Taking SD tuning to the next level....
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From: Port Tobacco, MD
Taking SD tuning to the next level.... I have always wondered how to integrate the VE throttle table into my tunes and think its time to figure it out. The motor is a 346 with high compression and a 254/260 solid roller camshaft, when it idles the map values are very high ~75kpa very close to when my setup is changing from 14.7 to 13.0. It idles great but if it dips it has a tough time recovering because the computer is setup for 13.0:1 @ 80kpa and above. The throttle table would add a way to fine tune the combo. I am almost thinking from 400 - 1200 tune it to 14.7 so idle is dead on, when doing PT tuning @ 1000 - 1200 use the throttle modifier to correct the A/F which is different than when idle 1000 - 1200. Very little throttle input will send the MAP from 75 to 100kpa. Any input is appreciated.
Phil
Phil
That should work just fine...get the VE table in line, and then set up a custom histogram that mimics the VE Mult vs. RPM vs. TPS table, and do another iteration of AFR % Error. I do that on my bolt-on car, and it seems to work just fine.
You running SD? OL? CL?
I'm not exactly sure what you mean by VE throttle table... maybe something I've overlooked.
I did want to point out that if you mean when you say the idle dips, that the RPM drops and the MAP increases, then you could probably just catch the problem in your VE table by changing just that particular cell it drops to, to match your normal idle cell, and of course the spark advance would be duplicated as well to keep things more stable.
Anyway if the RPM does drop during your dip in idle, then you could possibly fix that area of the VE without harming your PT area.
I'm not exactly sure what you mean by VE throttle table... maybe something I've overlooked.
I did want to point out that if you mean when you say the idle dips, that the RPM drops and the MAP increases, then you could probably just catch the problem in your VE table by changing just that particular cell it drops to, to match your normal idle cell, and of course the spark advance would be duplicated as well to keep things more stable.
Anyway if the RPM does drop during your dip in idle, then you could possibly fix that area of the VE without harming your PT area.
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From: Port Tobacco, MD
It can be corrected but I want it to be 100%. The car idles right now ~1000 so the ve table jumps between 800 and 1200. Once fueling is correct for idle and I tune 1200 PT to WOT the fuel is incorrect add the correct amount and now idle is off. I guess I need to tune 400-800-1200 for 14.7(idle) and use the throttle position modifier to correct while driving. Make sense?
I don't see an advantage to doing it myself, but I can see it could work.
I wouldn't think you could ever get to 800 RPM or less without having the throttle closed. I see more resolution for fixing the problem on the VE, but that's just me.
I wouldn't think you could ever get to 800 RPM or less without having the throttle closed. I see more resolution for fixing the problem on the VE, but that's just me.
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Originally Posted by MeentSS02
I would add extra resolution to the tune, since they work in tandem.
Good point, but I'd have to see what a histogram of his looks like for the VE table while it is idling. If the MAP values are jumping around a lot, it'd be tough to get the VE table to do exactly what he needs at idle. Having an idle of 1000 doesn't help either (as it jumps back and forth between the 800 and 1200 cells)...
Hell, I don't know. Either way, it is a tough problem that I simply don't have, so pure conjecture is the best I can come up with.
Hell, I don't know. Either way, it is a tough problem that I simply don't have, so pure conjecture is the best I can come up with.
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From: Port Tobacco, MD
I am going to try to retune it tonight. With a cam this big in a 346 the MAP values are very high @ low RPM. I've got roughly 6 cells to work with between 800 and 1600 rpm where you have 12 from the factory. Adding the VE/TPS multiplier will make it so I have 20 steps of tuning at the low RPMs, basically more fine tuning. I guess the way I am seeing it is I am going to have 3-7 sub tables for each kpa.
Sorry I had it backwards. At first it sounded like your PT was okay, but you were trying to fix the dipping idle problem by using the TPS vs VE.
Sounds like it may work really well for increasing your PT resolution.
Sounds like it may work really well for increasing your PT resolution.
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Its tough, its a combo of both here's my thought
Tune VE @ 800 and 1200 to 14.7
- will take care of any dips in idle, dips now in idle command 13.0:1 A/F which is tough for a big cam to recover from....
Use TPS to correct A/F to 13.x for PT.
Idle won't go rich if it stumbles and will add fuel for PT to WOT transition...
0 - 75% would command 1.00 and 75% to 100 would multiply the VE by 1.13
Tune VE @ 800 and 1200 to 14.7
- will take care of any dips in idle, dips now in idle command 13.0:1 A/F which is tough for a big cam to recover from....
Use TPS to correct A/F to 13.x for PT.
Idle won't go rich if it stumbles and will add fuel for PT to WOT transition...
0 - 75% would command 1.00 and 75% to 100 would multiply the VE by 1.13
Last edited by Phil99vette; Mar 28, 2006 at 01:34 PM.
That's another option as well. There's so many ways to do the same thing.
Phil, about your idle with the huge cam...
Consider that a big cam will pass a lot of oxygen out the exhaust even when the A/F is very good while burning in the chamber. This means your ideal A/F as reported by your wideband in the exhaust will actually be leaner than 14.7 as you see it displayed.
I would try something closer to 15.5 AFR as displayed by your WBO2 and you'll have some more room to cushion those dips. It may clean your idle up a bit.
I'm not sure what kind of advance you run in idle mode, but big cams generally like a lot. Something over 30* wouldn't surprise me at all with your size cam.
If the idle cleans up enough you may be able to drop it closer to 800.
Phil, about your idle with the huge cam...
Consider that a big cam will pass a lot of oxygen out the exhaust even when the A/F is very good while burning in the chamber. This means your ideal A/F as reported by your wideband in the exhaust will actually be leaner than 14.7 as you see it displayed.
I would try something closer to 15.5 AFR as displayed by your WBO2 and you'll have some more room to cushion those dips. It may clean your idle up a bit.
I'm not sure what kind of advance you run in idle mode, but big cams generally like a lot. Something over 30* wouldn't surprise me at all with your size cam.
If the idle cleans up enough you may be able to drop it closer to 800.