I am considering adding a turbo to my 5.3L, which has about 240k on it, all stock. I am not looking to get a ton of boost, but an considering a bifuel CNG conversion and wouldn't mind seeing some performance increase instead of decrease, CNG has less energy density than gasoline, needs more air, and is around 130 octane so adding some boost - I think - may be a good way to achieve this. I'm thinking maybe around 5psi - it still needs to work on premium pump gas.

My question is - what type of stuff do I need to worry about with my motor? From reading, sounds like the tune and valve springs would be a main consideration - and to get a compression/leakdown test to check the condition of the engine.

I will be replacing/rebuilding the transmission prior - as I can't imagine that lasting much longer under any circumstances.

Thanks for any thoughts and info!

 

Ive never run CNG but Ive delt with more LPG trucks than i care to admit to. Is CNG is anything like LPG it will be hard as hell on parts and by its self will destroy that motor with out boost. Now please keep in mind I'm speeking about LPG and not CNG so I'm not sure how closely related the two are..... not sure how much this will help you if at all but here it is anyway.

 

Don't need to change the valve springs unless you are going with a different cam. But engine life will depend on having the tune dialed in more than anything else, especially when (not if ) you turn up the boost.

 

Yeah... I am not sure - I've done some googling but have not come up with anyone that says anything bad, except the CNG burns hotter than gas, and because it's a gas and not a liquid it also does not cool as well... that can lead to burned valves. Otherwise, people say it burns cleaner and does not wash oil off cylinder walls etc. Really, it appears there is no consensus -but most articles seem to point to increased engine life, with 240k on the truck, I'm willing to give it a shot.

What type of issues crop up with LPG vehicles?

 

To be such a clean burning fuel… LPG is a dirty dirty fuel. The company I worked with (Bi-Phase) was the first company to market multi port LPG injection and as of 2012 is the company that GM is working with for of their LPG vehicles. It is hell on all your parts and to be ~-41deg F in liquid form it too burns much hotter than gas and has a more violent combustion. We saw quite a few burnt valves, broke valves, it cooks oil (even fully synthetic), the cold dryness is hell on anything plastic or rubber (injectors/fuel lines), and most of the engines only made it ~120k miles before needing to be replaced due to anything from premature wear but mostly just destroying themselves.