Engine tweeking & tuning questions, About the only ones I haven't asked... Options

[ahdoman]

It's been awhile now since I got my teener and I think I've begun to really figure this stuff out thanks to you 914World adicts. But, I do have a couple of inquisitions for the engine tweaker guru's...
1) What is the relationship (if there is one) between engine heat and timing?
2) What is the realtionship between A/F mixture and engine heat?
3) As oil temp goes up does oil pressure decrease?

And finally...I finally got myself a real digital timing gun so I can truly check advance. I am running an 009 distro (I know Mallory or 050 would be better but no $ right now. I spent it all on my timing gun) and am trying to figure out just how bad it is. If someone else has a gun with adjustable advance would you be kind enough to tell me what your advance degrees are at;
1000 RPM
1500 RPM
2500 RPM
Why do this? Because I don't think my distro is properly advancing and I need to see how far off it is. Hopefully this will help me find it's "happy place".

[Aaron Cox]

take as many measurements as you can and plot the curve.... Advance VS RPM

and not all 009's are curved the same - LOL

[ahdoman]

take as many measurements as you can and plot the curve.... Advance VS RPM

and not all 009's are curved the same - LOL

Aaron,
I was planning on doing that at some point but for right now I just want to see what's "normal". Any idea if a curve plot of a 009 in our cars exists?

[Aaron Cox]

im sure you can find an advance chart on samba or shoptalk forums.

the grey/grey mallory spring combo has a steep advance curve that is in by 2900 rpm IIRC for what its worth.... (comparison data?)

[Bleyseng]

Too much advance =pinging and high heat
Too lean = higher engine temps
Oil temps don't lessen oil pressure unless there is excessive wear.

[ahdoman]

That's some good info Geoff. Any chance you also have an advance chart of what a stock 2.0 is supposed to look like?

[Dave_Darling]

Oil temps do indeed change the oil pressure! This very much goes for oil that is cold (cold starting), but it also to a lesser extent goes for oil that gets hot. Oil thins as it warms up, and even though the oil pressure control springs try to maintain the pressure at a specific point, they can't really do that through the engine's whole operating range. And, of course, if the engine is working outside its normal operating range....

--DD

[ahdoman]

Oil temps do indeed change the oil pressure! This very much goes for oil that is cold (cold starting), but it also to a lesser extent goes for oil that gets hot. Oil thins as it warms up, and even though the oil pressure control springs try to maintain the pressure at a specific point, they can't really do that through the engine's whole operating range. And, of course, if the engine is working outside its normal operating range....

--DD

Thanks Dave, I thought so. BTW - I've been all over your site looking for info on the 009 curve and it looks like nothing is there. I found this page - http://www.pelicanparts.com/techarticles/9.../914_timing.htm
but I am having troubles identifying the distributor part #'s. Which one is the stock 2.0 distributor?

[Bleyseng]

Oil temps do indeed change the oil pressure! This very much goes for oil that is cold (cold starting), but it also to a lesser extent goes for oil that gets hot. Oil thins as it warms up, and even though the oil pressure control springs try to maintain the pressure at a specific point, they can't really do that through the engine's whole operating range. And, of course, if the engine is working outside its normal operating range....

--DD

The relief controls the pressure at 42lbs whether its cold or hot...only when the engine is worn can it not maintain the 42lbs as the clearances are too big for the thin oil. (at 4000rpms)

[Dave_Darling]

The relief controls the pressure at 42lbs whether its cold or hot...only when the engine is worn can it not maintain the 42lbs as the clearances are too big for the thin oil. (at 4000rpms)

If you're below 4000 RPM, the pressure can easily be lower. When the oil is colder, the pressure will be higher at (say) 2000 RPM; when the oil is warmer the pressure will be lower.

And in my experience, very cold oil (cold-start) will have much higher pressure than 42 PSI. Actually, in my car the relief appears to open at about 50 PSI.

--DD