Hey guys I figured id share my experience and also maybe look for a little bit of input on it. I have a 8-9 psi pulley on my car and wanted to see if I could squeak by with a fmu so I took my vortech fmu recalibrated it to 12:1 I believe and took it for a spin. I was noticing my afr got very lean right at vtec right around 14.5-15 but dropped all the way to redline where it got to about 12.5. This was a little bit leaner than I wanted so I decided to install the comptech fmu. It is adjusted as rich as it will go and its odd it does the oppisite of the vortech at vtec it drop to 10:1 and quickly jumps up and I was seeing mid 13s at redline. The vortech is a little lean but if it would stay 12.5 from vtec to redline I would be ok I dont understand why it has the big lean spot there. I also dont understand why the vortech decides to go super rich at vtec than leans out. Any input would be great.

Oh and one question about the comptech since I cant find instructions anywhere I went with markings on the fmu does the fitting on the side go to the fuel rail and the fitting on the bottom go to the return line? Thanks for any help I will most likely be installing a smaller pulley unless anyone has any suggestions but I am interested in why both fmu's are so different.

 

Yes the side fitting goes to the fuel rail.

I have found that 8psi is about all you can get out of the comptech fpr and stock injectors. I have no experience running the VT regulator, except that I prefer the CT because it has an external adjustment. The comptech fpr had two versions available for the S2000 with a different fuel ramp up rate (a steeper fuel curve for the ap2 fpr) Either regulator housing can be modified internally to change the fuel curve however. The adjustment on top just pre loads the spring to increase fuel pressure over the existing fuel curve/ramp up rate. Running low and high boost with the comptech regulator, I have found that under vtec it notoriously runs rich, followed by a lean spike at vtec transition (which is common anyway) If the afr continues to get leaner towards redline, then likely your running too much boost and the fuel pump or injectors are not keeping up, the CT fpr should be the same or richer at 8-9k as it is at 6-7k for example.

The typical safe afr with the Comptech fpr without any other fuel correction devices would be in the upper 10's- low 11's prevtec, followed by a vtec transition spike of 12.5-13.3 tapering down to 12.5 and usually a bit richer in the 11.5-12 range at redline. This is with stock boost 5.5-6psi. Adjusting for more pressure to run 7-8psi will keep the same afr curve but the prevtec pressure usually gets richer to try and keep the above vtec in check. Its a finite balance to find. This is why the vafc was a popular upgrade for a base CT kit, because you could lean out that prevtec curve and gain some performance back, lowering vtec is also a nice feature. I still rely on one today. On top of this, I eventually began experimenting with Water/meth injection and ended up being able to run 13psi. So anything is possible if you are hands on and dont mind playing some trial and error. other then myself, you wont find much in the way of insight into this arena. Most just stick to the recommended psi for the fpr and then go with a piggy back or full standalone.

 

So the comptech FPR is different between ap1 and ap2? How can they be changed internally?

I think I'm using an ap1 regulator on my ap2. Is this bad? The supercharger isn't on yet, but the wideband shows 10.7 to 11 while flooring and it moves a lot between 14-15 while cruising. Normal?

 

Yes, the f22 consumes more fuel then an f20, it also has a shorter rev limit, so the recalibrated fpr has a steeper fuel ramp up. other then changing out the spring and diaphragm, I've never gotten into the deep internals of the fpr, you should get some instruction from CT-Engineering on that, I'm sure you can order a kit to change it. My guess is your fuel curve is goign to be further off base then it would be normally, even with adjustment ie: too rich in one area and lean in another. But your wideband will tell you more then I can, follow it and do whats appropriate to get your afr in line. If you plan on sticking with the fpr for a wile, I'd recommend investing in a vafc to get better control of your afr. Yes 14-15afr wile cruising partial throttle is normal, it should sweep back and forth.

 

Hmm ok, well I'm not sure if the fpr I have was originally for an ap2 or ap1, so I guess I'll have to wait and see.

One thing I'm a little concerned with is before the engine is completely warmed up, once I start to head out of my complex, the car will buckle...just for a second. This is only every once in a while.

It only happened right after I installed the fp and FPR. Wideband doesnt show anything so I'm not sure if the computer is adjusting or what. I haven't pulled the battery cable yet.

I did notice too that with the ct FPR, there is a knocking sound I can hear in the cabin. Its faint, but there. Normal?

So the Vafc was wort it? Really at this point I'm looking for reliability more than anything. How does this add to the complexity?

 

I called up comptech and they confirmed the steeper curve when using the ap2 regulator. BUT they also said it was not necessary and that even the supplied comptech fmu that comes with the SOS Kit is for an AP1, but is advertised as ap1 and ap2 universal.

They also mentioned the fpr rebuild is $100, and in order to change my ap1 regulator to an ap2 specific, they would have to change the lower half of the housing. At that point it would be more cost effective to just buy a whole new one from them.

Also the faint knocking I had went away after I put the black fuel rail cover on.

 

I called up comptech and they confirmed the steeper curve when using the ap2 regulator. BUT they also said it was not necessary and that even the supplied comptech fmu that comes with the SOS Kit is for an AP1, but is advertised as ap1 and ap2 universal.

They also mentioned the fpr rebuild is $100, and in order to change my ap1 regulator to an ap2 specific, they would have to change the lower half of the housing. At that point it would be more cost effective to just buy a whole new one from them.

Also the faint knocking I had went away after I put the black fuel rail cover on.