from day one i had a bad stumble/cough on hard acceleration. i believe i was using a "stock" vette bin for AE/MAP/TPS. i was of opinion the cough was inadequate AE values. a rapid increase in air flow and lack of immediate PS. so i increase at 5% accross the board in AE with little improvement after several attempts/burns. Then i went 10% more on top of what i had and started to see less cough/stumbled on hard accelleration. air temps last fall were dropping so maybe i was fighting cold air as well. not sure. result was 250% inc at all values. yup that was a lot. currently at medium rpms 2500-3000 if i put pedal to floor quick i get a gurgle but goes. not crisp. this is 4th gear of 5 manual trans x way speeds. if in a lower gear seems to rev nice and less issue. never a cough. i thought i may have gone overboard in AE fueling so yesterday i backed off AE amp in lower areas.
old AE/TPS 0% 305 AE/MAP 0 732
3 671 20 1343
9 1282 40 1831
12 1465

new 0 244 0 0
3 610 20 1099
9 1160 40 1831


the map was moved to tps and i thought that was suggested somewhere as a good thing. i think it was said to make the 0 map at 0. should the 20 map be zeroed and moved to tps?. on a hard accell at 20 mph in 2nd gear it still coughs badly and stumbles. moderate hard accel it goes. seems like wont tolerate a hard full pedal to floor. is is possible i need to increase the TPS even more in higher % areas? same with map? but map slow to respond vs tps? blms optimized as is PE. spark tabled moderate not aggressive from what i compared. thanks for the help

 

If it's getting better continue to add.
The bugger with TBI is that as you nail the throttle the intake velocity drops to nothing.

If your using a big open element air cleaner that can aggravate things. In lots of testing with my 355, TBI'd car, it ran best with a 2.25x14, and slowed down with a 3, and 4" tall filter.

 

Your switching to the 747 soon?

Anyway, I've had a stumble under accel at below 3000rpm for the last year. The only thing that fixed it was stretching out the AE, using the AE tps and map filters (747 ecm). I run about 300% the table values for AE. Then the filters stretch out the AE, I used about 60 - 70% of the stock filter value (lower value means more stretching). Also I'm running about 2X the injector flow rate. And its been pointed out that chaning your bpw (again 747') doesn't affect AE calculations.

So I'm running tons of AE compared to stock. The main reason I think my engine needs this is cause of large intake plenum volume. I've got a ported intake with spacer. So with out knowing the exact cc values, I would guess that my plenum volume is about 3x the stock manifold's.


So play with filters, they helped me the most by far. I can now nail it from idle with no bog at all....nice!

 

Grump. thanks. that was my opinion. the xram has a single plane. that plus the 2.00 TB's drops intake velocity and injectors cant keep up or are delayed in effect. Q i think i understand the AE MAP as self explanatory. the AE TPS of lower values such as 0-3--9-12? are those a percentage of travel of tps sensor? 3= 3% of possible travell? that does not make sense. how could i ever open tps 3%. i need an explanation on that. i reduced only those area thionking my increase at 250% was not needed and left the higher values of tps/map at 250%. i may add more still in higher areas only.
low1500. i have 7747 and tunercat. TC i dont believe allows me to edit what you call "filters". what is a filter? filers stretch out the AE? does that mean a time consideration? if i understand this correctly the injectors fire more often over a period of time so the effect is longer in duration/time span? this may be another area TC doe not support? i have not the knowledge to edit what i think you call hex. just learning! 2X the injector flow rate? doe you mean the BPW is modified to make ecu think it is smaller, if that makes sense, so it stays on longer? or is the FP upped to provide more spray(duty cycle). my manifold is a weiand low riser vs prior crossfire. i believe it to be healthy as rated to 6500 pms

 

I use winbin (7747mine.ecu) to edit the filters. GO to diy-efi.org and read the fueling paper on the 747, should clear things up.

 

It's delta TPS. or in the case of 3, if the TPS changes 3%. So changing from 12% to 16% would be in excess of 3% so on that bias there would be some TPS AE available.

 

thanks again. i looked up diy.efi.org and subscribed. it seems no search function to locate that thread/paper(filter/TPS/7747). any tip on how to find it? i have not browsed that site as of yet.

 

http://www.diy-efi.org/gmecm/ecm_info/1227747/


Lots of very good info there.

Again I had the worst bog before, I just went for a spin, and I can't make the thing miss at all, warm or cold engine temp. AE filters were my problem, and I'm sure there yours.

 

It looks like the 747 lag filter paper isn' t there anymore, but all you need to know is that a smaller AE filter (ie: 0.09) will add the AE slower and over more time, than a filter of of say 0.43


So try and find the 7747mine.ecu file, it was done by V8astro captian (he doesn't post here anymore). I can email you it if you can't find it in the ftp.

 

thanks so much. that is a great site. i just enrolled. lots of tuning info. i will look for that. dont i need to know how to hex edit to change it? maybe TC will add this in for me. They did b4 on deaccel enleanment. if my filter setting is say .50 would not i gradually change it and test the result. say from .50 to .40 and check it out?

 

Steve has rearranged the site a bit, the papers ('7747 & '8746) can be found here:

http://www.diy-efi.org/gmecm/papers/

The 7747mine.ecu ECU is the Spk747_3.ecu file with some additions. The Spk747_3.ecu may be found here:

http://www.diy-efi.org/gmecm/ecm_inf...7/Spk747_3.ecu

Even though it is labeled 'Spk', it has a lot more then just SA in it.

I think that the 7747mine.ecu ECU is on the diy-efi ftp site.

RBob.

 

thanks again. can someone explain how increasing the duration of PS will help a stumble? it appears this is the plan. i also will add more at higher TPS% only and leave the MAP as is. does this seem like a good approach?

 

Since your intake air velocity is probably slower than stock when you crack open the throttle, you don't the quick burst of gas. But since your plenum volume is larger than stock , your map sensor will be a little slower to pick up the increase in load, so to keep the air fuel ratio good , until the VE table values take over , the the longer AE going in helps.