GSXR 750 head info

[latheboy]

Anybody know what the combustion chamber CC is for the oil cooled GSXR 750(749 no dot) head is?
Piston to deck at top dead center?
Piston dish or dome CC's?

I've stepped into the future and now have a smart phone, I got the Virtual Dyno app as a laugh and i'm missing some figures to see how awesome my bike is in the electronic world.

[BANDITROD]

if the phone is smart dont you think it should already know the answer

[latheboy]

Yeah it should, so it's not really smart.

It's just a phone with the interweb too, thats not smart....

[El_Hefty]

use math, you know the CC its 749 divide by 4 and im sure you can work out the rest if you know the compression ratio

[latheboy]

I was hoping for the easy way out Hefty.....
Brain's not up to the easiest of math today.

I had done 749/4 etc but it doesn't work when i plug the numbers into the program

[El_Hefty]

but your the owner of a smart phone. lifes easy from here...

haha know what you mean though

[Dynomutt]

Bore is 70mm stroke is 48.7mm capacity per cylinder is 187cc. From memory I seem to think the combustion chamber volume is nominally 17cc. They do all vary a little so it is worth measuring them to be accurate. The stock pistons do not have a large intrusion into the compression void at TDC. I seem to think the actual C/R is around the 10.6-1 mark. I can't remember the above piston volume at TDC, as it is quite a long time since I've measured the longstroke motor.

[latheboy]

Thanks dynomutt, one of the problems with the app is it doesn't let you input the CR, it works it out for you...

I Don't need the app cause i have many dyno's to play with, its just for interest.....

Also I can borrow Dynomaster 2000 if you've heard of it. The guy who has it says the program has been correct to within 10 HP when compared to a real motor on the dyno.... Same specs etc

[Dynomutt]

I'm always a little suspicious of the dyno apps, there are a huge amount of variables involved even with two motors of exactly the same spec. They're ok as a very rough guide to what you may expect from a certain engine combo. But I've seen such variations across the bikes I've run on my dyno to know that it is not quite as clear cut as the dyno apps would like you to believe.
Because I've done a large number of shows with the dyno truck I have a fairly extensive database of results from running lots of the same model. Possibly more than many places over here. Even two or three bikes of the same model with the same exhaust can/filter combo can vary by more than 10bhp.
Keep me posted when you get your results, and I'll have a look at the data I have stored in the Dyno software, and see how they compare.

[latheboy]

When i get all the specs into the program ill post the data, then post a graph from my bike to show the differance.
I already know what the bike makes, It started out as a research thing for work to see if any of the programs are any good compaired to real life.

So far it's not real good, It reckons i should have 165HP at the wheel when the last run i did was 130HP (Dyno Dynamics HP) at the wheel which is 153 dynojet HP.

[Dynomutt]

What spec is your motor? That does seem to be a fair difference in what the app is saying to what you're actually getting.

[latheboy]

As far as I know it's stock inside, other than a new gearbox :)

749cc, T28 7PSI with cooler, retarded 4°, Ø38mm carbs, 98 RON fuel (so they say)

I'm not too worried about the program, it was just interesting to have a go.
I think it's wrong mostly because some of the inputs are not 100%.
These are things id have to strip the motor to measure.


Have you dyno'ed any similar spec'edbikes?