Other Cars Without Turbos

[jmp2006]

I would like to see Subaru put the flat 6 with a turbo in the Impreza - would probably be good for 375hp!

Why would you want to make the Impreza even more front-heavy? Getting that kind of power out of the current engine isn't that difficult anyway, but a lighter car with ~325hp would be much more fun. Personally, I'd rather have them keep the flat-4 w/ STi sized turbos and a slightly more aggressive factory tune and you're well into the 300s as far as power while keeping the lighter engine. I'll take less weight over added power any day of the week.

[spt wrx 2k8]

The G's are NOT true AWD. The system is controlled electronically, these cars do NOT have diffs.

Some of those cars, like the G37x are awd and still just as fast.

[wrxgc]

Each person has the thing that tickles their fancy - for some people it's turbos, for some people it's displacement, etc. BUT as far as competing cars that have AWD, subaru has certainly taken advances on providing some of the best AWD support. For reference, please watch the video provided below. Symmetrical AWD > other AWD.
http://www.youtube.com/watch?v=2OzK-oRPCbs

[zax]

OP: I would seriously recommend reading up on forced induction. Here's a place to start:
http://en.wikipedia.org/wiki/Forced_induction

There is essentially only one way to increase the torque out of an internal combustion engine tremendously -- very broad, but somewhat applicable -- and that is to increase the amount of oxygen in the cylinders so more fuel can be combusted. There are two methods to accomplish this feat: 1. increase the displacement of the engine i.e. the GM LS-2 engine displaces 6 liters of volume to produce approx. 400 hp or 2. Forced induction whereas a turbo/supercharger physically forces air into the cylinders to create a similar situation. A WRX 2.0L with 14.7 PSI of boost (1 ATM) will be a stoichiometric equivalent to a naturally aspirated 4.0 L engine running at optimum efficiency IF the turbocharger doesn't create excess heat.

There are two problems with the last statement I made: First, a turbocharger is not at peak efficiency over the full RPM range. That is the turbo has an efficiency range that may be limited to approx. 4000 RPM over which the boost will be maximized. For a stock WRX, the efficiency range is about 2000 - 5500 RPM (I believe) therefore the power is robbed at redline. This can be remedied with a larger turbo, but at the expense of greater boost threshold and greater lag (worse driveability IMO). A supercharger will have a greater efficiency range, but is overall less efficient than a turbocharger due to the parasitic loss from the supercharger pulley. The second issue with the statement above is that I mentioned a 4.0 L engine running at optimum efficiency. This assumes that the naturally aspirated engine is operating as a perfect vacuum and equalizing to exactly atmospheric pressure in the cylinders. This does not occur without the aid of a passive forced induction system such as Ram Air. Furthermore, the absolute pressure in the cylinders decreases as the RPM increases because breathing is not as efficient at this rotational speed. Variable camshaft and valve lift timing aims to increase the volumetric efficiency at these RPM ranges, as does forced induction.

Clearly Subaru chose to take the small displacement/forced induction approach, mostly due to the fact that symmetrical AWD requires the engine to be stuffed in the very front of the car. A big GM LS engine would cause the car to be veryyy front heavy.

[CGimpreza]

Once again, another thread that has taught me some things I did not know.

[Willard]

Fantastic post Zax

[teikyo30]

Is it possible to make the WRX twin turbo?

[Drews]

Is it possible to make the WRX twin turbo?

Absolutely. But if you're sticking with a stock turbo it's pretty worthless to go with a twin scroll kit, from what I've read. You're spool time is already quick with the smaller turbos, so slapping two smaller turbos under the hood isn't going to be very beneficial.

If you're looking for faster spool times there are other mods you can do that are chaper than a twin scroll kit and more beneficial. An external wastegate setup, hi-flow cross pipe, port and polishing of your exhaust manifold, or ceramic coating are all great options to help your spool time and get more power from your stock setup.

[oguitar]

If you mean twin turbo as in having two identical turbos then you could possibly do it, but it won't be cheap. I am not sure what you would have to do with the ECU though. It would be a big project indeed. My friend has a twin turbo BMW 335i and it is quick as hell.

[Drews]

If you mean twin turbo as in having two identical turbos then you could possibly do it, but it won't be cheap. I am not sure what you would have to do with the ECU though. It would be a big project indeed. My friend has a twin turbo BMW 335i and it is quick as hell.

The 335i comes stock with twins.

You wouldn't have to do anything to the ECU but retune it for your twin scroll setup. They make twin scroll kits with VF 37s? (I think) that are direct swaps for the WRX. But you aren't really going to get any real benefit out of it.

[JoeMomma]

ugh i know ive seen a tt'ed wrx/sti before but i cant find it now

[Nigel79]

I agree about naturally aspirated engines getting boring after a while. Straight power all the way through gets old. I had an '04 GTO and it was fast but I got sick of it quick. Forced Induction is the way to go for the fun power band.

[oguitar]

The 335i comes stock with twins.

You wouldn't have to do anything to the ECU but retune it for your twin scroll setup. They make twin scroll kits with VF 37s? (I think) that are direct swaps for the WRX. But you aren't really going to get any real benefit out of it.

I am talking about having two turbos not a twin scroll. Their are twin scroll kits out there but they are expensive. I have never seen a twin turbo WRX. If you have a link post it I would like to see it. Now what would really be nice is a bi-turbo set up.

[Anub1s]

I am talking about having two turbos not a twin scroll. Their are twin scroll kits out there but they are expensive. I have never seen a twin turbo WRX. If you have a link post it I would like to see it. Now what would really be nice is a bi-turbo set up.

There's a few of them actually. Even a twin-turbo, supercharged WRX.

[mycologist]

I would be fine with a car with a larger motor with a turbo placed further back.

I saw last night where a gorgeous 260z rotisserie restoration with a full 300zx swap sold for only $12K. While the purist in cringes slightly and the NA straight six was a joy in my 280, the claimed 400hp FI v6 sounds like it might do the trick.