starshifter

I'm very ignorant when it comes to software tuning. Someone, please answer these questions. I'll truly appreciate it.

I have a 99 C5 6-speed with 12K miles on it. It's bone stock except for a K&N air filter, a Borla Stinger catback exhaust and a 4.10 axle ratio. Would I benefit from a mail order tune? I'm more interested in raising fuel economy than in gaining horsepower (although a combination of the two would be best) and I don't want to risk blowing my engine. Can that be done or is the car already set to run as lean as possible?

My DIC always overestimates my average MPG by 10-12%. Can the PCM be reprogrammed to indicate actual MPG instead (i.e. current number multiplied by 0.89)?

If fuel cut off were changed from about 6200RPM to say 6700RPM, wouldn't it be bad for the engine to rev. that high without supporting modifications?

Who would you recommend I send my PCM to? Are there instructions on how to locate, remove and later replace the PCM for my car?

How much does a mail order tune cost? And a tune in the shop? Is there a good tuner near washington DC?

Thanks a lot.

soundengineer

iTrader: (16)

It might be smarte and possibly cheaper for somebody in your Area with HP Tuners Or EFI Live to pay a little visit and do the programming for you..
I'm sure there is somebody close to DC that would help out for less than a "mail order guess"

the few mods you have are pretty common mods...
your MPG is probably off because your rear gear is different than stock...I would have guessed closer to 15%-20% off from the gear change

if fuel cutoff is changed to a higer RPM you really need some different vavle springs, and different pushrods...
you can rev it a little higher if you dare..but you will start getting into a grey area around 6200 and vou start to get valve float above that...which usually leads to a loss of power from the float..and sometimes bent valves and pushrods...over rev is the most common reason for bent valves...not a cheap or easy repair job..
the PCM I believe is in the engine bay...and I thought it was over against the passenger wall almost up under the cowl....but I dont remember for certain on the vettes....
dont waste money on a shop/dyno tune...
hey typically tune the wrong things and only mess up setting up proper fueling..
they are usually only good for WOT...tuned the wrong way...

starshifter

Thanks, from your input I guess I'd better look for someone whom I can drive to to do a tune w/o dyno and not think about raising the rev. limiter. If I were near Kansas City, I'd give you a call.

I'm still wondering about my DIC's MPG average because that should not be affected by the 4.10. I was having the same exact problem before the gear change. It seems to be common among 99-00 C5s but less common on 01-04s. That's why I was wondering whether a tune would fix it. On the C5, the speed sensor counts wheel rotations while the fuel sensor is supposed to measure how much fuel runs through the injectors. It seems all the average would have to do is integrate the fuel measurement and divide it by the number of miles driven, but it must be doing something else to always overestimate actual MPG.

And as far as fuel economy in normal daily driving at low RPM is concerned, can the tune improve that, even in a 6-speed? I had always assumed tuning on a nearly stock car is only useful for an automatic.

Black02SS

iTrader: (36)

Get with HumpinSS. He can take care of you. He isn't far at all.

soundengineer

iTrader: (16)

every car can stand to gain from a tune..auto or six speed...even completely stock vehicles