MWIS350

Drop some header and exhaust. I' still take RCF all day that thing look sexy.

Davew77

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.

jdmSW20

iTrader: (12)

yeah I have to agree I saw that plenty of times on the m3 forums, the F8x was putting down a lot more power bonestock than advertised. it was actually impressive

DougHII

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

DougHII

For sure. Purchase the RCF based on looks, quality and just all around great and dependable car.

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.

JT4

I couldn't agree more... A lot of these so called social media "auto journalists" look clueless for the most.

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..

airlaird

As noted in this thread...it is very well known that BMW underates the power of their vehicles

Deanrcf

iTrader: (1)

You have to factor in gearing as well. Typically, a roll race will start in high RPMs/high speeds. The M4's torque will be in its sweet spot in races from a dig or low rpm. The RCF will be making max torque in any race that starts off in high rpm, let's say 5k and above. If the race started at a point where it was too high for 1st, but very low in 2nd, then the M4 would have a great advantage. The RCF not so much. So a better data point would be for the "reviewers" to announce rolling speed and not "2nd gear". Were both cars stock? And since these are regular guys and they supposedly own these cars, I question this as well. Again, I'm not saying the M4 isn't faster, but everything I've seen from real reviews have them very close at 0-60 and no more than .5 seconds, 5mph at the 1/4 mile. BMWs are geared very aggressively 1-4, so a very high speed race would be interesting to see. 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

n2knee

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.

NickZ

I've heard this as well, there have also been issues with the crank sprocket working itself loose and crashing the valves into the pistons. It only seems to affect modified new M3/M4 cars though. M series engines are far from bulletproof even without mods, there are documented instances where the oil pump sprocket on older M3's would work itself loose and starve the engine for oil (which obviously destroyed it if you didn't catch it in time), rod bearing failures on low mileage V10 M5 engines, poorly made plastic water pumps and cooling reservoirs that would overheat engines, VANOS problems, etc. I always thought the Germans built bulletproof engines, maybe not the case here. The RCF V8 is under stressed from the factory, the tech I know at the dealership constantly harps on how he feels this motor can handle so much more.

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.

05RollaXRS

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.

Davew77

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.

DougHII

hp for top speed, torque for acceleration. Forced induction will always be the better choice for acceleration in this price range. Strike that, a friend of our brought over a new Tesla the other day. Forced induction, no forced induction, both the RCF and the M4 are sllloooooowwwwww . . .

05RollaXRS

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.

DougHII

Not a misconception and a massive effort at over intellectualizing of and twisting of my words regarding a very simple concept. Of course they are not completely separate or independent and hp is a by product of torque and rpms. I never said that. I spent the better part of 30 years tuning race cars and hot rodded Porsches for the street, some with stand alone fuel management systems. Torque at the wheels gives you acceleration or gets a car moving. Once moving, it is more important to have more hp and less torque to sustain high speed. As I stated above, total area under the curve and a curve that is as flat as possible (much like the M4 torque curve versus the RCF torque curve) is highly preferable for acceleration, but perhaps not for high 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.