system lag?

[howracer]

perhaps this has been addressed and i will do a search but would like to hear some comment:

since our systems (mine is Alkycontrol) are generally manifold pressure actuated it would seem that between shifts and into the beginning of the next gear they could run lean while the system catches up. i have not experienced this but have only been doing 3rd gear pulls and tuning so far.

offsetting the boost drop might be pump momentum run-on... if it exists???

here is a typical question (from an EVO board) on the subject:

EVO forum
i have a progressive kit and i can tune(AEM) it in 4th gear and make the afr's hold very consistent, but when i do a pull in 1st, 2nd or 3rd the afrs are all wacked. it usually goes lean for about a second(14-15afr) coming into boost. kinda seems the pump isn't keeping up the volume when the engine accelerates faster in the low gears. is there anything i can do? I'm about to use an on/off setup. is there an accel enrichment that might work? thanks everyone.


here is a reply from an Aquamist engineer:

I don't think you are going to be able to solve your afr problem that easily.

If your progressive system is manifold pressure driven and made no reference to RPM and Gear position, you won't be able to get a consistant afr in all gears.

Assuming you have all the above inputs, if the AI pump speed is not responding fast enough to your load change, you will always have a afr gap.

I suggest tuning your progressive kit over-rich at 4th gear and hope the lean condition disappears at 1st, 2nd, 3rd gear pull.

I have mentioned this problem tuning a progressive system before on this forum
and I suggested the a fix delivery rate (on/off) system gave less tuning problems.

This is just my opinion of your present situation and I am not bashing the concept of a progressive kits against an on/off system. Please do not take it as such.



i would be delighted to hear comment.

thanks,

howard coleman

 

[Grumpy]

ummmmm we have automatics I run Julio's ALKY kits and never miss a beat

 

[PhilM]

The only way to adjust this is to change the slope or even better... the shape... of the injection slope. The latter is only possible in very application specific systems since adjusting the curve shape would depend on so many factors ESPECIALLY when you have a manual tranny. This is why I dont put curve shape as a user adjustable control. Slope changes can compensate to a degree for this but in general setups, tuning has to be done to ensure no lean which means overshooting. How much overshoot is related to how good the curve shape already matches the requirement and how well it is tuned.

As far as secondary inputs... well then you have a more expensive kit. This would have to become closer to an acutal ECU which does enrichments based on 'fast moving' sensors such as TPS not MAP. Would people pay for such a system? Probably not.

Phil

 

[Razor]

perhaps this has been addressed and i will do a search but would like to hear some comment:

since our systems (mine is Alkycontrol) are generally manifold pressure actuated it would seem that between shifts and into the beginning of the next gear they could run lean while the system catches up. i have not experienced this but have only been doing 3rd gear pulls and tuning so far.

offsetting the boost drop might be pump momentum run-on... if it exists???

here is a typical question (from an EVO board) on the subject:

EVO forum
i have a progressive kit and i can tune(AEM) it in 4th gear and make the afr's hold very consistent, but when i do a pull in 1st, 2nd or 3rd the afrs are all wacked. it usually goes lean for about a second(14-15afr) coming into boost. kinda seems the pump isn't keeping up the volume when the engine accelerates faster in the low gears. is there anything i can do? I'm about to use an on/off setup. is there an accel enrichment that might work? thanks everyone.


here is a reply from an Aquamist engineer:

I don't think you are going to be able to solve your afr problem that easily.

If your progressive system is manifold pressure driven and made no reference to RPM and Gear position, you won't be able to get a consistant afr in all gears.

Assuming you have all the above inputs, if the AI pump speed is not responding fast enough to your load change, you will always have a afr gap.

I suggest tuning your progressive kit over-rich at 4th gear and hope the lean condition disappears at 1st, 2nd, 3rd gear pull.

I have mentioned this problem tuning a progressive system before on this forum
and I suggested the a fix delivery rate (on/off) system gave less tuning problems.

This is just my opinion of your present situation and I am not bashing the concept of a progressive kits against an on/off system. Please do not take it as such.



i would be delighted to hear comment.

thanks,

howard coleman

Howard, There is a lot more going on. Perfect example is TPS AE, MAP AE. Whereby the computer shoots fuel in when you stab the throttle. Kinda like a carb has a pump shot. If your gears are very short and you punch it.. getting this stuff dead on is tough. Most 4 cyl racing engines in first gear are useless. And I would doubt there is any engine that tunes out perfectly under all conditions. AEM or not. As the common is run them a little richer.

Now if the boost goes up on a VE table. Its going to hit a cell that is based on RPM and KPa(boost). It will hit that spot on the table whether in 1st or 4th gear. So if the alky is 10 percent on the VE number on that table.. you have your issue with or without the alcohol.

Water is more so a problem. And the ability to tune out an engine in 1st gear. Vs 4th which allows a way longer pull to be made.

The injection pumps are slow moving devices in the scheme of things. They all are. And delays are inherent no matter how you do this. Due to distance from nozzle to combustion chamber. If I were to get closer, I would do individual MAP per gear. You shift... goes to a different MAP.. different VE to compliment the circumstances.

Think the Aquamist engineer needs to study a little more bout EFI

Us with automatics.. non-issue.

 

[bison]

I always found it better to overshoot the alky and create a slightly rich condition in 1st on spoolup. Its much safer and then you still have the ability to take a little fuel out of 1st with one of Eric's chips. You dont need to go excessively rich, just enough to prevent a mis-fire or detonation. The engine will tolerate a little leaner a/f ratio in 1st as the cylinder isnt all heated up yet from the long blast at WOT. If you were building boost and launching at a very high boost level you could simply raise the turn-on point to rpevent the rich condtion building boost. At this point it will usually spool from 10-15psi to 25-30 psi in less than half a second anyway. I have never noticed a problem between gears as i have an automatic like almost everyone else on here. Between a system like Julio's and a chip burner like Eric you can take a stock TR and plunge it into the low 12's in under a day with a set of slicks. Those that bash alky and say its just another tuning variable are the ones who never tried it . The problem is, is that it works almost too well.