View Full Version : Power Levels> What Do You Think???

02-23-2006, 07:30 PM
Ok here we go. New STi block(EJ257), RS DOHC heads with a mild port job, 4 to 1 manifold, 3" catless exhaust, FMIC, STi VF39 turbo, STi injectors, aluminum crank pulley, Exedy flywheel. On pump gas, 91 octane. I'm wanting at least 350 crank hp. I'm pondering methanol injection, but thats later. What kind of power does everyone think I could put down with this combo? What kind of boost levels? What would be the weak link? Just want to see what everyone thinks. Thanks!!

02-23-2006, 08:52 PM
Get the RS SOHC heads. They are the best flowing by far.

If you want 350 chp then I'd recommend a different turbo. The VF39 really isn't very big.

gator gt
02-23-2006, 09:00 PM
I'm not a genius when it comes to tuning and forecasting power output....but I can see some weaknesses in your setup already.

1. Don't forget the Walbro fuel pump. You'll need it. You WON'T achieve those power levels without an upgraded pump.

2. Why waste your time and money with RS heads....go straight to WRX heads at least. Get them PnP and then put them on the EJ257.

3. With the FMIC, you'll get a touch more lag than a usual outta the box STi (regardless of the AVCS). Cause you'll have to push that much more air through the system before it gets smashed into your cylinders.

4. Like 92-22 said, skip the OEM turbo....you want 350 hp, shoot for an AVO400.

5. Think about an external wastegate setup. You can tune it more aggresively with that setup.

6. I wouldn't waste your money on a crank pulley.

7. Think about the proper clutch to handle that power too.

8. Ideas on the exhaust mani? You're not thinking custom, are you?

92-22: RS heads better than WRX heads?


02-23-2006, 09:11 PM
Well a lot of the parts I already have on my car now, the manifold and exhaust, fuel pump, clutch, crank pulley. The heads are rebuilt, brand new. If they really are that bad I guess I could sell them. I already have a TMIC from a WRX, but I figured a FMIC would be more benificial for the power I want to make. How much HP will a VF39 hold? I heard they are good from 350 to 400HP, If it wouldn't be worth it I guess I could sell it too. I really don't want to mess with an external wastegate. I already have a good 4to1 manifold and 3" DP and I don't want to cut them up. What about the injectors??

02-23-2006, 09:16 PM
This is the setup I have been running for about a year and a half. It just died recently. Time for a better setup.


gator gt
02-23-2006, 10:31 PM
I'm waiting for 92-22 to chime in on his opinion on heads.

Get the pink STi injectors...you should be fine. Any step higher, you're looking at Nismo 750cc (with modded wiring on your engine harness) or Power Enterprise injectors. $$$

I'm not sure about the limit on the 39. But, I'm constantly seeing it for sale on NASIOC. Why do rats leave a ship?


02-23-2006, 10:40 PM
92-22: RS heads better than WRX heads?


Yes, by quite a bit IIRC. I don't remember the exact numbers but I should be able to find them. It seems like the SOHC RS heads flowed 40cfm higher, or around there.

Since gator brought up some very good points I'll expand apon it too.

If you're going to do 350chp then you'll need a built tranny (big $). Trust me, I know.

You're going to need SEM too, if you're going to be tuning. That's additional sensors, gauges, wiring ect.....skillz, or dyno time.

Not 100% sure about the injectors but I'd get solid info before committing to them. Maybe a RRFPR could be a band aid, if they are too small.

Brakes and suspension are crucial. Especially brakes.

02-23-2006, 10:56 PM
One thing though. The WRX heads ( We're talking EJ205 ?) will be set up for the turbo where as the RS heads won't. With RS heads you'll need a custom coolant return line and oil feed line. Teh N/A heads aren't setup for them. Guys say it's an easy thing to overcome but it takes some fab work.

What I said about needing a built tranny. You might be ok for a short while and have some fun but it won't last. It'll break. Start planning for a tranny now so you can be ready.

gator gt
02-24-2006, 01:20 PM
:lol: Matt, I thought this was a motor thread....if he wanted to know how to build a proper monster, I could have expanded my own thread too. :lol:

Interesting about the SOHC RS heads. But, like you mentioned, WRX heads are set for FI from the gates. I'm thinking a good PnP job could see some significant gains though from the EJ205 heads.

And yes, 205....1-bad-legacy doesn't seem to have an endless budget, so I was sparing him the 257 or 207 heads and applicable costs/fab/wiring that go along with those.

And yes, if nothing else, look at upgrading your brakes if you're upping your power levels. What goes, must stop...one way or another.


02-24-2006, 03:29 PM
If you plan on using SOHC heads, you might get better performance if you went to Cobb or TWE or a similar company and bought FI cams for the heads. Then you could get FI performance with good flow.