Report on headers
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From: Kent WA
Originally Posted by seanvicious
there was an article about how a 6.9L with a banks turbo made 196HP at the rear wheels. i'd say it'd be safe to guess the 185 stock hp number is measured at the flywheel.
Since it is calculating moving a given weight in a specified time through a pre-determined distance it seems logical to me that it should be calculating wheel horsepower - since the wheels are what actually move the weight.
If that is the case, then the mods that KJLYPW has done gained him more like 60 or 70 HP instead of 41, since the original wheel HP is almost certainly 20 or 30 HP less than the flywheel HP. That seems pretty hard to believe for such relatively simple and inexpensive mods. Pretty hard to believe Ford Engineers would leave behind that much "low-hanging fruit"...
Once I get mine running right, I am going to do a few 1/4 mile passes before making any mods and punch the numbers into that calculator and see what it comes up with. Then I'll repeat it after each mod I do. That ought to make for some interesting analysis.....
Last edited by CheaperJeeper; Sep 18, 2006 at 11:58 PM.
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Originally Posted by CheaperJeeper
Well, if you make the assumption that the calculator is estimating HP at the flywheel then it is pretty well worthless - because it has some best-guess mechanical loss constant built into it that may or may not be anywhere near accurate for a given vehicle.
Since it is calculating moving a given weight in a specified time through a pre-determined distance it seems logical to me that it should be calculating wheel horsepower - since the wheels are what actually move the weight.
If that is the case, then the mods that KJLYPW has done gained him more like 60 or 70 HP instead of 41, since the original wheel HP is almost certainly 20 or 30 HP less than the flywheel HP. That seems pretty hard to believe for such relatively simple and inexpensive mods. Pretty hard to believe Ford Engineers would leave behind that much "low-hanging fruit"...
Once I get mine running right, I am going to do a few 1/4 mile passes before making any mods and punch the numbers into that calculator and see what it comes up with. Then I'll repeat it after each mod I do. That ought to make for some interesting analysis.....
Since it is calculating moving a given weight in a specified time through a pre-determined distance it seems logical to me that it should be calculating wheel horsepower - since the wheels are what actually move the weight.
If that is the case, then the mods that KJLYPW has done gained him more like 60 or 70 HP instead of 41, since the original wheel HP is almost certainly 20 or 30 HP less than the flywheel HP. That seems pretty hard to believe for such relatively simple and inexpensive mods. Pretty hard to believe Ford Engineers would leave behind that much "low-hanging fruit"...
Once I get mine running right, I am going to do a few 1/4 mile passes before making any mods and punch the numbers into that calculator and see what it comes up with. Then I'll repeat it after each mod I do. That ought to make for some interesting analysis.....
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From: Kent WA
I did think of one other very real possibility. The numbers that KJLYPW posted may be a bit "off".
In playing around with the calculator I found that entering a 1 mph lower top speed resulted in a reduction of approximately 9 calculated HP. So being just a couple of MPH off makes a HUGE difference in the final estimate.
KJLYPW, how were you measuring your 1/4 mile run? Did you use your speedo and a watch, or were you running the 1/4 traps at a local track? 80-90 flywheel HP seems like a lot for the mods you have.
Just trying to figure out how "real" are the numbers that calculator gives....
In playing around with the calculator I found that entering a 1 mph lower top speed resulted in a reduction of approximately 9 calculated HP. So being just a couple of MPH off makes a HUGE difference in the final estimate.
KJLYPW, how were you measuring your 1/4 mile run? Did you use your speedo and a watch, or were you running the 1/4 traps at a local track? 80-90 flywheel HP seems like a lot for the mods you have.
Just trying to figure out how "real" are the numbers that calculator gives....
Senior User
Joined: Aug 2006
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when I do this header mod, I will have to dyno the truck.
taking donations....
seriously though, if I do get the headers I wont be able to afford a dyno, since I cant afford the headers in the first place. maybe it might be worth $5 to some of you.
taking donations....
seriously though, if I do get the headers I wont be able to afford a dyno, since I cant afford the headers in the first place. maybe it might be worth $5 to some of you.
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cheaperjeeper, another thing is that he doesn't know exactly how much his truck weighs. i have a banks catalog i'm looking at right now, and it specifically says the stock 7.3L makes 185hp at the flywheel.
2new2fords, i don't know where you're located, but around here 3 pulls on a dyno run right around $100.
2new2fords, i don't know where you're located, but around here 3 pulls on a dyno run right around $100.
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From: Powell River B.C.
The stock truck is rated at 185 at 3000 rpm. In doing a 1/4 test, I used basic method of speedometer and odometer, trip guage set to 0 and go to see how fast you are going once you reach .4km. If you enter the rated HP of 185 seems about right, you would get 70 @ 19.5 seconds. I got to 75 when I reached .4 km, if you want to be that technical I guess I should have waited till .40552 km but my odometer doesn't go that low. Also keep in mind the 1/4 calcualtor idea is to give you a rough idea, your engine doesn't start out at 3000 rpm or stay there for the whole 1/4 mile. Bottom line is the 1/4 mile calcuator gives you a rough idea as to how to quantify your performance increase, without having any expensive equipment available. On top of that, the stock performance numbers seam reasonable enough to assume that my findings after the mods are "ball park" within reason. To be truly accurate a real dyno test is the real answer, lets face it, the 1/4 test has too many variables, flat road or not, standard or auto transmission, shift points, etc, etc.
Last edited by KJLYPW; Sep 19, 2006 at 09:36 PM.
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Posting Guru
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From: Kent WA
Originally Posted by KJLYPW
The stock truck is rated at 185 at 3000 rpm. In doing a 1/4 test, I used basic method of speedometer and odometer, trip guage set to 0 and go to see how fast you are going once you reach .4km. If you enter the rated HP of 185 seems about right, you would get 70 @ 19.5 seconds. I got to 75 when I reached .4 km, if you want to be that technical I guess I should have waited till .40552 km but my odometer doesn't go that low. Also keep in mind the 1/4 calcualtor idea is to give you a rough idea, your engine doesn't start out at 3000 rpm or stay there for the whole 1/4 mile. Bottom line is the 1/4 mile calcuator gives you a rough idea as to how to quantify your performance increase, without having any expensive equipment available. On top of that, the stock performance numbers seam reasonable enough to assume that my findings after the mods are "ball park" within reason. To be truly accurate a real dyno test is the real answer, lets face it, the 1/4 test has too many variables, flat road or not, standard or auto transmission, shift points, etc, etc.
Thanks again for providing the link man. BTW, no criticisim intended in ANY of my remarks. Totally an analytical exercise.
Last edited by CheaperJeeper; Sep 19, 2006 at 09:45 PM.
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it's because i've been trying to post a link...
go to double-u double-u double-u dot the diesel garage dot come and click on calculators on the left.
you can calculate HP at the flywheel and rear wheels based on your vehicle weight and 1/4 mile trap speed.
go to double-u double-u double-u dot the diesel garage dot come and click on calculators on the left.
you can calculate HP at the flywheel and rear wheels based on your vehicle weight and 1/4 mile trap speed.
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From: Kent WA
Sean,
That one is really no different. It is posted right there on the page that it assumes an 18% drivetrain loss. Is that the correct # for these trucks? Who knows?
On that one a 75mph run with 6870 curb weight shows 213 HP at the flywheel and 197 HP at the drive wheels.
Using the same weight and a 71.5mph run shows 185 at the flywheel and 170 HP at the drive wheels.
Who knows which is right? Without the data for a baseline (run before the mods) it is impossible to tell. Like he said though - it gives you a "feel" for what kind of improvement you get - especially if you use the same calculator for both "before-n-after" runs.....
That one is really no different. It is posted right there on the page that it assumes an 18% drivetrain loss. Is that the correct # for these trucks? Who knows?
On that one a 75mph run with 6870 curb weight shows 213 HP at the flywheel and 197 HP at the drive wheels.
Using the same weight and a 71.5mph run shows 185 at the flywheel and 170 HP at the drive wheels.
Who knows which is right? Without the data for a baseline (run before the mods) it is impossible to tell. Like he said though - it gives you a "feel" for what kind of improvement you get - especially if you use the same calculator for both "before-n-after" runs.....
