Basically trying to find out how easy or make that how hard it would be to make a 747 ecm read boost on a 2 bar map sensor. I know it could be done with the proper coding.

Anyone attempted it?

Maybe I should just use a FMU for fuel and a check valve to blow off pressure so that the standard map sensor does not see boost?

 

Too much trouble making a '747 read boost. Don't need a blow off for the 1 bar MAP either. It will take some overpressure w/o damage.

Now, if you aren't making more then 4-6 psi, and the Weiand is a positive displacement (I believe it is), then the boost tuning can be made within the normal '747 tables. With a positive displacement blower the boost will be the same at each RPM point eacha nd every time, unlike a centrifugal blower where it can vary at the same RPM.

I believe it was Lyndon that did this type of tuning for a number of engines and it works.

The engine will need an appropriate increase in fuel delivery (injector size and/or fuel pressure) for the increased HP.

RBob.

 

You pegged it exactly. The weiand is a positive displacement mini roots style blower that makes 4-6 psi of boost. Probably about 5 on a TBI motor.

How can the boost tuning be made in the stock tables? They only go to 100 KPA. Would you just measure the MAP at the throttle body instead of under the blower?

I am thinking that the GM vacuum compensated regulator that everyone uses on the TBI will also raise fuel pressure when boost is put on the line. It is just a diaghram that works on a spring. Vacuum equals less pressure, so boost should equal more. The TBI is going to be in atmospheric pressure and not boost so the pressure rise is going to dump more fuel.

What about going romless and converting to a Mass air flow based TBI like dimented.

 

Don't bother answering the stock table part. I got to thinking about it and if boost at a given rpm and map is always the same which it should be their is no problem. Even if the MAP is seeing vacuum and the engine is in boost with the right numbers in the tables their isn't a problem.