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Engine basics => Engine set up tips => Topic started by: Tim Wescott on November 30, 2018, 06:11:53 PM
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What is Perry Directional Porting? What's it's history, and what does it do? Anyone got explanatory pictures? Is it related to Perry carbs?
I remember it being touted on engines that I couldn't hope to afford back in the late '70's, but that's all I know about it.
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What is Perry Directional Porting? What's it's history, and what does it do? Anyone got explanatory pictures? Is it related to Perry carbs?
I remember it being touted on engines that I couldn't hope to afford back in the late '70's, but that's all I know about it.
PDP porting was sort of a ripoff of Dr Schnuerle's porting arrangement, it added 4 very small ports, 2 in the front and 2 in the back, in the same place a standard loop charged port would go, Boosting the performance of the single bypass arrangement
Randy
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Its not quite the same as a perry caburator .
(http://www.sceptreflight.net/Model%20Engine%20Tests/ST%20G60%20FI%20ABC-PDP%20page%201.jpg)
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Confusers awry , Read the second page here , save me rattling on . http://www.sceptreflight.net/Model%20Engine%20Tests/ST%20G60%20FI%20ABC-PDP.html
They aim to blow the incoming charge aft , so it doesnt disapear out the zorst ol;e .
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I've allways thought that main idea of them ports is to clean away the used gases that would otherwise stay stuck in the turbulence behind piston baffle.
At least my plan is to do something like that in my next piston/cylinder group. L
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I've allways thought that main idea of them ports is to clean away the used gases that would otherwise stay stuck in the turbulence behind piston baffle.
There is no piston baffle on a Perry ported engine (flat top). Think of it as three water hoses aiming at each other and meeting in the middle. Most engines have the side ports open first, to block the path of the rear port fuel charge opposite the exhaust and send it up to the combustion chamber, not out the exhaust.
Al.
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Its not quite the same as a perry caburator .
I understand it's not the same thing. I was wondering if it came from the same guy.
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There is no piston baffle on a Perry ported engine (flat top). Think of it as three water hoses aiming at each other and meeting in the middle. Most engines have the side ports open first, to block the path of the rear port fuel charge opposite the exhaust and send it up to the combustion chamber, not out the exhaust.
Al.
PDP were born to improve the scavengig conditions.
The various engine manufacturers have used them with baffle pistons, Supertigre porting (flat top) , with the only purpose of improving engine operating conditions.
Massimo
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How many Perrys are there out there , Id assume it'd have to be the same outfit. But thats only a guess .
On the Como 51 or was it the ST 60 3 window , the front of the two slots about on the baffle , the rear 1/2 open behind the baffle . thereabouts .
' They ' are two vertical slots approximate same timing as intake . Ea Side , NOT tangental - Angled substantially toward the bypass .
The ' Vane ' between the two slots thus also anglked same .
Yea , Clear unscavenged gas , but also the action rearwards reducing the typical 2 stroke waste comparable to over high valve timing overlap on a 4 stroke .
Which is why enhanced pipes have a strong effect . The PDP not neccesarilly being tooned pipe relevant . More a combustion cycle enhancement .
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The Perry in question developed and made carbs for K&B/Veco and at roughly the same time, developed the PDP deal. They had a name like "Perry Automotive" or something like that. Seems to me like K&B may have been first to use PDP, but Super Tigre and HB (not HP) for sure used it. Possibly also Irvine or Webra as well, but I'm not that familiar with either brand. I have two HB .61's, one PDP and one not. Irvine started out as a K&B derivative, and I seem to recall that HB may have been also. "HB" was short for "Helmut Bernhardt" or somewhere close to that.
I had a Big Jim Greenaway PDP ST .60, and I wondered if Jim might have plugged the PDP ports with JB Weld or something, but never looked. I would expect he at least tried it. D>K Steve
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PDP porting was sort of a ripoff of Dr Schnuerle's porting arrangement, it added 4 very small ports, 2 in the front and 2 in the back, in the same place a standard loop charged port would go, Boosting the performance of the single bypass arrangement
Randy
I agree. When Schnuerle-porting hit the market and blew away to old single bypass engines, some manufacturers tried to compete without making entire new engines. PDP was a low budget attempt to stay in the game with the tooling, slightly modified.