From: hotrod@dixie.com (The Hotrod List)
Newsgroups: alt.hotrod,wiz.hotrod
Subject: Re: Speaking of 1/4 mile performance...
Date: 27 Jan 93 16:16:43 GMT
Reply-To: hotrod@dixie.com
Organization: Dixie Communications Public Access.  The Mouth of the South.
To: hotrod@dixie.com
Posted-Date: Wednesday, Jan 27 11:16:36
X-Sequence: 3634
X-Gifs-To: met@sunset.cse.nau.edu
X-Gifs-From: ftp.nau.edu

> From butler@comm.mot.com Tue Jan 26 10:15:56 1993
> > 	That covers all ratios available for GM 12 bolt carriers.

Which are presently legal on dragsters per NHRA rules.  However they are
not the only governing body for drag racing.

> 	Thanks for the info on the tires.  I've always wondered what 
> tires where used and what they cost.  With 3-5 runs/tire that's a 
> hefty amount of $$$ left as rubber on the track.
> 
> 	You say 12 runs/engine.  What has to be done then when 
> they're expired?  What can you use over?

Well not necessarly expired but if the engine held together that long
it probably well over due time to tear it apart and closely inspect
it for damage, metal fractures, and weak spots.  Its a lot better to do
it this way than find out on the strip when you get eliminated because
some bolt broke form fatigue.

> 
> 	Anyway, back the original concept of engine revolutions per run, I 
> submit this.
> 
> 	If the max the engine can turn is 10000RPM, then the *greatest* number 
> of revolutions possible from green to finish is
> 
> 	10000RPM * 1min/60s * 4.5s/run = 750 eng_revs/run

lets use a modest 5.0 sec and then call it 835 rpms.
> 
> and there ain't nothin' anyone can do about it unless they make the 
> engine turn faster or make the ET longer!

Yes some engines turn more rpm's than that.  If you notice most blown dragster
engines occur in the first 2 sec. when tire slippage is at its peak and
rpm's sometimes go crazey often hitting 14K + which can rip through the 
engine pretty badly.

> 
> 
> 	Taking another tack and using your tire rotation example (the 38" tire) 
> I get the total number of axle_revs per quarter mile to be (slippage ignored) 
> 
> 	5280'/mi * .25mi/run * 1axle_rev/9.94' = 132 axle_revs/run. 
> 	Using a rear end with 2.73 gears gives the total engine revs as 
> 	2.73eng_revs/axle_rev * 132 axle_revs/run = 362 engine_revs/run

let's use the 3.23 axle its more popular especially with NHRA events.
which gives us closser to 428 rpm's.
> 
> 
> 	Now, clearly my initial estimate of 750 engine_revs/run (above) is high 
> because I assumed that the engine was running at "redline" the entire time, 
> which I do not believe to be the case.  The estimate given immediately above 
> using the tire rotation (362 engine_revs/run) is somewhere near a lower bound 
> since with tire slippage this number has to increase.  As such, my the 
> estimate  from my original posting of 750 engine_revs/run is actually 
> close to an upper bound, based on the data you gave me, with the total 
> number of engine_revs/run being somewhere between 362 and 750.

Actually when you consider tire slippage almost continius through the 1/4 mile
as well as clutch slippage you probably closser to the 835 revolutions 
than the lower figuers.  Actually some one should set up a pulse counter
on a run to give you some accurate numbers on this.

>  And of 
> course, the number of cylinder firings is somewhere less than
> 	750engine_revs/run * 4pops/engine_rev = 3000 pops/run

it could hit as high as 3,350.

> 	How much fuel do you use per run?


Well I'm not sure on the consumption rate in a dragster.  My experience
is mainly in the SuperStock and Modified Production classes.  The fuel
is costly enough here around $3.00 per gallon after adding octane
boosters etc.  My guess is a dragster uses at least 1 gallon per run and
with the cost of nitro at least $20.00 per run.  A couple years back one
of the nitro fuel dragsters was pitted next to me and through
conversation with the owner he claimed the the prior year he took his
total expenses and divided into the number of runs the car took and
averaged just under $2,000.00 per run.  He claimed that as the car gets
older this sum comes down as there is a great initial investment.
However he didn't ever expect it to get near a cheap $1,000.00 per run.
No I ain't got that much money but if someone wanted to sponsor me I'm
all ears.

> dennis
----------
Posted by: hotrod@dixie.com
Newsgroups: alt.hotrod,wiz.hotrod