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Old 01-01-2012, 06:09 AM
Gen1dak Gen1dak is offline
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Join Date: Aug 2011
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Engine: 1988-1991 318ci (5.2L) LA V8 140hp
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So a turbo isn't practical. Well, let's look at that a minute. Take the 318. Figure 90% volumetric efficiency for the typical stocker. That equals approximately 286 cubic inches actual displacement in a naturally aspirated engine. Now, while up to around 9 psi IS SAFE FOR CAST ALUMINUM PISTONS (can you hear me now?), let's just figure on 7 psi. That's 1/2 atmosphere. So, with positive displacement under boost, you're looking at 150% displacement at 7 psi. In other words, at roughly 100% volumetric efficiency, a turbo 318 at 7 psi is displacing 476 cubic inches. Even if you weight that against less than ideal flow and the exhaust restiction imposed by the turbo, let's say you actually net 450 cubes under full boost. Are you seriously saying that going from natural aspiration of around 290 cubes to over 450 cubes isn't practical??? Even if the engine made 1/2hp per cubic inch that's an 80hp increase without touching anything else. In reality, it'd be closer to 3/4hp per cube on the typical stocker, meaning 120hp. Toss in a better cam and a couple tweaks and you have 1hp per cube. You've gone from 230 to 450. No way will your higher rpm + other mods approach come anywhere close. And how much higher could you go with that higher rpm scheme? Regular duty over 6,000 rpm's requires HD hardware (crank and rod bolts). Start pushing 7 grand and you need a forged "steel" crank and stronger rods. Now for the disclaimer. These numbers aren't cast in stone. Your mileage may vary, but the theory and reality are very close here, and it's basic physics at work. Your Dakota turbo fellow used too much boost or too much ignition timing, or both.
Regarding forged pistons. Umm, they're still aluminum, not iron. You think they'd cause too much drag? Tell that to EVERY 426 Gen II Hemi owner (and most other legendary engines ever built), EVERY race engine builder, every diesel ever made. They are designed to slightly greater tolerances so that when the FORGED ALUMINUM expands, it seals optimally. Confuse the PCM? There's this little thing called a timing chain. It keeps everything in correct time. The reciprocating system would need to be rebalanced for the heavier pistons, just like if a stroker kit were added, or you added all the guts I listed for high rpm's.
Finally, just because someone with more money than knowledge bolts something onto their engine and it blows up doesn't mean it won't work. It does mean they didn't know what they were doing.

Last edited by Gen1dak; 01-01-2012 at 06:57 AM.
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