nj1266

iTrader: (6)

You are wrong.

Here is what you do to find out that you are indeed wrong. Install an Injen intake/AEM intake/HKS intake on an Evo X. I have logged the trims on all three. Immediately log the AFR at WOT in 3rd or 4th gear. Then drive the car at a steady speed for about 45 minutes while logging the fuel trims. Once the fuel trims go positive by about 6% (Injen), 10-12% (AEM), 10% (HKS). Then do a WOT run in 3rd or 4th gear. The AFR will be richer on the second run that it is on the first run. That is why you MUST get the fuel trims stable on an Evo X BEFORE you tune the AFR.

I have done this multiple times with multiple intakes and the result is the same.

LTFT change will change the AFR at WOT.

nj1266

iTrader: (6)

You should not do that. It is very important to get the fuel trims stable before you adjust the AFR. You must drive the car and see where the LTFT end up. Then you must adjust the latencies to get the LTFT to +/-5%. Then you set the AFR.

If you are not letting the trims settle and keeping them below +/-5% (Cobb suggests +/-8%), then the AFR will be inconsistent.

Say you dialed the AFR on an Evo X immediately after you installed an intake and you set the AFR at 11:1 at WOT. At the time the LTFT was +2%. Then the LTFT drifted to +10%. Both the AEM and the HKS drift to +10% or more. The AFR will now become 9.9:1 and the car will run rich. That will make the AFR inconsistent.

HB Speed

iTrader: (1)

You are correct Naji.

I've been telling people this forever now. i do however have a different way of doing it...... Gotta love hot wire mafs

nj1266

iTrader: (6)

I thought I was going crazy. I thought I was the only one who was experiencing this. Since you tune Subarus, you have a lot of experience with hotwire MAFs. Since I started tuning Subarus, I also became aware of the impact if an intake on the LTFT and its impat on AFR at WOT operation.

HB Speed

iTrader: (1)

yer catchin on!

nj1266

iTrader: (6)

Here is a perfect example of the impact of trims on the AFR. This is an Evo X GSR that had an HKS intake. I was tuning the car and had these two different AFRs even though I did not change the fuel table.



In the above chart the AFR was tapering to 11.2/10.9 by redline and the LTFT was +10.2%.

Check what happens to the AFR in the chart below when the LTFT goes down to +6.3%



The trims fell by ~4%. Look what happened to the AFR at redline. It leaned out to 11.8:1

Let us do the math 11.2x0.04=0.448. Now add 11.2+0.448 and you get 11.65 which is very close to the 11.8:1 that I logged when the LTFT was at 6.3%.

Let us pick another section of the rpm, 5000 rpm.

The AFR when the LTFT was +10.3% was 11.5:1. The LTFT then falls to 6.3%, ~4% drop. What happens to the AFR? It leans out to 11.9:1.

Let us do the math. 11.5x0.04=0.46. 11.5+0.46=11.96 which is very close to the 11.9:1 that was logged when the trim fell to 6.3%

There is no doubt in my mind that the AFR will not be stable w/o making the LTFT stable first. It must be done when an intake is installed on either the Evo X or the RA.

boondoc

iTrader: (4)

I am so confused

murlo26

iTrader: (9)

Put it this way, if you want to be safe just get a tune when you put parts on, simplifies everything

boondoc

iTrader: (4)

This i kno. But its the convo at hand. All the trim adjustments or what not. So the intakes that TTP are refering are not bad if u take the time and tune the trims?

silthos

iTrader: (23)

+1

nj1266

iTrader: (6)

Yes, that is the core of it. If a tuner takes his time and makes sure that the trims are not going nuts, then ANY intake can be tuned to work on the RA. It should take one hour to set the trims. Insist that the tuner does that. If he says that the trims are not affected by the intake, then find another tuner.

Ladogaboy

iTrader: (1)

So, do the trims change from car to car (i.e., one Ralliart will not be the same as the next), or if you have already mapped the trims on a particular intake in one Ralliart, could you use the map over? Basically, could you save considerable tuning time if you are working on several Ralliarts with the same intakes?

boondoc

iTrader: (4)

Ahhhh....Thank you for clearing that up for me.

+1 Good question.

HB Speed

iTrader: (1)

i said that earlier and got deleted hahah
naj

nj1266

iTrader: (6)

Trims change from car to car, gas to gas, location to location. There are many things that impact trims. Having said that, if you have done the smae intake over and over again on a ralliart, you will discover a trim adjustment that will get your trims 90% under control. Your trims will never be zero. It is impossible. The tuner has to get them as close to zero as possible. I like +/-5%. Cobb suggests +/-8%. I think that is too much.

Adjusting trims is time intensive since the ECU changes the LTFT every 4 minutes. You need to drive the car at a steady speed to get the trims to settle down at a number. For example, you drive the car and after several 4 minute cycles the trim settles at +10%. Then you flash the ECU to adjust the latency to bring the trims down. So now you have to drive for another 20-30 mintues to get the trims to settle lower at +/-5%. The whole process takes about an hour. Once the trims have settled at +/-5%, then you can tune the AFR.