taken19

For the LS2 would be preferable, but I'm not sure that actually matters.

Most tuners dyno tune with maximum output in mind by adding timing or taking fuel until knock is sensed, then backing off one iteration. Many times this lends itself to variable timing across the RPM band for maximum power.

At the road course yesterday, one of the instructors mentioned that running a constant timing pattern (he suggested 20 or 21*) keeps the engine cooler overall and is much safer in the long term (more reliable motor)

I was curious what your thoughts are. Im at 485 rwhp right now at 24* peak timing and almost wish I has less Hp as I'm still learning. Running 20 or 21* would probably recuse my Hp by 20-30 but I would be ok with that.

What are you guys running out there who spend most of their time on the track?

vettman10

I think your instructor should stick to instructing, as he knows little on engine tuning. The amount of spark any gas engine can handle depends on several factors, and RPM is on of the primary ones. As RPM increases, the need for more spark advance increases. So, running 20-21 might be ok at higher RPM, it could very easily produce detnonation at low RPM. I have a part-time tuning business, and I tune my part time track car ('02 Z06) the same as I would tune any car. The only consideration of reducing spark advance for a track car is if the cooling system can't keep up with the thermal load and the coolant temp continues to rise, reduced spark advance would be protection from detnonation. But hey, everything made for the past 10+ years has had knock sensors, and if they sense detnonation, the spark is backed off, and if it continues, the program shifts to the "low octane" spark table where the advance is significantly reduced. So I would stay with what you have.

Zenak

How new are you to Road Racing? Are you an advanced driver or a novice?

Did you read the stickiest in this forum first like this one:
http://forums.corvetteforum.com/auto...e-learned.html

Dont specially tune out timing, instead learn to cool the motor better.. that link details al the most common ways for C5/6

Also I see you have in your profile: 25% UD pulley

UD pulleys are for 1/4 mile guys, where heat isnt as important. remember you are now under driving your water pump as well. Think about that when your car is being tortured at full RPM for an entire day how 25% less water flow does for temps??!?!

John B

Most seem to only care about peak hp bragging rights. I will leave a little more on the table in terms of A/F ratio & timing for vehicles that get used hard for extended periods.

taken19

Good advice. His ideas sounded reasonable so I thought I would throw them out there for you guys to support or disprove. I would like the most reliable motor possible.

taken19

6 track days total, so pretty new. I have moved to intermediate/solo in all four clubs I have driven with but I know I still have a lot to learn.

I use your sticky like the bible!!! Every track mod i have planned has used your input as a baseline or starting point. The motor was originally built by me for the drag strip, but fell in love with the road course after doing a ride along with a co-worker. I've been trying to get the rest of the car track ready ever since.

taken19

That's what I'm aiming for. When we tuned this car, we went to the point of knock, then backed down one iteration. If I need to back down a bit more in terms of spark and fatten up the fuel curve a bit in the name of reliability, I would much rather do that then buy a new motor in 6 months.

davidfarmer

my local tuner knows how to do road race cars, especially good when longevity is more important that outright power. He was able to pull timing (even lower than OEM) and lose virtually now power, and keep a nice safe rich fuel mixture, both to keep temps down.

Anyway, a slight power loss is a small price to pay for safe combustion, but I'd suggest finding a tuner who is already doing that type of work.

taken19

I wonder if it could be as simple as taking 1-2* of timing from the existing map across the map and fattening up .1-.2 on AFR. Same power and torque curve, just less of it and more conservative.

vettman10

If you are only at 24 degrees of peak timing now, that's not really too aggressive. I do wonder what he set the Power Enrichment (PE) fuel to. I only go to 12.5 - 12.3 when I tune. Some tuners want to get every last hp out and go to 12.8 or even 13.0. If you are at around 12.5 for PE fuel and 24 degrees peak timing, you are pretty safe. Also, the spark program has a 'safety' built in, in regards to coolant temp and timing - when the temp gets hot the PCM will start pulling timing, and the hotter it is, the more it pulls. Now this table can be altered by a tuner, so I would ask your tuner if he altered this table, and what he set the PE fuel to.

2MCHPWR

where are you measuring A/F from?
before the cats or after? does it matter?
My tuner said since i have cats (stock exhaust), and he put the tailpipe sniffer in, my reading was like 12.5 but since i have cats, in reality, its 1/2 point richer if we measure ahead of the cats (12.0). truth?

taken19

24* of peak timing at 12.5 AFR. Tuner fattened up fuel .2 after final tune to give added margin. Not having coolant temp issues - worst I have seen is 209. I'm working through oil cooling issues, but Z06 cooler helped a lot. Temps down ~20 degrees from last track day.

vettman10

Mosts tuners, me included test at the tailpipe because its so much easier and faster. How much difference does it make - this has been a hotly discussed subject on HP Tuners forum. The "standard" answer is as your tuner said, the actual A/F is .5 richer than indicated when testing at the tailpipe. However, during these discussions a 'senior' tuners who opinion I respect chimed in and said in actual testing they saw only .1 or .2 difference. I have personally tested one car in this criteria and found it only .2 richer.