lurkin' eg

whats up yall. hey im just wondering if i have to get a retune when i change my tranny. i have an turbo lsvtec setup with a b16 trans. its pretty quick but on the highway its sucks! so i just picked up a gsr for a little longer gearing but im not sure if it will affect the tune of the car. So will I have to get a retune when i change from the b16 trans to the gsr trans?

Drew Peacock

No.

wunfstgsr

unless it was tuned for a diffrent fd then no.

aasarsak

iTrader: (2)

x2

HiProfile

If its a big change, such as stock LS to '00 ITR, you might want to revisit the fuel map a little. If you go the opposite way, short to tall gearing, you might have to. The extra load can spool the turbo a bit sooner, which might put it into an untuned cell if your tuner didn't do his job thoroughly.

lurkin' eg

well from doin my own research and talkin to tuners, i believe that changing from the b16 to the gsr, a retune may not be necessary. plus my car is running a little rich as it is. but thanks for those who put in their input. if anybody else wants to chime is, feel free.

HighRevn

When you tune a car, your tuning the engine not the drivetrain. No you dont have to retune as long as it was tuned the right way the first time.

street_ride14

So what happens if your FinalDrive changes, Will it be OK to run a previous tune or get a retune ?

hoya_10fintec

I would personally check and make sure that everything(a/f and ign timing and such) is still within desired spec if I went from LS tranny to ITR.

LSTEG96

Completely disagree.


You aren't tuning the drivetrain, but if you went from a b16 tranny to an ls there would be more load on the engine now, which you are tuning.

DOHC_16v

I don't see why you're have to re-tune. Do your AFRs change from gear to gear? It's the same thing when changing the gear ratios/FD. Even if you have a longer first gear and there's more load, you experience more load in the next gear and so on. Engines aren't tuned based on gear ratios.

I CRX I

thia is a good question! i'd like to know more about this if anybody can chime in with personal experience. i would assume there would have to be a re-tune bein as the RPM's and throttle position probably wouldnt match up anymore but then again this is just an assumption...

EARLdaSQUIRREL

if the car was tuned properly for the cruising rpm's etc it will not or should not need a retune

if this was true the tuner would need a seperate map for every gear and some way of telling what gear it was in, since no tuning software that i know of has this (although most have gear based corrections) i would assume you would be perfectly fine changing and probably get better gas mileage

lurkin' eg

okay i plan on talkin to my tuner, but there are some good points. i personally believe that goin from b16 to gsr should be alright cause as EARLdaSQUIRREL said earlier, the tuner would need a seperate map for every gear. but ill def talk to my tuner about it though

aasarsak

iTrader: (2)

No, you misunderstood his post. He was saying that it is not possible to have a different map for every gear. The point he was trying to make is that you will not need a re-tune.

Gear ratio has nothing to do with tuning. The ECU doesn't see what gear you're in. The ECU makes fuel/timing corrections based on input from the sensors attached to the motor, not the transmission. Your ECU has no way of knowing whether it has a B16 tranny or an LS tranny.

You do NOT need a re-tune.

EARLdaSQUIRREL

exactly... thank you

HighRevn

Which if you have tuned correctly, such as on a stead state dyno and have went through the cells on each table, you should be fine.

aasarsak

iTrader: (2)

This logic is flawed. it is possible to have the exact same load on either tranny.

Case in point: Let's say the LS tranny exerts a torque load of X on the motor in 3rd gear under acceleration from 30 - 40 mph. Now let's say we have a B16 tranny which exerts a torque load of X - a in the same gear and rate of acceleration. Looking only at this case, one may conclude that it would be necessary to tune each separate tranny; however, what happens when one is travelling uphill or downhill and the load factors change.

Example: LS tranny exerts torque load X in 3rd gear under constant acceleration from 30 - 40 mph. It is mathematically possible to calculate the angle of incline (driving uphill) at which the B16 tranny would exert the same torque load on the engine given the same gear and rate of acceleration. Using this example, it is clear that either tranny can exert the same load under the same rate of acceleration given different road conditions.

This shows that no matter what tranny he has attached to his car, the ECU will make the exact same fuel/timing corrections.

I say again, you do NOT need to re-tune your car

if you really want to throw away your cash, just give it to me. I need some new door panels

connor53

True, but what about being at 3300rpm in 3rd in the GSR trans, vs 3500rpms in 3rd with the B16 Trans? Or visa versa, (just hypathetical numbers) What about problems such as that? If it were my car I would ATLEAST take 2-3 quick pulls with a wideband and my laptop on a dyno to verify everythings copesthetic. I'm NOT disagreeing with you AT ALL aasarak. Just trying to save the man some pain.

aasarsak

iTrader: (2)

And I'm just trying to save him some dough...

Like I said, it doesn't matter what tryanny he has. The fact remains that no matter what engine rotational velocity (RPM), the only thing that changes is the vehicle speed and load. Speed in this case can be ignored since the only factor that affects the engine tuning is the load placed on the motor under acceleration.

The only factors that determine how much timing and fuel the motor will get is based solely on the data recieve from the sensors attached to the motor.

To help you visualize the connection, think about what causes load. There are several factors that effect load. Just to name a few: vehicle weight, rate of acceleration, and rotational weight (moving parts like clutch, wheels, axles, etc.) which is related to the moment of inertia.

To say that the reason swapping trannys would constitute a re-tune would be the equivelant of saying that you need a retune when you add a passenger to the car, or if you increase the rate of acceleration, or you change the type of tire or wheels you use. All these things do is increase the load on the engine.

Is it starting to make a little more sense now?

aasarsak

iTrader: (2)

This is why most modern chassis dynos now use a dynamic load feature which simulates these things so that a tuner can create a more realistic tune.

connor53

again. Didn't disagree with you at all. And I totally agree as far as applying a load while on a dyno, to simulate true life characteristics.

aasarsak

iTrader: (2)

Cool man. I was just confused as to what pain you were trying to save him from by having him do a couple of dyno pulls. You mean like a sort of just in case thing?

ralph11sec

based on experience,

a simple mild tune modification is needed.

for example the car get 1bar @ 5trpm on a 4.7 itr tranny.
then switched to a 4.2 tranny, obviously you'll get 1bar a bit earlier.
but basically no retune is need. not that significant at least.

hoya_10fintec

Good example. Thank you for sharing...

So basically it comes down to this:

Whatever you do to your engine or tranny, DOUBLE CHECK YOUR WORK/TUNE!!