Quote:
Originally Posted by wnta1ss
This is a common problem with boosting a stock LT1, and the reason why it's common is already known. The factory is doing tight ring gaps, sometimes ridiculously tight. Shops have seen top ring gaps of .007" or .009" which is crazy. This means it's rolling the dice when you boost these, because yours might be really tight or just tight. Cooling mods like methanol injection or using E85 probably help to some extent by cutting down on the heat (less heat equals less chance of rings butting together and breaking the piston). But there is only so much you can get away with when the engines are assembled so wrong for using this type of modification.
Guys, boosting an engine always contains some amount of risk, we know that. But with THIS issue in the LT1, the risk is more than we'd normally feel that it is, so go into this knowing that the chances of breakage are increased on this engine. Unfortunately most people here parrot the fuel and tune stuff that is just generic to going boosted. The truth about the piston rings is ignored by those people, but it should absolutely be considered when thinking about boosting a stock LT1. Since heat is such a big issue, how you want to use your car will effect the chances of breakage. The guy from Procharger for example said to keep it to short runs of not longer than a 1/4 mile. Obviously longer runs or more boost would mean more heat, and therefore more likely to break. The fact that so many people with supercharged LT1s only screw around on the street, or just do short runs up to a 1/4 mile, gives a false sense of security. People say crap like so and so has 700hp or so and so has 800hp. Completely ignoring though, how many of these things have broken. Like I said, it's rolling the dice, you might be lucky or you might be on a tow truck. To be clear, I'm not flatly saying you should not supercharge your LT1, I'm just saying that you should understand how these engines are built, so that you can carefully evaluate what your use of the car and boost level chosen could mean with regards to these piston rings.
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There is no question you are on point but at the same time we have to know what causes the rings to butt in the first place.
I think everyone wants to blame boost or a HP number, but that is not the core of the issue.
We successfully supercharger engines from all walks of life, even the ones that everyone says to stay away from, we do more than Chevrolet cars here, we do GM, Ford, Chrysler, Jeep and Trucks from all the Domestic brands.
Combustion Temp, Water Temp, Air Temp, Air fuel ratio, octane and Timing all effect the final combustion temp, which is what controls or causes ring growth.
You can achieve much higher power levels and maintain
same combustion Temps, or final ring temps.
I see too many combinations that are run
way too lean, or over 570 RWHP on Stock fuel systems, which is the biggest contributor to high combustion temps and eminent engine failure.
The internet said I should run my DFI engine at 12.8-13:1 AFR and I call bullshit.
I run my supercharged DFI engine at .80-.82 lambda or 11.76-12.0 and they live even at high power levels and high duty cycle.
I have run up and down the AFR or Lambda Scale on my dyno with every engine combination and I always end up back at -.80-.82 for best mean torque and engine life.
I will go richer for higher duty cycle combinations
Some of this fuel is wasted in cooling the piston and rings.
Food for thought and is by no means specific to this thread.
Ted.