ISX 2350 485

[gearhead]

(02-03-2017 )Magard Wrote:  Hey gearhead, I the spirit of understanding. Can you tell me if the boost pressure is measured at the intake manifold by a manual gauge wouldn't that indicate how much charge flow can enter the cylinder through the head. Smaller ducting to the intake manifold should equal more velocity less time to cool in charge cooler but same charge volume just less dense because it is warmer. Anyhow you can probably tell I'm in a Volvo. When I seen that air compressor snorkel I thought that was more restrictive than anything else in the system.

Chargeflow is calculated based off of several things one is boost others are things like turbo speed,egr delta pressure,exhaust backpressure. It is a measure of volume of air so yes smaller piping will reduce volume. Think in terms of a hose, lets say that i have a 1 inch hose and i am pushing water threw that hose at 20psi. Now take anouther hose at 3/4 inch and pump at 20psi you will not get the same amount of water. So increase the pressure of the 3/4 hose to 30psi and you might get the same amount as the 1 inch hose. Now let me stop and explain i have in no way said that these figures are correct i have not done the math LOL. Just an example. But in terms of your engine you would be way better off in some ways to be with the 1 inch hose. The psi is lower but yet you get the same volume of air. This reduces backpressure on the engine because of the ratio law with turbos. Lets say your turbo for argument sake has a 1 to 1 ratio which is dam good under full boost. With that being said if you make 1psi of boost you would make 1 psi of backpressure between the exhaust output and the turbo. With the vgt on the cm2250 and the cm2350 the ratio is more like 4 to 1 at full boost. So now we have an even bigger problem with things because the more boost you build the more backpressure you build.
So that's part of the reason for running less boost. I have learned that when you try to push the turbo at 40psi you are making so much backpressure that you are literally working backwards. The more you try to push it the exhaust cannot get through the turbo. So your fuel mileage will suffer from this. It's like a giant balancing act with making the motor last as long as possible. Keeping the backpressure low and cylinder pressure to a minimum will make the head gasket and liners in better shape. I do not wish to disagree because rawze in fact is correct. I only try to explain what i have seen and to help everyone to understand why the high boost can be a problem on a higher compression engine like the common rail cummins. I have a hard time putting my thoughts into writing so sometimes i word things in a weird manner and sometimes i will type something in a manner that looks different from what i ment to say if that makes any since.