05RollaXRS

Completely incorrect. IS-F owners are getting all riled up for people saying "RC-F should be faster". It is a newer better car. It should be faster. That is what Lexus' promise was.

The RC-F has a PWR of 8.6 lbs/HP. (4040 lbs test weight/ 467 HP). It might be physics, but your math is all off.

It has power to weight advantage. More importantly, it has a broader torque band as it stretches up to 7300 rpm (it still makes over 85% of its peak near redline) and better tires.

It has all the advantages.

MK4Sup_isF

iTrader: (10)

I wasn't refering to you. I meant to type 12.4-12.5 "real world" stock ISF was able to achieved by even fellow board members. I'm not denying how good the RCF is around the corners considering the 4k lbs. It is astonishing really. Yes Lexus did give us the 12.5 documented time, I'll take that number. Just don't have to bash an old car to show how good the RCF is. RCF gives has a teterifc ride and corners well, I'll give you that. Interior is also beautiful, as it should.
Yeah my mistake about the 12.2. I meant to say 12.4-12.5 by members on this board. Yeah I don't doubt the RCF is faster in the straight line, I'll even take the 12.7 numbers published by magazines. Just don't use the slower numbers of the ISF to support what we know so far to be the best number for the RCF. Can the RCF get faster as more people get more favorable condition at the local 1/4 mile? Sure, but until then; lets compare the best possible time for both cars as documented instead of picking a lower number vs a higher number to prove a point.
Here is one example of 12.44 , I guess I'll have take his word for it being completely stock
http://www.dragtimes.com/Lexus-IS-F-Timeslip-16729.html

DrRick

im using hp at the wheels vs published hp. 3800 lbs/350 hp (which is what most folks in the real world have gotten from their ISF) vs 4038 lbs /388 hp (from the only dyno available of the RCF). with respect to the broader torque curve...i would love to see a graph of the dyno for the RCF because i havent seen one yet. i would be willing to bet that it looks suspiciously 'peaky' like the dyno from the IS-F.

and no...IS-F owners arent riled up over anything other than a 'fellow' ISF owners that shouts any kinda critique about his upcoming purchase down without the slightest hint of objectivity.

the RC-F is 7 yrs newer than the IS-F. it should be MUCH faster than the IS-F. but its not. thats not ISF owners' fault...

ISF001

It's always a drivers race.

More data to share:

RCF

Accelerations:

0-80 km/h (sec): 3.3
0-100 km/h (sec): 4.4
0-160 km/h (sec): 9.6
0-200 km/h (sec): 15.2

0-50 mph (sec): 3.4
0-60 mph (sec): 4.2
0-100 mph (sec): 9.7
0-150 mph (sec): 24.8

ISF

Accelerations:

0-80 km/h (sec): 3.5
0-100 km/h (sec): 4.6
0-160 km/h (sec): 10.4
0-200 km/h (sec): 16.5

0-50 mph (sec): 3.5
0-60 mph (sec): 4.4
0-100 mph (sec): 10.5
0-150 mph (sec): 27


My 2012 ISF does/has done 150 mph in just under 30 seconds. How about yours?


Two fast cars--just one faster than the other...in the straights. Things appear to change at 100 mph.

DrRick

got a time slip for that? VBOX?

05RollaXRS

Ahhh I see what you did there. Pick the dyno numbers that were done on different dynos, different days, different times. You ignored the 333 wheel HP dyno for the IS-F done by Automobile mag? Fact is, there can be up to 20 - 30 wheel HP difference in dyno numbers based on variables. Dynos are used for tuning (before/after). That is all they are good for. Not comparisons in a cross section format.

http://www.automobilemag.com/reviews...-f_dyno_chart/

If RC-F and IS-F get dyno'ed on the same day and on the same dyno, I would get your argument. Until then, stick with the factory tested crank horsepower.


Corrected times? If the corrected times were really normalized, there would not be a variance of over 0.5 seconds typically on the same model tested over different times and tracks. I once posted 5 tests of RS5 all done by MotorTrend and the times varied from 12.2 to 12.9 seconds. That is a huge variance for something that should be "corrected".

DrRick

actually...what i did was a search of stock dynos for the ISF. the OVERWHELMING majority are in the 348 - 358 hp range. and if the ISF is REALLY only putting down 333 hp...than thats even more disappointing that the RCF is trapping very similar mph (which....as im sure you know...is a pretty accurate measure of hp)


corrected to sea level and altitude. that has nothing to do with traction and the variances within vehicles...

05RollaXRS

It does not matter. You took two randomly selected dyno numbers and compared them. You said it was "only 0.4 lbs/hp". Do you realize, even 0.4 lbs HP to the wheels, is a substantial difference? That is because it is factoring in the 15 - 17% drivetrain loss.

BTW, I have seen many people on lexusfforum saying they are getting between 332 - 336 wheel HP range. Again, it goes back to me saying, the variability in dyno numbers of around 20 wheel HP is very common since dynos don't account for the density of air. The dyno numbers can fluctuate based on the gear you select for dyno. For example, it will be different in 5th gear versus 6th gear.

And your point is? You asked me about "correction factor". The final time published by the magazines are after all of their "corrections". Even with an AWD car like RS5 that launches consistently, they had a huge variance of 0.6 seconds in their 5 tests.

Case in point, two tests done on different days, times and tracks are not directly comparable.

DrRick

mentioned correction because you jumped from magazine times to posting a video of vehicles at altitude to make a point.

would still be interested in seeing this dyno graph that shows 85% of the torque available. or are you just extrapolating due to 5252 rpm, knowing peak hp, etc?

in the end...time will tell once these start getting into the hands of enthusiasts that will provide hard data instead of impressions. i sincerely hope it works out for those that defend it so vociferously. but expecting the TVD, with its added weight and non-existent additional benefit on straight line performance over a mechanical diff, to be some sort of saviour is a Fool's Errand, imo...

ISF001

Unless you know something Yaguchi has overlooked, the carbon TVD will be the ride in the F line. Your claim on unsubstantiated benefit is as much conjecture as my claim that it will deliver benefit.

The TVD has a lot of promise in the hands of capable drivers--like any other car. The new Vet has great documented numbers. Yet, few of the drivers are able to emulate the numbers, and we all know the variables.

I admire the tenacity of those who take opposing positions, regardless of where they stand on the new F. If I had my way, I'd keep both the RC F and the IS F. I just do not need to road rockets.

The numbers posted indicate substantial gains in performance over top cars in the class. This is relatively black and white, IMO.

My hard earned money is riding on Yaguchi.

One more thing: this is not the new Ferrari 458 Speciale. However, the Speciale is to the GT3 as the RC F is to the IS F. All great cars, but both the Speciale and the RC F have the edge.

Happy Holidays Guys! (We all probably need to lighten up.)

05RollaXRS

And what was my point all along?

My point all along has been that despite all of the comments by IS-F owners, RC-F's 12.6 seconds in this video is simply incomparable to what the IS-F has been running.

There are way too many variables (which is why I posted the 5000 feet above sea level) that can skew the numbers. Altitude, density, moisture, traction on the track (is ther powder compound on the track or not?), heat etc. I maintain, it can only be determined by a head to head drag race of the IS-F and RC-F to see how they stack up.


Simple mathematical formula that the dyno uses

HP = torque X RPM / 5252

So if we know the HP is 467 HP@ 7100 rpm, then I can solve for torque. This can give us the torque back through mathematical extrapolation.

467 = torque X 7100 / 5252

Torque = 346 ft-lbs@7100 rpm or 89% of the peak torque still sustained near the 7300 rpm redline. That is an amazing torque curve.

DrRick

im sorry man...the TVD is an accessory for tracking the car. it will help straight line speed coming out of a corner but it is little to no benefit over a limited slip diff on the type of surfaces where acceleration tests are run.

its not conjecture...its the very definition of what the unit does.

jat0223

iTrader: (1)

Of course it will impact straight line acceleration. It makes the car heavier so it'll be slower.

ISF001

Sorry, but that's inaccurate.

Road & Track ran its times in the TVD, non-carbon. The times include the Motown mile--An impressive time if you objectively look at the competition.

ISF001

With the TVD, Torque can be better targeted to the wheel with higher friction locking potential. This reduces wheel spin, and it is particularly of value when each wheel is on a slightly different surface at the start. The outcome is an increase in propulsion and better times.

Now, how much improvement in launch with the TVD is required to nudge times 2-3 tenths?

Let's hold back the horses until the production TVD car lands in March.

There is no intention to push aside the merits of my IS F. It's a superb car.

I am trying to point to the benefits of the new technology.