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Twin Turbo Project

147383 Views 199 Replies 60 Participants Last post by  Gixxerboy63
Hello e34 members,
I wanted to share this with all the members here. I do appreciate the great wisdom on this board and I am a huge fan of the e34 M5.

Although I do not post often, I thought some of you may enjoy this. This project was born from a blown head gasget. It is in the final stages of pre-fabrication and the motor will be pulled next week and sent to Jim Rowe at MM for a low compression complete rebuild. Car is a 92 3.8 with about 70K mi in really nice shape that I bought about a year ago and put much TLC and $$ into.

the plans are a driveable TT with a powerband resembling the original. plan to drive in cool weather mostly. The chasis was ready before the blown head, has many nice upgrades.

The muscle behind this is my friend and head mechanic Jon Firpach here in Arizona. He is a real talent, a BMW fanatic to the core, and a stickler for detail. I must admit that I was very hesistant initially, not wanting to ruin any part of this car. After seeing (and driving) and realizing how far turbo technology has come, I slowly became convinced I could make something worthwhile and still honor the original. I'll be the first to acknowledge if I in fact turn out to be wrong.

I'll try to keep those interested posted in the next several weeks. the photos are of simlpe pre-fab placement, the manifold is being fabricated as we speak. There will be an air/water IC in place of the old air box position.


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Sounds a very intriguing project. Best of luck!


ralph (vadas1)
Looks like a good job!

What are you using for mapping / ECU?
wonderful. beautiful...

Very nice project.

I believe your power band will be full of torque from 3000 rpm till redline.

Your are using twin Gt28? Gt25?

I pondered about twin turbo`ing S38, but went single GT47-88. Right now i am also working on my S38.

Are your turbo manifolds log type or tubular?

Keep up the good work.

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Thats different.:applause:
The location for the Turbochargers.:)
They seem very close to the bulk oil of the engine & transmission.
(Might be the angle of the pics)
Are you going to shield these parts from exothermic heat soak ?
The vehicle has an aux oil cooler which does its job on the std engine.
Have you got any generic or projected engine bulk oil temps ?

I notice that you are running integrated poppet valve wastegates in exhaust housings.
I have found that heat stressed areas where heat can be trapped or exhaust gas temps get
high for extended periods, I have had these poppet valve waste gates seize part open.
The cure was inconel poppet valves or remote waste gates.
The remote waste gates is best solution imho but space is tight here.
How much MAP will you run at ?

Good luck with the old girl;)
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Thanks for the replies. As to the mapping, this was the luckiest part. Turns out there is a company making a piggyback system to the edc that uses air speed vs. MAF. we went with this system. I'll get the name for you.

The turbos are GT2871R. the manifold is tubular 3". I'll post pics when the manifold is done, Jon does beautiful work here.

Farrell, you are right, the location is unusual. we wanted the car to appear as "stock" as possible from above, and the group in charge felt there was plenty of room properly shielded to place them close. We had already prepared modified engine mount brackets to make sure we could fit dual intakes but we ended up not needing them. We really wanted this car to have minimal lag and I think going with two smaller turbos and placing them where we did should give us the best shot. We plan on extensively shielding that entire area for sure. We are planning an auxillary oil cooler as well. As for the wg we have no plans for remote but I will pass your point along to Jon, appreciated.

The motor is going to be 8.5cr with all lightweight internals, Weisco pistons etc... We plan on running about 12 to 15 psi.
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Good reply:thumbsup:
The numbers make sense.
The FI profile is shadowing Nissan RB26 DETT engine except with much greater
engine displacement.:applause:
Heat is concerning around exhaust hsg's
Depends on use I guess.
In Europe, on Autobahn or some tracks here...phew !
I think your man knows his sh1t though.

Very interesting.
Good luck;)
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go get a real car :hihi:

BTW interesting project mr Wolf. I think a lot is down to how the manifold is made. Tubular , cast , they all have pro's and cons.

Keep us updated!
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haha its a joke

the Jap guys usually are very much into their own stuff and RBDETT is the engine code for the Skyline that Sir Farrell drives.
Great project. It's good to see something like this state side. Will you be bringing the car out to California anytime after it's done? :)

If so, I may have to buy you a beer in exchange for a ride if you're up for it. :cheers:


No problem Brian! I do have family in San Diego. If you ever make it to the Phoenix area PM me and we can meet.

Motor out yesterday, manifolds being finished. Expect things actually to move quickly as the motor builder has been waiting with all parts ready and Jim can do these 6s in his sleep. We expect a 2-3 week turn around on the motor.
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I'm actually hoping to move back to San Diego when I finish school. At that point in time I will get my M back on the road and would not be the least bit opposed to a road trip to AZ!

Best of luck with the project. Can't wait to see the finished result.
It is coming along nicely, thanks. the head mechanic on the project is waiting to get his posting priveldges on the board and plans to post a more detailed update with pics of the finished manifold soon.
the motor is out and should be on its way to Metric Mechanic in Missouri by the end of the week. I spoke with Jim Rowe yesterday, parts are in, he said 4 week turn-around on the finsihed motor. after that it should go quickly.
Mr. Wolf, you definitely run alone on this path, and I salute your vision. Do you mind sharing your power goals, and your plans for transferring it? I take it from your earlier posts you will be running a modified chassis, would you please share the details on that as well? This has always been an interesting debate on whether the perfect manifestation of I 6 N/A poetry would produce the same in a forced inducted beast of a daily. We know it is capable of monster numbers in a straight line, maybe you will finally add substance to speculation. Good luck with the tuning and there are many that will applaud that nut being cracked. Thanks in advance to the key to that.
I'll give it a shot M. First the bad news. I think in fact some of what makes the e34 M5 so fun and special will in fact be lost. Going really fast can be over-rated. How you go fast is often times more important I think. I remember my '75 trans am 454 from high school, it always sounded like it was going twice as fast as it was, and that was really all that mattered most of the time. What will be lost to some degree is is the great sound and the feeling that the motor wants to pull slowly well past redline. For the track, no question I would keep the car NA and get the most out of it possible. I considered this route stronlgy. It is the reason for example that I think the gt3rs is the real gem in the porsche lineup, not the tt.

Now to the upside. One of the reasons I love BMW is beacause it is somewhat inconspicuous and underrated. Turbo technology has really grown in the last decade. The turbos on this car are water and oil cooled and wildly more efficient than anything from the 1990's for example. The possiblitly in a smaller twin set-up does exist to nearly reporduce the powerband profile, just bumbing it up significantly.
That possibility is intriguing to me. The ultimate question is whether what will be gained will outweigh that which will be lost. I hope so, but as I said in my initial post, I will be quick to admit if it doesn't make for a better car.

We do not have a power goal, in fact we really have no idea what it is going to produce. Our main goal is to try as much as possible to keep the "feel' and look of the original intact. That being said, this set-up should not have trouble throwing down an additional 150rwhp without pushing it hard at all. We do not plan on pushing the limit even though the motor is being built to withstand considerably more. the car as it is set-up should give a stock e60 a serious run under all conditions. Everythng would certainly point to that.

The chasis of the car has an all new front and rear end with new steering components, Ground Control coilovers, Dinan sways, factory M parallels with Toyo Ra1's, UUC brakes etc.... . It is one of the best handling sedans I have ever driven (far better than stock) and handles better than my equally maxed out e39. Our additional plans include a single piece driveshaft and possibly a custom support for the rear diff ala Dinan's for the e39.
I was by the shop tonight and saw the motor out for the first time, Jon was working on the manifolds, he plans to post some pictures soon. The motor is easily as heavy as an S62.

We have a question for the group: Any good clutch suggestions for this car?
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making some kit!

My name is Jon, I am one of the lucky ones that get to design and build a unique project like this, I will be doing all the air control design and fabrication and my associate Joe Morell will be creating the fuel system. I apologize for the delay in posting, I know there are lots of questions and I will do my best to answer them as they come.
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First project description: we at GoodSpeed Performance believe in tailoring a customers car to there specific requests. In this case we are not going for maximum raw horsepower #s. this is to be a reliable, daily driven, cross country capable car, and to make it even more challenging, it is to remain relatively stock looking, no huge air to air in front, no chrome, no polishing, no bling, witch personally I like. In addition the power curve must be smooth and unobtrusive, my plan is to tune the car to have a nice sweeping torque curve, there will be no freight train hitting you in the back when the boost comes in. for this reason I chose 2 GT2871 turbos this is at the top side of the 28 family but still small enough to control (minimize) lag. Location is a mid level staggered orientation, I did read some concerns on this location but it is proven ideal, of course it is also challenging (space constraints). The exducers will have there closest point at the middle of the water jacket, concern for location in correlation to the bulk of the oil is not relevant in this case, and the location is not to be that low. Location of the turbo center section that low would result in inadequate oil drain back and I am not a big fan of using sump systems if at all possible. Research has shown that turbo exducer location is optimal at the water jacket especially in cast iron blocks, the heat will have substantially less thermal transfer and what transfer there is, is well shielded and dispersed by the coolant running through the jacket it self. This is most likely why most manufactures use this location for OEM component placement, nothing new I just use what works for the application. It is also desirable, when possible to keep heat transferring components as close to each other as possible, for lost heat, is lost energy. For this reason the turbo in relation to the exhaust ports are as close as possible this will transfer low cfm heat energy as quickly and efficiently as allowed by space constraints. Long runners have poor thermal retention. At hi cfm this concern dissolves, example; a big turbo on a race car where it’s designed to operate in a narrow band on the compressor map. Keeping in mind that fast spool up is a primary goal, the shorter the manifold runner the faster the spool. The turbos were also kept low to reduce under hood temps, we have found that when locating a turbo up high in the engine compartment, it causes heat to be trapped and cause many problems, of course this can be combated with heat extractors and vented hoods, but keep in mind this is to remain stock looking. We have also found that in most cases with turbos located lower in the compartment they gain the benefit of air from under the car extracting heat from the arias such as ours. I believe there was a question about the internal waist gaits, I chose internal waist gait for reliability and simplicity, external waist gaits are very good for race applications but for a street car, the less parts and pluming the better, plus it also gains you thermal energy on the low end, heat lost in remote piping is heat that is not benefiting the spool of the turbo. As for the heat damage concern, I substantial faith in the Garrett unit, I have never seen a Garrett turbo waist gait diaphragm fail from heat and I have used them in many heat constricted places, examples of this are the unbelievably tight APS 350Z turbo kit witch uses a Garrett and the Tial R650 kit for the S4, no heat relief there. With proper shielding, WOT for many miles at a time will be no problem. Wow! ok I didn’t mean to ramble on like that, Probable more that most wanted to know, and on that note, that’s all for tonight, I will post more later, got to go.
<o:p> </o:p>
Thank you for welcoming me to your community!
<o:p> </o:p>


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MR. Wolf, great answer: "How you go fast is often times more important I think", which also answers the question I am sure that would follow, why not just get the E60?
Afterall, this car(E34) was meant to go fast, almost as fast as any production car, much less sedan, it is only a matter of going fast, quicker, by installing the turbo, and hopefully maintaining the qualities that make it unique to the discerning driver.

I have not seen anything but half shafts on even the most boosted BMW's unless they were frame dedicated dragsters. They have half shafts good for 800 lb/ft of torque which should be plenty and won't take away from the handling.

If there is anyway for a fit, Southbend clutch is by far the smoothest, most quiet solution. The "Feramic" material doesn't grab like the ceramic or screech or squeak or chatter, and can be feathered better than stock. UUC might have this as well, and I know they have the ceramic and ceramitallic. BTW, I don't know your experience with boosted cars, but overbuild to your goals -it is inevitable that you will want to "turn it up" now and then.

Best of luck, and thanks for sharing the adventure, and the pictures are great, please keep it all coming.
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You are right, e60 is way more practical but:
Smaller, lower, lighter, more nimble, better cockpit, better build, better handling, way better looks, better feel, and on and on e34 vs e60 in my opinion. that car just feels too big and detached for me, even the manual. I really don't know why. Maybe it just crossed some threshold into too "big and luxurious" that the e39 was toying with all along.
it also is my hope that my car, when finished, still has as much of the raw e34 feel as possible that is totally missing in the e60 IMO and was tough and expensive to create in my e39. Quite frankly I think it is going to be a far more exciting and involving ride than an e60. I think from 3k on there will be good power and a significantly more torque. I never felt I had to really "drive' the e60, I think this car will need some paying attention to as the driver. We'll see. No one said any of this was practical however!

thanks for the clutch recommendation, looking into that.
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