Lotus Elan and Lotus Elan Plus 2 Forums

Ok Your lost ????....spend an afternoon wandering around the garage with a hose in your ear and you will find the way out ..

twincamman wrote:Oiiiiiii....runners make headers ...that run into 4 into 2 into 1 collectors and that runs into the exhaust tube ........and that's attached to the rib bone....this causing me exhaustivity

Doesn't that song end: "Hear the word of the Lord?"

Amen.

More like ...unhu unhu ..Elvis has left the building ...oi vey

Some thoughts and comments

Prior to retiring, I was a thermal engineer for an aerospace company that designed and built commercial and military jet engine mounted digital fuel controls. Heat and vibration were big concerns. I was responsible for the prediction and verification of the temperature of the control as a whole and all of it's individual internal components, throughout the operational envelope. Analysis was by computer simulation and verification was by test.

During product development, I used a very expensive FLIR brand infrared (IR) camera to visualize the temperature of the individual components at the printed wiring board level, under various operating conditions. I was looking for components that were running hotter than predicted. I did this for various operating conditions. I also looked at the control as a whole as when exposed to a 2000F external fire condition, a very dramatic test. In all cases, we used at least some thermocouples to check that the IR measured temperatures we got matched the thermocouple temperatures at the same location.

The spot IR thermometers you are likely to use depend heavily on the emissivity of the target surface and the distance from the target surface. Too far away and you will likely start to pick up an average temperature of everything in its field of view. Two inches from a tube seems to be a reasonable distance. Make sure the target surfaces have the same surface finish, whatever it is. Your are looking for relative temperature comparisons. For spot temperature comparisons, its best to take temperatures under steady state conditions. That is, wait until all temperatures have stabilized, then rapidly sample the 4-primary tubes in succession, at the same relative locations on the tubes.

I'm not sure how accurate tube temperature measurements will be in determining mixture. At low rpm, how do you know if temperature differences are caused by mixture or imbalance?

Does one adjust mixture for maximum tube temperature, all else being the same?

If one starts from a known too lean condition, there will be no burn and no heat generation. As one gradually richens the mixture intermittent firing will occur and the tube temperature will rise. Continuing to richen the mixture will result in a reliable steady burn and the tube temperature will be hotter. If one now richens the mixture more, does the tube temperature begin to drop?

How do you know when your are at an optimum mixture? It's one thing to match temperatures if one cylinder is known to be at the desired mixture and quite another thing to dial in that first one, when there is nothing to compare it to.

Does the direction one approaches the target mixture matter? If one approaches form a too lean direction does one get the same result as if one started from a too rich condition?

The best method for setting mixture IMHO, is to install gas sampling tubes in each primary tube. This is what Ferrari did for their carb cars. One sets the mixture of each cylinder to a particular % CO (usually 4-6% for Webers) and then you are done for the idle condition. Mid and high rpm/load conditions can be sampled at the collector or tail pipe as an average value as I have never known anyone who would use different idle jets, air correctors, emulsion tubes, or main jets in different cylinders of the same engine. One usually keeps all carb fixings at the same specification, so tail pipe sampling works well. Individual cylinder mixtures are usually only important at idle.

Bill