VF570 installed

[ZStig]

not sure what I'm looking at, car lost power being catless?

[pandusr]

Originally Posted by ZStig

not sure what I'm looking at, car lost power being catless?

Yes !!

range (4000-6000) = -30/25 hp
range (6000-8000)= + 10 hp

[ZStig]

very strange. Maybe its because your supersprint X-pipe + muffler is too open...

I have OEM catless headers, and was planning on removing the section 1 cats, keeping the rest of the exhaust stock, now I'm wondering if thats a bad idea

[ajw45]

It happens. On my old e28 m5 I dynoed with and w/o cats back to back and lost a huge chunk of torque below 3500 rpm but gained a little everywhere above 4k. So peak numbers were better w/o cats but area under the curve was about the same....

[Rated M Roadster]

Even if you lose a little power, you get flames

Some day I'll make it back to the dyno to check this out...

[pandusr]

Originally Posted by ZStig

very strange. Maybe its because your supersprint X-pipe + muffler is too open...

I have OEM catless headers, and was planning on removing the section 1 cats, keeping the rest of the exhaust stock, now I'm wondering if thats a bad idea

Real. My exhaust is wide-open. My car is europe and has no cat in collectors.

Odd project. Usually you change the headers and you keep the cat section 1. The main difference between the USA and Europe models is the headers CSL (catless).

[pandusr]

Originally Posted by Rated M Roadster

Even if you lose a little power, you get flames

Some day I'll make it back to the dyno to check this out...

real.

mine looks like a bike with differential 4:10.

the first two gears do not exist.

[Beedub]

Originally Posted by pandusr

real.

mine looks like a bike with differential 4:10.

the first two gears do not exist.

hmmmm i really dont see why this car would loose power being catless... Being supercharger id expect gains across the board which is what ive seen on many a supercharged m3......

[pandusr]

Originally Posted by Beedub

hmmmm i really dont see why this car would loose power being catless... Being supercharger id expect gains across the board which is what ive seen on many a supercharged m3......

Sorry for my English, I try to explain.

If empty too exhaust, without changing the valve timing, low speed rotation, throw gasoline into the drain.

The change is very complex. Pressure waves, resonance, pitch and length, etc.

If does not change DME, expect losses HP to low speed rotation.

[dre99gsx]

Removing restrictions (cats, mufflers, etc) will always be beneficial since you're reducing backpressure, but the flip side is that you must also pay attention to the exhaust diameter, routing, merge collector, etc. In other words, the OEM exhaust was engineered to flow properly with all the components in place (mufflers, cats, etc).

It is so much easier with turbos since the turbo more than makes up for lack of torque, where no exhaust equals the best exhaust. With a supercharger running low boost at low RPM, you're still at the mercy of the exhaust system to optimize exhaust velocity and scavenging.

I've always thought that designing an exhaust for a SUPERCHARGED vehicle is extremely demanding. Since boost increases linearly, ideally, the exhaust should also dynamically change to support higher velocity and pressures. You're damned one way or another.

Simply removing restrictions can affect the original engineered intent of the Z4M exhaust. The proper way is to install an engineered and designed exhaust system to support:

- Increased velocity up top from the supercharger
- Maintain low RPM velocity for maintaining and aiding low end torque

It would be nice to see dynos of various exhaust systems, back to back, with a supercharger on the Z4M. Until then, mixing and matching will be a toss up.

AND: If you are just roll-racing on the highway, which usually starts in 2nd gear @ 4500rpm (in some cases), you'll never get below 4500 anyway. At the circuit is a different ball game of course...

RPM Gear Ratio
shift point -> 1st 8000 4.35
2nd 4597.701149 2.5
3rd 5344 1.67
4th 5892.215569 1.23
5th 6504.065041 1
6th 6800 0.85
Final Drive 3.62

[ajw45]

Ah, found an old dyno of my e28 with and without cats. We simply swapped out the catted oem mid-section (red) with an straight pipe center section (blue). I'm sure the S54 has it's own unique issue but this is a good example of how removing the cats can lower output in a certain rpm range.

[seank]

Originally Posted by ajw45

It happens. On my old e28 m5 I dynoed with and w/o cats back to back and lost a huge chunk of torque below 3500 rpm but gained a little everywhere above 4k. So peak numbers were better w/o cats but area under the curve was about the same....

WHS.


my s14 race motor had he same issue of less power, until the fueling was adjusted. The open exhaust made it run slightly lean.

[Platinum Child]

favorite roadster on here, need my car to shoot flames

[Rated M Roadster]

Originally Posted by Platinum Child

favorite roadster on here, need my car to shoot flames

Thanks!


This just came in the mail; getting installed tonight.


TiAl BOV VF570 by M detaR, on Flickr

[ZStig]

oooh! take a before-after sound clip

[GuidoK]

How does the kit (and bov) work?
Is the bov opened by vacuum (vacuum from behind the throttle body)? I mean is it constructed in the kit just like a normal bov?
These systems for the s54 (this one and the ESS kits) are mafless right?

And is there some sort of wastegate system (maybe to get a wider pressure range?) or is the buildup of pressure just regulated by the engine rpm?

[Beedub]

lovely floor rated i love natural wood boards..... really nice colour..... BOV is nice but the floor is awesome....

[Rated M Roadster]

Originally Posted by ZStig

oooh! take a before-after sound clip

I would take a video, but I'm removing it tonight. The sound is not to my liking; so I'm going back to the stock BPV.

Originally Posted by GuidoK

...
Is the bov opened by vacuum (vacuum from behind the throttle body)? I mean is it constructed in the kit just like a normal bov?
These systems for the s54 (this one and the ESS kits) are mafless right?

...or is the buildup of pressure just regulated by the engine rpm?

Yes, opens by vacuum; bolted to the bottom of the manifold. The VF kit is MAFless, not sure about the ESS kit. Pressure is dependent on the engine rpm (assuming your talking about boost).

Originally Posted by Beedub

lovely floor rated i love natural wood boards..... really nice colour..... BOV is nice but the floor is awesome....

Why thank you!

[GuidoK]

What is the difference in sound? Is the tial too loud? (or too quiet?).
Was there any difference in throttle response?

[Rated M Roadster]

Originally Posted by GuidoK

What is the difference in sound? Is the tial too loud? (or too quiet?).
Was there any difference in throttle response?

The TiAL is too loud for me. The stock BPV makes no noise at all. Didn't notice a difference in throttle response...

[ZStig]

Too loud eh? Sounds like its for me

[Rated M Roadster]

Originally Posted by ZStig

Too loud eh? Sounds like its for me

I'll sell it for $30 less than what I paid... Paid $290 with greddy adapter plus black and green springs.