Here's something a little weird. I got my car tuned (HOndata with 720's) and 15 PSI on a 60 AR 57 Trim compressor. It was tuned at about 11.5:1 across the board from 3800 on. (4th gear pull)


A little low, I know, but I have a very restrictive exhaust.

Here's where it gets weird. If I'm on the HWY, and roll into 3rd, I get no detonation, shift 4th, all good. Or if I'm in 4th and lay into it, no detonation.

But, if I go from a dead stop, once I'm in 3rd, I can hear det, and then again in 4th. Wideband reads 10.8-11.4 throughout the run (on video). So it's definitely no a lean condition.

I have an MSD 6T ignition with a blaster 2 coil. MSD Cap, brand new OEM wires and brand new BCPR7ES plugs.

I also noticed my tach gets jumpy at high RPM - ignitor likely on its way out. Could this also cause mis-fire/pre-det issues?

I really don't want to blow up my Bensons sleeved LS/VTEC.

It just makes no sense that it detonates when I go from a stop once I hit 3rd, but never does if I roll onto the gas while already moving.....

Thanks in advance guys!

 

Throtal tip in maybe? The only reason I say this, is because you said you are "rolling" into the throtal on the HWY, but not from a stop.

Have you checked the plugs to see if there is evidence of detonation, and if the timing is good?

 

ttt

 

Hmm Todd do a launch and let it datanate then pull over and check ur plugs.

U sure its detonation tho?

 

Don't really like the idea of pulling plugs when the motor is that hot, last thing I need is fubarred threads

 

if they aren't overtorqued you won't have a problem. Everybody pulls plugs while there hot.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Turboteggy &raquo;</TD></TR><TR><TD CLASS="quote">Don't really like the idea of pulling plugs when the motor is that hot, last thing I need is fubarred threads</TD></TR></TABLE>

Pulling plugs when hot is no problem, just use copper anti-seize on the threads.... available at auto parts stores for like $5-$10

 

look to timing rather than mixiture and ask someone who knows about tuning

 

Are you sure it's not misfiring or something?

 

first, id ask your tuner what ignition timing you are running at that given PSI, secondly did he make sure to check your base timing at the crank pulley. next look at your plugs, if they have white specs, they are surely detonating.

but, from what u are saying, w/ the tach jumping, it sounds more like a misfire to me, but whatever it is, address it, dont keep raggin on the motor incase it is detonation/knock

also check ur gap when u check the plugs....i usually like to run .26-.28 unless its high HP

 

the dyno day was 3 weeks ago. Base timing was checked before the tuning began. perfect. I never asked him where the timing was set through boost, something to look at aI guess. I'm gonna be replacing the dizzy shortly, I know it's on its way out.

Thanks for the comment guys.....

It's still a mystery to me why it only occurs from a stop. i CAN do all the HWY pulls I want, and never hear this sound. Only from a stop, and only in 3rd and 4th (not brave enough to go to 5th yet)

 

Heatsoak. At low speeds the intercooler can't keep its cool. When your up to speed it can then start cooling, but it has to get rid of the heat is currently accepting and the heat that was added when you were in first and second gear.