Had to pull a lot of timing, normal for LS7?

[HinesPerf]

I'm tuning my first LS7 in a 2011 Corvette and it seems I had to pull quite a bit of timing to eliminate all the knock retard. It's has the following engine mods and is running 93 octane fuel,

• Heads milled 0.024"
• Cam: 235/242 0.621 0.638 113 LSA +4 degree advanced
• Long Tube headers, 3" exhaust with no cats

Here is a diff on the timing table from the stock tune, you can see a lot of timing was pulled. Is this typical for these mods on an LS7? I've tuned LS2's and LS3's with identical mods but didn't have to pull near as much timing.TimingReduction.PNG

[Kyne]

That's a lot, are you sure it's real knock? I've only seen the ls7 need one or two degrees pulled anywhere NA.

[MikeOD]

That's brutal...it's probably making no power. Is the AFR correct? Is there a mechanical issue with the mods done?

[HinesPerf]

That's a lot, are you sure it's real knock? I've only seen the ls7 need one or two degrees pulled anywhere NA.

It looks like real knock....here's a shot of the KR histogram from the first pull.
KnockRetard.PNG

[SSUte01]

Burst Knock Retard or Knock Retard? Also Gen4 knock sensors are notoriously over sensitive in many cases.

[edcmat-l1]

I never mill the heads on the LS7s. It's counter productive. Causes lots of knock and the need to pull timing almost everywhere. Depending what the knock sensor settings are, if you have any audible knock down low, and what the final timing actually is, it could be about right, or could be you pulled a little too much. Either way, you're going to end up pulling some.

[edcmat-l1]

Post the tune so I can see how you have the knock sensors setup, and what the timing tables look like.

[LSxpwrdZ]

Octane limited....

Be carefull cause the LS7 pistons are brittle.

[HinesPerf]

Post the tune so I can see how you have the knock sensors setup, and what the timing tables look like.

Here's where I ended up with the tune.

[HinesPerf]

Octane limited....

Be carefull cause the LS7 pistons are brittle.

Yes, indeed. I'm surprised milling just 0.024" made such a difference.

[SultanHassanMasTuning]

in my experience LS7's do not take timing very well. 90oct here!

[edcmat-l1]

There's a few things you can do to get some more timing in that thing. Soften the knock sensors, zero the AFR correction, etc. At that compression, on 93, you should be able to run 19-20 degrees safely.

[HinesPerf]

So, I took the car down to Sunoco and filled it with GT 260. Is it normal for that fuel to completely trash your fuel trims?

[Midnite Magic]

So, I took the car down to Sunoco and filled it with GT 260. Is it normal for that fuel to completely trash your fuel trims?

Sunoco racing fuel will have a different Stoich point then pump gas 93 octane

[HinesPerf]

Sunoco racing fuel will have a different Stoich point then pump gas 93 octane

You're right sir....14.6 to be exact. http://www.racegas.com/fuel/8

[LSxpwrdZ]

Yes and it'll also cause them to read a little funny with fuels containing lead.

[GrannySShifting]

Ed and other guys, have you had LS7 only take 18 degrees, stock with a mild cam (230s) unmilled, just headers/cam. Made 537, but would not take any timing

[LSxpwrdZ]

I have yes. I have one with a rather large cam with milled heads on Q16 that makes peak power w/ 23* @ peak torque and 24.5-25* @ redline. Q16 will not detonate on this engine NA but made less power with more than this timing. So on pump with smaller cam's I can see low amounts of timing to keep them happy.

They still make great power with less timing. In the end it's just a number, give it what it likes!

[edcmat-l1]

Ed and other guys, have you had LS7 only take 18 degrees, stock with a mild cam (230s) unmilled, just headers/cam. Made 537, but would not take any timing

That's pretty damn low for stock compression. Are you going by KR or is it audible? Or showing other signs of being real knock? Did you read the plugs? Any signs of detonation on the plugs? What's the A/F?

[GrannySShifting]

Just KR on logs... not sure if it was real or BS. never got into it enough, just put it together, spent hour on dyno, and the car has been sitting since. Shit to loud to be audible! Need knock box or stethoscope and lotsa tube AF was mid 12s if I remember right. Thing was trying to make a bunch of torque I think, had 2" headers on it... and it was still 40 ft lbs above other cammed Z06s with normal 1 7/8 type headers at 3500-4000 rpm.