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ZQQH6
09-07-2010, 07:56pm
What do y'all think? I put on 3,135 miles Carlisle and back to TX last week. On the way back I was experiecing some light detonation on upgrades and some pedal nudging while crusing on the highway @ 75mph. Is the timing too far advanced? Fuel needs richened O2 sensors slow. I put on heads and 92/90 intake last winter first real drive since tuned. All fuel from brand names. 11:01 compression. This al in 6th gear downed to 5th and was good.
No tuning for me, doing good just posting.

Y2Kvert4me
09-07-2010, 08:42pm
Is it cammed? How big? And if I may ask, who tuned it?

I've "fixed" a couple tunes from big name vendors where timing was insanely advanced in the table cells you'd normally hit during low-RPM cruising like you describe.

I know some tuners do this in attempt to minimize the cam surge effect, but (for a real example) seeing 38 advance at cruise is just a bit excessive, and increasing the load (cruising up a slight grade) would induce KR every time.

:cheers:

ZQQH6
09-08-2010, 05:50am
A cam for sure. Been in the motor for years. Its a LG G5x1 228/230 on 112.
Tuned by a guy that broke off from 21st Century Muscle Cars Texas- Lingenfelter. I get surge at fast stops now too. Hunts up and down. Never did that before either. I think he put timming @ 28* I got the SVO 30# injectors and the cycles aren't maxed. WOT runs great just the cruise deal and the hunting. Will be going back like 3x now to remedy surge.

Y2Kvert4me
09-08-2010, 03:45pm
If 28 at that (low) RPM, that's not unreasonable at all. I just checked my current tune, and I'm right around 24-26 in the 1400, 1600, and 1800 RPM rows (the ballpark you'd be in cruising in 6th at 75).

The thing that strikes me, is that you mentioned it only started doing this on the way back, not on the way there. That tells me something physical changed, and it wouldn't be the timing to blame.

I'd be curious to know what your fuel trims and MAP are doing. With the idle hunting, it now almost sounds like it could be an (intake) air leak somewhere. The FASTs are well-known to be fussy in sealing up sometimes. What did you do for a fresh air source into the engine for PCV?

I hear ya on the return trips to the tuner, most just don't want to spend that kind of time on a car. It's easy to make the car run perfect on any given day, the challenge of tuning is making it run perfect on ALL days.


:cheers:

ZQQH6
09-08-2010, 08:37pm
I stuck a brass fitting into silcone coupler between air bridge a nd TB sealed it and tubed to valve cover. Nothing else changed on system.
The air leak has crossed my mine. I may take intake off and redo. I'll probly go back to tuner first and see if he can give input after he looks at program.

Y2Kvert4me
09-08-2010, 09:23pm
I stuck a brass fitting into silcone coupler between air bridge a nd TB sealed it and tubed to valve cover. Well done. :yesnod: (so many people overlook this).


I'll probly go back to tuner first and see if he can give input after he looks at program. I'd do that first too before tearing the manifold off.

Heck, just putting a wrench on the manifold bolts to check torque might be the first step. Those intake seals are rather thick, and as they compress over time with heat cycling, the manifold bolts tend to gradually become looser.

Short of that, a can of starting fluid sprayed around the manifold-to-head area with the engine idling works well at detecting air leaks. Just be careful with it.

:cheers: