mnengr

Does any one know why the waste gate is set at 20 and the ecm gives codes if your going over that? Was it emissions?

smokindog

It might be emissions, might be that more boost usually requires more fuel, and we all now more fuel is mo' power

I have 4 Class 6 Trucks all with 260/660 Cummins 24V ISB's in them. They are boosting between 28psi-33psi and I have never made any modifications to those trucks.

I wish I knew the answer to your question, but.... someone here should know!

HOHN

21 psi or so is the peak efficiency of the turbo. This gives the most O2 into the engine at the lowest temp. This means the engine will run the leanest, and the coolest, which helps NOx emissions.

That's my theory, anyway.

smokindog

Ahh,

Thanks for pointing that out Hohn! I am, of course, referring to HX35 equipped units!

BigBlue

There's really no point in upping the boost if there's no additional fuel. More boost doesn't not equal more fuel. In some instances it just means super heated air that raises EGT's. Emissions also play a big part in it.

mnengr

With big NG burners (30 million Btu) we try for excess air to get more complete combustion. Low NOx and CO2is usually maybe 5-10% excess air where higher efficiency is in the 30% range. I know Maxon can tune the emissions based upon that ratio. So more air might mean you get all the bang you can out of the burn. running the flame rich just cools off the burn. Not sure how that fits in, but combustion is combustion right?

Fueling around

Big difference between open & closed (external & internal) system combustion.
An open system such as a NG burner is not really going to generate excess NOx as the pressures are not there to force the nitrogen conversion.

Spark ignition engines operate under a very narrow air/fuel ratio around 14.7 to 1.
Compression ignition (diesel) engines operate in a very large ratio from 90 to 1 to less than 1 to 1

Why the low boost pressure? Emsissions. The cam & ECM are different from a commercial unit.

apwatson50

Lean conditions generate more NOx rich conditions generate less NOx but more COs and in a diesel that means that not all the fuel was burnt.

20psi is what the factory set it at because thats all the power they wanted out of the truck and thats all the boost they needed to efficiently burn the fuel they were injecting. The factory has to worry about emmissions, advertised MPG, and advertised power. So they have to do things to insure that the trucks they produce will do what they say it will do!!