How come you get people that dyno at one number but then say it's actually another number? This is something that has boggled my mind for quite some time. Dyno is a dyno is a dyno right? How come you get guys that say this is the blah blah blah dyno number and this is the blah blah dyno number? I just don't understand the differences I guess. Further explanation?
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4 Cams...32 Valves...5 Liters...This Could Get Fun!
I has to do with the way the dyno gets the hp number. Each of them have a different set up which ends up giving a different reading for the same car. So some dynos maybe "set up" to give you a higher hp number.
So what you are saying is that there is no true way to properly gauge wheel horsepower.
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4 Cams...32 Valves...5 Liters...This Could Get Fun!
i always use dyno jet #s cause thats what i always dynoed on before ohio, and i use the higher # cause im a ricer...lol
R.I.P. Brian Klocke, you will never be forgotten
YES there is
if everyone gets on the same dyno that same day, then there are no arguements! Thats why a bunch of us got together in Wisconsion @ Great Lakes Dragway last year. I was closing in on the 14.00 sec all motor record, and we let er loose and set both ends of the all motor record that day, that 14.00 record holder went best of 14.46 and i went best 13.67 @ 100mph (Same idea different story)
Again at the GM Tuner Bash 2008 there was a dyno there, yes it was different than prob your local guy has but you were getting numbers comparison to others thats all that matters on that day
Hope i explained that in a way you could understand
-Ben
That's why trap speeds matter
The dyno is a tuning tool, it could measure different based on different conditions or just a different machine. But no matter how it reads it can tell you if the changes you are making are good or bad when done right after one another. Or as Brandon said measuring the same cars on the same dyno on the same day would give a good comparison.
12.770 @ 111.99 Intercooled Eaton M62
Boosted2point4 wrote:and i use the higher # cause im a ricer...lol
Heavens no! Not from the great Fetter. lol
Thanks guys. So now I think I get it a little better. Trap speeds and caculations are more accurate than a dyno.
One thing though, airflow is different on a dyno vs. driving down the road, so tuning specifically on a dyno shouldn't be the best thing, track runs would produce the most accurate tune. Correct?
I'm just trying to understand the "science" behind everything that I've done to my car to this point to try and understand where I can make improvements to make more power and ultimately reach my goal of mid 400's for whp.
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4 Cams...32 Valves...5 Liters...This Could Get Fun!
Well technically trap speeds are better measure for hp but your adding a dynamic variable of the driver into the equation
One thing we must all remember is horsepower is calculation of the ability to do work...IT IS UNMEASUREABLE.
It can only be calculated which also means NO DYNO can EVER physically measure and give a 100% accurate horsepower readout. Period.
Torque however is measureable and is used to equate to horsepower via speed.
The sign of a good true to life dyno run and result is at 5500rpm torque and Horsepower bands should cross. This is where the fact that skunk made significantly more torque than HP bothers me. I blame it on them running his car up in 3rd gear. 4th would have brought those numbers closer and I would bet that torque and Horsepower cross early of the 5500rpm line on his dyno sheet because of it.
Skunk, personally I would throw that @!#$ out and find a better show and make a pull in 4th. You might get some more orthodox and true to life numbers. Torque multiplication through the trans is a big problem with your current 3rd gear numbers.
Buildin' n' Boostin for 08' - Alex Richards
Alex Richards wrote: Well technically trap speeds are better measure for hp but your adding a dynamic variable of the driver into the equation
One thing we must all remember is horsepower is calculation of the ability to do work...IT IS UNMEASUREABLE.
It can only be calculated which also means NO DYNO can EVER physically measure and give a 100% accurate horsepower readout. Period.
Torque however is measureable and is used to equate to horsepower via speed.
The sign of a good true to life dyno run and result is at 5500rpm torque and Horsepower bands should cross. This is where the fact that skunk made significantly more torque than HP bothers me. I blame it on them running his car up in 3rd gear. 4th would have brought those numbers closer and I would bet that torque and Horsepower cross early of the 5500rpm line on his dyno sheet because of it.
Skunk, personally I would throw that @!#$ out and find a better show and make a pull in 4th. You might get some more orthodox and true to life numbers. Torque multiplication through the trans is a big problem with your current 3rd gear numbers.
- Trap speeds are usually decently accurate no matter how good or bad the driver is. ETs can change alot, but trap speeds usually don't change by much.
- Horsepower can easily be measured. If you move "X" amount of weight, a distance of "Y", in "Z" amount of time then you know how much work was done and hence the horsepower. Yes you are calculating the horsepower, but you are also calculating torque in the same way since you need to know force (i.e. Lbs) and distance (i.e. Feet) to get a torque #.
Time can be measured, force can be measured, distance can be measure. By Alex Richards statement, HP is calculated and therefore un-measureable... but torque is still measurable. Torque is also a calculation... of measured force and measured distance. Horsepower is the same calculation with the insertion of measured time. So neither of them is truly measurable, but for ease of communication, we say them as measured #s.
- Intertia dynos, like a typical dynojet, actually measure horsepower (and only horsepower) and calculate from that the torque if engine rpm is measured. Brake dynos, like a dynapack, measure torque and time and calculate horsepower from that.
-the gear a dyno run is done in has very little effect on the outputed #s since the TWO factors that change do to a gear change are TIME and TORQUE (or power) and the changes are opposite of each other and therefore cancel each other out. Gear changes do have a small effect on the reading due to drivetrain inertia, but the difference is small enough to be within the percentage of error of the dyno anyway.
- all machine generated dyno sheets will always cross at 5252 rpm no matter what because they are all either calculting torque or horsepower using the same exact formula. If it doesn't cross at 5252 rpm, it does not mean it wasn't a "good run", it means the sheet you are being shown is a total fake.
All accurate dynos can read the exact real horsepower put into them at the time it was tested. The problem comes from hte "correction factors".
The SAE (among others) has come up with an agreed upon set of rules that have to be met to accurately dyno an engine for comparison to any other engine. The problem is that these rules are very hard to meet. So there are cheater sets of calculations, or "corrections", that can be applied to engines run in deviation to the rules. This works ok when properly applied, but most dyno shops don't do that accurately. They do not have an accurate barometer, or ambient temperature thermometer, or much else, to enter into the formula. Also the operating condition of the engines aren't very controlled as to heat soak, coolant temps, and so on, so the #s differ alot from shop to shop. Really bad examples of the inaccuracies, like the "dynojet" numbers from the bash, are easy to find
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So, Tod, you can find power by using a 1\4 mile calculator?
hmmmmm
Chris
'02 Z-24 Supercharged
13.7 @102.45 MPH Third Place, 2007 GMSC Bash SOLD AS OF 01MAR08
hp = weight * (speed / 234)3 from:
http://www.dsm.org/tools/calchp.htm
That's the calculation I used and it appears to be very accurate when comparing Skilz and my dynapack numbers to my trap speeds after the dyno. If you look back at the bash dyno numbers thread I used that same calculation to compare the dynodynamics numbers to Brandon's trap speeds and it came out about right.
Curious to see how Todd feels about that though.
12.770 @ 111.99 Intercooled Eaton M62
Using the ET method, I come up with 231 horsepower
Using the Speed method, I come up with 247 horsepower
....must be really like 210 though.. right? after all it was a M45.
Chris
'02 Z-24 Supercharged
13.7 @102.45 MPH Third Place, 2007 GMSC Bash SOLD AS OF 01MAR08
about how much does a cavalier weigh? i figured 3000lbs with me in it
Using the ET method, I come up with 335 horsepower
Using the Speed method, I come up with 446 horsepower
R.I.P. Brian Klocke, you will never be forgotten
Taetsch Z-24 wrote:Using the ET method, I come up with 231 horsepower
Using the Speed method, I come up with 247 horsepower
....must be really like 210 though.. right? after all it was a M45.
Chris
A bit misleading since you also ran nitrous with that trap speed right? So yes, it's possible....
Brandon my car with me in it, less jack and spare tire weighs 2856 I would think the cage added about 50-100 lbs or so? When I did your calculation for the bash runs I figured you at 2900lbs with a 121mph trap speed that night and came up with 401whp. Were the dynodynamics numbers 398? Seems pretty close. I know at a later date you trapped 124, different weather may have made a difference in power too.
12.770 @ 111.99 Intercooled Eaton M62
yea ill just have to throw the car on the scales, i would think the cage is at least 75lbs, all the tubing is .120 dom mild steel, actually the weather conditions i would say where worse when i trapped 124, very humid and muggy air was very thick, i think once i get a clutch that can hold the power and get traction ill have higher traps
R.I.P. Brian Klocke, you will never be forgotten
Airtonics wrote:Taetsch Z-24 wrote:Using the ET method, I come up with 231 horsepower
Using the Speed method, I come up with 247 horsepower
....must be really like 210 though.. right? after all it was a M45.
Chris
A bit misleading since you also ran nitrous with that trap speed right? So yes, it's possible....
No.
the car had 1 through half of 2nd with the gas before the the switch broke, Ergo the same trap speed i had that day... 103... every run was at 103, 14.2-13.7 at 103.
it OK though
i know Brain Nor my self have told you that before....
Chris
'02 Z-24 Supercharged
13.7 @102.45 MPH Third Place, 2007 GMSC Bash SOLD AS OF 01MAR08
We spoke just before the race and you asked me if you were going to have to spray so I assumed it worked and was on. If you made that power off the nitrous thats great. Can't say I know anyone else trapping that high with an m45, even with a smaller pulley that I recall. I unsure what I trapped that day but I think it was only 101 but again I don't remember.
12.770 @ 111.99 Intercooled Eaton M62
Not many people had a Over drive crank pulley
Chris
'02 Z-24 Supercharged
13.7 @102.45 MPH Third Place, 2007 GMSC Bash SOLD AS OF 01MAR08
HP/Tq numbers are subject to a lot of variables:
- Ambient air temp,
- Elevation,
- Tire/wheel sizes & Weights,
- gear ratios,
- fuel grade & timing (*I know fuel won't make more power, but if the ECU doesn't have to retard timing, you're going to make more power)
- lubricant viscosity, windage,
- etc, etc, ad nauseum.
IF you want to see your numbers thrown for a loop, try switching from dirty blended oil to clean synthetic.
To accutately decide what your car should be putting out, you can calculate it (don't ask me how, but there is a formula out there. Just bare in mind that it's a guide post, and some of the other conditions that I listed are going to affect your total output.
GAM speaks the truth.
My old electrical teacher has me help out on his front engined LS1 dragster...Possibly being able to drive it this year.
He runs it a half quart low and drops 2 tenths of his E/T that way. From an 8.80 to an 8.60 is a big difference.
Buildin' n' Boostin for 08' - Alex Richards
brandon, dont forget you deleted your spare tire well, have no windshield wiper motor etc, and deleted your entire ac system. with all that coupled with your cf hood and racing seats and you weigh what, 175 if that? i would say your car with a full tank of gas and you in it weighs right around 2850-2900.
at the place ive dynoed at they said that dynoing in 3rd gear would result in a higher whp number as the car isnt running a 1:1 ratio, its closer to 1:1 in fourth gear for our cars (so ive heard). i personally watched paul tjepkes' car dyno 155whp in 4th and then it did 167whp in 3rd gear. so... which gear should be believe? dynojet dyno btw...
personally, the same exact place tried dynoing mine in 4th gear and physically could not because it got to the speed limiter before they could accurately measure the max power, so... they did it in 3rd gear, resulting in 151.4whp. frankly, after seeing what happened to paul's numbers through the different gears at the exact same dyno shop i question weather or not my 151.4 was what it really did...
protomec wrote:
-the gear a dyno run is done in has very little effect on the outputed #s since the TWO factors that change do to a gear change are TIME and TORQUE (or power) and the changes are opposite of each other and therefore cancel each other out. Gear changes do have a small effect on the reading due to drivetrain inertia, but the difference is small enough to be within the percentage of error of the dyno anyway.
I dont quite understand this after reading it again...
Say a car redlines with the wheels spinning at 100mph in 1:1 drive
if you change that to say a 1:2 (for the sake of the experiment...basically your ending up with a shorter gear by 50
IT now redlines at 50mph.
But the dyno looks at the numbers based on time and the torque acheived
so if it takes 3/4 of the time it took to get to 100mph to get to 50mph would it not see the 1:1 run as a decrease in horsepower and therefore a more accurate interpretation? (due to the 1:1 ratio?)
This basically applying true in the dynapack dynos since they actually measure torque at the wheels, So I would think the torque multiplication of the trans would result in more torque and less time to acheive a desired redline or max torque reading...
I dunno just open minded thinking, maybe I'm reading it wrong, I'm tired.
Buildin' n' Boostin for 08' - Alex Richards
