RCF vs M4 Roll Racing
#17
Lead Lap
I'm confident that a forged V8, like the RC F's engine, is capable of a lot more than 700 whp with a turbo. It wouldn't be advertised yet because nobody has done it because nobody has been able to crack the ECU. A lot of people are basing the RC F's engine on the IS F. The IS F engine wasn't forged.
For the record, there were some IS F's in the 600 whp range. The RC F should be capable of that and more given it's upgraded internals.
https://www.clublexus.com/forums/is-...wer-isf-s.html <-- and this thread is 4 years old.
Until we actually start getting some RC F's into the forced induction club this is all academic though. I've always been a pioneer. I'll be first in line if it becomes available when I'm ready to boost.
#18
Racer
iTrader: (12)
It always bothers me to see the RC F take 2nd in every M4 VS RC F video...BUT, we all must realize that the M4 HP is always underrated by BMW.
I have seen numerous videos of the M4 actually being dyno'de at 480....so the M4 is really putting out much higher numbers than the claimed 425... But hey, the M4 is a fast vehicle...
airlaird
I have seen numerous videos of the M4 actually being dyno'de at 480....so the M4 is really putting out much higher numbers than the claimed 425... But hey, the M4 is a fast vehicle...
airlaird
#19
Lexus Test Driver
A forced induction engine will almost always have a huge advantage here. I just pulled a M4 dyno and it shows very linear torque and 400 ftlbs already available at 3k rpms and has 405 at 4K and around 380 at 5k. Based in Kareem's stock dyno run, the RCF's NA power is at 300 ftlbs at 3k, 325 at 4K and 350 at 5k.
Peak hp numbers are nice for magazines . . . like adding some bolt ons to increase peak hp and never see a real world improvement in acceleration. Area under torque curve is key for the discussion here and why the M4 will pull on a RCF so effortlessly.
Unlike Japanese marketing, German manufacturers are typically conservative in performance estimates. Porsche is same way. You typically get more (sometimes much more) than what you think you purchased.
http://f80.bimmerpost.com/forums/sho....php?t=1003735
https://www.clublexus.com/forums/rc-...-rcf-dyno.html
Last edited by DougHII; 09-09-16 at 04:04 AM.
#20
Lexus Test Driver
We just had an M4 convertible all last week to drive for the week and it was fun, but it honestly felt cheap and uncomfortable interior wise and the looks, especially with the top up, just are not that great to me.
This week, the wife brought home a year old CLS 550 and I like this car much better than the M4 . . . The A8 W12 we had the week before blew chunks though. Tomorrow, gotta go through inventory and figure out what car she needs to bring home next week, but no desire to have an M4 again at all and we could basically keep and drive a coupe or convertible for free for as long as we wanted it.
Last edited by DougHII; 09-09-16 at 04:25 AM.
#21
Lexus Test Driver
I guess anybody can get press credentials and get to drive these cars. It seems the quality of reviews aren't what they used to be. Too many question marks; was he shifting manually, was he in sport plus, etc, etc. We can't assume either, because I've seen too many videos of guys racing in normal and auto modes. M4 traps between 116 and 120 and the RCF 112 and 114, that's a very slow walk.
First off why would anyone consider racing these cars in the rain. Now granted, light rain, but light rain is usually the worse because it brings all of the oils and dirt to the surface and it stays there until it gets washed away by heavier rain.
And then how clueless did the M4 driver look as he was counting down. 3, 2, 1, GO.... The RC-F driver takes off and the M4 drivers looks as though he waits almost .05 to 1 second before he puts his foot down.. I don't understand what he was waiting for, did he forget they were racing..What a putz....
This is not imply the M4 is better, faster etc, if I was buying one of these tomorrow I would take the RC-F. I'm just saying these types of uncontrolled races leave a lot to be desired..
Last edited by JT4; 09-09-16 at 01:35 PM.
#22
As noted in this thread...it is very well known that BMW underates the power of their vehicles
#23
Pole Position
iTrader: (1)
I suppose this is more in reference to the post you quoted, but the focus on peak hp is interesting. Acceleration is a function of area under the torque curve.
A forced induction engine will almost always have a huge advantage here. I just pulled a M4 dyno and it shows very linear torque and 400 ftlbs already available at 3k rpms and has 405 at 4K and around 380 at 5k. Based in Kareem's stock dyno run, the RCF's NA power is at 300 ftlbs at 3k, 325 at 4K and 350 at 5k.
Peak hp numbers are nice for magazines . . . like adding some bolt ons to increase peak hp and never see a real world improvement in acceleration. Area under torque curve is key for the discussion here and why the M4 will pull on a RCF so effortlessly.
Unlike Japanese marketing, German manufacturers are typically conservative in performance estimates. Porsche is same way. You typically get more (sometimes much more) than what you think you purchased.
http://f80.bimmerpost.com/forums/sho....php?t=1003735
https://www.clublexus.com/forums/rc-...-rcf-dyno.html
A forced induction engine will almost always have a huge advantage here. I just pulled a M4 dyno and it shows very linear torque and 400 ftlbs already available at 3k rpms and has 405 at 4K and around 380 at 5k. Based in Kareem's stock dyno run, the RCF's NA power is at 300 ftlbs at 3k, 325 at 4K and 350 at 5k.
Peak hp numbers are nice for magazines . . . like adding some bolt ons to increase peak hp and never see a real world improvement in acceleration. Area under torque curve is key for the discussion here and why the M4 will pull on a RCF so effortlessly.
Unlike Japanese marketing, German manufacturers are typically conservative in performance estimates. Porsche is same way. You typically get more (sometimes much more) than what you think you purchased.
http://f80.bimmerpost.com/forums/sho....php?t=1003735
https://www.clublexus.com/forums/rc-...-rcf-dyno.html
Found it. So a real roll race where the RCF is in it's powerband (5k and above) would be better. The RCF will still probably lose, but It should be a very good race and exactly walked like it the video
Last edited by Deanrcf; 09-09-16 at 09:13 AM. Reason: link
#24
Driver School Candidate
I do know that the F80/82 are underrated, but as I have stated there is NO way a regular F80/82 will reach 480 whp STOCK. Stock usually measures at around 420 whp. 480-490 for the M4 GTS.
#25
One of those links I posted has some M4's blowing their motors with 700 whp tunes. The rods were snapping.
I'm confident that a forged V8, like the RC F's engine, is capable of a lot more than 700 whp with a turbo. It wouldn't be advertised yet because nobody has done it because nobody has been able to crack the ECU. A lot of people are basing the RC F's engine on the IS F. The IS F engine wasn't forged.
For the record, there were some IS F's in the 600 whp range. The RC F should be capable of that and more given it's upgraded internals.
https://www.clublexus.com/forums/is-...wer-isf-s.html <-- and this thread is 4 years old.
Until we actually start getting some RC F's into the forced induction club this is all academic though. I've always been a pioneer. I'll be first in line if it becomes available when I'm ready to boost.
I'm confident that a forged V8, like the RC F's engine, is capable of a lot more than 700 whp with a turbo. It wouldn't be advertised yet because nobody has done it because nobody has been able to crack the ECU. A lot of people are basing the RC F's engine on the IS F. The IS F engine wasn't forged.
For the record, there were some IS F's in the 600 whp range. The RC F should be capable of that and more given it's upgraded internals.
https://www.clublexus.com/forums/is-...wer-isf-s.html <-- and this thread is 4 years old.
Until we actually start getting some RC F's into the forced induction club this is all academic though. I've always been a pioneer. I'll be first in line if it becomes available when I'm ready to boost.
Anyway, I was kind of surprised by how effortlessly the M4 caught the RCF, and I'm not going to take anything away from it as the thing hauls a** for sure. Regardless, I'm not a fan as I purchase my cars and try to hold on to them for a while.
#26
Lexus Test Driver
I would say, irrespective of the power/torque difference, the 400 lbs weight difference is what truly matters. Everything else remaining the same, if RCF and M4 weighed the same then it would not be a question of RCF being slower.
Last edited by 05RollaXRS; 09-09-16 at 02:21 PM.
#27
Lead Lap
I'm with ya. I give credit where credit is due. I don't deny that it makes good power in stock form and that it will smoke my stock RC F in a drag race (given equal drivers). I just know that the RC F engine has a lot more potential than many people realize. I eagerly await the chance to prove it.
#28
Lexus Test Driver
. . . . I saw a video where both cars made a run to over 150mph, but were filmed separately from each cars cockpit. Neither car never ran away from each other. I'll see if I can find it.
Found it. So a real roll race where the RCF is in it's powerband (5k and above) would be better. The RCF will still probably lose, but It should be a very good race and exactly walked like it the video
#29
Lexus Test Driver
No, that very statement is not correct. That is the most common misconception where torque and HP are viewed as separate entities. HP is not for top speed. HP is merely torque over time. HP only tells how much torque engine is generating near its redline, which is why it is always quote near its redline.
Being an engineering, I can dive deep into the physics explanation, but just to keep things simple, horsepower is extrapolated from torque and rpms.
The equation for torque/HP relation is:
HP = Torque x RPM ÷ 5252
So if two cars are generating peak HP of 500 HP@7100 rpm vs 400 HP@7100 rpm, it merely means the car making 400 HP at 7100 rpm has torque curve falling much more quickly.
I can easily calculate the torque figure by plugging numbers in it:
500 HP = Torque X 7100 RPM ÷ 5252
Torque = 369 ft-lbs@ 7100 rpm
400 HP = Torque X 7100 RPM ÷ 5252
Torque = 295 ft-lbs@7100 rpm
The combination of factor that will determine the overall acceleration is product of gear ratios from final drive and individual gearing (how short they are since gears are torque multipliers) and how the torque curve looks like across the entire rev range. Aerodynamics/drag and overdrive gear ratios play a huge part in top speed.
Being an engineering, I can dive deep into the physics explanation, but just to keep things simple, horsepower is extrapolated from torque and rpms.
The equation for torque/HP relation is:
HP = Torque x RPM ÷ 5252
So if two cars are generating peak HP of 500 HP@7100 rpm vs 400 HP@7100 rpm, it merely means the car making 400 HP at 7100 rpm has torque curve falling much more quickly.
I can easily calculate the torque figure by plugging numbers in it:
500 HP = Torque X 7100 RPM ÷ 5252
Torque = 369 ft-lbs@ 7100 rpm
400 HP = Torque X 7100 RPM ÷ 5252
Torque = 295 ft-lbs@7100 rpm
The combination of factor that will determine the overall acceleration is product of gear ratios from final drive and individual gearing (how short they are since gears are torque multipliers) and how the torque curve looks like across the entire rev range. Aerodynamics/drag and overdrive gear ratios play a huge part in top speed.
Last edited by 05RollaXRS; 09-09-16 at 05:17 PM.
#30
Lexus Test Driver
No, that very statement is not correct. That is the most common misconception where torque and HP are viewed as separate entities. HP is not for top speed. HP is merely torque over time. HP only tells how much torque engine is generating near its redline, which is why it is always quote near its redline.
Being an engineering, I can dive deep into the physics explanation, but just to keep things simple, horsepower is extrapolated from torque and rpms.
The equation for torque/HP relation is:
HP = Torque x RPM ÷ 5252
So if two cars are generating peak HP of 500 HP@7100 rpm vs 400 HP@7100 rpm, it merely means the car making 400 HP at 7100 rpm has torque curve falling much more quickly.
I can easily calculate the torque figure by plugging numbers in it:
500 HP = Torque X 7100 RPM ÷ 5252
Torque = 369 ft-lbs@ 7100 rpm
400 HP = Torque X 7100 RPM ÷ 5252
Torque = 295 ft-lbs@7100 rpm
The combination of factor that will determine the overall acceleration is product of gear ratios from final drive and individual gearing (how short they are since gears are torque multipliers) and how the torque curve looks like across the entire rev range. Aerodynamics/drag and overdrive gear ratios play a huge part in top speed.
Being an engineering, I can dive deep into the physics explanation, but just to keep things simple, horsepower is extrapolated from torque and rpms.
The equation for torque/HP relation is:
HP = Torque x RPM ÷ 5252
So if two cars are generating peak HP of 500 HP@7100 rpm vs 400 HP@7100 rpm, it merely means the car making 400 HP at 7100 rpm has torque curve falling much more quickly.
I can easily calculate the torque figure by plugging numbers in it:
500 HP = Torque X 7100 RPM ÷ 5252
Torque = 369 ft-lbs@ 7100 rpm
400 HP = Torque X 7100 RPM ÷ 5252
Torque = 295 ft-lbs@7100 rpm
The combination of factor that will determine the overall acceleration is product of gear ratios from final drive and individual gearing (how short they are since gears are torque multipliers) and how the torque curve looks like across the entire rev range. Aerodynamics/drag and overdrive gear ratios play a huge part in top speed.
On the race track, I have used different cams and tuning that actually decrease area under the torque curve and both torque and hp below 5252, but increase hp curve above 5252 and peak hp to provide me a little better speed on momentum type tracks where massive speed is rarely or never scrubbed. The focus here is maintaining or increasing speed once moving through more hp as the sacrifice of torque.
There is some truth about building for torque and hp will follow, but there is always a trade off. While you cannot have hp without torque, you can have torque without hp . . . i.e., dump truck.