nuspeed88

I’m looking for some answer what is there differences?

w8ye

My Feedback: (16)

AAC = Aluminum Aluminum Chrome

ABC = Aluminum Brass Chrome

These are references to the construction of the piston/cylinder wall.

Enjoy,

Jim

tIANci

I believe it ABC means Aluminium Piston, Brass Sleeve, Chrome Plating on Sleeve. AAC means Aluminium Piston, Aluminium Sleeve, Chrome Plating on Sleeve. Is that correct? You get AAC most in RC car engines, the better engines are AAC.

ZAGNUT

My Feedback: (1)

that's news to me! most i've seen are ABC

very few real AAC engines out there. a good example is the enya X engines (except the .50) that never, ever wear out



dave

pnmrr

AAC I think it is Aluminum cylinder, Aluminum piston Chrome plated piston. A least I think that is how the K & B sportsters are made

djlyon

The Nelson 40 aac is about an oz lighter than the Nelson 40 ABC. It is currently the prefered configuration for Pylon racing.

Denis

wildthing7037

Copied and pasted from the Nelson Website....

Stefan

djlyon

Never met a pylon racer who was into user friendly

Rudeboy

You can both fry 'em... ABC or AAC, they both burn when you run 'em lean. But according to Dub Jett a fried AAC is cheaper to rebuild. With ABC, if you fry it, you have to replace both the liner and the piston... because the liner actually gets out of shape at the top end. AAC does not have this tendency. You just fry the piston, but the liner keeps its shape...

Apart from that, AAC is indeed significantly lighter. That's what I like about Saito's: the integral AAC cilinder design is top notch.

daven

My Feedback: (1)

I don't believe they are even making ABC versions any longer. You can break an AAC Nelson in significantly faster and easier than the ABC version. There was initially concern that the AAC version wouldn't hold up as long as the ABC version, but I haven't seen that at all. With the weight savings, ease of break in, and longevity, the AAC version is what most people are using.

All this being said, I believe the current National record was set with an older ABC motor

sport10

I thought that in AAC engines the chrome is applied to the aluminum bore in the cylinder head. There was no removable aluminum sleeve.

Rudeboy

Depends on the engine. Saito has an intergral cilinder design: no sleeve. But Jett and Nelson engines still have a liner... it's just made out of alu instead of brass...

downunder

I believe the K&B's mentioned earlier had the chrome put directly on the inside bore of the crankcase but the Enya 60X had a normal removeable aluminium liner that was chromed. The Enya 80X was ringed with a steel sleeve though.

djlyon

I don't think the K&B sportsters were chromed at all, either piston or cylinder. I'll confirm this tomorrow because the 20s are still being made by Randy (MECOA). We're using them in AT6 pylon racing

Denis

ZAGNUT

My Feedback: (1)

i do remember a reviewer of the .45 sportster saying that the piston was plated but can't remember if it was nickel or chrome. and yes, no separate sleeve just a detachable cylinder with integral fins



dave

daven

My Feedback: (1)

The Nelson AAC definately has a sleeve (I had one apart last night) and have looked inside many of them.

djlyon

K&B Sporsters. Pistons are chrome plated aluminum running in an aluminum bore. At least the new 20 sportsters are. So I'm sure they all were.

Denis

gcb

I'll have to disagree with that. I'm looking right now at my older K&B .20 Sportster (with the needle on the carb) and it has a shiney cylinder (chrome?) and a dull piston (aluminum?).

I'll take your word about the new ones, but I can't see why they are opposite most other manufacturers on their combo. Perhaps they anodize the aluminum cylinder or use a high silicon content alloy.

I'm glad that K&B/MECOA is still making them. How well does the remote needle work?

George

PS. Sorry for hijacking the Nelson thread.

djlyon

George

I'm not actually personally familiar with the sportster engines. I've never taken one apart. There is about 9 guys in our club that are currently very active in pylon racing, a mix of 424, 428, Q40 and AT6. About 5 of them are flying AT6 for fun and entertainment, to relax a little from 428 and Q40. I don't race AT6. The local rules for AT6 only allow OS 25 LAs or K&B 20 sportsters. Don't ask me to explain the logic of that. The K&B is the prefered engine obviously if you can get one. A couple of guys in our club have managed to get new ones from MECOA and they may be available over MECOAs web site. They checked them and told me chromed piston. It seemed unusual to me too. Sence reading your post I emailed a club member who builds engines for MECOA and asked him when and why the change was made from chroming the sleeve to chroming the piston. I'll let you know if and when I get an answer. If he doesn't answer the email it'll be a couple of weeks before I see him at the field because this week end will be taken up with pylon racing at the basin.
The remote needle seems to work fine. At least the guys seem to be happy with it.

Denis

gcb

Denis,

Does your friend work for MECOA or K&B? When Randy Linsolato bought K&B he kept K&B's production intact. That was several years ago and may no longer be true.

Since seeing your post I looked up the K&B's on the MECOA site. It was very interesting. My old K&B Sportster came with instructions and a three view but no parts list nor exploded view. Since it may have the "O" ring (early models) I will not pop the head unless necessary...might have to replace the "O" ring.

I was wondering how you fix it when it's worn out. Apparently you replace the jug and piston since it has no liner. Learned something new...great!

George

Edit: typo

djlyon

Hi George

My friend is a machinist who occasionaly works for Randy when ever needed. The last time I was down there was over a year ago. It looked to me that when Randy bought K&B he moved the whole operation in with the rest of his operations. I believe he kept K&B as a separate company for accounting purposes only. I still haven't heard from my friend. He just recently moved and may not be minding his email.

Denis