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      10-17-2013, 06:16 PM   #1
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3.07 --> 3.64 + Headers



Update 21 OCT 2013: The car pulled 285 whp and 225 ft-lbs wheel torque on the dyno.




3.07 --> 3.64
Pros – 18.6% more torque to the ground; wider range of gear choices

Cons – 18.6% increased highway rpm with lower gas mileage

2500 rpm at 60 mph
2900 rpm at 70 mph
3300 rpm at 80 mph

The car is a whole lot more fun around town with the 3.64 final drive. Without a doubt it’s the best bang for the buck “power” mod (we all know it doesn’t really add horsepower). A stock car will feel like it’s gained 40 horsepower, and forced induction cars will feel like they have gained around 60 horsepower… plus all that extra torque throughout the rev range.

A 3.64 pairs extremely well with a low boost centrifugal supercharger kit. For NA cars, I would recommend a raised redline, either through the Shark Injector or other tuning software. After driving the 3.64 around for a few hundred miles, I think I could even go as high as a 3.91 on a NA car. For a car with a centrifugal supercharger, a 3.64 is about right if highway cruising isn’t the norm.

Highway rpm is similar to a 2.5i manual. Regular short-distance runs on the highway are a non-issue. If the car spends most of its life on the highway, this mod is on the aggressive side. If you have a 3.07 and want to know how it feels, try driving around in 5th on the highway.

I wouldn’t say that I shift more often. I think that only applies if you’re one of those people that feels the need to row through every gear before settling. I skip gears almost every time I shift. With the 3.64, it’s much easier to do so. The car is happier going from say 3rd to 5th than it was with the 3.07.

I now have a wider range of gear choices. With the 3.07, there were hills I had to navigate in 2nd gear. Now I can be in 2nd or 3rd. Similarly, when I would have previously been forced to choose between downshifting into 2nd at 50 mph (wringing the car out more than I would have liked), I can drop to 3rd and have plenty of torque to get the job done.

I like the diff more than I thought I would. I bought it off of a 17k mile 2.5i auto, and I couldn’t be happier.

Ceramic Coated Headers
Pros – finally makes the M54 sound mean, flames, spitting, popping, horsepower increase, cooler operating temps, better fuel economy, easier on the engine

Cons – eliminates the only set of cats (emissions), fitment, resonance, rasp, spitting, popping, drone, gas fumes

It’s harder for me to recommend this mod than the 3.64 final drive, because there’s more baggage that comes with it. Where a 3.64 has no other side effects than higher rpm on the highway, headers are a mixed bag. Personally, I’m thrilled with them. You may not be, depending on what you want with your car.

I decided to do headers as soon as I saw a picture of the stock exhaust manifold. Long story short, the stock exhaust is terrible. I couldn’t believe how much it sucked. Knowing how much better the Supersprint headers were, and seeing the ones I bought sit around the house for almost two years, kept the engineer in me awake at night. When we got the stockers off, the guy that did most of the work independently commented, “It doesn’t look like BMW spent much time on these.”

I would guess that these headers uncork at least as much power on a supercharged non-M as a stock Z4M, because a Z4M’s stock headers are better designed, and supercharged cars gain significant benefits from free-flowing exhausts. I had previously installed a Supersprint Race exhaust, including a Y-pipe and muffler. With the addition of Supersprint headers, the car went from tame to loud. It spits and pops more than I would prefer, but I’ll be installing cats soon to appease the environmentalist in me, which will also moderate the noise a bit.

Comments on the exhaust note are overwhelmingly positive. Every person that has heard the car has said two things – “God that’s LOUD" and "It sounds amazing.” Down low it’s bassy, similar to the Diablos on my M, and up high it roars. There is some rasp, but don’t confuse “rasp” with a tinny, buzzy, hollow noise. It’s like Satan is blowing his vocal cords out at redline. I can see it being a bit much for some. Oh yeah, and it shoots flames during high rpm let off… evidence of a rich supercharger tune and catless exhaust.

There were some fitment issues in two places. The first is where the headers mate up to the rest of the exhaust (S-pipe on a Z4M). Even if I gave Supersprint the benefit of the doubt, saying the exhaust shop that installed the Y-pipe and muffler somehow influenced the remaining resonated “S-pipe”… it doesn’t excuse the fact that you can’t put both secondary O2 sensors in the remaining bungs simultaneously. Fortunately I had already planned to relocate the O2 sensors, so I went ahead and did it. I put my wideband in the second slot on bank 4-6, but beware: if you plan to put your secondary O2 sensors in the headers (rather than allowing them to dangle around somewhere in the engine bay), you’ll have to weld in a new bung. With my headers being ceramic coated, this wouldn’t have been easy.

There are other downsides too. While everyone that’s heard the car has been highly complimentary, an audiophile would notice increased resonance. Louder is not always better. The resonance reminds me of the same reverberations I heard when I removed the foam during the sound generator mod. Some of it could be due to the combination of the headers and other Supersprint exhaust pieces. At redline it screams, but below 4000 rpm it’s a bit boomy. I expect the planned aftermarket cats to mitigate this. Right now it’s just a quirk, and it doesn’t annoy me enough to spend hundreds of dollars to fix it.

The last negative is the smell of gas that sometimes enters the cabin, which I’m sure other motorists have to endure. This is something that I know will get on my nerves once the new mod feeling wears off. Again, cats are in the near future. If you do this mod and don’t plan to get cats, expect every nearby motorist that knows anything about cars to immediately label you an asshole.

With the combination of the headers and 3.64 final drive, I have no doubts that this car would smoke a stock M in a straight line. I can shift it right into its powerband at any speed, where the supercharger happily provides its contribution to the engine’s increased power to the ground. Overall I’d give the 3.64 final drive an “A” and headers a “B”.
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      10-17-2013, 08:09 PM   #2
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Great review Josh.
I will be doing the 3.64 this winter.

Dave
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      10-17-2013, 09:07 PM   #3
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Great to hear Dave! You will love the way it wakes up the car. Are you going with a limited slip unit?
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      10-18-2013, 04:17 AM   #4
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Don't you have trouble with first gear being totally useless with the short ratio diff+FI?

I wouldn't mind shorter gears, but first&second are spot on; even with an LSD I have trouble getting the power to the ground. 3rd-5th should be shorter and maybe 6th for an overdrive. With 342 lb-ft of torque it's nice to have one heavy top gear for cruising.
That would be ideal.

Headers are indeed loud. I have some larger diameter schmiedmann headers (originally an e46 set adapted to a z4) & mid muffler delete (Cats go there), and I think it's too loud:

No flames though (it's impossible to drive without cats where I live)
And ceramic coating is a must. It's unbelievable how much more heat headers create under the hood (more piping surface and thinner walls)


I still have to change the backbox (that is still the stock exhaust diameter, all the rest of the tubing is 30% larger), so maybe I'll try to dampen the sound a bit. I think I'm going to adapt the stock muffler and see if there's any room for sound improving (to get rid of some of the high notes)
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      10-18-2013, 05:36 PM   #5
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Quote:
Originally Posted by pokeybritches View Post
Great to hear Dave! You will love the way it wakes up the car. Are you going with a limited slip unit?
Yes, found an LSD 3.64:1 at a local wreckers up here.
Gonna go through it and replace bearings etc get it set up correctly before installing.
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      10-19-2013, 01:04 AM   #6
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Quote:
Originally Posted by GuidoK View Post
Don't you have trouble with first gear being totally useless with the short ratio diff+FI?

I wouldn't mind shorter gears, but first&second are spot on; even with an LSD I have trouble getting the power to the ground. 3rd-5th should be shorter and maybe 6th for an overdrive. With 342 lb-ft of torque it's nice to have one heavy top gear for cruising.
That would be ideal.

Headers are indeed loud. I have some larger diameter schmiedmann headers (originally an e46 set adapted to a z4) & mid muffler delete (Cats go there), and I think it's too loud:

No flames though (it's impossible to drive without cats where I live)
And ceramic coating is a must. It's unbelievable how much more heat headers create under the hood (more piping surface and thinner walls)


I still have to change the backbox (that is still the stock exhaust diameter, all the rest of the tubing is 30% larger), so maybe I'll try to dampen the sound a bit. I think I'm going to adapt the stock muffler and see if there's any room for sound improving (to get rid of some of the high notes)
First gear is definitely useful, although a quick shift to second does throw the car off balance with the open diff. As you know, but others may not, I am only doing 6 psi at redline... whereas you're doing 8 psi at anything over 2800 rpm. I could see going to a 3.38 final drive with your setup, but that's totally conjecture. A 3.64 would be too short in your case, and anything less than a 3.38 wouldn't be worth the time or money IMHO. I think a 3.64 is pretty much perfect for a VF car. I'm with you on 6th gear, and I've never understood why car makers design it to be only 15% taller than 5th.

While the flames are cool, they will disappear soon. I'm not keen on running catless, independent of legality.

I absolutely agree on the ceramic coating. I told a friend that I was sure they were cool to the touch after allowing the car to sit for five minutes following a hard run. He laughed... "yeah right"... so I grabbed them. They were barely warm. I'm sure the benefits are realized more so on FI cars.

I'd recommend having a crossover somewhere in your exhaust setup. Besides the scavenging (performance) benefits, the sound would likely improve. It does sound great as-is, but rather than sounding like two 3 cylinder engines working in harmony, it will sound like one 6 cylinder engine.

With regards to exhaust diameters, the non-M's exhaust pipes are a lot smaller than the M's. Assuming BMW optimized the exhaust for the power produced, something around the M's diameter should provide an optimum balance between low end torque and ultimate high rpm horsepower.
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      10-19-2013, 01:08 AM   #7
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Quote:
Originally Posted by dbarton62 View Post
Yes, found an LSD 3.64:1 at a local wreckers up here.
Gonna go through it and replace bearings etc get it set up correctly before installing.
Ask a lot of questions. BMW never produced a LSD for the non-M. If it's "OEM BMW"... it's not an LSD. Nothing against the seller, as I've watched a lot of them turn one side of the diff and notice the other turning, then assuming that it has a little bit of lock. The only option for an LSD is an aftermarket unit or adapting an M diff.
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      10-19-2013, 08:07 AM   #8
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Quote:
Originally Posted by pokeybritches View Post
Ask a lot of questions. BMW never produced a LSD for the non-M. If it's "OEM BMW"... it's not an LSD. Nothing against the seller, as I've watched a lot of them turn one side of the diff and notice the other turning, then assuming that it has a little bit of lock. The only option for an LSD is an aftermarket unit or adapting an M diff.
I have asked the question and the wrecker is going to pull the unit so I can inspect it.
I did some research and came up with the same as you.
I think the price is right for what they claim is a low mileage unit even without the LSD

Not a bad call Josh to see if the 3.64 is enough and then have an aftermarket LSD installed later
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      10-19-2013, 11:12 AM   #9
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Quote:
Originally Posted by dbarton62 View Post
I have asked the question and the wrecker is going to pull the unit so I can inspect it.
I did some research and came up with the same as you.
I think the price is right for what they claim is a low mileage unit even without the LSD

Not a bad call Josh to see if the 3.64 is enough and then have an aftermarket LSD installed later
When I have my LSD built, I'll likely go with a 3.64. Because I already have a 3.64 open diff, other options are available like WaveTrac and Quaife.

A few hundred dollars is a fair price for an open 3.64 from a junked car. Shops list them for $600+, which would be about the maximum I would pay for something that I knew worked. A real LSD is worth over $1k. You'll be amazed at the difference it makes with the supercharger!
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      10-19-2013, 11:59 AM   #10
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Quote:
Originally Posted by pokeybritches View Post
When I have my LSD built, I'll likely go with a 3.64. Because I already have a 3.64 open diff, other options are available like WaveTrac and Quaife.

A few hundred dollars is a fair price for an open 3.64 from a junked car. Shops list them for $600+, which would be about the maximum I would pay for something that I knew worked. A real LSD is worth over $1k. You'll be amazed at the difference it makes with the supercharger!
Found a couple locally both for $250
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      10-19-2013, 03:23 PM   #11
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Those are good prices. The Z4 has a finned diff, which is a little different than the standard E46 non-M diff. The 2.5i auto is the only Z4 I know for certain has a 3.64, but there may be others.

I didn't replace any seals or plugs with it. Despite the "one time use" label, there's really no need.
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      10-19-2013, 09:08 PM   #12
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Great Review Josh, Thanks!

Next week I'll be getting some quotes for the labor. It should be 2-3 hours maximun right?
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      10-19-2013, 11:35 PM   #13
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2 hours is on the low end and assumes you get someone that knows what he is doing. I've been quoted 3-4 before, but I managed to have it done in 2.
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      10-19-2013, 11:37 PM   #14
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Also - a lot of general shops are afraid to touch differentials for some reason. Don't be surprised if you have to run around town a bit.
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      10-20-2013, 08:27 AM   #15
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Quote:
Originally Posted by pokeybritches View Post
2 hours is on the low end and assumes you get someone that knows what he is doing. I've been quoted 3-4 before, but I managed to have it done in 2.
Didn't think it was that quick a project.
There is guy locally (ex BMW Dealer Tech) who raced E46's he now runs his own indie shop
Might just drop the car off with the carrier and have him install it.
Much easier on a hoist.
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      10-21-2013, 06:59 AM   #16
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Did the swap throw off the speedo?
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      10-21-2013, 09:25 AM   #17
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No speedo error.
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      10-21-2013, 04:51 PM   #18
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Updated with dyno video and numbers.

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      10-21-2013, 05:26 PM   #19
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what brand/type of dyno is that?
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      10-21-2013, 05:37 PM   #20
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It's a Dynojet. SAE corrected. Once I get the file, I'll upload a better picture.

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      10-21-2013, 06:01 PM   #21
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Ok, so it's comparable with the numbers that ESS, VF and AA give (I think they all use the dynojet 224/424 as they are fairly simple dynometers with 'less room' for operator correction factors)

So it's +5hp more than the VF factory rating, is that correct?

that torque line looks like it was drawn with a ruler
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      10-21-2013, 10:29 PM   #22
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Quote:
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that torque line looks like it was drawn with a ruler
Haha, yes it does. Though there are perks to this, in that it's easier on things like the clutch. I've been fine on the stock clutch; no slippage so far. When I replace the dual mass flywheel with a single mass, I'll be able to go with a sprung hub organic clutch rather than Kevlar. The stock flywheel is considered a wear item, and I'm fairly certain that it's out of spec at this mileage (129k miles).

As far as the power ratings, I'm not sure. I have headers, Y-pipe, and a race muffler. How does each effects a change in horsepower? It's anyone's guess, but I'd lean towards 15 whp from the Supersprint pieces, based on E46 dynos.

I think there's power to be had in the midrange. AFR at 10.3:1 is way too rich. I have the CEL to prove it. I'll ask VF what they can do.
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