180,000km 4kc Igniton Timing?

[Evan G]

gday all

 

ive got a ke55 4kc and ive done the timing as per workshop manual (6 degrees on idle)

 

its got me think, workshop manual says 6 degrees on idle with 90 octane. So if I'm running 95-98 octane how much should my idle be advanced? to get all the power out of it

 

 

ill be putting it on the dyno at tafe in a couple of weeks, should i just do it then?

 

thanks

Ev

[Felix]

Try bumping the timing up a few degrees at a time and see for yourself. If it pings, or runs hot, back it down a bit.

 

I wouldn't be expecting too much from a stock 4k.

[Evan G]

Try bumping the timing up a few degrees at a time and see for yourself. If it pings, or runs hot, back it down a bit.

 

I wouldn't be expecting too much from a stock 4k.

 

speaking of running hot, i had the 4 gas emission tester on my ke55 and we found it was running a bit lean, so we backed it to 14.7:1 (91 octane) and ive seen my temperture gauge creep upto 1/2 way. its normaly 1/4?

 

 

but now its down to 1/4ish with 98 octane?

[kiahn]

speaking of running hot, i had the 4 gas emission tester on my ke55 and we found it was running a bit lean, so we backed it to 14.7:1 (91 octane) and ive seen my temperture gauge creep upto 1/2 way. its normaly 1/4?

 

 

but now its down to 1/4ish with 98 octane?

 

higher octane fuel burns slower and cooler, maybe this is the reason for the temp creeping??

 

 

 

my gregory's manual said 8 degrees at 2000 rpm and i was running 10-12 degrees when i put 95 through it and it ran fine without pinging

Edited July 15, 2009 by kiahn

[Evan G]

higher octane fuel burns slower and cooler, maybe this is the reason for the temp creeping??

 

 

 

my gregory's manual said 8 degrees at 2000 rpm and i was running 10-12 degrees when i put 95 through it and it ran fine without pinging

 

wouldnt higher octane fuel burn faster? the more the octane the more BANG the camber will have therefor piston will be pushed down harder?

 

and also another bit i don't understand is a engine running lean will run hotter, but when i adjusted the mixtures to run perfect the temp went up? WTF :dance:

 

i think fuel burn time has something to do with it, so run 10 - 12 degrees with 95 octane?

 

 

For everyone who doesnt really understand a cars ignition keep reading

 

with the workshop manual it says 6 degrees advanced with a minium of 90 octane fuel. Lets Say : piston is 6degrees BTDC, air/fuel is ready to be ignted, so when the air/fuel is ignited the piston will be 2 degree before heading down, there for will be induced a knock.

 

(was getting BAD knocking with 91)

 

same scenario but timing slighty advaced - lets say the piston is 3 degrees BTDC, air/fuel is compressed and ready to get ignited, now when theres ignition piston is 1 degree before heading down. now that theres higher octane fuel in the engine it will be burn quicker therefore pushing the piston down just as fuel ignites,

 

hence more power and no knocking

 

evan.

Edited July 15, 2009 by Evan G

[kiahn]

wouldnt higher octane fuel burn faster? the more the octane the more BANG the camber will have therefor piston will be pushed down harder?

 

and also another bit i don't understand is a engine running lean will run hotter, but when i adjusted the mixtures to run perfect the temp went up? WTF :dance:

 

i think fuel burn time has something to do with it, so run 10 - 12 degrees with 95 octane?

 

 

For everyone who doesnt really understand a cars ignition keep reading

 

with the workshop manual it says 6 degrees advanced with a minium of 90 octane fuel. Lets Say : piston is 6degrees BTDC, air/fuel is ready to be ignted, so when the air/fuel is ignited the piston will be 2 degree before heading down, there for will be induced a knock.

 

(was getting BAD knocking with 91)

 

same scenario but timing slighty advaced - lets say the piston is 3 degrees BTDC, air/fuel is compressed and ready to get ignited, now when theres ignition piston is 1 degree before heading down. now that theres higher octane fuel in the engine it will be burn quicker therefore pushing the piston down just as fuel ignites,

 

hence more power and no knocking

 

evan.

 

 

when i went to kawasaki because my motorbike was fowling plugs like a mofo the guy there who is an ex racer told me that professional racers use 95 or 98 octane fuel because it burns slower and at high revvs colder than 91.

the reason you push the timing up when you run higher octane fuel is because the burn time is longer by milliseconds and the further you push timing the slower the fuel needs to burn therefore higher the octane.

 

thats my understanding of how fuel works.

[Evan G]

when i went to kawasaki because my motorbike was fowling plugs like a mofo the guy there who is an ex racer told me that professional racers use 95 or 98 octane fuel because it burns slower and at high revvs colder than 91.

the reason you push the timing up when you run higher octane fuel is because the burn time is longer by milliseconds and the further you push timing the slower the fuel needs to burn therefore higher the octane.

 

thats my understanding of how fuel works.

 

yea i getcha, where the hell is the technical moderator when u need him :dance:

[Taz_Rx]

There's a couple of us.

 

You guys seem pretty self sufficent here anyway. :dance:

[Jimpoole]

I used about 15 degrees. Any higher than that, and you will have problems starting it (I believe it's because the engine wants to turn the wrong way:) ). I thought stock timing was 8 degrees BTDC anyway? I was aware that using higher octane fuel in a well timed engine only really gave you higher low-end figures? Not to mention better economy :dance:

[Hiro Protagonist]

when i went to kawasaki because my motorbike was fowling plugs like a mofo the guy there who is an ex racer told me that professional racers use 95 or 98 octane fuel because it burns slower and at high revvs colder than 91.

the reason you push the timing up when you run higher octane fuel is because the burn time is longer by milliseconds and the further you push timing the slower the fuel needs to burn therefore higher the octane.

 

thats my understanding of how fuel works.

 

In short - higher octane = slower burn. Thus, advance timing (ie make it spark earlier) so fuel is finished burning at the same time as if it was lower octane.

[kiahn]

In short - higher octane = slower burn. Thus, advance timing (ie make it spark earlier) so fuel is finished burning at the same time as if it was lower octane.

 

 

EXACTLY!

 

haha best said simple like that.

 

and it is 8 degrees but thats at 2000 rpm at 750 rpm (warm idle) its 6 degrees due to vac advance i guess

[philbey]

wouldnt higher octane fuel burn faster? the more the octane the more BANG the camber will have therefor piston will be pushed down harder?

 

Not quite. It burns slower and in a more controlled fashion. explosions or faster burn just creates overly high cylinder pressures.

 

yea i getcha, where the hell is the technical moderator when u need him :)

 

this tech moderator is under his bonnet after doing a head gasket!

 

Also, you can run more advance because it is a slower more controlled burn. Sounds counter intuitive, I know, given that you need higher octane in high comp motors to avoid preignition!