How does the Accelleration Enrichment Multiplier vs. TPS Differential table work?
The table is 2D going from a TPS value of 0 - 50 and the Multiplier goes from 1 @ a TPS of 0 down to 0.25 @ a TPS of 50??
*
This seems backwards, seems like the bigger multiplier of 1 would be at 50, not 0.25, which would seem to cut fuel at higher TPS?
And how is the Differential TPS measured since it only goes to 50??
This is in the 90-92 TPI ECM.

 

which tunning software are you using.??

 

I'm using Tunercat, but this table is also know as the "Pump Shot" table in other sw, in fact in the hac code its called Pump shot Vs TPS Differential.

 

well i wanted to make sure we were on the same page thanx. ok the multiplier would taper off. ever changed and accelerator pump cam on a holley ?? same sort of deal. the first pulse needs to be the biggest while slowly tapering off extra fuel. although the conversion sounds sort of fishy. got a nasty bog ?

 

Depressing the accellerator at cruise speeds seems to be a little lazy, not a real bad bog, but there is a definite flat spot that I can't seem to program out.
I understand now what your saying by tappering off the fuel after reaching 50% throttle.
I see in the hac code that the value in the table is multiplied by 128, but not sure how the resultant is used in combination with the VE table value.
Time for a little experimenting....

 

yeah if theres a flat spot in cruising throttle i would try bumping the AE timing by maybe a dergree or so. also try changing the multiplier to say maybe 1.02 or slightly more. anyways yeah work with the accelerator pump cam in mind. i had a bit of trouble with the concept at first till i realized it behaved the smae way. could also be to much fuel. hard to say. got any vacum leaks.?? this will cuase flat spots as well.

 

I asked that question back in 1999...

https://www.thirdgen.org/techbb2/sho...threadid=37059

It still doesn't make any sense to me. The greater the differential TPS the more pump shot the car needs. For example - if I crack the throttle open from 0 to 10% then the %TPS would be 10. If I crack the throttle from 0 to 50% then the %TPS would be 50. In my world - the 0 to 50% throttle opening needs more of a pump shot than the 0 to 10%. The numbers ... even after 3 years ... still seem reversed to me (as originally indicated in the HAC).

Tim

 

Unless in the code it take the result of 128*(value) and subtracts it from 128, where 128 would be the max pump shot....
And it assumes there can't be more than a 50% change in TPS in a single data loop in the computer. Going from 0 to 50% in less than a few milliseconds would be impossible.
*
Given this, making the value in the table closer to 0 would make the pump shot greater......
Just a guess, I have not seen any of the code to confirm this.

 

ill ask email tunercat and se what they have to say ont eh subject.

 

Let us know what they tell ya funstick.
I increased all of the original values by .150 and could not tell much difference, so then I decreased them to these values (starting from 0%):
1.000
0.898
0.750
0.508
0.328
0.289
0.289
0.289
0.148
0.148
0.148
0.148
0.148
0.148
0.148
0.148
0.148
And it seems to be a bit more responsive, so maybe decreasing the values does add more fuel.
As reference, the original values were:
1.000
1.000
1.000
0.625
0.375
0.375
0.375
0.375
0.250
0.250
0.250
0.250
0.250
0.250
0.250
0.250
0.250
My mods include TPI with ZZ4 short block w/ZZ4 cam, fully polished Sportsman200 heads, headers, light porting on stock intake, runners, and plenum, 24# inj, 1.5 Roller rockers so it should be able to handle a little more juice on the pump shot than the original settings, so I'm inferring that it increaces by decreasing the table values.
See what Tunercat says, thanks

 

this is from the horses mouth cut and paste.

Hi Sean,

No this is actually not an inverse table. The TPS Accel Enrich pulse width is directly proportional to the differential TPS. This table is used to reduce the effect of the differential TPS on the calculation as the differential TPS gets larger so a larger value from this table does increase the Accel Enrich pulse width.

 

Thanks for that info, I guess mine actually likes less fuel then on accell as it sure does acell crisper now. Probably because my VE table gets pretty aggressive already at more than 80 to 85 KPa intake pressure, and the PE values have been increased as well.
Thanks

 

glad to help.

 

I'm still not buying it! I reduced my pumpshot values and got better tip in response as well, and I'm pretty darned sure I had a lean tip in problem. The table seems backwards from conventional thinking. I glad I'm not the only one who is confused by this.

Steve

 

Always comes back to what the engien wants - not what you want or expext to see.
Always best to try a little both ways and log the engines response , then decide what the engine responds to. One of the reasons I bought this on the fly tuning setup for the 165/808 you can quickly make a change and then analyze how it feels.Although it is just as easy to program 4 bins onto a chip with slighly different changes and analyse that by swapping while driving betwen them.

 

I started looking at the hac hoping to add some insight to this thread. I'll say, there is a lot more to the $8D AE then I expected. The table discussed above (Acceleration Enrichment Multiplier vs. TPS Differential) does reduce the AE as the values get smaller.

What is not shown is that the actual differential TPS is also added into the AE BPW. This value is factored by the term at $8534. So there is a decent amount of AE increase due to an increase in differential TPS.

There is a differential MAP table that increases the AE BPW as the delta MAP increases. The total amount of AE also depends upon the current (regular) BPW along with how long the AE has been active.

There are two reasons that a port injected engine requires AE. The first is for tip-in response. It is to provide a momentary decrease in AFR for better feel.

The second is to make up for the wall wetting of the runner. A port injected engine has some wetting but nothing like a carb or TBI injected engine. Wall wetting is where fuel clings to the surfaces of the interior of the manifold and head runners.

For the most part wall wetting is covered by the differential MAP AE while tip-in is covered by the differential TPS AE. One thing to remember about wall wetting is the effect of air velocity in the runner. At higher throttle openings with greater air velocity the fuel will be stripped from the runner walls. This reduces the amount of AE fuel required.

AE is the most difficult part of tuning an engine. A lot of it is done by feel. How well is the engine responding to pedal changes. . .

RBob.

 

does anyone have a WBO2 on thiers? it ought to be fast enough to be able to see the difference in adding or subtracting from that table to see which way it goes. I would like to see for sure which way it is. I am playing with it now, but have not had a chance to figure it out & dont have a WBO2 running.

BW

 

Answers:

Yes.
Yes.
Lowering the pump-shot number reduces fuel in $8D.
It takes a lot of trial & testing to get pump shot right.

Here is an old example of AFR vs. rpm - from last winter, prior to final tuning for that combination. You can see the pump shot on the left hand side of the blue curve, as rpms spool up.

http://temp.corvetteforum.net/c4/doc..._a_10feb_s.jpg

DrJ

ps - when you gonna finish your WB? I ordered some crank trigger parts last week.

 

Not sure what I am looking @ there. the brown line jumps up but that is B4 the blue line even starts to move (2 divisions). if I look 10 devisions in I see what I could say would be an increase in the brown line with a coresponding increase in the blue line, but then it drops back down (decay on the pump shot?) to some AFR. then @ some high RPM, it looks like the AFR gets a hicup.

What kind of scope are you using there or are you using a DATAQ or similar to record that data?

To be frank with you I have not even started yet. I have been swamped with other projects. now that it is getting close to "winter", it is time to break out the in door projects. that & Christmas is here & I dont have any Doh-hoe. I am selling the Camaro, so I redid the seats & am going to get it painted. I hope to have both of the WBO2's done in a couple of months, but.......

I have found a lockout for my distibutor, so I think that for now I am going to go with that. If it is a PITB, I am going to head down to Cheby & find the parts I need for the crank trigger. I am interested in hearing how yours turns out. you are using it with your 7730 right?

BW

 

BW-

That chart is an old in-car Dataq record of a second-gear pull made from a rolling start, AFR & RPM vs. time.

(It was from a SuperRam on a 350 with a modest cam & the Corvette shorty headers - running up my 'secret dyno-hill'.)

Gray line is rpm - it starts around idle, then the converter flashes to ~ 2400 when I roll the throttle 100% open. It just lays like a lump for a while until it comes up on the cam ~ 2800. From that point it goes fairly straight up to ~ 5500, where I shifted.

Blue line is WB volts - it starts at stoich (center horizontal line of chart is 2.5 v) then drops as the butterfly goes WO. The first ripples are pump-shot + PE, the rest is PE only. The Dataq Cursor (center vertical line) is sitting at 2.12 v & 3610 rpm.

The whole chart is ~ 4 sec wide. With the Dataq you can make those all day long - when I'm working on it I usually make 3 pulls, insert a different chip, make 3 more pulls, etc. As soon as a run is over you can see how PROM changes affect the curves.

There's no special sigificance to that chart - it's just an example I had sitting in the computer. I think that one was a baseline I made before I did any fuel tuning. I have a hundred more just like it in my notes that show various spark and fuel changes - and I'm still not done (sigh).

It's an example of what you can do with the Dataq & the WB. Here is another one I saved - It shows what a misfire looks like (burned through a plug wire on a new set of headers): http://temp.corvetteforum.net/c4/doc.../misfire_s.jpg

They are just examples of what you can do with instrumentation & a laptop.... (By the way, THANK YOU to the developers of the DIY WB - it works great!)


I know what you mean about Christma$$$..

I ordered the L-31 crank wheel & sensor, and I'll try to fit those in Dec/Jan on the 727 ECM. Need to see if that works before I invest in the LS1 coils...

D

 

I fought this and fought this also with my Miniram intake. I never did get it right. I swapped on a Super ram and now the stock AE tables worked good until it got cold outside. Now I have a very , very tiny tip in hesitation. I have a relocated MAT sensor that I plan on putting back to the stock location before I start playing with AE fuel again.

 

Sounds like its time for a little tweaking on the "Inverse MAT Term Lookup Delta Multiplier vs. Airflow" table to adjust fueling based on MAT so you don't have to change programs everytime the temp changes, at least if its a large enough change to effect BLMs.

 

Nahhh. Just easier to put the temp sensor back where it belongs!

 

CL, I see it now. I will check out the other one when I get to work in the AM.

BW

 

Is the TPS calculation based on one scan through the ladder of the program or is time based? Sorta the same thing I guess.

BTW, What is the scan rate of a 730? I like trivia.

Steve

 

WOW, Boy does that WBO2 move fast. you can see exactly where it flakes out & where it cleans up etc. how are you loogging the RPM in? did you make some kind of an adapter, or are you overlaying scanned data in on top of your data logged data?

BW

 

Bob-

http://temp.corvetteforum.net/c4/doc...ach_box07s.jpg

The tach sender is made from the LM2917 chip. RPM & WB volt data go directly to the Dataq board, & I use those charts to tune WOT fuel and spark. (No sense making PROM changes unless you have a way to measure the result.) For part-throttle work I use Diacom & Datamaster.

There is a write up of the tach sender (and a shift-light) I built somewhere in the middle of this thread - along with some possible OBD2 sw solutions:
http://forums.corvetteforum.com/zero...postid=3960101

If you have any Qs on the tach let me know.

(On another topic, I put a summary of my HEI coil investigation here, if you should ever need any of the info: http://forums.corvetteforum.com/zerothread?id=419893 )

Dave

 

Shoot Dave, you are ALL over this. what have you not done to that thing yet? LOL

did you just copy the suggested print off of the National site or did you make any modifcations to it? I am thinking that maybe I ought to buy a larger WBO2 box & stick it all in the same box. my only concern is that the freq from the ignition is going to mess with the WBO2.

BW

 

BW-

Um, the 2917 needs a zero-crossing signal on the input for it to work. I used the 'points-type' example circuit from the National Spec Sheet & tied into the switching terminal of the HEI module for a feed signal. I did a quick test on the bench & the tach output (scaled to 1 v = 1000 rpm) was +/- 1% or so from 600 - 6000 rpm... which ain't bad for a $3 chip on a $2 board. Oh, yeah, I also used shielded mic wire (cheapo RadioShack type) to bring the coil signal to my tach box... Thought that would keep stray RFI out of the neighborhood.

Depending on what you use for a trigger, the input of the 2917 may need some protection from v spikes & RFI (if you tie it directly to the coil). I imagine you could also run this board off the tach input to your dash cluster, or make a separate input line and use something like the GM tach filter dwg shown here: http://temp.corvetteforum.net/c4/doc...chfilter_s.jpg

I don't see any reason you couldn't put the WB in the same box (if RShack has a box big enough) - just do the RFI filtering outside the box if it's needed...

If you decide to build it send me an e-mail off line & we'll figure something out.

Dave

 

COOL.

BW