Weird Rev Limit Resolved

I reported in my recent trip to NJMP that I was experiencing weird rev limits as Bumblestook's oil temperature rose. Unfortunately, I left my tuning laptop at home so I couldn't fix it on track and it was frustrating to have the limiter kick it as low as 7000 rpms at times. I was convinced it was due to engine protection settings on the car due to oil temps but that turned out not to be the case.

Engine protection screen on my Haltech tune - 6-28-2020

According to that page if any of the following conditions are met, the car will go into limp mode and limit my revs to 3500rpms.

• Coolant above 110C (230F) for at least 2.5 seconds
• Oil temp above 135C (275F) for at least 2.5 seconds
• Oil pressure below 172.4 kPa (25psi) with TPS at 25% and RPM above 2000

The last condition I already experienced when my oil pressure sender failed two weeks ago so it can't have been this because the car didn't go into limp mode. It simply had a lower rev limit. I looked at my track video and looked at what my Racepak dash was showing me. At the hottest the car was at 213F coolant and 248F oil so I was well within the engine protection values. 

I reached out to Jeff Evans and he told me to check my rev limit table since the Haltech rev limit can be configured to scale based on coolant temp and sure enough that's where the problem was. This is actually a really neat feature and gives you the ability to limit revs until the car is up to temp. 

Coolant based rev-limit (old values) - 6-28-2020

Similarly, it can be used to limit revs if the temps get too high. What was happening was that the car was going above 100C on the coolant temps due the high ambient temps that day and because the rev limiter was configured for 2000rpm at 120C, it was scaling down my rev limit as the coolant temps went up. This explains why the rev limit seemed variable. Since I've already configured other warning lights regarding oil and coolant temps. I changed the 120C value to the normal rev limit so I won't run into this issue again. I also took the opportunity to lower the rev limit at 60C to the stock limiter of 7900. Seemed like a reasonable thing to do until the engine gets to full operating temp. 

Coolant based rev-limit (new values) - 6-29-2020