How to get rid of this darn sag...

[TurboJim]

Drove the car about today, you know, to keep the juices flowing. Hadta get the laptop out cuz this darn sag I have. Figered I'd give it a shot again today.

Couple things helped, adding timing mainly, but theres one thing I dont like...

This is a stock long block and Delphi 65's mind you...

Idle VE values are in the mid to high 30's and the area where it sags needs upwards of 50-60 to minimize the sag. I didnt go any further due to the though I was getting too far away with it but, putting the car in closed loop from 900rpm took care of it. I n open loop I noticed when its sagging, actual AF goes to 15+:1 then in closed loop the correction goes to 25% and it doest sag anymore. Now, going back to the VE tables, the high 50's in the few cellls where its sagging brings the corrections down to 10% or so, so I know it needs more fuel there, but being its a stock long block I just cant see why? Could it be a combination of the engine starting to breath and the injectors characteristics dictates that as a lean spot? I know 50's are a little lean at 7mS, I dont know about these 65's.

Anyone have a solution to this they want to share, or should I just keep going up as needed with the few VE cells and disregard the actual values, so long as correction is minimal?

Advice-suggestions?

 

[RickWI]

I never try to argue with what the computer says the motor wants. So I give it what it wants. 50-60 VEs don't seem out of line to me.

 

[TurboJim]

Originally posted by RickWI
I never try to argue with what the computer says the motor wants. So I give it what it wants. 50-60 VEs don't seem out of line to me.

JUst off idle, where the idle cell is like 38?

I kinda agree with ya tho, the ECU knows best

 

[Spooled]

If I've learned one thing, it's this....GIVE IT WHAT IT WANTS!

 

[bobc455]

50's don't seem outlandish to me. Your RPMs are still fairly low, so if you look at your injector DC it will still be very low.

Remember that your motor is now under load instead of idling.

-Bob Cunningham
bobc@gnttype.org

 

[bruce]

Originally posted by TurboJim
I know 50's are a little lean at 7mS, I dont know about these 65's.

Oh really?.
I one time I got to look at fair bit of injector flow charts at short pulse widths, and the only real problem ranges were as you got to really short PWs, ie under about 1.5 msec. While injectors can suffer from not being perfectly linear, if you study the charts it really ain't no big deal.

If changing the fuel doesn't get you what you want,
change the timing.

Remember, you want to spool the turbo, not necessarily to make serious boost, but to get it spinning. At low speeds like idle the turbine is just loafing along, so when you want to get the engine to acclerate, you also want to ask the turbo to start to spool.

Just as a clue,
I run more timing at idle then anywhere else in the map.

Anymore and I'd have to shoot you......

 

[TurboJim]

Re: Re: How to get rid of this darn sag...

Originally posted by bruce
Oh really?.
I one time I got to look at fair bit of injector flow charts at short pulse widths, and the only real problem ranges were as you got to really short PWs, ie under about 1.5 msec. While injectors can suffer from not being perfectly linear, if you study the charts it really ain't no big deal.

Yes really. When I first put the 50's in my car, I got a flow sheet from PTE on them. They flowed ~67% more than stock, except for ~6-7mS where they flowed 50something more than stock. 10% at low RPM is a lot... and it shows in the cold start

If changing the fuel doesn't get you what you want,
change the timing.

Yes, that helped a lot, although it got to the point it backfired out the exhaust. LIke I said, just touching the gas the AF went to 15:x:1 and I think that lean, in combination of the added load and the extra timing caused it. Once I got the AF in the 13's it stopped doing that. My timing at idle and off idle is 30-33*. It also changed how the car spools. I set the timing table up at the MAX without retard all the way from vacuum to boost. I did however pull a few degrees where the turbo STARTS to spool to raise EGT. Could never get my chip to spool like this, although my chip ran MUCH better. Guess there is a tradeoff...I hate that. The car runs VERY well using closed loop at idle, its just that the off idle correection had me concerned since people here seem to be concerned with the VE values, Mine were pretty high for such a low RPM/load area, I too was concerned.

Remember, you want to spool the turbo, not necessarily to make serious boost, but to get it spinning. At low speeds like idle the turbine is just loafing along, so when you want to get the engine to acclerate, you also want to ask the turbo to start to spool.

Just as a clue,
I run more timing at idle then anywhere else in the map.

Anymore and I'd have to shoot you......

Yes, I run more timing there too....

Dont shoot me, I'm only the piano man.....

 

[bobc455]

I think you've had this problem for a while now-

Please refresh me, I assume you've played with the AE (vs. TPS and vs. MAP)? It sounds to me like you might be putting in high VE numbers to compensate for a lack of AE.

What about your AE Fuel vs. TPS position table - do you go negative on there?

Also, is your TPS indicating properly (can be checked w/ engine off)?

-Bob Cunningham
bobc@gnttype.org

 

[bruce]

Re: Re: Re: How to get rid of this darn sag...

Originally posted by TurboJim
Yes really. When I first put the 50's in my car, I got a flow sheet from PTE on them. They flowed ~67% more than stock, except for ~6-7mS where they flowed 50something more than stock. 10% at low RPM is a lot... and it shows in the cold start


Yes, that helped a lot, although it got to the point it backfired out the exhaust. LIke I said, just touching the gas the AF went to 15:x:1 and I think that lean, in combination of the added load and the extra timing caused it. Once I got the AF in the 13's it stopped doing that. My timing at idle and off idle is 30-33*. It also changed how the car spools. I set the timing table up at the MAX without retard all the way from vacuum to boost. I did however pull a few degrees where the turbo STARTS to spool to raise EGT. Could never get my chip to spool like this, although my chip ran MUCH better. Guess there is a tradeoff...I hate that. The car runs VERY well using closed loop at idle, its just that the off idle correection had me concerned since people here seem to be concerned with the VE values, Mine were pretty high for such a low RPM/load area, I too was concerned.

Timing as I do it drops immediately off idle.

Can you email me a copy of that flow sheet?. I've just not seen an injector go that far out.

15 ain't good for anything but overrun, and possibly an indicated AFR at idle. EGR and timing can screw with the idicated AFRs.

You really need a WB...

 

[TurboJim]

No, this is something, well, not new, but the next thing to address I guess you'd say.

The FAST to me has been a decent learning curve, but I think Im getting it.

This new condition is for example, you're pulling away from your driveway slowly to avoid hiutting the curb say...just maybe 3% throttle, the engine goes vrrrraaahhhwww plplplplplaahhhhplplplaahhhplllll (nice sound effects right?) point is is kinda just lean sags...kinda like opening the EGR valve too early, but my WGR isnt functinoal anymore so it aint that

I have my tip in perfect, I can tap the pedal to stabbing it WOT and theres no hiccup at all. LIke I said, putting the car in closed loop iat 900rpm instead of 1500 how I had it gets rid of the sag totally, but corrections go to 22-23% telling me at that spot the car goes REAL lean. I've checked for ported vacuum line leaks and have found none, so itsa either a characteristic of the engine or injectors. I think its the injectors cuz it didnt do this with the 50's

 

[TurboJim]

Re: Re: Re: Re: How to get rid of this darn sag...

Originally posted by bruce

You really need a WB...

I have a WB. Its part of the system. Thats how I knew it was going upwards of 15:1

I hope you dont think I'm that much a fool I'd be taking the word of a NB sensor......15;1 could be 18:1 in that case

 

[Red Supra]

I seem to have the same problem, let us all know if you figured it out. I will try to messing with it some more when the new trans comes. I think i have to play with one of those AE tables.

Max
93 Supra turbo