E34 M5 Plenum

[ajwong]

Hey Guys,
Has anyone fitted the e34 M5 plenum to an s38b35? Is it worth it?Aside from having to move the coolant resevoir, what is involved in fitting the plenum from the E34 M5 models? Can it be done easily enough? I noticed in the etk that the plenum controller requires some sort of vaccum tank to open and close the flap. Is that something that must be retrofitted?

Thanks,
Andy<img src="http://home.comcast.net/~wong.andrew/pics/sig.JPG">

[ScottJ]

I had the S38B38 installed in my 88 M6 which required the ABS unit, the coolant tank, and the power steering fluid tank all be relocated. Further, relocating everything the way Brett Anderson did, no BMW factory airbox would fit, so a cone filter was necessary. Not at all an easy swap. Besides, the E34 plenum need a signal from the ECU to open the resonance flap in the plenum - a signal that the B35 ECU does not provide.

[bob.knox]

[b.kirk]

I really want one ....<img src="http://www.mye28.com/avatars/bnc.jpg" height=131 width=259>

86 M535i
85 M635i mit 73K original (just sold.. :()
88 E30 IX Touring

[ScottJ]

The 3.8L is great. Lot of money spent to get it into the hole, but once it is there, its great. Pulls really hard and sounds great with no cats and the UUC E28 M5 exhaust. To do it again, I would probably just have a Metric Mechanic engine built and forget the six speed conversion. Too much spent on moving pieces around the engine bay and fabrication to make this an economical conversion.

Scott

[Philo - e28 M5]

I hate to always quote Fahey but apparently he has done dyno testing with both plenums and feels the stock one performs better. Call him for details.

Howver.., if you have a programable computer you can control the fuel curve, timing and resonance flap to help adapt to the E34 plenum. But then your changing over a bunch of stuff on your engine to first adapt the programmable ECU to help control the plenum. Yes,allot of work. You'll get more bang for the buck if you chip it and drive it.

Also, the resonance flap is actuated by a small plastic vacuum tank(4" long by about 2" dia). A solenoid tripped by the ECU allows vacuum from this tank to open the resonance flap. One thing though, the flap opens at two different points based on a combo of RPM and throttle position. Since the B35 doesn't have a progressive TPS you're going to be hit and mis as to when to open the flap. There is also something called "histeresis" (sp?) that keeps the resonance flap from opening/closing repeatedly if you happen to be cruising at just that exact RPM/throttle position.

I did a fair amount of research a year ago for my stroker engine and unless you do a complete B36 or B38 swap like Scott or use a programmable ECU putting the E34 plenum is allot of work with little to show in performance.., other then bling factor of course.

Philo.
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[Eric J Miller]

Let's get the facts right...yes you will gain from updating to a later plenum...BUT let's do some home work first...3.6 uses the same as 3.8 & that's about it...on a 3.6 it's controled by a "box" much like an old 533 had a idle box & on the 3.8 the dme does the job & it's does it better, in the fact that it has two different "rpm ranges" that's it opened & closed @.The 3.6 only one opening....now It's my understanding that you must use the 3.6/3.8 which ever your your using...airfilter box as the mass airflow will get a "shadow"...that's how it was told to me by CARL NELSON...he's been there done that...no test pilot s__t. I'm doing a 3.8 system & have a lot of 3.6 M5 stuff if anybody got an interest. I was going 3.6 & found a guy in Germany that had the 3.8 stuff for the right price...same guy BK got his crank from on E-bay.de..I could have got that same crank for 350USD...Brad paid a bit more...the way I did it was to E-snipe the 3.8 Throttle Bodies for 450USD!!! & got the DME & harness & etc parts for another cool grand IE a complete 3.8 set-up to convert over to 3.8 Minus the pressureized cooling system like the 3.6/3.8...I have that 90mm RD crank & rods so it should be sweet with the Schrick cams...I'm going for that 375+HP mark...It's all fits go look @ some of the photos from the fiver fests...there a couple fans out there that have a 3.6/3.8 in the E28...one must address the engine mounts that's a problem if using the late block...been there done that onlate M30 in my 1986/535 with a 1993/735 engine...but that's another story, I'm Eric& that's my three cents worth folks....

[Philo M5]

controls the two stage plenum. The Motronic is the brain of the whole mess along with a solenoid, diaphram and vacume tank.

So Andy..., doing this on a stock S38-B5 would not be prudent.

Eric.., getting control of that caffine problem yet ;)

Philo.

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[RoyW]

And, here it is:

[ScottJ]

Here is how Brett Anderson did the B38 swap - probably no more work than a B36 swap.
Scott Jancura
88 M6 with 3.8L S38B38 engine and six speed
98 M3 (wife's car)
91 525i (wife's car)