i have a FMU and i run 8 psi but during accelleration when im not flooring it fully maybe only 3/4 of the way m y air fuel reads way lean till i let off gas then it quick goes to rich for a sec or two. at full throttle it reads all rich but i just dont wanna damage anything if this is a prob. if i spool up gently or full throttle its ok though??

91 civic hatch, homemade turbo+ LS motor = 12 sec street car.

sounds normal to me. as long as its not dangerous lean you should be ok.. you should have a wideband to know for sure. don't tune by an idiot light.

^^^what he said.

Kevin
The old:


The new:

Thats the ECU staying in closed loop during boost, and its still reading off of the o2 sensor to keep the A/F around stoich(14.7:1). There really isn't much of a way around this with that setup.. Either boost it a bit lighter, or put it to the floor, to kick it into open loop. As long as you are not getting any detonation, and you dont go though all the gears like that, then it should be fine. This is another reason I'm really going to like the Megasquirt.

13.5 @108 MPH-2.2 60ft(stupid FWD!)
S16G @ 18 PSI/FMIC/Running on MegaSquirt II (Now with sequential
fuel injection)
My webpage: http://eclipsed4evr.home.comcast.net
-1998 Mitsubishi Eclipse RS-T- "Toy"
-1992 Plymouth Laser Turbo AWD(SOLD)
-2000 Honda CR-V(daily)

I always found this to be extremely annoying. It always made me nervious seeing the stock ECU trying to lean things out if I didn't have my foot mashed into the floor while in boost.

A long time ago I cooked up a quick and dirty solution to the problem - a relay that clicks on at atmoshperic pressure and switch the TPS signal wire to a ~3.8 volt (100%) refrence. This makes the ECU think you are at full throttle and will start open loop operation. My little gadget worked, but not as well as I hoped so I stopped using it. I was too lazy to perfect it. When I picked up my 034EFI a while back it partially solved this problem, however, the real solution is to stop using the stock ECU entirely.

2016 WRX STi Limited (current)
2001 A4 1.8tqms (donated)
1991 GVR4 #1933 (sold)
old.dsmregistry.com/detail.php?carid=218 (dismantled)

I've thought about this question alot. I don't think it's as much of an issue because it's at part throttle. Remembering that it's really about how much air gets pumped into the cylinder and not what the pressure in the manifold is at, with the throttle partially open we are substantially limiting the amount of air that can make it into the cylinder during the intake stroke. Since the amont of a/f mixture is considerably less, we should not be seeing obscenely high cylinder pressures. With the low load being placed on the motor at the same this should be safe.

Now I could be way off. This is just how I've rationalized it. This also depends on what you mean by "lean". Is lean like 15:1 or is lean like 13:1 to you? I do think there could be issues when you ride the line between high load and low load conditions. Basically when the car goes from open to closed loop operation (or is that the other way around ... I can never get that straight), there might be some points that you'd like it to be a little richer than it is.

Now I'm curious as to what a stock turbo car's A/F curve is at partial throttle experiencing positive pressure.

-"Easy Mac"
05 Mazda RX-8 (RR8 #88)
99 Eclipse RS 398whp & 372lb-ft

ok well it reads all the way lean on a/f gauge so i dunno. why does ecu stay in closed loop mode any way? cant i somehow make something to stop that? i dotn like running lean at all .

91 civic hatch, homemade turbo+ LS motor = 12 sec street car.

Yeah I hate that lean thing too. I wonder if it is like that all all non-turbo cars with an aftermarket kit?

I was wondering, if it says "lean" on you cheap regular a/f gauge, will it say "lean" on a wideband?

New Car:
2004 350z base, Nismo CAI, pioneer avic-n1 (dvd, cd, navi)



Old Car:
1998 GS with hrc stage 2, HID 6000k conversion kit, AEM UEGO wideband, sfmu, ml, prokits, Greddy warning gauges: egt, boost gauge, and oil pressure, apexi tt, haydans tranny cooler, costum dp, groundwires, dynotune fp gauge. gst muff, turbo spoiler
Boostin since Aug 03.

nothing like driving with the windows down and the music low: i love hearing the turbo spool, swwwhhhttt!!!!

The ECU is still seaking to 14.7:1 A/F becuase its in closed loop. at partial throttle load levels, this is 100% a non-issue and if any of you had the resolution of a real wideband, you'd see what it's doing and realize the same thing.

Lean != knock. Not always. High EGTs != knock. Not always. Boost and 14.7:1 A/F in closed loop may look lean on your Gadgetseller gauge, or your blinky Autometer, but i'd bet money it's not knocking and you don't have anything to worry about.

______________________________
If a sentence found online has 35% misspellings or greater and includes at least two racially charged expletives, chances are it is a YouTube comment.

'95 Eclipse TurboGS (garage deco)
'95 TSi AWD (restoring a survivor)
'97 Talon ESi-T (poor impulse control)
'99 Eclipse RS-T (daily beater)
'13 Evo X (mostly stock)
'17 Sienna (Middle Aged Dad Mobile)



Factory Service Manuals: http://nawdu.de/files/

hmm.. all this happened cause i fixed a boost leak i found i had. i never knew ... oh well as long as it dont hurt it, this is my only car. Why does ecu stay in that closed loop during boost anyway? what makes it do that.

91 civic hatch, homemade turbo+ LS motor = 12 sec street car.

cuz our PCM doesnt know what boost is, and you prevent the PCM from seeing boost, so it doesnt even know its boosting.

2005 Legacy GT Ltd, Garnet Red Pearl
speak softly and spool a big turbo

The inputs required for open loop operation are not met at a part throttle cruise, boost or no boost. Boost is not part of the equation at all.

______________________________
If a sentence found online has 35% misspellings or greater and includes at least two racially charged expletives, chances are it is a YouTube comment.

'95 Eclipse TurboGS (garage deco)
'95 TSi AWD (restoring a survivor)
'97 Talon ESi-T (poor impulse control)
'99 Eclipse RS-T (daily beater)
'13 Evo X (mostly stock)
'17 Sienna (Middle Aged Dad Mobile)



Factory Service Manuals: http://nawdu.de/files/

New Car:
2004 350z base, Nismo CAI, pioneer avic-n1 (dvd, cd, navi)



Old Car:
1998 GS with hrc stage 2, HID 6000k conversion kit, AEM UEGO wideband, sfmu, ml, prokits, Greddy warning gauges: egt, boost gauge, and oil pressure, apexi tt, haydans tranny cooler, costum dp, groundwires, dynotune fp gauge. gst muff, turbo spoiler
Boostin since Aug 03.

nothing like driving with the windows down and the music low: i love hearing the turbo spool, swwwhhhttt!!!!

ecu definately seeks 14.7 afr like dino said, proven with a wideband

_ _ _ _ _ _ _ _ _

96 Black ESi
91 Red TSI AWD (RIP)
02 WRX


"turnin wrenches for nine hours in the pouring rain, just to get the beast up and running again"

Aerospace Certified TIG welder for Precision Castparts in Portland, OR.

JoshSpair.com

the thing i cant figure out is why it never did this before. ive ran 8 psi for a while now and it never did this. it feels like its weaker to. . i dunno. at full throttle its ok but not at half throttle. the only time it felt like this was when my fmu gas hose had a small leak and gas was pouring out into my rug.. but i fixed that and it was better. now i changed my piping and fixed a boost leak and it feels like less power. and reads lean . .

91 civic hatch, homemade turbo+ LS motor = 12 sec street car.

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Built. That's All...
.........................................................................................................................
www.monkeybuttpirate.com
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2 Fingers of Scotch with a milk back... Stat!

Originally posted by BlackMagic

Originally posted by djtrickee

Originally posted by 97grnRS when my fmu gas hose had a small leak and gas was pouring out into my rug..

so you run your fuel lines through the interior of the car??? you're kidding right?

maybe his garage is carpeted?

.........................................................................................................................

Built. That's All...
.........................................................................................................................
www.monkeybuttpirate.com
.........................................................................................................................
2 Fingers of Scotch with a milk back... Stat!

this pisses me off alot... losing power

91 civic hatch, homemade turbo+ LS motor = 12 sec street car.

I would recommend getting yourself a datalogger...you are now at the crossroads I have come too as well. I just recently had a turbo installed and I am having similar issues, except I am only leaning out for a breif second or 2 and then back to rich. Also when I let off the gas completely my car goes all the way lean not rich like you stated yours does. But I just ordered a datalogger to get figure out what is really going on. I think you would benefit from one as well. There are some for sale on dsmtuner.com for a good price that comes with everything you need.

Just something to think about, because if you are like me at all you do not want to take any chances. Maybe this lean spike during closed loop is normal...but more then likely it isn't!

Good luck, and I hope you get things figured out. I will keep you posted on mine as well.

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- 05 Subaru STi
- 97 eclipse gs (289whp w/ 276tq)