[sickem]

So I'm not very knowledgable about the linkage between whp and quarter mile traps and ET's and I'm sure this a debate that rages on every car forum since their inception. But my buddy is an avid bracket racer with a highly modded NA C5 vette that traps in the 124mph range with 11.1 ET deep stage. He is calling BS on all the E85 protune dyno numbers that are >400 rwhp based on the mid to high 11 second ETs, even higher in some cases. (I've seen some in the 420 whp range.) His argument is that HP is HP so these cars really should be running low 11s, hence the dyno numbers are inaccurate. What rebuttal am I missing here? I mean I thought that the trap speeds the protuners are getting in the 120s is sufficient to prove the hp, but I guess not. I'm trying to learn something out of this exchange so I welcome a lively discussion. Thanks.

[foghat]

Well. Horsepower is horsepower. But weight is also weight. Gearing comes into play as well. As does traction when you are talking about the et.

Every 1/4 mile calculator I've seen, 400 hp and ~3500-3600lbs (with driver) = 12 sec 1/4 mile. this has pretty much been confirmed by multiple time slips. No way you are running low 11's in a 335i with 400hp.

[pits200]

Originally Posted by sickem

So I'm not very knowledgable about the linkage between whp and quarter mile traps and ET's and I'm sure this a debate that rages on every car forum since their inception. But my buddy is an avid bracket racer with a highly modded NA C5 vette that traps in the 124mph range with 11.1 ET deep stage. He is calling BS on all the E85 protune dyno numbers that are >400 rwhp based on the mid to high 11 second ETs, even higher in some cases. (I've seen some in the 420 whp range.) His argument is that HP is HP so these cars really should be running low 11s, hence the dyno numbers are inaccurate. What rebuttal am I missing here? I mean I thought that the trap speeds the protuners are getting in the 120s is sufficient to prove the hp, but I guess not. I'm trying to learn something out of this exchange so I welcome a lively discussion. Thanks.

That his C5 is about 400lbs lighter than the 335. Hp is hp but weight needs to be taken into account when looking to determine 1/4 mile times based off whp.

[Jeff@TopGearSolutions]

Drag co-efficient. Gearing. Torque. Powerband. All factor in as well as many others.

ET calculators are just another way to guess. Launching a car, working with traction, and other factors are different in the real world.

[sickem]

Yeah I mean I agree guys I'm just trying to understand why a guy who has so much experience / knowledge drag racing is being so myopic. Obviously the two dozen or so protuned independent dynos are all wrong and he's right lol

[biz77]

Originally Posted by sickem

So I'm not very knowledgable about the linkage between whp and quarter mile traps and ET's and I'm sure this a debate that rages on every car forum since their inception. But my buddy is an avid bracket racer with a highly modded NA C5 vette that traps in the 124mph range with 11.1 ET deep stage. He is calling BS on all the E85 protune dyno numbers that are >400 rwhp based on the mid to high 11 second ETs, even higher in some cases. (I've seen some in the 420 whp range.) His argument is that HP is HP so these cars really should be running low 11s, hence the dyno numbers are inaccurate. What rebuttal am I missing here? I mean I thought that the trap speeds the protuners are getting in the 120s is sufficient to prove the hp, but I guess not. I'm trying to learn something out of this exchange so I welcome a lively discussion. Thanks.

You are correct. Trap speed is a much better indicator of horsepower than ET is. Ask your Vette driver what his 60 foot time is. I'm guessing he runs slicks? Ask him what he thinks his 60 foot time might be on normal street tires. Ask him what that change in 60 foot time would do to his overall ET.

Each .1 in the 60 foot is worth at least .2 at the end of the track. Take a 12.00 second car that pulls 2.0 60' times on street tires and put drag radials on it to cut 60' times down to 1.6 and you now have a low 11-second car.

[foghat]

I mean, doesn't a stock z06 put down about 440ish to the wheels? Don't they run high 11's stock. I honestly have no idea how your friend thinks 400whp is going to translate to low 11s. If he is running that fast, I suspect he has more power than he thinks or has some sort of mad traction.

[sickem]

I mean stock F10 M5s are running 11.8 @ 119 and weighs about 500 lbs more than a 3er. I asked him to explain that one and he got pissed

[Jeff@TopGearSolutions]

Originally Posted by biz77

You are correct. Trap speed is a much better indicator of horsepower than ET is. Ask your Vette driver what his 60 foot time is. I'm guessing he runs slicks? Ask him what he thinks his 60 foot time might be on normal street tires. Ask him what that change in 60 foot time would do to his overall ET.

Each .1 in the 60 foot is worth at least .2 at the end of the track. Take a 12.00 second car that pulls 2.0 60' times on street tires and put drag radials on it to cut 60' times down to 1.6 and you now have a low 11-second car.

Originally Posted by foghat

I mean, doesn't a stock z06 put down about 440ish to the wheels? Don't they run high 11's stock. I honestly have no idea how your friend thinks 400whp is going to translate to low 11s. If he is running that fast, I suspect he has more power than he thinks or has some sort of mad traction.

Little over 440ish. With an EXCELLENT driver they can run in the high 11's.

I have a few mods in mine and I still doubt I can run high 11's first time out. The car has it in it, but it's hard to dial all that into a car between the perfect launch and the perfect shifting. Not to mention track prep and DA.

[BMWM.D.]

Originally Posted by sickem

Yeah I mean I agree guys I'm just trying to understand why a guy who has so much experience / knowledge drag racing is being so myopic. Obviously the two dozen or so protuned independent dynos are all wrong and he's right lol

It's mainly that most of these N54 cars have pretty poor 60' times and are running stock run-flats (much smaller width than a Vette), or regular street tires. I also have a well modded C6, and most guys I know who drag race on a regular basis have a good set of drag radials, and usually a high-stall converter on automatic cars. Not the case with these BMWs. I suspect a lot of these N54 cars still have the factory open-diff as well.

For what it's worth, a stock LS3 Corvette dynos at around 375-390 rwhp (436 crank rating), is ~300 lbs lighter than an E90 335i, and run ~12.5 @ 115-116 stock. I think the N54 cars are doing just fine based on the lack of traction mods most have. The formula I've always used is 100 lbs = 10 hp/10tq. So a ~400 rwhp 335i should run similar trap speeds to a ~370 rwhp LS3 C6. ET is going to depend heavily on traction and 60' times.

[andrew1182]

Three letters explain the majority of the difference.

LSD...not the trippy kind, the grippy kind.

We're basically running open diffs. Old school drag racing rule of thumb is every 1/10th of a second for the 60' is worth 2/10th's on the 1/4 mile time. A well set up C5 (with some balls) on an ET Street radial should be cutting 1.4-1.6 60 ft times. Do the math. If high hp N54 cars were cutting those 60' times where would they be?

PS: I've had done my time with LS based engines and your friends C5 is FAR from heavily modded if he's trapping 125mph. He's probably got heads, cam, bolt-ons running those traps. Vette guys shouldn't be able to talk until they break into the 130's, LoL.

[sickem]

Originally Posted by andrew1182

Three letters explain the majority of the difference.

LSD...not the trippy kind, the grippy kind.

We're basically running open diffs. Old school drag racing rule of thumb is every 1/10th of a second for the 60' is worth 2/10th's on the 1/4 mile time. A well set up C5 (with some balls) on an ET Street radial should be cutting 1.4-1.6 60 ft times. Do the math. If high hp N54 cars were cutting those 60' times where would they be?

PS: I've had done my time with LS based engines and your friends C5 is FAR from heavily modded if he's trapping 125mph. He's probably got heads, cam, bolt-ons running those traps. Vette guys shouldn't be able to talk until they break into the 130's, LoL.

when I say heavily modded I mean lots of upgraded internals, all the bolt-ons, and also non-stock rear end, TC, and tranny. he's into bracket racing so he's not into forced induction and making the car really any faster than it is. That motor the way it was pretty much maxed out without putting a huffer on it. anyway point isn't about his car but just about me understanding the link between wheel hp and drag data. thank you to everyone for the input.

[BQTuning]

Not many BMW owners in general take their cars to the drag strip. There is only a minority that know how to make these cars perform on the strip

Being that said, in general, a 2.0 60" + speed trap can give good accuracy of what an N54 is putting down depending on the transmission type

If you can break 11s with at least 2.0 60" and high trap speed then you are hauling azz

[ASAP]

Originally Posted by BuraQ

Not many BMW owners in general take their cars to the drag strip. There is only a minority that know how to make these cars perform on the strip

Being that said, in general, a 2.0 60" + speed trap can give good accuracy of what an N54 is putting down depending on the transmission type

If you can break 11s with at least 2.0 60" and high trap speed then you are hauling azz

1.946 on my 12.0 run on hankraps

[BMWM.D.]

Originally Posted by sickem

when I say heavily modded I mean lots of upgraded internals, all the bolt-ons, and also non-stock rear end, TC, and tranny. he's into bracket racing so he's not into forced induction and making the car really any faster than it is. That motor the way it was pretty much maxed out without putting a huffer on it. anyway point isn't about his car but just about me understanding the link between wheel hp and drag data. thank you to everyone for the input.

Pretty much what I thought. This is a fully prepped bracket car -- meaning it has the suspension and traction necessary to launch hard and consistent. A C5/C6 making decent power, a high-stall converter and M/T or Hoosiers is going to be worlds better when talking 1/4 mile ET. He's probably knocking down ~1.6 60's or better, right?

But there really isn't any link between wheel HP and ET. Trap speed definitely has a relationship with RWHP on a given platform. Trap speed is what I use to decide if a car is really making power.

[sickem]

Yeah my best 60' is also on hankooks 2.00? I think he cuts like 1.4x or something ridonkulous