PilotOdyssey.com
http://www.pilotodyssey.com/PO/

Comression for pump gas and best way to get it
http://www.pilotodyssey.com/PO/viewtopic.php?f=1&t=17795		 Page 2 of 2
Author:  dipnadactyl [ Wed Dec 20, 2017 6:15 pm ]
Post subject:  Re: Comression for pump gas and best way to get it
Randman wrote:
Not everyone can afford to run race gas. At 10 bucks a gallon I for one can't.

This Engine can be simply de-tuned to run on regular pump gas with no issues. Ridindirty's Ody Engine was a race Engine and it runs very strong de-tuned on 91 octane with 10% ethanol pump gas. You just need to know what modifications were made to the top end to correct them.

Proper jetting is everything for 2 stroke Engine longevity. Remember spark plugs are cheap! Top ends aren't.

Rand


Rand: Yes - also good points. I certainly cannot afford $10 a gallon either but av fuel is only about 4.75 per gallon and (in my case, at least) for the small premium in cost over 93, is good insurance against another melt down. I've had too many. I've heard others are getting good results from mixing 50/50 with 93 but I'm still gun shy and don't want to push my luck.
Author:  Randman [ Wed Dec 20, 2017 10:57 pm ]
Post subject:  Re: Comression for pump gas and best way to get it
I've never used av gas. Never had to but then again I've been playing with 2 strokes since the 70's and was taught jetting by an old 2 stroke racer.

Amazingly enough, I've only burnt one top end. I let my brother mix the oil and gas. Come to find out, he forgot the oil. Poured in straight fuel on top of about 2 gallons of gas. She ran like a raped ape until the top end went! Lesson learned. Do it yourself, this way you have no one to blame but yourself if shit goes south!

I jet to just short of fouling plugs which brings the power level down slightly but improves top end life. I have bought so many spark plugs I should have bought stock in NGK!

I even have a sand blaster for cleaning spark plugs which saves me money.

Rand
Author:  Superlite_Don [ Wed Jan 17, 2018 1:03 pm ]
Post subject:  Re: Comression for pump gas and best way to get it
So an update. He had the cylinder bored. I think 80.5mm. Then put it back together with shims under the barrel and did some compression testing. He has now ordered a copper base gasket .080" and thinks this will hit around 160 PSI so it will run on 93 octane. So we will know the end of the story when he gets it put together. He sent me some cool pictures of the porting that I thought you would like to see. Um, we had a bunch of ports in this thing... I think you will see why we turned it so many RPMs...Boost ports, wings, etc. Back in the day this was all top secret. I almost feel dirty posting them, lol. It did not have the low end the Nature's Recipe cars did (Bills Pipes motors), but it flew on high speed tracks. Won the SCORE Off Road World Championships, MTEG Rose Bowl, and MTEG Indianapolis Hoosierdome races with this (or its clone).

Attachments:
IMG_1628.JPG
IMG_1628.JPG [ 53.93 KiB | Viewed 286 times ]
IMG_1629.JPG
IMG_1629.JPG [ 59.2 KiB | Viewed 286 times ]
IMG_1630.JPG
IMG_1630.JPG [ 50.88 KiB | Viewed 286 times ]
IMG_1631.JPG
IMG_1631.JPG [ 63.03 KiB | Viewed 286 times ]
IMG_1632.JPG
IMG_1632.JPG [ 64.9 KiB | Viewed 286 times ]
Author:  canadian oddy [ Wed Jan 17, 2018 3:50 pm ]
Post subject:  Re: Comression for pump gas and best way to get it
Superlite_Don wrote:
So an update. He had the cylinder bored. I think 80.5mm. Then put it back together with shims under the barrel and did some compression testing. He has now ordered a copper base gasket .080" and thinks this will hit around 160 PSI so it will run on 93 octane. So we will know the end of the story when he gets it put together. He sent me some cool pictures of the porting that I thought you would like to see. Um, we had a bunch of ports in this thing... I think you will see why we turned it so many RPMs...Boost ports, wings, etc. Back in the day this was all top secret. I almost feel dirty posting them, lol. It did not have the low end the Nature's Recipe cars did (Bills Pipes motors), but it flew on high speed tracks. Won the SCORE Off Road World Championships, MTEG Rose Bowl, and MTEG Indianapolis Hoosierdome races with this (or its clone).


Thx for posting those pics. If we were all racing for the same championship here then I would say keep it secret, but many of us will never even meet each other in our life time. We don't even race anymore (a lot of us anyway). Plus very few even know what an oddy is, as they have never seen one. Our world is a small one now. Great to see some old history.
If ya would have cut anymore holes in that cylinder you could have used fly screen.

I got no confidence in that 93 octane decision. Amen.

Edit: Take a look at Randman and dipnadactyl comments above and you can see how critical it is.
dipnadactyl blew several engines in a row just like I did running straight pump fuel. Randman gets away with it by running so rich he fouls plugs and wants to buy shares in the plug company. Now you burn fuel like an F15 on afterburner. Also the Engine has to be in perfect condition. Get it wrong and it's all over. Pump fuel detonates, that's a reality. The fuel companies get away with it because all modern engines have deto control in the Engine management system. These old oddys don't.
Author:  Randman [ Wed Jan 17, 2018 5:18 pm ]
Post subject:  Re: Comression for pump gas and best way to get it
Randman gets away with it by running so rich he fouls plugs and wants to buy shares in the plug company.

Actually I don't foul spark plugs, because my Ody is jetted correctly. When my plugs show signs of carbon and oil buildup, I clean my plugs with an abrasive blaster. Once they show signs of abrasive wear from abrasive blasting I buy new ones..... they're cheap.

Like I said, I've only burnt a hole in one piston since 1977.

Rand
Author:  adnoh [ Wed Jan 17, 2018 9:00 pm ]
Post subject:  Re: Comression for pump gas and best way to get it
I have a couple of thing for him to check if not to late. Since he is using a base gasket .080 or 2 mm if read correctly he may want to check the shirt on exhaust side at TDC (Top Dead Center) also ring land pins ( ring end gap)on intake at BDC do not want a short cycle or pin in the intake port. The squish will of course greater most likly near 2.5 to 3 mm. I base this off of some assumptions, base .060 thicker with the base line head at .040. just guessing. If set to run at 10500 raising ports .060 will effect that which is a given. Just some thought to change. Most likely already had a fatty so not to big of deal just may need to add stall to clutch to get it there. Hope it works well for him. Thanks for pics way cool.
Page 2 of 2 All times are UTC - 5 hours [ DST ]
Powered by phpBB® Forum Software © phpBB Group
https://www.phpbb.com/