Beginning about the time I put on the UDP, I noticed a power loss in the upper rpm band. You can see from my dynos - I lost 13 whp after addition of the UDP.

Finally got a chance to test it at the track.

I have previously consistently run sub 15s with crappy 60' times at about 95-96 mph.

Saturday at the track, the best I ran WITH A 2.194 60' time - was 15.06 at 91mph. Pitiful. With a 2.194, I shoulda been at least 14.7. Trap speed shoulda been around 95-96. SO. . .

I TOOK OFF THE UDP on Sunday. Guess what - I still have the same problem. Car feels flat from about 5800-redline. So, something else is the culprit - I think.

Mechanic suggested the fuel filter - but it is in the trunk and supposed to be maint. free.

I previously had a problem with stalling/wanting to stall after hard acceleration followed by clutching and braking. I thought I had fixed it when I took off my intake and cleaned the filter, since it seemed to disappear. But after resetting my ECU last night - its baaack. I'm thinking its related.

So far, the only things I can think of are:
faulty intake runner changeover - see my dyno below - power falls off beginning at intake runner changeover.

fuel filter

the non-nissan gas cap I have

02 Sensor

anyone have any guesses? I'm going to redyno to confirm

 

It could be your spark plugs, or the ignition.

 

Maybe bad coils?

Is your ECU throwing an error code?

 

Yeah it might be some bad coils , never had this problem thoe.

Try resetting the ECU.

 

Kev - I'm not sure. I'm not getting a check engine light.

Is there an easy way to read/analyze codes. Does the deal where you stick a paper clip in two holes and read the service engine soon light flashing work with the max?

But, if its coils wouldn't it happen throughout the rpm range rather than just at high rpms.

 

Bad O2's would definitely throw some sort of code. From what I gathered, faulty coils won't throw a code.

The flashing thingy won't work on our cars because we don't have that screw to adjust.

I don't know the answer to the your last paragraph. No one has dyno'ed to confirm, but I'm assuming that faulty coils will affect your whole rpm range.

Did you accidentally disconnect a vacuum hose to your intake runners?

 

John-

Thats also the first thing that popped into my head when I started thinking about it yesterday.

When you redynoed last time, did you use the wideband O2? If so, youll have the A/F ratio data which might help determine the cause of this problem.

 

I've heard of an overly sensitive knock sensor retarding timing on the top-end. You won't necessarily hear knocking, but it affects performance. A dyno should show this if you don't have it "smoothed" too much.

One CRUDE test is to dump in a bottle of 104+ Octane Booster(Outlaw?) and see if it makes a difference.

You should invest in a scan tool/labtop and you might be able to diagnose it easier.

 

coils? I got new ones from Dave B... need to install them sometime...

 

Check your MAFS and also check to see if your throttle body is clean.

 

Yeah, I have the O2 info. John did it when I dyno'd after adding the UDP (you were there). Whada you think??

http://web.tampabay.rr.com/maxgator/airfuel.BMP

 

One thing you can do is measure your fuel pressure. Since you said the 2k max fuel filter is in the tank and isn't serviceable it would make measuring fuel pressure harder. If you can find a rubber fuel hose that runs into the fuel line then you can hook a gauge that reads the fuel pressure. Other suspects would be the knock sensor and crank/cam angle sensors.

 

Guess its something the dealer is going to have to look at.