Running rich....help me analyze my dyno graph

[SolidState]

hey guys. below is a scan of the second run on saturday.



It was an overcast day at about 15 degree celcius. The car was at proper operating temp according to the dash guage. Shell 91 octane fuel.

You will notice that my curves are exactly as they should be, and I guess they aren't too far off of an unmodded ATX SHO with 155k should be. But my AF after the cats are wayyyy outta wack. This car is running far too rich.

Maintenance done the car:

Plugs
Wires
O2s
TPS
CPS
Waterpump
newish fuel filter
clean K&N
lower milage y-pipe

We tried two different MAFs. The second maf was a one off 73mm and it leaned it out a little, but was still running at about 12:1. The curve on the AF was the same, just a little leaner.

The intake on the car is fairly caked up. I have a new one that I am cleaning, painting and applying new gaskets to.

I will note that the car runs noticabley better in rainy weather with denser air.

Any input is much appreciated. I am hoping to pick a couple extra wheel HP by setting the air/fuel ratio correctly.

TIA

 

[sdpatt]

The dyno run started high, but I saw no evidence that the secondaries are opening at 3,950 rpm. If that air:fuel ratio measuerment is accurate (a 73mm not running lean?) then your engine is definitely running rich. So rich that you should be seeing the CHECK ENGINE light and the telltale codes. Try the OEM MAF.

Edit: Comparing the numbers on your graph to those on my last dyno run revealed that the power and torque at the 4,000 rpm level are within 5 hp and 5 lb-ft: very similar. Above that level, your torque continues to drop rather than rise to a peak in the 4,500-5,000 range. The slope of the power curve shows there to be a possible spark advance limitation, exhaust restriction or, with that rich mixture, a misreading MAF, ACT or BAP sensor. The curve is smooth, but not increasing at the rate of a healthy stock SHO engine.

<small>[ October 23, 2003, 10:12 AM: Message edited by: sdpatt ]</small>

 

[SolidState]

I have run two OEM MAFs and a custom one off 73mm MAF. PM me for details

I heard the secondaries open, so I know they are opening...no CEL either. I was thinking that one of the temp sending units is bad...

In all honesty though, there isn't near the bump at 3950 there used to be.

I think I am going to get that other intake on the go and put it on the car.

<small>[ October 23, 2003, 09:25 AM: Message edited by: SolidState ]</small>

 

[SolidState]

sdpatt:
The dyno run started high, but I saw no evidence that the secondaries are opening at 3,950 rpm. If that air:fuel ratio measuerment is accurate (a 73mm not running lean?) then your engine is definitely running rich. So rich that you should be seeing the CHECK ENGINE light and the telltale codes. Try the OEM MAF.

Edit: Comparing the numbers on your graph to those on my last dyno run revealed that the power and torque at the 4,000 rpm level are within 5 hp and 5 lb-ft: very similar. Above that level, your torque continues to drop rather than rise to a peak in the 4,500-5,000 range. The slope of the power curve shows there to be a possible spark advance limitation, exhaust restriction or, with that rich mixture, a misreading MAF, ACT or BAP sensor. The curve is smooth, but not increasing at the rate of a healthy stock SHO engine.

I follow. The y-pipe is is clear. Kepp in mind that this is an ATX, so the power peaks at different rpms than an MTX.

I am going to change the ACT and DPFE. The ATX does not have an BAP. I am also going to change both temp sending units.

 

[projectSHO89]

Save your money on the DPFE, it won't affect this.

Steve

 

[sho 'nuff]

Anyone want to try to make an analysis of my dyno?

This dyno was done before I got the Pro-M MAF or VAKS. At the time I was running a RActive heatshield filter. I've since gone back to the stock airbox with the 75mm MAF.

 

[Ishodu]

sho 'nuff:
Anyone want to try to make an analysis of my dyno?

This dyno was done before I got the Pro-M MAF or VAKS. At the time I was running a RActive heatshield filter. I've since gone back to the stock airbox with the 75mm MAF.

It looks like you have a miss fire of something? Bad plugs or wires? Fuel pump? You are sure lacking power in the high end. Did you have AF reading?

 

[SolidState]

my first run of the day was 168.9hp and 178ft-lb of torque..

I have a spare DPFE sensor on the other intake.