How Chassis Dynos work

[Tom @ Fast Forward]

I just looked at your graph again and drew they typical red line for what it should look like. To me it still looks like either you are running out of ignition or the exhaust is restricted. The line shows you should be around 225 at 7000 RPM. The way it simply rolls over is indicative of ignition, plugged flow path or fuel. Your other graph shows that you have 11.4 which is plenty of fuel.

As you can see, you are drawing a pretty good line up to about 5700 RPM and then over it goes.

[Scaytale]

Hello Tom, saw your message about ignition timing, and COPs with the FFS Cards. I have sent FAB9 a message and hopefully this will make the issue go away, I have noticed some starting and idle hesitation over the last month or so but I didn't think of the relationship to the COPs.
Other than that a test without the CAT will have to wait, but it will happen.

Thanks for your help

[Scaytale]

This is what I got from Bryan, at FAB9

Hi Jon,

These FFS cards have been hit or miss. We have a couple of trial harnesses out there for testing. One of them has failed and the other customer is waiting for installation. As soon as I have confirmed functionality of the harness I will be offering it to the small handful of customers that have run into this issue. Can you please send an email with your information to [email protected]. I'll add to you the list.

Cheers,
Bryan

So I am on the list, if you have COPs from FAB9 and you are having any issues taht might be related to ignition and you are running the FFS cards, you might want to check it out and pursue a replacement harness.

[jportwood]

Hello Again :-)

OK so I did get to go to the other dyno. I think I like the way the drum dyno better, it give a smoother output, likely because the drum is spun up through the gears until you get to 4th then between 1500-2000 WOT all the way up.

Still no real answer about why the power seems lower than it should be, even though this dyno showed about 200 HP @ 6700 probably get to 220 HP @ 7200, but the operator wouldn't get there. About 170 TQ at 5050 RPM but pretty flat curve. Still doesn't give any indication of a problem other than lower than expected HP/TQ numbers. The only thing left is take the cat out of the system. That will likely have to wait a while.

Tom Suggested that I post these two pix and see if anyone has an idea, comment, or whatever. I plan to Lower G/B to help the slight rise in AFR between 4500 and 6000 RPM.
[ATTACH=CONFIG]1517[/ATTACH][ATTACH=CONFIG]1518[/ATTACH]
Any Ideas are appreciated.

So you paid to have your car dynoed and dude didn't take it up to the redline/rev limiter and your questioning your numbers? I don't get it.

[Scaytale]

So you paid to have your car dynoed and dude didn't take it up to the redline/rev limiter and your questioning your numbers? I don't get it.

I guess you don’t, of course it gets convoluted if you don’t follow it all. First, I have never tried to assign blame to anyone but me, and Tom has been exceptionally helpful, just to get that out of the way up front.
My initial results were 187 HP and 154 TQ, I thought this a little low and asked about it, to see where I may have done something wrong or what the issue might be, there was lots of discussion, the operator in this case took the car to 7000 RPM, and the dyno sheets are available earlier in this thread. I also have higher than expected boost, this was thought to be a bad CAT, I had it replaced, still higher than expected, so we are trying to determine what could case those two issues. One suggestion was a difference in Dyno’s so I found one similar to what Tom is using and had the car dyno’ed again in the DynoJet. This netted about 200 HP and 168 TQ and he took the car to about 6700 RPM, I didn’t notice the lower RPM until later and I discussed that with Tom, as well as sending him the files from the dynoJet and the AEM data for those runs, additionally he has the dyno charts from the earlier run with the FFS, and a comparison of a run on that same dyno without the FFS. Please See Toms comment below after reviewing the data.

I just looked at your graph again and drew they typical red line for what it should look like. To me it still looks like either you are running out of ignition or the exhaust is restricted. The line shows you should be around 225 at 7000 RPM. The way it simply rolls over is indicative of ignition, plugged flow path or fuel. Your other graph shows that you have 11.4 which is plenty of fuel.
As you can see, you are drawing a pretty good line up to about 5700 RPM and then over it goes.

After this Tom and I talked about my Ignition and he pointed out that the Fab9 COPs may need a new harness to work well with the FFS Cards, so I contacted them and I am also having some starting issue and idle issues until it warms up but I didn’t think it was related to the COPS, this is not my daily driver. We still may have an exhaust restriction as discussed above, after that I’m not sure what the issue may be, it could be a difference in Dyno’s it could be a high end ignition issue it could be excessive back pressure (since the boost is about 2-3 PSI higher than expected.
Like Tom, I expected something closer to 225 HP and 12-13 PSI boost. Just trying to work the kinks out and see if anyone had any other suggestion, it’s more of an exchange of information than a complaint.

[jportwood]

With all due respect dyno dude robbed you on a full pull. I'm thinking this is your first dyno rodeo so it's not your fault. I would have to question the operators experience being that it's common knowledge that most tachs are behind true engine RPM. This is why you pull to the limiter. Don't take this as anything other than what should have and does happen with the right operator.