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Advice on boost on L28


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Hey guys i was just wondering if you could give some advice on how much boost i can be safe with running on my L28. I have forged pistons, ARP head and piston rod studs, T3/T4 hybrid turbo, comp cam, intercooler, Supra 440cc injectors, Aeromotive fuel pump and regulator and an SDS (simple Digital System) engine management system. I do have stock 280 piston rods and a stock crank that has been balanced. I was going to get it tuned pretty soon and have about 800-1000 miles on it so far. How much boost would be safe to run on this kind of set-up?

 

Thanks. :willy_nil

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I doubt any of the guys that know what they're talking about on this forum will answer this question. It would be a total guess. What compression ratio and gas you are running is going to be a big factor. Every motor is a little different and the only way to know is tune it on a dyno. Maybe someone can give a hypothetical guess with some more info and has a very similar setup. 

 

Rob

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I understand its a type of rhetorical question, but was just wondering an idea or if anyone else has this type of setup like you said. Im running 8.3:1 compression on 91 octane pump gas. I am going to get it tuned on a dyno to know for sure and see how everything goes but i dont know what would be a good starting point. Thanks for the tip.

 

Steven.

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What forged piston? What head? Which comp cam? What size intercooler?  What FPR? T3/T4 Specs? 

 

You say you want to get it tuned soon, but it's SDS, how much tuning has been done so far?

 

How much boost you can run is directly related to knock. You can run as much boost as you want as long as you keep it out of detonation, but at some point diminishing returns will make it almost impossible to get more power because of heat. Where that is can depend on a million of factors, but it all comes down to one - HEAT!!!!

 

Why do we add an intercooler? To reduce HEAT!!!

 

What's the main thing that makes alcohol so bomb-awesome? It reduces HEAT!!!!

 

Why do people add water injection? To reduce HEAT!!!!

 

Why do people run larger turbos and get more power for a given PSI? Because it creates less HEAT!!!!

 

 

Heat is detonations best friend. Keep things cool and there's almost no limit to how much power you can run. If your longblock was built correctly, there's no reason it can't see 500+ hp...

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I'm running JE forged pistons, n42 head, intercooler size: 18"x12"x2.5" aeromotive fpr, and a 48mm turbo. Not too sure on the exact specs on the turbo. Also running 3" intercooler piping if that makes a difference?

 

I have not tuned the SDS it still has the stock tune from the factory.

 

That is true, keeping the engine cool creats optimal power. Thanks for the insight on that. I've researched about what kind of thermostat to use for a turbo motor and found that a 190 degree Fahrenheit was the most common.

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When I was planning to build my engine I did a ton of research online.  It was tough to find any concrete answers and/or equations to use in my calculations. I'm using a supercharger instead of a turbo, but figuring it out is very similar.  I read Corky Bells books, Maximum Boost & Supercharged, as well as all the other books I could find about boost and engine building. As a baseline Corky Bell assumes that detonation occurs when combustion temperatures exceed about 1075 degrees. You do everything you can to not exceed it. I created a spreadsheet with all his equations to build an engine for my goals in theory. I understood that using all his equations isn't going to lead to exact real world results, but I figured it was better than slapping a bunch of random parts together and experimenting blindly. What I did was pick a horsepower goal I wanted to achieve and work backwards from there. Practically everything is done to reduce heat. I didn't care how many psi I could run, I wanted the engine to flow enough to reach my horsepower goal. I better flowing engine will make the same horsepower with less boost than an engine that doesn't flow as well.  For a supercharger you need to size it using it's compressor map to match your engine and goals so it will be operating as close to the most efficient area of the map as possible. I think turbo's are the same, but I'm not 100% sure.

 

What I would suggest you do: Read "Maximum Boost" by Corky Bell and plug in your engine components into his equations. That would give you an educated guess. Then when you take it to the dyno, the tuner should be able to get as much as possible out of it safely. Hopefully, the power will peak before you experience any detonation.

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  • 1 year later...

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