IcemanG17

Okay lets say you are building a car for a certain power-weight racing class. I would guess thats is better to have a lighter less powerful car for a given power-weight ratio, lets say 15.0-1 than a heavier more powerful car with the same ratio?

My thinking is the lighter less powerful car will be easier to drive, burn through less tires and brakes with better fuel economy than the heavier car?

So here is the ??? Gut the car to the bones, then install ballast to make weight since you can put the weight exactly where you want it (sorta anyway) then tune down the engine if you have too? That seems like the plan to me?

Thoughts-opinions?

C.J. Ichiban

generally it's HP they limit, not TQ- so factor that as well if you're tuning anything.

but- the first thing you do for NASA as it's a HP/weight thing...get a great braking system/ suspension and awesome tires. you can gain SO MUCH in a semi-spec class with the right handling platform...also- know what everyone else is racing. if they've all got HP beasts then you're probably gonna get drag-raced after each slow corner.

bobt993

Brian, If your looking to be at the front of a certain race series eg NASA GTS (which uses hp/wght ratio) then look at the results in the class you want to target for the tracks you drive. The front runners have already figured out the best ballance. The challenge is you want both............ A car you can ballast a little more or less with an engine you can run with or without HP/TQ gains for the track that it is best on. If someone has hp on you then they are going to be a serious threat at the starts and long straights as mentioned above. If you get tangled with another car running the opposite scenario as you then each of you kills the other's lap time.

If your thinking maintenance and less expense then lighter car will use less consumables and be more consistent in the long races.

disasterman

In NASA, torque is taken into account, add torque and HP then divide by two. Where you make the power is the key. Don't forget about getting that power to the ground - gear ratios.

good hands

On the faster tracks I race on such as VIR the M3'S kick my *** with the higher horsepwower and their 300lbs of ballast ( in some cases ) where top end speed is desired. But when I come home to Summit point I have been much more competitive with my lighter car with less HP. I have a friend who was racing his 911 in GTS 3, got his car down to 2200 lbs and was doing OK but said he got tired of being passed on the straightaways by heavier more powerful cars so he bought an E46 M3 and sold the 911. To answer your question I would start with a more powerful car with gobs of torque as opposed to lighter more nimble car. That being said I'd rather push a Porsche than drive a Bimmer

Lemming

Only true if Torque is greater than wHP, otherwise just wHP.

I agree with what's been said above, if you want to run as cheap as possible, go light, everything lasts longer. My car was very light with low HP (but on the extreme lower edge of my wt/hp class). Although I could run the lap times of the others, when you get into traffic the low HP can hinder your progress.

jakermc

This is only true if max torque is above max hp, otherwise it's a staight hp calc.

Where the power is critical, a flat torque curve and short gears help.

As CJ mentioned, the big gains here are through suspension and handling. A newer chassis pays big dividends here. No offense to the air cooled guys (I race one myself) but the 996 chassis really shines here.

MelanomaMan

Interesting thread Brian. I echo Scott's comments. I'm not as competitive as most of the M3's in our region for NASA, but have a lot of fun just the same. (2500 lbs w/driver, 215 hp 3.2l) I chose the 911 platform because I wanted to learn how to drive it well. Since we don't have the GTS class in AZ I run PTA during the year, and will run GTS3 for nationals this fall. Short tracks are no problem but when we run the longer tracks like MMP or Willow the higher hp/tq walk away from me. Fortunately we have a really fun class of 5-6 of us here that finish within .5 seconds in almost every race.

+1 for doing your homework on your competition beforehand.

Bryan Watts

I prefer to lean towards the power side of the equation. I can tune the suspension around weight, but more power = a better racing car. It's easy to keep someone behind you in the corners in a slower car, but it's impossible to "block" a faster car on the straights. A heavier, more powerful car, is a better car to race versus a lighter, less powerful car IMO. I've raced GT3RSR's a few times that were slower in the corners (driver), but powered away on the straights...even if I somehow managed to squeeze a pass into a braking zone, they always powered back by eventually.

And don't forget about the importance of power for getting around traffic and other, out of class, cars that might be on track with you. Putting a slower car between you and your competitor at the end of a straight can do wonders for making up for any handling deficiencies you are giving up to the lighter car.

For qualifying laps on a wide open track, I'll would less power and less weight. If I'm actually racing, and running in traffic, I'll take the more powerful car almost everytime.

Here's a good battle between two pretty "optimized" GT4 cars from a power/weight standpoint. I'm in the heavier, more powerful M3 camera car and Derek Schwarz is in a much lighter, less powerful 911:
Part 1: http://www.vimeo.com/5810776
Part 2: http://www.vimeo.com/5815391

We have a pretty good race. You can see where the lighter car has an advantage and you can see where the heavier car has an advantage in different places around the track. With some more time on R-comps, tuning the suspension (we just strapped them on with our slicks setup in order to meet GTS4 rules), I think I could make the heavier car dominate the lighter car. Ultimately, one car wins on the final lap.

Bull993tt

Whats up Bryan? This is about as good as a comparison as you can get for this thread. One of my most exciting races I ever had to date.

FYI Bryan... I am out of GTS4 now and in GTS5. I had Peter Dawe build me a 3.8L which I just had my first session in the car at the Glen last weekend with PCA. I was able to get into 1:59's on Sunday, but think the car has another 2+ seconds in it once I learn how to re-drive the car. It is very different now being that I am on slicks and not DOT's and everything is happening a whole lot faster now...

Hope to see you soon and I hope all is well with you.

Bryan Watts

Derek - Heard about your jump to GTS5 from some GTS4 competitors (Max) who were glad to see you go.

The economy is forcing us into a little break from racing this year it seems. The good news about our car is that we can hop back and forth from GTS4-GTS5 depending on who shows up to have the best time (or win the most tires ). Unfortunately, we're not very close to being maxed out for GTS5, but your laptimes at Watkins sound like we could have a pretty good race. Laptimes at Watkins and VIR seem to be almost exactly the same for various cars I've driven and compared over the years.

CAM14

On a momentum track with limited straights and limited high speed, then the light weight will have an advantage, but if longer straights, sustained inclines, or general high speed stretches, then higher HP will have an advantage. Personal Opinion, I enjoy racing my lighter weight with less power spec class car in SCCA and NASA because the car is more agile in corners and generally more fun but very difficult to pass a heaver higher HP car unless the other car makes a mistake. Lap times are nearly identical, we just go about it slightly differently.

Bryan Watts

Advantage in lap times, but I would still argue that the heavier car would make the better RACE car (i.e. the better car for winning a race with) on almost any track. It's always easier to pass between corners than it is to pass in the corners, and vice-versa.

claykos

As others have said - the higher hp, heavier car is going to win in a race. Maybe not in qualifying, but in a race.

Especially at higher speed tracks, HP/Drag dominates acceleration.

I have a lot of experience racing on the lower weight, lower hp side against some heavy, very high hp cars. I raced a 240 hp, 2500 lb car in NASA ST2 and now race a 350 rwhp, 2500 lb car in ST1.

I raced at Cal Speedway in my ST1 car last year, and while I was on pole for the race I got blitzed at the start by the 3200+ lb, 550+ rwhp vipers and vettes. I was able to work my way back by and ended up winning the race, but they had such a huge advantage on the straights. The Oval turn actually helped a lot because I was able to go flat out and carry 155+ mph all the way around this corner (flat out from the straightaway) whereas the vettes/vipers would approach this corner at 170+ and then slow down to 140. On a track with a pure "straight" without the oval corner in the middle I would have been hosed.

mark kibort

I actually had a hand in setting that rule for GTS, and the reasoning was, that higher torque than HP engines, generally have a flatter HP curve, which can be a huge advange, and basically give you more average HP over your gear range. However, the opposite is not true, so thats the reasoning for the rule.