sothpaw2

I'm thinking of doing something to my PCM tune just because it came with the car when I bought it and I think it comes from a Predator tuner; so I'm not exactly sure of what I have.

My road course use is mild--last year I did 3 events (4 days total) on street tires & stock Z06 pads. I saw oil temps of 250-260 tops; if I see more next year I will short shift or bring it in.

What I'm after is a little insurance that my tune is not so lean anywhere that it will hurt the motor. Nothing more.

Now, my C5 Z car does have headers, X-pipe & hi-flow cats, and Varram air box from the first owner.

Questions:

1. If I dyno this car (wide band O2's--not sure if they do both banks??)as is and see a 12.8 A/F ratio or richer across the band is that good enough for the road course? If not, and I'm looking at the A/F curve, what do I look for?

2. How many of you guys do special tuning to try and mitigate lean cylinders on 7&8? Is this more of a race car issue and not something to worry about on street tires?

Thanks

Andrew

MattB

Have you asked in the C5 tune section? The only thing I can tell you is that 250 - 260 is not a bad oil temp. The DIC warning doesn't come until over 300. Getting a engine oil cooler is the only way to bring the temps down.

sothpaw2

Yes I asked. 20 reads and no replies. I guess they are not as familiar with the needs of the road course.

I might do the oil cooler sometime but I would prefer to avoid the expense until my skill level is higher. Right now virtually all my budget is track time+ gas. I haven't even gone thru a set of pads yet.

AU N EGL

Andrew, again that is something to talk to the tuner about.

Let the tuner know your concerns and let him do his magic.

sothpaw2

Working on it--trying to line up an appointment. It's always good though to have a gut check--I don't know how many of us are worrying about 7&8 on a stock car w/street tires.

Gordy M

For a road course, I would skip a dyno tune and find a good tuner in you area who likes to hpde. If you could run a scan log on a 15-20 minute session it would tell you more of the info you need to dial in a good tune. With street tire you are still placing a heavy load on the engine when going around corners and accelerating out. A scan log will reach all the intermediate cells in the PCM , WOT, PE, injector duty cycle, etc. Those results will probably tell you that you need larger injectors, or you may have engine knock coming off a corner, ect. This is some of the info you need to do a quality tune.

Wicked Weasel

sorry for not reading this earlier. Why not come up to our shop for the day and have us do your tune. You are about 2.5 hours away which is not long at all.

I do about 15 track days per year. My 2001 ECS H/C C5 had 3 years of road racing and over 50 1/4 mile passes on it before the timing chain broke. IF not for that I would have kept the engine, but decided to go with a 402 now.

We are at the track alot collecting data which helps you in the end. Doug @ ECS does all the tuning and you can PM him directly if you want to find out more.

Wicked Weasel

I forgot to say we are having a special right now

street tune $199
Dyno and street tune $299

0Randy@DRM

7 and 8 are problems that is forsure. There is many different things you can do to save the pistons from ending up in your cats. We flow all of our injectors and put the higher flowing ones in those holes. We don't run street-track cars on the edge. 5 horsepower doesn't matter one bit on the track. Run a splash of race gas just to make sure it's over kill. Run a colder plug in 7 and 8.

Randy

Lawdogg

Spoken like a true track guy. Listen to Randy, he won't steer you wrong.

sothpaw2

Ok--good advice here--what's an example of a colder plug I should run? I have the stock C5Z plugs, originals.

By not running street-track cars on the edge, you dial back the A/F ratio for the whole bank that 7&8 are a part of and watch the graph of that bank over the rpm range?

Thanks for the help, guys. I searched the archives and this isn't discussed--so it should help others too.

Bink

You would need to use EGTs to check each cylinder. Run it at 12.9 max (leanest) and about 11.9 at max torq - you'll be fine.

0Randy@DRM

We run alot of the NGK TR6 plugs. They are about the same heat range but are much cheaper and don't have the problems with tips falling out. You can run them in all 8 holes. You have to replace them more often but it's a good idea to check and change plugs more often then 100,000k miles anyways.
7 and 8 are on the oppsite sides of the engine. In theory, tune to the leanest hole. You can run a fairly stock engine to 13.1 and be just fine. The timing tables and other craziness is where you get into some trouble.

Randy

96CollectorSport

For HPDE's you want to leave a little on the table, a little extra fuel will help cool the engine. Lean is mean, more power means more heat.
Randy is right on who gives a crap about the last 5 hp if your going to be giving up reliability. Personally I wouldn't go higher than 12.7 for a track tune.

sothpaw2

Ok!! Conservative is what I'm talking about, it makes no sense to get every last hp out of it unless it's a race car and you're a good experienced driver.

0Randy@DRM

and a spare engine in the trailer.

Randy