Microfueler: Operation Q’s (Technical)

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13rus
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Microfueler: Operation Q’s (Technical)

Post by 13rus »

Does anyone know exactly how Microfueler operates? ‘87 CTTC.

What I understand is:
- Using fuel from fuel rails, Microfueler opens auxiliary injectors by certain percentage (injector duty) at certain boost level and ramps up fueling based on increase in boost.

What I am looking to find out:
- At what boost level does MF begin opening injectors?
- What is the ramp curve, in other words, is it linear and boost only referenced or are there other reference inputs such as load, etc?
- What is the amount of fueling in CC’s (or gph or whatever measure) at the beginning of auxiliary fueling on stock aux injectors?
- What is the amount of fueling at maximum referenced boost level on stock aux injectors?
- What is the aux injector duty at initial open? Max duty?
- Overall I would like to find out how much additional fuel is being supplied under which conditions and any other technical details on MicoFueler operation are very welcome.

Reading MF threads, I also understand that replacement of MF with aftermarket units is recommended. Is there a consensus on which unit is the absolute best?

Many thanks all!
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SurfnSun
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Re: Microfueler: Operation Q’s (Technical)

Post by SurfnSun »

The microfueler starts at positive manifold pressure.

I never found it to be very adjustable, but may it was just me. Seemed off or on. I was making a lot more power and we needed more fuel.

I can’t help with the other questions, sorry.
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Re: Microfueler: Operation Q’s (Technical)

Post by undercover »

The microfueler is a basic analog setup. It has 2 inputs, boost and RPM. It is non-programmable, but there are pots inside to adjust the 'gain' of duty cycle for boost and RPM. Being analog, I assume it's a linear relationship, but I don't know for sure.

I believe Callaway just dialed them in on the dyno when the cars were built, and they erred on the side of going way rich to protect the engine from failure due to lean condition. In the past others have gotten some performance gains by re-tuning the microfueler, but much more can be had with modern, digital setups.

I can't really answer any of your other questions because there's no 'map' that you can look at like a digital unit would have. You'd have to test for those values on a bench with an oscilloscope.

Any modern additional injector controller that can drive 2 low-impedance injectors (or high if your change out the injectors) will work and will provide a big improvement in tunability over the microfueler. An example would be the split second AIC (www.splitsec.com).

I'm going to go the route of letting the main ECU handle everything, which will allow for much more control over things. I did a write-up on some options on here a while back:

https://callawayownersgroup.com/viewtopic.php?p=25920

Hope this helps, and glad to see others on here unshrouding the mystery of these wonderful cars!
1987 CTTC conv #147
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13rus
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Re: Microfueler: Operation Q’s (Technical)

Post by 13rus »

Thank you both! Good info.
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Re: Microfueler: Operation Q’s (Technical)

Post by SurfnSun »

13rus wrote: Wed Jan 19, 2022 10:57 am Thank you both! Good info.
I ended up going with a high pressure fuel regulator and a custom tune to get the fuel we needed on the dyno.

Another b2k owner kept the stock tune and used the previous analog version of this device. Id give them a shout if you want aftermarket.
http://www.sdsefi.com/eic.html
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