xxx
258 at the rear wheels is like 310-325 at the flywheel. FWHP for the factory 4V Clevelands was only 320-335 so be happy with what you've got goin' on under the hood.xcgxl said:258 rwhp
I don't know whoever said to take dyno figures lightly, but they're usually the best indication of output available. ETs are arguably worthwhile, but traction losses and bad chassis combinations can slow a car such that ET is meaningless when trying to "reverse engineer" engine power.TTNOS8 said:But as said a gazillion times before, take dyno figures lightly.
Its been an arguing point in this forum for a while now.davis said:I don't know whoever said to take dyno figures lightly, but they're usually the best indication of output available. ETs are arguably worthwhile, but traction losses and bad chassis combinations can slow a car such that ET is meaningless when trying to "reverse engineer" engine power.
:davis:
..davis said:258 at the rear wheels is like 310-325 at the flywheel. FWHP for the factory 4V Clevelands was only 320-335 so be happy with what you've got goin' on under the hood.
On a Dyno Jet maybe, but not on a Dyno Dynamics!
I don't know whoever said to take dyno figures lightly, but they're usually the best indication of output available. ETs are arguably worthwhile, but traction losses and bad chassis combinations can slow a car such that ET is meaningless when trying to "reverse engineer" engine power.
I respectfully disagree. A dyno is the worst method of calculating actual HP.
Also ET is virtually meaninless in calculating HP - you must use MPH, which is a very accurate method. Unlike ET, driver ability or chassis setup doesnt adversly effect MPH to any appreciable degree. Being a drag racer, and engineer, i would have thought you would have known that!
:davis:
The more I learn about what is happening during each pass (from data capture/analysis), the more I realize that I know nothing. I've designed dozens of pieces of hardware and written software to support my data collection and analysis of what happens everytime I strap in and light it up. I even built a small, high speed CMOS imager running at 110 frames per second to take pictures of my tires throughout passes. I used a scaled background behind the tire so that I could see how much growth they underwent, how much deflection and distortion due to high speed and wind drag...can you even imagine all of the "tire" data I collected? Several gigabytes of video data alone. I wrote an image processor to calculate the variation in tire size from frame to frame so that it plotted a graph of tire changes for the course of the entire pass. I had such meaningful information as average tire size, peak tire growth and maximum launch distortion values at the end of it all. I tried several different brands and types/compounds of tires. I had a whole slew of information about which grew more/less, distorted more/less and when I was done, I was still left wondering how to actually use all of that data to actually do anything meaningful at all. I even thought about trying to sell it to a tire manufacturer to use in some marketing effort. You can almost imagine a series of still frames of OUR TIRE versus COMPETITOR'S where our's is somehow supposedly better and this picture supposedly proves it.Racer said:Being a drag racer, and engineer, i would have thought you would have known that!
No, but traction and driving do and so does air density when you have to push the same car through denser air, you loose MPH. If you bring your own air with you, as in blown applications, are you making more or less HP as a result of the reduced MPH?STROKEXD said:Add to Racer's sentiments there Davis, simple laws of physics that to move a given mass over a set distance which results in a certain speed is all you need to calculate true HP, in the most accurate way possible. And ET hasn't got bugger all to do with it.
However, when you use HISTORICAL data against recently observed data, both ET and MPH are useful in determining whether you're making the power you should be for a known environmental situation. Neither one alone or together are the Holy Grail in defining what kind of power an engine is capable of making. At best, they can be an approximation of how much power was USED to accomplish a given task.davis said:ETs are arguably worthwhile, but traction losses and bad chassis combinations can slow a car such that ET is meaningless when trying to "reverse engineer" engine power.
Well I'm going to get stuck into you a bit here Davis because you've got a really major flaw in your logic here.davis said:Racer, please try not to quote me using your words such that it is difficult to distinguish who said what.
MPH is (respectfully) BULLSHIT. You can stick a 4.88 gear in a 3600# car and have it run mid 12s at under 100 MPH. How much HP is that? Math says 260-ish RWHP. Somehow I'm thinking that a big block 427 is making more than 260-something RWHP.
I've seen funny cars go up in smoke down the track and run only 140 MPH. How much HP is that? What is being measured, how much traction is lost going down the track? A friend of mine runs 7.20s in a 3200# car on 10.5W tires smoking them the entire length of the track. How much power is he making?
A dynamometer is by definition a device for measuring mechanical power. From the available torque, horsepower is calculated using engine RPM and simple math.
Try not to tell me what I should know or not. I stand by what I said. A dyno is the best way to tell power. A POS dyno is just as good as a POS anything else.
I think that the point some may try to make is that the actual numeric output from a dyno is not to be compared to other dyno figures, as was stated previously "take dyno figures lightly." I read this to mean that dyno output figures vary between different dynos. From the perspective of one guy makes XYZ power at ABC dyno and EFG power from OPQ dyno, the numbers are meaningless. One the same dyno, assuming that it is fairly consistent, the measurements can be used to properly tune the vehicle for best power given the dynamics of the environment.
Maybe some hardware out there sucks, and yes, we largely use DynoJets for chassis dynoing in Arizona. However, my comments are related to all dyno types whether engine or chassis.
They are the only way to accurately measure engine power, when properly calibrated and used by an astute professional. Any bloke can misuse even the simplest measuring device. I don't suppose that anyone here ever cut a board too short in their lives, regardless of what they "should" know or not.
Your argument that driver ability and chassis setup doesn't adversely affect MPH is BULLSHIT. Try this. Launch your car at the lowest possible RPM to get it moving. Stay in first gear the entire length of the track with your foot mashed to the floor and the engine bouncing off of the rev limiter. What happened to your MPH and how much power did your engine make? I'm guessing that your MPH will be WAY OFF. Are you saying that your engine makes more power in 2nd gear than 1st just because it allows the rear wheels to turn more rapidly?
As a racer, I know what you mean by using MPH to see if your power is off, but it is still very dependent on known good data and consistent driving ability AND making a good run down the track. If you don't think that driving affects MPH, get out of the groove and see if your MPH slows. It will, as will your ET. It doesn't mean that you're making any more or less power. MPH just tells you how much power you effectively used, not how much power you've got available.
One day on one of my blown big block cars, I jumped the boost up to 22% over driven, ran both sides of the track repeatedly as a result of traction loss. Had this whole "S" thing going down the track. I don't think it got over 100 MPH without me having to brake to get it to return somewhere near to the middle of my lane. It was probably making about 1150-1200 HP on that day, certainly more than enough to overpower the chassis. Still ran like an 11.25. For a 3500-3600# car, how much power does my 100 MPH pass say that I make? How much will MPH be affected if you stutter and miss a shift? Driving has a lot to do with ET and MPH and bad driving will make both worse.
The more I learn about what is happening during each pass (from data capture/analysis), the more I realize that I know nothing. I've designed dozens of pieces of hardware and written software to support my data collection and analysis of what happens everytime I strap in and light it up. I even built a small, high speed CMOS imager running at 110 frames per second to take pictures of my tires throughout passes. I used a scaled background behind the tire so that I could see how much growth they underwent, how much deflection and distortion due to high speed and wind drag...can you even imagine all of the "tire" data I collected? Several gigabytes of video data alone. I wrote an image processor to calculate the variation in tire size from frame to frame so that it plotted a graph of tire changes for the course of the entire pass. I had such meaningful information as average tire size, peak tire growth and maximum launch distortion values at the end of it all. I tried several different brands and types/compounds of tires. I had a whole slew of information about which grew more/less, distorted more/less and when I was done, I was still left wondering how to actually use all of that data to actually do anything meaningful at all. I even thought about trying to sell it to a tire manufacturer to use in some marketing effort. You can almost imagine a series of still frames of OUR TIRE versus COMPETITOR'S where our's is somehow supposedly better and this picture supposedly proves it.
The truth in knowledge is realizing that you know nothing. What an excellent oxymoron.
Take Care.
Rob!
:davis:
davis said:I don't know why you guys keep bringing up ET. My exact words were:
Quote: Originally Posted by davis
ETs are arguably worthwhile, but traction losses and bad chassis combinations can slow a car such that ET is meaningless when trying to "reverse engineer" engine power.
OK ***. Tell me how much HP is used by a 3600# car crossing the finish line at 1 MPH?STROKEXD said:HP from 1/4 mile mph is the most mathematical appropriate and correct method in theoretical physics for calculating HP
brenx said:My only comment sorry just had to say "It's not how much power it has got. It's how you drive it."
You can have all the power in the world and still drive like shit.
Brenden
ROFLOL :wnc:davis said:OK wise ass. Tell me how much HP is used by a 3600# car crossing the finish line at 1 MPH?:davis:
Well not much HP at all. A fraction of a HP, it's about .3 of HP. I'm sure you can use a calculator so check it out yourself as well..davis said:OK ***. Tell me how much HP is used by a 3600# car crossing the finish line at 1 MPH?
Well the head wind cancels out, and is incorprated in the calculations. So two cars (A & B) of the same weight both finish the line at 1mph. Except car A had a 40mph head wind.davis said:Are you saying that another 3600# car crossing the finish line at 1 MPH with a 40 MPH head wind uses more, less or the same amount of HP to accomplish that goal?
Well it's not my math, it is established physics theory chum. If you still think it's bullshit then you seem a tad conceited to me. Are you right and all the textbooks and theoretical physicists in the world wrong then?davis said:Show your math or quit running your mouth. You keep talking like HP isn't a measurement of work over time and that some final calculation is somehow meaningful with regard to the output of the engine. You criticize my use of variables as being overused in the same voice that you use to say that you somehow have an exact expression of the total HP used simply by looking at the MPH figure at the end of the pass. I say BULLSHIT. You're dropping variables or your calculations are as far out as your idea of a "simple" formula that will accurately characterize total power involved in making a certain MPH number. Either retract your insults about my education, physics and logic or prove yours using the math you suggest that you concur with Newton on.?
Already covered this. It is really clear and simple! One could say "What happens to the dyno print-out when you pull off 3 ignition leads during the run". Well you get less HP don't you.davis said:Let's see it, *****. What are you actually producing with such a calculation? The sum of all power values used to produce the MPH? The HP *average* throughout the pass? What is so EXACT that you're spewing on about?
Then, once you get all of that done, at what MPH did the guy who jumped on his brakes just before hitting the MPH lights do to your "formula?" What happened to your math when a bloke has a 15 MPH head wind or even a 15 MPH tail wind? Come on out with your supposed EXACT science that is so perfect that you throw insults as me like you're some kind of expert and I'm not quite out of toilet training just yet.
Put your proof where your mouth is or get off your soapbox.
:davis:
***** edited by xa coupe ******