Crux of the Biscuit

[hombre]

Excessive valve overlap will move the powerband of a supercharged engine up significantly, and a supercharged engine with narrow cam lobe seperation gives power very suddenly in a narrow RPM range. Increasing cam lobe separation in a supercharged engine will broaden the torque band and increase low end power. This can be done by advancing the exhaust cam and retarding the intake cam.

Should I, in the interest of furthering the knowledge base for the Supercharged R3, after the installation of my "super" exhaust system and long duration exhaust cam, then consider experimentally advancing my exhaust cam 2 degrees, and possibly retarding my intake cam 1.5 degrees, and of course re-tuning? After all, the the crux of the biscuit is the apostrophe!

FURTHER!

 

[dragline708]

Hombre ,
Last I heard you have something like
267 rwhp & more then 200 + # TQ
What do you suppose the R3's
mechanical limits are ?
Before you need to beef up the
crank , connecting rods , pistons ,
O - ring the heads, splay the bolts ,
and start using
http://www.hardblok.com/info.html .

Once you think its fast enough ,
Paint it Red

wayne

 

[Joker]

****, I was expecting a recipe!

Seriously though, I really think you ought to give it a try.

Purely selfish reasons on my part. You are already well over 20hp ahead of me and the further you push it, the further I know I can go before other things start braking.

The only way we're ever going to know the answers to Wayne's question is if somebody tries it, and you're just the bloke for the job. Go on, you know you want to.

Good luck.

 

[hombre]

Actually, Wayne is telling me (subtly and effectively) that I have cement between my ears for not listening to him!

No doubt he is correct, as what I have now seems totally reliable with stock pistons and rods. Further increases in low end torque would stress rods and crank, would they not? Let's see what happens to the power band with the exhaust system and exhaust cam designed for a SC R3 first. If the exhaust system broadens the power band, do I really need to advance the cam for more low end torque? I'd rather boost torque in the upper power band, which is what the exhaust system is actually designed to do. Less stress on the crank when turning higher RPM, and I think the rods and pistons are fine if kept under 7250 RPM.

Further opinions would be appreciated.

 

[Sidecar Flip]

Walt:

Sounds to me like it's time to dress a spare block. Why not buy a wrecked, but mechanically useable R3 for spares. You could have the engine mildly re-worked and pull the final drive so you'd have a spare set in case you overextended your engine somewhat and it went south.

That sounds to me like the ticket. That way, you can explore the edge of failure without compromising your seat time.

 

[Jamie]

There's that widespread notion than the Rocket's weakest link between one's right hand and the rear rubber is the tranny. I would certainly be tempted to viagra-ize the engine, Hombre, i.e. to graft more ponies onto it, one way or another, were it not for said tranny-related anxiety (after 3 gearbox fixes under warranty, YOU know what I am talking about). Or mansuetude.

The question is: In your view, how much "more" can it cope with Jamie

 

[hombre]

I think the R3 can handle up to 300HP if the torque is produced in the upper RPMs. That's 218 Ft Lbs at 7250 RPM... not such an elusive goal from where I am now. I haven't had any problems with my transmission with my present HP/TQ since it was properly re-assembled with locktite.

My new equal length headers have made such an impressive difference in low end torque, that I may take Nev's suggestion and advance the long duration SC cam when I install it.

 

[REGULATOR]

I know you originally built this thing for Maxton... but I cannot take the suspense any longer, get to a dragstrip and let us see what this beast will do!!!

I want to know what I could potentially aim to achieve if I lost about 50 pounds and added a Supercharger ( obviously not as fast as yours, but could get in the neighborhood)


Richard once said with a TTS kit I could achieve 9.50's ( hmm I don't think he saw how big I am)

 

[Joker]

Richard reckons he got his (now MINE) to do 10 flat with a terminal (I think) of about 140mph. That is with ToRs, standard clutch apart from heavier springs and standard cams, but he's about 7 stones (98lbs) lighter than me! He also said that at that speed the bars are rotating in their mounting as you hang on for dear life. Can't wait for August and the Bulldog Bash (run by the HAs and the only place in this country you can get on a strip without full leathers) so I can give it a try.

 

[W. Tripp]

No doubt he is correct, as what I have now seems totally reliable with stock pistons and rods. Further increases in low end torque would stress rods and crank, would they not? Let's see what happens to the power band with the exhaust system and exhaust cam designed for a SC R3 first. If the exhaust system broadens the power band, do I really need to advance the cam for more low end torque? I'd rather boost torque in the upper power band, which is what the exhaust system is actually designed to do. Less stress on the crank when turning higher RPM, and I think the rods and pistons are fine if kept under 7250 RPM.

Further opinions would be appreciated.

RPM is the enemy of rods, valvetrain, and bores. A wise engine builder (Larry Widmir) once said "RPM means 'Ruins Peoples Motors'". Heat (and the time it can effect parts) is the enemy of pistons and bore sealing. You would be amazed at how much of the heat in an engine is caused by nothing more than the valvetrain friction - especially the valve springs.

As for a max rpm, the valvetrain mass -vs- spring pressure, the piston ring mass, and the piston speed is going to set your limits. If I had a good measurement (center-to-center) of the rod length, and the thickness of the compression rings, I could give you the suggested limits (street and racing) for these - they are relatively easy to figure.

It does not suprise me that the new header has improved bottom end efficiency - likey with reduced stresses as well. The R3 engine is tuned almost too conservatively, and your cam(s) change make a big difference. At higher rpm, the forced induction is offsetting much of the exhaust's scavenging effects. But I would wager that you see a slight reduction in boost pressure, with an increase in power - once you get a chance to tune and test the bike again.

Stating a horsepower limit (without rpm) is open ended IMHO. Torque (and where it is made) is what will determine the limits of the engine and gearcase at a given rpm. Lifespan of parts will also be a big issue.

However, just how much torque do you think the bike can hook up to the pavement in lower gears? It is easy to make more power and/or torque than you can comfortably handle... ever riden a turbocharged GSX1300R? This is why the choice of the centrifugal supercharger so well matches the R3, IMHO. Although I plan on going as far along the naturally asperated route as I can... within reason.

Just my .02 (uncorrected for Dollar devaluation and inflation).