High trap speeds are an indication of the power being made. As you increase vehicle power output, Trap speed should increase. All things being equal. Generally speaking it takes 10-15 hp to add every additional mph. If a vehicle exhibits high trap speeds but a comparatively bad E.T. is generally an indication of bad traction or launch.

Some vehicles will have a great E.T. but a relatively slow mph. Usually this happens with a very light weight vehicle that is not making as much power as a heavy vehicle that runs the same E.T. since it takes less horsepower to move the lighter car, gearing, higher stall speeds on autos, better traction, weight transfer and a few other variables can affect this.

An example of quick E.T.'s but slow mph would be junior Dragsters that can run high 7 second 1/8 passes but only make speeds around 75-80 mph. A stock SRT 8 on the same track can run low 8's but trap 87-89 mph!

 

A high trap speed with low ET usually means you were spinning

Not sure if there a such thing as a "low trap speed" with good (quick) ET

 

Not sure if there a such thing as a "low trap speed" with good (quick) ET

Refer to Deathstar's explanation above...

 

The 392 A5 with DRs, tune, and mild bolt-ons is a great example of a great ET with a relatively low trap speed. The fact this 4200 lb car can run about 12 flat in decent air almost defies logic, particularly since it's typically only trapping around 113 MPH. Normally that ET is associated with a much higher trap speed - more like 118 MPH.

Just goes to demonstrate the efficiency of the TQ converter and auto trans, and also highlights the broad TQ curve of the 392. A 1.7x short time is amazing for that weight car with a 3.06 diff.

 

This is an interesting example to bring up! Do you think rising air drag at >100 mph speeds on the Challenger body is taking its toll on the trap speed? I guess this could be hit or miss, because I'm sure there are lots of examples of other cars that punch through the air with less than stellar aerodynamics, too?

Do you know if the 392 A5 gets into 4th by the end of the run at 113 mph, or is it still winding out 3rd?

 

Also note the Hellcat trap speeds for the OE tire and DR runs was almost the same - within 1 MPH. But the ET was 4 tenths apart. And that was with a very street-oriented DR which audibly/visibly spun on the launch (that's 2 tenths lost right there).

Wait until someone bolts a set of slicks to the Hellcat and really nails the holeshot with zero spin. I predict that ultra short 1st gear will result in a 1.5x short time and 10.4-10.5 in decent air.

 

Great explanation...thanks!

 

It's still in third but closing in on redline. Just another reason the 392 and A5 is a pretty sweet set up on the drag strip.

 

Could it make it to 118 mph in 3rd, you think, or would it have to go to 4th to reach that speed?

 

Yes I think so. I have been 117.79 to 117.85mph a few times at two different tracks. Always shifts to after the 1/4 traps.

 

I hit 117.4 in third with 26" DRs between 6650 and 6680 RPM. Oddly enough that wasn't my quickest ET as I had some slippage with a 1.82 60'. Air was awesome but the traction wasn't...

 

Here is a great example of lower et and a slow trap speed.
A friend runs a modded, somewhat beater 63 vetted with drag radials.
He has run a 12.8x on his best pass but never has trapped faster
Then 101mph. My best is a 12.9x and I consistently 110 mph

 

Wow, KJ...you are running the willy's outta that engine!

 

Yeah Dave at B&G got me hooked up with a good tune for shorter DRs. 6680 is as high as I have seen it.
I've been running 28" DRs lately and they are .1 slower as I'm only getting to about 6K in third in the traps.
28" for bracket racing as they hook awesome and are consistent. 26" for grudge racing and hero runs.
A 3.23 or 3.53 rear with 28 DRs would be optimum... I achieve the same result with the shorter DRs (26”) but lately the 392 is toasting the 275/40s so it’s time to try the 305/35 Hoosiers.

 

My 09 supercharged trapped no better than 112mph but a pretty decent 12.1 ET, that's with a 1.8 60 ft. as well on street tires. Magnacharged AWD RT Charger, 6 psi. I attribute most of the power was off the line and up to the 8th mile mark, past that, the weight was evident though a 112mph isn't bad and I was running a measly 6 psi. It made what.. 420AWHP maybe as low as 400??