"Tuning" Vortech kit with FMU discs- question

[nicholase]

I have a stock 90 GT other than a full exhaust. I installed a Vortech kit . I am using the included FMU, BTM, and Trex w 255lph HP intank pump. I'm getting around 7lbs of boost. I did install a UPR power pipe and mounted the stock MAF in the fender well.

I am using AEM boost/ AFR and FP guages to "tune".

I started out with the standard 12:1 disc for the 19lb injectors.

The AFR guage reads:
Idle 14.7
Cruise 14.5
WOT dips to 12 and steadily drops to 9.0. This seem pretty rich.

I installed the 10:1 FMU disc
The AFR guage reads:
Idle 14.7
Cruise 14.5
WOT dips to 12 and steadily drops to low 10's.

I'm wondering if I should try the 8:1 disc? I'm not wanting to lean out and melt anything. I'm not trying to extract every bit of power. I also don't want it so rich that I'm washing down the cylinders and covering O2's and wideband in soot.

Is there anything I'm missing here? I'm thinking to try discs until I get around mid 11's at WOT full boost / max RPM. Does that sound right?

I don't want to make any rookie mistake here. Thanks for any info.

 

[Noobz347]

Yeah, try giving your base timing a little tickle. Just a degree advance.

 

[nicholase]

Thanks for the reply. Right now I'm set at 10° base and using the BTM at 1. I checked it with a pressure tester. So I should be running 19° total advance at WOT near redline. Which I'm figuring to be safe. I'm not hearing any detonation at all.

Mostly just worried about using an 8:1 disc (which is suggested for 24lb injectors) with my stock 19's. Maybe Vortech calibrated the discs for the stock pump and Trex? When replacing the stock pump to a 255lph and using the Trex it's more fuel than they are calibrated for? I dunno.

I'm assuming I just use whatever disc combination that gets me in the mid 11's as I near redline at max boost, which is 7psi currently. If I'm off on this line of thinking please let me know.

Thanks for any insight.

 

[Noobz347]

There are multiple ways to affect AFR in any given range.

It can also be affected by the robustness of your ignition system.

The point is that the AFR ratio is not the only way to 'adjust' AFR in your circumstance and the possibility also exists that you may not be able to get it 'perfect' without a digital tune. The issue there is that if you're going to go [that] far, you may as well ditch the FMU, the in-line pump and do it all up with larger injectors and a high volume in-tank pump.

If you're hyper focused on the just the FMU disk tho... Let us know what you come up with.

Another wrinkle in the whole mess is the inadequate power supply to both, the fuel pump and coil through the entire useable rev range. It is not consistent.

 

[AeroCoupe]

Fuel pump voltage can be solved with a 30amp relay mounted in the trunk with a 10 gauge wire from the battery for the power supply to the relay. Use the old pump 12V supply for the trigger wire. This will ensure you have enough amperage and the voltage will be much more stable. I did this on my Coupe and it’s loads better.

 

[nicholase]

There are multiple ways to affect AFR in any given range.

It can also be affected by the robustness of your ignition system.

I think my ignition should be pretty solid. All the connections are clean. I put in a new Motorcraft TFI and I'm using the MSD6BTM (6Al, BTM combo), Performamce Distributors Screaming Demon coil, and 10.4 mm livewire plug wires. I gaped the plugs to .35 but then raised it to .40. Maybe I should bump that up more as it holds up fine to the rev limiter. See if that makes any difference in the AFR?

The point is that the AFR ratio is not the only way to 'adjust' AFR in your circumstance and the possibility also exists that you may not be able to get it 'perfect' without a digital tune. The issue there is that if you're going to go [that] far, you may as well ditch the FMU, the in-line pump and do it all up with larger injectors and a high volume in-tank pump.

If you're hyper focused on the just the FMU disk tho... Let us know what you come up with.

I'm hoping to get through the summer with it as is. It's just a weekend toy I take out on nice days. Then debate over the winter if I want to go deeper. I did find a reputable tuner about an hour away so that might be an option if I want to do a HCI and other things.

It actually runs great. But the low 9's richness under boost with the 12:1 disc was blowing soot and I had some gas smell in the oil. I changed the oil and swapped discs to the 10:1 and it definitely got better.

At this point I'm not really looking for a perfect tune and I realize the FMU / BTM is old school. Just wondering how close I can get and not wanting to burn anything up.

I should probably leave the 10:1 disc and get through a few different weather patterns. It's hot as balls right now. Might get leaner when the humidity and heat calm down. Maybe with this old school FMU 10's at max boost / rpm isn't a terrible thing. It is in the 11's for most of the pull.

If you're hyper focused on the just the FMU disk tho... Let us know what you come up with.

Will do.

Thanks again for the feedback.

 

[nicholase]

Fuel pump voltage can be solved with a 30amp relay mounted in the trunk with a 10 gauge wire from the battery for the power supply to the relay. Use the old pump 12V supply for the trigger wire. This will ensure you have enough amperage and the voltage will be much more stable. I did this on my Coupe and it’s loads better.

Thanks for the info.

I'm running a 130a PA performance 3g alternator and it seems to output pretty well. I did a few things different than the vortech manual. I passed on mounting the relay in the trunk and using the cigar lighter fuse as power. I put the relay under the driver's seat next to the factory fuel pump relay which I used as a trigger for the TRex pump relay. I also mounted my guage relay there. I ran 10ga power and ground from the battery to the relay and then back to the TRex.

The factory fuel pump bracket conveniently has places for a couple more relays. Just have to drill a hole in it, slide a clip nut over the hole and bolt the new relay to it.

 

[Noobz347]

Just for reference and informational purposes:

When I initially installed my Kenne Bell, I fought 'gremlins' in the AFR vs. RPM for a time.

I eventually solved the issues with two things:

Kenne Bell Boost-a-Pump - This is nothing more than an adjustable voltage regulator specifically for the pump. It keeps the pump at a constant voltage regardless of current draw over my 38 year old wiring and electrical signal. [Side Note: I do not use their boost pressure switch. I just keep the pump saturated at a constant voltage]

Kenne Bell Boost-a-Spark - Same thing only, it keeps the coil saturated.

Other manufacturers make similar components. Air On/Off, Lights On/Off, etc... doesn't matter to those two components anymore.

 

[Cheapskate207]

I love that you’re using some old school tech with good results. I considered doing that with my first gen lightning and kinda regret not.

FWIW I had my HCI 7 psi vortech car dyno tuned and the (reputable) tuner was happy with 11:1 afr.

There’s probably a million cars with the same setup as you running the 12:1 disc so it’s probably fine, especially with the 10:1. If it were me I’d likely try the 8:1 and see how it works. Back out if it’s lean, put the 10:1 back in and enjoy it indefinitely.

 

[Noobz347]

I ran a similar setup with my KB when I got it. The [tweaks] that I employed to get it right are not tweaks that I would prefer to relay over a forum.

On a side note: The 19 lb injectors used in this setup are being pushed way beyond spec and it is a [really] good idea to have them all flow tested and adjusted so that they all squirt the same.

It only takes one weak injector to throw the whole damned thing off.