any word on rear mount turbo setup
 

on a 98 civic... would u go with or against a rear mount setup...

against: these systems are for larger v6/v8 vehicles with no room in the engine compartment. a 4 cylinder engine will have a hard time spinning up the turbo because its in the back of the vehicle. it adds a lot of weight. rear mounted turbo systems are limited in power output.

k cool yea i was leaning toward front mount... thanks man

Well i wouldent, but, I also wouldent say they have limited power output, my boss put twin 67mms in the back of his ls2 corvette and it made 812hp on 14psi stock motor.

LS2. What is that 5.7L? Comparing that to a 2.0 or a 1.6, not the same cookie. You can run a rear mount but it will cost more than running a simple set up up front with all the parts available for your car now a days.

Adds a lot of weight? Wait... what?

I am building one at the moment for a car that has no room in the engine bay and yes it is a 4 cylinder. The only added weight is the added piping you need to run back to the motor, The return oil pump and the hose to bring oil to the turbo and to return it back to the motor. This is about 10-15 lbs of stuff. The gains made by adding boost will far out weigh this.

The trick to a rear mounted setup is sizing. You need the hot side to be a bit smaller than a unit you would use up at the exhaust manifold. Yes you will have a little more lag but from what I have been reading it is all but eliminated with proper turbo sizing. On the plus side you don't have to run an intercooler until you get in the 10+ PIS range as the pipe running back to the motor is longer and will help cool things. The turbo its self is using cooler exhaust gasses and is out of the engine compartment so it stays cooler as well. Because of this you should have better turbo lift all other things being equal.

I was not a fan of the rear mount system but after doing a lot of homework is is like everything else with proper engineering it is a vary viable system and usually is cheaper to install if you can do your own fab work. If you are not willing to fab things up then a front mount is the way to go there are bolt on kids for your car that can have you running boost after a weekends worth of parts swapping.

I have already built a remote mount setup for a 1.6 liter miata. it worked well for my first turbo build, but was real down and dirty in construction. dean is right, exhaust turbine sizing is critical. in a sub 2.0 litre 4 cylinder, you really want to keep it around garretts gt20-25 frame size. there are a few tricks to the trade but that is the general idea. another thing you have to watch is routing oil. get the best scavenge pump you can afford.

Also with respect to weight you are eliminating the muffler. The weight removed by the elimination of the muffler is roughly a direct swap in weight with newly installed turbo. So you have a net gain of zero weight by adding the turbo. Thus the only real weight you are picking up is the added piping and plumbing to get the pressurised charge back to the motor and the oiling system. I bet that the total net gain in weight between a front and rear mounted set up is 10 lbs or less especially if you eliminate the IC. Another thing to consider is that most manifolds for turbos are cast iron needed to support the weight of the turbo. With a rear mounted system you can keep your tubular headers and this will save you some more weight as compared to the cast iron manifolds and by keeping the headers you get better exhaust scavenging of the cylinders.

Again with proper engineering and design the systems can end up being relatively equal.

I actually have the cat back out of my Porsche at the moment and should put it on the scales. I can then take the second cat back that I modified and added a KO4 and put it on the scales to see if my theory is correct.

the only doubt i have is the scavgning of the exhaust pulses. in a remote setup the entire exhaust tract gets pressurized between 3 and 10 psi.. depending on the turbo exhaust a/r. but better flow is better flow.
also the exhaust event pulses get get blended and lessened when it passes through the catalytic converter. the pulses are there... they just aren't as bright.

and there is actually a small gain in weight with the turbo over a stock muffler. but it is definitely offset by not having a huge cast mani up front. a net loss in vehicle weight overall.

You are correct and this is why sizing of the hot side is so important. You have to go smaller than a front mount to make up for that.

Since the exhaust gas will be cooler and thusly denser, why would you need a smaller turbine than if it was mounted in front? Just curious.

Because they also have less energy. The equation for energy a turbine can extract includes incoming air pressure, temperature, and mass flow rate - but not, directly, the density. Less temperature will drop the air pressure and temperature while leaving the mass flow rate the same.

Lot of money for a little play, don't you think?

Although I have a rear mounted turbo, id have to agree with the nay says in that unless yu go the pump to push any decent sized turbo, front mount is the way to go wit a 4cyclinder. may be a V6 with a properly sized turbo. Its hard enough to get a rear mounted V8 to run efficiently with wrapping exhaust pipes, proper sized turbine that balances flow and spool without sacrificing to much power or drivability. I got a T76 on my LS1 trans am and spool doesn't kick in until about 3000rpm and I have a 3200 stall. I have the grunt of a V8 to make up that difference. I couldnt imagine trying to do the same with half the cylinders even with a smaller sized turbo. you would have to have something in the range of a 50mm turbo if not smaller just to have ay fun out of it.