[jessrayo]

Originally Posted by Speedy1975

I've read this a few times, the coating coming off, and the consensus was that it wasn't a big deal. Did you experience other wise? Mainly Vette guys I saw doing it commented that the coating coming off didn't affect anything for them so curious what your experience was?

I built my Challenger's motor to 9:1 compression. Knowing what I know now, I would have gone a bit more on compression (10.5:1) and run less boost. I calculated I'd make the same power on less boost, meaning cooler IATs and a happier setup. 11.5:1 is getting up there, but do you think it's that big a deal to just run a bit less boost? Making 560 on 7psi seems pretty good to me. I'm waiting for some of the track folks to bump it to 9 or 10psi on 109 race gas and see how it goes. Had a buddy run 10psi on his stock R/T Challenger and everyone said he'd blow it up. He only ran that at the track on Sunoco 110 and 3 years later he was still going strong. He eventually had a a built motor put in, had all kinds of issues, and sold the car wishing he'd left it a lone LOL.



Thanks, fingers crossed they fixed whatever the problem was.

I could feel no change in performance even though probably 2/3 of my rotor coating was gone. But I was running compound boost with turbos pressurizing the intake tube before the supercharger. So not exactly the same as just supercharger performance, my supercharger was just jump starting the turbos so I didn't have as much lag. Turbos were pushing most of my boost.

I also only ran that configuration with the heartbeat and methanol for a few hundred miles. I really don't know how it would play out long term. I personally don't think I would spray methanol into a PD supercharger again, the supercharger coating is there for a reason. I'm sure if you talked to Maggie of Eaton engineers they could give all of the exact information but I really don't know.

Regarding the compression ratio, there is a lot of variation available between ignition advance, compression ratio and the fuels inherent detonation resistance. There are a few basic principles that come into play. All of these are relative however....
1. The more you compress the air fuel mixture the faster the spark will pass from molecule to molecule and the more power can be made. This works right up to the point of detonation. Once you get to a point of detonation it is all lost. So ideally the closer you can compress the air/fuel mixture to the point of detonation without actually crossing the line the more fuel efficient and powerful the engine will be. The LT1 motor is optimized for no boost and really is incredibly efficient and powerful because it is already pretty close to the limit. The tolerances are so tight that you can really only add 5 to 7 pounds of boost to a stock motor before you have to take away some of the efficiency.

2. Spark advance/retard is one way to modulate compression and the tune of the engine is adjusting this constantly. The problem is there is a range of effectiveness. All of this varies with engine rpm but lets just say for peak power at high rpm, If your spark is being retarded honestly less than 15 degrees before tdc you are losing the most efficient push on the piston. You will still make power but not as efficiently. To keep stuffing boost into this LT1 engine without adding some fuel to resist knock (E85, meth, race gas) the timing will quickly move out of max efficiency range due to high compression ratio.

Because of the compression ratio, this engine is going to LOVE E85 and race gas. If you have a separate tune that allows more advance the power gains will be major. But us bums that want to run pump gas are going to be kind of limited with this motor. On premium pump gas I think 550-575 whp is the sweet spot on this 11.5 to 1 motor. You can push more air and fuel into it but the efficiency is going to drop if you are not using a stabilizing fuel.

On your challenger 9:1 is on the other extreme, you could easily make 1000 whp on pump gas with that ratio if you can get the air and fuel into the engine. You could run all the spark advance you wanted with no detonation.