ok the short of it is i dyno'd at 194@8400rpms last year
i added a header and a snorkel. dyno'd slightly less yesterday mostly because the car stopped making power at 7600 rpm (186whp)after that it's level till 8k then drops off about 30hp.
the car didnt want to lean out after 7k. afrs start at 12.8 @7k rpm 12.1 @8k adn 11.6@8500. down to 11.0@8900 rpms, so, the tuner plugs in the emanage and gets to work, in the end he got the afr's around 13 @8300 and the power was up to 198@7600 peak tq was 135 ft lbs@7500but after that she still died down to 175hp.
the car is a MY00 and has 75k miles and in good running order, or so i thought.
any ideas to why i cant make power after 7500? the plugs looked fine the filter was clean, and i havent had any problems w/ the car has any one encountered anything like this before? any tips would be greatly appreciated

 

Maybe your fuel pump is dying out.

 

would that cause me to run that rich up top?
i was thinking along the lines of an ignition problem, im clueless..
thanks though.

 

best thing I can think of is to replace your plugs, or maybe one of your coil packs is giving up. an inability to recharge fast enough between sparks would be prevalent at higher rpms, and if your not igniting the fuel in 1 or more cylinders that would cause it to be expelled through the exhaust, showing a rich reading.

does it sound any different when the power starts to drop off. if its a missing spark the engine should stutter

 

where'd you dyno at shawn?

sounds like maybe the tuner wasnt creating a smooth AFR curve. fuel pump problems i doubt, ignition i doubt.

with your mods and a good tuner you should be damn close to 225whp easy. did he fiddle with the timing? bad tank of gas?

not leaning out is a tuner problem. your stock AFR progression is normal 12.1-11.6ish, thats the factory ECU richening the top en for saftey. if june at AIXOM tuned it then i can understand, cause when he tuned my vafc it did the exact same thing your talking about. 8k then the power hit the deck.

 

you should shoot for 13.5:1AFR at wot, that really optimal for our cars, especailly a MY01 like yourS.

 

My AFRS were almost identical with similar mods. VAFC II did the trick so far but I dynoed 206 on a mustang before the vafc II. I am getting a check engine light currently dont know why though. Possibly something with the VTEC Switchover.

 

Looks to me like the header and snorkel you added ("a header" and "a snorkel"?) aren't as good as the stock header and intake. Just a few posts down is a link to dyno results for a Spoon header. -3hp!

For tuning A/F, I'd start leanish and richen it until it just *starts* to cost hp, then go back to the previous slightly richer setting.
13.5 seems way lean, but I'm more used to triple sidedraft carbs than factory fuel injection!

I wonder if you'd be better off with a tune on the stock header and intake...

 

13.5 is on the leaner side, but still safe for the s2k. i had my car tuned at 13.9 and it loved it there.

the snorkel isnt hurting him, and i doubt the the 5z header is hurting im that much, i really think its the tuner.

 

I dunno, I read it that he made 194rwhp, then only made 186 with header and cai, presumably *before* tuning commenced. Seems most likely to me that the mods hurt high-rpm airflow, further enrichening the already rich stock mixture. Less air + even more rich = less power.

I'd be interested to see how the tune developed for the mods works with the stock intake and header. If the mixture goes leaner, and power doesn't fall off, or shows gains, no doubt stock config is better.

At the *very* least I'd back-to-back dyno with the header and CAI vs. header and stock intake.