Heres the "problem"...
If I get into boost at all under light throttle - my car freaks out and like bogs right down and i have to totally let off or almost go into WOT for it to straighten out. Now i was told it is due to the Jbody ECU's reading TP vs RPM... and that this can not be fixed, that its something boosted J's have to deal with and avoid. Due to Aplha N. And the bogging down is because it leans out way to much - i honestly forget what the AFR jumps to, due to not having driven my car for awhile and i haven't looked at my logs in since. (I dont have an afr gauge - i use HPT to read it and its hard to read the lappy while driving lol.) Should have it running again soon though (had to pull turbo to fix a few things)...
I also have it set so that at 20% throttle it goes into PE because i shouldn't be boosting it lower than 20% but the damn turbo spools so easy sometimes... And i mean like even if i hit 1pst, like if i just give it a lil more gas to speed up and it reads 1psi or more it freaks out... like boggs right down i guess is the only way to explain it.
I was just curious if theres anything you can do besides running in PE all the time, to avoid the lean out at low throttle.
My tuning still may need some adjustments but for the most part (if i remember correctly) im at 14.7 cruising and 11.7 WOT idle is around 14.7-15 and start up idle is still a lil rich but its around 11. Im still having some trouble getting it right -> where it hits 9psi and goes through the high rpm because almost in unison with my waste gate opening up it leans out to like 13.
I only have 1 post left so if i don't respond im still reading your responses! Any input is greatly appreciated guys!
Also another question regarding the 2200 motor - where is the crankcase breather/pcv valve. Im having blow by and i want to make sure its working. I need to relieve pressure in the crank case when i hit boost it makes some oil blow out of my dipstick
thanks
I'm sure you already know this/heard this, but I would recommend getting a wideband hooked up. In the meantime, if you can send me some of your logs, I can probably see enough from the narrowband (when in PE because it doesn't jump all over the place) to make a reasonable guess as to how rich or lean it is, but the first thing that came to my mind when you said it was bogging is it was going too rich possibly. The reason I thought that is probably because that's what mine does sometimes. I believe that comes from a few possible things. One thing is the PE enable, if it's set to low for lower rpms it'll dump a lot more fuel causing it to bog down. That would also explain the suddenness you describe in it bogging down. Another possibility is that some of the VE cells are off a little on the tuning. Use the 3-D view of the table to get a better idea of problem areas, any sudden change generally isn't a good thing. You will still look at the same issues if it's going lean, just with the opposite mindset.
As far as watching the logs while driving...just save it after you're done driving then go back and look. You can set "markers" to show areas in the log file you want to go back and look at by hitting the 'm' key. That comes in handy for marking problems after they occur so you can find them easier (such as you're bogging)
If you have any questions send me a pm or im.
i've mentioned this to jess but perhaps having others view it may provide some more input.
the jbody ecu is primarily an alpha-n setup for fueling. there's three primary VE maps (low rpm single fire, low rpm double fire, and high rpm.
the low rpm tables stop at 3800rpm and its from there the high rpm table takes over.
on top of this, fuel trims adjust AFR for stoich when not in PE. when PE is engaged, the fuel trims shut off, following the VE map exactly as it is. This is why tuning out low TPS inputs in low rpms helps fuel trim because it won't have to correct as much.
jess' car is turbo, which as all turbo cars do.. produces boost even under light throttle conditions.
our ecu (being that its alpha-n) primarily references 2 sensors for fueling.. TPS and RPM.
the problem with this is the ecu assumes that load conditions on the engine is always the same.. which it is not. A turbo can generate boost with little exhaust flow and when this happens the ecu cannot compensate.
a speed density ecu that uses a MAP sensor for load on the engine would be able to compensate without a problem. because as boot inceases, so does manifold pressure. When the ecu sees that data change, even tho RPM is low, it can still proportionately add fuel to meet programming criteria (either stoich, or your desired AFR under WOT).
alpha-n doesn't use the MAP sensor to effect boost, and thus as boost increases, it still sees RPM is low and TPS input is low, so it doesn't add anymore fuel. Fuel trims adjust for stoich, but with so much air being forced into the cylinder, the engine is almost certainly going to run lean.
fuel trims can only compensate so much before maxing out.
I can't really find another way to effect the fueling of the engine in other maps on the ecu through HPT. Perhaps someone else has more experience.
faking 2 bar maps also do nothing since again.. the map sensor has nothing to do with fueling. our ecu uses them for spark tables.
Btw PJ aww that sig is hott you know i <3 her in that shot 
Sexxxx
You basically reassured that I at least had a straight understanding in my head
I guess I just want to find a way around this (other than physically avoiding it myself). Which for the most part is possible, just kind of a pain.
Id also like to hear what Ryan has to add on the subject, im just waiting to actually go over and start on the car before I talk with him.
yea us jbody peeps got the shaft when it comes to ecu setups. (other than a few earlier year ecus for the 2.4)
its a shame HPT can't come up with a custom OS for us.
even n/a you hit a wall in terms of RPM limits.. for the lack of better terminology, our ecus suck.
why dont you use an FMU???
because thats the band aid approach, if ur in boost and the hose comes off the FMU, your in a world of @!#$ cuz the fuel pressure will drop and detonation will occur. (I was behind my buddy's when it happened)
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Jess, I'd love to sit down with your car and HPT and look through some tables. It's certainly possible that there's no way to improve fueling, but I've had to tune forced induction MAF equipped cars which consume more air than the MAF can measure, and when that happens you're left with TPS and RPM as your only variables.
I consider FMU by itself to be a band-aid because you're not addressing timing changes. But in a case like this, if there's really no other way to effect fuel delivery when boost comes up, the FMU will end up being the best approach. Sure, you could lose fuel if the pressure sense hose falls off, but you can also lose fuel if the fuel pump gets weak, or if the filter gets plugged, or if a wire gets corroded near the tank. Do a good job installing the FMU and connect the hoses using clamps and you'll reduce the chances of anything falling off.
-->Slow
At least for now id like to get an AFPR to keep an eye on the fuel pressure for one. And see if theres any way to at least adjust it a little with HPT. I have my tune on my usb drive now so im planning on giving ImPhat a call probably tomorrow or later today and see if he can give me any input . And Shannon id also like to see your input as well. I should have the cavalier put back together within the next week or two (im fixing the charge pipe issue i was having as well as a lil turbo re-build - oil seals went out.. so i should be done everything but the turbo this weekened, my boyfriend is away for work this weekend so id prefer to have his help rebuilding the turbo.) but when the cav is back together Shannon I can swing up to your area and meet with you if you'd want? If you guys would like to see my file let me know and i can email it to either of you. I have my latest logs as well as my latest tuning files.
I mean I cant be the only one having this problem, and if i am than it cant be the ECU, lol. I was hoping to hear input from others that have actually dealt with this as well. I mean I can drive the car in a way to avoid it but its so sensitive, i have to consider the gear im in, the throttle im at, keep an eye on the boost gauge, the speed im at, etc.. everything contributes in different ways on how it reacts to everything. So it'd be a pain, but certainly possible
No need to take any long drives, I'm in Manchester every day. I'll be in town at the shop tonight until at least 9:00, probably the same story next week, too. My wife and I carpool and sometimes she has to close, so I stay around until she's done.
seems like the best idea anymore for boosted Jbodies is Megasquirt or Greddy Emanage.
When my next turbo cav comes chances are I will be squirting
LE61T PTE6262 Powered
QBE - My turbo makes me squirt too... sorta...
lol... in a girl way?
Shannon - Ill PM you my # and maybe next week we can get 2gether
You left it out there
i had too hehe
Why don't you have it anymore? I miss mine right now
Its down for a few minor fixes/adjustments and i just haven't really had the time.... Driving the SS just doesn't do it for me...
oh @!#$! that sucks... all your hard work and effort
I dont think i could ever sell my car... Its my pride & joy
