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November 15th, 2007, 06:48 AM
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Join Date: Sep 2006
Location: San Leandro, CA (near San Francisco)
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Independent slide throttle bodies
I've come up with another crazy question, and I'm hoping I can get some confirmation or deny...-ation(there is no noun form of "to deny") on whether it's a good idea or not.
I found this resource on the BMW m3, and for a time, they came with slide throttle bodies rather than butterfly throttle bodies. For a time, BMW made slide throttle bodies to get better performance out of their engines. They made driveability tough because they're inconsistent. It isn't a linear or even exponential gain in airflow with a linear increase on throttle. Basically, they're good for WOT and nothing else.
Knowing that, I was ready to close that book of thought and move on. However, there are gains to be made in throttle response if the intake runners are shorter, and the air distribution is more even with independent throttle bodies. At WOT slide throttle bodies are more efficient because there's no sideways-butterfly-valve hampering flow and creating turbulence.
To solve the non-progressive problem, why not change the shape of the intake? What I mean is, instead of making round O shaped openings, make them triangular or even square. If they're triangular, like < and the slide moves from right to left, creating a forced progression on air intake levels, wouldn't that solve part of the driveability problem, while giving the same huge gains at WOT? You'd also get much better throttle response from the shortened (possibly 6" or less) intake runners, and lack of a plenum. It would also be really cheap to manufacture, and would require next-to-no maintenance.
Mounting up electronics and vac lines would be identical to the Suzuki ITB setup a lot of people are running now, and mounting injectors would just require some messy holes drilled with oversized rubber gaskets bored out to fit the injectors for a tight fit.
Correct me if I'm wrong, but this sounds like a fun weekend project. Let me know what you guys think. |
November 15th, 2007, 12:24 PM
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Super Moderator
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Location: Gs-R-less in New York.
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wouldnt making the openings square or triangular decrease air flow kinda making them useless?? If i understand correctly the reason they are round is to maximize flow with little resistanse and increase turbulance in the air flow since it will intake in a tornado style air flow giving you better mixture in air and fuel. correct me if im wrong. Blake would deff know about this he has a home made itb project going on.
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November 16th, 2007, 05:24 PM
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Noob
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Join Date: Oct 2007
Location: La Ciotat, France
Posts: 26
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Interesting reflexion...
To my mind -tho I'm not specialized in fluid dynamics- as A_White_Gs-R stated it, the round shape is to maximize air flow speed through a kind of swirl effect. Edges brings turbulences, turbulences slow the air column...
PS: Is not the noun form for deny...denial?
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November 16th, 2007, 09:45 PM
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CRXus Maximus Arelues
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Join Date: Mar 2006
Location: North West NJ
Posts: 2,073
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Funny this is being thought of on cars. For years to get more performance and throttle response out of our RC car engines we switch to slide carbs rather then the more restrictive butterfly style.
When I switched my T-Maxx to a slide carb the tunability greatly improved as did the top end.
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November 16th, 2007, 10:39 PM
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The shape of the intake tract usually follows the port shape usually. The shape really wouldn't matter much i'd think with respect to flow, but changing shapes wouldn't be a good idea.. especially that close to the port. I didn't do that well in fluids though so I don't know that much about laminar flow or that shit haha.
Making a non linear throttle would actually not be that hard if that's the battle to making the tuning easy. I really don't know what the problem is with slide throttles, just heard that they're a pain to tune at part throttle (have heard the same about ITB's though so who knows).
I actually have a couple designs drawn up that would work better than traditional butterfly throttle bodies but meh, it'll probably never get done.
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November 17th, 2007, 12:41 PM
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Quote:
Originally Posted by njn63
The shape of the intake tract usually follows the port shape usually. The shape really wouldn't matter much i'd think with respect to flow, but changing shapes wouldn't be a good idea.. especially that close to the port. I didn't do that well in fluids though so I don't know that much about laminar flow or that shit haha.
Making a non linear throttle would actually not be that hard if that's the battle to making the tuning easy. I really don't know what the problem is with slide throttles, just heard that they're a pain to tune at part throttle (have heard the same about ITB's though so who knows).
I actually have a couple designs drawn up that would work better than traditional butterfly throttle bodies but meh, it'll probably never get done.
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I think I'm going to greenlight this on my project list. First step is to get a camera, though. I've got to get pics, if I do it. I imagine it'll sound pretty interesting with pod filters too.
Is there a reason for long runners on the intake side that anybody knows of? |
November 17th, 2007, 03:42 PM
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Made Member
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Quote:
Originally Posted by njn63
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Just ordered a copy. $10.76 |
November 17th, 2007, 03:58 PM
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Fresh Meat
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Join Date: Nov 2007
Location: Naperville/Chicago, Ill
Posts: 14
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Quote:
Originally Posted by njn63
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Thats exactly right, Check out AEMPOWER.COM and look at the "How the V2 works" demonstration, it does a pretty good job conceptualizing the air pressure/velocity thing. Wavelengths change as RPMs change. Long runners typically produce better high-rpm performance, whereas shorter runners produce better torque and throttle response. (Almost sure i'm right on all that.) |
November 18th, 2007, 01:41 AM
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Quote:
Originally Posted by Ice78Transam
Thats exactly right, Check out AEMPOWER.COM and look at the "How the V2 works" demonstration, it does a pretty good job conceptualizing the air pressure/velocity thing. Wavelengths change as RPMs change. Long runners typically produce better high-rpm performance, whereas shorter runners produce better torque and throttle response. (Almost sure i'm right on all that.)
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Other way around, shorter for high rpm.. at least I think so.
There are many engines with variable length runners also that we havn't talked about which is a good idea. I think the e46 BMW's had them and of course the 787B le mans cars did. |
November 18th, 2007, 02:03 PM
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Quote:
Originally Posted by njn63
Other way around, shorter for high rpm.. at least I think so.
There are many engines with variable length runners also that we havn't talked about which is a good idea. I think the e46 BMW's had them and of course the 787B le mans cars did.
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Let's just skip right on past the part where you go more in-depth about that. I'm not competing with any le mans cars here. I'll actually be happy as long as my power doesn't go DOWN. So, 6" runners? Velocity stacks, basically? |
November 18th, 2007, 05:01 PM
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velocity stacks help get the most air in and creat the swirl effect which causes turbulance which you do want inorder to get a maximum air fuel mixture. Short for high rpm power band and long for low rpm power band. You might get away with a 3"runner with the velocity stack since that will ad maybe another inch or two to the total runner length.
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November 19th, 2007, 04:00 PM
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Quote:
Originally Posted by A_White_Gs-R
velocity stacks help get the most air in and creat the swirl effect which causes turbulance which you do want inorder to get a maximum air fuel mixture.
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I disagree with that. Velocity stacks do help get the most air in but it's because they allow the smoothest entry possible into the pipe with the least turbulence.
I have no idea what to suggest for runner length, i'd just make sure to make it adjustable because it's very hard to calculate the best runner length with so many variables. |
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