Turbo in the rear

[gstyle704]

So I just saw my buddy's e46 m3 and he is running his turbo out back where the muffler would be it looks pretty cool. I know alot of us e9x guys aren't running turbos because of lack of space in the engine bay. Was wondering what people thought of maybe running a similar setup in our e9x M3; maybe twin turbo? Any thoughts. Ps he is already running over 650rwhp at low boost on a single turbo and he has more tuning to do he figures he'll be over 800rwhp easily; I can't wait to see it out on the road!!!!

[shendrick]

Lag must be awesome.

[kthxbye]

I agree that there are many great SC systems out that are already proven for performance and reliability.

There is some president behind a rear mounted turbo charger. Its a common option of F-Body cars and I remember back when I had a Mazda 6 this was the only option.

- Addresses space issues
- Addresses heat issues
- Addresses concerns with additional front-end weight
- Lag is actually minimal with these types of setups

[THE TECH]

There was a thread on this before a while back. It went nowhere.

[gstyle704]

actually there is very little turbo lag. the only thing that sucks is he has to to zip tie his dip stick so it doesn't shoot off like a bottle rocket lol.

[m3an]

Originally Posted by gstyle704

actually there is very little turbo lag. the only thing that sucks is he has to to zip tie his dip stick so it doesn't shoot off like a bottle rocket lol.

wayy to much crankcase pressure then... He needs to remove the PCV setup and run some catchcans to alleviate the pressure under boost.

[Erhan]

Originally Posted by shendrick

Lag must be awesome.

[mkoesel]

I opened this thread hoping to see some high speed hard core porn.

[pbonsalb]

STS pioneered the rear mount turbo kits. Generally the turbo experts look down on this because the turbo is located at the coolest part of the exhaust, where gas energy is lowest, and the boosted air has to travel all the way back to the intercooler in the front of the car. Response is not comparable to a standard turbo system. On a V8 with plenty of low end torque to get the car moving, the delayed response probably is not an issue and the midrange to top end is very entertaining.

Tuning can be an issue. First, the stock compression is probably too high for a turbo. Even this turbo will still make more midrange boost than a supercharger and that is the rpm range where boost and compression can be most at odds. There are no low compression headgaskets for these cars yet like there are for the S50 and S52. There are only expensive low compression engine rebuilds with new pistons at a minimum.

Then there is ECU tuning. Tuning a turbo with its nonlinear response is much more challenging than tuning a naturally aspirated or centrifugal supercharged motor. It can be done, but I am not sure how many shops can do it at present.

If you look at the pump gas HPF turbo kits for the fairly high compression S54, they really don't do much better than the stage 2 centrifugal supercharger kits. This is because the S54 is a low torque high rpm motor. The S65 is the same. With the big cams needed to make power at 8000 rpm, the bottom end is weaker. You get more horsepower out of the available displacement, but not more torque. You have to trade some torque for the horsepower.

So the boost comes in slowly and there is not so much of it in the midrange with the turbo to make the turbo significantly better than the centrifugal on pump gas. Run race gas or meth and raise the boost and the game changes in favor of the turbo. With the turbo, boost is adjustable so it is easy to turn it back down for pump gas. It is a pain to swap supercharger pulleys every tank of gas. Rebuild the engine to lower compression and run higher boost and the turbo again outshines the centrifugal even if the centrifugal was also fitted to a low compression motor. As the boost goes up, the centrifugal drags more and more on the crank while the turbo recycles exhaust gas energy -- it is a very efficient way of making power.

Maybe in a few years there will be turbo solutions for the E90M3. The centrifugal is making nice gains in the meantime.

For the S54, HPF makes a kit, ProEFI may make a kit or do tuning, and Maximum Psi is making a kit with Techniques Tuning doing a turbo (TT currently makes kits for the E36M3 and regular E46 and has been involved with custom tuning on other forced induction projects, but I do not think it has delved into the S65 ECU yet).

[SchnellM3]

wasn't this discussed not too long ago??? Then we actually saw someone in South Africa turbo their E92 though not in the rear, since they were able to fit it up front due to the right hand drive...

[crabman]

I have been in an sts vette and there was no noticeable turbo lag, felt just the same as my tti kit. Rear mounted turbos are much more viable when you're only looking to make 5 to 7 psi because its easy to make that boost even with the inefficiencies involved in the remote mount. Heat issues and packaging are also in many ways alleviated by rear mount turbos.

A couple things not mentioned, rear mounts give you more opportunity for leaks and a lot more country to cover trying to find them. You have to mount your air intake somewhere and typically thats going to be right back there under the car with the turbos, ya have to pay a lot of attention to those filters.

Myself having gone twin turbo I would probably just go centri were I to do it again. So much simpler and less expensive.

[Singletrack]

Originally Posted by mkoesel

I opened this thread hoping to see some high speed hard core porn.

HAHAHAHAHAHAHA...I was going to say something obscene also, but you beat me to it.

[tightie]

Originally Posted by shendrick

Lag must be awesome.

[VCP]

where you going to put boost tubes riddle me that

[m3an]

Originally Posted by VCMperformance

where you going to put boost tubes riddle me that

ideally you would run a collector and run a single 3" or 3.5" exhaust and use the other area for the charge piping to do a single remote mount turbo

[CecilHartlely]

There is a turbo built in progress