Dyno'd it....AF Ratio Problem...

[DamnYankee]

Well, they got through a partial run on the Dyno and said they weren't going to run the RPM's higher due to the Air to Fuel ratio. So I'm waiting to hear from Allen so I can get 'er fixed!

Anyway, at 4,000 RPM's it turned out 229RWHP and 272ft-lbs torque...

Not sure how that rates, I'm about to read some old posts, but that's where I stand at the moment...

[RedHeartbeat]

I dyno'd there also. I think their machine is messed up. They put a sniffer behind the cats and read off the fumes coming behind a converter. I don't believe their readings are correct. I could have warned you if I had known you were coming up this way to have it done.

Also, do you have a single exhaust pipe with dual outlets?

[DamnYankee]

<div class='quotetop'>QUOTE(RedHeartbeat &#064; Jun 26 2006, 04&#58;21 PM) [snapback]56341[/snapback]</div>

I dyno&#39;d there also. I think their machine is messed up. They put a sniffer behind the cats and read off the fumes coming behind a converter. I don&#39;t believe their readings are correct. I could have warned you if I had known you were coming up this way to have it done.

Also, do you have a single exhaust pipe with dual outlets?
[/b]

Hmmm...who else in the area does them?

I think I need to change my sig...my exhaust is a single running into the muffler and dual out. Not the same as cat-back duals I guess...

[RedHeartbeat]

The whole purpose of a cat is to change the emissions and destroy unburned fuels. The sniffer is designed to read unburned fuels.

[DamnYankee]

<div class='quotetop'>QUOTE(RedHeartbeat &#064; Jun 26 2006, 04&#58;38 PM) [snapback]56344[/snapback]</div>

The whole purpose of a cat is to change the emissions and destroy unburned fuels. The sniffer is designed to read unburned fuels.
[/b]

Sorry - I didn&#39;t mean it doesn&#39;t have cats, it does. I meant it&#39;s not really a "cat-back duals" setup. After the two cats it&#39;s condensed into a single pipe, then into the muffler with duals out of the muffler.

[DamnYankee]

So until I hear from Allen...

When he&#39;s tuning it, does the AF ratio not show on the laptop? Just trying to understand if he can fix it, how it was missed in the first place? (translation: he&#39;s too thorough to miss something that important)...

[RedHeartbeat]

Honestly, I don&#39;t think he missed a thing. What the readout is showing you is that your cats are working properly. Allen tunes using the factory O2 sensors mounted and reading prior to the cats. The cats heat up and burn any unburned fuels that came through the exhaust. When you compare readings before the cat and after the cats you get different readings. To properly measure the A/F you have to do it before a cat, not after.

[DamnYankee]

<div class='quotetop'>QUOTE(RedHeartbeat &#064; Jun 26 2006, 06&#58;08 PM) [snapback]56350[/snapback]</div>

Honestly, I don&#39;t think he missed a thing. What the readout is showing you is that your cats are working properly. Allen tunes using the factory O2 sensors mounted and reading prior to the cats. The cats heat up and burn any unburned fuels that came through the exhaust. When you compare readings before the cat and after the cats you get different readings. To properly measure the A/F you have to do it before a cat, not after.
[/b]

OK, my first thought is if someone buys a 40K dollar Dyno (or whatever they cost), surely they know how to use it right?

And yeah, I can&#39;t Allen missing anything, he&#39;s too thorough.

So does that mean the ratio they were showing was correct and they should have finished the runs? Or is the ration after the cats supposed to be closer to 13?

I&#39;m confused as to where this went wrong, IF it went wrong, or if they should have finished the runs.

[RedHeartbeat]

Here is my thought about why their readings are wrong.....

1.) They measure the A/F readings at the tail pipe
2.) They are only measured one side of a split pipe system
3.) A/F readings on the PCM are read before the cat
4.) RPM measures after the cats
5.) Cats are designed to alter the emissions levels
6.) the tailpipe sniffer they use is not designed for a catted vehicle

I spent an entire Saturday at one of their dyno days and saw about 50% of the vehicles that went across their dyno read lean. I don&#39;t have the stats as to which ones had cats or not but I find it hard to believe that 50% of vehicles on the road are running lean at WOT. I was going to call Lydia and ask her if they somehow compensate for high efficiency cats or not. I would bet good money that they do not.

I would suggest you buy an 02 bung and have it welded in before the cat so that they can get their readings there instead of in the tailpipe.

[DamnYankee]

Anyone else in the Metroplex that&#39;s reliable?