Ltrims at idle?
Launching!
Joined: Feb 2002
Posts: 210
Likes: 0
From: miami
Re: Ltrims at idle? Arent the Ltrim supposed to be in the negative range? It might just be that since my car is supercgarges it need extra gas, but I dont believe this is true. Everyone has always told me to shoot for negative (-3 to -8) ltrims.
So colonel, Why is it OK for dean to be running in the positive +3 to +8.
I might not be understanding something, OPlease clarify?
So colonel, Why is it OK for dean to be running in the positive +3 to +8.
I might not be understanding something, OPlease clarify?
Trending Topics
Re: Ltrims at idle? There is no major problem with slightly positive LTFTs.
This is what happens at WOT: If the LTFTs are positive (PCM is adding fuel during cruising around), when the engine goes WOT, the PCM will add in extra fuel equal to the positive LTFT value. This is in addition to any extra fuel required thru the PE tables.
If the LTFTs are negative while cruising around, when the engine goes into WOT, the PCM will not take away (or add extra) fuel based on the negative LTFT value (the LTFT is set to zero). All extra fuel is gotten only thru the PE tables.
So if you are tuning for max HP at WOT, you do not want extra fuel coming into the fuel equation from the LTFT value. The LTFT value can change a small amount and have a big effect on WOT AFR, if it stays negative, it will not have any effect on the WOT operation of your engine.
This is what happens at WOT: If the LTFTs are positive (PCM is adding fuel during cruising around), when the engine goes WOT, the PCM will add in extra fuel equal to the positive LTFT value. This is in addition to any extra fuel required thru the PE tables.
If the LTFTs are negative while cruising around, when the engine goes into WOT, the PCM will not take away (or add extra) fuel based on the negative LTFT value (the LTFT is set to zero). All extra fuel is gotten only thru the PE tables.
So if you are tuning for max HP at WOT, you do not want extra fuel coming into the fuel equation from the LTFT value. The LTFT value can change a small amount and have a big effect on WOT AFR, if it stays negative, it will not have any effect on the WOT operation of your engine.
LS1 Tech Stories
The Best V8 Stories One Small Block at Time
6 Common C5 Corvette Failures and What's Involved In Repairing Them
Pouria Savadkouei
Retro Modern Bandit Pontiac Trans AM Comes With Burt Reynolds' Autograph
Verdad Gallardo
Top 10 Greatest Cadillac V Series Performance Models Ever, Ranked
Pouria Savadkouei
Top 10 Most Powerful Chevy Trucks Ever Made!
Hennessey's New Supercharged Silverado ZR2 Has 700 HP
Verdad Gallardo
Coachbuilt N2A Anteros Is an LS2-Powered C6 Corvette In Italian Clothes
Verdad Gallardo
Awesome K5 Blazer Restomod Comes With C7 Corvette Power
Verdad Gallardo
10 Camaros You Should Never Buy
10 LS Engine Myths That Refuse to Die
Verdad Gallardo Re: Ltrims at idle? JAS,
I agree with you completely. For WOT tuning, you need a good wide band O2 sensor, no doubt about it. I assumed that we all know that the stock O2 sensor should not be used to tune WOT because they are not accurate enough to tune such a critical thing as WOT.
I calibrated my MAF table for my GMAF by using the LTFTs while doing part throotle stuff on the street. Once I got the LTFTs under 0% across all RPMs, I worked on the timing table and finally got on a chassis dyno with a AFR meter (wide band O2 sensor). What I found out was that I was at 13.2AFR when my O2 sensors put out 960 to 970mV. Most people would say that I was very rich at WOT with the O2s at 970mV, but that just points out how inaccurate our O2 sensors are. I'm pulling 400RWHP with 28* timing at 6300RPM. Not bad for my setup.
Basically, we need the calibrate our O2 sensors with a known good AFR meter. My O2s read 970mV for 13.2 AFR, but your O2s might put out 860mV for 13.2 AFR.
I agree with you completely. For WOT tuning, you need a good wide band O2 sensor, no doubt about it. I assumed that we all know that the stock O2 sensor should not be used to tune WOT because they are not accurate enough to tune such a critical thing as WOT.
I calibrated my MAF table for my GMAF by using the LTFTs while doing part throotle stuff on the street. Once I got the LTFTs under 0% across all RPMs, I worked on the timing table and finally got on a chassis dyno with a AFR meter (wide band O2 sensor). What I found out was that I was at 13.2AFR when my O2 sensors put out 960 to 970mV. Most people would say that I was very rich at WOT with the O2s at 970mV, but that just points out how inaccurate our O2 sensors are. I'm pulling 400RWHP with 28* timing at 6300RPM. Not bad for my setup.
Basically, we need the calibrate our O2 sensors with a known good AFR meter. My O2s read 970mV for 13.2 AFR, but your O2s might put out 860mV for 13.2 AFR.