MechaGodzilla

So I got my Vortech SC on a Dynojet today and it gave some good numbers compared to my baseline on the same dyno prior to the SC installation.

Stock 199.3 hp / 133.7 ft-lbs
SC 289.1 hp /182.6 ft-lbs

So I got a 90 hp boost. Nice, however the AFR was above 14.0 at high revs, while an earlier dyno of the SC on a DynoDynamics gave a max reading in the low 13s. So my Vortech is running lean now. It was suggested however that if I switched to the Vortech "Super FMU" instead of the fixed FMU the kit ships with then I could richen it sufficiently without using electronics.

http://www.vortechsuperchargers.com/tech/fmu_sfmu.html

Anyone tried this?

MG

jerrypeterson

How is the Air/Fuel ratio being measured? Ideally, you want a reading from a wideband 02 sensor mounted pre-Cat in the exhaust path.

Stuffing a wideband into the end of the exhaust pipe is going to give really lean readings. At my last dyno they thought I was running a 19:1 A/F ratio. They finally concluded after 8 runs that the equipment must be giving false readings since my gauge was showing 12-13:1'ish and the engine hadn't blown up.

I'd make sure something is broken before you go through the trouble to fix it.

MechaGodzilla

Yes, just the usual sensor in the tailpipe, typical of dynos, so the accuracy isn't absolute.
But the before and after SC installation delta in the AF ratio should
indicate at least the relative change, and that still suggests my car is leaner
than stock. It may be prudent to at least bring it down to those original levels, as measured at the tailpipe.

MG

jerrypeterson

Just have a bung welded into the header post-collector and tell the shop to plug in there. Probably cost you $50 for the mod and it will afford you the most accurate A/F reading possible.

Yellow Streak

[QUOTE]Originally posted by jerrypeterson
[B]Just have a bung welded into the header post-collector and tell the shop to plug in there.

jerrypeterson

[QUOTE]Originally posted by Yellow Streak
[B]

The shop that dyno'd my car put the O2 sensor in the cat.

Yellow Streak

[QUOTE]Originally posted by jerrypeterson
[B]

Possibly, but its still post cat.

jerrypeterson

[QUOTE]Originally posted by Yellow Streak
[B]

So when I buy a header, I can have a second bung welded in for dyno tuning?

Jenner

You could do it that way, but you will just be raising the fuel pressure to compensate. According to my fuel pressure gauge our Vortech kits are running at 100psi of fuel pressure at Wide Open Throttle. Raising the fuel pressure is just a bandaid and may not work because the injectors can only pulse so much at 9000 rpm. You will be putting the injector into 90% duty cycle, and may incur back pulsing.

I would suggest doing it with a VAFC. If you don't want to deal with a VAFC you could try going to larger injectors, and lowering the FMU from a 10:1 to a lower ratio in order to tune the injectors, but I still think you will need a VAFC to get the best fuel and power out of it.

MechaGodzilla

The guy at the shop said the S2000 injectors can handle 100psi, but if they are already at 100psi then raising the pressure probably isn't a good idea.
It always come back to a need for bigger injectors... The Vortech kit is pretty much setup to use the stock injectors to their fullest and gets extra power from the aftercooler despite the relatively low boost. This contrasts with Comptech's approach.

MG