Tuning timing with EGT Options

[james2]

If I tune AFR with a wide band, would it be safe to say optimum timing = Lowest EGT?

[james2]

no one? i can't find much info on this, some info for using EGT for AFR. But with wideband, why would you need EGT for AFR? (IMG:style_emoticons/default/confused24.gif)

So, I'm reading and couple articles say retarded timing will also cause high EGT.

Then another article i read, says the retarded ignition timing doesn't ignite the mixture soon enough and the burn continues in the pipe.

2+2. (IMG:style_emoticons/default/idea.gif)

So, if I keep advancing my timing until EGT just drops, then I will know that combustion has been completed in the cylinder, and I'm getting max power, economy. (IMG:style_emoticons/default/aktion035.gif)

Or I'm I full of BS?

[SLITS]

1200 degrees F is FAT

1600 degrees F is lean detonation

Tune to the lower number .............

Try a timing light for better results.

[james2]

I think you have largely missed my point. I have a wideband o2, and a timing light.

What my AFR or timing advance is not a mystery to me.

What the optimum timing for any given throttle load and rpm, is.

[SLITS]

That you would have to get an opinion from Mr. Raby ....

A long time ago, in another galaxy (different board), someone published the advance cures for the Type 4 engine dizzys.

[james2]

Found this-

LINK

[DBCooper]

Really excellent article. These paragraphs are good:

If, however, you have a chamber design that burns very slowly, like a mid-60s engine, you need to advance the spark and fire at 38 degrees BTDC. Because the optimum 14 degrees after top dead center (LPP) hasn't changed the chamber has far more opportunity to detonate as it is being acted upon by heat and pressure. If we have a fast burn chamber, with 15 degrees of spark advance, we've reduced our window for detonation to occur considerably. It's a mechanical phenomenon. That's one of the goals of having a fast burn chamber because it is resistant to detonation.

There are other advantages too, because the faster the chamber burns, the less spark advance you need. The less time pistons have to act against the pressure build up, the air pump becomes more efficient. Pumping losses are minimized. In other words, as the piston moves towards top dead center compression of the fuel/air mixture increases. If you light the fire at 38 degrees before top dead center, the piston acts against that pressure for 38 degrees. If you light the spark 20 degrees before top dead center, it's only acting against it for 20. The engine becomes more mechanically efficient.

That reference to the mid-sixties combustion chamber hits Gene Berg's semi-hemi chambers on the head. And then one step further, that second paragraph explains why two valve pushrod heads will never be able to match the modern pent roof designs, even with old-school double plugging like Jake's been trying to do. I like old cars, but what I REALLY like is cool stuff, in any form. Irony here is that I heard recently that the Northstar engine's production's been canceled, on to something even more advanced. Good one James.

[Bartlett 914]

no one? i can't find much info on this, some info for using EGT for AFR. But with wideband, why would you need EGT for AFR? (IMG:style_emoticons/default/confused24.gif)

So, I'm reading and couple articles say retarded timing will also cause high EGT.

Then another article i read, says the retarded ignition timing doesn't ignite the mixture soon enough and the burn continues in the pipe.

2+2. (IMG:style_emoticons/default/idea.gif)

So, if I keep advancing my timing until EGT just drops, then I will know that combustion has been completed in the cylinder, and I'm getting max power, economy. (IMG:style_emoticons/default/aktion035.gif)

Or I'm I full of BS?

That was a very interesting read on Detonation and pre-ignition. I did see this comment about EGT that applies here to your question:

"The other technique is a little more subtle but usable if attention is paid to EGT (Exhaust Gas Temperature). Detonation will actually cause EGTs to drop. This behavior has fooled a lot of people because they will watch the EGT and think that it is in a low enough range to be safe, the only reason it is low is because the engine is detonating."

[ArtechnikA]

You do not tune timing with EGT, you tune mixture with EGT.

Aircraft guys like to tune to 50ºF Lean of Peak in cruise.

[james2]

From reading some other forums, some tuners can tell if they don't have enough timing, because the EGTs increase. but that article is saying detonation will cause a drop also.

So I figure you need a EGT and a knock sensor. Just increase timing until EGTs drop or you get knock.

[james2]

The wideband o2 meters have made tuning AFR with EGT out dated. People do tune timing with EGTs.

You do not tune timing with EGT, you tune mixture with EGT.

Aircraft guys like to tune to 50ºF Lean of Peak in cruise.

[Jake Raby]

EGT gives the best indication of engine optimization.

Our race engines are tuned solely by EGT.

BUT EGT is only an effective tuning tool at WOT, part throttle operation will create high EGT no matter what, at part throttle AFR is the best tuning tool.

James, you should attend my Tuning workshop being held this Winter here at the shop.. Three days of class room and practical application education...

Because I am tired of people now understanding how to tune!