edit: This is on a 383 TPI 730 SD car with vortec heads and a 217/221 cam around .500 lift

Having some difficulty working something out.

From a standing stop the wideband will go from 14.7 to 11.8 and then settle in the lowwwwww 12.0 range.

This is accompanied with some slight knock, couple degrees tha tapers off quickly.

If I am rolling at say 30+mph and do a heavy stomp the wideband will register 14-15afr and knock will be present then decline to high 11 low 12 afr at the same time. Will spike to 8-9 degree than taper off.

I ahve been treouble searching several issues and eliminated sources of vibration and a clunking driveshaft loop. So at this point I am positive it is related to the tune and it is not a false issue from mech/elec/outside sounds.

Also pulled a large amount of timing out from cruise to WOT and results were identical.

The AE on this thing is giving me fits. I can leave a lite fine. I can accelerate light to medium fine. Will see AFR dip to 12ish then rise back to 14.7 as it tapers out. Just the heavy medium to WOT I cannot get quite right. Damned lean spike is kicking my butt.

How much AE added to the TPS table is enough?

Or would my issue possibly involve some of the MAP AE since it is while rolling is it the larger issue?

Could my car just want more AE even thou it "feels good"? Is it showing tme that hru my little lean spike after AE cuts out on lite throttle transitions? (will hit 14.8-15 then settle back to 14.5-14.7)

Possible I may have to play with the pulsewidth scale factors?

Or am I looking at something the wrong way?(always possible with my warped mind)

Again, the rolling hard accells seem to make the issue very noticeable?

Its really my only complaint on the car, and its really frying my last nerve lol

Thanks for the insite as always

Jeremy

 

30 MPH in what gear with a heavy stomp?.

Not always is going *rich* needed, in AE. You can add enough AE to where that's then the problem.

 

Any heavy accel to cause a downshift from 4-3 or 3 to 2.

Can also get it to workon a heavy third gear romp without downshifting.

Did notive something in your other post. You AE delat TPS starts smaller then goes longer and then settles back down.

I do have AE tables as being sloping curves in my head and how I "attempt" to work them.

I understand the smaller AE amount at intial TB openings. It does go rich for a plit second then the lean hit occiurs and knock starts.

Maybe try and play with the delta TPS and try working towards a more bellshaped curve. Seems like it might be worth a shot.

Hard part is I dont have alot of $$$ for gas lol. So I work on it and it sits for a week etc.

later
Jeremy

 

grrrrrrrrrrrrrrrrrrr

frustratin pile of stuff I cant say :-)

Did some light playing around t-nite.

Abandoned issues due to several issues I noticed much improved from not running the car on the Romulator.

Dipping rpm at idle and the wideband reading rouglhy 14.6-14.7 vs 14.3-14,5 everything else the same.

Have to find a good way to shield it.

Thinking going back the the AE yet again(using chips) should hopefuly net me some more consitent results.

Jeremy

 

Well, maybe your phasing of things is just off. If you want to set the TPS PE enable high for MPG, then you will have to fight a too lean moment. You might try upping the BKR amount or lower the MPH threshold (you'll have to look at exactly how the 8D handles the above).

Doesn't that just make sense, once you think about it?. Since it's delta TPS, at small deltas, you should need hardly any, and then progressively more, up until it's easy to get into PE.

Don't forget too retarded of timing with too much fuel can put you into detonation.

 

Whoa! What's that, Grumpy? Never heard that one before (or I'm having another Senior Moment and forgot that I had....

I've dropped my timing so much trying to drop the knock counts that I may well have set myself up for this condition. Could you please elaborate just a bit more on this topic? Please?

 

PE enable is all TPS % based.

Currently it is more setup like the 3.8 Turbo code than the TPI style :-) There are set pretty low.

Motor has torque, I dont need throttle opening to make it move around normal driving ranges, so in turn I dont hit PE unless I get on it. So when I am "on it" its in PE mode. I usually have throttle openings of like 10-15% when accelerating around town and even highway cruise with TPS set at .55 @idle I am only at .88 on the highway at 70 :-)

I'm still fighting that transition stage with the AE vs Knock vs PE engagemant.

And yes I am revising my views on what "I think" and AE table looks like and trying to force myself to think like air/fuel and what the "car wants". I am pretty sure I think my car has an AE issue and I am sure it needs more(from wideband readings) . Trying to ascertain the exact why and where my car wants it at.

Hopefully weather here stays ok so I can play and update it some more later t-nite.

thanks guys
Jeremy

 

If adding isn't helping, try removing. It might look like a lean spike on the wideband but when the engine isn't happy you might as well try the opposite and see if it helps. Have you removed some timing in the high load low RPM areas? Even if there isn't any knock counts it doesn't mean you aren't getting pre-ignition that's causing your issues from transient. When you snap open the throttle pretty fast the ecm moves rapid like over to those low RPM high load areas... area's of the tables that would almost never be reached unless in the conditions you've described.

vernw, run rich and retarded and things like the exhaust valve get super hot. If the spark plug is near the exhaust port and you've got a warm/hot plug for all weather conditions then you could get detonation. I'm not sure how else it cascades into detonation other than I've done it . I thought I was running too much timing so one day I took out 10 degrees from the main table and took her out for a spin. The thing had no power and I could smell my headers cooking. Then whenever I leaned into the throttle, forget it, it slowed down and make some aweful noises. With an unpatched bin (code 43 still enabled) it would through the code and I'd be putting along the side of the road with even less timing! Moral of the story, don't run too rich and too retarded. Why do you think all those vette owners keep getting into accidents

 

yepper..........
I'm not sure I can fully answer this in just a paragraph or two, but here goes..

The spark cascades an event already in progress.
Detonation is an abnormal combustion event. *something* has gone wrong in the cascading part of the equation, and two flames fronts start, with the spark event, and collide with each other.

Now, if the cascading is allowed to progress too long (retarded timing), then the cascading is further along, and the spark, just puts the reaction into a catastrophic event, because the whole chamber is just waiting to explode.

Now, if you add an excess of fuel to the situation, then that increases the compression ratio, ever so slightly, remember we're in an event that is already cascading, and ANYTHING that pushes the event along faster then what is *normal* can sent the process into detonation.

If the cascading is hastened along (excess fuel), or allowed to pregess long enough (retarded timing), you can skip the detonation part all together, and be in preignition, and have serious issues, in the long term. Remember we're just talking about a tip-in discussion here. Once you drive the temps up in the chambers, from just about anything, then you have to add fuel, and again, you're just getting further and further from what the engine really needs.

If you do a search under my name, you'll see where I posted some AE stuff where it shows 0 initial AE, and at the end of the tables, again 0.

It took an incredible number of hours to *stumble* into that. It was more like, I'd tried about every combination of timing, VE table changes, AE, and PE to figure out the code needed a *simple* tweak to allow shutting off the TPS AE to get the throttle response *perfect*. Once I got the bell shape of the TPS correct, the MAP AE was a snap.

BTW, this also in some ways may fly in the convention wisdom, about min lenght intake tracts always being the best answer. If you have to wash the cylinders with fuel, from AE, then I'd say the tract lenght is just *off*. One needs to remember, with a 3.0 first gear, and a .6 overdrive high gear, it's not like the engine doesn't experience a huge difference in load. But, that also gets us into differential fueling and timing based on gear, and VSS.

Again thou, your mileage may vary......

 

Yet more testing :-)

Finally got some positive results.

Only annoyance is the damned lean blip after an AE event still.

I managed to get enought to cover the area from AE to PE though :-) Took a lot more AE than I thought. Now I have to retest and back it down vs. knock counts.

Wierd part was the lean blip is still there under almost any circumstance other than enough gas pedal to hit PE. This is with even cutting the decay rate by 50% from stock.

Ah well, progress made ever so slightly :-) Its getting better, its getting better every day lol

HAve an issue on the left bank fo the engine anyhow now, wideband is osciallating while driving lol. Gave up working on stuff after that. Get it fixed and do it all over again

later
Jeremy

 

Is the lean spike coming in while the iac steps increase?
If yes, there might be enough air to need some AE that isn't triggering enough MAP AE. Some code has it where any time the IAC opens there is a pulse of extra fuel... but I've only found it in TBI code.

 

Light throttle movements generally yield large MAP movements. Are you focusing on dTPS AE? I'd take a look at the dMAP AE first, then go off into lalaland with spark and cascading events and rich mixtures raising the compression ratio (rather than say maybe increasing the burn rate??). I'm gonna catch some flak, ain't I. Jacket's on, but I'm unarmed, hehe.

 

What do you consider large MAP movements?
At idle my engine is 50kpa 0tps. In 1 second I go from 0 to 10%tps and the MAP goes to 70kpa. Not fast enough to trigger an Async AE pulse. At 67mph the engine is at 47kpa 16tps, 1 second I go from 16 to 27%tps and the MAP goes to 64kpa.
At very low RPM the MAP moves a lot with a little TPS but once the engine is motoring the car at a normal cruise the MAP really follows the TPS.
One good way of knowing if you need MAP AE with an auto is to look at the o2 and INT during an upshift. If you can't trigger a MAP AE with an upshift then look at the VE tables for fixing the lean spike.