Linear MAP-MAF Relationship......and CC503 bucking.
08-26-2010, 11:27 PM
#1
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Join Date: Mar 1999
Location: Kernersville, NC
Posts: 2,060
Linear MAP-MAF Relationship......and CC503 bucking.
In reading tonight, I have learned that there is roughly a linear relationship between MAP and MAF(airflow). When plotted at a certain RPM, it yields a straight line. So with that, I plotted the Main VE tables from my CC503 tune and the stock tune. Something interesting popped up.
Look at the nice roughly linear relationship of the stock tune compared to the CC503 tune. Notice that area between the red arrows. Those are the 400, 600, 800, and 1000rpm points. Notice how it's constant or flat right there.....this could be why I'm bucking on tip in. The fuel delivered is constant and not increased as needed when tipping in part throttle. Many have described my bucking as what sounds like a lean problem and that may be it. It clears up once I get around 1500rpm. I generally have to really give it throttle or clutch in to stop it from bucking....can't do any part throttle driving down low.
I'm hoping, if I make these areas more linear(with each line slightly above the other) that it will clear up the part throttle issues. There may be some other transitional tables I will need to tweak, but I think the above is a good start. There also looks to be some wacky stuff going on in the 1400rpm range @ 60kpa.
I've also noticed a mistake on the Main VE and EXT VE tables. Both of these tables have 2000 RPM in the table. On the stock table, both 2000 RPM lines match....on the CC503 tune they do not....so I'm going to change that. I have not noted any problems around 2000rpms, so it may not be a big deal.
Look at the nice roughly linear relationship of the stock tune compared to the CC503 tune. Notice that area between the red arrows. Those are the 400, 600, 800, and 1000rpm points. Notice how it's constant or flat right there.....this could be why I'm bucking on tip in. The fuel delivered is constant and not increased as needed when tipping in part throttle. Many have described my bucking as what sounds like a lean problem and that may be it. It clears up once I get around 1500rpm. I generally have to really give it throttle or clutch in to stop it from bucking....can't do any part throttle driving down low.
I'm hoping, if I make these areas more linear(with each line slightly above the other) that it will clear up the part throttle issues. There may be some other transitional tables I will need to tweak, but I think the above is a good start. There also looks to be some wacky stuff going on in the 1400rpm range @ 60kpa.
I've also noticed a mistake on the Main VE and EXT VE tables. Both of these tables have 2000 RPM in the table. On the stock table, both 2000 RPM lines match....on the CC503 tune they do not....so I'm going to change that. I have not noted any problems around 2000rpms, so it may not be a big deal.
08-27-2010, 02:19 AM
#3
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Join Date: Oct 2001
Location: Engineerland
Posts: 1,517
If its the car in your sig you're talking about, you're looking in the wrong place. The ve tables do jack and **** in a car with a functioning maf. Are properly tuned up ve tables part of a complete tune? Absolutely. They're there for the time when you're crusty old wiring harness loses a pin or your maf fouls etc and you can still get home on the ve tables. If you're just playing with the ve tables or trying out speed density mode then fine you may have some valid point. I will however say that having a smooth ve table is not a MUST HAVE with a modified car that has some reversion.
Ignition timing is going to have more effect than you can ever imagine on tip in. Take a peak at where you're sweeping through on tip in and how well shaped the advance rise is in that area. It better be above or equal to where you were in the previous cells when you tip in or its going to fall on its face. That may mean removing and adding timing to the table
Your other thread on the injector offsets while interesting is going to have minimal effects on the performance of the engine. The difference in response to voltage inputs is going to be very similar between the new injectors and the old stockers. The importance of the offset tables is getting the engine started when the starter is sucking all the available energy from the battery and voltage sags dramatically.
Ignition timing is going to have more effect than you can ever imagine on tip in. Take a peak at where you're sweeping through on tip in and how well shaped the advance rise is in that area. It better be above or equal to where you were in the previous cells when you tip in or its going to fall on its face. That may mean removing and adding timing to the table
Your other thread on the injector offsets while interesting is going to have minimal effects on the performance of the engine. The difference in response to voltage inputs is going to be very similar between the new injectors and the old stockers. The importance of the offset tables is getting the engine started when the starter is sucking all the available energy from the battery and voltage sags dramatically.
09-09-2010, 02:20 PM
#4
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Join Date: Feb 2004
Posts: 674
How did you obtain the VE tables for your 503 cam?
I am interested because I would like to run speed density off the VE tables.
I generated some VE tables for my LE3.2 cam in the past, but with an auto you dont get to run in all the possible MAP/RPM cells.
I am interested because I would like to run speed density off the VE tables.
I generated some VE tables for my LE3.2 cam in the past, but with an auto you dont get to run in all the possible MAP/RPM cells.
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