Super gas/comp/Street forums?

[voltdr]

I wonder about this also. If we have a car that runs SG, 9.90 @ 160ish. If the stop stall is
4200 for 3.5 seconds. How fast is the car at 4200 for the 3.5 seconds? Lets just say it's
130 mph and then gets to 160 at the finish. If the same car is 4000 rpm for 2.5 seconds. Is that car now running 125 mph. Does it get to 165? The car is at a slower speed and has more time to accelerate, but can it over come the lower rpm while on the stop to run faster at the stripe? Or, is it better to be at a faster mph on the stop and not have as much mph to gain? I have heard many discussions about this but I'm still not sure which one is better?
Dan
SC4698

[Lenny5160]

Originally Posted by voltdr

I wonder about this also. If we have a car that runs SG, 9.90 @ 160ish. If the stop stall is
4200 for 3.5 seconds. How fast is the car at 4200 for the 3.5 seconds? Lets just say it's
130 mph and then gets to 160 at the finish. If the same car is 4000 rpm for 2.5 seconds. Is that car now running 125 mph. Does it get to 165?

It doesn't really impact what you are trying to say, but those speeds on the stop seem really really crazy to me. 130 mph while coasting on the throttle stop? Not unless you turned the stop on at the 1/8 mile!

[Marc]

Originally Posted by Lenny5160

It doesn't really impact what you are trying to say, but those speeds on the stop seem really really crazy to me. 130 mph while coasting on the throttle stop? Not unless you turned the stop on at the 1/8 mile!

That had me confused as well. I don't remember exactly, but I believe my datalogger showed MPH on the stop at just over 60mph. And my cruise RPM is on the high side.

[gnicholson]

my car with a 4.88 and 32 inch tire shows about82 mph at 4200. drop to a 4.30 would be about 93 doing the basic rpm tire diameter gear ratio calculations. ofcourse thats with no convertor slippage so its actually less

[Lenny5160]

My completely uneducated guess would have been 40-60 mph for most cars.

[Ken MacNicol]

Mine is probably slower than that since my cruise is 3,600 rpm's

[voltdr]

Originally Posted by Lenny5160

It doesn't really impact what you are trying to say, but those speeds on the stop seem really really crazy to me. 130 mph while coasting on the throttle stop? Not unless you turned the stop on at the 1/8 mile!

I just picked a mph for my discussion. I have no idea what the stop mph is. Those numbers are probably more indicative of the 1/8 mile mph. Just saying that if you start at a slower mph but have a longer time to get to the finish, versus a higher mph but shorter time to get to the finish... Will it change the finish mph much?
Dan

[Lenny5160]

Originally Posted by voltdr

I just picked a mph for my discussion. I have no idea what the stop mph is. Those numbers are probably more indicative of the 1/8 mile mph. Just saying that if you start at a slower mph but have a longer time to get to the finish, versus a higher mph but shorter time to get to the finish... Will it change the finish mph much?
Dan

Of course it will change it. More time WOT will produce more MPH unless your engine has its tongue hanging out by the finish line. The definition of "much" is up for debate. Will it be enough to change the appearance of the race for you and your opponent? Probably not unless your timer or cruise RPM change is dramatic.

My dragster is mechanically injected, so I go on the stop at 0.100 and shut it down to a dead idle. My cruising speed is almost a stop. I also come off the stop in Low gear. I've never run this combination wide open to the 1/4 but I only lose 2-3 MPH at the 1/8 mile when running 8.90 on the stop as compared to a wide open pass. 6.19 @ 145.86 compared to 4.69 @ 148.14.

I would hazard a guess that cars running a more traditional cruise RPM and coming off the stop in High gear are down 10+ MPH at the 1/8 compared to a WOT run.

[Superstreet29]

I do know if you are low on power dropping that cruise rpm gets unpredictable. And if you make good power getting it too high puts too many numbers in the timer. It’s a test and tune fine tuning point til you find what works on your car. I’ve been on at .001 with a Maxspeed, on at .10 same carb...you just have to have enough power to do it that soon or it will know the breath out of it and you’ll get a dip. I had a big motor combo that liked .001 and shift at .020.at 4300 and it worked well. Tried it with a smaller motor and it was a no go

[Keith 944]

Originally Posted by Superstreet29

I do know if you are low on power dropping that cruise rpm gets unpredictable. And if you make good power getting it too high puts too many numbers in the timer. It’s a test and tune fine tuning point til you find what works on your car. I’ve been on at .001 with a Maxspeed, on at .10 same carb...you just have to have enough power to do it that soon or it will know the breath out of it and you’ll get a dip. I had a big motor combo that liked .001 and shift at .020.at 4300 and it worked well. Tried it with a smaller motor and it was a no go

^^^^ This
Every engine/combo is different. The key? Test, Test, and Test some more. The combo will show you what it likes, not the other way around...