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View Full Version : +20s/+40s on a stock head



Dave
03-31-2006, 05:41 PM
I know there's a good debate between whether +40s will even help on a stock head due to the fact that the head's ports are so small that you can't really get the air in, so the extra fuel between the 20s and 40s wont help, because you can't physically fit the volume. Is this true?

I'm debating whether or not to get the 40s or 20s because of this. I wont be pulling the head until Fall when I can afford a hybrid, or if the headgasket blows, whichever comes first.

This means I wont be porting the head until I have a reason to pull the head.

Thanks.

89DaytonaTII
03-31-2006, 06:17 PM
What a bunch of bs. You can make more power on a stock head than +20's can supply fuel for.

Although for a mild setup still using the stock turbo/IC the +20's will cover what they can dish out.

iTurbo
03-31-2006, 06:37 PM
How much WHP are +20s good for? I'm running the +20s with a stock TII calibration.....stock TII engine and 3" exhaust. Sometimes I wonder if I'm asking too much of them.

inmyshadow
03-31-2006, 06:44 PM
I'm running +40s on stock swirl port head running 20lbs of boost right now.

Last year I was using my rebuilt swirl port head with some flow work. Same setup.

iTurbo
03-31-2006, 06:48 PM
I'm also running 20 psi right now on the stock swirl port head. With the +20s, I run 55 psi base fuel pressure. The head/cam/turbo/intercooler are stock TII. I do have a narrow-band A/F gauge, but it is practically worthless. Am I nearing the limit of +20s?

turbovanmanČ
03-31-2006, 08:50 PM
iTurbo, your guages will tell you if your lean, then if your lean at WOT, you've gone too far.

Bryan, your looking at it wrong, you need to look at what your expecting. If you want 300-350 whp, then go +40's, if less, go +20's etc. The turbo dictates injector size, then the cal tuner can tell you what injectors to run. Sure a ported head helps but its not the be all.

Dave
04-01-2006, 12:26 PM
iTurbo, your guages will tell you if your lean, then if your lean at WOT, you've gone too far.

Bryan, your looking at it wrong, you need to look at what your expecting. If you want 300-350 whp, then go +40's, if less, go +20's etc. The turbo dictates injector size, then the cal tuner can tell you what injectors to run. Sure a ported head helps but its not the be all.

I'm just looking to run 18-20psi once I upgrade my intercooler to the Mishimoto and +20's. That should net me around 260-275WHP.

iTurbo
04-03-2006, 03:50 PM
Are +20s good for 275 WHP with no other fuel supplement (5 injector, alcohol, wet N20 system etc..) I have +20s in my Omni which has a stock 2.5L T1 (no balance shafts), 3" exhaust, big NPR, TII turbo.....Hoping for about 250 WHP with 20 psi.

turbovanmanČ
04-03-2006, 04:21 PM
Are +20s good for 275 WHP with no other fuel supplement (5 injector, alcohol, wet N20 system etc..) I have +20s in my Omni which has a stock 2.5L T1 (no balance shafts), 3" exhaust, big NPR, TII turbo.....Hoping for about 250 WHP with 20 psi.

You should be ok, I layed down 236.5 whp with lots of fuel to go, :D

Dave
04-05-2006, 08:31 AM
You should be ok, I layed down 236.5 whp with lots of fuel to go, :D

Simon, what was all done to yours at the time??

So what Im getting here, run the +40's, eh? Just concerned about mass volume being achieved to use the fuel.

turbovanmanČ
04-05-2006, 11:02 AM
Simon, what was all done to yours at the time??

So what Im getting here, run the +40's, eh? Just concerned about mass volume being achieved to use the fuel.

If you plan on going big, IE big turbo and big boost, get the +40's. If your keeping it close to stock or mildly done, get the +20's.

At the time, stock exhaust manny, one piece intake, 52mm t/b, stock cal, 3 inch ex with DP, mandrel bent, no cat, 3 chamber Flowmaster, RX7 IC, stock T1 cam and my CAI setup. Head was just cleaned up, a bit of grinding and backcut valves.

Dave
04-06-2006, 08:32 AM
I'm planning on staying with the stock Garrett for the summer, but after I buy the Dawe's Device gauge and my pizza rims I will be investing in a Mishimoto intercooler and 2.5" i/c piping.

Are the 20's a reasonable estimate of fuel needs? I only want 18 or 19psi. I want my stock bottom end to last for the rest of the season.

turbovanmanČ
04-06-2006, 11:56 AM
Bryan, +20's are more than adequate for your needs.

Dave
04-07-2006, 08:23 AM
K thanks. :D