wannagofast

Hey guys I have had my C6Z sine new (2007) and just took it out on the weekend to a local road race course at Castro Raceway. My car ran awesome for the first 15 minutes then it started to just fall flat giving about 50-75% power? Coolant temps 220*F and Engine oil at 265*F. Is there any sort of display on the dash if it is going into reduced power mode? It never threw any codes nothing come on the dash? It was about 80*F outside and it is possible it had heat soak but I have never tracked the car before so have never experienced it before either?

carefulnow

Those temps are not particularly alarming, although it should be asked what oil are you running?

Is 220 truly the highest your coolant reached? I think its unlikely timing would be pulled with that water temp but I can't claim to know the specific curves/config in the stock ECU.

A problem I've had a few times is a spark plug wire popping off, however that would very quickly trigger a check engine light and have a large number of historic misfires stored.

Plug a scanner (or tech 2) into it and see if there are any stored codes/metrics.

You may want to run a 15w50 oil with sustained high oil temps in summer, it will help keep oil pressure up. You may notice very low oil pressures at lower engine speeds towards the end of a session.

Dan_the_C5_Man

That is not normal (power loss).

Did the engine recover after the session? No further issues? You may have codes stored - only certain codes trigger the Service Engine light.

If the car went into over temp / limp mode, you would have seen that on the DIC.

Please tell us you know about checking the valve guides (semi-related related to your post, just taking the opportunity to inform).

DaOtherOne

You didn't come close to hitting the temps required to required to have a problem.

From the owners manual.

COOLANT OVER TEMPERATURE
This message displays and a chime sounds if the engine coolant exceeds 255°F (124°C).

ENGINE PROTECTION REDUCE ENGINE RPM
This message displays if the engine oil temperature exceeds 320°F (160°C).

Mordeth

Those are normal temps for C6Z on a road course. Right where it likes to be. I routinely see 260-270 oil and 220 coolant after a long session at the Glen, where I'm typing this from right now. No issues or any loss of power. I run M1 0w40. If you are truly losing power then something else is going on.

I would check spark plugs and TPMS sensors. The car freaks out if anything is amiss here. I would also pull the cold air intake and inspect the MAF and throttle body. The blade should open and close by hand without sticking and the MAF should be clean. I would also check the battery for secure connections and voltage. If you aren't getting codes or messages like "Reduced Engine Power" then it maybe something internal.
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Any mods to the car worth noting? Are you simply losing power at WOT or is it exhibiting some other kind of behavior?

AzDave47

Stock my 09Z would see 285* oil temp and 245* water temp on road courses. It would run with some less engine power than first run of the day with 20* less ambient, but that is normal for these cars. If you hit 260*+ on the oil your should change from M1 5W-30.

DaOtherOne, thanks for the info on oil and coolant overtemp levels. They are certainly higher than I would want to run my engine stock or now with HCI.

wannagofast

Thanks for the feedback you guys! I have had some issues with the car that was diagnosed as being the throttle body being changed out last week (posted in c6 scan and tune section). I am running 5-30 Mobil 1 oil, car is still stock other than K&N air filter. I removed the heads and sent to lingenfelter at Xmas time. The plan is now to put the car on the dyno and run with about 10% brake and try to repeat and scan with HP tuners or Scan tech 2 tool. Coolant temperature for sure was 220*F, oil temperature was 265 and 20 lbs pressure at idle and after it sat for 1 hour between sessions it ran perfect for about 15 minutes into the second session then did the whole low power thing.

DaOtherOne

Are you using your street tires or swapping them for slicks? If you change tires you will need to relearn the TPMS sensors or the car will go into limp home mode.

wannagofast

I have Michelin super sports in OEM size, no TPMS issues that I know of.

RamAir972003

When tracking a car any in particular first think is changing to correct fluids and brakes. Second tires or wheels, then cooling radiator......also make sure you have good fuel......

Bill Dearborn

If a C6 has a problem with a tire pressure, a failure in the tire pressure system or no sensors and you are going over 55 mph it will apply the front brakes every time you turn the steering wheel for a corner.

That is what my C6Z would do. Go like hell on the straight and every time I turned into a corner the brakes would go on. One time I had a sensor fail as I completed a pass going through T4 at the Glen at about 120 mph. The brakes went on, the car understeered like hell thus moving to the left and the guy who I just passed almost ran into my rear.

Bill

db2xpert

Normally, there should be a msg in the DIC if there's a problem with a tire pressure or a tpms sensor.