turbo and how much are we looking at
 

iv been modifying my svx for about a year now and I decided I would like to put some boost to EG33. I have read that it had been done to a few out there so I was wondering which turbo they decided on and the intercooler used also if the internals were forged or just run a low amount of boost without forged internals and if custom up and down pipes had to be made

Supercharging is the only way to go on the SVX IMO, But they have been turbo'd over in Japan and we have 2 members here that have them too. I just have yet to see any decent numbers posted on a turbo SVX and with the cost and custom work needed, It isn't worth it to me. Just my 2 cents.:)

Standard answer I give, doing a turbo setup right costs the same as doing it cheap once you get down the road a bit.

Doing a low boost kit is in my opinion risky as very few turbos work at all at low boost, and even worse... none of them in a size that the SVX will like. If you have to do it, find a BIG turbo with as good of a low pressure ratio map as possible. You will note that turbos are very inefficent at high flow and low pressure ratios, this is what happens when you try to run a small turbo at low boost. A big turbo at low boost might be "soggy" on up to out and out laggy, but it will atleast make a performance difference on boost and not just burn your motor up like a small turbo. Even worse a small turbo will have a small turbine or "hot side". Small hotsides equal large backpressure which equals lower performance with higher stress. Going with a larger hotside can actualy decrease lag despite the common ricer wisdom. This is due to the fact that the compressor side is powered by the turbine, and too small of a turbine will not provide sufficent power to the compressor. Imagine if you ran a second engine to power the supercharger on a top fuel dragster... A 3cyl Geo Metro engine just won't get the job done, yet thats what many of the very popular aftermarket turbos DO, is put a tiny turbine to power a huge compressor.

Honestly If I was to do mine today, I would start with a built Forced induction motor from ECUTune, a built transmission (or 6spd swap), and then a properly built Turbocharger setup from someone who knows what they are doing. Proper external wastegating, proper bypass setup, proper piping, proper intercooler design, etc. Its comical the number of times I've seen a Stock turbo STi drop 10-15whp with a FMIC that wasn't exactly thought out. Thats compared to the stock topmount which people wrongly think of as too small and incorrectly placed. Sadly the SVX doesn't even have room for a proper elbow into the throttlebody, much less a TMIC. In this application I'd honestly say that doing a Air/Water IC replacing the plenum is the only way to fly on the SVX if your budget can take it. Super low pressure drop and minimal lag. Running the pipes to the bumper for a small FMIC just adds alot of volume to the system and alot of pressure drop. Again I'd assume ECUTune could make you a very nice Air/water intercooler intake manifold combo with his experience at doing the fabrication for the supercharger kits.

Last, don't be shy with exhaust pipe diamiter. I've seen cars that I'd be running 3.5" or 4" if I could actualy get the parts to make an exhaust in that size properly. One car shoved a 20ft long aluminum chimney "pipe" a good 8-10ft off the tailpipe once it hit boost as the internal 4" diamiter just ah... wasn't enough. Oh and DON'T taper the exhaust like some companies do claiming that it makes more power. LoL just because the exhaust is cooler and more dense, doesn't matter, you still have the same mass flow. The reduction in energy does make it more dense, but it moves slower too. So tapering down to 2.5" say from a 3" is still bad as the slower cooler exhaust gas has even less room to wander out, and thus slows down more, which of course provdies more restriction.



Last thought, it would be a ***** to tune perfect without running the engine as a pair of 3cyl engines, but you could use an asymetrical setup on the turbocharger. This means only running one bank of cylinders into the turbocharger's turbine. This is normaly done to keep a large engine from overspeeding a smaller turbo and er.. breaking turbo and motor. So if you say got a VF-39 from a STi, this is how I would run it. More lag, but likely more peak power as you have far lower exhaust restriction. This lack of restriction on the one bank is what causes the tuning issues. I'll finish with this style of setup is honestly for torque and MPG boosting, not pure power. The difficuties doing this right prevent me from recomending this as a good idea unless you want to spend the time and money for real heavy R&D to make it right.

http://www.subaru-svx.net/forum/showthread.php?t=38251
http://www.subaru-svx.net/forum/showthread.php?t=32280

superchargers suck!
 

Tubo is the way to go, dont listen to budfreak.i am a professional car tuner and trust me supercharger is only best for 0-60. turbo is constant boost!!!

uhhhhhhhhhhhhhhhhhhh,

Superchagers create a static pressure...... Turbochargers have to spool.

Uhmmmmmm..... yeah...... So anyway..... (tumbleweed blows by)..... What phil just said..

I personaly think turbos are the way to go, but ah not for a single reason you just said. Mostly since what you just said is just completely 100% wrong.

Strange, My supercharger makes a constant 9 to 10 pounds of boost from the time tha the bypass closes (WOT) to redline, with out having to wait for it to spool up. The main advantage of turbos, is it uses wasted energy to make power, while the supercharger uses power from the crank to make more power. The supercharger also draws on the power of the engine some even when not in use. Obviously there are many other opinions on what makes one better then the other. These depates have been going on ever since man descovered more power can be made by forcing more air into the car.

Milage
 

How is your SC on milage?

I get about 20mpg but I realized today finally where my air leak is comming from so that should change soon

Tom

I havent computed it out. But you cant really go by mine and TomSVX's mileage. We're both running JDM 6-speed trannies. Our gear ratios hurt our mileage worse then the S/C ever could.

Putting the whole supercharger vs turbo debate away....


The answer to your question is you need to build the engine. It's not just a matter of the compression either it's the cams. The engine is very over square and wants to make power at high rpms. The factory cams are set to make power at low rpms. The math works out to it being silly to use forced induction without cams. As the engines are old and the pistons are weak to being with combined with the compression ratio is far from ideal for forced induction and the factory oil clearances ranges are unacceptable for performance applications...you need to do the bottom end too. The bottom line is...build the engine first...then supercharge or turbo. If you build the engine right you should see big power from either method of forced induction.

To the what turbo to use question... the answer is for a single turbo use a garrett gt35r. For twins use garret gt2871's. Neither of those set ups have been used to date but I think all 3 of the turbo svx builders thus far would aggree that they would rather have those turbos if they had the $$ and/or didn't already buy what they bought.

I wouldn't try to supercharge myself. I'm the guy who fabricated the blower systems to date and I can tell you the clearances are TIGHT. The job is difficult enough to make whoever is foolish enough to take on the task cry before they are done.

I may offer another supercharger "kit" in the future but then I may not. I wouldn't do it the way I have in the past again. I have a large cnc machining center now and can make production runs of the parts but instead of trying to fight the loosing battle of fitting it under the stock hood I would make aftercooled systems that would perform like the living daylight but require you to get a fiberglass hooed and make a bump/scoop/cowl induction type design to give the necessary clearance. As far as that is concerned..unless by some miracle people start throwing $$$$ at me out of nowhere you will just have to wait and see what I do with my car and whatever I do will be made available for everyone else. I'm up in the air between twin turbos and an after cooled whipple at this point.

Cam Power Peak Prediction
 

Some good points Mike. I think it is important for folks to know comming into this sort of project, what sort of costs to expect. Built engine, built or different transmission etc.

Do you have any predictions as to where the peak power will occur with the new cam grinds? I understand we won't really know until we tune, but I'm wondering if I will need to cheat my TCU to shift higher at WOT.

Twin Turbos!!!!!!:D