Drag Racing Tech - Spinning will add mph?

I've heard it said that spinning your tires off the line will add mph to your time slip. Is there a limit to this? Wouldn't it start to subtract after a certain point?

As far as drag racing is concerned, MPH isn't nearly as important as ET.

Spinning your tires at launch could contribute to a higher MPH since the car tends to make up some of the lost ET with speed. A big speed and a slower ET usually mean the car lost traction at some point in the run. It's sort of a trade off.

To me, I'd take a lower ET over a bigger MPH any day. :)

When I switched to my MT Steet ETs before 14.145 @ 99.94 after 13.699 @ 96.73. I lost almost 3 MPH but gained .5 seconds. I'd take the .5 second anyday.

So as much as 3 mph can be gained through spinning, so far. Anyone else?

As far as drag racing is concerned, MPH isn't nearly as important as ET.

No doubt. I don't mean to say I'm TRYING to induce this condition, I just want to know for the purposes of interpreting time slips. If I see a high MPH, I want to know how much of it could be due to spinning.

Yeah, it's going to add mph, but your et is going to suck.

When you are under-geared or under-stalled, spinning helps trap speed by keeping the engine rpms closer to the powerband. A deadhook while under-geared or under-stalled will bog until the engine gets into the powerband.

With the right gear and stall, spinning will hurt trap speed. So, that explains why some say spinning helps and others say it hurts.

Yeah, it's going to add mph, but your et is going to suck.

Yes, yes, that is known. That's not the point of my question.

To a point, isn't trap speed independent of traction and dependant on horsepower? The reason you lose speed with slicks is they grow and distort so they reduce your gear ratio and "suck up" some hosepower. I doubt you can attribute all of that 3 mph loss to slicks, or attribute a 3 mph gain to spinning. I can see how dead hooking an undergeared car will hurt it, lol that's why ricers have to clutch dump their civics at 6k rpm, they make no power down low. But I don't think that spinning in more optimally geared car will decrease your trap speed. Taking out variables such as weather, shifting time, as long as you're at full throttle, you should run right around x trap speed all the time. Someone willing to try it at the track? :) Try a 6k clutch dump and then try a normal launch and see if the traps differ! This might be only for street tires though because I believe slicks are a little less consistent trap speed wise because of growth and such.

I tried it at the track. My street tires and my MT street radials are both 255/50R16. I have a 2800 stall and 3.73s.

As far as drag racing is concerned, MPH isn't nearly as important as ET.

Spinning your tires at launch could contribute to a higher MPH since the car tends to make up some of the lost ET with speed. A big speed and a slower ET usually mean the car lost traction at some point in the run. It's sort of a trade off.

To me, I'd take a lower ET over a bigger MPH any day. :)

Good call! MPH can be an indicator of hp, but at the same time, it's the e.t. that matters most. I've launched my auto at numerous different rpms, and the mph doesn't change too much. Keep in mind that the mph at the track is measured as the distance between the first timer box and the actual finish line (called the speed trap or why they use trap speed) traveled, and that's why it can higher/lower than what your actual speedometer reads.

Spinning at the line also keeps the rpm higher unless you lift, and that can sometimes help to avoid the bog referred to earlier, thus higher mph at times. Sticky tires and/or slicks can take away mph due to friction, contact patch and the flexible sidewalls versus a street radial, but it can be a lot or very little, if anything. My Nova will MPH within .20 when swapping between my 275/60/15 std radials and my 28 x 11.5 x 15 ET Streets (actual measurement is 27.5 x 8.9).

Derek

The purpose here is measurement of a car's power output via it's mph. I'd like to know how much this can be distorted by "spinning off the line."

Good call! MPH can be an indicator of hp, but at the same time, it's the e.t. that matters most. I've launched my auto at numerous different rpms, and the mph doesn't change too much. Keep in mind that the mph at the track is measured as the distance between the first timer box and the actual finish line (called the speed trap or why they use trap speed) traveled, and that's why it can higher/lower than what your actual speedometer reads.

Spinning at the line also keeps the rpm higher unless you lift, and that can sometimes help to avoid the bog referred to earlier, thus higher mph at times. Sticky tires and/or slicks can take away mph due to friction, contact patch and the flexible sidewalls versus a street radial, but it can be a lot or very little, if anything. My Nova will MPH within .20 when swapping between my 275/60/15 std radials and my 28 x 11.5 x 15 ET Streets (actual measurement is 27.5 x 8.9).

Derek

What is you 60 ft times both ways?

This guy runs a 8.068 at only 97.89 mph! So I suspect in this case spinning the tires caused him to lose MPH. And ET.

I only mention this to show there is no real way to tell if spinning the tires adds mph in a 1/4 mile run. If you spin them all the way through you will lose mph.

Right Lane: John Force Runs 8.068/97.89 mph

ENNIS, Texas - DALLAS - Notes from round 3 qualifying in Funny Car at the NHRA POWERade Drag Racing Series, 20th annual O'Reilly NHRA Fall Nationals presented by Castrol Syntec listing lane, driver name, elapsed time/top speed this round, position in order following run, best prior elapsed time/speed, and position in order prior to run:

What is you 60 ft times both ways?

1.716 on street tires, 1.576 on the ET Streets.

Derek

This guy runs a 8.068 at only 97.89 mph! So I suspect in this case spinning the tires caused him to lose MPH. And ET.

I only mention this to show there is no real way to tell if spinning the tires adds mph in a 1/4 mile run. If you spin them all the way through you will lose mph.

Right Lane: John Force Runs 8.068/97.89 mph

ENNIS, Texas - DALLAS - Notes from round 3 qualifying in Funny Car at the NHRA POWERade Drag Racing Series, 20th annual O'Reilly NHRA Fall Nationals presented by Castrol Syntec listing lane, driver name, elapsed time/top speed this round, position in order following run, best prior elapsed time/speed, and position in order prior to run:

I don't think we can introduce a Funny Car pass to the argument... :lol:

When you are under-geared or under-stalled, spinning helps trap speed by keeping the engine rpms closer to the powerband. A deadhook while under-geared or under-stalled will bog until the engine gets into the powerband.

With the right gear and stall, spinning will hurt trap speed. So, that explains why some say spinning helps and others say it hurts.

couldn't have said it better myself. most 6 speeds, spinning increases the mph alot wheras stalled autos (like mine) i actually loose 1-2mph if i get a 1.9 or higher 60ft (from spinning). also sometimes the car spins a little then hooks HARD which throws the car forward and gives you some extra momentum/mph. i think everybody with drag radials have experienced this.

There's really no limit on how much mph you can gain or ET you can lose from spinning. Look at some of the faster FWDs at the track. It's not uncommon to see a fast Honda running a 13.0@125 or something.

There's really no limit on how much mph you can gain or ET you can lose from spinning. Look at some of the faster FWDs at the track. It's not uncommon to see a fast Honda running a 13.0@125 or something.

Ah, but does MPH still indicate power? If I took the same car and threw crappy tires on it so that they would spin, would there be *no limit* to the amount of MPH that would be added?

Or did you just mean to say that there is no limit to the amount of spread between ET's and MPH's?

PLEASE feel free to use me as an example!!!!
Everyone tells me my car is slow for the mods. So feel free to tear me up, I know I can't launch.
I am running 12.8 @ 112 MPH
I either launch slow , or I spin through second feathering the gas, on street tires
close 1/4 results in times. 60' is 1.9 to 2.2 average. Now, my friend got 12.1 @ 110 MPH. OK we are both confused, so be both decided to be the winner and drink to ourselves....LMAO :cheers:
PS worst part is ...I built his car 383 blown vette....nothing like beating yourself :(

black knight
I rely on trap speed mph to measure performance gains from mods that I have done. It works reliably when used this way. But I shouldn't use my trap speed in comparison with somebody else's to draw a power similarity, because trap speed is also affected by weight, transmission efficiency, shift-points, etc. However, between similar cars and setups, mph should give you a pretty good ballpark indication of how well each car is putting down whatever power they are making.

For me, trap speeds usually don't vary greatly between runs when I hook or spin lightly. It is usually within a 1 mph range. When I was near stock, spinning a little bit helped not only mph but sometimes ET as well. If I spun too much, both ET and mph suffered. So you can't assume that more spin will make higher mph. I think there is a fine line to be drawn on the amount of spin to see benefit vs. mph lost.

From what I understand you gain MPH when you spin off the line because you cover little distance when spinning, while still gaining RPMs and have more distance to make up with while your still making up power, gearing, RPMs.