I am wondering if anyone has done testing here to measure the impact of adding or removing 100lbs in ultimate lap time in a higher speed track environment. I'm a racer and mechanical engineer by education, understand physics, of course removing the weight for all the obvious reasons will make the car quicker. But can anyone here offer any real world data of their own in this Chassis Weight Range and Speed Range? Assume a typical 15 corner roadcourse, with 3 long acceleration zones, 5 corners with cornering speeds in the 70-80mph or so range, lots of elevation change, a high speed banked 100+ mph corner, and 115mph braking zone down to 45mph or so. (My specific example is a Showroom Stock 1994 BMW 325 I, on R6's, at New Hampshire International Speedway Road Course in case you are curious.)

So has anyone tested the impact on their lap time in back to back sessions by adding or removing signficant amounts of weight? What was the result?

I have a lot of experience as to the impact of weight in autocross speeds/environment. In one example, another 200lb passenger in an NA miata was around 2 seconds, with 55mph max cornering speeds. But of course, the impact on weight in cornering speeds goes up as the cornering speed goes up (it's physics). F1 cars are on the order of 5-7 seconds slower in full fuel trim (an 800 hp car in a 1200lbs chassis) with tremendously high cornering speeds. I have personally logged lap times at a local go kart track, and with almost freakish clarity of results, adding 10lbs to a 6hp indoor go kart was worth just over 1 tenth of a second on a 36 second track, with ~25-30mph cornering speeds.

All data points in different environments. So what say you? Can anyone share their data for ultimate lap time impact by removing around 100lbs in a ~3000lb car in a typical road course level of speed environment?

My thanks in advance.

Very Best,

Nick

 

I suspect the difference between 3100 and 3000 pounds is less than the lap to lap variation of a non-pro driver, i.e. impossible to detect under most any circumstances.

I suppose if you had a enough laps under similar weather conditions, not limited by traffic and ignore the effects of tire wear and changing fuel load... at both weights, perhaps then if there is a difference, it may be due to the weight savings.

 

where you remove that weight has more bearing than simply removing 100lb for the sake of removing 100lb.

 

Well, we're talking about great drivers here extracting near 100% of the car, no doubt about that. I understand the common "Within the lap variation stance" and everything else you mention. But, I am inclined to disagree that 100lbs, even on a 3000lb car at "at limit" cornering speeds is neglible. Whether it is a few tenths on an ~80 second track, or more than half a second is really the question. I am just wondering if anyone here as logged lap times to put a rough order of magnitude number to it.

 

weight reduction is weight reduction. It is always going to make a difference, whether or not you notice is a different story. If you are not extremely comfortable with oversteer, I would not recommend removing from the rear of the vehicle.

 

Yes, I understand that, that's not what I'm asking. I'm wondering if anyone has datalogged the impact of 100 lbs weight reduction in a 3000lb car in a track environment. Hopefully some of the more track oriented/time attack folks can share their data. Billy Johnson, Krazik, where are you guys? I want to hear from you on this.

Thanks,

Nick

 

PM MrSideways.

 

Will do, thanks -

 

Wonder if people have logged laps on the same day with and without passengers. That'd be a pretty close approximation.

 

Personally, I'm around ~3.5% faster (lap times) without a 200 lb. passenger (~ 2850 to 2650 lbs.) at VIR. Same conditions, very consistent, and recorded with a DL1 data logger. You gain time everywhere. As Colin Chapman said, "Adding power makes you faster on the straights. Subtracting weight makes you faster everywhere."