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Inlet trumpet dyno testing

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Impressive stuff. You even got props from Billzilla! Haven't seen that name in years.

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@Roman  Dave getting all the credit, with his following of fellow graph theorists

dave.jpg.76ffa2bf7ce203422a67f2b945aab32e.jpg

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This thread is still warm so I don't mind bringing it back from the dead.

Just a theory question, does the throttle plate position make any difference to the function of an inlet runner? Say you have two identical intakes of 10" length, from inlet port to bellmouth. One has the throttle butterfly right up against the head, and one has it right up against the bellmouth. So one has a 9" stack, and one has a .5" stack, but the total lengths are the same. Would there be a theoretical difference? 

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Wouldn't think so,  not at wide open throttle anyway.

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15 hours ago, gibbon said:

This thread is still warm so I don't mind bringing it back from the dead.

Just a theory question, does the throttle plate position make any difference to the function of an inlet runner? Say you have two identical intakes of 10" length, from inlet port to bellmouth. One has the throttle butterfly right up against the head, and one has it right up against the bellmouth. So one has a 9" stack, and one has a .5" stack, but the total lengths are the same. Would there be a theoretical difference? 

Yeah, the throttle plate creates a lot of turbulence downstream, even open. I can't recall specifics but I know Duckworth has talked about this, I believe he said it takes a decent amount of length of straight port before the flow cleans up again. So you are better off running them as far away from the port as possible, as the dirty flow can cause early flow separation off the short turn in the port.  Of course, the further out the throttle plate from the valve the larger it needs to be. In terms of harmonic turning I don't think there would be a big difference at WOT, though you may get some different effects at lower throttle openings if there are reflections off the throttle. 

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Going to do a round 2 on this soon, since i've forgotten how long it took last time.  
 Same deal as last time, you can send me stuff and will test it.    Pretty much anything goes this time.    Main thing i will be testing is smaller diameter trumpets,  which i will likely make from pvc  or anything else i can find in the correct diameter.   If have any dumb ideas novelty items etc..  or think you can build something that beats everything in the last test, send it my way.     My normal  intake will be the baseline everything is tested against.

 

Will probably do the same thing  on a stock blacktop 20v fwd format, at some stage also.  which maybe of more benefit  to most people, that haven't spent half their life polishing a turd. (not saying a 20v isn't a turd, it definitely is )

 

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Have done some butchery with some more power duct.     This is same as one of the ones in last test (51m id).   but ive cut a section out of some more pvc and slid it inside.  making 46mm runner,  will slide a second one inside  make 41mm.       just need to acquire  some more to cut up

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I would love to see the difference in performance of moving injectors outboard of trumpets, but a bit of work to setup for someone.

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1 hour ago, Hyperblade said:

I would love to see the difference in performance of moving injectors outboard of trumpets, but a bit of work to setup for someone.

This video does a good job of showing those effects on a Honda B engine: 

 

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2 hours ago, Hyperblade said:

I would love to see the difference in performance of moving injectors outboard of trumpets, but a bit of work to setup for someone.

Only thing that sucks is the wall wetting area gets massive. So steady state is fine but transients become super messy. 
Your tune can work really well at a given rpm accel rate (like 4th or 5th gear) but then is messy in 1st and 2nd because the delayed evaporation now happens at a different rpm.
You really need to maintain a hot intake manifold temp to keep evaporating the fuel that sticks to the runners. 
With a temperature insulated intake manifold it ends up feeling like you're cold start tuning your car the whole time it runs.

Also need a big injector so that you've got some scope to move the injector timing around to avoid standoff issues.
Where the fuel blows back out the top of the runner.

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1 hour ago, Truenotch said:

This video does a good job of showing those effects on a Honda B engine: 

 

Thanks for that, great video, clearly a no brainier if you can do it.

1 hour ago, Roman said:

Only thing that sucks is the wall wetting area gets massive. So steady state is fine but transients become super messy. 
Your tune can work really well at a given rpm accel rate (like 4th or 5th gear) but then is messy in 1st and 2nd because the delayed evaporation now happens at a different rpm.
You really need to maintain a hot intake manifold temp to keep evaporating the fuel that sticks to the runners. 
With a temperature insulated intake manifold it ends up feeling like you're cold start tuning your car the whole time it runs.

Also need a big injector so that you've got some scope to move the injector timing around to avoid standoff issues.
Where the fuel blows back out the top of the runner.

So, was thinking about running staged, with some 700cc injectors I have here outboard... 

Still need to see if I can fit them in the manifold.

But probably best not to derail this thread anymore :)

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Haven't bothered trying it for reasons @Roman  suggests.    If was dedicated race car would have likely tried it already.

Still would be interesting to see if has as much benefit  as what old mate had on the b16a

I can say if you are going to do it.  move them far as possible, going actual outboard.   moving my injectors back from head about 50mm to the throttles had zero or at least un-measurable effect.  Probably also want to go bigger than 700cc.  got 980cc's on mine (dont ask why)  and thats 40% duty on pump gas.   I'm  assuming you will be making more power, so to get in  window to avoid stand off, probably need something bigger 

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I'll throw my two pennies worth in here ... unless you have irrefutable engine dyno #'s, then everything is theory ! 

Many theories have been tested and been held to be true, what works on one installation may not on another  (  this holds true for fuel entry placement and throttle body design &c )

The radius on the trumpet bell mouth is a function of throat diameter ( there is a mathematical formula for this curve, but to be honest, it probably varies with air density &c, so flag it ! ) and should extend right to the backside of the horn ( as in the picture of the Honda  B16 ) 

Change of Trumpet or port diameter is limited to around 4 deg before turbulence 

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From my testing, a full bell mouth that rolls back around on itself is unneeded.  diminishing returns over anything more that a basic bellmouth that barley makes it to 90deg.   I thought this maybe as you say  something to do with my setup.   the runners being oversized for the engine meaning the bellmouth has less effect.   But  some preliminary testing yesterday on a runner that is too small for the engine basically acted the same way.  a small flair on the end got it close to what a full bellmouth can do.     Still have more things to try before  come to any conclusions, and as you say my conclusion may not work on another engine.  Ive seen downsizing of the runner work on a similar engine to mine,  but it maybe band aiding another issue

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How loud were the cones in person? 

I’m pretty surprised about that peak down low. It’s  a considerable jump!

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Bit louder than normal,  which is all the loud.  sounds like a deeper dort.

Yeh it does some silly stuff around there when get too out the gate with length or small diameter so i found out..   80kw at 4000rpm is pretty lol though

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Results are in on the downsized runners.    

 

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Nice! The results are basically as expected. Looks like a big tapered inlet has some potential? Cool to see the power climbing and staying level right up to 9k. 

We really need to get a Beams on that dyno... I’m curious to see the difference between 45-55mm on a 2L engine. 

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