MUSTANG VS. DYNOJET HP COMPARISON

[dj10]

I am the poster child for getting screwy results from dynos. I had a dyno operator swear I was running 18:1 air fuel. As Joe told me at the time, I'd have had holes in the piston if that were the case. What actually happened was the guy had a bad sniffer.

Find a good solid dyno that returns semi-repeatable results and stick with it. Dyno shopping just leads to trouble.

I've seen anywhere from 130 to 165 whp on my car. 160 has been repeatedable on one particular dyno and seems to be correct. Same with torque. Anywhere from 180 to 205.

Look for the repeatable stuff and work with THAT guy. [/b]

What actually happened was the guy had a bad sniffer.



If your refering to the a/f sniffer they stick in the tail pipe, I learned the hard way they are not they way to go. My engine builder will not accept any numbers from them. He uses the O2 port just behing the header with a broadband O2 on his dyno.

[C. Ludwig]

What actually happened was the guy had a bad sniffer.



If your refering to the a/f sniffer they stick in the tail pipe, I learned the hard way they are not they way to go. My engine builder will not accept any numbers from them. He uses the O2 port just behing the header with a broadband O2 on his dyno.
[/b]

Wives tale.

[dj10]

Wives tale.
[/b]

Chris, I certaintly won't argue with you! But honestly back to back there was a big difference between the two on my car. The tailpipe sniffer was reading much leaner than the broadband O2 sensor. Could this have been the operator? One was on a dyno jet the other was on my engine builders Mustang.

[JeffYoung]

Dan, exhaust leak maybe? Or I guess that would richen things up?

[Eagle7]

I'm sure it's dependent on a lot of factors - operator, tailpipe arrangement, sniffer arrangement, etc. The sniffer fell off my car during one pull. I don't trust them.

[dj10]

Dan, exhaust leak maybe? Or I guess that would richen things up? [/b]

Jeff, if I would have had a exhaust on the dyno jet it would have been leaking on the Mustang too. The exhaust was not leaking.



Marty, your right there may be other factors and I'm not nearly technical enough to tell Chris or Chuck their business . I guess it comes down to how and who reads it. What the hell do I know, I'm only the driver.

[C. Ludwig]

Theoretically there is no difference in what the sensor will see at the tailpipe versus the exhaust port as far as a/f ratio is concerned. There are factors that influence what that sensor sees. An exhaust leak is the big one and if a cat is in place that will obviously skew the results greatly. Exhaust leaks will generally show up as a leaner than actual reading. The sensor has to be in the tailpipe and not hanging half way out. And the sensor needs to be in good condition. Seems like everyone is using the Bosch sensors now and they are notorious for short life spans when they're exposed to leaded race fuel. They'll begin responding slowly and eventually default to a lean reading. If you are suspicious of the readings you are getting that Bosch sensor is the first place to look. For those of you that want to run a wideband in the car full time and run leaded fuel spend the extra money on an NTK sensor and the hardware to run it.

Again, in a theoretical sense, where using a tailpipe mounted sensor becomes an issue is in the delay of the reading and how that reading is logged versus actual engine RPM. It's possible to have a lean condition at 2500 rpm but depending on how quickly the engine is accelerating, exhaust velocity, exhaust length, etc the hardware might be seeing that lean condition at 3000 rpm and logging it as such.

It also sounds like there is some confusion about the hardware that is used for each location. The tailpipe "sniffers" should be the same hardware that would otherwise be installed closer to the exhaust port. Just with the sensor installed in the piece that bolts to the tailpipe or held up by a floor stand. For the purpose of this arguement there is no difference. A wideband is a wideband.

I've done several sessions at Automotion using my wideband installed in the header or downpipe and compared my results to their setup simultaneously installed in the tailpipe and havn't noted anything outside of an acceptable "noise" range. A ratio difference of around 2/10. Your results may vary. And I can see how it would be hard to trust someone until you've done multiple sessions with them and proven out their methods and equipment.

One of the other local dynos is notorious for giving poor results from failed sensors and problematic inductive rev pickups.