I've been trying to fool around with some math but apparently I haven't got that far to be able to do so. I just want to see how close I can come to estimating my trap speed based off what I already know about my car.

Before it trapped a best of 100.89mph. This was with a race weight of 2,680lbs (including driver). At that time it layed down 173whp. I'm anticipating 190whp shortly once I get back on the dyno and for entertainments sake I want to see if any of you guys can give me a good trap speed estimate considering all else is equal (humidity, temp, and elevation). Pretend gains throughout the usable power band will be equal as well. Right now at 180whp I'm holding on to 8-10whp more past peak than I was at 173whp.

Would it be safe to say that with 190whp I could be trapping in the 102mph range. That would only be 1.1mph trap speed increase for 17whp which seems very reasonable. Any input would be appreciated.

 

I unfortunately don't have any concrete information (aside from the links below) that will help you in calculating your estimates, but I am extremely curious as to where your intense interest in trap speed came from. By no means do I mean this in a derogatory way, I have simply never seen anyone who places such emphasis on trap speed over E.T., and I'm interested in hearing about it. Good luck with your calculations, and if you haven't already visited some of these sites, perhaps they will be of use in some way.

http://www.karlsnet.com/mopar/formulas.shtml

http://www.rpmoutlet.com/formula.htm

http://www.dsm.org/tools/calchp.htm

 

try this formula...it should do the trick

to calculate 1/4 mile ET and MPH from HP and Weight

ET = ((Weight / HP)^.333) * 5.825

MPH = ((HP / Weight)^.333) * 234

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Padawan &raquo;</TD></TR><TR><TD CLASS="quote">I unfortunately don't have any concrete information (aside from the links below) that will help you in calculating your estimates, but I am extremely curious as to where your intense interest in trap speed came from. By no means do I mean this in a derogatory way, I have simply never seen anyone who places such emphasis on trap speed over E.T., and I'm interested in hearing about it. Good luck with your calculations, and if you haven't already visited some of these sites, perhaps they will be of use in some way.

http://www.karlsnet.com/mopar/formulas.shtml

http://www.rpmoutlet.com/formula.htm

http://www.dsm.org/tools/calchp.htm </TD></TR></TABLE>

Here is how I look at it. Trap speed is how fast the CAR is, ET is up the the driver. If I know what my car should be able to trap I can deduce what my ET should be. In the past I became very good at launching with a few 2.0 60' times on true street tires (not drag radials) and was able to pull 2.1's on a fairly regular basis. However that was back on my stock clutch and flywheel and at the time I went to the strip quite frequently. I now have a new clutch and flywheel that I will essentially have to relearn launching with, but I see my drag strip days to be limited (want to start doing track events) so I might never learn my new setup well enought to pull as consistent good 60' times. Therefore if I only go the track once more the trap speed will be more important, unless I happen to quickly adapt to my new setup and learn how to launch it as well as my stock setup.

Thanks for info both of you have given.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by venom &raquo;</TD></TR><TR><TD CLASS="quote">try this formula...it should do the trick

to calculate 1/4 mile ET and MPH from HP and Weight

ET = ((Weight / HP)^.333) * 5.825

MPH = ((HP / Weight)^.333) * 234


</TD></TR></TABLE>

Dang those seem to be some of the best formula's I have seen. Saying I had 173whp (converted to flywheel using 16% loss) and weighed 2680 it said I should trap 99.89. I trapped 100.89mph and thats not taking into account dyno numbers being corrected (meaning I was probably making more that night at the track) and theoretical weight loss from a lightened flywheel (which I had on that run).

With 190whp (225 flywheel) it said I should trap 102.5mph which seems very reasonable.

 

Although the tracks average the last 60ft to give you your trap speed. Using that formula would give you an "instantaneous" trap speed? So calculating it using formulas may give you a higher trap than if you were to actually go to the track. But then again the differences may be neglible.

 

Brock i think it will Bring you down to about the 13.5-13.3 area and bring up your MPH almost 3-5mph. Call me crazy but i can almost bet money it will be inbetween there.

Good luck

 

I don't know how much you can trust a formula. It's all about what's under the curve, if you only make 3-4 whp high in most of it, than spike in the last 1000 rpm, it won't be as significant than if it's like 8-12 throughout the range.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by SoCal ITR &raquo;</TD></TR><TR><TD CLASS="quote">I don't know how much you can trust a formula. It's all about what's under the curve, if you only make 3-4 whp high in most of it, than spike in the last 1000 rpm, it won't be as significant than if it's like 8-12 throughout the range.</TD></TR></TABLE>

That's correct. You can't get a very accurate estimate from just PEAK hp. I know that on a good run you should be near the peak most of the time, but the whole curve still matters.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by fredtoast &raquo;</TD></TR><TR><TD CLASS="quote"> You can't get a very accurate estimate from just PEAK hp.</TD></TR></TABLE>

Period !!!


Greg

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by SoCal ITR &raquo;</TD></TR><TR><TD CLASS="quote">I don't know how much you can trust a formula. It's all about what's under the curve, if you only make 3-4 whp high in most of it, than spike in the last 1000 rpm, it won't be as significant than if it's like 8-12 throughout the range.</TD></TR></TABLE>

Well right now setting at 180whp it does just that. It has only gained 7whp at peak, but holds on to 8-10whp past it (than previous). This however is at 180whp, I now have an exhaust and plan to tune my cam gears once I get to the dyno again. We'll just have to see I guess.

 

The slope of the curve is much more important than the highest value.
The area under the curve compared to the previous area under the curve is most important!

 

Generally it takes about 10hp for a tenth. Again this is a general rule of thumb.

 

Umm not in a honda man lol, like 4-5 wph does a tenth in an ITR id say...

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Header Tech &raquo;</TD></TR><TR><TD CLASS="quote">Generally it takes about 10hp for a tenth. Again this is a general rule of thumb.
</TD></TR></TABLE>

Rule of thumb?

The difference between 500 hp and 510 hp will not be 1/10 in the quarter, and that doesn't even consider weight.

There are too many variables to make a rule of thumb that simple and that reliable.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by SoCal ITR &raquo;</TD></TR><TR><TD CLASS="quote">There are too many variables to make a rule of thumb that simple and that reliable.</TD></TR></TABLE>

This is sooo true. Driver is key as well...and i have seen Brock in action. This is why i said the times i did previously