Re: turbocharger supercharger
Posted by shinyribs on Oct 04, 2011; 3:39am
URL: http://vintage-and-classic-hondas.81.s1.nabble.com/turbocharger-supercharger-tp3374914p3392096.html
You may be 100% right with those numbers,Samir. I have never boosted a bike of any sort. My only experience with forced induction has been on big block chevys and that one 5.0 ford we tinkered with.The rule of thumb on auto engines is 9-10 comp ratio + 10lb boost+93 octane = will live all day.Might not work out the same on such a smaller displacement engine.I want to study up on that some more.Generally when going for bigger boost numbers(on autos)you would go with a 7:1 ratio.That will allow up to 15-17 lb boost on pump gas...MAX!
Another thing needed to accurately judge eff. comp.ratio is to know the volume output of the blower.
For example,we ran a 486 cu. in. BBC with 12:1 static comp. with a 250 B&M Megablower and got 18:1 effective comp. That blower produced 250 cfm of air per revolution.
We then took that exact same motor,installed an 8-71 GMC style blower and got the same eff. comp. ratio,but turned the blower alot slower and ran much faster.The 8-71 produces about 600-650 cfm per revolution.
By turning the bigger blower slower,but still producing the same/more cfm of air per rev.,we eliminated excess pulsations in the intake tract,less heat generated by not compressing the air as hard,and loss parasitic drag by turning lower blower rpms. At the track the car went from 5.20's to 4.80's with ONLY a blower change.It equates to roughly a 300-350 hp increase by using a more efficient setup,even though boost was exactly the same.
It is impossible to estimate effective compression without talking to the blower or turbo manufacturer themselves.We talked to B&M when we used their blower ,and Littlefield when we used their 8-71.They had to know cubic inch,elevation(like you said),intended rpm of engine and intended rpm of the blower to calculate it.I would have a hard time trusting any chart to figure those numbers without all the info being factored in.But that is strictly opinion on my part.I will not preach opinion as fact.
There are so many factors that affect effective compression other than boost or piston design.Camshaft profile is the biggest one.The more duration the cam has,the more cylinder pressure it will bleed off at lower rpm operation.That is why you see race cars,with their monster cams,running huge compression ratios.Its not so much that it actually produces more power(very little really.roughly 3% increase per point of compression)but that it helps restore lost bottom end torque due to a very inefficient camshaft profile.
Again,i know nothing of the cams on these bikes,but i would assume they have a rather tight cam profile.I assume this due to the good bottom end torque they produce and the good fuel mileage they achieve.
I'm not leaving until they make me.Hope to see you around,too.Ride safe!BTW,picking my brain is about as effective as picking your nose...alot of stuff in there,but most likely worthless
URL: http://vintage-and-classic-hondas.81.s1.nabble.com/turbocharger-supercharger-tp3374914p3392096.html
You may be 100% right with those numbers,Samir. I have never boosted a bike of any sort. My only experience with forced induction has been on big block chevys and that one 5.0 ford we tinkered with.The rule of thumb on auto engines is 9-10 comp ratio + 10lb boost+93 octane = will live all day.Might not work out the same on such a smaller displacement engine.I want to study up on that some more.Generally when going for bigger boost numbers(on autos)you would go with a 7:1 ratio.That will allow up to 15-17 lb boost on pump gas...MAX!
Another thing needed to accurately judge eff. comp.ratio is to know the volume output of the blower.
For example,we ran a 486 cu. in. BBC with 12:1 static comp. with a 250 B&M Megablower and got 18:1 effective comp. That blower produced 250 cfm of air per revolution.
We then took that exact same motor,installed an 8-71 GMC style blower and got the same eff. comp. ratio,but turned the blower alot slower and ran much faster.The 8-71 produces about 600-650 cfm per revolution.
By turning the bigger blower slower,but still producing the same/more cfm of air per rev.,we eliminated excess pulsations in the intake tract,less heat generated by not compressing the air as hard,and loss parasitic drag by turning lower blower rpms. At the track the car went from 5.20's to 4.80's with ONLY a blower change.It equates to roughly a 300-350 hp increase by using a more efficient setup,even though boost was exactly the same.
It is impossible to estimate effective compression without talking to the blower or turbo manufacturer themselves.We talked to B&M when we used their blower ,and Littlefield when we used their 8-71.They had to know cubic inch,elevation(like you said),intended rpm of engine and intended rpm of the blower to calculate it.I would have a hard time trusting any chart to figure those numbers without all the info being factored in.But that is strictly opinion on my part.I will not preach opinion as fact.
There are so many factors that affect effective compression other than boost or piston design.Camshaft profile is the biggest one.The more duration the cam has,the more cylinder pressure it will bleed off at lower rpm operation.That is why you see race cars,with their monster cams,running huge compression ratios.Its not so much that it actually produces more power(very little really.roughly 3% increase per point of compression)but that it helps restore lost bottom end torque due to a very inefficient camshaft profile.
Again,i know nothing of the cams on these bikes,but i would assume they have a rather tight cam profile.I assume this due to the good bottom end torque they produce and the good fuel mileage they achieve.
I'm not leaving until they make me.Hope to see you around,too.Ride safe!BTW,picking my brain is about as effective as picking your nose...alot of stuff in there,but most likely worthless
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