never fails. under WOT at exactly 5000 rpms i get a "detonation" sounding bang and a full out loss of power to the car where half a second later the engine catches itself and revs up once again. it was constant on the dyno and is constant at the track. only happens under WOT.
i do not have an auto tap so i do not know if this is knock retard. my question is could it be caused by not having enough fuel to accomodate the air from the headwork? i also have an air lid and a cold air induction, but still the stock fuel pump. would my engine benefit from an aftermarket fuel pump? or am i thinking totaly wrong?

i do have the maft+ and have richened up the fuel a bit, but that doesnt seem to help.

any ideas?

 

ok the guy who did the porting and polishing said that i need to wide band dyno, but at the dyno, it messes up at 5000 rpms and the dyno is worthless.
any suggestions???

 

Give us a little more info about the engine, and what you are using to control it. Have you retained a knock sensor?

Maybe that info is in you link, but you will have a better chance of getting an answer if you post the relevant data.

 

Without the ability to log data, there are various things that could be at fault. Is there no way for you to log?

 

i will finally have a chance to auto-tap my car feb 15th. this is what i plan on checking:1. Long term fuel trim Banks 1 and 2
2. Short term fuel trim Banks 1 and 2
3. Bank 1 Sensor 1 HEGO
4. Bank 2 Sensor 1 HEGO
5. RPM
6. Ign timing
7. TPS
8. Mass air flow
9. IAT
10. ECT
11. IAC %
12. Misfires

i know i show misfires left and right but that is from the cam i am sure.

the engine itself is the all mighty L36 in a 2000 V6 camaro. when i first had the port and polish work and cam put in i ran an all time best of 14.45 at 94 mph. i did not have the maft+ at that time. but then everytime i went back to the track the times got progresively worse- even with the maft+. i then found out that i had a broken valve guide and no wonder my times are crappy. had that fixed, and at the same time put in some 3.73s and hooked up a HPP3. still times are crappy.
i disconnected the maf part of the maft+ and the knock seemed to go away. others have told me that when the maft+ was connected their cars where reading some awefull knock. maybe just maybe when i can a-tap my car i will find out just what is happening.

 

You need a "cell #" column to identify which fuel correction cell the long term corrections are coming from.

You need to add manifold absolute pressure (MAP), corresponding barometric pressure (BAR), and add MPH if you are logging while driving.

When logging anything, only use one parameter.... e.g. for throttle position (TPS) you can log TPS voltage or TPS%. Once you have established that your TPS sensor voltage correctly converts to TPS%, you don't need both. You can see either % long term fuel corrections, or the absolute number... e.g. 128... but you don't need both. I prefer the absolute number.

Add injector pulse widths.

Add spark timing retard.

After I took the time to go to your page, my first thought was the "+" part (spark timing) of the MAFT+. Have you established that the GMC3800 tuning you are using isn't already overloading the ignition timing with enough timing advance, to the extent that any alteration from the MAFT+ could result in a huge amount of timing overload... maybe more than the PCM can even pull? If you "hear" detonation, you may have that condition, and the PCM is just going to max retard, which would appear as a serious (but not "full") power loss. IMHO, you are always at risk when you start trying to tune with something like the MAFT+, AND a reprogram..... there may be somehting in there that isn't compatible.

Have you asked the outfit that supplied the GM3800 tuning for their opinion on your problem?

 

thank you guys.
turns out the knock sensor was picking up knock. 4-5 degrees while cruising and 14-18 degrees while under load. had that bypassed and now none is picked up on the scanner.
have now added a fuel pressure regulator and upped the pressure.
now it seems that i am floating valves. #1 was missing while driving normally and it was found to be the valve. ( had the spark plug changed, wire changed, injector changed)

but now #5 is missing under load. i was told to shim all the rocker arms just to be safe.

so now another question. where can i buy valve shims? my mechanic said a box of .015" valve spring shims would work. he gave me a thicker spring shim and said that would work also, but with a smaller diameter. does anybody know where i can buy .015 valve spring shims?

thanks,

nino