chenzob

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

busa4

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.

chenzob

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

1slow1g

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.

sleepy 7 bolt

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?

dean924s

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.

rohmer

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.

dean924s

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.

dean924s

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.

rohmer

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.