HPInc TB flow numbers

[ThumperDeuce]

I spoke with HPInc. today to try and get some flow numbers.  They told me that the 58/62 flowed at about 335 cfm at 10" and would support around 170hp.  The 62mm flows about 40 cfm more and supports 200+ hp.

[TorQuePimp]

    I don't think they flow that much @ 10"

[ThumperDeuce]

That is their claim.

[TorQuePimp]

  I think you mean @ 28"

[Merc63]

So anything over 62mm is useless? Why does SnS have these large bore throttle hogs??

Thought HPI was coming out with a 70mm...  Maybe they are talking crank HP?

[No Cents]

 

[ThumperDeuce]

When I heard him say 10" I actually asked 2 more times to confirm.  I also asked if they had any plans on building a tb larger than 62mm in the near future.  He said that they had made a 70mm that one time but that they do not have any plans to do that again.  I run a 58/62 on my Deuce.  I may bump up my compression next year.  So the next time it comes off I'll probably go ahead and have it flowed.  It will be a sad thing if they are blowing smoke.

[Deye76]

They're pretty straight forward folks (HPI), was it a tech person you spoke with?

[ThumperDeuce]

Well, I asked the lady who answered the phone if I could speak with someone who could answer a technical question about their throttle bodies.  It took a couple of minutes for the guy to get to the phone.  I did't get a name.  I hope he wasn't the UPS guy.

[Deye76]

LOL

[HD/Wrench]

The flow numbers are at 28 not 10  They make a great product .

[strokerjlk]

So anything over 62mm is useless? Why does SnS have these large bore throttle hogs??

Thought HPI was coming out with a 70mm...  Maybe they are talking crank HP?

Because S&S knows that bigger always sells.
It's a win win . They have some motors that benefit from the huge hogs .
And they can sell to the street crowd , that thinks bigger is always better .

[Hillside Motorcycle]

When I heard him say 10" I actually asked 2 more times to confirm.  I also asked if they had any plans on building a tb larger than 62mm in the near future.  He said that they had made a 70mm that one time but that they do not have any plans to do that again.  I run a 58/62 on my Deuce.  I may bump up my compression next year.  So the next time it comes off I'll probably go ahead and have it flowed.  It will be a sad thing if they are blowing smoke.

We had on of their 70's here years ago, when we were setting up a Daytona HP Shoot-Out engine for one of their former employees.
It was equipped with a beautiful(HUGE!!!) air horn, that actually threaded on to the t/body.
Scott

[Admiral Akbar]

I've measured a 57mm Wild things throttle body and got 303 cfm corrected to 10 inches. It wouldn't surprise me that a bigger one would get more.. The problem is that it need to be fit to a manifold that has a 41 to 46 mm port size.. When you do they flow drops to the 200 cfm range or less. It's nice to have a TB that has a larger than port sized bore since the butterfly kills flow but after some value the bigger TB does not do anything except make the bike harder to ride at partial throttle settings.

Of course if you want bragging rights,since many don't realize port is the limiting factor and all you ever to is run it wide open.. Get the biggest there is and put the numbers on the back of your laminated dyno run that you keep in your wallet..

If you plan to increase the port size to 1.9 - 2 inches and have heads that support the flow.. Go for it..

Max

[dynoharley]

I've measured a 57mm Wild things throttle body and got 303 cfm corrected to 10 inches. It wouldn't surprise me that a bigger one would get more.. The problem is that it need to be fit to a manifold that has a 41 to 46 mm port size.. When you do they flow drops to the 200 cfm range or less. It's nice to have a TB that has a larger than port sized bore since the butterfly kills flow but after some value the bigger TB does not do anything except make the bike harder to ride at partial throttle settings.

Of course if you want bragging rights,since many don't realize port is the limiting factor and all you ever to is run it wide open.. Get the biggest there is and put the numbers on the back of your laminated dyno run that you keep in your wallet..

If you plan to increase the port size to 1.9 - 2 inches and have heads that support the flow.. Go for it..

Max

hi max I to have been spending time with known head , and what they  flow,  and trying out different  manifolds throttle bodys ect here in down under ,and port cross section is always a killer , funny how whats in front of valve etc knocks it down ay , the saying big is better thems to work in the movies but not in this secta LOLO, cheers

[Hillside Motorcycle]

Bigger is not always better no doubt, but running the proper size for the intended application.
Scott

[ThumperDeuce]

Ok, help me understand the intake system a little more.  I'll use my 58/62 for an example.  The claim is that it flows 335 cfm at 10".  So in the 58 mm part of the throttle body the flow would be faster.  It hits the 62mm plenum expands and slows but builds up a reservoir of air.  It goes into the 1.8" runner gets squeezed and accelerates.  As it hits the closed intake valve all kinds of funky stuff happens to the airflow.  Then it fills the cylinder.  The fill is measured by volumetric efficiency?  Right now I've got a 2.1" intake valve and my heads flow 308 cfm @ .700 lift measured at 22".  If you do as Max says and open up the intake do you risk slowing the airflow and decrease the VE or does the decreased velocity get offset by an increase in volume?  Is this where the magic happens to get the maximum fill?  To get the final flow going into the cylinder head do you ultimately have to measure what is coming out of the runner with the throttle body and air filter assembled in its final configuration.  I was talking to Otto the other day and he was saying that you can tell by the MAP sensor readings where the tb starts to show its limits.

This all comes from trying to find the smallest tb necessary to get the maximum power that my engine configuration will produce.  This has to do with the drivability characteristics of the engine at the intermediate throttle positions that Max was talking about.  Right now I think that the 58/62 is supporting my heads, cr and cam OK.  My exhaust system may not be optimal.  I am going to go into the engine one more time.  I've got Burns designing me an exhaust to go with a TW68G cam with a cr of 12.3:1 and I am trying to get a feel for whether or not I am going to have to increase my throttle body size.

[TorQuePimp]

335@10" is around 550 cfm @ 28"

  There is software to calculate how large both the runners and blade size should be but it doesn't always work out like the software says it should.

Best way to find out is to test the throttle body you have and try and borrow another larger one or buy one and do some bench testing of both flow and velocity and find a balance between the two.....if the airspeed gets too low,you went to large and in most cases it will be a right sided monster no matter how many cams you stuff in it.

[Merc63]

Ok, help me understand the intake system a little more.  I'll use my 58/62 for an example.  The claim is that it flows 335 cfm at 10".  So in the 58 mm part of the throttle body the flow would be faster.  It hits the 62mm plenum expands and slows but builds up a reservoir of air.  It goes into the 1.8" runner gets squeezed and accelerates.  As it hits the closed intake valve all kinds of funky stuff happens to the airflow.  Then it fills the cylinder.  The fill is measured by volumetric efficiency?  Right now I've got a 2.1" intake valve and my heads flow 308 cfm @ .700 lift measured at 22".  If you do as Max says and open up the intake do you risk slowing the airflow and decrease the VE or does the decreased velocity get offset by an increase in volume?  Is this where the magic happens to get the maximum fill?  To get the final flow going into the cylinder head do you ultimately have to measure what is coming out of the runner with the throttle body and air filter assembled in its final configuration.  I was talking to Otto the other day and he was saying that you can tell by the MAP sensor readings where the tb starts to show its limits.

This all comes from trying to find the smallest tb necessary to get the maximum power that my engine configuration will produce.  This has to do with the drivability characteristics of the engine at the intermediate throttle positions that Max was talking about.  Right now I think that the 58/62 is supporting my heads, cr and cam OK.  My exhaust system may not be optimal.  I am going to go into the engine one more time.  I've got Burns designing me an exhaust to go with a TW68G cam with a cr of 12.3:1 and I am trying to get a feel for whether or not I am going to have to increase my throttle body size.

How exactly can you tell by MAP read out where the limit is if it exists?

[gordonr]

It seems to me by keeping the plenum bore and throttle plate smaller, its as though you are trying to get as close to an individual port setup  as possible but without the advantages of the "wave action" the intake port would make if it was an IR. Curtis Boggs, head and intake designer told me "you have to make the air happy" and having super high velocity around the throttle plate doesn't make the air happy and that the port in the head needs to draw from a calm non turbulent air. Tall orders for a vtwin.

[HD/Wrench]

As stated you can play the  program game and it may lead you into the right direction. If the program has data that has been proven and tested in the real world.  Flow the entire set upon the bench. Test borrow parts to see how they work. A wet bench would be the outstanding for this testing. Use clay to alter manifold or intake port, you may find something there as well..  Unless this complete set has been done you are testing in new waters.  

But it will be some trial and error.  Use of a spin tron for the cam would be very helpful with the heads. It may be the cam or you may find another cam is much more suite for your current heads you have.  If you start the testing I would like to see what you come up with.   

[strokerjlk]

Ok, help me understand the intake system a little more.  I'll use my 58/62 for an example.  The claim is that it flows 335 cfm at 10".  So in the 58 mm part of the throttle body the flow would be faster.  It hits the 62mm plenum expands and slows but builds up a reservoir of air.  It goes into the 1.8" runner gets squeezed and accelerates.  As it hits the closed intake valve all kinds of funky stuff happens to the airflow.  Then it fills the cylinder.  The fill is measured by volumetric efficiency?  Right now I've got a 2.1" intake valve and my heads flow 308 cfm @ .700 lift measured at 22".  If you do as Max says and open up the intake do you risk slowing the airflow and decrease the VE or does the decreased velocity get offset by an increase in volume?  Is this where the magic happens to get the maximum fill?  To get the final flow going into the cylinder head do you ultimately have to measure what is coming out of the runner with the throttle body and air filter assembled in its final configuration.  I was talking to Otto the other day and he was saying that you can tell by the MAP sensor readings where the tb starts to show its limits.

This all comes from trying to find the smallest tb necessary to get the maximum power that my engine configuration will produce.  This has to do with the drivability characteristics of the engine at the intermediate throttle positions that Max was talking about.  Right now I think that the 58/62 is supporting my heads, cr and cam OK.  My exhaust system may not be optimal.  I am going to go into the engine one more time.  I've got Burns designing me an exhaust to go with a TW68G cam with a cr of 12.3:1 and I am trying to get a feel for whether or not I am going to have to increase my throttle body size.

How exactly can you tell by MAP read out where the limit is if it exists?

you cant tell exactly,where the limit exists. ( T/B to exhaust tip somewhere)  but you know something is limiting .
this is where it gets interesting ,and experience pays off. could be T/B, could be heads , could be exhaust .

[TXChop]

fwiw, I ran the 62 mm when i had the tw68's in my 117. It was a bit twitchy on tip in throttle. I did get used to it mostly. Lots of clutch control helps.

I went with a 55mm on my 124 and coulndt be any happier.

[Hillside Motorcycle]

We've used the HPI 62 on 117"/S&S .640 combo's a couple times now.
Seems to work well from what the clients have told us.
Scott

[ThumperDeuce]

Ok, help me understand the intake system a little more.  I'll use my 58/62 for an example.  The claim is that it flows 335 cfm at 10".  So in the 58 mm part of the throttle body the flow would be faster.  It hits the 62mm plenum expands and slows but builds up a reservoir of air.  It goes into the 1.8" runner gets squeezed and accelerates.  As it hits the closed intake valve all kinds of funky stuff happens to the airflow.  Then it fills the cylinder.  The fill is measured by volumetric efficiency?  Right now I've got a 2.1" intake valve and my heads flow 308 cfm @ .700 lift measured at 22".  If you do as Max says and open up the intake do you risk slowing the airflow and decrease the VE or does the decreased velocity get offset by an increase in volume?  Is this where the magic happens to get the maximum fill?  To get the final flow going into the cylinder head do you ultimately have to measure what is coming out of the runner with the throttle body and air filter assembled in its final configuration.  I was talking to Otto the other day and he was saying that you can tell by the MAP sensor readings where the tb starts to show its limits.

This all comes from trying to find the smallest tb necessary to get the maximum power that my engine configuration will produce.  This has to do with the drivability characteristics of the engine at the intermediate throttle positions that Max was talking about.  Right now I think that the 58/62 is supporting my heads, cr and cam OK.  My exhaust system may not be optimal.  I am going to go into the engine one more time.  I've got Burns designing me an exhaust to go with a TW68G cam with a cr of 12.3:1 and I am trying to get a feel for whether or not I am going to have to increase my throttle body size.

How exactly can you tell by MAP read out where the limit is if it exists?

I don't know.  It was a comment he made.  It takes me a couple of times hearing this stuff and then a lot of thought for it to make sense sometimes.  I think it has something to do with the pressure dropping off.  If I get to the point where I understand it more I'll make a further comment.  I try not to bug Otto too much.  He has been exceptionally tolerant with my questions and the stuff I have him do to my scoot.

My money is pretty tight right now.  I'll probably swap out the LSR 2-1 pipe for the Burns and retune the TW62G and see what difference the pipe swap makes.  Then hopefully by August I'll have enough to do the pistons and TW68G cam.  I'll keep the 58/62 tb on and see what kind of numbers I get and make a decision about going to a larger tb.