I am just finishing up my header install and wonder if it would be worth my while to have a retune for this change.

I currently have a mail-order tune that I'm very happy with from PCM4Less that was done after I added a Corsa catback, Hotcam, & SLP claw CAI.

This header install replaced stock manifolds & cats with EM longtubes & RT high-flow cats feeding inton the Corsa system, so what I would like to know is if you pro tuners think I would beneifit from a new tweak to my mail order tune.

I feel certain it would be worthwhile if I were talking about a dyno tune where every last HP point can be wrung out, but I don't know since I'm going mail order (more of a ballpark tune).


Thanks in advance,
David

 

I get a retune with every performance change, also have the PCM chip, but purchased the unlimited retune option with my origional purchase.

 

Yeah, I paid a couple hundred up front, but all retunes are $50 for as long as I have the car.

David

 

No other opinions?

 

You are Still breathing thru mufflers. That means you aren't going to see That much of a flow difference. Some, sure, but nothing Too dramatic. This alone isn't enough of a departure from what you had to worry a lot about. Not like changing the cam, or heads, stuff that really Matters.

With that, the timing and fuel needed aren't going to be that different.

The Timing probably shouldn't change at All (assuming it's already where it Should be, or Could be).

The small increase in air flow (at any given TPS position) will be seen by the MAF, and therefore the Fuel delivered will be increased. Any error will be compensated for by the feedback loop (O2 sensors).

Where you would see a potential problem will be in Open loop - i.e. Full throttle. Errors in fuel There don't get corrected. This isn't as bad as it seems - the MAF is still measuring the air flow, afterall - if the fuel tables are even Close it'll be OK. The real changes, if any, needed would be in the target A/F ratio changes - how much richer would you Want it, which is sort of fuzzy - everyone agrees that you need Some, but how Much is up to the individual.

From my experience most tuners play it safe and go rich - less worry about detonation, particularly when you are also crowding the timing advance and don't really know where the coolant temp (and combustion chamber temp) is going to be with any reliability. Simpler on a dedicated race motor, nearly impossible on a street driven car.

Bottom line, I guess, is that without a dyno (or a day at the track with logging software) you aren't going to know how much or what to change. Mail order isn't going to be much help - it's just a guess on the part of the particular tuner. Might be better than the chip you have Now, but still a guess.

Spend the money on a tuner with a dyno, and Go there. Either that or live with what you have and call it good enough.

 

Well, Now I know who that crazy guy is with the red Corvette in the snow..

-- Joe

 

buy the software and tune it yourself and yes i would adjust the tune there should be a little more power to get out with headers and a fresh tune

 

Without a dyno you don't know if you are getting the most out of the tune safely.Usually you will get a price break on comebacks for a tuning adjustment with the same shop.
Mail order tunes get you in the ballpark but I like to know where my seat is.

 

Tuning on a dyno is a waste of time and money. Do you drive your car on a dyno or on the streets? How do you simulate up hill, down hill, light throttle around a corner on a dyno?

Even 1/4 mile racing can barely be simulated on a dyno because the load on a dyno is not variable.

Dyno's are for getting an idea how much HP an engine makes at a given AFR. Not useful for tuning cars.

-- Joe

 

I sort of disagree. With the conclusion, not the rest. The only thing you want or Need to learn on a dyno is what happems under "full throttle" open loop. Where is the fuel, how much advance is too much.

Nothing Else you do on the rollers is worth much on a driver, but at Least you get the open loop stuff sorted out - which is all that really matters here anyhow.

Al the rest of the stuff is best sorted out during the type of driving you do, datalogged and played with until you are happy with it. Takes time.

And, yes, that crazy guy in the snow would be me...