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      02-07-2016, 10:37 PM   #1
pokeybritches
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High Boost M54 Build

I’m in the planning stages for my Z4 3.0i build. After debating an engine swap or going turbo, I’ve decided a ~15 psi supercharged M54 would best meet my build’s goals of reliability, 400+ whp, and remaining daily drivable. The next decision for me to make is whether to stick with my Vortech, or move to an ESS twin screw.

Bottom line, I’m considering a high compression build to max out my current Vortech supercharger at around 15-16 psi and 45k-50k impeller rpm, adding an intercooler, and spraying a water/meth mix for detonation control. Alternatively, I could move to a TS3 setup, but with custom low compression pistons and rods. Tuning has already been lined up and is not an issue.

My thought process is outlined here, and constructive criticism is welcome. I wanted to do my own research privately and keep quiet about it until the build was complete, but I’ve found some pretty interesting things that I haven’t seen anywhere else… at least not on a BMW-centric forum.

It’s common knowledge that a twin screw makes boost sooner. Centrifugal superchargers seem to make more peak power at similar boost levels. Both twin screw and centrifugal supercharger companies claim that their supercharger is the most efficient out there. But who is right? What does the “adiabatic efficiency” really mean? Now that I can change compression ratio, should I change it? And to what? How will gas mileage be affected?

I couldn’t find much real data out there other than forum myth, so I had to be creative.

http://www.mustangandfords.com/proje...ced-induction/

This is the only instance I’ve found of the same vehicle being equipped with various types of forced induction, run to 14-15 psi, and measured on the same dyno. Yes, it’s not an M54B30 and the compressors are different models than the ones I’m considering. But, I think generalizations can be made for the BEHAVIOR of each type of compressor in a high boost situation.

On the Mustang, boost builds with both compressors as rpm climbs. It starts higher with the twin screw, around 11.9 psi @ 3k rpm, and then climbs slowly to 14.5 psi. The centrifugal supercharger starts lower, around 2.2 psi @ 3k rpm, and climbs exponentially to 14.5 psi at 6600. For my build, I will likely set the rpm limiter to 6800 rpm. I extrapolated the twin screw running 14.5 psi to 6800, and the centrifugal increasing to 15.5 psi because I plan to run 15-16 psi. Since boost is a measure of restriction, it’s possible that the Mustang’s engine can’t flow enough air to support the supercharger, so it starts to choke up top, and boost pressure builds as flow requirements increase. A flow restriction would affect both superchargers, and without additional data showing supercharger behavior in other high boost applications, I am using this test as a generalization of supercharger behavior.



Predicting exact boost pressures wasn’t imperative to extract the I data I wanted, and everything would change anyway once I install aftermarket camshafts and have my cylinder head modified.

What the boost curves allowed me to do was plot performance on each supercharger’s compressor map. I used formulas to predict volumetric flow in cubic feet per minute (cfm).

The twin screw is plotted as a near-horizontal line with a slightly increasing slope, since the pressure ratio [(boost pressure + 14.7) / 14.7] is almost constant. The Vortech’s performance is plotted as a line with steep slope, which skirts the 70% efficiency line to the left of the supercharger’s “sweet spot”. For each data point, I found the compressor efficiency at 100 rpm increments. Yeah, it was time consuming to plot all 39 data points on each compressor map and transfer them to an Excel file :lol.



So, which is more efficient, the twin screw or centrifugal supercharger? Both. It depends on where you are on the compressor map. Below 4.2k rpm, the Lysholm is more efficient. Above 4.3k rpm, the Vortech is more efficient.

What does this mean?

Using some thermodynamics, you can predict the discharge temperature and horsepower lost due to compression.





For the discharge temperature, I used an inlet temperature of 70 deg F. As you can see, the Lysholm’s discharge temperature is a lot hotter, 224 deg F @ 3k rpm versus 111 deg F for the Vortech. Even though the twin screw has a better efficiency at 3k rpm, it produces more than 5 times as much boost, and the penalty is an additional 113 deg F and 5.1 hp loss over the Vortech.

These discharge temperatures are only accurate for the air leaving the supercharger. The air is then cooled with an intercooler/aftercooler and/or WMI. The ESS kit utilizes a liquid aftercooler. Water has four times the specific heat of air, meaning water can absorb four times the heat of air before it rises one degree. Coolant has a lower specific heat than water, so cooling capacity will vary depending on water/coolant mix. Besides the fact that air-to-air systems aren’t normally feasible for positive displacement superchargers, I think the air-to-water system is the right choice for the ESS kit, since its discharge requires a huge drop in temperature to avoid detonation. It also explains the reduction in compression ratio for the TS3 kit. However, I am concerned about heat soak during extended driving with the TS3 kit.

The Vortech may get away with an air-to-air intercooler, and water/meth for high discharge temps in the upper rpm band. Compression ratio can be higher due to the lower discharge temps and water/meth mix for detonation control.

Now to the big question - which one will be faster?

Obviously there are assumptions that must be made. I used a rule of thumb of 4% change in horsepower per point of compression. I calculated wheel horsepower in 100 rpm increments by taking a stock M54B30 dyno; multiplied it by the pressure ratio of each compressor; multiplied the result by % gained or lost due to CR; then subtracted the power it takes to spin the supercharger. I did not take into account power adders such as headers, cams, head work, and so on… nor did I take into account power lost due to heat of compression, since it is too dynamic.

With a 10.7 CR (102%) for the Vortech, and 9.0 CR (95%) for the Lysholm:



Below 5k rpm, the Lysholm makes an average of 30% more power than the Vortech, good for 50-66 more horsepower with my rough estimates. The Vortech finally moves ahead around 6.1k rpm, peaking about 11% higher at redline.

In a race with a Vortech versus the Lysholm, first gear would be a wash due to traction. Shifts at redline would land the cars at 4k rpm in 2nd; 4.5k in 3rd; 5k in 4th. Even in an ideal race, where both drivers shifted exactly at redline with no traction issues, the Lysholm car would be significantly faster until the top half of 4th gear.

Now if we raise the CR of the Vortech Z4 to 11.5:



The crossover point is lower (5800 rpm) and peak horsepower difference is 16% in favor of the Vortech. In this situation, I think the twin screw would still be faster through 2nd and 3rd gear. Torque wins races, and it’s tough to come back from a deficit.

It’s safe to conclude that with all other things being equal, a TS3 at 14-15 psi would be faster than a high compression Vortech running 15-16 psi and WMI until triple digit speeds. However, it would also consume 6 hp at highway speeds (and have a lower CR), while the raised compression of the Vortech Z4 would offset the power consumed by the supercharger (and the car would possibly get better gas mileage than stock). Additionally, the Vortech Z4 would require less cooling capacity, especially during normal driving.

If I had an ESS twin screw, I wouldn’t switch to a Vortech and build the motor to get the added top end and gas mileage. For me, it’s a matter of cost versus benefit. I already own a Vortech; I’ve got a nice trunk-mounted water/meth setup; I have a 3.46 Quaife LSD that might be overwhelmed by the extra low end of the twin screw; and I daily drive the car and would appreciate the added gas mileage. However… custom crank/accessory pulleys, injectors, intercooler, brackets, piping, etc. aren’t cheap, and there is a salvage value in selling my VF kit.

Both setups have pros and cons, some of these results surprised me, so I wanted to share

------------------------------------------

Update 2/13/2016

Before I start swapping pistons and rods, I wanted to see if there would be any benefit to using a smaller pulley on a centrifugal setup, and adding a wastegate between the supercharger discharge and throttle body to control boost levels. The engineer in me doesn’t like the idea of it because it’s an inefficient way of doing things. Regardless, I considered doing it to get max boost from ~6k rpm to redline, with the tradeoff of higher discharge temperatures and more power consumed by the supercharger.

In other words, I’d get more low end and midrange, at the expense of peak power and efficiency.

My tuner says he can tune around it. I think part throttle would be hard to tune around, because you have two competing discharges. The intake wastegate and bypass valve are both dumping boost (unless the bypass opening dropped boost pressure enough that the wastegate closed). The ECU is using the info given to it by the MAF sensor for fuel calculations, so the car would need to be tuned to estimate how much air is being dumped through the wastegate, and how much is being dumped through the bypass. At full throttle or off throttle, things are better defined.

For the estimations, I used the same boost curve that I used previously for the 14.5 psig twin screw and 15.5 psig centrifugal (henceforth, I’ll drop the “g” from psig). I multiplied each 100 rpm increment by a fraction related to the new peak boost (so in this case, I multiplied each data point by 8.5/14.5 for the twin screw and [8.5, 12, 15, 18]/15.5 for the centrifugal). I did not go back and recalculate the compressor efficiency at every single data point. I did glance at the compressor maps, and the twin screw operates just above the “sweet spot” at 14.5 psi, and just below it at 8.5 psi; the centrifugal starts out in an area not covered on the compressor map (so data would need to be extrapolated), then moves towards the “sweet spot” of 73% efficiency. For the purposes of what I’m showing, a 5% change in compressor efficiency is irrelevant, since it only equates to a few degrees of discharge temperature and tenths of a horsepower.

The 15 psi and 18 psi pulleys would probably require a whole new pulley set to avoid belt slip, since the supercharger pulley would be too small with the standard crankshaft pulley, and the power required to turn it is higher. A Vortech SCi trim compressor would need to be spun to about 53k rpm (2.36” pulley using the stock 5.11” crank pulley… and that won’t happen without serious belt slip :lol).



First is boost pressure. Peak boost is reach at:

6800 rpm, 8.5 psi pulley
5900 rpm, 12 psi pulley
5300 rpm, 15 psi pulley
4900 rpm, 18 psi pulley

Even with maxing out the centrifugal supercharger, the twin screw has a huge advantage at low rpm.





Next we have the volume flow rate (cfm) of air dumped by the wastegate, and air passing through the throttle body. Ideally, only the air that is passing through the throttle body would have passed through the intercooler. The air that is not going to be used by the engine would be dumped before it passed through an intercooler. All things being equal, a lower volumetric flow rate means cooler air will exit the intercooler and into the engine, because there is less hot air to cool.



If the boost pressure graph shows the advantages of smaller pulleys, the discharge temperature graph is one of the areas where the downsides appear. I used an ambient temperature of 70 deg F, like with my previous high boost analysis (by the way, “standard day” is actually 59 deg F).

Obviously, some sort of aftercooling is necessary. Max discharge temps for each setup:

174 deg F, 8.5 psi
209 deg F, 12 psi
236 deg F, 15 psi
261 deg F, 18 psi
196 deg F, twin screw

When I lived in the California desert, ambient temperatures regularly got up to 110 deg F.



222 deg F, 8.5 psi
259 deg F, 12 psi
289 deg F, 15 psi
316 deg F, 18 psi
246 deg F, twin screw

I think we can agree that a well-developed means of cooling is necessary.

A smaller pulley is a compromise. It provides the midrange benefits of a high boost setup without the stress of high boost pressures, which is great for a stock engine. Because the volumetric flow rate of air entering the intercooler is lower, less cooling capacity is required, even if discharge temperatures are the same.

Then again, you deal with many of the downsides of a high boost setup, without enjoying the significant power advantages that high boost provides. The power required to spin the supercharger is the same whether you use the boost or dump it, so there’s a lot of waste:



Using the formulas I used previously, we can estimate wheel horsepower. Again, this doesn’t take into account power adders such as headers, FI-spec camshafts, or head work. It also doesn’t include losses due to intercoolers, heat of the intake air, or conservative tuning.



IMHO, a 12 psi pulley, with an 8.5 psi wastegate dump, appears to be the best compromise for a centrifugal setup. Max boost comes in before 6k rpm. Discharge temperature and horsepower consumed by the supercharger are mildly greater than a twin screw at high rpm, and it will run cooler and be more economical everywhere else. However, for maximum average horsepower at identical peak boost levels, you can’t beat a twin screw.

Overall average horsepower, 3k-6.8k rpm:
226 whp, 8.5 psi pulley
240 whp, 12 psi pulley
247 whp, 15 psi pulley
250 whp, 18 psi pulley
264 whp, 8.5 psi twin screw

Average horsepower, 4k-5.5k rpm:
216 whp, 8.5 psi pulley
233 whp, 12 psi pulley
247 whp, 15 psi pulley
255 whp, 18 psi pulley
263 whp, 8.5 psi twin screw

Average horsepower, >5.5k rpm:
281 whp, 8.5 psi pulley
297 whp, 12 psi pulley
295 whp, 15 psi pulley
291 whp, 18 psi pulley
298 whp, 8.5 psi twin screw

If you’ve got a centrifugal supercharger, it may be worth pursuing this mod, along with aggressive gearing to minimize your time spent outside of boost.
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      02-08-2016, 12:20 AM   #2
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I'd like to first identify that there is some irony in the fact that the most upfront/informative place of knowledge was a "Mustang and Ford" domain.

Regardless, there's a ton of knowledge here and it you've taken everything into consideration. I think for the vast majority of us we consider the most basic principles of the first law of thermodynamics (heat passing through a system creates work/energy, more of this = more power [hence our knowledge of your description of "power adders") and everything past that is a little bit of sorcery, but this was easy to read and straight forward. I learned a lot here and I am very appreciative of that, and I hope others walk away with the same knowledge.

What I'm most curious about is the actual heart of the system itself, because that becomes the next question I'd think. A solution to it that question would be purely curiosity at this point and would require a ton of data points. In this case you have found the most efficient system given the system is an M54B30. Would it be fair to apply this same theory to other engine models? Different capacities, cylinders, even a rotary?

In our case for these motors and these cars is this the most applicable power (as in usable or performance power and not just a number for a Dyno)? Would you say that a turbo setup would not out perform there is an option for that as well (I would assume that this would be true given a turbo does not start producing boost until later stages and would be too far behind, as you said usable torque wins out every time).

Just some curious questions as I was reading. I'll make sure to re-read with greater attention soon. I really enjoyed this analysis.
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      02-08-2016, 07:25 AM   #3
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      02-08-2016, 10:42 AM   #4
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Personally I'd go for E85 if you're not planning on opening the engine, if that's not an option due to availability of E85 I'd go with water and meth injection. Aiming for 400 WHP without opening the engine I'd stick to the centrifugal instead of a twin screw to get more linear boost instead of boost lower in the rev range. Mostly because it puts less stress on the engine if the boost comes higher up in the rev range, I'm not so sure the rods will remain in one piece with 400 WHP and full boost at low revs.

Other then that the M54 is a really strong engine when it comes to boost. With new pistons, rods, copper ring gasket and ARP bolts it will be a tank of an engine.
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      02-08-2016, 10:55 AM   #5
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Why would a certain amount of boost on lower revs put more stress on the engine than with high revs?
I think it's just the other way around.
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      02-08-2016, 11:33 AM   #6
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It's the combination of high boost and max torque that kills the rods, in the case of a twin screw that means that max boost and torque will be early in the rev range. Whereas a centrifugal max boost comes late and won't happen at the same time as max torque. It's pretty common here in Sweden to build stock M60's with a single turbo instead of twin turbo because the stock rods will snap a lot easier with twin turbos because of the higher amount of torque and boost earlier in the rev range.

This is something I've read in numerous build thread on Swedish forums, I have no own experience of this.

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      02-08-2016, 11:58 AM   #7
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Yes but that single vs double turbo is probably due to that the one gives way more torque in general than the other. Obviously 1000Nm at 3krpm is a bigger strain than 500Nm at 6krpm

But if an engine can stand for example 500Nm of torque at 6k rpm, it can certainly stand 500Nm at 3k rpm.
On high revs everything is more at risk. There is way more heat, so the cooling system is more under stress, heat also weakens parts. Ignition timing is earlier, so the blow the piston gets is less precise etc etc.
It's a logical step to go and turbocharge engines to get more power instead of increasing revs and displacement.
That turbocharged engine is usually lighter in build, yet it gives more torque... at lower rpms.
So I don't agree with your initial statement. I see no reason why a certain amount of boost (say 15psi) would be more harmful at 2k or 3k rpm than at 6k rpm. I think that an engine can stand more boost and torque at lower rpm's than at higher rpm's. How much more I don't know, there is probably not a set value for that.
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      02-08-2016, 12:27 PM   #8
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It's a combination of torque and boost. Peak boost at high rpms means less torque. Peak boost in the mid range means it will happen at the same time as peak torque. At what boost and torque will the rods break? How long is a piece of string?

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      02-08-2016, 12:59 PM   #9
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Boost is pretty linear to torque. And the torque curve is pretty linear on the m54. Only after 5.5k or 6k it noticeably starts falling off a bit.
Torque on 2,5k or on 5k is pretty much the same imho. Certainly not that of a difference to not choose for a specific type of supercharger.
A few Nm are not going to give the difference in snapping driveshafts or not. Certainly not if considering that to my opinion an engine can handle more torque in low and midrange than in the high range. Unless you spec a supercharger that only gives boost after 6k rpm. But's what's the use in that?
ESS specs their twinscrews up to 15psi on the m54 without much trouble on the stock lower block (only low compression pistons. driveshaft and rods stay the same). I don't see potential problems.
The problems I do see are maybe on headbolts and gasket, but that's also very revdependant, as cooling/heat also plays a role in that. Those are usually blown at higher rpms.
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      02-08-2016, 01:13 PM   #10
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I never said it was a big difference, but there is a difference. And if he's going to run stock rods and 400 WHP he's walking a very fine line and will need all the help he can get to increase reliability. Even if that means sticking with the centrifugal instead of a twin screw. Unless he's planning on spending most of the time at the rev limiter it's not the rpm's that will kill the rods first. If rev's are the cause of rod failure it's more than likely it's because of over revving, not hitting red line momentarily.
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      02-08-2016, 01:53 PM   #11
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Quote:
Originally Posted by Arsonism View Post
I'd like to first identify that there is some irony in the fact that the most upfront/informative place of knowledge was a "Mustang and Ford" domain.

Regardless, there's a ton of knowledge here and it you've taken everything into consideration. I think for the vast majority of us we consider the most basic principles of the first law of thermodynamics (heat passing through a system creates work/energy, more of this = more power [hence our knowledge of your description of "power adders") and everything past that is a little bit of sorcery, but this was easy to read and straight forward. I learned a lot here and I am very appreciative of that, and I hope others walk away with the same knowledge.

What I'm most curious about is the actual heart of the system itself, because that becomes the next question I'd think. A solution to it that question would be purely curiosity at this point and would require a ton of data points. In this case you have found the most efficient system given the system is an M54B30. Would it be fair to apply this same theory to other engine models? Different capacities, cylinders, even a rotary?

In our case for these motors and these cars is this the most applicable power (as in usable or performance power and not just a number for a Dyno)? Would you say that a turbo setup would not out perform there is an option for that as well (I would assume that this would be true given a turbo does not start producing boost until later stages and would be too far behind, as you said usable torque wins out every time).

Just some curious questions as I was reading. I'll make sure to re-read with greater attention soon. I really enjoyed this analysis.
Haha, yeah, I figured I'd get some pushback for using a Ford magazine as a source. Because FI modifications to Cobras are more popular than FI mods to BMW's (as in, more $$ is spent), there's more information out there on the Cobra. Without specific data for the M54B30 under high boost, I had to make some assumptions on supercharger behavior, and go from there.

I spent a lot of time weighing an engine swap or turbo before ultimately deciding on the supercharger. I have another write-up which goes through the details, but I'm saving it for when the build is complete. The basics are:

Vortech Supercharged - built engine (pistons, rods, head work, head studs), cams, add cooling, ensure proper fueling, raise boost, tune.
ESS Supercharged - ESS kit, built engine (pistons, rods, head work, head studs), cams, ensure proper fueling, raise boost, tune.

****

Turbo - Bottom line is I don't want something I have to constantly fiddle with to get right, and I'm not confident that the rest of the car can handle the torque. The supercharger is a simpler setup with less risk involved.

I can't see myself with a log-style manifold, so I'd want a custom manifold built. I'd also want to use a twin scroll turbo. Piping for a twin scroll setup and intercooler would be long and complicated, and there is potential for leaks/cracking. The MAF would either have to be in front of everything (making boost leaks a nightmare), or I'd have to convert to a blow through MAF (and the car would need to be tuned for a different MAF sensor, likely Porsche, since the stock one would be susceptible to oil contamination post-turbo). O2 sensors would need to be converted to a single bank, affecting the general smoothness and fueling precision of the engine. The engine would run hotter and an oil cooler circuit would be needed. I expect tuning would take a whole lot longer, and no tuner works for free.

A turbo has more power potential. However, I don't know how much power the block can hold without ripping out threads, lifting the head, and destroying my expensive built engine. Assuming it could safely handle the power, the clutch would need to handle the torque. I'd have to ditch my Quaife LSD and upgrade the diff. The entire driveline would need to be modified to handle the torque. Larger fuel injectors decrease precision and feel.

Then there's the cost. I've already got a full Supersprint exhaust, from ceramic coated headers all the way to the race muffler. Acquiring all of these parts wasn't easy or cheap, so I'm tempted to "love the one I'm with" and take advantage of it. It's tough to sell Z4 parts, and I don't want an exhaust system and supercharger kit sitting in my garage for a year while I bump it up in the classified section, only to ship it off and find out a part was missing or be bombarded with questions about the install. I'd rather take the risk-averse path and avoid headaches, enjoy the better feel of a supercharged car, and not worry if my drivetrain is going to grenade from all the power I'm pumping through it.

****

Swap - a completely different beast. I don't want to spend years of my life tracing wiring and digging up part numbers from RealOEM to make something work, and paying a shop to do it would be insane. I want an OBD2 ready car that functions just like stock, except with more power. Anything newer than the M54B30-era is out of the question due to the electronics. The S62 won't fit because of the oil pan, and a turbo M/S 50/52 would have all of the issues of a turbo build with the added complexity of an engine swap. An S54 would work, but I have two S54 Z4's already. I haven't seen a TS3 or high CR, high boost Vortech Z4.

****

As far as applying this same theory to other engine models with different capacities, cylinders, or even a rotary... some basic principles are relevant. You would need data regarding boost vs rpm, or you will have to make an assumption as to boost vs rpm like I did. From there, you can estimate the volumetric flow rate. This online calculator can help:

http://www.mk5cortinaestate.co.uk/calculator3.php

Then, you can plot the points on the compressor map. Typically pressure ratio is the vertical axis, and volumetric flow is the horizontal axis. Normally a twin screw will have a near-constant pressure ratio, so it's almost a horizontal line. The Vortech centrifugal superchargers plot as a steep line moving up and to the right on the map. ASA may be different.

Once you plot, you can estimate the compressor's efficiency at each point. Plug that info into an Excel file, along with some thermodynamic formulas, and you can see any of the things I posted.
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      02-08-2016, 02:10 PM   #12
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Quote:
Originally Posted by Westersund View Post
Personally I'd go for E85 if you're not planning on opening the engine, if that's not an option due to availability of E85 I'd go with water and meth injection. Aiming for 400 WHP without opening the engine I'd stick to the centrifugal instead of a twin screw to get more linear boost instead of boost lower in the rev range. Mostly because it puts less stress on the engine if the boost comes higher up in the rev range, I'm not so sure the rods will remain in one piece with 400 WHP and full boost at low revs.

Other then that the M54 is a really strong engine when it comes to boost. With new pistons, rods, copper ring gasket and ARP bolts it will be a tank of an engine.
This will be a fully built engine. I'm not comfortable pushing much beyond 450 whp though, even with a built engine. Much of the drivetrain cannot handle it, as it's been proven on E46 cars. My goal isn't max power with a limitless budget. I'm looking to either upgrade what I have plus the built engine, or switch to a custom TS3-like setup.

Old thinking was that CR had to be lowered when running high boost, because inlet air temperature can be regulated (lowered) via an intercooler. Once it passes into the cylinder, you've got what you've got, and CR and fuel quality will dictate whether you will get detonation. New thinking is that high CR will work without detonation, but it's risky and up to the tuner. When asked about CR, my tuner said 11.5 for the Vortech. While he is very experienced and knowledgeable, I wanted to see for myself what this meant for the air coming into the engine (or intercooler). I was curious as to whether a Vortech running high boost could handle a higher CR than stock, and how inlet temperatures differed from a twin screw at the same peak boost.

The other questions I wanted answered were, just how much more power would a high boost twin screw make down low versus a centrifugal kit, and would a high compression centrifugal kit ultimately provide a faster car when going balls to the wall? It appears the answer to the first is question is "30-40%", and the second is "no".

The advantages and disadvantages of the various types of forced induction don't shine through very much when you are only running 6-8 psi. Yeah, a twin screw or turbo make power sooner, but that's about it. A properly sized turbo doesn't have much lag at 6-8 psi. The twin screw doesn't heat up the inlet air to the point of needing a lower compression ratio. And the engine naturally produces most of its power, rather than artificially with forced induction.

Once you crank up the boost, the true characteristics of each type of forced induction shine through.
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      02-08-2016, 03:00 PM   #13
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Quote:
Originally Posted by Westersund View Post
I never said it was a big difference, but there is a difference. And if he's going to run stock rods and 400 WHP he's walking a very fine line and will need all the help he can get to increase reliability. Even if that means sticking with the centrifugal instead of a twin screw. Unless he's planning on spending most of the time at the rev limiter it's not the rpm's that will kill the rods first. If rev's are the cause of rod failure it's more than likely it's because of over revving, not hitting red line momentarily.

Well, then I still don't exactly understand what your statement is?

Do you think an engine can handle more torque at low rpms or can it handle more torque at high rpms? What is it?

As for this build I think the mapping or better said the ecu will have the biggest problem.
The ms45 doesnt lend itself very well for high boost. (ess dropped the ts3 offer on the ms45 for that; problems with the ping algorithems that havent been cracked&mapped yet, or so they say. None of the other tuners have a high psi possibility for the ms45 either.)
The fuel injection might be another problem
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      02-08-2016, 04:08 PM   #14
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Originally Posted by GuidoK View Post
Well, then I still don't exactly understand what your statement is?

Do you think an engine can handle more torque at low rpms or can it handle more torque at high rpms? What is it?
I don't know how much more clearer I can say this without repeating myself. If you're sticking with stock internals you want the boost to come later in the rev range so max boost and max torque won't align. Making it less likely to break the rods.
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      02-08-2016, 04:13 PM   #15
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Quote:
Originally Posted by pokeybritches View Post
Old thinking was that CR had to be lowered when running high boost, because inlet air temperature can be regulated (lowered) via an intercooler. Once it passes into the cylinder, you've got what you've got, and CR and fuel quality will dictate whether you will get detonation. New thinking is that high CR will work without detonation, but it's risky and up to the tuner. When asked about CR, my tuner said 11.5 for the Vortech. While he is very experienced and knowledgeable, I wanted to see for myself what this meant for the air coming into the engine (or intercooler). I was curious as to whether a Vortech running high boost could handle a higher CR than stock, and how inlet temperatures differed from a twin screw at the same peak boost.
Running high comp and high boost on pump gas will be very risky. Increasing the comp while adding boost makes no sense, rather leave the comp were it is stock and add more boost. The only way you would get away with it is running E85. I don't think pump gas and water/meth will be enough.

Will be interesting to see how it goes nontheless. Good luck!
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      02-08-2016, 04:38 PM   #16
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Quote:
Originally Posted by GuidoK View Post
As for this build I think the mapping or better said the ecu will have the biggest problem.
The ms45 doesnt lend itself very well for high boost. (ess dropped the ts3 offer on the ms45 for that; problems with the ping algorithems that havent been cracked&mapped yet, or so they say. None of the other tuners have a high psi possibility for the ms45 either.)
The fuel injection might be another problem
I had brought this up previously with my tuner, and he said the reason no one offers the kits is like you said, the ECU hasn't been cracked and mapped. He mapped it himself when he tuned my car. He had assumed the Z4 ECU had already been mapped, and it was time consuming and a huge pain when everything had to be done from scratch. Fortunately he only charged me the standard price. He assured me that it would not be hard to raise the boost now that the base file has been established. He also mentioned the hardware setup on my 2003 car was "only that year, and only that car [Z4]". So, there may even be differences between the Z4's. Or, he could have been messing with me to see how much of it ends up on the forums I do know the MS45.0 on the Z4 is not the same as the MS45.x on the E46.

That being said, I think there is some risk that I could run into tuning issues. Such is the nature of doing a build that no one has done before, and relying on someone else to tell you what they are capable of doing. A high compression Vortech build would at least make more power than stock+Vortech, whereas a low compression twin screw would make less power than stock+ESS. Then again, I could sell a low compression built motor to a TS3-hunting ESS E46...

As far as making power at high or low rpm, detonation is less likely when time at TDC ("dwell time") is minimized. Whether this offsets the risks you mentioned that are associated with high rpm, I don't know. There are so many moving parts, and any one failure can lead to destruction.

I'm hoping I don't need to upgrade the fuel pump, but I'm budgeting for it. If I'm lucky it will be the same as a Z4M (I'd have to check RealOEM).
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      02-08-2016, 04:51 PM   #17
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Quote:
Originally Posted by Westersund View Post
Running high comp and high boost on pump gas will be very risky. Increasing the comp while adding boost makes no sense, rather leave the comp were it is stock and add more boost.
Why do you think it makes no sense? The supercharger will be very nearly maxed out at 15-16 psi. Raising compression increases both efficiency and power. If you increase the base engine's power, you don't have to run as much boost to make good power. Or, you can run the same boost and make even more power. Lowering compression would be a last resort to ensure a margin of safety. Based on the supercharger discharge temperatures, this would be necessary with the TS3 kit. I don't know that the Vortech necessitates lower compression.

I will have both an intercooler and water/meth injection to control temperatures. My car is currently tuned for 8-9 psi, and the trunk-mounted water/meth kicks in at 4 psi.

One other point - water/meth is more feasible on a centrifugally supercharged car. I've used maybe 1/2 of a tank in a year. With a twin screw car, I would have to base it on something other than boost pressure (like rpm), unless I wanted to fill the tank up every few weeks. There's also the issue of finding a way to inject it post-supercharger for maximum effect.
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      02-08-2016, 06:40 PM   #18
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Quote:
Originally Posted by Westersund View Post
I don't know how much more clearer I can say this without repeating myself. If you're sticking with stock internals you want the boost to come later in the rev range so max boost and max torque won't align. Making it less likely to break the rods.
So if I post this picture of a typical m54 torque curve:



Where would you suggest the supercharger should start making boost?

Between 2,5k revs and 5.5k revs there is only 20ft/lbs variation in torque....
So only boost above 5.5k revs? what's the point in that?

Or lets start boost at 6k, because then we can make 40ft/lbs more torque...
Your advice has theoretical logic but no practical value.

I think most people will prefer a wider torque range. Prefer 40ft/lbs of overall less torque but all over the rev range instead of a boost at 6k revs to the revlimiter at 6.5k
In fact I even think that the m54 even can hold 40ft/lbs of extra torque on 3.5k revs than over the maximum torque value (before things start to break down) at 6k revs if you understand what I mean here...
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      02-08-2016, 06:52 PM   #19
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Quote:
Originally Posted by pokeybritches View Post
I had brought this up previously with my tuner, and he said the reason no one offers the kits is like you said, the ECU hasn't been cracked and mapped.
The ecu has been cracked and mapped, but not for all mappings.
Talk to daniel_f on e46fanatics. He did some mapping for his computerprogram (but on the ms43), and I said I was amaized to see that there are over 50 or so mappings in his program for various functions. He reckoned that that was maybe 10 percent of ALL the mappings

Ask your tuner if he can write a new ping sensor algorithm.
No one probably can. (its probably not a single mapping but a whole bunch)

That's why all high power builds go with aftermarket ecu's. There are too many hidden mappings that go out of their recorded boundries. With an aftermarket ecu everything is documented and there are no hidden surprises (at least that's how it's supposed to be)
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      02-09-2016, 10:23 AM   #20
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Quote:
Originally Posted by pokeybritches View Post
Why do you think it makes no sense? The supercharger will be very nearly maxed out at 15-16 psi. Raising compression increases both efficiency and power. If you increase the base engine's power, you don't have to run as much boost to make good power. Or, you can run the same boost and make even more power. Lowering compression would be a last resort to ensure a margin of safety. Based on the supercharger discharge temperatures, this would be necessary with the TS3 kit. I don't know that the Vortech necessitates lower compression.

I will have both an intercooler and water/meth injection to control temperatures. My car is currently tuned for 8-9 psi, and the trunk-mounted water/meth kicks in at 4 psi.

One other point - water/meth is more feasible on a centrifugally supercharged car. I've used maybe 1/2 of a tank in a year. With a twin screw car, I would have to base it on something other than boost pressure (like rpm), unless I wanted to fill the tank up every few weeks. There's also the issue of finding a way to inject it post-supercharger for maximum effect.
It makes no sense if you want a reliable daily driven car. High compression, boost and pump gas don't mix that well. Intercooler is a must, but I'm not so sure water/meth injection will be enough to prevent knocking. On stock compression maybe, 11.5:1 compression? You're playing with fire. (Pun intended)

If you're going with forged internals just increase the boost instead of the compression. Forged internals, cooper ring gasket and helicoil the block for the ARP head studs and the M54 will hold at least 30 psi of boost.
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      02-09-2016, 10:42 AM   #21
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Quote:
Originally Posted by GuidoK View Post
Where would you suggest the supercharger should start making boost?

Between 2,5k revs and 5.5k revs there is only 20ft/lbs variation in torque....
So only boost above 5.5k revs? what's the point in that?

Or lets start boost at 6k, because then we can make 40ft/lbs more torque...
Your advice has theoretical logic but no practical value.

I think most people will prefer a wider torque range. Prefer 40ft/lbs of overall less torque but all over the rev range instead of a boost at 6k revs to the revlimiter at 6.5k
In fact I even think that the m54 even can hold 40ft/lbs of extra torque on 3.5k revs than over the maximum torque value (before things start to break down) at 6k revs if you understand what I mean here...
I know that the M54 has a very flat torque curve due to the VANOS, I'm not arguing with you there.

I don't know if you've misunderstood me. I've been talking about an engine with stock internals with 400 WHP from the get go. That's why I think the centrifugal is better because it will have a more linear boost curve relative to the RPM, which with stock internals is less abusive than a twin screw that reaches max boost a lot earlier. Twin screw = almost instantaneous boost. Centrifugal = Linear build up. I don't know where you got the boost build up from 6K RPM from, I've never said anything of the sort.

What peoples preferences are is irrelevant, I'm strictly talking about reliability on a daily driven car.
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      02-09-2016, 01:38 PM   #22
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Quote:
Originally Posted by Westersund
High compression, boost and pump gas don't mix that well.
My point is that these are dated generalizations that are spread over forums with little factual basis. Fuel injection has become precise and dynamic, and a centrifugal supercharger produces lower discharge temperatures than a twin screw at the same boost levels (as I've shown with thermodynamics). No offense is intended of course, but I'm looking more to answer "why" I should go with a specific CR other than that's what others have done (which is not always the best way to do things).

"Why" could be answered with, "What's the maximum safe cylinder temperature in which to inject 93 octane fuel?" I can calculate supercharger discharge temps, make an estimate (with buffer) for aftercooler efficiency, and then estimate cylinder temps due to CR. Obviously there will need to be a margin of safety due to cylinder hot spots, extended use, and so on.
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