Dynoed my car today

[dean]

I got 328 hp to the wheels and 316 ft.lbs. It is running a hair lean. I tried to richen it up but it didn't work very well. I will post a pic of the sheet.

[ZAMIRZ]

Damn dude, nice numbers! I like the torque curve =)

[ChrisBennet]

Nice!
-Chris

[beepbeep]

No, that's OK! It's nice to finally see pappers on how CIS does on WOT (i've been wondering for a long time). If it matters, I would like my engine to have your sort of fuel/air ratio.

You engine is producing max power around 5600 rpm and you are still under lambda 14:1 there. That's bloddy perfect!

Engines do produce their best power pretty near stochiometric 14.7:1 ratio, excess fuel trick is mainly for cooling purposes. Now your engine is from -75 thus first generation of 930 engines with pre-historic 6.5:1 C/R and added intercooler, so i think that chances of it knocking to death are minimal, at least as long as you use good gas.

I find both your power/torque, and actually air/fuel ratio perfect! Reving past 6000 isn't doing much good anyway, and your air/fuel is OK under that...

Congratulations, it must be pretty fast car!

P.S. You can also see the effects of heat-soak in the intercooler, between red and blue runs.

P.P.S.
Stock 930 produces max power @ 5500 RPM, so i think they got air/fuel ratio spot-on under that ...not bad for such pervert fuel system...

[catuck]

Must be a fun car!! If you don't mind my asking, how much do they charge to dyno? Where is NE Dyno and Tuning? I would like to have my car checked.

[ChrisBennet]

Now that beepbeep mentions it, look how flat that mixture curve is. Pretty good for 1975 CIS technology!
-Chris

[dean]

Thanks guys. The car is a blast to drive. It is pretty quick. I would like it to be a little richer. But I am not going to spend money (fuel enrichment) on the CIS if I can help it. The dyno runs cost $95 with air/fuel reading. They are in Worcherster MA (can't spell). I mostly did the testing for the air/fuel and for a base line. I am going to go to EFI next winter and I want to know how much just going to EFI makes

[350HP930]

Your numbers could be a lot better if you could fatten up that WOT mix a bit.

14:1 may be a good air fuel ratio for low load conditions, its too low for an air cooled forced induction motor at full output.

If you can bump it down a point or two you will probably be able to get yourself a few extra horses.

[dean]

I did try to fatten it up. The screw only does so much. At idle it is 12 to 1, then the mixture gets leaner when under load.

[350HP930]

To pull off what you need to do using only your CIS you would need to bump your CIS pressure.

This would involve shimming your fuel pressure regulator spring, which is easier said than done.

The only other method would be a pressure switch and a dwell signal generator that you can use to adjust the lambda mix adjustor regulator valve (which is all the andial CIS Fuel Enrichment System is).

If you want to get serious about tuning your setup for a safe maximum power I would recommend the combination of a J&S knock-timing controller and a AIC controller and leaving your pefectly operating CIS system alone.

http://jandssafeguard.com/
http://www.hksusa.com/products/?id=638

[kstylianos]

Blown,

If I understand CIS correctly, richening via the 3mm screw (if that’s where you made your adjustment) will only fatten up A/F at the bottom end. It's not a liner/progressive change throughout the RPM range, WOT or not. These numbers do look promising though as I'm in the process of building a modded 3.0 with CIS.

I think you have the vacuum WUR which is adjustable internally. You can modify the WUR to lower the warm control pressure, which will fatten the A/F mix throughout the range, CIS gauges needed. I did some brief research on this a few weeks ago and will probably go this route (modifying the WUR) if I need to richen the A/F.

Hopefully some CIS experts will chime in as I'm still curious as well......

[350HP930]

Actually, the A/F adjustor screw fattens or leans out the entire curve.

If you want to increase the progression of the A/F curve altered CIS pressures are necessary.

There would be a lot of trial and error and difficult tuning involved which is why I recommend a piggy back supplemental system instead.

The HKS unit I posted a link to allows you to create a supplimental fuel map over a RPM-Manifold Pressure grid.

When it comes to tuning your fuel curves it don't get much better than that.

[kstylianos]

Actually, the A/F adjustor screw fattens or leans out the entire curve.

So, essentially it does increase/lower the warm control pressure? If it does, I understand how it affects the entire range.

I'm still trying to figure CIS out.......

[350HP930]

The a/f adjustor screw effects the control valve to the meter door adjustment.

Since the mechanics and valving are designed to properly meter air and fuel, adjusting this mechanism just changes the overall a/f ratio.

The warm start pressure regulator (and the boost mix controller on 930s adjusts the same pressure circuit) places a hydraulic force on the metering valve that works against the force on the other side from the air metering door.

Therefore the cold start / boost mix regulator reduces the control pressure when warm and boosting so that the air against the meter door has a greater effect on the meter valve, and voilla, a fatter mix.

This pressure circuit is the same one that is tweaked by the closed circuit lambda system to electronically adjust the mix.

In a way CIS is very simple once you realize it is nothing more than a pressurized fuel source, a fuel valve connected to an air metering door and a control pressure source (warmup, boost and lambda regulators) to adjust the air meter door force to fuel rate ratio.