Hey everyone,
Today I brought my car in to school today to dyno it and possibly swap the injectors and computer back to stock to see if thats whats causing my rich condition, but I didn't get to swap them. Heres the whole story:

In June, at the Midwest F-Body Meet, I had my car dynoed and it only put out 205.9 HP and 231.9 TQ. It was running about 10.4:1 at WOT, so I knew that wasn't helping the power. I recently checked the plugs and realized I had them gapped incorrectly. They were at .045" instead of .035" (I must have misread ). Anyway, I corrected them and the car ran much smoother. I brought the car to school today to dyno it. The first run gave me 180.48 HM and 179.54 TQ, but that was incorrect. The A/F was at about 15:1 til 4750 RPM, then began to lean out until it was off the charts, then came back down to 14.5:1 at 5350 RPM. There is no way it is running lean with the HC readings it had on the 5-Gas (240 ppm at idle, 1010 at 2500) The next run it put down 202.31 HP and 226.83 TQ, which is still disappointing. After pulling the car off, I noticed a decent sized puddle of oil. We found the distributor had come loose and began to leak oil. After resetting the timing, we ran the car two more times. First it put out 212.29 HP and 240.22 TQ, and the next run 206.80 HP with 243.72 TQ. The car is still way too rich, dropping to 10.5:1 at 4650 RPM and below 12:1 from 3900 on.

Here is my setup:
K&N Airfilters
Holley 52MM throttle body
LT1 Intake
24lb SVO injectors with a chip burned for them
Hooker 2055 headers, ceramic coated
3" Ravin catback exhaust
180* thermostat and fan switch.

Fuel pressure for all the runs was 40PSI at idle. After the last run, I dropped it down to 37 PSI and it lowered my HC's some, but not much. We didn't have time to dyno it again.

Any ideas on what can be causing my rich condition? Since my headers are ceramic coated, should I consider getting a heated O2 Sensor to make sure it reaches its operating temperature? Also, I did not have the chip burned, it came with the intake for those injectors. If the computer is looking for a higher operating temperature than my fan switch and thermostat, wouldn't it keep adding fuel to try and get it hotter? Perhaps I should get another chip burned for the 24lb injectors, aftermarket fan switch and lower thermostat? Or would I be better off putting the stock injectors, fan switch and thermostat back in? Thats just what I was thinking, but I'm sure you guys know more than I do. ANy help is appreciated. Thanks for the read.

Andy

 

I'm not a fuel injection expert, so i don't know how much help i can be,

But, a heated O2 sensor won't do anything for you. At WOT the ECM is in open loop, and while in open loop, the ECM does not take readings from the O2 sensor to determine fuel mixture or timing.

So your oxygen senson isn't the culprit

Leaning your fuel curve out will definatly help some.

I don't know how to tell you this, but your not too far off from your engines peak perfromance.

LT1's only dyno around 240 at the wheels stock(intake and headers)

so i wouldn't expect more than about 220-230hp

 

I forgot the ECU ignores the O2 at WOT

My engine isn't an LT1, Its an L98 with the LT1 intake manifold. I know I'm close to peak for it, but I still would like to see what it runs at like 12:1 or so.

Thank you for the input

 

What heads & cam is this?

Now I don't feel so bad about my weenie little 305.... it only does 237 HP & 266 ft-lbs on the chassis dyno. Stock carb and all the computer stuff, intact.

 

The heads and cam are whatever came stock on a 89 L98.

 

I would say the culprit lies in the chip. Sure changes may have been made for the injectors but not for the intake, and headers. This is a common problem for any modded TBI/TPI set-up. Fueling and spark chances can not be done through mail order. Chip work is the key when significant modding is done. Do you still have your stock injectors and PROM? I would start by putting both of those back in.

 

Even if you had a chip for 24 pph injectors, the stock power enrichment air fuel ratio is usually sub 12:1 (to shut the cat down and be on the rich side of best torque to allow for production tolerances and wear and tear). The injectors are 24 pph when the fuel pressure is set at 43.5 with the regulator's vacuum reference tube disconnected (don't run the engine long this way, just set the pressure this way). When the pressure is higher, the flowrate is higher (square root of the pressure ratios times the reference pressure). So, another chip burn with a little less PE adder is going to help, and the injector constant should reflect the actual flow rate of the injectors as run.
HC's are NOT a good measure of air fuel ratio - CO IS a very good measure of air fuel ratio. If your 5 gas is reading CO in percent, aim for around 5%, or a little more. If you have a wideband, or are using the 5 gas to calculate air/fuel ratio, shoot for around 12.3 to 12.8 throughout all RPMs at WOT. Power output isn't very sensitive to air fuel ratio in this region, and is *generally* max in this region (i.e. power won't really spike at a certain A/F).

 

Sounds to me like your ignition timing is likely to be WAY retarded from optimum.

Check it during a pull.

It should reach somewhere near 35° at full load (WOT) and 3500 RPM. If it doesn't, adjust the "static" timing (what you adjust by twiddling the distributor) until it does. Then see what it gives.

That will tell you if that's a problem area. If it is, you probably need it re-programmed as part of your chip work.

Leaving it loose guarantees that it will retard itself; after all, the rotation of the shaft, tends to turn the body in that direction.

With stock heads & cam, don't expect miracles; but it should be able to do more torque especially; you should see somewhere around 300-320 ft-lbs at the wheels.

 

Thanks guys, I appreciate all the help.

Shifty- I do still have the stock injecotors and chip, so maybe I will try putting those back in or getting another chip burned for the whole setup.

RednGold- The a/f was calculated using the sniffer on the dyno. But prior to running it on the dyno, we ran a 5-Gas on it. I do not recall the CO numbers off the top of my head, but I can get them off the sheet I have at school.

RB- Unfortunately I won't be able to bring it back for more dyno time, so I won't be able to check timing during a pull. The car is about done for this year anyway, maybe I'll bring it somewhere for some tuning on a dyno next year. But it has a knock, so I'm thinking about starting a new engine anyway.

Thanks again everyone