Crux of the Biscuit

[hombre]

Thanks, Wayne. It's all very interesting to me. If I had nothing but time (and money) to devote to the R3, I'd explore even more cam profiles. The lobes on the "supercharger" cams made for me by Nev have very different profiles for intake and exhaust, that both appear symmetrical. It would be interesting to learn what happens with 2 different profiles for the paired valves in each cylinder. Maybe next year.

 

[hombre]

Using the advanced position for the exhaust cam, and the retarded position for the intake cam, only dropped the cranking pressure by about 7 PSI. That shouldn't result in too much loss of lower RPM torque, and the wider LSA should benefit the higher RPMs with the supercharger boost.

Time to button her up and see.

 

[W. Tripp]

Watch to see if peak boost drops.

 

[hombre]

Looking at the stock R3 cam lobe centers, the LSA is extremely tight at 101.5 degrees. This is great for low end torque but way less than what's recommended for SC engines (112-114). It's no wonder all the SC R3s with stock cams seem to be limited to 230-240 HP. The longer duration of Nev's SC cams also results in tight valve to piston clearances, and the "new" cam positions improve clearance. I may lose a bit of power on the low end, but expect gain in the upper RPMs. Wider LSA also reduces the chance of detonation.

I'll fire her tomorrow.

 

[Neville Lush]

cams etc

Hombre,I just read this.All interesting.Maybe an email with your cranking pressure? Also Mr W.Tripp, I rarely go to the pub,and never open a beer until the work is done.Am not an expert like you,just a bloke working in a tin shed.Hombre may wear the bike out tuning it With new cams/settings fuel and ign need to be optimised to see true benefits. Have you put an extra fan on the eddy current brake yet?

 

[dragline708]

Walt ,

Nev knows the clearances of the R3
Since he's had them apart many times .
Personally , I think a lobe separation something like
this would be nice and move the torque a bit higher

intake centerline 103
exhaust centerline 113
103
+113
_____
108 = lobe separation

The billet blank .... roller cam , I designed
and had Crane Cams grind it . I really liked
the torque & hp curve Max tq was flat @ 3500 & 4000 521 # TQ
@ 5000 Rpm Tq was # 500 , so lost , very little @ cross over = hp & tq merge

@ 6500 max hp= 538

Designed it for street use
Could have designed for max Hp @ High rpm range ,
then your losing alot of mid range Tq .
Then it's becoming a drag vehicle
and not very practical for street use
I really liked that lobe separation

ps: I'd cross the traps @ 7200 rpm's
.....it was an 8000 Rpm spring rate float
if I remember right ( new owner has cam card profile )

wayne

 

[hombre]

Wow, this is great! Finally all the R3 gear heads together in one thread! (Except for Silver Bullet... I expect he'll chime in anytime)

Hombre,I just read this.All interesting.Maybe an email with your cranking pressure? Also Mr W.Tripp, I rarely go to the pub,and never open a beer until the work is done.Am not an expert like you,just a bloke working in a tin shed.Hombre may wear the bike out tuning it With new cams/settings fuel and ign need to be optimised to see true benefits. Have you put an extra fan on the eddy current brake yet?

Nev

We had to put TWO extra fans just on the eddy brake to tune my SC R3 last time. Still had to let it cool between full RPM step tests. I can't see how a 250i could be rated for 750 HP without an AC unit on the brake.

Walt ,

Personally , I think a lobe separation something like
this would be nice and move the torque a bit higher

intake centerline 103
exhaust centerline 113
103
+113
_____
108 = lobe separation

I really liked that lobe separation

wayne

Wayne (dragline)

An intake centerline of 103 is possible with the SC intake cam I have now. I'd love to try an even longer duration SC exhaust cam (close to 250 degrees) with a centerline close to your suggestion. Everything I read says SC exhaust cams should have more duration than the SC intake cam, and even more LSA than I have now. Nev, you listening?

First Run Report:

With the current SC cams installed in the suggested advanced/retarded positions, the bike fired right up no problem. The idle hunted a bit, then settled right down. Idle vacuum was actually greater. I currently can only check SC boost with a large handheld meter (still waiting on SPA gauge), so the readings of .92 to .94 BAR max boost are really inconclusive. This was a static measurement with no load on the engine (bike in neutral)... not a dynamic (road load) measurement. The bike was already so freakin' fast, I really can't say from seat-of-pants if it's faster now or not. I can report that it is running a richer AF ratio at lower RPMs, and leaner AF at higher RPMs. The most noticeable change is that the engine seems to rev much faster (and almost too fast, as 7250 shows in a blink). It's like the engine was no longer being held back by any internal friction. I suspect that the short duration exhaust cam and narrow LSA were creating pumping losses, and holding her back. I absolutely agree with Nev, that the bike has to be completely retuned for both fuel and timing... more of both at higher RPMs, me thinks. Unfortunately, this will have to wait until we return from Europe.

 

[dragline708]

Walt ,

103 int centerline
113 exh centerline

Duration @ .050 lift intake = .258
Duration @ @ .050 lift exh = .266

Advertized duration 308 / 316

That was with a .630 lift solid roller

Nev would know the millimeter conversions
and of course an R3 won't take a .630 lift cam
with 1.65 roller rockers , but the lobe separation on intake & exhaust lobes ,
and duration was awesome , to keep the hp & tq up @ the conversion
point

I must have used ream of print paper
to dial in that combo , using DeskTop Dyno

PS: maybe you could off set grind the crank
to give you some more cubic inches

wayne

 

[hombre]

Thanks, Wayne!

I'd be interested in playing with other cam durations at some point, but I don't think I want to get into grinding the crank... maybe different length rods?

 

[Brembo]

Brembo

I've seen your torque chart... and with the right rear tire and correct launch, you'll turn sub 10s no problem.

brembo,
you may want to look at a car tire.bridgestone potenza reo1 or dunlop durreza star spec. go 205 to 225. you'll hook like no tomorrow. you got nev's clutch? if not, you'll need it with these tires. sounds like you're hazing a little bit on the top after you feather the bottom.

greg

I feel like I can get sub 10's also. Yes it would have to hook up off the line. Greg, I had that exact thought concerning the car tires, thanks for the suggested type/sizes. I'll have to put the car tire on a stock R3 rim and take the CF rim of on track day, to pretty for the track and will it handle the bite of the Darkside? who knows. Also launching off the line like that will take some getting use too.