Torque - A Real World Example

[Ron Earp]

We have two cars, Car1 and Car2. Attached below are the actual dyno plots for Car1 and Car2. The dyno plots were taken on the same day and on the same dyno that is always used to dyno Car1 and Car2. I apologize that Car1's sheet is in ASCII data format from the dyno but it is the real deal.

Some particulars:

*Car1 has peak rear wheel torque value of 197 ft lbs @ 3350 RPM
*Car1 has peak rear wheel hp of 156 hp @ 4600 RPM

*Car2 has peak rear wheel torque value of 160 ft lbs @ 5100 RPM
*Car2 has peak rear wheel hp of 168 hp @ 5900 RPM

*In race trim Car1 routinely crosses the scales at 2650 lbs (40 lbs heavy), Car2 at 2590 lbs (100 lbs heavy).

As you can see Car1 has almost 40 ft lbs more rear wheel torque than Car2, or 20% more. Car1 also has a wider RPM spread between the horsepower and torque peaks. Car2 has a narrow RPM spread between the horsepower and torque peaks.

Both cars have a strut front suspension. Both cars have solid (no, not vented kiddies, I said solid) front discs and rear drum brakes. Car1 has a solid rear axle, Car2 has an IRS.

Questions:
How do you suspect these cars race based on the specifications?
How do you suspect they race in the real world, driver independent?
Should Car1 get a torque adder?
Should Car2 get a weight break?

Discuss.

Car1 Dynojet Data
http://www.gt40s.com/images/misc/car1.jpg

Car2 Dynojet Plots
http://www.gt40s.com/images/misc/car2.jpg

[GKR_17]

Good post Ron,

I think this will help show the V-8's (which includes car 1!) are not as superior as many think. Notice car 2 has roughly a 1800 RPM range (5000-6800) where the power is above 150, while car 1 only exceeds 150 for an RPM range of about 1000 (4250-5250). Clearly car 2 will win in most cases. Maybe availablitly is an issue (car 1 is pretty rare), but you see a lot of car 2 on the track, and very few car 1.

Grafton

[Chip42]

car1... that's a lot of torque - and for 2000 RPM it's over the peak of car2. gear the thing right, and it oculd be a very real threat, a true rocketship out of the corners, assuming it can hook up. no matter what, it's a one-trick pony, and if the track doesn't suit it, it will likely not impress.

car 2 has that "drivability" factor going for it - long, flat curves mean you can use it in a lot of different ways, and the peaks are the sort of arangement we look for - some might opt for a bit more torwque, others for more HP and a higher redline, but for an IT motor, these are very good looking curves. I would presume this car to be the better all around racer, particularly with regard to car1.

given the brakes as described, though, I wouldn't choose either one - over race length heat will kill their lap times and thus they can't really be contenders, anyhow.

btw - "car3" is missing, it's the one with a dynoplot that looks like car1, swapping HP and torque and mirrored, redlinning around 8k. that car comes accross the scales ~5lbs heavy, has IRS, solid rear disks, vented front disks. anywhere but an autocross, that's the one I want.

[Andy Bettencourt]

What if the car with more torque was almost 200lbs lighter?

I just refuse to compare cars when you don't know the weights. The point is that higher hp cars pay a weight penalty in weight up front.

[Ron Earp]

I just refuse to compare cars when you don't know the weights.

??? Weights were provided.

[Andy Bettencourt]

??? Weights were provided.

Ya, but those aren't the weights that should be quoted IMHO when 'chosing' a between the two. There should be 200lbs difference given the power.

[Ron Earp]

Ya, but those aren't the weights that should be quoted IMHO when 'chosing' a between the two. There should be 200lbs difference given the power.

The Car1 and Car2 in this thread have nothing to do with the other thread.

[Knestis]

What the cars in question "should" weigh is a function of their stock HP - at least so far as their base spec weight is concerned. Remember that the point of these complicated conversations is to clarify the process for establishing that process.

I'm cross posting but context needs to be set on a couple of points...

** Remember that the ITAC generally won't have IT-prepared dyno sheets when setting specifications.

** You provide "real world" as-raced weights relative to the current established IT weights. It's possible that those weights were determined under different regimes.

** We have NO mechanism for applying "how they race" in the classification/specification process for individual cars, and (again, sorry I sound like a broken record on this) we don't think the membership wants us to...

Ron's asking informative questions but they are about how IT-spec dyno results translate into "raceability" and drivers' individual preferences. It's remotely - but ONLY remotely - related to the questions of if, and if so how, torque should be applied to specification practices.

K

[wrcRS]

Just going off of the Diesel prototype cars (i.e. R8 vs. R10,) there is not much difference between "quick" lap times. There is however, many differences between race pace and consistency over the run.

The two differ in torque by somewhere in the 400lb/ft range with similiar HP #'s. Im not sure about weight but they can't be that much different.