Big Tire Outlaw questions

[Dave Rifkin]

I went to Atco yesterday; they had Pro-Mods, old time funny cars and a group they called "Big Tire Outlaws". These were great fun to watch but, for some reason, they only ran 1/8 mile passes. I asked someone in the stands why that was and he said because they'd run too fast in the 1/4 and would have a hard time getting them stopped. What I found strange is the Pro Mods ran 1/4 (or 1,000' I'm not sure) and they are faster than the Outlaw cars. Anyone familiar with these cars who can explain it to me?

Also, I noticed a bunch of fast cars running nitrous; I have seen plenty of cars running nitrous but, these guys purged the hell out of the lines before each pass. You would almost think they'd have to refill the tanks after each run; what's the reason for such a long purge?

[VintageMusclecar]

The Pro Mods are likely ~1000 lbs lighter than the big tire outlaw stuff. That extra weight is a hell of a lot harder to slow down (never mind accelerate lol).

[Gary Anderson]

And possibly they are older cars whose chassis/cages won't certify for the times/speed they could run in the quarter.

[Day2_69Z]

BINGO !

[Dave Rifkin]

Any thoughts on the lengthy nitrous purges? Just for show?

[VintageMusclecar]

That, and maybe to fine-tune the bottle pressure before a pass?

[Day2_69Z]

Eric,
You're close....

None of it is for show, unless they also do the long Smokey John Force style 1/2 Burn outs.

Keep in mind these Nitrous cars not only run on high octane racing fuel, they are also running ON NO2 before the purges
Multiple bottles in unison plumbed through multiple regulators, computor monitored fuel injection and manifolds. (No high tech explanation)...
Most cars on the high end of the class are using
4, 5, 6, 7 & 8 stages , ....(my brother tunes 8 stages)
The full bottles are warmed in electric blankets prior to a run.....barometric and ambient temperature along with the track surface temperature all play games with the gas/liquid mix in the bottles, feed lines and through the system until the NO2 REACHES the Cylinders.......
The Purge time is dictated by the volume it needs pure fuel (Nitrogen) & (Oxidizer) to run the entire pass .... the More Volume Fuel Injection needs along with the electronic(computer) controlled multiple systems to feed the huge cubic inch displacements dictates " Clean mixed & consistent pressures" feeding 900+ C.I. Engines.

The Pro Nitrous Pictured is a very Competitive car, finished 4th last year in National Points .
Runs Musi /Sonny's / Martin 903 or 942. With 8 stages... tuned to run 6-8 depending on track conditions.
This car Runs 3.70's @ 200. PDRA.
The bottles you see mounted up front
(Fire Bottles)
ARE NOT the NO2 Bottles. . .they are mounted Iin the Car, passenger side where the Pit crew member activates them before the Burn out.

[Day2_69Z]

Dave,
I hope that purged your curiosity....

PDRA is running at Memphis this Friday and Saturday.....

Live on MM1
MOTOR MANIA TV CHANNEL 1
GO TO. 660 DRAGS OR. PDRA LIVE FEED
online
Tom

[Dave Rifkin]

Yes, thank you for the explanation; it makes sense to me now.