Fully Modded RC390 VS 600?

[Tom]

I see a few of the guys here have lighter wheels and rotors, major engine mods, the whole shebang. Out of curiosity, how close does this get you to the performance of say an R6 or similar 600cc? Does a super light RC390 making roughly 45 hp- 50hp at the wheel make up for the power difference 600s crank out?

I know on a track the weight difference plays a big factor around the turns, but what about cruising/keeping up with 600s on the street?

 

[thunderrun53]

I'd say there's still a huge performance gap. If you take the most done up RC you can find and put it head to head on the street with a 2018 R6, the R6 would completely out perform the RC. Looking at just raw numbers, the R6 has 116 BHP vs the 45-50 from a prepped RC. Quarter mile times are 10.6 seconds to the R6 vs 14.? for the RC. Top speed isn't even close. Yes, the RC will be lighter, but the rest of the power just isn't in the RC's favor.

Where the RC will always outshine bigger bikes is corner speed and shorter braking distances. Those are mostly benefits seen on the track more so than the street though. On a short, technical track, I know the RC is a great weapon as that's where I spend most of my time. On the big high speed tracks, the only places the RC can catch up are in the turns. The last time I did a track day at Circuit of the Americas, there was no 300 only group, so I got mixed in with Ducatis and MVs, and R6s and so on. Now, they would all destroy me on the long straights, I couldn't even touch em. But as soon as there were any hard braking spots, I could catch back up. Most of the faster turns were 6th gear pinned for me, so passing bigger bikes was not really a challenge. As soon as the track opened up, I was left in the dust.

It's always true that the rider makes the machine, but if you are comparing apples to apples, on the street, a 600cc sport bike is just going to out perform the most advanced RC390. The track is a different story.

 

[rompus]

I'd say there's still a huge performance gap. If you take the most done up RC you can find and put it head to head on the street with a 2018 R6, the R6 would completely out perform the RC. Looking at just raw numbers, the R6 has 116 BHP vs the 45-50 from a prepped RC. Quarter mile times are 10.6 seconds to the R6 vs 14.? for the RC. Top speed isn't even close. Yes, the RC will be lighter, but the rest of the power just isn't in the RC's favor.

Where the RC will always outshine bigger bikes is corner speed and shorter braking distances. Those are mostly benefits seen on the track more so than the street though. On a short, technical track, I know the RC is a great weapon as that's where I spend most of my time. On the big high speed tracks, the only places the RC can catch up are in the turns. The last time I did a track day at Circuit of the Americas, there was no 300 only group, so I got mixed in with Ducatis and MVs, and R6s and so on. Now, they would all destroy me on the long straights, I couldn't even touch em. But as soon as there were any hard braking spots, I could catch back up. Most of the faster turns were 6th gear pinned for me, so passing bigger bikes was not really a challenge. As soon as the track opened up, I was left in the dust.

It's always true that the rider makes the machine, but if you are comparing apples to apples, on the street, a 600cc sport bike is just going to out perform the most advanced RC390. The track is a different story.

I got into a dicing match on backroads with a kid on a 600 super sport on a windy hilly backroad. I was redlined the whole time but kept up with him. The kid was shocked when he found out I only had a single.Mike
Hailwood beat bikes on the isle of man TT in 78 that had 40 hp up on him.My bike is stock.

 

[thunderrun53]

Mike Hailwood was not a real human being. He was an alien. A motorcycle racing alien who felt no fear.


It is about rider, absolutely. All these crazy kids trucking around on 'Busas and ZX-14s that will never see more than a 15 degree lean angle are proof. I am stilted though as all my RC time has been on a track. Us little bike racers have something to prove to the big bikes.

 

[hvlmike]

The r6 ...hands down. With equal riders the r6 will smoke a rc on the track as well. The rc is a fun bike and is quick in the corners but way too slow on straights. (I have both bikes)
That being said...A good rider on an rc can beat not so good riders on 600's and even 1000's .... street or track.

 

[Tom]

Yeah I was just curious, I ran the calculations for power to weight ratio between a stock r6 vs a 50hp rc390 at 330 lbs and even the numbers show that I wouldn't be able to keep up on the road.

 

[John390]

gearing plays a role too. If we are geared lower than them by enough, maybe we can stay closer until the speeds reach triple digits in mph?

 

[Tom]

^thats what I was hoping. But the problem is that the 600s already are able to rev pretty high and reach high speeds in low gears. I could maybe see if we went with shorter gearing and had a quick shifter, but then you would run into topend issues. For the RC390 to reach the same power/weight ratio, we would need to be making 70hp at the wheel with a wet weight of 300lbs.... Unless NASA starts building aftermarket parts, I honestly dont see any way for our little bike to come close to competing.

Looks like the RC390 is a fun little bike, and can be made to do great things with a few mods... But dont forget your place in the food chain.

 

[John390]

you can get them around 300lbs. costs a bit, but it has been done.

As for 70 ponies, with turbocharging, I suspect that is fully acheivable. Lots of money tho

 

[Tom]

You could probably get to that 70hp mark with higher compression using one of the exotic oxygenated fuels from VP racing, but at that point it would be pretty impractical. The tuning alone, for timing advancement, would probably blow a few motors in the process. I still have no idea how guys are advancing timing without a knock sensor during tuning.

 

[Formula390]

You could probably get to that 70hp mark with higher compression using one of the exotic oxygenated fuels from VP racing, but at that point it would be pretty impractical.

LOL No. The rest of the motor would let go LONG before you got to 70. You'd be picking up engine parts for a mile around the bike, assuming you could even find the smoldering remains in the first place.

 

[Falkon45]

Lol. We need someone to take this challenge. I honestly would, but I got too many projects already.

 

[Tom]

Ugh, now I'm even more depressed... I just ran the numbers for what the power to weight ratio of a 50 hp bike with my 200lbs of lard on it would be. If the total weight of the bike was 500lbs it would equate to a tenth of a hp per pound. A slightly modded WRX STI could easily make 350 at the wheels, and at 3400lbs it also make roughly a tenth of a hp per pound.

That kinda puts a stop to my plans for going all out on this bike. I think I'll just stick a power commander, intake, and exhaust.

 

[Sacape2]

Ugh, now I'm even more depressed... I just ran the numbers for what the power to weight ratio of a 50 hp bike with my 200lbs of lard on it would be. If the total weight of the bike was 500lbs it would equate to a tenth of a hp per pound. A slightly modded WRX STI could easily make 350 at the wheels, and at 3400lbs it also make roughly a tenth of a hp per pound.

That kinda puts a stop to my plans for going all out on this bike. I think I'll just stick a power commander, intake, and exhaust.

It's a 390. Shoulda known that before buying it. Ride it, enjoy it, and have fun doing it! You'd be surprised how well this thing handles. This thing is a surgical track weapon when a good rider is at the helm. I saw another rider lapping dudes on his track prepped RC.

 

[Tom]

I forgot about this thread. I got all bent out of shape because of bad math. I calculated my weight into the bike's total weight, but not into the weight of the car.

I have an Antigravity 8 cell, Yosh dual carbon exhaust (it's a 2017 bike), rear passenger pegs delete, aftermarket license plate holder, KTM powerparts aluminum 41 tooth sprocket.

Total weight savings is roughly 19.2 lbs, so I still have a ways to go for 300lbs.

BTW if you haven't moved to an Antigravity 8 cell, you would be surprised at how immediate you feel those 7-8lbs lost when you transition the bike side to side the first time you ride it.

So, back to the math:
if I could hit 50 whp with 500lb total weight - 0.1 hp/lb
if I drove a 3446lb car (an STI for example) with my 200lbs of manliness, it would take 365 whp to equal that 0.1 power to weight ratio. Assuming the average 20% drivetrain loss, this would equate to 456 hp at the crank.

If Chad would hurry up with the 400cc big bore kit, I'm assuming that 55whp on the 93 AKI octane pump gas we get here is possible. Most of metro Atlanta and surrounding parts of Georgia are at about 1000 feet of elevation.

If I could get down to 480lbs with me and the bike, 55whp = 0.115 (rounded up) horsepower per pound of weight.

That would require a 3,446 with a 200lb driver to make 420whp to equal a similar power to weight ratio.

So a set of Marchesini wheels, eating salads for a month, and Chad's 3mm overbore kit are my goals this year.

 

[Seth]

KTM powerparts aluminum 41 tooth sprocket.

What does this do... reduce weight or does it also provide performance? Quicker of the line or top speed?

 

[Botts]

What does this do... reduce weight or does it also provide performance? Quicker of the line or top speed?

It will make the gearing taller, so you will see lower revs at the same speed, or a perceived torque reduction of roughly 10%.

It'll be lighter too, but that's imperceptible to most people.

 

[Tom]

Both of you are correct.
The 41 tooth (aftermarket or powerparts ktm brand) is much lighter. The 41 tooth sprocket gives you much higher speeds per gear. So first gear is actually usable, and because of the decrease in torque it feeds back into the gearbox off throttle, 1st and 2nd gear are very throttle friendly. The slipper clutch removes all of the jolting, and you can literally dump the clutch going down gears.

The problem with such a drastic change in gearing is that 6th is heavily under powered if you are not modded.

Basically a 41T sprocket is the sweet spot for the street on a bike with intake, exhaust, and a tune. Lower gears are very useful for low speed traffic, and 6th becomes great for 70+mph highway commutes. If you slap a 41 tooth on without mods (like I did) you basically will only use 1st-5th unless you are cruising at a set speed for 6th, as the wind resistance in 6th will make acceleration very slow. With mods, 6th has the same acceleration as the stock sprocket but you can top out much higher.

I have Chad's timing tables running with my autotune fuel tables on PCV from Chad, WBC2 from HardRacing (closed loop tune capable), and a GreyArea KTM intake with larger injector. Paired with the Yoshi dual exhaust, and open lid K&N filter, the bike feels faster than the stock sprocket and is very street friendly.

I forgot to mention that I also installed a set of the GreyArea KTM titanium retainers, and increased my redline to 11,250. Screaming through the gears to redline sounds like a mix between a Ducati and a pissed off large bore dirt bike. You hold on for dear life while tucking in... very fun indeed.

 

[Shaharidan]

Is this really a serious question?
Are you talking about racing or the street?
If it's racing, it really doesn't matter because they aren't in the same class, and I don't think most clubs would allow a 390 in the middle weight class.
if just in general, no short of dropping an engine from one of the bigger dukes there is absolutely nothing you can do to make it perform like a 600 super sport.

Lastly more than anything it depends on the rider.
I am very low level novice racer, I can take my 390 to a track day and there will be people on liter bikes who basically get in my way.
At the same time there will be good riders on 250's who pass me like I'm standing still.

 

[Tom]

Well, I can still dream =)

You gotta admit, a 300lb rocket sure would be fun to ride. This whole idea came from me riding my friend's '17 R6. I really didnt notice the extra weight of the R6, but by no means was I putting it through it's paces. I grew up riding everything you could imagine with 2 wheels and a motor, but I have no disillusion of considering myself anything but a novice when it comes to riding a sportbike. Outside of a dirtbike track, I've never done anything remotely competitive on a motorcycle (shifter karts, and the money pit WRX and MR2 I had are a different story).

The funny thing is my buddy actually had more fun on my RC390 than his R6, but he's a lot more experienced than I am.