Freez, I just want to know how much an 87 hp hpr 800 motor (rear wheel hp) would be at the crank?... Didnt you say that was impossible.

 

Dynoguy.

I think you are misunderstanding what I am trying to say.

The 70HP superbike numbers I refer to is at 7500 RPM. The KFX was said to make max HP at 7500 RPM, and I compared that to another 750cc motor. A 750 superbike makes way more HP, but peak output is at around 12 000 RPM. The 70HP claim I made was from FMF's web site where they show the dyno of a GSX-750R. At 7500 RPM this superbike makes around 70HP, not 100HP like the KFX guys claim. This 750 carries on and makes 120HP at 12 500 RPM. What I am saying is that at 7500 RPM, no 750cc will make 100HP. To make 100HP you need way more RPM. At 12 000 RPM yes, sure, but the KFX was said to not make power at that RPM.

Have you tested this 100HP KFX on a engine dyno? Getting 48HP at the crank of a stock KFX is spot on and within tolerance of what Kawasaki claims. The missing 1 to 2HP can easily be lost due to running it at a higher room temperature or a different altitude to what Kawasaki did. You will also find that one motor will produce 48 and anther motor will make 50. To move it from 48HP to 100HP and keeping the RPM to a max of 7500 is not possible.

 

Freez Im sure Mr Hp thanks you for giviing him advice to make him faster but Im just want to know who are you building motors for and what track or hill do they run cuz I want to see your **** rock?

 

By the way good job on the Vs guys!!!!!!!! Good to see another fast thumper[img]i/expressions/face-icon-small-happy.gif[/img]

 

Guys you need to understand how the math work.

87HP with a 800cc is possible, BUT, it depends at what RPM and with what compression ratio you claim this 87HP.

At 7500 RPM with 12:1 compression 800cc's and 87HP at the rear wheels is very unlikely. With 14:1 compression pistons, race fuel, the right cams, intake and exhaust to match and you might be able to push 87 HP at the crank, but not the rear wheels. The spec as mentioned gives a VE of 92%, which is very possible.

Then let’s apply the math to the number Dynoguy claims. 92HP at 7500 with 730cc, 12:1 compression. VE shows 124%. In other words 730 X 1.24 and you get 905.2. This means that this motor breathes 905.2cc's of air per power stroke. Come on 905cc for air going thru a motor with the capacity of 730 cc ? Explain to me how you get nearly 25% more air into this motor, without a turbo? No tuned intake or velocity stack has the capability of increasing airflow to 25% more.

Then, to his claims of 107HP with an 800cc motor. I assume 7500 RPM with 12:1 compression and VE shows 131%. Meaning 800cc motor is able to flow 1050cc of air thru it. Again, how is this possible?

Even running these number with a compression of 14:1 on the 800cc motor and the figures are still to high, 113%. The higher the compression the more difficult it is to get good VE.

 

Thanks Freeze for enlightening us with our math lesson today. Now run along so we can pay attention to the real engine builder that is posting on this thread. Good day!

 

Sandbomber.

You have no idea what I do for a living. Maybe I build high performance quads, maybe I don't. For all you know I could be a bum, or maybe I am a engineer working for a superbike race team in designing their motors for them, and I ride quads for fun, hence my interest in them and spending time on this site.

Let’s assume I know a few things about air flow and where power comes from and leave it at that. Don’t believe me, why not try this for yourself. You might learn something.

Do yourself a favour and do a search on how VE works and the math around 4 stroke motors. Concentrate your search on Volumetric Efficiency, thermal efficiency, and break mean effective pressure of the engine and then do the math. It's the kind of stuff people like me use on a daily bases. There are companies out there that supply race teams with software that uses this math and they are spot on. Race teams pay millions for this software. It saves racing teams million in development cost, since they don't have to build motors and test them on a dyno to know what they can produce power wise. You can change the cam, intake, valve size and thousands of other things in the software and within seconds you know if the change was good or bad.

How many builders who build engines for quads use this software or know how to apply the math????

The math don't lie, dynos and people do!

 

Hi Freez, you didn't read what I said. Someone else guessed at 7500 RPM's. Like i said in one of my post is our big HP motors peak at low to high 8000rpm and some in the low 9000RPM range.
As for VE, there are mass produced passenger cars with better then 100% VE now. A normally aspirated engine that has a VE of only 100% is a piece of junk as far as we are concerned, now 20 years ago it was not to bad.
You are talking about street engines as well, not race motors.
ie: in 1970, Dick mann won the Dayton 200 on a 1970 CB750 with 90RWHP
Even back in 2000 the Honda RC51 1000cc V twin made 170RWHP, I forget the exact RPM but I think it was around 9500-10,000.
We Dyno all our CVT engines on our engine Dyno, it's the only way to get reall results.
Most engine don't come with anywhere near max performance from the factories.
Take a 350 Small block Chev, back in the 80's and 90's they came factory with 150HP in some application but the 355 stock car engines we and many others were building in the 90's were 700-750HP now some are over 800HP.
Have a good one.
Ray

 

I still think that this V force motor builder is trying to research and make these Vs fast for a GREAT price. Ive seen them run, they are very fast, even last years tecknology. I dont think that Fundy is trying to do anything but support the demand of the v force riders...Dont get dicouraged fundy, keep up the good work.

 

Hi Frez, yes most of the software you are talking about is pretty good on a small block chev ect. The trouble is most of the formulas used were devised 20+ years ago and alot don't apply with to days technology. Ie: with those calculations you can calculate HP with airflow of the heads, well on the V for example if you make these heads flow good on a flow bench at 15 ", well you just ruined a set of heads.
We build raps to and a real good pumpgas 740 Rap makes 64-65RWHP on our chassis Dyno and I can tell you this, it's not even in the same league as an 90HP (64RWHP) 730 V.
Ray