[Doc Oc]

I know this is a long shot but was hoping someone had some ideas on a starting point. Got some disappointing dyno results last week but with no baselines I figured it'd be best to hit the strip before getting too worried. Did so recently and was unhappy to get trap speeds in the 113-14 range. 70 degree night, tank full of E, and mods in the sig w/fresh dyno tune. Logs show good afr (12.2 or so), good airflow (49 lbs/min) and timing up to 22 deg. It does feel like it's breaking up just a little in the upper rpms for which I plan a spark plug change (and gap down a bit) this weekend but I'm not really sure where else to look beyond that? Any help would be appreciated!

[Joshinator99]

Originally Posted by Doc Oc

I know this is a long shot but was hoping someone had some ideas on a starting point. Got some disappointing dyno results last week but with no baselines I figured it'd be best to hit the strip before getting too worried. Did so recently and was unhappy to get trap speeds in the 113-14 range. 70 degree night, tank full of E, and mods in the sig w/fresh dyno tune. Logs show good afr (12.2 or so), good airflow (49 lbs/min) and timing at about 18 deg. It does feel like it's breaking up just a little in the upper rpms for which I plan a spark plug change this weekend but I'm not really sure where else to look beyond that? Any help would be appreciated!

18 degrees of timing seems very conservative for a “tank full of E”, in my opinion...

[Doc Oc]

Sorry, was looking at my 93 logs. Timing hit 22 on the ethanol runs. Edited.

Also, just pulled the plugs (ngk ltr51x) and noticed that the ceramics were all very white (they've been in about 3k miles) which usually means it's pretty lean. Not sure where that fits but I expected a nice light tan color.

[BlackbeastSS2]

A good tune on pump 93 is 25 degrees with no knock. E85 average is probably set at 28 degrees of timing. Cooler thermostat and set the fans to come on earlier helps. 22 degrees of timing for you is robing you of power on E.

[KingLT1]

You are running Forced Induction timing and afr for E. NA should be 27-28 degrees of timing and 12.8-13.0 afr.

[Doc Oc]

Originally Posted by BlackbeastSS2

A good tune on pump 93 is 25 degrees with no knock. E85 average is probably set at 28 degrees of timing. Cooler thermostat and set the fans to come on earlier helps. 22 degrees of timing for you is robing you of power on E.

That's good to know. Our tuner said he could not get it to go above 20 (without knock) on the dyno (on 93). Definitely could be the issue. I'm in a bit of a sticky spot because I work part time at the performance shop where I dyno and the tuner is the owner of the shop. I have to be delicate in my approach to him, but it raised an eyebrow when he said he couldn't get it over 20 deg. I'm so new to the platform that I didn't push it but sounds like we definitely need to discuss.

[KingLT1]

Likely because the knock sensor thresholds have not been adjusted. These engines show knock bone stock and it's usually false.

[Doc Oc]

Originally Posted by KingLT1

Likely because the knock sensor thresholds have not been adjusted. These engines show knock bone stock and it's usually false.

Thanks man. I'm tuning illiterate but would like to be armed with as much info as possible for our discussion tomorrow. Is there a typical percentage that the thresholds are adjusted or how does it work? While I am at it, what causes false knock? Many threads here say headers can, but I'd think that wouldn't go away with timing reduction would it?

[gtfoxy]

Originally Posted by Doc Oc

Thanks man. I'm tuning illiterate but would like to be armed with as much info as possible for our discussion tomorrow. Is there a typical percentage that the thresholds are adjusted or how does it work? While I am at it, what causes false knock? Many threads here say headers can, but I'd think that wouldn't go away with timing reduction would it?

There’s a point in a mans life where he has to take his all encompassing destiny into his own hands, throw caution to the wind, sow his performance wild-oats, & tune his own shit, embracing the inevitable of success & failure, to become the king of your own internal combustion kingdom, be-it prince or pauper.

What gear did your boss run your dyne tune?

Remember, you can’t race a dyno.

Learn to read plugs, analyze sensor data. It’s all an individual part of a larger picture.

[BlackbeastSS2]

Originally Posted by KingLT1

Likely because the knock sensor thresholds have not been adjusted. These engines show knock bone stock and it's usually false.

That reminds me of my first tuner back in 2016 when it was all new to the tuners. There was nobody in my area yet that had done a LT1 GEN V. I found out later on my second tuner that the first guy turned off the knock sensor probably because he was unable to tune properly. So it’s important to chose your tuner wisely.

[Doc Oc]

Originally Posted by gtfoxy

There’s a point in a mans life where he has to take his all encompassing destiny into his own hands, throw caution to the wind, sow his performance wild-oats, & tune his own shit, embracing the inevitable of success & failure, to become the king of your own internal combustion kingdom, be-it prince or pauper.

What gear did your boss run your dyne tune?

Remember, you can’t race a dyno.

Learn to read plugs, analyze sensor data. It’s all an individual part of a larger picture.

Been thinking about that recently. Pretty scary endeavor but probably the best bet.

We dyno'd in 6, but the results of the dyno aren't as concerning to me as the low trap speeds...

[laynlo15]

I have almost identical mods on my C7 Vet and my total timing with 72 percent is 26.5. Most tuners run 4 more degrees of timing to the standard GM timing. You timing at 22 is what the factory should be on 93. Your not going to make good power with 12.2 AFR on E85 and 22 degrees of timing. Mine is 13.0 AFR and 26.5 degree of timing at the end of the pull which was 6350 rpms. Headers will sometimes show false knock. So I don't think you ever said what power it made. Do you have HP Tuners if not you should buy the MPVi2. You'll need it at some point plus you can learn to log and possibly at some point make small changes if need. There is a lot of info on line about learning to tune. Its taken me a few years but still need some assistance sometimes. Your tuner has something messed up if he can't get over 22 degrees of timing. I and most always dyno in 5th gear even though its not 1 to 1. Your MPH can get pretty high on the dyno especially with a SCd car. I ran mine in sixth one time when I was making about 800 rwhp on my Camaro and Mph got close to 190. Thats too high and even my Vet is exceeding 160 mph in 5th NA

[Doc Oc]

Thanks laynlo, appreciate the feedback. I already purchased the mp last night lol. Anxious to learn. It's starting to look like our tuner actually dialed things back vs oe programming if that's the case.

The car dyno'd 414 rw on 93, after tuning. I don't have any baselines so I tried not to get hung up on the number but I've been dynoing on that machine for a decade and know it isn't stingy.

[Joshinator99]

Originally Posted by Doc Oc

Thanks laynlo, appreciate the feedback. I already purchased the mp last night lol. Anxious to learn. It's starting to look like our tuner actually dialed things back vs oe programming if that's the case.

The car dyno'd 414 rw on 93, after tuning. I don't have any baselines so I tried not to get hung up on the number but I've been dynoing on that machine for a decade and know it isn't stingy.

If your tuner wasn’t sure about the knock, he undoubtedly played it safe as most tuners would. But someone knowledgeable about Gen V motors will know a stock motor on E85 is not seeing true knock at only 20 degrees of timing. With your own MPVI2 you can slowly tweak that up and datalog your results.