Durametric logging-- please advise
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Just to add a small point of mine own,with 30 years of Big HP cars and dyno experience. Apart from the usual air flow and heat soak issues. Dyno pulls in 5th at 6700 rpms will be well into 170 mph. No Dyno operator I know likes to sit in a car on a Dyno at those speeds. Its just too much and requires big ***** as well. Most Dyno operators I know will only use 3rd and like the wheel speed to under 100 mph. There is just too much inertia if things go wrong and no escape route. Also the chance of wheel bounce is much greater at very high speeds which will lead to high speed wheel spin out. This can be nasty.
Just my little experience.
Frank
Just my little experience.
Frank
Last edited by Frank ( Sunnyside ); Apr 10, 2011 at 01:20 AM.
Manthey would disagree...
Honestly I'm a little confused as to what you're asking.
Are you asking why most tuners tune in 4th gear on chassis dynos? Its quick, relatively cheap, safe and provides a 90% solution to most of the enthusiast crowd as well as pretty sheets to brag to one's buddys about. Does it adequately simulate real world conditions? Maybe, really depends on how the car is used.
Would a 5th gear dyno pull be better? As you said, not really unless you can adequately represent airflow in these conditions. Is a 5th gear pull on the road better? IMO, heck yes! (safety & law considerations aside)
As an example of when this type of dyno tuning (non load bearing) may miss the mark... there have been many that have dyno'd well & been tuned in 4th gear with no apparent issues and then have had the cars fall flat on their face doing actual (non dyno) runs to 200mph (because of the issues I mentioned). If you never run the car this hard, this its probably no big deal as these issues won't surface. Some examples in the link in this post ("technical data on flashes"):
https://www.6speedonline.com/forums/...ml#post2932471
Note: I'm am NOT saying EPL does this, I have beat the p*ss out of their tune (well beyond 4th gear) and the logs look beautiful.
Does that help?
Honestly I'm a little confused as to what you're asking.
Are you asking why most tuners tune in 4th gear on chassis dynos? Its quick, relatively cheap, safe and provides a 90% solution to most of the enthusiast crowd as well as pretty sheets to brag to one's buddys about. Does it adequately simulate real world conditions? Maybe, really depends on how the car is used.
Would a 5th gear dyno pull be better? As you said, not really unless you can adequately represent airflow in these conditions. Is a 5th gear pull on the road better? IMO, heck yes! (safety & law considerations aside)
As an example of when this type of dyno tuning (non load bearing) may miss the mark... there have been many that have dyno'd well & been tuned in 4th gear with no apparent issues and then have had the cars fall flat on their face doing actual (non dyno) runs to 200mph (because of the issues I mentioned). If you never run the car this hard, this its probably no big deal as these issues won't surface. Some examples in the link in this post ("technical data on flashes"):
https://www.6speedonline.com/forums/...ml#post2932471
Note: I'm am NOT saying EPL does this, I have beat the p*ss out of their tune (well beyond 4th gear) and the logs look beautiful.
Does that help?
Just to add a small point of mine own,with 30 years of Big HP cars and dyno experience. Apart from the usual air flow and heat soak issues. Dyno pulls in 5th at 6700 rpms will be well into 170 mph. No Dyno operator I know likes to sit in a car on a Dyno at those speeds. Its just too much and requires big ***** as well. Most Dyno operators I know will only use 3rd and like the wheel speed to under 100 mph. There is just too much inertia if things go wrong and no escape route. Also the chance of wheel bounce is much greater at very high speeds which will lead to high speed wheel spin out. This can be nasty.
Just my little experience.
Frank
Just my little experience.
Frank
I hope that the OP isn't put off by the threadjacking. There is some good stuff here that should help him in interpreting his logs when he gets them. I hope that he'll post them when he has a chance.
Small points to add to the discussion above, with which I am in general agreement... Boost pressure is not a measure of engine load - it's an output of the ecu trying to reach its target load. And the boost pressure you read on your dash is integrated over several seconds to give a smooth readout. In lower gears you pass through the rpm range too fast to get accurate readings of instantaneous boost on the dash.
Jon
Small points to add to the discussion above, with which I am in general agreement... Boost pressure is not a measure of engine load - it's an output of the ecu trying to reach its target load. And the boost pressure you read on your dash is integrated over several seconds to give a smooth readout. In lower gears you pass through the rpm range too fast to get accurate readings of instantaneous boost on the dash.
Jon
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The OP is quite happy to have all the input here. Its one of the reasons I love this group, you guys dont just answer the questions, you go the extra mile. Thanks!!!
I agree with Sunnyside, I've seen a lug nut fly off while on the dyno. There is no where to run when its ricocheting I no longer stand in the bay or go near an operating dyno. I'm especially leery of the lift dynos used at car shows. If a car were to shoot off with wheels spinning over 125mph, things will get bad and quick.
On a side note, the previous owner gave me a receipt for a chip that was installed at Champion Motorsports back in 11/04, but based on the way my car performs, it seems stock, not chipped/flashed.
I know that there was a switch chip or some sort of switchable chip back then, does anyone know how to attempt to adjust it? I spoke to the original owner who told me the guy I bought it from was so scared of the car that he probably had it removed. Anyone in South Fl up to help remove the ecu to see what's in it?
Again, thanks for all the input. I should have logs completed Monday or Tues.
I agree with Sunnyside, I've seen a lug nut fly off while on the dyno. There is no where to run when its ricocheting I no longer stand in the bay or go near an operating dyno. I'm especially leery of the lift dynos used at car shows. If a car were to shoot off with wheels spinning over 125mph, things will get bad and quick.
On a side note, the previous owner gave me a receipt for a chip that was installed at Champion Motorsports back in 11/04, but based on the way my car performs, it seems stock, not chipped/flashed.
I know that there was a switch chip or some sort of switchable chip back then, does anyone know how to attempt to adjust it? I spoke to the original owner who told me the guy I bought it from was so scared of the car that he probably had it removed. Anyone in South Fl up to help remove the ecu to see what's in it?
Again, thanks for all the input. I should have logs completed Monday or Tues.
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Another side note - A 4th gear data-logging pull would take longer than a 3rd gear pull, which allows for more data sampling so you would get finer resolution on how car is behaving.
I will settle on 3rd gear pulls only though, 4th gear is simply too fast for comfort on public roads.
I will settle on 3rd gear pulls only though, 4th gear is simply too fast for comfort on public roads.
Hey I agree that 4th gear can be a bit much for the public ways,,We do not want to endanger anyone,,,,But I just wanted to know which would be more helpful for tuning,3rd or 4th.....Some of us are blessed with long stretches of highyway with out traffic or LOOK for them to let are cars unwind....lol...I am suprised the tuners have not gave some advice to us on this topic??
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