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Old Mar 12, 2009, 08:27 AM
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basic engine definitions

Can someone guide me to a post or reference that lists definitions of basic engine terms I see in ads, like "ABC", "BB", or "Schnurle"?

Thanks,

Del
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Old Mar 12, 2009, 11:07 AM
'Merica!
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Here you go.......
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Old Mar 12, 2009, 01:27 PM
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Thank you.

Del
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Old Mar 12, 2009, 10:22 PM
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I'll try to be brief.

The ABC you mentioned is the type of construction of the piston/liner where "A" means an aluminium piston, "B" means a brass liner which is "C" for chrome plated.
Then there's ABN where the "N" means the brass liner is nickle plated.
AAC is aluminium piston, aluminium liner chrome plated.

These are the most common types you'll run across but sometimes you'll see something like ABCR or AACR where the "R" means the piston has a ring (mostly in some 4 stroke engines).

Another term you might come across for the piston/liner is ceramic or AAO (same thing) which is an aluminium piston and aluminium liner that's coated with Aluminium Oxide. So in fact it should be called an AAAO . This is what the Norvel engines use and is superior to anything else. The problem is that, for now, only the Russians have perfected the process. Fox are now selling a couple of ceramic engines but I'd assume their liners may came from Russia.

The only other terms you might hear are ringed (aluminium piston with a ring running in a steel liner) and lapped (cast iron piston running in a steel liner).

OK, that's the complicated bit done.

"BB" stands for Ball Bearing which just means the crankshaft runs on ball races at the front and back. "PB" would mean Plain Bearing where the crankshaft runs in a brass bush. Both have their good and bad points.

Schneurle means the type of ports used in the liner to get the mixture up from the crankcase into the cylinder. This is almost universal today but very old engines had a different porting system and needed a baffle on top of the piston to direct the mixture up into the cylinder. With Schneurle porting the top of the piston is flat.

And it seems I wasn't very brief after all .
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Old Mar 13, 2009, 06:39 AM
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Thank you, also.

Del
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Old Mar 13, 2009, 09:57 PM
TigreJohn
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Missed one: PDP = Perry Directional Porting. This was a multi-port intake system that pre-dates the Schurnle. Or was the Schurnle a refinement of the PDP? Was used in Super Tigres and K&B's in the late 70's-early 80's. Also used a flat top piston.
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Old Mar 14, 2009, 05:53 AM
Will fly for food
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PDP was a way of introducing Schnuerle without major changes to engine design.

Other 2 storkes engines (motorcycles, snowmobiles, outboard motors, etc) had Schnuerle porting a LONG time before PDP.

Quick Google, Schnuerle porting was invented in the 1920s.
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Old Mar 14, 2009, 06:35 AM
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Don't forget TST. (Travassi Super Tigre) which was Supertigre's implementation of enhanced porting back in the day.
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Old Mar 14, 2009, 06:59 AM
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In 50-odd years of playing with model engines no-one has ever asked me a solitary question about "PDP" or "TST".

So I'm not sure I'd really regard either of those being included in "basic engine definitions" .

Steve
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Old Mar 14, 2009, 10:00 AM
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Quote:
Originally Posted by slipstick
In 50-odd years of playing with model engines no-one has ever asked me a solitary question about "PDP" or "TST".

So I'm not sure I'd really regard either of those being included in "basic engine definitions" .

Steve

Look at old seventies and eighties World Engines ads and you'll see TST mentioned quite frequently. PDP has been around since the early seventies and is usually associated with K&B/Irvine/HB engines and later spreading to Super Tigre engines.

Most folks needing a glossary aren't focused on expensive high performance sport engines, so it isn't a surprise that you didn't receive many queries regarding this nomenclature.


Ed Cregger
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Old Mar 14, 2009, 10:58 PM
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Engine design and construction has been almost standardised ever since the old OS FSR's came out so some of the older technology isn't necessary to know. Probably the one modern engine that's different are some of the Enyas which use cast iron pistons which can trap the unwary.
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Old Mar 15, 2009, 07:17 AM
Will fly for food
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Why are we limited to "modern" engines.

I didn't know about TST, the STs I have, that have any such porting, are PDP.
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Old Mar 15, 2009, 09:25 AM
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Quote:
Originally Posted by Pinecone
Why are we limited to "modern" engines.
Well of course you're not limited to modern engines, thread drift being what it is. But I suspect the OP was asking about the basic engine terms he sees in current adverts, not ads in 50-60 year old magazines. He may by now be somewhat confused .

Steve
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Old Mar 15, 2009, 12:24 PM
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Everett Wa.
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How can more information, if correct, be confusing?

With the advent of E-bay and the internet these older engines are still being traded. When I sell some of my engines that are not to modern standards over the internet. I ask the buyer if he really knows what he bought. If he doesn't I offer him the option of opting out of the sale.

Just for clarity. The original Schnuerle patent had only 2 intake ports on the sleeve, no boost port. The Fox 36RX is one such engine with true schnuerle porting.

PDP was an atempt to scavange the "dead zone" on the exhaust side of the baffle. PDP got its power boost by allowing a cleaner intake charge to be burned in the combustion chamber than the standard baffle system allowed. It had nothing to do with Schnuerle porting.

The real benifit to schnuerle porting was (is) the elimination of the baffle. This allowed the flame front to travel across the top of the piston unimpeeded.

Definition:
"Auto mixture carb" is a carburetor that changes the fuel metering orifice as the choke area changes.

"Air bleed carb" is a carburetor that has no other way to control fuel flow than to bypasses air around the fuel spray bar to lessen the fuel draw at idle.

FYI;
The first P in PDP is the same Perry as the Perry carb. I think only Clarence Lee, ST. and HB bought the rights to use PDP in their engines. K&B never did buy the right. So any new K&B with PDP was a Lee Custom engine.

I don't like the paragraph under "timing" in the posted link. But then its not my web page.

All the best,
Konrad
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Last edited by Konrad; Mar 15, 2009 at 12:44 PM. Reason: Change Clearance to Clarence. Sorry Clarence
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Old Mar 15, 2009, 01:34 PM
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Konrad: FYI;
The first P in PDP is the same Perry as the Perry carb. I think only Clarence Lee, ST. and HB bought the rights to use PDP in their engines. K&B never did buy the right. So any new K&B with PDP was a Lee Custom engine.

-------------


I stand corrected. K&B had their own version of schneurle porting and did not use PDP.

And, again, you are correct in saying that all K&B engines with PDP are the result of Mr. Clarence Lee's efforts (the engine's designer).


Ed Cregger
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