L.T.F.T. off by having a s.s.r.a. and ss scoop?

[smslyguy]

Is it possible to have inconsistant L.T.F.T by having a ss scoop and a s.s.r.a.?? Don't know if it would be an inconsitant reading on the m.a.f sensor or not? Has anyone else had both on there ss car's?

[WeathermanShawn]

smslyguy:

If you can post up a log that shows your MAF Frequency you can easily evaluate whether it has unusual oscillations. I have the LS1 'Free Air Mod', and have not see any unusual frequencies or oscillations. It is normally not an issue of the LS1 as there is ample distance between the incoming air and the MAF.

Having said that, an air-box itself will normally cause your LTFT's to become more positive, but the MAF Frequency signal itself should remain 'clean'.

The two most likely cases can be in a ported MAF or in the tuning of the MAF Calibration Table itself. Occasional different blends of gasoline can cause a change in LTFT's, but usually the entire MAF curve will drift in the same direction.

90% of the time you just need to carefully log LTFT's under identical ECT's and IAT's and properly calibrate your MAF Calibration Table. If after 1-2 sessions you are still having problems, it is usually some other problem with the tune.

The short answer would be to post a tune and log. It is easy to spot.

Good luck..

[SSpdDmon]

My money is on the fact that your MAF is descreened. That's a good way to get inconsistent MAF readings, which will confuse your FT's.

[WeathermanShawn]

Screen-shot of 80 MPH Interstate Cruise with MAF Frequency logged.

Probably less than 100 (Hz) difference at that speed, with no LTFT drift...

[smslyguy]

smslyguy:

If you can post up a log that shows your MAF Frequency you can easily evaluate whether it has unusual oscillations. I have the LS1 'Free Air Mod', and have not see any unusual frequencies or oscillations. It is normally not an issue of the LS1 as there is ample distance between the incoming air and the MAF.

Having said that, an air-box itself will normally cause your LTFT's to become more positive, but the MAF Frequency signal itself should remain 'clean'.

The two most likely cases can be in a ported MAF or in the tuning of the MAF Calibration Table itself. Occasional different blends of gasoline can cause a change in LTFT's, but usually the entire MAF curve will drift in the same direction.

90% of the time you just need to carefully log LTFT's under identical ECT's and IAT's and properly calibrate your MAF Calibration Table. If after 1-2 sessions you are still having problems, it is usually some other problem with the tune.

The short answer would be to post a tune and log. It is easy to spot.

Good luck..

shawn, i'm not having inconsistant reading that was kind of a hypothetical. A little of topic but, should your v.e tables be a bit higher than stock after running the mods i have in my sig? I am actually about 5-10% below stock v.e tables on my tune. The L.T.F.T are within reason + or -3 i would say. I would think that after adding header ( yes they are short tubes) would increase the air flow, not decrease it. My timming tables are bumped up a little from stock but everything from 2000 r.p.m. and up is still stock. Here is a copy of my tune

[WeathermanShawn]

Well, I noticed your MAF Calibration Table is still stock. If you go by the CALC.VE Table premise..that you can calculate your VE Table utilizing the MAF and LTFTBENS, then your VE Table may not be that far off.

A cam will defiantly change the look of your VE Table, as will heads. Exhaust/intake mods will usually add upper RPM values to your VE Table.

Here would be my question(s):

1. What is the Max Rpm you can hit on a WOT run.
2. What is the Max MAF Freq(s) you hit on a WOT Run.
3. What is your average LTFT's.
4. How close is Actual WOT AFR to Commanded AFR.

I guess I am a little surprised that your RPM/MAP VE Table values are not higher. But,that depends on your MAF Airflow (for me to compare).

Disclaimer: This is utilizing the CALC.VE Table theory.

So, yes I would think it would be higher, but if you can answer 1-4, I might be able to make a better estimate..

[smslyguy]

Well, I noticed your MAF Calibration Table is still stock. If you go by the CALC.VE Table premise..that you can calculate your VE Table utilizing the MAF and LTFTBENS, then your VE Table may not be that far off.

A cam will defiantly change the look of your VE Table, as will heads. Exhaust/intake mods will usually add upper RPM values to your VE Table.

Here would be my question(s):

1. What is the Max Rpm you can hit on a WOT run.
2. What is the Max MAF Freq(s) you hit on a WOT Run.
3. What is your average LTFT's.
4. How close is Actual WOT AFR to Commanded AFR.

I guess I am a little surprised that your RPM/MAP VE Table values are not higher. But,that depends on your MAF Airflow (for me to compare).

Disclaimer: This is utilizing the CALC.VE Table theory.

So, yes I would think it would be higher, but if you can answer 1-4, I might be able to make a better estimate..

I have worked with the ben's for the maf table before and infact i had just done a open loop run using the maf exclusively and the ben's where within reason. That is kinda what i had thought about the v.e tables as well. Here is the answers to your ?

1. I can hit 6200 r.p.m before the rev limiter kicks in.
2.8250 is what i usaully hit.
3.The average L.t.f.t is usually between -5 to -2
4.Now this very's a little bit. some run's it is spot on while other's it is off by no more than .5 a.f.r.
I am on another computer right now i will add a run with the open loop for the maf scan and a run with the l.t.f.t

[WeathermanShawn]

8250 is pretty low for a MAF Frequency. But that may be normal for a stock H/C with a Rev Limiter set at 6250 Rpm.

I am slightly confused where you said you run 'open-loop' with BENS. How are you getting LTFTBENS now. Are you back to closed-loop?

My specialty is the application of the CALC.VE Table utilizing MAF. If you tuned open-loop, I can't really equate your current VE Table appropriately, as the method I use is done differently.

Perhaps someone with a stock setup can comment on the 8250 (Hz) MAF Frequency and whether that is low.

[smslyguy]

here is a copy of one of my scan's in open loop to use the w.b ben's for calc maf freq. and the other is a copy of c.l. And yes i am back to c.l. loop now.

[WeathermanShawn]

Chris, a few comments..

Generally it appears your MAF is calibrated correctly. All your LTFTBENS fall within range.

The reason your CALC.VE Table %'s are not that high, is because on this particular Closed-Loop log you simply did not hit the upper Rpm's and MAF Frequency's. You hit 8600 on the MAF, but never took it past 4500 Rpm's.

Next time you log closed-loop try a few things.

1. Keep channels to 24 or less.
2. Hit 100% TPS several times.
3. Try to hit near your Rev Limiter.

Based on that, I am sure you would hit at least 10,000 Hz of the MAF, and over 100% VE Table. Your tune looks basically good, you just need to do some more precise logging.

Really, not too bad.

[smslyguy]

Shawn thanks for the reply. Here is a scan hitting 9500 on the maf scale and only 23 channels as well. I don't really like hitting 6200 r.p.m anymore since i slipped my clutch the last time i hit that high. Factory clutch with only at the time 36,000 miles on it. Since then i have been trying to baby it a little. It's hard to believe that it still works good though. For now. lol.

[WeathermanShawn]

Not bad Chris...

Overall it looks like you have a pretty decent tune. Your MAF looks fairly steady at WOT.

I burned out my factory clutch in no time. Upgraded to the LS7 clutch. Its a little heavier, but it has stood up well.

Later..