Fuel Mix Ratio = rich/lean

Got a technical question? Ask it in here.

Moderator: Moderators

User avatar
BJ
Expert participant
Expert participant
Posts: 271
Joined: Tue Oct 21, 2003 8:00 am
Location: Moving Quickly

Fuel Mix Ratio = rich/lean

Postby BJ » Fri Mar 18, 2005 2:01 pm

Here's one for you Howard.

I heard this the other day and to me it makes sense.

The higher ratio fuel mix you run the richer the fuel air mix through the carbi and vise versa.

The concept was based on the density of the mixture going through a pre defined jet size. The more lubricant in the fuel mix, the thicker the fuel and a very slight reduction in amount that goes through the jet. ie. leaner mix

While this might not make a huge difference in noticable performance, the way it was explained sounded reasonable to me. The person suggested that an engine would run leaner on a 100:1 mix than it would on a 50:1 mix.

I don't know that I would use this as a tuning method but I would suggest if you find an oil brand and mix that works it might be worth sticking with it. It could be more related to what your motor wants to run on than you think.

Or for the fanatical tuning freak the higher the altitude the more lubricant in the mix to compensate for less oxygen???????

A teaspoon full of oil at the beach, a litre in the Alps???

Has that got ya scratchin ya head Howard or just more BS????

Or do we just listen to Scorps and all ride SY125 four bangers????


BJ
Gone over to the Dark Side for a bit!!!!
http://www.parlagully.com

User avatar
Sherco H
B grade participant
B grade participant
Posts: 62
Joined: Wed Aug 18, 2004 8:27 am

Postby Sherco H » Wed Mar 23, 2005 11:55 am

BJ,
You`ve touched on motorcyclings Holy Grail. Everybody has their own belief. What`s the best oil, ratio, type of fuel, and I`m not even going near that one!!!!, as it opens up discussion boards that have raged the world over. Well before you came onto the scene. Can tell you though, I know of a bike that has run at 600:1 before it siezed. And ran at 200, 300 and 400:1 over six months. This was done to satisfy the owners curiosity as to what was the limit. No, it wasn`t me !!!!!! but it`s got me wondering.????
Cheers,
ShercoH. 8)



User avatar
BJ
Expert participant
Expert participant
Posts: 271
Joined: Tue Oct 21, 2003 8:00 am
Location: Moving Quickly

Postby BJ » Wed Mar 30, 2005 3:15 pm

Howard

Don't know if increasing oil ratio really makes an engine leaner but......Day 2 at Glenmaggie bright spark here is wondering why the bike was running off song and not idling right. :?: :?:

No.... not the aircleaner.... not dirty jets.......... Just had to look at the color of the fuel from the second tin I used that day. :idea: :idea:

Quess who put in two lots of oil!!!!! :oops: :oops: :oops: Anyway they were long fast laps that kept it cleaned out and I'm sure a bit more lube for the high speed never hurt! Just goes to show 25:1 Motul is not the preferred mix :!:


BJ
Gone over to the Dark Side for a bit!!!!
http://www.parlagully.com

User avatar
Sherco H
B grade participant
B grade participant
Posts: 62
Joined: Wed Aug 18, 2004 8:27 am

Postby Sherco H » Wed Mar 30, 2005 3:24 pm

BJ,
So that`s not campfire smoke in Keiths photos.
ShercoH. 8)



User avatar
BJ
Expert participant
Expert participant
Posts: 271
Joined: Tue Oct 21, 2003 8:00 am
Location: Moving Quickly

Postby BJ » Wed Mar 30, 2005 3:47 pm

Howard

Got me thinking now :idea: :idea:

Maybe that's why I scored so low on day two!!!!!!

Poor Observers couldn't see me paddling through the sections for the smoke...... and I just thought they were looking the other way????? Looks like its back to the lawnmower mix from now on!!!! Won't matter how the bike runs, if the wind is right I could push it through and still get a clean... Now I know how PA does it!!!!! 8) 8)


BJ
Gone over to the Dark Side for a bit!!!!
http://www.parlagully.com

nissh
Junior participant
Junior participant
Posts: 1
Joined: Wed Sep 14, 2005 6:52 am

mixture.

Postby nissh » Wed Sep 14, 2005 7:13 am

A given volume is full, in this example your crank case, this is made up of three parts: petrol, oil and air. If you add more oil it has to displace another because the volume is already full, as the petrol and oil are mixed externally and the jets meter the amount of fuel(petroland oil) entering the crank you have already sealed your fate. Petrol cools the engine, oil lubricates oxygen burns.
More oil = less petrol the air remains a constant.
Your engine will run lean, hot and you might here a top end knock (lean knock) not good.
You will go through plugs, damage pistons crowns and at worst nip it up.

Digest at your leasure zzzzzzzzzzzzzzzzz

Regards

Wee Scots chap with melted piston and welly,s.



User avatar
Robbymac
Junior participant
Junior participant
Posts: 3
Joined: Tue Jan 20, 2004 8:13 pm
Location: 'Two Tops' Cowra

Postby Robbymac » Fri Sep 16, 2005 2:29 am

I am surprised at how lean on the oil we can run these trials bikes.
I used to ride a rz250 on the street in sydney many years ago. When castrol tts was the best you could get. Over the course of nine months I just kept backing off the injection pump. eventually I got to about 200-1 petrol to oil riding around town, the pipe was grey at the back and the performance crisp. then I went for a run down to the snowy's and the crank nipped up at cooma...... my point being you need more oil if you are doing quick laps. Don't you think the difference in jetting caused a different mix of oil would be less than the difference in jetting caused by altitude. look at the problems the raod racers used to have at Bathurst.


call that a rock. I'll show you a rock.


Return to “Technical help”

Who is online

Users browsing this forum: No registered users and 3 guests