Dyno vs Trap Speed vs Actual HP

Quik95SC

SCCoA Member
I have been wondering after this past weekend of racing in KY about how far off the HP/ET Calulators are on the internet. I have used several and they all seem to be way off from my perceived actual. Heres the situation.

Best Run in KY this weekend was a 12.214 @ 113 mph

Best Dyno to date was at the 2011 shootout of 350 rwhp.

When I punch in my car race weight (just over 3/4 tank) I get vary different HP numbers. Now I realize they don't mean much I was just wondering about why the large difference.

Wallaceracing has these numbers.

Your Horsepower computed from your vehicle weight of 4000 pounds and MPH of 113 is 474.36.

Then based on my ET I get this: Your HP is 433.88 computed from your vehicle weight of 4000 pounds and ET of 12.214 seconds.

Both of these are great, but I am wondering how far off these things are typically, especially when I only dyno'd 350 RWHP at the shootout this year.

Also when I punch in my actual dyno number HP and weight I should only be able to run a 13.025 @ about 103 MPH

I understand there will always be a difference, but this large of a difference?

Just wondering really. Are our cars that strange and throw off normal N/A HP numbers? I wouldn't think so.

But I don't really know hence why I am asking.

Smitty
 
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Using my calculator I get 365rwhp which is just about right on for the weather conditions, etc. I also get an ideal ET of 12.06 so that means you have work to do son!

The online calculators do not work right for any car. Sorry, not posting mine. ;)

Using my calculator it also says that David's car weighing in at 3950 (guess) should run 10.75's with his HP level and was making 508rwhp at the track that day. David also has work to do. lol
 
Mine weighs in right about 4000....it was 4080 on Kevin's scales a few years ago with street tires, spare tire and jack. Best time for the weekend was 11.84.
 
Kurt,

Yours is calculating about 385rwhp but your numbers are skewed a little I think because your car seems to be much stronger in the first half of the track than the second. This makes the car seem super efficient but I think it may be more a matter of a lack of top end making the first half look better compared to how the car runs out the top end.
 
Using my calculator it also says that David's car weighing in at 3950 (guess) should run 10.75's with his HP level and was making 508rwhp at the track that day. David also has work to do. lol

David

10.75 with the weather we had, or with optimum weather and track conditions ?

David
 
Smitty if you want screwy numbers let Dave do the math on these. At Englishtown 2 years ago it was 45 degrees and clear when I ran 11.63 @ 119. and change.

Now go ahead Dave, tell me how much work I have to do :p lol

Ira
 
Kurt,

Yours is calculating about 385rwhp but your numbers are skewed a little I think because your car seems to be much stronger in the first half of the track than the second. This makes the car seem super efficient but I think it may be more a matter of a lack of top end making the first half look better compared to how the car runs out the top end.
I agree that my car seems stronger in the first half, especially since I generally have lower MPHs that anybody else running the same times....I guess I need to do some upgrades at some point.
 
David

10.75 with the weather we had, or with optimum weather and track conditions ?

David

10.75 with the weather you had. Track conditions I can't comment on but you are losing about .15-.2 sec most likely in the first 60 ft. If you can pick up just .1 in the first 60 that generally translates to .2 in the 1/4, more or less. I think that with good weather and a better launch you could definitely beat your nitrous times.
 
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Smitty if you want screwy numbers let Dave do the math on these. At Englishtown 2 years ago it was 45 degrees and clear when I ran 11.63 @ 119. and change.

Now go ahead Dave, tell me how much work I have to do :p lol

Ira

Ira, how much does your car weigh?
 
I apologize, it's been a long time since I used this formula and I now realize I was applying the wrong correction factor. :eek:

Also, if Brian ran exclusively in a slow mph lane, then his calculations are off. IN order for this to work properly I need valid ET, MPH, and race weight values.

Revised #'s:

Smitty 342rwhp
David 481rwhp
Brian 422rshp
Chris 446rwhp


I didn't make that up - that is using the exact same formula on all 4 cars. On Brians I added 4mph because of what Chris said.

Ira, you didn't reply with a weight, but if we assume 4000lbs also, you'd be looking at 451rwhp.
 
I apologize, it's been a long time since I used this formula and I now realize I was applying the wrong correction factor. :eek:

Also, if Brian ran exclusively in a slow mph lane, then his calculations are off. IN order for this to work properly I need valid ET, MPH, and race weight values.

Revised #'s:

Smitty 342rwhp
David 481rwhp
Brian 422rshp
Chris 446rwhp


I didn't make that up - that is using the exact same formula on all 4 cars. On Brians I added 4mph because of what Chris said.

Ira, you didn't reply with a weight, but if we assume 4000lbs also, you'd be looking at 451rwhp.

I liked your first rwhp estimate better :cool: I'm also going to try and get a current race weight sometime next week.

David
 
I've never been on a dyno for a number, just tuning purposes. What do you estimate mine made on its last combo? 12.789@103.74 estimated 3700lbs with driver. a few years ago it weighed in at 3650 without driver but I've done some weight reduction along with adding weight.
 
The numbers I've been kicking around today were from my very last run wich was the "fast" lane that everybody thought was correct.
 
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