Topic: free virtual race tune dyno

[turboguzzi]

Quite busy working on my gpz750/810 project's motor, trying to figure out a strategy for improvements. So, while doing some searches I came across this performance calculator done by a US race car tuner.
 
http://www.schmidtmotorworks.com/enginedesigner.aspx
 
Tried to insert there the parameters of my CB500 race motor and wow! the final HP number (62hp) really matches my dyno readings! So sounds like its a pretty realisitc calculator at least for well develepod RACE motors. It even predicted quite well the rpm's for peak torque and peak HP which are indeed, pretty low for such a small stroke engine but that also what my dyno runs showed. 
 
The only parameters you can enter are in the white areas, the SW will fill by itself the missing ones.
 
I think that for a stock street motor with stock manifolds, air filter etc. the results are going to be quite unrealistic as its hard to figure out the flow losses all around but for tuned motors that have work done on them, it seems to really work.
 
As i expected, the most dominant factor that limits a 500's hp is inlet valve/throat size. change those and the HP and revs jump up
 
If anybody has other dyno readings and racing engine parameters it'll be intersting to see how these match reality.
 
BTW, the calculator predicts 102 hp for my 810... yummie

[gnarlycharlie4u]

this is pretty cool. i'm mesmerized and will probably get no work done today. thanks.

[bwaller]

Yea TG, I played with this when you posted before, pretty neat.

What kind of juice does the stocker make? I expect 102 must be quite a jump.

[turboguzzi]

Yea TG, I played with this when you posted before, pretty neat.

What kind of juice does the stocker make? I expect 102 must be quite a jump.

they seem to have around 70 rwhp stock if in good condition. cycle mag dynoed at 69 back at the time i reckon

[bwaller]

A good increase indeed but completely believable considering a CB500 jump from 38ish to 62ish.

[mec]

it must have been in the 80ies, when two of my friends raced those Z650. the engines had termignoni 850ccm and termignoni cams, ported head and 29mm smoothbore mikunis. these bikes were as fast as my 1000ccm sohc.

mec

[turboguzzi]

it must have been in the 80ies, when two of my friends raced those Z650. the engines had termignoni 850ccm and termignoni cams, ported head and 29mm smoothbore mikunis. these bikes were as fast as my 1000ccm sohc.

mec

Interesting mec, would like to hear more. After all, the gpz750 motor is just a slightly updated 650 motor.

This is more or less what I am building too, I even managed to find a termignoni exhaust but didnt know they made also 850 kits and cams.

got hold of some andrews cams though.

With a shorter stroke of 54mm and relatively big 34mm valves (50% of the 69mm bore) a 750/810 has quite high rpm potential. In fact, that calculator gave me a peak hp rpm of 9500, just like for my 500 with only 50mm stroke!

[mlinder]

Yow, this thing tells me, on one of my cb350t builds, that peak HP is at 12k rpm, peak torque is at 10k rpm, and that I shouldn't get any cam with more duration than about 250 degrees (at .5"), though it's suggested lift is about 20% higher than what's available, so the extra duration may help. Good thing this is built to handle about 13.5k rpm :/

We'll see what the dyno says.

[turboguzzi]

sounds like something is wrong/missing with the data you entered as the revs are very high

the 810 data i entered might be closer to your 350 in terms of bore/valve size and still it wont give 12K as peak hp rpm.

what's the valve size in a 350?

[mlinder]

Well this here's what I got, TG.

Some of these are close guesses trying to remember what Mike told me about the head.

Maybe he can remember and correct me.

In any case, it seems a bit... optimistic...

[mlinder]

I reckon this thing is at least 20% optimistic, which prolly means your 102hp 810 is prolly more like 85hp

It was about 20% optimistic for stock 350t output, too, and as I said, I figured 40 to 43 rwhp for this particular build, it's putting me at 60 crank, which is 20%ish more than the 49-50 I was figuring at crank.

Neat piece of software.

[turboguzzi]

well, like i said, it was spot on on my 500, gave 62, exactly what i got on the dyno and at exactly the right rpm's too.
Agree with you that almost the same power output from a 350 twin looks  optimistic . That's why i am saying that you might have gotten one of the parameters wrong.

if it gave me 102 hp for a 810cc four, then a 400 twin  should be round 50hp, round 44 for a 350 .... which is about what  i heard about people getting from good K4's.

so let me check your numbers a bit, your inlet valve looks already too big to me at 36mm.... a gpz750's is 34mm by comparison

TG

[mlinder]

Well, mine is 36mm, not 34

Stock is 35mm. I'm one bigger.

[turboguzzi]

Well, mine is 36mm, not 34

Stock is 35mm. I'm one bigger.

glad for you, wish i had 36's m valves .... Rob Muzzy used 35's in his 750's on 66 bores, so yours are certainly huge.

and are you sure you are opening up the minimum throat size to 91% of 36mm? That's quite extreme. If so you should be able to measure something like internal diameter 32.76mm at the narrowest point of the port near or at the valve seat . check it out

From my checks, the program is quite sensitive to valve size and % of minimum throat diameter to valve size parameters. 85% is a much more common number.



TG

 

[mlinder]

I seem to remember it being something like that. Mike told me, but I only sorta remember. I'll measure it on Saturday.

85% puts me at a more reasonable 10.5k peak hp of 55.

Still a bit optimistic, imo, considering I've got stock cam there...

[turboguzzi]

ok, i think i found the problem

the software automatically put a very optimisitc/unrealistic 167 CFM @ 28", a number that is way too high.

If you correct the port speed for a more resonable 105 cfm, you get exactly 45 ponies

Ask Mike what kind of CFM he was getting from that port, adjust the speed to get that number and the result will be pretty spot on.

Of course, assuming you have a proper race cam in there!

On the other hand, why do this extreme porting and increase in valve size with a stock cam? doesnt make much sense to me...

[turboguzzi]

and the 810 parameters corrected....

now its left to see if ill manage to get  105 CFM too with my porting job

The GPZ ports are pretty good to begin with, it will not be easy to improve flow compared to the CB500

I am starting to build a flowbench this weekend, hopr to dyno in three weeks, should be fun finding out if science meets reality....

TG

[mlinder]

Mostly because we aren't sure which cam is going to benefit Jons riding style yet. A little time with a stock cam can tell us what he wants more of, and what he doesn't want to lose.

Both top end and bottom end are good for some pretty astronomical RPMs (for being a 40 year old 2 cylinder) but if Jon doesn't want a powerband that is only between 11 and 12.5k, we need to figure that out before dropping 500 bucks on a cam.

My guess is he's going to want something a little more mild, he's used to racing a big low-end power bike.

[mlinder]

What is the unit for throat velocity? FPM? IPS? MPH? KP..whatever?

'Cus my math is telling me that, in a perfect world (no obstructions, which obviously isn't true) one piston would be pulling in 4950 cubic inches per minute at 9000rpm.

With a diameter of 30mm in the throat, this gives something like 375 feet per minute velocity in said throat.

Of course, like I said, this isn't right for a lot of reasons. One being, of course, that the airflow is blocked pretty often by the intake valve closing, the other that the intakes are far from perfect.

I'm just not sure what the engine calculator is measuring, nor am I able to quantify actual velocity with things 4 stroke engines need, like, valves, and stuff.

[turboguzzi]

feet per minute,

from what i gather, most important for power is the CFM, i.e. the actual flow into the cyl, so best to adjust the speed so the CFM parameter is about what you know to be true from flowbench testing/rumors. fpm doesnt make power, cfm does..

For instance, from a Kawasaki tuner i heard that the stock GPZ ports give about 75-80 CFM so improving to about a 100 CFM is a reasonable target (if you know what you are doing)

If my experience with megacycle's 126-20 is anything to go by, you are worrying too much... power on my CB500/4 is pretty good from 7K onwards, it peaks at 9.5K-10K and that's with 125 cc cyls. Cant see your 175cc cyls. peaking at 11-12K, no way. 

[mlinder]

feet per minute,

OK, kinda thought so, which is why I used that in my 'calculations' above.

from what i gather, most important for power is the CFM, i.e. the actual flow into the cyl, so best to adjust the speed so the CFM parameter is about what you know to be true from flowbench testing/rumors. fpm doesnt make power, cfm does..

There's a lot of back and forth on this. Obviously, being able to flow enough to fill the cylinder is very important. However, air has mass, and the faster it goes, the more inertia it has. The more inertia it has, the longer it will be trying to fill up the cylinder, even as the piston begins to rise. Done correctly, a higher velocity will, theoretically, shove more air and fuel into a cylinder than a higher CFM, lower velocity port will. But this is me bench-racing with information gleaned from experienced builders like Mike, Mark, etc.

For instance, from a Kawasaki tuner i heard that the stock GPZ ports give about 75-80 CFM so improving to about a 100 CFM is a reasonable target (if you know what you are doing)

It'll be interesting to see what we have. Mr Rieck did what appears to be a bang-up job on this head, and in comparison to my i4's, everything is pretty damned huge.

If my experience with megacycle's 126-20 is anything to go by, you are worrying too much... power on my CB500/4 is pretty good from 7K onwards, it peaks at 9.5K-10K and that's with 125 cc cyls. Cant see your 175cc cyls. peaking at 11-12K, no way. 

Stroke is the same, more oversquare, and more flow. Who's to say? We'll see In any case, Jon will prolly want a little smoother powerband. Then again, I'll be paying for the cam, so it's sorta up to me