When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
400 lbs is more weight than most humans can lose lol.
I think 400 lbs is wishful thinking for this platform, hence my question above about sharing of chassis. The RCF is only 200lbs
heavier than a RC350 F Sport RWD (3748). Not bad considering the RCF has V8, bigger wheels and tires, bigger brakes, probably bigger exhaust, TVD, etc. The IS350 F Sport is 3600lbs as a reference, so I guess Lexus make heavy cars like Mercedes. it's been my experience that coupes are heavier than sedans due to extra bracing in doors due to lack of b pillar
The IS350 F-Sport is actually in the 37XX lbs ballpark.
Lightweight wheels and performance tires that can shed weight that is not just static weight. Since the wheels/tires have rotational mass, it actually has an exponential effect in reducing rotational inertia when the tire is rotating. For example, a 12 lbs loss in all four corners will not give a net effect of 12 lbs loss, but a much greater compounding effect since that is 12 lbs of rotational inertia the faster the wheel rotates. So at the high-revs, the engine response will increase dramatically with lightweight wheels. It will give the illusion of the car suddenly shedding a couple of hundred pounds.
It will have a similar effect to a lightened flywheel which increases what they call "virtual torque" in the mid range and high rpm at the expense of a bit on/off behavior at low revs.
Originally Posted by Deanrcf
I think 400 lbs is wishful thinking for this platform, hence my question above about sharing of chassis. The RCF is only 200lbs
heavier than a RC350 F Sport RWD (3748). Not bad considering the RCF has V8, bigger wheels and tires, bigger brakes, probably bigger exhaust, TVD, etc. The IS350 F Sport is 3600lbs as a reference, so I guess Lexus make heavy cars like Mercedes. it's been my experience that coupes are heavier than sedans due to extra bracing in doors due to lack of b pillar
The IS350 F-Sport is actually in the 37XX lbs ballpark.
Lightweight wheels and performance tires that can shed weight that is not just static weight. Since the wheels/tires have rotational mass, it actually has an exponential effect in reducing rotational inertia when the tire is rotating. For example, a 12 lbs loss in all four corners will not give a net effect of 12 lbs loss, but a much greater compounding effect since that is 12 lbs of rotational inertia the faster the wheel rotates. So at the high-revs, the engine response will increase dramatically with lightweight wheels. It will give the illusion of the car suddenly shedding a couple of hundred pounds.
It will have a similar effect to a lightened flywheel which increases what they call "virtual torque" in the mid range and high rpm at the expense of a bit on/off behavior at low revs.
The 37xx lbs for the IS350 was a typo on their website as that is the weight of their AWD version. The corrected spec sheet reads 3593 lbs for the RWD version. Hard to believe there is such a large difference in weight between the two platforms...
The IS350 F-Sport is actually in the 37XX lbs ballpark.
Lightweight wheels and performance tires that can shed weight that is not just static weight. Since the wheels/tires have rotational mass, it actually has an exponential effect in reducing rotational inertia when the tire is rotating. For example, a 12 lbs loss in all four corners will not give a net effect of 12 lbs loss, but a much greater compounding effect since that is 12 lbs of rotational inertia the faster the wheel rotates. So at the high-revs, the engine response will increase dramatically with lightweight wheels. It will give the illusion of the car suddenly shedding a couple of hundred pounds.
It will have a similar effect to a lightened flywheel which increases what they call "virtual torque" in the mid range and high rpm at the expense of a bit on/off behavior at low revs.
You are correct, Sir. I learned this from the G35 camp. While everyone was going to 19's, which was a big deal in 2003, I stayed with 18s and went wider. I bought 18" BBS RGR in 8.5 and 9.5" and went with larger tires. The 18x8.5" RGR was 18lbs and 9.5 were about 19.4lbs. The stock wheels were 25lbs each. So even though I went with wider tires, i was still able to shave 3-4 lbs of unsprung weight per corner, which like you said has a more dramatic effect on performance and not overall weight savings. Sticking with 19s, i'm doing the same thing with the RCF. I went wider and lighter 19x9.5 and 10.5. The difference is not that dramatic from stock, but I should be able to have about 2-3lbs with 265/30 and 295/30 when the time comes. The stock tires are still good.
Good to hear you have reduction in rotational mass. You might also want to consider tire weight. Tire rack specifies the weights for each type of tire. It is possible to get lighter tires and you can shed 1 - 3 lbs per tire giving you a total of 4 - 12 lbs of total weight loss through tires, but that some times requires switching brands as tire weights vary greatly depending on the model/brand of the tires for a given size. Light flywheel is another way to reduce rotational inertia, but I have never seen it being offered for the ISF so not sure if there is anything like that possible for RCF.
Also, good you are sticking with the stock wheel circumference as larger diameter tires without reducing tire wall height results in larger circumference of the tire. That also makes the gear ratios taller making it slower for the car to rev up to redline.
Originally Posted by Deanrcf
You are correct, Sir. I learned this from the G35 camp. While everyone was going to 19's, which was a big deal in 2003, I stayed with 18s and went wider. I bought 18" BBS RGR in 8.5 and 9.5" and went with larger tires. The 18x8.5" RGR was 18lbs and 9.5 were about 19.4lbs. The stock wheels were 25lbs each. So even though I went with wider tires, i was still able to shave 3-4 lbs of unsprung weight per corner, which like you said has a more dramatic effect on performance and not overall weight savings. Sticking with 19s, i'm doing the same thing with the RCF. I went wider and lighter 19x9.5 and 10.5. The difference is not that dramatic from stock, but I should be able to have about 2-3lbs with 265/30 and 295/30 when the time comes. The stock tires are still good.
I don't know if the GT3 uses the exact same chassis, but if it does then it is possible to get the RCF well under 3000 pounds by gutting the cabin and such. The GT3 has no internal luxuries and weighs in at 2756 pounds.
But I didn't buy this car for that reason. The weight is not an issue to me. I actually prefer the weight. The car is solid, even at the speed limiter.
For those of you interested in some RCF weight reduction, we have a new RCF specific battery upgrade:
Some background: We have been looking for a *reliable* lightweight battery option for some time, but found the AGM based Braille and Odyssey not to be very reliable, so we gave up on the idea... until hearing about the new lithium battery technology that is making its way into the racing world.
We have tested this battery in our shop ISF for nearly 5 months and its been flawless. By testing I mean, driving it, storing the car, and intentionally discharging it numerous times just to try to get it to fail.
Some other features:
Comes with our Lexus specific mounting hardware "box" and terminal posts.
Our standard box colors are blue and silver powder coat, but we can do other powder coat colors on request.
Saves about 37lbs over the stock battery, which is huge considering that short of gutting your car, there aren't many ways of getting this kind of weight savings. Also the weight is all coming from the front of the car, so this is excellent for improving F/R weight distribution.
Battery comes with a 2 year warranty from the manufacturer, and special protection circuitry that protects the battery from damage due to discharging or short circuit.
Over 800 cranking amps and 16Ah reserve makes this a practical battery, not just for race use.
Rafi
__________________
We Engineer Track Proven Upgrades For Your Lexus! SUPERCHARGERS : ECU TUNING : SUSPENSION : EXHAUST : PPE MASTER DEALER
You can easily get 300lbs+ weight loss (seats, hood, suspension, brakes, wheels/tires, exhaust, etc...) but eventually you start losing the luxury side and tips more on performance. Stock is a great balance of sport and luxury. It is all about what you are willing to give up. Plus, it costs money...but I have already crossed that line
01-10-17, 11:14 AM
