Why not twin turbo instead of a single turbo?

[Bimmerguy2002]

You know how they obviously have a single turbo like on a V-6 or V-8 etc....
Is it a space issue?
Or not enough exhaust gas going through just 3 exhaust ports?
Or sequential turbochargers, like one small for low RPM boost and a bigger turbo for higher RPM?
Might be a dumb question but ive always wanted to know why there arent even twin setups for a 535.

Thanks

[Jeremy]

Twin turbos are commonplace on V motors since there's two banks of cylinders. Just put one turbo on each bank. Using a single turbo on a V motor requires a bit more plumbing usually.

There's really no advantage to using a twin setup on a straight six, since each turbo will only see half the exhaust volume. Sequential setups are technically complicated and offer little gain for the effort expended. My turbo reaches full boost (10psi) at around 3100rpm.

Two turbos also take up twice the space, and are difficult to plumb for intake and exhaust piping, particularly in the e28. Sweeney had to do some "interesting" modifications to his frame rail to get his to fit in the e24.

It could be done, it has been done, but there is little to be gained from doing it. I think BMW only did it on the 335i so they could use really small, fast spooling turbos.

Jeremy

[Bimmerguy2002]

Okay just wanted to know, that makes sense.
It makes me wonder how long some of these motors will last seeing as they are producing over 400 foot pounds and over 350 HP...

[russc]

Okay just wanted to know, that makes sense.
It makes me wonder how long some of these motors will last seeing as they are producing over 400 foot pounds and over 350 HP...

Quite long with proper tuning. Mines had 37k of hard miles before I went to the M30b35 engine runing 425lb-ft. It would have went another 35k even with the leaking head gasket. Most will go 75k+ with good maintenance.

RussC

[Yellow2]

http://www.bmw535bitic.com/

or

http://www.praerien-racing.com/prosjekt ... /index.htm

Search and you shall find !

[Boru]

Sweeney had to do some "interesting" modifications to his frame rail to get his to fit in the e24.

Nothing really "interesting" about it and it wasn't the frame rail, rather, part of the inner fender structure. This could have been avoided if I had another hunk of aluminum tube bend on hand. When I sell the twin turbo setup I'll make that piece so the buyer need not notch.

[Jeremy]

Apparently a "memory error" on my part then. Have you managed to keep all the exhaust bolts attached since Boone at least?

Jeremy

[Boru]

Yeah, no issues since... in fact, the same hood hinge bolts are still in there. 8)
It's off the road now waiting yto be disected and parted out. The way thing are going I estimate the new car will be on the road by May.....2017....

[rundatrack]

Yeah, no issues since... in fact, the same hood hinge bolts are still in there. 8)
It's off the road now waiting yto be disected and parted out. The way thing are going I estimate the new car will be on the road by May.....2017....

Whats the next project?

[Boru]

'86 M635 chassis w/Eibach Pro springs and Billy sports, adjustable rear subframe, M30B35, bored 0.5mm, JE 8.5:1 pistons, balanced, "M" throttles, GT35 spinny thing along with all the bits to connect the open ends together, TCD MegaSquirt ala Peter Florence, Alpina 8.5x17 and 10x17 wheels with big meats..... or I'm gonna lop the roof off of it and turn it into a hot tub.

[Bimmerguy2002]

thats it? like 75,000 miles? ouch!
i would hope that my engine built up lasts over 300,000.....

[Jeremy]

thats it? like 75,000 miles? ouch!
i would hope that my engine built up lasts over 300,000.....

Built up, it won't. Any time you increase the performance of a motor, you decrease its life expectancy. Lifetime of a turbo motor is highly dependant on maintenance and use. I think a street driven m30 on moderate boost would survive to 150k miles at least.

Jeremy

[russc]

thats it? like 75,000 miles? ouch!
i would hope that my engine built up lasts over 300,000.....

On moderate boost levels it won't last 300k,no way no how. Im was running 13-14psi. An M30 wont last that long on that kind of boost. Id say 75-100k. It is 425-450lb-ft after all.

Moderate boost levels will get you farther as Jermey stated, and at 9-10psi, you could expect 150k.

RussC

[Bimmerguy2002]

oh i see, its because its working that much harder and the stress level, heat, friction etc....huh?

[superj]

how come no one talks about supercharging? it seems to be just as easy and then you will have the low rpm power also.

oh yes, hi everyone. long time no see.

[Shawn D.]

how come no one talks about supercharging?

Folks have talked about supercharging. You know where to find those discussions.

[T_C_D]

how come no one talks about supercharging? it seems to be just as easy and then you will have the low rpm power also.

oh yes, hi everyone. long time no see.

Unless you are going find a reasonable way to attach a positive displacement SC to a m30 then you can forget about any low end boost.

Lack of turbos boosting at low rpm is a thing of the past. Any properly setup turbo will produce boost at a very low rpm on a m30.

Todd

[superj]

a few guys on e30tech.com are running eaton m62 and m90 superchargers on their cars. i'm not sure if they are positive displacement though

[superj]

nevermind, they are positive displacement. i googled it

[Shawn D.]

nevermind, they are positive displacement. i googled it

FYI, all Roots-type and screw blowers are positive displacement.

[superj]

i was unsure of what roots meant. now i know that they are the lobed ones and the screw are exactly that, like screws. centrifugal are just turbos that are run on a belt instead of off exhaust.