Question here about Minirams and pump shots. My lower VE table is fairly close right now. In open loop, my throttle responce is crisp and instant. The minute it goes into closed loop, it gets a little sluggish and less responsive. During driving, the higher the load placed on the motor from a closed throttle position, the worse the stumble. O2 volts drop way down then recover. All signs point to more pump shot. My quesiton is on the table itself. One the left side, there is a TPS colum and the other a multiplier. The table is listed as Pump shot vs differential TPS. Is this the added fuel vs a change in TPS? Since the first multiplier is is 100, does that mean the the pulse width is doubled from an off idle throttle movement?

If anyone can list their pump shot table values from a Minram car (Trax?)that I can use as a guideline, I'd appreciate it.

Thanks

 

I have looking and thinking about that table and I believe it is the "starting" position of the sensor; ie if you are starting from a lower TPS setting then it gives a bigger pump shot.

The title "Differential" means "change" from what I've seen in other tables that use this reference. A differential of 0% does not make any sense. But if 0 means the starting point of the TPS when a pump shot is needed, then it does make sense that this should have the largest pump shot. It also explains why that table is maxed at 50%.

Given your setup, (SBC 396, Miniram, etc), I think a little extra pump shot is worth trying. Do it in small increments though. Based on your testing, you should see the results fairly quickly.

 

Do you think I should adjust all the values or just the lower ones. Do you remember that one bin we looked at that had 100% values fo rthe first three rows?

Jason

 

I tried to get a definite answer to this question a long long time ago. I made a post here ....
https://www.thirdgen.org/messgboard/...ML/000074.html

I also posted to GMECM and searched the archives. I could NOT find a definite answer that *truly* explains the operation of this table. What I can tell you is that I increased the values and the stumble is gone. I think I used a 25% increase across the board.

Glenn - I am not following your comment regarding the "starting" position of the sensor. How does that explain why the table is maxed at 50%? If I start from 0% TPS and then go to WOT (100%) then isn't the Delta TPS = 100?

Tim

------------------
TRAXION's 1990 IROC-Z
Best Time = 12.244 @ 112.51mph (1.778 60' / 7.819@88.32mph in the 1/8)
All Natural. No Force. No Drugs. Stock Bottom End. Stock Body Panels.
Gunning for NA 11's with bigger cam, bigger stall, and bigger exhaust.
-=ICON Motorsports=-
Moderator: PROM board at thirdgen.org

 

Tim, I am suggesting that possibly 0 means the starting TPS setting to go PE. This would explain the 100 Multiplier for 0 as this indicates the "richest shot"...or so I have found.

At 50, I suspect that if you are at 50 (or higher) %TPS, then you get that multiplier which seems to be the leanest.

Some of these tables behave a little weird. The "Inverse MAT Term Lookup Delta Multiplier vs Air Flow" is a great example. To lean the engine, you increase the Multiplier value, and to richen it, you decrease the Multiplier value. They work opposite to what you would normally think it shoud be.

The difference I note with this table is that it is not referred to as a "Delta Table" and they don't use "Inverse"...which I have found to mean "do the opposite".

 

Interesting thoughts Glenn. Hmmmmm. I understand where you are going with this but there is one thing that doesn't "fit" for me. The 0, 3.1, and 6.3 %TPS values all have 100 as the multiplier. I didn't change these values in the table (obviously) but changed the other values. However, I did notice via my AFR guage that the at very low throttle I have more of a pump shot. I guess I could have been greater than 6.3% when I blipped the throttle but I don't think that I was. Hmmm. I guess this is something that I have to check. Also - as a side note - I didn't change my table values by 25%. I scaled them by around 50% ... give or take.

Tim

------------------
TRAXION's 1990 IROC-Z
Best Time = 12.244 @ 112.51mph (1.778 60' / 7.819@88.32mph in the 1/8)
All Natural. No Force. No Drugs. Stock Bottom End. Stock Body Panels.
Gunning for NA 11's with bigger cam, bigger stall, and bigger exhaust.
-=ICON Motorsports=-
Moderator: PROM board at thirdgen.org

 

When I played with my Pump Shot for my basically stock L98, I found it needed less of a pump shot. But, that kind of follows with my whole experience with AUJP; I found it to be richer all over and very conservative on the spark. I am stilling playing with that table myself.

Right now I am analyzing info on my new Knock Sensor. I think I may have some information that some people may find interesting in the next few days. I have definitely noticed some things, but I want to do more testing to get a good "sample" of the results. I also like to build up suspense.

[This message has been edited by Glenn91L98GTA (edited July 06, 2001).]