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View Full Version : Lost Power Well below Redline When Hot


sciff5
08-09-2010, 02:55 PM
Hey Guys,

Yesterday I was at the autox course which is especially tough on my cooling system. High RPM pretty high load and relativly low speed.

Anyway after 6 back to back runs the car started to exhibit almost a self imposed lower rpm limit. I couldent see what rpm it was hitting this wierd artificial limiter but it was probably at least 2k below the actual redline. The instructor when driving my car even mentioned that he was hitting the limiter or fuel cut as he explained it, and I had to let him know we were no where near redline. I know IATS were high and coolant temps were around 230 so she was about as hot as I ever push it.

Funny thing is after the car got time to cool down I drove home and wound out a couple gears and everything was fine. This morning too everything was fine.

Anyone heard of anything like this?
Is this a safety feature in the PCM or something?
or
Don did you program some idiot proofing into my pcm to protect it from me?

ILuvPizzaTimes10
08-09-2010, 05:58 PM
im gunna go out a limb here and just say that any car thats hitting 230* should not be driven hard till its cooled off. you need better fans/radiator or just not hot lap it like that till its cooled down. i bet it wasnt the pcm and it was just from being hot and detonating.

sciff5
08-09-2010, 07:41 PM
Stock the high fan is supposed to come on at like 230 or 235 degrees, so they run these engines pretty hot from the factory.

I know the LT1s run even hotter so I am guessing its not too bad. If I come in after a run and the car is around 230 I shut it down and let it cool back off to say 190 or so before I make another run, because if I made another run when it was 230 by the end of that run it would probably be 245.. which to me is really starting to push things, anywhere near 250 is too hot in my mind. Hell 230 is too hot

I'de really like to keep it under 200 all the time. On my ride up there in the morning it was like 65 degrees out the car was running about 165 degrees the whole time. Even sitting and idling the car doesnt overheat, Autocross is just tough on the cooling system

Batman
08-09-2010, 09:39 PM
Ummm, high fan on my came on at 210 from the factory. I'd shit if it hit 230. I'm with Pizza that was probably detonation. You don't want to get it much above 210.

ILuvPizzaTimes10
08-09-2010, 10:42 PM
I doubt don tuned the fans for 230 thinking about it. Mine come on at 195ish and high fan at 210 I think at most. Id do some better fans or rad or something. The fuel at that temp will actually burn on th e intake valve before entering the cylinder causing a fuel cut condition at high engine load. From what I've seen in the past. Good luck getting it figured out.

Slowhawk
08-09-2010, 11:43 PM
You answered your own question.
Car running hot,inlet temp was probly hot as hell as well. Car was saying - lay off stupid before I puke my gut's out.

The fans work alot earlier than 230 degree's BUT there are speed limits for the fans which is about 40mph they shut off.

Get off the parking lots and hit bigger tracks that actually get airflow across the radiator on these hot days.

sciff5
08-10-2010, 12:10 AM
You answered your own question.
Car running hot,inlet temp was probly hot as hell as well. Car was saying - lay off stupid before I puke my gut's out.

The fans work alot earlier than 230 degree's BUT there are speed limits for the fans which is about 40mph they shut off.

Get off the parking lots and hit bigger tracks that actually get airflow across the radiator on these hot days.

I am adding a 4500cfm fan from a ford taurus and hitting New Hampshire Motor Speedway Aug 23rd where I'll get 4 25 minute sessions on their 1.6 mile track. I hope the improved speed/airflow on the road course is a little easier on the car than the parking lot.

I am just using the parking lot to shake down an entirely new setup, brand new suspension, brakes, clutch ect.

Maybe if you think its a good idea, before hard events from now on I'll throw in a couple gallons of unleaded race gas into the tank just for added protection.

Batman
08-10-2010, 02:39 AM
race fuel would help with detonation but 230 is still way too high engine temp, you are asking for problems at those temps

sciff5
08-10-2010, 02:45 AM
This is what I've read from several places

http://www.norotors.com/index.php?topic=1428.0

But I know Don lowers these numbers with his tunes.

Batman
08-10-2010, 03:01 AM
I don't know where they are getting there numbers but 225 for the first fan and 235 for the second is not correct. mine never got above 210-215, and I only know that from keeping the scan tool hooked up. Except for the 97-98 cars the temp gauge is useless on an LS1 car, it is an idiot gauge

ILuvPizzaTimes10
08-10-2010, 03:13 AM
Actually nick the 99 up g auge is the 2 wire while th e 1998 is a true reading 3 wire gauge

Slowhawk
08-11-2010, 01:13 AM
You should spend some time securing the radiator and making air damns for it.