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Supercharger help

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Old 08-07-2011, 08:31 AM
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Supercharger help

I have a Scarab with a stock 502 mpi. Looking hard at putting a 5 psi supercharger on it. One problem is there is no marina here with premium fuel,only 87 octane. Does anyone have any advice? Short of putting a bigger engine I thought the charger is the only way to go. Just want to go fast! Oh ya Whipple says 92 or higher only! I can't see all those boats out there running premium gas!
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Old 08-07-2011, 08:41 AM
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I only run 93 in mine. I do have several bottles of this I keep on board in the event I can only find 89:

ValvTect Octane Performance Improver

http://www.valvtect.com/marineGasAdditives.asp


As a general rule I will not use 87 in my boat. Not worth the risk.
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Old 08-07-2011, 08:54 AM
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What type of charger set up are you using? Does that octane boost really work? Some say it is a gimmick!
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Old 08-07-2011, 12:57 PM
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a lot of guys around here that need premium fuel just trailer their boat to the nearest gas station...i know its a pita,but still the easiest solution
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Old 08-07-2011, 01:42 PM
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Keep it on the trailer and fill it up at the gas station. I have a B&M 250 dual carb set up I'll let go cheap. PM me
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Old 08-07-2011, 05:17 PM
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Quote:
Originally Posted by 95SCARAB29 View Post
What type of charger set up are you using? Does that octane boost really work? Some say it is a gimmick!
B&M Superchargers on my 502 MPIs (fuel injected). The Valvtech stuff is suppsoed to be legit. I use this stuff in my Harley (10.5-1 compression)-
http://www.manhattanoil.com/octane-boosters.php

The 2-1 racing formula.

Last edited by rgrgoog; 08-07-2011 at 05:20 PM.
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Old 08-08-2011, 02:12 AM
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Any supercharged engine is going to need more than 87 octane fuel. Might be able to get by with 89 on a very low boost engine that is tuned rich.
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Old 08-08-2011, 09:50 AM
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502mpi running M1 Procharger @ 7psi i only run 93 if they dont have it I put on the trailer till I find it. Its not worth the risk at all IMO. Oh and my 502 is all stock except for the entire fuel system and ecm update and the procharger. Runs like a beast and knock on wood been on the lake all summer long and no problems .

Last edited by swan2; 08-08-2011 at 09:54 AM.
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Old 08-08-2011, 11:11 AM
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Smile forced induction

I wouldnt reccomend running any boost into that engine with lower octane fuel unless an aftermarket engine management system is installed. The factory system installed on your MPI only utilizes a 1 bar map sensor and cannot sense a load under boost, therefore you have to use piggyback boxes for the ignition and fuel to "cheat" the engine into believing its still operating under a vacuum. Those systems in my experience are extremely unreliable and prone to tuning mistakes and problems, in fact most tuners will steer away from playing with them. Your best bet would be to sell your complete MPI and build a new engine with low compression, aftermarket EFI/DFI and a whipple setup. OR go carbed with 7.5:1 compression and low boost... Or just pull it out of the water and put 93 in it like we all do!
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Old 08-08-2011, 12:47 PM
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I wouldnt reccomend running any boost into that engine with lower octane fuel unless an aftermarket engine management system is installed. The factory system installed on your MPI only utilizes a 1 bar map sensor and cannot sense a load under boost, therefore you have to use piggyback boxes for the ignition and fuel to "cheat" the engine into believing its still operating under a vacuum. Those systems in my experience are extremely unreliable and prone to tuning mistakes and problems, in fact most tuners will steer away from playing with them. Your best bet would be to sell your complete MPI and build a new engine with low compression, aftermarket EFI/DFI and a whipple setup. OR go carbed with 7.5:1 compression and low boost... Or just pull it out of the water and put 93 in it like we all do!
I have MSD boxes on mine as well as some other electronic items to do exactly what you are talking about.
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