Boostaholic

iTrader: (4)

And had a intresting problem. The car won't rev past 5500 and stay clean, it will go past but it stumbles and the logs show it going up and down in rpm but slowly up.

AFRs were 10.5-11.2, I was kind of focusing on the RPM problem more than making the AFRs perfect, had 17deg timing and saw almost 9psi of boost.

Made 540 / 557 and 512 / 601, very disapointing numbers but the power is still going way up when it hits our problem RPM so I think once I get that resolved things will go better.

LTLHOMER had the same problem on his car and it was a crank pickup wheel issue, but if anyone has suggestions on things to try before that let me know!

Frost

iTrader: (45)

Valve float?

DERTY

Sounds exactly like the LTLHOMER / PSJ crank signal issue.

LTLHOMER

iTrader: (10)

Did you have the cam sync override on or off? If you have it off (aka won't override) it should hit the certain rpm, resync itself, and then hit it again and again almost like a rev limiter. Mine was on so it would just hit the certain rpm, lose cam sync and die.

Boostaholic

iTrader: (4)

Mine was off

LTLHOMER

iTrader: (10)

Any video? Or any logs?

LTLHOMER@aol.com

The a/f wouldn't be the cause...I've run mine from 9.5 to 12.5 and it rpm's exactly the same.

Boostaholic

iTrader: (4)

Didn't have a camera, but I have all the logs

LTLHOMER

iTrader: (10)

Send 'em this way.

Pro Stock John

iTrader: (34)

Plug gap?
Type of coils?
BS3?
Cam
Valvesprings, open & closed spring pressure?
Stock pcm gone?

Boostaholic

iTrader: (4)

Gap : TR6 @ 30
Coils : Stock
BS3 : Yes
Cam : Small
Springs : Huge
Pcm : Gone

Pro Stock John

iTrader: (34)

My blower setup was:

Gap : TR8 @ 25-30
Coils : Truck Coiols
BS3 : Yes
Cam : Big
Springs : Comp 977's so on the big side
Pcm : Gone

LTLHOMER

iTrader: (10)

Send those logs over. LTLHOMER@aol.com

Boostaholic

iTrader: (4)

I'll have to buy a USB flash drive, my laptop sucks really really bad.

MIGHTYMOUSE

iTrader: (59)

ltlhomer, can you describe in more detail the cam sync error, what happens when the error reports on a log, and what the cam sync override does, and what the car should do when you select override?

i was talking to john about this myself last night cuz i get a backfire now and then, he had me check to log cam sync error and it is hitting when i get the backfire. so he mentioned to try selecting the synch override or advancing the cam?

my chain was more slack than i thought it would be when i changed cams last week also fwiw

MIGHTYMOUSE

iTrader: (59)

also, what did your external crank sensor have to do with correcting cam synch error?

LTLHOMER

iTrader: (10)

In my case, it was losing crank signal so without signals from both cam and crank, it has no idea where it's at. It would literally disappear at like 6500 rpm's when John put it on the oscilloscope. From what I understand, the cam is telling it when it is on the compression stroke of cylinder 1 (hence why it only has one tooth), and the crank signal is responsible for telling it everywhere between that stroke and the stroke 2 crank revolutions later. If it loses sync it will do one of two things:

If cam sync override is on, it will continue as if the cam sync was not lost so if cam sync really wasn't lost, it would continue on its merry way. I've heard of a few instances of this...has to do with how close the falling edge of the cam and crank sensors are to eachother (COP value). If cam sync was lost, it will be off 15 degrees per tooth it missed and eventually just shut down since it will be adding fuel and sparking somewhere it's not supposed to be (that's what mine did). This is why John was asking about you advancing the cam because that will increase the angle between the cam and crank falling edges.

If cam sync override is off, it will rev down a little from the rpm where it loses sync in order for it to resync itself, and then either keep hitting that same point and repeating or just rev through that point without issue. That's what mine did when we turned it off...it would hit 6700, come down to 6300 or so, and go back up like a rev limiter.

I can go into more depth when I get back from my interview, but that's the 2-minute version and probably has some mistakes.

As far as the log goes, if you log cam sync, you can see a spike in the graph when it loses sync. It will go back to zero when it resyncs itself and usually takes <0.10 seconds. If you send me your logs I can take a look since I've seen pretty much everything in relation to the cam sync stuff.

LTLHOMER

iTrader: (10)

Yeh it sounds like a backfire when it loses sync...mine does it once in awhile even now but we are working on using a different crank trigger and wheel setup...but it's close to perfect which isn't bad for just throwing something on there.

Boostaholic

iTrader: (4)

I do not get any backfiring, it just won't rev higher or revs slowly

67Firebird455

iTrader: (27)

That is nuts... I am curious to see what it is... I know the backfire he's referring to... Strange that it revs slowly. What is the timing like on the log?

Boostaholic

iTrader: (4)

18deg