Progress Thread Komo's 1990 GT - Parts Gathering Purgatory & Home Remodel

Noobz347 · Apr 29, 2026

For an A9L (I'm certain others are similar):

When you lift off the throttle, the ECU transitions into Closed Throttle Mode and then:

1) First: Decel Fuel Lean-Out (ramp-down)
2) Then (if conditions are right): Decel Fuel Shutoff (DFSO)

You can feel the two stages if you start decel at a high enough RPM.

Level off the gas, you will feel some engine braking.
Lift off the gas, you will feel a lot of engine braking.

Noobz347 · Apr 29, 2026

We should also remember that you're running an FMU.

If that is pinching off the return during decel...

gkomo · Apr 29, 2026

I had thought maybe there is residual pressure from the FMU during decel that the return line can’t displace fast enough, but it shows these conditions even decelerating at like 1,500 rpm’s without previously getting up into higher rpm’s at all. I don’t think the FMU is even doing anything if I’m not or was not in boost.

My future plans are to run 24lb injectors with the 8:1 FMU disk to ‘safely’ (I know safely and FMU in the same sentence is probably a sticky point) run my power levels as well as lower fuel line pressures.

Side note: Not a lot of information about how much power 24lb injectors can support supercharged WITH a FMU… most injector calculators just show NA or boosted (I couldn’t find any that account for a FMU in the equation). I plugged all my information into Claude (and it showed all its calculations) but it stated that with 24lb injectors with boost running a 8:1 FMU disk at 85% injector duty cycle it should support 386hp.

gkomo · Apr 29, 2026

One other thing to note, in open loop it does spike lean on decel. Only when the engine is fully warmed up (in closed loop?, Hope I got those right) it shows rich on decel.

Noobz347 · Apr 30, 2026

gkomo said:
My future plans are to run 24lb injectors with the 8:1 FMU disk to ‘safely’ (I know safely and FMU in the same sentence is probably a sticky point) run my power levels as well as lower fuel line pressures.

Why on Earth would you spend money on another FMU setup?

Put on the big boy pants, get some 42s and a tune.

gkomo · Apr 30, 2026

Noobz347 said:
Why on Earth would you spend money on another FMU setup?

Put on the big boy pants, get some 42s and a tune.

I'm struggling with the tune aspect because i have to pass SMOG. Don't get me wrong, i haven't researched to the bone, but most aftermarket ECUs are not SMOG legal because they don't have any provisions for controlling SMOG equipment.

Does a MOATES quarterhorse keep all that stuff functional? I'm assuming since its just a piggy back on the ECU basically. If thats the case then maybe i'll purchase the MOATES setup. However, i have no idea if there are any tuners in my area familiar with BinaryEditor and all that.

The 24lb injectors and FMU disk are just a bridge until i can figure out exactly how i'm going to tune this thing. However, why do FMUs get a bad rep? Their function is fairly straightforward and with the lower disk ratio fuel pressures aren't extreme.

Anyways, for all i know, i'm years away from that after 'probably' needing to spend $5k+ on an engine rebuild.

Noobz347 · Apr 30, 2026

gkomo said:
I'm struggling with the tune aspect because i have to pass SMOG. Don't get me wrong, i haven't researched to the bone, but most aftermarket ECUs are not SMOG legal because they don't have any provisions for controlling SMOG equipment.

Try to keep your A9L. Call a dyno shop in your area. They should all be experts on the local laws etc.

gkomo · Apr 30, 2026

Hmm, looks like there is a tuner here in SD.

DMP! Automotive Performance Tuning

DMP Dantes Modular Performance is the premier Southern California Dyno Tuning, and all your Automotive Performance needs! Located in National City and serving greater San Diego.

dantesmodularperformance.net

i'll give them a call.

AeroCoupe · Apr 30, 2026

I am not 100% certain but a chip like an SCT will trigger a Code 15 which I believe will trigger a CEL which is no bueno if they are looking for that. Not sure if the Moates Quarterhorse will do that or not.

gkomo · Apr 30, 2026

I'm probably getting a head of myself again. Nothing is going to happen until September or later anyways.

On another note, i was able to get my UPR vacuum tree bolted back to the firewall by running a new rerouted vacuum line from the brake booster:

No pinches in the line and its only like a couple inches max longer than the OEM one i took off.

gkomo · Apr 30, 2026

So I’m still fighting the boost gauge only showing like 2psi. It spikes to around that area then just stops flat. I took a video this time:

View: https://youtu.be/LsM7CPopHdk?si=0F83yE7D5gZQ0pFQ

Might need to zoom in on the boost gauge watching it.

What are some other ways to troubleshoot low boost besides just looking at the gauge?

Noobz347 · Apr 30, 2026

I want also want to see what the P,S and Is are doing when you [Decel].

gkomo · Apr 30, 2026

I can take another video, but it shoots down to like -25 to -30hg of vacuum.

gkomo · May 1, 2026

Here’s a full video of a 3rd gear pull where it spikes to 2 psi and stays, plus the decel:

View: https://youtu.be/_W8C6EwjBlo?si=gQYcDBHArtxbyNws

nicholase · May 1, 2026

PSI looks good to me. I slowed down the playback to 40% and it looks like its climbing all the while.

Gotta take it to the red portion of the RPM guage, or at least the yellow All your clips were lifting around 4k or 4.5k. These things make more boost the faster they spin.

gkomo · May 1, 2026

nicholase said:
PSI looks good to me. I slowed down the playback to 40% and it looks like its climbing all the while.

Gotta take it to the red portion of the RPM guage, or at least the yellow All your clips were lifting around 4k or 4.5k. These things make more boost the faster they spin.

Haha, remember, my car completely cuts out at like 5,200-5,500rpms... Actually... i'll get a video of it doing that and see what both gauges are reading. Could be useful information.

Noobz347 · May 1, 2026

gkomo said:
Here’s a full video of a 3rd gear pull where it spikes to 2 psi and stays, plus the decel:

View: https://youtu.be/_W8C6EwjBlo?si=gQYcDBHArtxbyNws

Your vac gauge on decel looks really good (thinking back to your rich on decel issue). 13ish on the AFR meter does look fat for decel though.

gkomo · May 1, 2026

Noobz347 said:
Your vac gauge on decel looks really good (thinking back to your rich on decel issue). 13ish on the AFR meter does look fat for decel though.

Under normal driving conditions it will dip into the high 11's low 12's just putzing around during decel.

Noobz347 · May 1, 2026

gkomo said:
Under normal driving conditions it will dip into the high 11's low 12's just putzing around during decel.

I have a lingering suspicion about your FMU lagging. Either, it's seeing boost a moment longer because of how/where it's hooked up --or-- something with the FMU diaphragm itself.

All I have are suspicions though.

gkomo · May 1, 2026

Since i don't have access to my smoke machine at the moment - if i removed my 'source' line on the vacuum tree and hooked up my little vacuum pump to that port, would the little pump be able to pressurize everything else connected to the vacuum tree to see if i'm leaking anywhere else within those connections? What would be left would be the FMU, Brake Booster, A/C, Cruise Control and Boost Gauge. Not sure if that pump is strong enough.

Also, I switched out my new Paxton oil fill neck to airbox filter with a clear one... i've never seen nor smelled (prior to getting the clear filter) oil in this, but i'm starting to see some. Would this be any indication of something wrong?

Its kind of hard to see but the filter has some light oil like from the halfway mark going right towards the airbox. Its pretty faint in the picture. By 'wrong', i mean like does that mean my PCV can't keep up with the crankcase pressure?

Progress Thread Komo's 1990 GT - Parts Gathering Purgatory & Home Remodel

Stangnet Facilities Maint Tech... Er... Janitor

Stangnet Facilities Maint Tech... Er... Janitor

now i can hopefully expect to receive the shaft

now i can hopefully expect to receive the shaft

Stangnet Facilities Maint Tech... Er... Janitor

now i can hopefully expect to receive the shaft

Stangnet Facilities Maint Tech... Er... Janitor

now i can hopefully expect to receive the shaft

lube between the nut and the face. I know my lubes

now i can hopefully expect to receive the shaft

now i can hopefully expect to receive the shaft

Stangnet Facilities Maint Tech... Er... Janitor

now i can hopefully expect to receive the shaft

now i can hopefully expect to receive the shaft

I lubed and pushed, until it was all the way in

now i can hopefully expect to receive the shaft

Stangnet Facilities Maint Tech... Er... Janitor

now i can hopefully expect to receive the shaft

Stangnet Facilities Maint Tech... Er... Janitor

now i can hopefully expect to receive the shaft

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