i have not tuned since November but i have been meaning to ask this question. since my tuning efforts began three years ago i have experienced an inability to get a clean response in neutral(manual) with a throttle blip. that means SOP the engine and resulting WB log shows the lean spike from the throttle blades opening(2.00 TB) with the following enrichment occurring too late. the blip is a flat result for lack of a better word. i started with a stock GM TPSMAP AE table and enrichened proportionally to get the AE in line. that did not effect the blip of throttle however. i then experimented with fattening up the lower TPS% and well as lowerMAP so as to get the enrichment in faster. that did not provide a positive result. my buddies 350 carbed engine has a crisp response in neutral. is this a characteristic of speed density engines? if not what else can i do to improve? this is mostly pre EBL(08/2006) but i dont believe EBL has improved in this area. actually there is no need to be concerned with this as it is not a drivability issue. BUT it may help my AE routines if i can get more gas in engine faster.

 

Given a big enough throttle body, any car would have an off idle *sag*.

Opening the throttle ~30%, gives you 60% of the cross sectional area of the TB. So air flow changes dramatically with a bigger Throttle Body, at the low throttle openings.

That being said, sometimes you have to fudge the VE table to get a good off idle/ low throttle response.

It wouldn't be surprising to see some timing adjustments in that area also....

When dinking with the tune for things like that, if changing the VE doesn't help, then try timing.

On one engine combo I had, going from a 62mm monoblade to a 70 meant the difference of not being able to get rid of an of idle sag. Since it was a street car, I went back to the 62, and then built a car to use the other TB... <G>

 

Thanks Grump. it appears the VE can be used to "crutch" AE once again.

will the fact i am idling OL @ 14.00/1 @ 35-40 MAP 850 rpms require that i fatten up the area 900-1000 rpms at 45-65 MAP? like up the VE table on MAP?

i am currently idling at 21 deg. i tried 16 and 26, and 21 seems best quality.
would one add in a couple degrees in same area as above?

 

Ron,

Have you played with the Throttle Follower? What are the IAC counts at idle?
I have restricted TF to about 50 steps so that I drive as much of the air through the venturi and not being bypassed through the IAC opening. I don't have any bog but there is almost always some kind of AFR sag. Its a question of how long it lasts. Looking at me EBL logs, mine has a duration of .1sec or about 2-3 datapoints in a log. I have also concentrated on the TPS AE and de-emphasized the MAP AE.

 

Guys I have the same lack of quick response time on throttle blips for downshifting. Pre EBL they were very quick and crisp. Many riders noting the speed of which I could go down a couple of gears slowing down and entering corners. [I like road racing by the way ] I have only spent a small amount of time on this matter a while back since other things have taken priority. With the new EBL tune it has plenty of fuel. Larger injectors and higher fuel pressure after adding a Walbro fuel pump. The only work I've had time to do lately is follow the Prop Gain posts and work on an idle surge. WOT and hvy throttle are the best ever so I would be interested to hear other comments on this issue also.

DM

 

The issue I have "struggled" with using EBL is DFCO. Prior to EBL, DFCO was very clean. I could downshift rapidly through the gears and the car would slow down with no drama. Today, it just seems that I can't get fuel cutoff soon enough. There always some fuel left when I go into decel in order to cause a popping from inside the exhaust in what feels like either in or after the cat. However the complaint Ron and DM have regarding throttle blip is no issue for me. I think RBob can attest to the throttle response.

 

Dom...........I have DFCO disabled and have the lower ve tables at zero IIRC. I too have some exh. popping after dropping to zero throttle with the car in gear. In fact I believe that the fuel being pulled out of the system on decel and then clutch in and doing a throttle blip is why it's not crisp. It has no fuel to start with. I remember doing some work when first getting the ebl and Bob stating that several users complained of stalling with manual trans after doing decel with DFCO and pressing the clutch in.

 

Not sure on the code you guys run but is there a "differential TPS" multiplier?
If so the reaction of the calculations would increase with smaller TPS movement by increasing the value. In $8D it appears to be set quite low (0.125) so there is room to make the calcs grow.
I'm sure its not a cure all but may help with some issues. Obviously will cause other tuning areas to be tweaked back a bit to reduce the reactions that you don't want increased.
Haven't done any direct testing to confirm/deny reactions but thought I'd toss it out there.

 

Many years ago when I first TBI'd the 327, I used the stock 350 1-11/16" bore unit. With this the throttle off idle was sharp as a razor. So much so that at the last state inspection the guy lit off the tires and almost drove it into the side of the building. Shook him up where they pushed the car into the bay. . .

Only down side was that by 4,000 RPM the engine was done. Flat as a pancake, no mo go.

After changing to the larger 2" bore TBI unit this sharpness was blunted. On the up side the engine now pulled strong to 6,000 RPM. My thought is that the manifold pressure increases so rapidly that the air becomes stagnant. Adding throw to the throttle setup helps, as it slows the opening of the blades. As it is now once over 1800 RPM the pedal can be slammed to the floor with no hesitation.

will the fact i am idling OL @ 14.00/1 @ 35-40 MAP 850 rpms require that i fatten up the area 900-1000 rpms at 45-65 MAP? like up the VE table on MAP?

You want to increase the VE at higher MAP values. From say 800 through 1200/1400 RPM. Then 80 through 100 KPa.

This technique is common to crutch or help on AE.

Today, it just seems that I can't get fuel cutoff soon enough.

To have no delay prior to DFCO set these values to 0:

DFCO - Enable delay
DFCO - MAP enable delay (the doc has this as TPS enable delay)

Then to have the fuel taper off as quickly as possible, set this to 100%:

DFCO - Decay Multiplier

That will provide an instant fuel cut. With larger injectors there will be more fuel during the tapering off period. At a minimum the Decay Multiplier should be increased.

May want to double check the DFCO - Lower/Upper MAP Thres(hyst) threholds. The MAP needs to go lower then the lower thres before entering DFCO. And will exit DFCO once above the upper threshold.

when first getting the ebl and Bob stating that several users complained of stalling with manual trans after doing decel with DFCO and pressing the clutch in.

Yes, this was an issue. The default DFCO values were for an automatic equip'd vehicle. When used with a stick the engine could easily stall when de-clutching while slowing for a stop. I've since changed the values to alleviate this. All I did was to check a TBI stick shift BIN. It was quite different then an auto BIN.

RBob.

 

I know the feeling as my WOT map values are around 90 now but it still pulls to above 5k. I still have the smaller TB unit on mine so it is not the reason for the lack of throttle response on clutch in after being in DFCO with zero fuel. In gear there is no problem when going full throttle. I do know that now without the fuel in the exhaust [when off the throttle in gear as after a down shift to slow] there is no popping as there was with the stock computor. So...I'm guessing that when there is no fuel being there at all that it is going to hesitate when blipped. It looses prime so to speak and cannot have a quick response.

DM

 

If you are talking about off the gas then back on and it hesitates. Look at the DFCO exit pulse.

 

Thanks I will.

 

I dont know if this has been mentioned yet, but it seems as though theres some time lag in the response of the MAP sensor as well as manifold filling when the throttle is first opened. I remember that without any momentary TPS AE, the engine would just sit there for a second and do nothing when I hit the gas. When I converted over to MAF it was really bad as not only was there an apparent transient response in the MAP, but also a transient response with the MAF due to how Im reading it in. With the SD, it would just hesitate. With the MAF, it would let off a huge bang out the intake, and then take off normally as though nothing happened. The easy solution to the short lean spike when tipping in was to add momentary AE based on the TPS. Just enough to cover for the transient response and the sudden inrush of air as the throttle opens. This same stratagy was used in the early f-body TBI PCMs ($4D, $61). There was a short spike of AE as the throttle opened that helped with throttle response. Without it, there would be momentary hesitation on tip-in.

 

Dom: Have I played with the throttle follower? Yes sort of. This weekend before reading this post. I opened up the latest EBL bin i am running and attempted to reduce the IAC counts that occur in TF routine. i pulled out 20%. As far as adding fuel to TF I could not identify the table to do so? What specifically is it called. I dont hacve access to TP righ now but i did see one i think was called TF Gain and showed % ??? not sure why i would want to add or remove fuel. by reducing the IAC counts during TF and not touching the TF fuel i believe i may have fattened up the routine.

IAC counts at idle are O. open loop idle.

DFCO is disabled as of yesterday as was Hyway mode. it showed up in WU logs last fall. no backfire-popping into exhaust ever prior with DFCO or otherwise referred to as DE. I believe the DFCO was adjusted for my manual post EBL install as it also stalled. no stall since. NO CAT. No air pump. having some fuel in intake tract after a decell cant be a bad thing? other than exhaust note. Hyway mode is different.

Differential TPS multiplier? I forgot it existed. I played with it in Tunercat. So JP88Ss states that a larger # will benefit. I assume that affects the duration of TPSAE but will not bring on even sooner? how could it? so a larger # will put the same quantity into maniford over less time?

RBob states adding throw to setup would help? how can one do that mechanically? I see holley TBI(4 barrell) is progressive with first 50% of pedal movement moves only first set of blades, then the second set open. maybe possible to add creative linkage to allow 50% pedal movement allowing 25% blade movement in a 2 barell TBI? more than i can engineer.

Fast comments... my issue was always from dead stop with clutch engagement. or blip during stop. once rolling i never had issues on-off gas.

Dimented comments... i experimented last fall with TPS vs MAP AE. i skewed the tables from mostly AETPS to MAP. basically revered the fueling using same quantities as a constant. results were dismal. seems TPSAE is much quicker reacting. i wonder if TPSMAP makes any contribution at all? one would think that the TPS movement would provide instant AE to balance out the onrush of air ???? as the TPS signal and injector on time would coincide exactly with the incoming volume of air? unless it(fuel) is hung up on TBI and plenum walls awaiting shearing?

 

I don't exactly know how the fueling is on the EBL for TPS AE or even MAP AE, but with the stock ECMs you have the % Change calculated every 12.5 milliseconds. That means that you have to see 50% TPS change in 12.5 milliseconds to hit that particular AE situation. What that means is that in a scenario such as easing onto the throttle and engaging the clutch, you need to change the lower end of the AE tables.

I have Dimented's MAF TBI setup up and running as well. I had the same BANGING back into the intake setup with rapid throttle opening. The engine was fine as the transmission upshifted, downshifted, etc. But it would not take heavy throttle opening smoothly at low engine speeds. It was particularly worse at light throttle cruise in say OD at lower RPMs. It would bog terribly, downshift, then get up and go like someone had just kicked it. TPS AE easily reversed this situation.

 

RBob,

"Today, it just seems that I can't get fuel cutoff soon enough.

To have no delay prior to DFCO set these values to 0:

DFCO - Enable delay
DFCO - MAP enable delay (the doc has this as TPS enable delay)

Then to have the fuel taper off as quickly as possible, set this to 100%:

DFCO - Decay Multiplier

That will provide an instant fuel cut. With larger injectors there will be more fuel during the tapering off period. At a minimum the Decay Multiplier should be increased.

May want to double check the DFCO - Lower/Upper MAP Thres(hyst) threholds. The MAP needs to go lower then the lower thres before entering DFCO. And will exit DFCO once above the upper threshold."

I thought the settings I had were pretty restrictive but you are right since I am running 80# injectors at 20# FP. The popping is worse when I do a quick stab of the throttle at load. I can do it in idle with no popping. I also have the DFCO settings so that there is very little room where I would not be in DFCO. I'll give it a shot once the ice disappears from the latest storm here.

 

before EBL i experimented and put more AETPS in the low %. ie instead of 122-168-183-244-305-361 i tried 183-183-183-244-305-361. or some multiple there of. made no diffenence. but my underlying VE-timing--ETC may have been a contributor as well.

 

TPS AE engages as soon as the throttle opens, so its instantanious. The MAP AE (or something similar based on TPS) is needed for longer durations of enrichment.

 

If it really is just a momentary lean spike lasting for less then a second or two, then the solution is additional momentary enrichment based on on TPS. This will cover for the large slug of air that you get when the manifold fills and also cover for any potential time response in the system. This will also avoid the need to use the VE to cover for the AE.

 

NVM,
"DFCO Decay " at 100%
Edit: I guess this is a "fuel decay" now that I've read that a few times.
Need to read up on that, not allot of discussions on DFCO that I find.

 

i think i read that Grumpy once said MAP-AE is involked when there is a change in MAP with or without change in TPS. like when you lock TPS movement and climb up a hill. zeroing out TPS-AE may be a good way to tune MAPAE. just find a nice hill to work on.

ps. my data logs of WB sometimes shows both events and PE as well (if PE is set to a higher % TPS). a double spike for AE(seems the TPS is always stronger as is set accordingly) with the PE coming in later. If i set the PE to a lower % i see the PE come in immediately after the AE is exhausted. sometimes the PE blends in perfectly.