Industrial gas engine exhaust backpressure minimum?

[Bribyk]

Any idea why an engine manufacturer would specify a minimum exhaust backpressure on both NA and turbo'd models?

I need an exhaust system that will work for a wide variety of engines and outputs. The system needs to be large to keep the pressure below the maximum spec for the biggest engines but results in little backpressure (below manufacturer's specs) for the smallest engines.

 

[ivymike]

I know I've seen a couple of patents on backpressure valves for EGR-forcing (International, someone else I can't remember), but I can't recall ever seeing such a system in person. Do you happen to know of any current-production vehicles using that scheme?

 

[dgallup]

I'm with GregLocock. We always used a butterfly in both the exhaust & intake to set pressure drops to standard values when I was a diesel engine development engineer. We didn't cover quite that big a range, only about 170 to 700 horsepower but it worked well.

 

[Bribyk]

Thanks, all. I will look into adding a butterfly valve to the system and possibly an actuator/controller so that the system is automated.

 

[tom5923]

Does anyone know if there are standard specs for exhaust backpressure tolerances for gasoline engines. Specifically, do OEM's specify upper BP limits for aftermarket mods to exhaust systems? Also are there published general standards for lower and upper limits for backpressure. I test facility told me that 0.5PSI change at the lower and 2.0PSI change at the upper were accpetable for modifications to exhaust systems. They could not provide the actual reference though. Thanks.

 

[Bribyk]

Is this for an industrial gasoline engine or vehicle? You likely won't find numbers for a vehicle because they come with an exhaust system already. Why would you increase exhaust backpressure anyway? Industrial natural gas engines typically specify a max backpressure of 10-12 in w.c. (.36-.43 psig) for NA engines and 15-18 in w.c. (.54-.65 psig)for turbocharged. Aim for zero, 2 psi is wayyy too much.