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Author Topic: max horsepower out of a 1397?  (Read 28910 times)

Offline PetriK

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Re: max horsepower out of a 1397?
« Reply #50 on: May 03, 2008, 08:56:39 AM »
Quote
Ah ok, its estimated then.  I have measured coast down losses but even then i don't think its accurate enough.

Yes - what alternatives to coastin losses we have ???

I think I will go through the dyno calibration process just to understand why so much lower figures on this dyno than local dj250's. I believe that the dyno manufacturers would know the answes - maybe someone should ask from dynojet and from factorypro why so big differences ... ?

Air density is not an issue as it is fundamental to drag and part of the calculation.

Rather meant that its info very seldom logged to give comparable figures. Quarter mile trap speed is something for which a lot of data is avail on time slips ...



Offline enginetuna

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Re: max horsepower out of a 1397?
« Reply #51 on: May 03, 2008, 09:43:09 AM »
I've asked factory pro and dynojet and they both say the other is an idiot and completely wrong.   :(

The latest race tyres are a complete pain in the ass.  The don't show huge drag on coast down as they do on hard acceleration.  Rate of sweep shows differences also.  Even on a 600 you can see 6bhp between a bunch of them.  Doesn't matter what brand of dyno.  A dunlop 16.5" slick on a superbike 2 years ago was guaranteed 15+bhp down on a touring tyre.  Latest ntec slicks are about 5-8bhp down depending on compound.

Any of you drag race guys spotted bhp losses with race versus road rubber on dyno?  Or do you all use road rubber at low pressure?  I'm dumb to the world of drag racing if that sounds like a squid question.

Offline PetriK

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Re: max horsepower out of a 1397?
« Reply #52 on: May 03, 2008, 10:07:10 AM »
I've asked factory pro and dynojet and they both say the other is an idiot and completely wrong.   :(

Or do you all use road rubber at low pressure? 

That answer from both parties as it really explains everything ... I really would like to hear what is the truth as calculating HP is very easy if we look at basic physics. The dyno calibration is also based on laws of physics so the differences are coming from different formulas inside the dyno software.

On this particular dyno always 1.5bar (25psi ?) pressure for road rubber is used. Prevents slippage and gives more consistent coastdown (learned a new English word today ;-)


Offline mike46

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Re: max horsepower out of a 1397?
« Reply #53 on: May 03, 2008, 03:28:39 PM »
I've asked factory pro and dynojet and they both say the other is an idiot and completely wrong.   :(

The latest race tyres are a complete pain in the ass.  The don't show huge drag on coast down as they do on hard acceleration.  Rate of sweep shows differences also.  Even on a 600 you can see 6bhp between a bunch of them.  Doesn't matter what brand of dyno.  A dunlop 16.5" slick on a superbike 2 years ago was guaranteed 15+bhp down on a touring tyre.  Latest ntec slicks are about 5-8bhp down depending on compound.

Any of you drag race guys spotted bhp losses with race versus road rubber on dyno?  Or do you all use road rubber at low pressure?  I'm dumb to the world of drag racing if that sounds like a squid question.
Holy crap that's a lot of loss for tire. I could see if you had a car tire on the bike but???
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Offline enginetuna

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Re: max horsepower out of a 1397?
« Reply #54 on: May 03, 2008, 04:21:05 PM »
Its a total pain in the ass Mike.  I build a race motor for someone and they bring the bike in for dyno with a bad reading tyre. They think they've been screwed over.  Its a major problem with the modern race tyre.
I tested a pirelli super corsa tyre against a dunlop qualifier last year on suzuki 750.  Within 10 mins then back again to confirm.  Both popular road tyre.  11bhp difference.  Everyone i know who takes the time to notice these things has the same issues, its not a one dyno problem. I've got a chart from dynojet showing 16bhp loss on a cbr1000rr within 10 mins also.
Its the same on a busa too so you guys better beware!!

Offline SPARKY1397R

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Re: max horsepower out of a 1397?
« Reply #55 on: May 03, 2008, 04:43:07 PM »
the race compound tires showing a big loss on the dyno is pretty well known,  especially the shinkos

Offline DarkFalcon

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Re: max horsepower out of a 1397?
« Reply #56 on: May 03, 2008, 06:17:41 PM »
Its a total pain in the ass Mike.  I build a race motor for someone and they bring the bike in for dyno with a bad reading tyre. They think they've been screwed over.  Its a major problem with the modern race tyre.
I tested a pirelli super corsa tyre against a dunlop qualifier last year on suzuki 750.  Within 10 mins then back again to confirm.  Both popular road tyre.  11bhp difference.  Everyone i know who takes the time to notice these things has the same issues, its not a one dyno problem. I've got a chart from dynojet showing 16bhp loss on a cbr1000rr within 10 mins also.
Its the same on a busa too so you guys better beware!!

ET, are there weight differences between the compounds/tires?

Offline mike46

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Re: max horsepower out of a 1397?
« Reply #57 on: May 03, 2008, 09:10:26 PM »
Its a total pain in the ass Mike.  I build a race motor for someone and they bring the bike in for dyno with a bad reading tyre. They think they've been screwed over.  Its a major problem with the modern race tyre.
I tested a pirelli super corsa tyre against a dunlop qualifier last year on suzuki 750.  Within 10 mins then back again to confirm.  Both popular road tyre.  11bhp difference.  Everyone i know who takes the time to notice these things has the same issues, its not a one dyno problem. I've got a chart from dynojet showing 16bhp loss on a cbr1000rr within 10 mins also.
Its the same on a busa too so you guys better beware!!

ET, are there weight differences between the compounds/tires?
If anything race tires are lighter than street. My experience. May be different now.
« Last Edit: May 03, 2008, 09:12:06 PM by mike46 »
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Offline Jonny Hotnuts

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Re: max horsepower out of a 1397?
« Reply #58 on: May 03, 2008, 11:02:55 PM »
In our car we ran 143 rwhp....you can imagine I was pissed considering we had a cold cam on the hot side, PC, yosh header......
The same motor, same day in the bike made 166 (zero map) with nothing else done except it was spinning 1 tire and 2 bearing and not 2 tires 4 bearings and 2 CVs.

That is a difference of 23 hp loss, true our axles were not dead in line causing loss in the CVs….but damn…. 143 from 166!
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Offline enginetuna

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Re: max horsepower out of a 1397?
« Reply #59 on: May 04, 2008, 03:10:07 AM »
ET, are there weight differences between the compounds/tires?

Yes but its not just a weight issue.  If i tested loaded instead of inertia it levels it out much more but there is still a rubber issue.  Its like some of the rubber sucks down hard and some doesn't.

Offline PetriK

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Re: max horsepower out of a 1397?
« Reply #60 on: May 04, 2008, 03:58:49 AM »
ET, are there weight differences between the compounds/tires?

Yes but its not just a weight issue.  If i tested loaded instead of inertia it levels it out much more but there is still a rubber issue.  Its like some of the rubber sucks down hard and some doesn't.

Do you measure the tyre slippage by comparing wheel RPM to Tach signal RPM ?


Offline enginetuna

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Re: max horsepower out of a 1397?
« Reply #61 on: May 04, 2008, 04:06:12 AM »
Yes.  Winpep has a gear ratio option.  The is comparing the 2 rpms.  You can see slippage easily with this.  Can also check coastdown easily

Offline peanuthead

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Re: max horsepower out of a 1397?
« Reply #62 on: May 04, 2008, 09:04:21 PM »
Just to throw my two cents in,what about when the dyno drum wheel has some or all of the rubber nurling gone on it.Would that affect the reading?

Offline whtrthanu

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Re: max horsepower out of a 1397?
« Reply #63 on: May 04, 2008, 09:16:14 PM »
the only way that could change readings would be of the drum lost weight...The readings would be lower than normal........

Offline peanuthead

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Re: max horsepower out of a 1397?
« Reply #64 on: May 04, 2008, 09:32:08 PM »
wouldnt the tire slip with some or all of the rubber nurling gone on the dyno drum

Offline whtrthanu

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Re: max horsepower out of a 1397?
« Reply #65 on: May 04, 2008, 09:37:04 PM »
it might slip, but the dyno reads engine rpm and tire speed at the same time......he graph will show a break in it usually if the tire slips......

Offline enginetuna

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Re: max horsepower out of a 1397?
« Reply #66 on: May 05, 2008, 03:44:05 AM »
wouldnt the tire slip with some or all of the rubber nurling gone on the dyno drum

When the knurling gets really worn you end up pulling the straps down a bit tighter.
There is always some slip, its just about keeping it to a minimum.
For those of you who are not too familiar with slip on the dyno, this may help you to understand.

Here is a good example.
This is a k6 1000. Look at the dates and times at the top. It is 6 successive roll-ons on a cold tire.
The left hand graph is you normal power graph and the right hand one is the tire slip graph.
But if you change to a low reading tyre the slip graph does not change.  It really is not a measurable thing how much the rubber sticks to the roller.


Offline peanuthead

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Re: max horsepower out of a 1397?
« Reply #67 on: May 05, 2008, 11:27:21 PM »
tuna,it seems to me is that you get less slippage with a warm tire on the dynoe drum,if Iam reading the grapf correctly.

Offline Steve S

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Re: max horsepower out of a 1397?
« Reply #68 on: May 06, 2008, 10:28:34 AM »
the only way that could change readings would be of the drum lost weight...The readings would be lower than normal........

?????????