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

[gkomo]

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.

With the FMU disk i have it in currently (came with the kit) i believe its a 12:1 disk... so i'm probably seeing 100+ psi of fuel pressure at max boost. Then again, i never seem to hit max boost anyways so at 12:1 and only ever seeing 2psi i should be seeing like 24 extra lbs of fuel pressure or a total of mid 60's fuel pressure in the lines. Like i mentioned before, maybe the return line can't displace all that extra pressure fast enough.

However, that doesn't explain the high 11 to mid 12 AFR when just normal driving.

Any one ever able to confirm the A9L doesn't use its decel fuel cutoff programming?

 

[Noobz347]

Like i mentioned before, maybe the return line can't displace all that extra pressure fast enough.

I don't think this is it. I ran an FMU on my 86 with SD for [years] and never saw an issue like that. I have heard of them being slow and sloppy before though.

I'll have to look around and see if mine is still around somewhere. If it is, I'll just box it up and send it to you. It's been a long time since I laid eyes on it.

 

[gkomo]

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.

Is it common to only have 2 psi up to the high 4K rpms then expect the the other 4psi to hit from 5k to 6,200?

My first go at a supercharger so I’m not all knowledgeable but I was thinking like 2psi at 3,500rpm or something then gradually increasing as rpm’s rise.

 

[Noobz347]

It is normal for a Centri to build with RPM.

You want instant boost, you need my setup.

 

[gkomo]

It is normal for a Centri to build with RPM.

You want instant boost, you need my setup.

So on a 6psi kit I shouldnt expect more than 2psi or 33% of boost up to like 75% of the rpm range? I get to enjoy 67% of advertised boost for only 25% of the time…

Damn, I should have done more research on the right kit to get! That’s pretty lame haha almost to the point of pointless.

It’s early and I don’t get much sleep with this damn baby but if my math is correct I should be seeing 3psi at 4,500rpm (assuming boost starts at 3k rpm and using 6k rpm as redline and boost curve is linear) which doesn’t sound like much difference but that’s like ~20% off.

 

[nicholase]

Is it common to only have 2 psi up to the high 4K rpms then expect the the other 4psi to hit from 5k to 6,200?

My first go at a supercharger so I’m not all knowledgeable but I was thinking like 2psi at 3,500rpm or something then gradually increasing as rpm’s rise.

Well, expecting 6psi is pretty optimistic. That's the base kit right? Real world you'll probably see 4.5 psi at the rev limiter. So seeing 2 or 2.5 at 4400 rpm doesn't seem unusual to me. Looks like 2.5 right before you lifted at 4400 rpm to me.

The whole idea of a centrifugal is for a rush of power from 3500 rpm (give or take) to the limiter. So if you're having to lift becasue it starts misfiring you're missing the best part lol.



I'd focus on why its cutting out at higher RPM. Has it been doing that always or just since the install? What have you tried so far for that issue? It would be interesting to see and hear that issue and see what your wideband is doing when it occurs.

 

[gkomo]

Well, expecting 6psi is pretty optimistic. That's the base kit right? Real world you'll probably see 4.5 psi at the rev limiter. So seeing 2 or 2.5 at 4400 rpm doesn't seem unusual to me. Looks like 2.5 right before you lifted at 4400 rpm to me.

The whole idea of a centrifugal is for a rush of power from 3500 rpm (give or take) to the limiter. So if you're having to lift becasue it starts misfiring you're missing the best part lol.



I'd focus on why its cutting out at higher RPM. Has it been doing that always or just since the install? What have you tried so far for that issue? It would be interesting to see and hear that issue and see what your wideband is doing when it occurs.

I almost 100% don't believe i ever experienced that issue pre-supercharger... its very noticeable so i think i would remember. BUT, i hardly drove the car much before putting the supercharger on so what i don't remember is if i ever even revved it out pre-supercharger to even get it to replicate the issue.

The only thing i've done so far to try and remedy the problem is close the gap on the spark plugs from .054 down to the .043 area, which didn't help. That and just confirming my gauge isn't bad, which it isn't (verified with hand vacuum pump).

What i do want to do is 1. do a smoke machine test and 2. spray soapy water on all the supercharger couplers with the engine running to see if any little bubbles form. I'll see if any loosened up on me and tighten them all snug again. Maybe i'm getting a leak only when pressure increases.

I forgot to take a video last week, but i'll try and get a video of all the gauges up to when it cuts out and see what they show. Just from reading online... the 'symptom' seems like spark blowout just based on other people descriptions. Car literally just falls flat, makes no weird noises (pops or whatever), and drives back to normal once below the 'threshold'.

 

[gkomo]

Ok I stand corrected on the boost psi. Revved it out until it cuts out and I think I saw almost 5psi.

So ya here’s a video of it going up till it does its cut out thing:


View: https://youtu.be/0K3bLIA253k?si=6UADcjYUTxYW0ApW

 

[Noobz347]

Now you know why Centri owners almost always have gears.

 

[gkomo]

One weird thing is I smelt like a burning smell at the high rpm but it goes away immediately. That smell I have smelt before when doing this.

 

[Noobz347]

View: https://www.youtube.com/watch?v=J4j7ggZqbiU

 

[gkomo]

The AFR gauge showed in the 10’s on that pull… is that too rich? Gauge is kinda hard to read on video but I rewatched and rewatched the video on my phone and I can clearly see 10’s.

I think I’ll focus on the ignition side and spark blowout. I believe everything is OEM (old) or OEM (new) replacements I.e. cap/rotor/plugs/wires. Maybe my coil is getting up there in age.

 

[gkomo]

Are there any companies that rebuild OEM distributors? Just thinking out loud… could be nice to have one I know is solid instead of trusting one with an unknown history/condition.

 

[RaggedGT]

 

[gkomo]

I’ll need to research how to test ignition components then.

 

[nicholase]

Ok I stand corrected on the boost psi. Revved it out until it cuts out and I think I saw almost 5psi.

So ya here’s a video of it going up till it does its cut out thing:


View: https://youtu.be/0K3bLIA253k?si=6UADcjYUTxYW0ApW

Nice. Looks like a solid 4psi at 5k.

I can't really hear what's going on there at the end. I really doubt it spart blowout at those levels, but its easy and cheap to try.

I'd be tempted to try a coil, but thats just tossing a dart.

On that set up how does the inlet tube attach to the MAF? I forget. Is it that dryer hose stuff directly to the MAF? If it is I'd check that real good. Any leak there would cause problems and problaly get worse at higher RPMs due to the suction increasing.

 

[gkomo]

Nice. Looks like a solid 4psi at 5k.

I can't really hear what's going on there at the end. I really doubt it spart blowout at those levels, but its easy and cheap to try.

I'd be tempted to try a coil, but thats just tossing a dart.

On that set up how does the inlet tube attach to the MAF? I forget. Is it that dryer hose stuff directly to the MAF? If it is I'd check that real good. Any leak there would cause problems and problaly get worse at higher RPMs due to the suction increasing.

Ya drier hose connected straight to the MAF. Maybe I have my MAF clocked incorrectly? It’s not sitting flat/level but more at an angle towards the engine.

I have a new Motorcraft coil I could try… just need to find it in all my stuff.

And there’s really nothing to hear the car just instantly stops making power but even I can’t hear any discernible noise of anything happening.

 

[AeroCoupe]

With regards to the OEM distributor. Get on car-part.com and search for 1993 Mustang distributor. Find one with low miles and buy it. Chances are everything is good and it just needs to be taken apart, cleaned up, and reassembled with a new cap and rotor.

I did this and between the distributor I bought and spare parts I had laying around I have a complete spare distributor for about $75.

If you need a TFI module about the best replacement is a Standard Ignition LX 218.

If you need a pickup module or PIP about the best one is a Standard Ignition LX 222.

 

[gkomo]

With regards to the OEM distributor. Get on car-part.com and search for 1993 Mustang distributor. Find one with low miles and buy it. Chances are everything is good and it just needs to be taken apart, cleaned up, and reassembled with a new cap and rotor.

I did this and between the distributor I bought and spare parts I had laying around I have a complete spare distributor for about $75.

If you need a TFI module about the best replacement is a Standard Ignition LX 218.

If you need a pickup module or PIP about the best one is a Standard Ignition LX 222.

Awesome I’ll look into this. Although I’ll need to see if I can specify mileage on car-part… not sure if I can.

I do have a spare TFI module that I tested and is good (thank you to whoever linked the video to test those).

 

[AeroCoupe]

They typically list the mileage of the car the part comes off of.