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Re: what is this distributor mod i been hearing about
Posted by binky (more from binky) on Tue, 22 Nov 2005 18:20:06
In Reply to: Re: what is this distributor mod i been hearing about, MS, Tue, 22 Nov 2005 11:08:03
If you're concerned about damaging your engine, why run more boost? ;-)
Try this: Modify a capsule to follow your explanation, that is, to allow a bit more boost retard while maintaining the same 16 degree BTDC static timing and 21 degrees max advance. So you now have say 10 degrees BTDC instead of 11. Go for a drive. Now modify a capsule as I outlined. Go for a drive. I'll buy you a grape soda if if you prefer the first capsule! :-)
2.2/2.4 engines are sensitive to timing under boost: all the difference in the world can be just a degree between knock and no knock. Beyond 10 degrees BTDC you are starting to lose power, as peak pressure occurs too late and combustion is more incomplete when the exhaust valves open. If you have knock beyond that, more retard won't gain you much of anything even if it stops the knock.
As for harming your engine: Yes, prolonged spark knock can hurt it. But it is audible. If you hear it, just take out some advance. Cars are engineered to take some knock - EZK actually advances timing until knock occurs, allows it to happen, then adjusts itself. And if every engine knocking up a mountain pass couldn't take it, most of the junkyards would be at those passes, full of dead cars.
And you are also running high octane fuel. And you are running an engine with a relatively low compression ratio. And an efficient 4-valve head, one that was designed for the heat of forced induction operation.
5 degrees of off-boost advance is not an issue.
Yes, there is a bit more heat with advanced timing - use a colder plug if you want.
I notice no change in off-boost high vac running temps, e.g., highway cruising. If you have the octane and no knock, then it's not an issue. Saab designed the timing with plenty of padding for poorly maintained cars, bad gas, etc. By the way, my car with 87 octane and 19 degrees static timing recently kicked butt at the emissions dyno: NOx levels were just fine (high NOx means too lean/hot in the chambers).
People have been running more advance on NA engines since forever. The principle for the turbo Saab is no different except for the need to keep the retard the same under boost. Actually, the Saab lucks out: NA cars gain more low end at the expense of high rev torque, whereas the Saab loses nothing up high.
That all said, the Saab capsule, as mentioned, is a crude timing device. If you are serious about getting more power from your engine, electronically controlled timing is much more flexible. Fuel is important for power and all, but without good timing, you miss out on a lot of power potential. In other words, go with an aftermarket ECU.
posted by 65.34....
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