20° BTDC for spark timing instead of the original 25°.

[Thruster87]

Has anyone adjusted the timing on the 3300 solid lifter to the folowing:

 

Note that late-model 3300 engines

 

The new part has been indexed to give 20° BTDC for spark timing instead of the original 25°. These are engraved with "20° BTDC". This change was made to improve the engine‟s tolerance to lower-grade fuel and it is recommended (but not mandatory) that the new part be fitted to 3300 engines at full overhaul

 

 

[Guest DonC]

Has anyone adjusted the timing on the 3300 solid lifter to the folowing:Note that late-model 3300 engines

 

The new part has been indexed to give 20° BTDC for spark timing instead of the original 25°. These are engraved with "20° BTDC". This change was made to improve the engine‟s tolerance to lower-grade fuel and it is recommended (but not mandatory) that the new part be fitted to 3300 engines at full overhaul

Don't do it!

I bought a new engine with retarded timing - won't pull the skin off a rice pudding. Lost at least 150 rpm and runs hotter.

 

Now I have to change it back to 30deg! Sorry, 25 deg

 

 

[facthunter]

I've tuned and timed a lot of engines and I don't believe that 20degrees is enough on this type of motor. The plugs being close together means you don't get much beneficial effect from twin plugs, and the engines that do have them on opposite sides of the combustion chamber usually run around 28 degrees.. Loss of power and hotter running would be the normal result . IF the engine runs hotter it's tolerance for low octane fuel will reduce. Nev

 

 

[fly_tornado]

So why would Jabiru release this sort of upgrade if its taking the engine in the wrong direction? They must have found something in their testing to suggest this is the correct direction. I wonder what it was.

 

 

[turboplanner]

I'm scratching my head at this too, unless they've changed the compression ratio.

 

Before messing with it, I would make a phone call to Jabiru - it's certainly important enough to get an exact explanation compared to the cost of a phone call.

 

 

[facthunter]

I understood they had already lowered the compression on the 2200 motor, which was producing well above the 80 HP stated. This (I think) is the 3300, only. Nev

 

 

[Guest DonC]

I understood they had already lowered the compression on the 2200 motor, which was producing well above the 80 HP stated. This (I think) is the 3300, only. Nev

Compression on 3300 has been lowered too by longer cylinders.

Their reason for retarding the ignition is to prevent detonation for pilots that use crap fuel!

 

 

[brilin_air]

Compression on 3300 has been lowered too by longer cylinders.Their reason for retarding the ignition is to prevent detonation for pilots that use crap fuel!

You can generally make something fool proof but it is hard to make it idiot proof

 

Brian

 

 

[jetjr]

"So why would Jabiru release this sort of upgrade if its taking the engine in the wrong direction? "

 

They did it with the hydraulic lifters??

 

Seriously though I was discussing this aleration with someone there they claim they had run both setups on thier dyno with no measurable difference.

 

Im thinking detonation might be becoming more prevalent with more Mogas use, might relate to through bol tupgrades and this retrdation too?

 

 

[facthunter]

I'm sure they have problems with detonation, as they have been blaming the bolt failure on it. THAT seems logical to me as It is extremely destructive on a motor. I've NEVER managed to get any but the most modern 4 valve heads with centre plug to run well with that small amount of advance. They just go dead, idle well but don't deliver power and run hot ( especially in the exhaust port area). This would make the exhaust valve hotter which could easily cause detonation on its own. It's usually the hottest thing in the combustion chamber, ( besides the plug insulator). Nev

 

 

[Guest DonC]

I'm sure they have problems with detonation, as they have been blaming the bolt failure on it. THAT seems logical to me as It is extremely destructive on a motor. I've NEVER managed to get any but the most modern 4 valve heads with centre plug to run well with that small amount of advance. They just go dead, idle well but don't deliver power and run hot ( especially in the exhaust port area). This would make the exhaust valve hotter which could easily cause detonation on its own. It's usually the hottest thing in the combustion chamber, ( besides the plug insulator). Nev

Apart from the dismal performance of the new engine, I can now report a consistent rise in fuel consumption of 4 lt p/h.

 

That, combined with a huge rev drop when pulling carb heat, or switching a mag off in flight, points to inefficient combustion due to retardation

 

 

[jetjr]

This all points towards needing smarter fuel metering as fuel quality changes - bring on EFI