Derect Scan- LV8 and inj.pw. problem.

[Quicksilver]

I ran the car at Norwalk this past weekend, using Derect Scan for the first time. I got a new best time, but...I developed a popping at the two three shift that drives the LV8 from 255 to 40 and a frame or two later the inj,pw. drops 153% to 48%. Each time the rpm drops 100-150. It is like this for only 2-3 frames@18fps.
24 PSI, 22 deg. timing, VP C116. Anyone got some suggestions as to what is causing this?
.. Had to move the seat forward to reach the steering wheel during the 1.55 60 ft.

 

[TurboDave]

Sounds like the dreaded "MAF droppout" problem. I'd bet that if you look at the MAF trace you'll see it "dropping out" also. Since LV8 and inj. pw. is driven by the MAF (among other things), that's the reason they're dropping out and you're getting those lean pops.

Since you're driving the injectors so incredibly hard and way past static, I'd have to assume the engine is also drawing way way more air than 255 grams, and the MAF buffer is hitting overflow resets.

 

[Quicksilver]

Thanks Dave, The MAF is solid 255 from start to finish. I even swapped in a known good senser from a friend with the same result.
The o2 volts vary from .8 to .753 with one frame at .695 following the LV8 drop. I understood this range to be ok, Is it not?
I had also changed plugs and installed new wires at the track to correct the poping .
And lastly, I've got 43 lb. injecters. I will try more pressure as they should not be static at my hp level. Do you agree ?

 

[kenmosher]

You might also want to try a run without DS connected (all cables, including the one to the edge connector). See if it happens again.... if not, then start looking for a shielding problem in the DS hookup.

 

[Quicksilver]

Thanks Ken, But I borrowed Derect scan to help track down my gremlins do to my OTC 's slower update time.

 

[TurboDave]

Originally posted by Quicksilver
Thanks Dave, The MAF is solid 255 from start to finish. I even swapped in a known good senser from a friend with the same result.
The o2 volts vary from .8 to .753 with one frame at .695 following the LV8 drop. I understood this range to be ok, Is it not?
I had also changed plugs and installed new wires at the track to correct the poping .
And lastly, I've got 43 lb. injecters. I will try more pressure as they should not be static at my hp level. Do you agree ?

Ummm, are you by chance running a chip with a MAF lock patch?? The reason I ask is, that it's my understanding from some experts, that even though such a patch is installed, and you see no MAF dropouts, it still doesn't prevent the problem.

There's little else that can cause LV8 and injector dropouts like that other than MAF buffer overload/dropouts.

 

[Quicksilver]

I was running a RA 106 chip. Forgive my ignorance, I am unaware of such technicalities.

 

[TurboBob]

To me it sounds exactly like MAF dropouts.

It might help a little to unplug the cam sensor before your run (engine running).

Otherwise, a MAF-locked chip will fix it.

TurboBob

 

[Quicksilver]

MAF dropout

Gentlemen, thank you for your assistance. I will investigate.

 

[TurboDave]

Originally posted by TurboBob
To me it sounds exactly like MAF dropouts.

It might help a little to unplug the cam sensor before your run (engine running).

Otherwise, a MAF-locked chip will fix it.

TurboBob

Thanks Bob, I couldn't remember which of the patches I was thinking would make it appear to fix a problem but really wouldn't. Musta been one of the others.