Vta Map Issue?

[SSinstaller]

I've been running a modified version of franchize's dyno tuned map with no issues until I added the VTA settings this afternoon. I copied all the -81 fuel settings and the fuel cut settings into my map. Is that the correct way to add the VTA function to my map?

I'm not getting any horrible backfires, so I'm pretty sire the vta settings are working, but I have a weird issue with light throttle inputs. If I gradually get into the throttle at around 2200~2600 rpms I sometimes get stuttering and my AFR goes WAY lean(my guage shows 35~50 to 1). I can apply a little more throttle and it goes right back to running fine at normal afr's.

It seems like I must be running through a part of the tune where the standback is trying to pull out fuel for the VTA function, but really don't know how to adjust the VTA settings to eliminate this.

Any help you could give me would be appreciated. If some data logs would help, just let me know what I should log and I'll go make them. At least it's only happening at light throttle so it can't cause any serious damage while I make some logs to try and figure out how to fix it.


***EDIT

I just read through dadasracecar's thread about his studder and I pretty certian that this is a seperate issue. I only get the stutter right after I shift and the BOV vents, and even then it only happens if I gently roll into the throttle. I'm not 100% sure how the VTA function works, but I assume that it cuts fuel and then waits to see a TPS greater than some set voltage to start the fuel up again, I think in my case that voltage is just set a litle too high for my driving style. I roll lightly in to the throttle, but don't excede the TPS voltage the standback is looking for to restart the fuel, so I go super lean and studder...

[Dadasracecar]

Get a buddy to ride along with you and watch where your tps-rpm sensor (little red dot that moves around the fuel and timing matrices) is reading when you get the stutter. If it's in the -81 sections that's where you'll see the lean conditions b/c your cutting fuel. If it's the fuel cut then there should be no damage as there is no fuel. 35 - 50:1 seems to indicate this.

[SSinstaller]

Get a buddy to ride along with you and watch where your tps-rpm sensor (little red dot that moves around the fuel and timing matrices) is reading when you get the stutter. If it's in the -81 sections that's where you'll see the lean conditions b/c your cutting fuel. If it's the fuel cut then there should be no damage as there is no fuel. 35 - 50:1 seems to indicate this.[/b]

Will do that tomorrow, I just wish I had a better idea what the fuel cut settings on the boost control tab do.

[Dadasracecar]

I'm not sure what the fuel cut volts box does but the fuel restore tps voltage is where the fuel is restored. If it's too low, you'll never hit fuel cut because the TPS is always something. If it's too high, you'll have to depress the throttle significantly to restore fuel.I'm not sure what the fuel cut volts box does but the fuel restore tps voltage is where the fuel is restored. If it's too low, you'll never hit fuel cut because the TPS is always something. If it's too high, you'll have to depress the throttle significantly to restore fuel.

[Gandalf]

My guess would be fuel cut volts would be the MAF voltage.

[SSinstaller]

Got it pretty much figured out today.

I ended up removing all of the -81 values below 3000 rpm. It's still backfire free and I get the only get the studder about 1 in 25 shifts--it used to happen just about every other shift(after a BOV vent). I think lowering the fuel restore voltage a couple tenths of a volt should get it perfect, but I'm going to wait until I talk to someone at CP-E before I adjust it..

[www.cp-e.com]

Got it pretty much figured out today.

I ended up removing all of the -81 values below 3000 rpm. It's still backfire free and I get the only get the studder about 1 in 25 shifts--it used to happen just about every other shift(after a BOV vent). I think lowering the fuel restore voltage a couple tenths of a volt should get it perfect, but I'm going to wait until I talk to someone at CP-E before I adjust it..[/b]

You see, this is why I love this community. The options in the Boost Settings tab are pretty cryptic, but you figured it out anyway.

I've been a part of several car communities, and not one had this much collaboration and cooperation. Its just cool to see everyone helping each other and collectively trying to improve this car. Anyway, I'll shut up now and answer your question...

You're on the right track, and what you need to do now is adjust those voltages so that you don't trigger a fuel cut inadvertantly. Now let me ask you, are you getting this false trigger after a shift, or is this happening when you get back on the throttle after cruising for a bit?

[SSinstaller]

You see, this is why I love this community. The options in the Boost Settings tab are pretty cryptic, but you figured it out anyway.

I've been a part of several car communities, and not one had this much collaboration and cooperation. Its just cool to see everyone helping each other and collectively trying to improve this car. Anyway, I'll shut up now and answer your question...

You're on the right track, and what you need to do now is adjust those voltages so that you don't trigger a fuel cut inadvertantly. Now let me ask you, are you getting this false trigger after a shift, or is this happening when you get back on the throttle after cruising for a bit?[/b]

I've only ever noticed it after a shift. Generally it happens when I accelerate at WOT in fourth and then shift into 5th and just ease into the throttle to maintain a steady speed. I have a lead foot so I find myself doing that alot... to aviod tickets... If I pay attention and let the rpms fall a little more during the shift and use more throttle when I enter fifth it doesn't happen. Would lowering the fuel restore voltage a little help stop this completely? I was thinking about lowering in .1v increments until I stopped having the studder, and then gradually adding back in some of the -81 values I removed to stop some minor lower rpm popping.


I also had a question about the -81 values: Does the standback use those values during normal driving or are they only used as part of VTA function? I ask because the instructions say it is only capable of adjusting the stock maps by plus or minus 80%, and a value outside the expected range stored in the fuel map(in a location unlikely to be used otherwise) would be a good way to store the VTA settings without using additional memory in the standback. I remember you saying that the current standback hardware is out of memory so no additional expansion is possible.

I'm going to give you a call tomorrow with a few questions, as I don't want to sit here and type a novel worth of questions for to you to read and answer...

****EDIT

Fuel restore setting at .9v and the studder is completly gone!!