Ve tuning question
Staging Lane
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LFA - Log File Analyser (Software program written by Chris Bennight??)
Bink - I agree that the S/D programs (such as the Holden GTS which run factory MAFless setup) utilise the VE tables in a different manner to cars running a MAF. I'm basing my VE tuning results from the GTS calibration I've forced into the PCM
In my experimenting I've noticed that a factory MAF calibration with the MAF disconnected will not behave in the same way a factory MAFless calibration will. Several problems I've observed tuning with a MAF calibration and disconnecting the MAF is that an A4 will not shift gears properly and you cannot hold stable ignition timing over 4800rpm. Rule of thumb is that the spark drop to 15 - 18 degrees at WOT over 4800rpm.
I guess the benefit of have the only factory MAFless LS1 cars in the World here in Australia gives us a definite advantage with MAFless tuning. Hence we also see good results with MAFless tunes in our cars with close to stock idle and low end drivability. Lucky for us we have both M6 and A4 GTS vehicles here, making the A4's easy to tune as well
Bink - I agree that the S/D programs (such as the Holden GTS which run factory MAFless setup) utilise the VE tables in a different manner to cars running a MAF. I'm basing my VE tuning results from the GTS calibration I've forced into the PCM
In my experimenting I've noticed that a factory MAF calibration with the MAF disconnected will not behave in the same way a factory MAFless calibration will. Several problems I've observed tuning with a MAF calibration and disconnecting the MAF is that an A4 will not shift gears properly and you cannot hold stable ignition timing over 4800rpm. Rule of thumb is that the spark drop to 15 - 18 degrees at WOT over 4800rpm.
I guess the benefit of have the only factory MAFless LS1 cars in the World here in Australia gives us a definite advantage with MAFless tuning. Hence we also see good results with MAFless tunes in our cars with close to stock idle and low end drivability. Lucky for us we have both M6 and A4 GTS vehicles here, making the A4's easy to tune as well
Originally Posted by VT2 EXEC LS1
Agreed. Neither is a MAF and accurate sensing device when used with large cams. Too much reversion at low RPM causes the MAF frequency to become unstable. Having an idle speed of 1200 - 1400 RPM is not a fix for that problem either.
Agreed. I believe any tuning (part throttle or full throttle should ALWAYS) be checked with a wideband O2 sensor.
Agreed. I believe any tuning (part throttle or full throttle should ALWAYS) be checked with a wideband O2 sensor.
MAFs only become unstable when the manifold pressure starts to drop below 30 kPa absolute. Cams with a 250+ intake duration are the only ones that will generate this kind of problem. At these durations, SD tuning is no picnic either though.
LTerms start to become unstable with the 230+ duration cams; depending on how free the exhaust is. The better/bigger the exhaust the more unreliable the Lterms become.
With that being said, I would much rather use the MAF and calculate out a SD tune.
Who idles the majority of these cars at 1400? There are only a few select cams that need an idle of ~1200 (binks has one of them). The rest of the cams in this industry can have the idle set below 1000. In fact I just finished one yesterday on an automatic, ~240 duration with the idle set to 900 rpm.
MAFless tuning is okay, but I have yet to see the benefits of it. We first started pulling MAFs about a year ago (inhouse car), and I have honestly never seen a clear advantage of MAFless over MAF tuning. With the wide variety of free flowing, larger diameter MAFs that are available for these cars, I don't see any purpose to the pull the MAF.
Bottom line: 99% of the setups out there don't need to be running MAFless. The same power/response/drivability is obtainable with a proper MAF.
Just my yank opinion
HumpinSS- Thanks for the help! I've said it before...I'll say it again...it never ceases to amaze me how kind people are around here. That said - obviously, I am the analog man! Question - you added 4% more fuel after the new VE values were flashed- how much of an increase (%) were your new VE values over yuor stock VE values????
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Originally Posted by HumpinSS
I have to check when i get home. I dont recall. I guess i could fix that in the VE table by tweaking a little more but my quick and dirty way of doing it was to add it back in the IFR table. If i told you 10% what would be your next suggestion (will verify later)?
joel
Staging Lane
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Originally Posted by NoGo
LTerms start to become unstable with the 230+ duration cams; depending on how free the exhaust is. The better/bigger the exhaust the more unreliable the Lterms become.
Originally Posted by NoGo
With that being said, I would much rather use the MAF and calculate out a SD tune.
Originally Posted by Nogo
Who idles the majority of these cars at 1400? There are only a few select cams that need an idle of ~1200 (binks has one of them).
Originally Posted by NoGo
MAFless tuning is okay, but I have yet to see the benefits of it. We first started pulling MAFs about a year ago (inhouse car), and I have honestly never seen a clear advantage of MAFless over MAF tuning. With the wide variety of free flowing, larger diameter MAFs that are available for these cars, I don't see any purpose to the pull the MAF.
Bottom line: 99% of the setups out there don't need to be running MAFless. The same power/response/drivability is obtainable with a proper MAF.
Bottom line: 99% of the setups out there don't need to be running MAFless. The same power/response/drivability is obtainable with a proper MAF.
I'm not challenging your tuning abilities, just trying to get an idea on everyone's perspective on different tuning methods
I don't write the tuning Bible. I just write how I see it. If you folks down under want to use Lterms go ahead. Odds are though, if you aren't running into LTerm problems, then your exhaust isn't big enough to cause problems.
I don't use LTerms. In fact, most of our high HP cars don't even have oxygen sensors. My personal car hasn't had oxygen sensors for well over a year. They are for emmissions, not power.
If you can comfortably idle your cam at 1000 rpm then good for you. I'm sure we could idle them lower than 1200, but cams of that size usually find themselves in front of a TH400 and equivilant converter (ie heavly loaded driveline) and I prefer having the extra RPM when placed into gear. Plus, I didn't know there was a competition going on to see who could get these things to idle the lowest
Larger MAF's are what I use to eliminate the the MAF restriction in the intake tract. Install a descreened 85mm MAF. The MAF is usually not our restriction problem. The throttle body is usually the pinchpoint.
Again, this brings me back to my original claim that I have yet to see a GOOD reason for running these things MAFless.
For very large cam setups I run a hybrid combination of MAF and VE tuning. It works well. You can get the very large cams to idle at the lower RPMs and you don't have the side effects that you get with SD tuning.
I don't use LTerms. In fact, most of our high HP cars don't even have oxygen sensors. My personal car hasn't had oxygen sensors for well over a year. They are for emmissions, not power.
If you can comfortably idle your cam at 1000 rpm then good for you. I'm sure we could idle them lower than 1200, but cams of that size usually find themselves in front of a TH400 and equivilant converter (ie heavly loaded driveline) and I prefer having the extra RPM when placed into gear. Plus, I didn't know there was a competition going on to see who could get these things to idle the lowest
Larger MAF's are what I use to eliminate the the MAF restriction in the intake tract. Install a descreened 85mm MAF. The MAF is usually not our restriction problem. The throttle body is usually the pinchpoint.
Again, this brings me back to my original claim that I have yet to see a GOOD reason for running these things MAFless.
For very large cam setups I run a hybrid combination of MAF and VE tuning. It works well. You can get the very large cams to idle at the lower RPMs and you don't have the side effects that you get with SD tuning.
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From: Dallas
Originally Posted by binksz06
It wouldn't be a proportional % VE adjustment running through the MAF. I just wanted to know the relationship - i.e. percentage increase and percentage adjustment. Thanks!
joel
joel
Edit: I don't want to mislead anyone. This was in one or two load ranges on my vehicle. The 3 to 1 ratio may not apply to a different vehicle. Always use your own log results to make tuning changes.
Last edited by deezel; Feb 12, 2004 at 08:21 PM. Reason: disclaimer
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VE Table To No Go,I have had great success tuning with the MAF.Now I hear adjusting the VE tables are another area for fine tuning.I have not used these tables as of yet.There are a few VE tables main ve ect.Which table if all do you get into and at what percent or numeric value do you start with? Thanks for the info........
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Verdad Gallardo TECH Addict
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Originally Posted by deezel
When I played with big VE changes I observed that a 3% VE change made about a 1% change in fuel trims. The maximum VE change I tried was about 10% increase. cheers
joel
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From: Dallas
Originally Posted by binksz06
Thanks deezel - so we'd expect a 12% increase of VE (over stock VE) for HumpinSS as he increased his Flow by 4%.
joel
joel
I may have seen a 3 to one ratio for one particular load range, but I really haven't studied the relationship (VE to LTFTs) well enough to say that will apply to anyone elses vehicle. I'd suggest some careful logging before changing the VE table by more than 10% or so...
Sorry for the confusion...
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From: Dallas
For those who were following this thread... I think I can explain why the change in my LTFTs did not match the change in the VE table.
When I edited my VE table I only changed some of the values in various Fuel Trim Cells. Since I did not increase the entire FTC range in the VE table, the full effect of my change was not seen in the fuel trims. I think this explains why I saw a 1% LTFT change - because I only increased part of the cell by 3%.
I imagine if you scaled the entire FTC range on the VE table, it would come close to the same percentage change in LTFTs. Hope this helps...
When I edited my VE table I only changed some of the values in various Fuel Trim Cells. Since I did not increase the entire FTC range in the VE table, the full effect of my change was not seen in the fuel trims. I think this explains why I saw a 1% LTFT change - because I only increased part of the cell by 3%.
I imagine if you scaled the entire FTC range on the VE table, it would come close to the same percentage change in LTFTs. Hope this helps...
