I ran this setup for three seasons and it became ever more apparent the shortcomings of the blower /carburetor setup.
1) Noisy, both exhaust and blower belt noise. Sounds cool at first but after several hours of use every weekend through the summer the noise gets bothersome. Also the noise laws keep getting tougher and noise reduction is inevitable.
2) Power consumption, at high boost a blower is taking away 150+ hp just to run it.
3) Lack of ability to make high boost, I ran more and more overdrive to try to get to 20lbs boost at 6500 rpm and I found that I couldn't get above 14 lbs no matter how much OD I ran. The roots blower is not really a compressor anyway and never was designed to make pressure. The only way anyone gets high boost out of a roots blower is with multiple teflon or nylon strips on the rotors and that leads to ever more heat generation, crankshaft horsepower reductions, and maintenance concerns.
4) Maintenance concerns, This was the straw that broke the camels back for me. After three seasons use it was apparent that the blower needed re-stripping. This turned out to be a costly thing. Sent the blower back to Hampton in Ca. had it disassembled, inspected and re-stripped. Turns out a 1" long section of the strip broke off and went through the engine. Probably wasn't the best for lubrication. As I recall back when I had a bad Holley fuel pump the engine gave a couple small pops and that's what caused the piece to break off. The bill was over $ 500.
5) Carburetor tuning inconsistencies, I had ongoing battles with the needle and seats. The boat would bounce over some waves and some fuel would slosh around and the engine tuning would change. Well, when you consider that carbs have been around for 100+ years then you know you're not talking state of the art here.
So I said to the blower " YOU"RE OUTTA HERE" I sold it to a guy who put it on a street car and only wanted to make 10 # boost. He loves it.
NEW PLAN
I had worked with turbo's on sand drag buggies and I knew the extreme high boost that was available. More than the engine can take.
Comparing a turbo to a blower you realize the simplicity of a turbo and the complexity of a blower. Semi diesels run for hundreds of thousands of miles with turbo's and run 20 # or more boost also. Turbos are very durable. A friend who used to work at a truck stop told me that trucks would stop in right off the expressway to fuel up and the turbine housings would be glowing dull red.
The previous setups I had ran used a carburetor and a draw through setup. There were the same tuning problems with the carburetor. You could make it run great at wide open throttle but the driveability was rough.
The new plan was to use the turbo's to get plenty of efficient boost and an Electronic fuel injection setup for precision of tuning. Since I knew nothing about EFI there was certainly going to be a learning curve. This new setup would be a blow through setup so no vaccuum seals would be needed on the compressors. That means quicker spool up time.
I also was convinced to use an intercooler and had no experience there either.
WELL, I LIKE A CHALLENGE
I started in November 2002 by first blocking the two turbo's up at the position I wanted keeping in mind that access to the distributor and the valve covers were some primary concerns as well as having the exhaust clear the sides of the boat.
I turned a 4 x 4 wood block round on each end on a lathe and inserted it into the compressor intake and then bolted the block to the ski tow bar.
Next I made flanges for both the turbine housing and cylinder head, mounted them in place and tacked a piece of flatstock between the flanges to hold the alignment. Next time I have to do this I would buy flanges already made. I found a source in Ohio that makes them out of stainless. See htttp://www.stainlessworks.com.
I made a jig to hold the flanges in place then cut and fitted the 2" stainless tubing bends to each port. If you don't use a jig the flanges will be warped bad after all the fitting up and welding. I had a hole through the jig on each port so that I could weld the pipes to the inside of the flanges.
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