Topic: 500 racer dyno results

[turboguzzi]

Finally had the time for some dyno runs and as some already said here, it’s worth the price and trouble in gold. Found there an easy extra 10% just by swapping main jets. A friendly shop let me had the dyno for the whole of Saturday morning to do as many runs as I wanted at 25$ the hour.
Engine always felt strong but after an initial run of 55 rwhp, jetted up from 130 to 135, then to 140, each change yelded another 2.5 hp, it got worse with 145 mains. Played then with ignition timing but found little power there even if things got a tiny bit better by backing it a good 4 degs from where I was (stock 35 at full advance)
Regretfully, the dynojet setup could not pick up my ignition pulses so RPM and torque could not be calculated. I plotted myself the red torque line from the HP.  Looking at the tacho, 140 equals 13,000 rpm, so peak torque is at 8500, peak power at 10,500
61 rwhp is not bad going for a 500c.c. home tune job, still not a match for PeterC’s claimed 63 but then I am running only swap meet ex-GS750 27mm VM’s and not smoothbore CR’s.
Would be nice to hear opinions on this one, my own feeling is that it peaks a bit early, thinking of retarding the cam a bit.

Your ideas will be appreciated.

TG

[mlinder]

Nice.

[Shenanigans]

Thats probably more than what my 750 is currently putting out. 


How about some pictures of the beast?

[goon 1492]

Thats probably more than what my 750 is currently putting out. 


How about some pictures of the beast?

 Dang dude don't give in without a struggle

[tank410]

awsome man

[hapsh]

The graph shows km per hour, is that correct?

[scondon]

 I Like the "rocket" trajectory of your power curve, Turbo'. I retarded the cam on my 750 a few degrees and though the power doesn't come on as soon it holds pretty nice at high rpm's and I like it for road racing. Letting off the throttle slows the bike better at high rpm's and I do a bit less braking before turns.

  What kind of ignition are you running that the dyno couldn't pick up the pulse? Kind of a bummer that you couldn't get that info. No AFR either?

   Pretty nice power you are able to get with intuitive tuning

[ezroller]

Awesome! 10,500 rpms

[Sam Green Racing]

TG, that's a nice increase in power, I would think the RWBHP of a stocker would be around 40 so you have a 50% increase and have raised the useable power from 9,000 to 10,500rpm.
You will find your lap times will tumble by changing gear at 10,500 instead of hanging on for 12,500rpm as you have been doing.
It'll make the motor less likely to go bang as well
Good luck with the coming season.

Sam.

[turboguzzi]

Sheningans, look up at my posts and you'll find plenty of pics. Attaching a recent one here from last race.
Yes, that's kilometers per hour, run the test in third gear.
Scondon, on track engine's almost too torquey as I dont really ever dip bellow 6-7K and by then it's pulling pretty hard hard. gonna try some light retarding after this weekend's race.
I am running a GSXR750WP ignition. We tried both the pick up for the HT leads and the signal wire from the pickup and it wouldnt react, but then, it could be something to do with the dyno's PC. That place is a bit scruffy...

Sam, thanks for the tip, in a way I was already trying this in my last race after seeing the dyno curve. indeed, both top speed and lap times were same when up shifting at 10-11 rather than 12K+. didnt make me faster but I stressed the engine a lot less. Still, I need to brake less for turns :-). I remember someone here saying once that no matter what, sohcs dont breath well beyond 10-11. He was onto someting I guess. BTW, an old copy of cycle magazine I've got shows a dyno of a stock CB550. 38 rwhp.

Cheers
TG

[scondon]

Turbo, what country do you race in and what class  are you in? I am researching the AHRMA here in the US as well as the AFM in order to figure what class I could race my over-bored 750's in. I come up with Vintage Superbike(heavyweight).

   Sweet shot of you on the track, thanks

[turboguzzi]

I am doing the italian classic bike championship, 500c.c. production based class. Even if this year the added 70's TZ250 and 350 to our class and they are simply on another planet. Last time I checked they had 10 mph top speed on all the sohc fours, doing lap times of front row in the 1000 class... we are all bitcihin the organziation to change the rules next year.

Only one really fast guy on a CB500 twin with plenty of todd henning parts is manging to keep them in check...

What are you up against in heavyweight superbike? KZ and GS 1000's? Tough!

TG

[bwaller]

Good numbers TG, congrats. Did you end up finding some pistons to help that cause? How much over stock displacement do your rules allow?

No damn fair feeding you guys to the TZ lions, but... c'est la vie j'imagine!

[scondon]

What are you up against in heavyweight superbike? KZ and GS 1000's? Tough!

TG

   I would fully expect to have my arse handed to me and would be happy with anything short of complete embarrassment      While researching I happened upon some speed trap results on the Daytona track and the leader averaged about 148mph through the trap, but the next guys were 128 and falling. My bike will hit 125 very quickly and has quite a bit more left. I was looking for a track layout to understand how much straightaway they had to reach those speeds but have only come up with this so far..

http://www.motorcycledaily.com/12august04_daytona.htm