The stock cast iron manifold would be suspect at a 100% duty cycle.= It=20 would be unusual to operate a street turbo car at full throttle for more= than a=20 few seconds. Cast iron does not perform well when over heated and stressed= at=20 the same time. It is easy to cast, and the cheapest material that will wor= k in a=20 car engine.

A small blast tube directed at the header tubes works wonders to make= non=20 turbo headers last to TBO.

Once quit using .125" wall SAE 1010 tubing my normally aspirated= =20 racer, and went to .135 Wall SAE 1010 tubing, I had no more header=20 problems. Even the thinner wall on the outside of bends holds up. The same= wall=20 or thicker in stainless would be fine, it seems to me. Easy to make from= =20 Handrail pieces. The turbo must be braced to the engine

in every case, to lower stress on the headers and turbo parts.

Lean mixtures are easy on the pieces in piston engines. Lower EGT, lo= wer=20 head temps, fewer exhaust valve heads falling off, Longer TBO and much low= er=20 fuel flows. Used on every round engine to cross the Atlantic. In the rotar= y the=20 same things, however, less fuel flow means less seal lubricant if you= =20 premix.

A real ignition system will light a far leaner mixture than a Ketteri= ng=20 system. A Mallory High Fire or MSD6AL

or similar, at least on the leading plugs. So any fuel setting will= run=20 smoother.

You can run rich at 1600 degrees or a bit less at take off and climb,= then=20 switch to lean to 1600 degrees at cruise, same as piston engines. Piston= engine=20 use the excess fuel for cooling and detonation protection at low altitudes= . Both=20 over lean, and over rich mixtures burn more slowly, and the richer mixture= =20 limits available oxygen, and cools the chamber.

Detonation is charge temperature dependant.

Over lean mixtures can stand more ignition advance than ideal (Best= power)=20 mixtures, so leaning also reduces ignition adjustment requirements. Moving= =20 ignition timing is done to keep highest cylinder pressure at about 50= =20 degrees after top dead center (ATDC). Adding boost increases effective=20 compression ratio, and moves the highest cylinder pressure point around.= More=20 boost, higher pressure, faster burn rate, Higher pressure closer to TDC,= lower=20 pressure further from TDC.

So the ideal advance will be different on each day.

You might tune the B controller for cruise, and the A controller for= take=20 off and climb.

Lynn E. Hanover

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