cliffyk

78 mm is too big, though as I said above it will only have noticeable negative effect on the last 750 to 1000 rpm, between peak HP and the rev-limiter--which most people never use anyway. 70 mm is the optimal combination of air flow and charge velocity for the PI engines.

Any aftermarket plenum, except possibly the Dragon unit, will flow all the air an n/a 2V could ever need--I have Pro Product's 70 mm TB and plenum--they are the same as the Trick Flow branded parts:



You should do a few dyno pulls at your current level to get a baseline from which to gauge future mods--I have had my '03 on the rollers five times since I bought it in December of 2006 (Pearl Harbor Day actually), that is in part why I know what works and what doesn't.

If you do dyno it, and you still have the stock intake, do a couple back-to-back runs with the aftermarket CAI and the stock CAI--I think you will be surprised by the results, and if optimised power is your true goal (as opposed to underhood flash and bragging rights) end up keeping the stock intake...

'02gtgarrett

so buy tuner,then tb/plenum and i should be good for 245rwhp. sweet. question about the tuner: I will definately not be able to run a 93 octance since i am a broke high school student with gas prices going up constantly around here so can i get a decent 87 octance tune that will give me some good power to it?

cliffyk

Running 87 octane capable tune will cost 7 to 10 peak rwHp and reduce mid-range gains, versus a tune optimised for 93 octane--look for around 235 rwHP with regular gas.

The difference is only $4.50 more for a fill-up from dead empty (15 gallons), based on current gasoline costs in Fayetteville--that's the difference between 87 octane at $3.40 a gallon vs. 93 octane at $3.70/gallon--or spending $55.50 for 93 versus $51 for 87.

Unless you drive a whole lot find someplace else to save the lousy $4.50 and enjoy the added HP...

'02gtgarrett

well i can try it. i'll see when i get the tuner. thanks man. you've really helped me out and educated me, lol.

'02gtgarrett

one more question. with all my mods i have right now plus a tune only, about how much HP would i gain?

cliffyk

You'll be up around 235 peak rwHP with an 87 octane capable tune.

This is the same peak HP as would be expected with a 70 mm TB and aftermarket upper plenum. The difference is that with the TB&P there will be some added power in the upper mid-range at WOT and the engine will pull strongly past peak HP, right out the the rev-limiter, rather than dropping off as with the stock TB&P.

It's still like trying to breathe through a straw, but it's a bigger straw.

You can get the tuner (BAMA's Free Tunes for Life is a good deal if you do not plan on doing your own tuning in the foreseeable future) now, there will be no need for retuning with the new TB&P as what they will do is just allow the engine to breath more freely, not change how much air the engine can ultimately ingest or how the incoming air is measured.

The MAF will still measure the actual amount of air entering the engine, including the additional mass flowing in because of the easier breathing, and the PCM will continue to calculate the injector pulse width based on the improved air flow as reported by the MAF...

'02gtgarrett

thanks. What about with a 93 octane tune?

cliffyk

These are all nothing but guesstimates, and without any idea of the condition of your engine, and in the absence of any baseline information, I think it best to stop the game at this point.

Do a baseline dyno run and let us know what the numbers are then there will be some basis for predicting the future. If you do not care to do a baseline run then you are not serious about "modding" your engine...

'02gtgarrett

alright. thanks.

TRUEBLUE3934

Cliffy also points out a very important point that many guys miss!
You should NOT simply look at peak numbers to assess mod effectiveness. It is the area under the power curve that is most important. I'll take 10hp gain all the way across the power curve in place of 15 at peak anytime.

Many mods make claims of power gains that are actually somewhere other than at peak. This is one reason that people bash an advertised claim. Because they did not use critical thinking when reading the advertisement. Did it say that you will gain 12hp at peak? Maybe you did in fact gain 12hp at 2900rpm, but only 5 at peak rpm. Ads may also claim up to 12hp gain. This may be correct for a modified motor, but not for a stock motor. You get what I'm saying...

True gains from a performance mod are really best measured at the track and not on the dyno.