Hypothetical Dyno Question

[rfoll]

How far would you need to drive to get to a chassis dyno set up that could handle the amount of HP you think your making?

If I remember correctly, 0.5" of barometer is a large chunk of power gained or lost.

[Stan Weiss]

How far would you need to drive to get to a chassis dyno set up that could handle the amount of HP you think your making?

If I remember correctly, 0.5" of barometer is a large chunk of power gained or lost.

SAE J607 @ temp 60 - 0% rh

30.24 bp - dts 0.98942 - ford 0.98732

29.55 bp - dts 1.01252- ford 1.01504

Stan

FORD_pages-62-63.pdf

[Zmechanic]

I'd be worried about the load cell getting abused if it looks in rough shape. Nothing can ruin the calibration and linearity of a load cell quicker than heavily overloading it (it's designed to stand some amount of overload, but still).

[F-BIRD'88]

MB there is a internet site that can convert between the station pressure and corrected pressure
for you . You can also find historic weather data on the web. You can also triangle the data from a few
local weather stations. Many are checked certified daily and go "offline" of that data system if they do not check out, until fixed. I like to look at and note both the corrected dyno data and the uncorrected dyno data from a dyno test.

[RevTheory]

Things to look at on a dyno.

1. Is the carb getting fresh unpolluted air?
2. Is the exhaust free flowing and sized adequately?
3. Is it measuring torque and rpm correctly?
4. Is it correcting for conditions correctly?

Doesn't matter what the dyno looks like or what the room looks like if these things are done correctly. Each one can be individually looked at to convince yourself it is or isn't correct.

Just because a dyno looks nice, clean well organized doesn't mean its right either. Lot of incorrect dynos out there being used every day.

Rick

Good point, Rick. I'll try not to be a dyno snob, lol. I spoke with Big Joe years ago and he said he was done with the whole $30,000 dyno cell thing.

[DaveMcLain]

MB there is a internet site that can convert between the station pressure and corrected pressure
for you . You can also find historic weather data on the web. You can also triangle the data from a few
local weather stations. Many are checked certified daily and go "offline" of that data system if they do not check out, until fixed. I like to look at and note both the corrected dyno data and the uncorrected dyno data from a dyno test.

Uncorrecting a corrected barometer reading from a local weather data source is easy enough to do. Back a long time ago I used data from a local weather barometer and corrected for my own altitude which is 1000ft. I just had to subtract 1.07 inches Hg. Later I had my own weather station with an uncorrected barometer but now I have one that's connected to the dyno. They always read very close to the same, no big deal.

[andyf]

Years ago the correction factor that someone used on a dyno was just an accepted fact but now it only takes a few minutes of internet searching to see if the shop used the right correction factor. Type in the location and the date and you should be able to find the weather records from an airport or a weather underground location that is close to the shop. I think this probably cuts down on some of the "creative" correction factors that people might have taken in the past. Not to mention the hand held weather stations and even weather features built into watches and phones and stuff like that. A dyno operator would need big balls or else be a little dumb to try and peddle fake correction factors these days.

[Frankshaft]

Years ago the correction factor that someone used on a dyno was just an accepted fact but now it only takes a few minutes of internet searching to see if the shop used the right correction factor. Type in the location and the date and you should be able to find the weather records from an airport or a weather underground location that is close to the shop. I think this probably cuts down on some of the "creative" correction factors that people might have taken in the past. Not to mention the hand held weather stations and even weather features built into watches and phones and stuff like that. A dyno operator would need big balls or else be a little dumb to try and peddle fake correction factors these days.

But they still do it. Most guys don't Care. If the sheet says so, that's what it is. How does an engine go from 1175hp, to 1238 in 1 pull, only change 30 degrees cooler water temperature. Bsfc' go from mid 4's to mid 3's like magic. Not only did it pick up 63 hp, but it used way less fuel to boot. From a 30 degree water temp change. Ok, you betcha. Owner believes it, because it's on the paper

Actually, I should say, it made way more power with the same amount of fuel.

[F-BIRD'88]

You can also check the time of day on the dyno sheet and compare weather data to the hour.
Watch on days with a Climbing barometer during the day.

I fact checked one here recently and it turned out that that day and location had just that.. His weather data was accurate in the morning but by 6pm time of dyno test the barometer had in fact climbed a good bit... Thus "happy" corrected dyno numbers.

details matter

[DaveMcLain]

You can also check the time of day on the dyno sheet and compare weather data to the hour.
Watch on days with a Climbing barometer during the day.

I fact checked one here recently and it turned out that that day and location had just that.. His weather data was accurate in the morning but by 6pm time of dyno test the barometer had in fact climbed a good bit... Thus "happy" corrected dyno numbers.

details matter

That's why its nice to have a dyno with a built in weather station so that you get up to the minute weather data before each test pull. With that said I don't like testing on days when the weather is moving around a lot.

[randy331]

Years ago the correction factor that someone used on a dyno was just an accepted fact but now it only takes a few minutes of internet searching to see if the shop used the right correction factor. Type in the location and the date and you should be able to find the weather records from an airport or a weather underground location that is close to the shop. I think this probably cuts down on some of the "creative" correction factors that people might have taken in the past. Not to mention the hand held weather stations and even weather features built into watches and phones and stuff like that. A dyno operator would need big balls or else be a little dumb to try and peddle fake correction factors these days.

But without enough air through the dyno room, it could still be off.

Was at one place that was showing 90+ deg temps during a pull in January. It was probably 20* out that day. It would climb 10* + during a pull.

Randy

[ptuomov]

How do you do the temperature correction on a knock limited engine?

[dorset]

I tune my LSR race bike on a Superflow chassis dyno....No O2 sensor hooked up, overhead garage door open, let it rip.I just tune for best power.I do not normally tune at the track..The competition spends time analyzing the dyno readouts, fuel air mixtures etc. At the track they are changing exhaust, jets, timing etc.....My bike literally comes off the trailer, I put in fresh race gas, warm up the engine and hand it to the rider..And set a new speed record...

yes.

this is why you continue to be so annoying.

[MadBill]