Jets vs Exhaust
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Graham
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Assuming Graham has learned something in "27 years of motorcycle repair" (yet another one of his unqualified statements) ,
then there is probably (a qualification of my thesis) some rational reason for his statement. I think I know what it is; the question is does he know what it is and can he articulate it?
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Maybe it's 27 years of selling pipes with bogus claims about horsepower increases.Comment
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Graham
I remember back in the day, a GS1100 on the dyno pushing 127hp stock with a Yoshimura header. A stock GPZ750 turbo running 130hp with a Kerker system. My stock 77 KZ650 ran 78hp with a Mac and a missing air filter. Back in the 80s aftermarket exhaust manufactures claimed 15 to 20% increase in hp (witch was true). The other 5% I guessed from the pods increased airflow. If you don?t find any validity in my statements then don?t get a header system.Comment
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Graham
Restrictive factory exhaust system changed to a free flowing system that will scavenge the exhaust gasses. More exhaust gas out means more fuel mix in which equals more CFM. Gee bigger valves and a performance cam will do that too, more CFM. Does more CFM in and out of motor equal more HP?Comment
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I think something must be fading ....................I remember back in the day, a GS1100 on the dyno pushing 127hp stock with a Yoshimura header. A stock GPZ750 turbo running 130hp with a Kerker system. My stock 77 KZ650 ran 78hp with a Mac and a missing air filter. Back in the 80s aftermarket exhaust manufactures claimed 15 to 20% increase in hp (witch was true). The other 5% I guessed from the pods increased airflow. If you don’t find any validity in my statements then don’t get a header system.
Here is a thread that will give you an idea of what it takes to add 25% to a stock 1100. It is alot more than a Yoshi pipe.
Technical Info posts that are deemed to be important or popular will be placed here for easier access. If you feel a post should be moved from the Technical Info forum to here then PM the Administrator with your request.
So do you still claim that just a Yoshi pipe will give 15% increasein hp????Comment
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No, he never claimed 15% increase, he claimed 25%.
All true, that's how it works. I have put pipes on a lot of my bikes, they usually go a little better.Restrictive factory exhaust system changed to a free flowing system that will scavenge the exhaust gasses. More exhaust gas out means more fuel mix in which equals more CFM. Gee bigger valves and a performance cam will do that too, more CFM. Does more CFM in and out of motor equal more HP?
Pods too, sure a little better on top once the jetting is figured out. I never said I didn't like them. I just said it's not going to get 25% more.Comment
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Graham
15 to 20% over stock with the right jetting. The bike in the thread is not stock and as should know one mod can take away from another.I think something must be fading ....................
Here is a thread that will give you an idea of what it takes to add 25% to a stock 1100. It is alot more than a Yoshi pipe.
Technical Info posts that are deemed to be important or popular will be placed here for easier access. If you feel a post should be moved from the Technical Info forum to here then PM the Administrator with your request.
So do you still claim that just a Yoshi pipe will give 15% increasein hp????
If you read back I first said about 25% for header + pods + jetting. I also said I guessed at 5% for the airflow incraese of the pod filter which left about 20% for the header.
Now if you or tkent02 are unable to get about 25% from your good header + good pods + jetting on a stock GS you just bring it down here to Florida and I'll show you how.
The nitpicking is getting no where.Last edited by Guest; 11-22-2010, 12:35 AM.Comment
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Surely in 27 years someone has put one of these bikes on a dyno, before and after? 6%, maybe 8%?
Maybe 10% gain from opening up a real corked up dog?
That's all we need. Some dyno results.
Real numbers on a real bike.
Let's see it.Comment
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Graham
That was like 84 or 85 and by 87 the stock exhaust was getting so close to aftermarket header performance you could no longer get double digit %HP from a header. The GS, KZ, CB and XJ were the last to get the big HP from the header.Comment

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