bouncing and jerking when cruising

[gallegos276]

hello i did a dyno pull but even when im cruising my car is bouncing and jerking idk if its the tune or 3700 stall from tci. its about 2000-3000 rpm you can see it jerking and idk how to fix it. any help would be great. made 540 rwhp little rice at 12* so doing good but just need alittle help still. twin turbo 70mm on3 5.3 104mm sheet metal intake custom comp cam. flat top pistons 799 heads. t6 ngk
thanks
Ryan

[5FDP]

The VE tables isn't looking so hot, way too many spikes and dips in there.

I'd even lower your timing at cruising speeds into the 40's instead of letting it go all the way into the 50's.

Disable abuse mode too. Set it to 8,000rpm and 0mph.

[gallegos276]

Thank you for the good advise I was seeing it was 56 to 58 on cruise and wondered that. I'll look through it and try to smooth it out ve and try it again. Darn thought I had abuse mode completely disabled I'll comb through it all again . Great advise 100%

[mbray01]

Sounds like its either over timed, as mentioned above, your you have a secondary ignition miss

the on3 manifold setup is notorious for cooking plug wires

[gallegos276]

Yea is a custom build set up wires go under the headers with re location of coils. They look good gonna change plugs again. How do you check secondary misfire?

[kingtal0n]

According to hptuners you are using 7psi of boost (12.8psi atmospheric pressure + 7 = 20psi total pressure displayed)
It says barometric is 12.8psi thats how I am getting your elevation. is that elevation accurate?


Next Your IAT flips the fuck out after the dyno pull. Why is that? it shows -38*F or something ridiculous

Next, Your IAT rise is too steep. Either those turbos are not in their efficiency range, or you have a crap intercooler, or there is a massive boost leak. Please tell me you pressure tested your entire plumbing before attempting a dyno run!

At that boost pressure I would not expect to see much of a rise over say 112*F and yours is going 150*F+ so that is a death sentence on gasoline if you don't figure out why.

Next your coolant temp rise is also indicative of an issue. At 7psi of boost with a 12.8psi barometric, it may be your timing setting. 13* may not be enough timing. Did you try 15*?
I would push +2* timing at the same boost, using the same dyno, AFTER a pressure test, see if it picks up torque throughout the range while also helping keep the Coolant temp down. Those two signs will indicate that the timing was the issue. If you had an EGT gauge it would also drop significantly.

I presume this is a stock bottom end 5.3. What year and what compression ratio now? What transmission? And to be clear its on 93 octane right

edit: The log file has 3 different 'map' values in it, I am just now noticing this. One of them reads as high as 24psi so thats 11psi of boost give or take.
In which case the timing should be in the right range. The CTS and IAT should not climb like that unless there was a gigantic boost leak so a pressure test is necessary and hope that you find a leak otherwise there is another issue.

It could also be that the turbos are oversized for the power you are making currently. There is no compressor map to read but it does say on the on3 website each one is worth 350-600hp. So if you have two of those set to 650 then each one is providing less than 350 which would make the turbo unhappy, maybe, it could produce alot of hot air at very low flow rates. On3 recommends twin 70mm for 900-1000hp ranges fwiw. So if you are moving less than 850hp worth of air it might be just as bad as having an undersized turbo (hot air)
The high CTS climb makes me think the EGT is skyrocketing due to a boost leak though.