747 computer question.
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Junior Member
Joined: May 2006
Posts: 2
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From: Catlettsburg, Ky
747 computer question.
Do the 747's do VE table cell interpolation or do they just use the VE value for the nearest cell?
The reason I ask is on bigger cam applications (large difference in VE at 800 compared to 1200) I have trouble transitioning in the low rpms. For example lets say i've got my wide band hooked up and I'm to this point shooting for 14.0.
800 RPM / 50KPA - AFR 14.0
900 RPM / 50KPA - AFR 15.0
950 RPM / 50KPA - AFR 16.0
1000 RPM / 50KPA - AFR 12.0
1100 RPM / 50KPA - AFR 13.0
1200 RPM / 50KPA - AFR 14.0
It's like the injector PW is the same till 999 then changes to the next cell at 1000. The fact that its rich after 1000 dosen't bother me, its the fact that its lean enough it dosen't want to run before the change. The only fix I have is to make the table cell for 800/50 overly rich so it dosen't lean out before 1000. I just found out today how to log the PW via ALDL thanks to your site and havent done it yet. If I can log the PW I assume I can see if that is whats happening.
My personal truck with a 747 running a MPI setup on a dakota (don't laugh
) and another big cammed 91 1500 with a 747 have the same problems. I just did a 93 2500 with a big cam last week ($9A) and its tuned flawless. Had a perfect ve table in 2 trips down the road, acted completely different then the $42 trucks. It had a single VE table (no adder) and was easier to work with, but the table only goes to 4800 and I need the 747's 6400 table for my app. If interpolation is the problem, is thier a computer that dose that and still has the bigger rpm capability?
The reason I ask is on bigger cam applications (large difference in VE at 800 compared to 1200) I have trouble transitioning in the low rpms. For example lets say i've got my wide band hooked up and I'm to this point shooting for 14.0.
800 RPM / 50KPA - AFR 14.0
900 RPM / 50KPA - AFR 15.0
950 RPM / 50KPA - AFR 16.0
1000 RPM / 50KPA - AFR 12.0
1100 RPM / 50KPA - AFR 13.0
1200 RPM / 50KPA - AFR 14.0
It's like the injector PW is the same till 999 then changes to the next cell at 1000. The fact that its rich after 1000 dosen't bother me, its the fact that its lean enough it dosen't want to run before the change. The only fix I have is to make the table cell for 800/50 overly rich so it dosen't lean out before 1000. I just found out today how to log the PW via ALDL thanks to your site and havent done it yet. If I can log the PW I assume I can see if that is whats happening.
My personal truck with a 747 running a MPI setup on a dakota (don't laugh
) and another big cammed 91 1500 with a 747 have the same problems. I just did a 93 2500 with a big cam last week ($9A) and its tuned flawless. Had a perfect ve table in 2 trips down the road, acted completely different then the $42 trucks. It had a single VE table (no adder) and was easier to work with, but the table only goes to 4800 and I need the 747's 6400 table for my app. If interpolation is the problem, is thier a computer that dose that and still has the bigger rpm capability? 
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iTrader: (1)
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Posts: 18,432
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From: Chasing Electrons
Car: check
Engine: check
Transmission: check
The '7747 does a 16-point linear interpolation between cells. However, as you have found out even that isn't enough for a cam'd engine. You can convert the '7747 to something better (much better), see my sig.
RBob.
RBob.
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iTrader: (1)
Joined: Mar 2002
Posts: 18,432
Likes: 233
From: Chasing Electrons
Car: check
Engine: check
Transmission: check
Originally Posted by Bluecat
I wander into your link earlier today when I was on here. Looks promising. I never saw a price or way to order. If I want to go that route, what do I do?
RBob.
its all in your tunning and how you use the parameters you do have. 
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