I got my car dynoed today, and with the wide band o2, it showed my A/F in the 16's all across the pull. I think it topped out at 16.7! I also had around 4 degrees of knock!

I made 277 rwhp and 321 rwtq @ 4900 rpm then fell sharply after that.

How much HP do you think I can lost from the knock and A/F?

I guess we'll see if the problem gets resolved.

All mods are in my sig.

 

Here's a picture of my dyno graph.

http://www.txstreetcars.com/street/m...view_photo.php

 

Does anyone have any ideas of what might be going on by looking at my dyno graph?

 

Your graph looks similar to my friends before his opti took a dump on him...you may also wanna check your fuel filter its very easy to check and I've seen it work miracles on cars before...

 

You're the second person to tell me that it looks like opti problems.

I think the fuel filter is okay, it's pretty new.

Thanks for your help.

 

You're obviously having a 'lack-of-fuel issue', whether it's mechanically or PCM induced.

-Dave C. '97 Z28

 

Wow, the opti gets blamed for a lot of stuff (much of it legitimate) but in this case I'm at a loss to come up with a reason the opti would create a lean condition.

Obviously you'd want to check fuel filter, hopefully something easy like that. If it persisted after the filter then I'd get a fuel pressure guage on there for a run and see if your fuel pressure is dropping (fuel pump failing / poor voltage / etc. perhaps). If that checks out then I'd check the PCM tune, maybe someone mis-entered in the PE / AFR tables but I highly highly doubt anyone in their right mind would be entering anything anywhere near the 16s a/f at WOT.

Good luck figuring it out, hopefully it proves to be simple.

 

That is the second highest a/f ratio ive seen on a dyno chart. I in person saw a blown lt1 run 18:1 on the dyno (talk about no fuel!).

What was mentioned previously about fuel is where i would start.

 

I don't think the OPTI could create a lean condition but the extreme jumpiness of the graph is usually a sign of a bad opti. I've seen 250+ cars dynoed and generally jumpiness is an ignition problem...as for running lean, thats why I mentioned checking the filter because its EASY and cheap...if thats been done could be a pump or some injectors going down, a leak in the fuel rail, could be a number of different things...I guess I should have been more clear in my first post...

Lean = Fuel
Jumpiness = Can indicate ignition problems

 

Oh and dave brings up a good point...it could be pcm induced...I've seen computers do some very strange things to cars from running lean to rich or not running more than 10 seconds....could be something on that end as well....

 

Ahh, I wasnt looking at the HP part of it. I think the above poster talking about the opti was referring to the peak occuring at 5k rpm and the really erratic drop after that.

I'd say get the fuel situation fixed first then if you are still getting really choppy above 5k rpm then it might be something electrical (coil / opti etc.).

When running well you shouldn't see that large choppy drop above 5k imo.

Sorry for being confused above.

 

Thats exactly why I mentioned the opti...peak power should occur about 5200 or so on a stock LT1 if you have bolt ons it'll shift peak power slightly higher...I wasn't really even pay attention to that part of it...once I pulled it up and noticed how choppy it was, that looked like opti...the fuel problems well we've covered those already...

 

I really appreciate all the help!

Please keep it coming.

 

wow
I think your losing a good 25-35 HP on my guess.
I think without 4deg KR and proper AF you should be over 300 easy. Plus you should be able to take the motor higher and gain that hp too.
I would do as the others say.

 

So, I guess it looks like it is going to cost me over $1,000 to get my problems worked out once again.

Do you guys think that a bad fuel pump can really cause my A/F to go that crazy?