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We had another visitor yesterday, @lrobbi came to visit and get his DDMworks Rotrex Supercharger kit installed. I have to say for those that have not met lrobbi yet, he is one of the niced guys you will ever meet and we were very happy to have him here with @Ayla, the fact that he brought a dozen and half of doughnuts didn't hurt ;)

This was a neat install for us since we have been getting questions about the Alpha adjustable exhaust and how it would work with a supercharger. @lrobbi has the Alpha and so we said we would give it a shot and see how it goes, and this is how it went -

He had a pretty clean setup when it came in, in this picture we had already removed the filter that he had, but here is what we started with -





We then removed the intake tube and went to work. We actually were going to try to see how fast we could put a supercharger on, but when @lrobbi arrived he had some other pieces that he wanted us to put on, a Rist Rocket Racing brace and also finish up putting on some coolant hoses from Cycle Springs, so we took our time and did a couple extras for him.











With the front end removed, it gives much better access for the intercooler install, we had to take a little more off though to install the RRR brace -







The good thing about having the radiator removed and front clip for the RRR brace and coolant hose install, it gave very easy access for the supercharger belt install -







With the RRR brace and coolant hoses installed we started to bolt everything back together -







Then our intercooler and shrouding went back on -







Since @lrobbi is using the RRR brace instead of the stock piece, we have to make a couple quick modifications to mount the oil filter and reservoir for the Rotrex -







Next, the charge tubes start to go on, also @[email protected] made a nice little bracket to hold his HID ballasts and mount the horn -







Then lastly the front end bolts back up -







Then the fun part, time to go put it on the dyno -







Pretty good numbers from the install. A couple notes on the power output, with the Alpha exhaust wide open it made 284hp and with it closed it made 250hp. We were happy to be the first one to test this type of setup on the supercharger setup and it did what we thought it would do. This Slingshot was equipped with a wideband oxygen sensor and along with the software from @MEFIburn I was able to monitor the engine on the dyno. With the exhaust open we were seeing pretty normal boost pressures around mid 8's and a pretty conservative air/fuel ratio in the high 11's, everything looked good. When we closed the exhaust, boost rose to around 10psi and the air/fuel ratio dropped to almost 10.



Here is why, for those that are not familiar with how the Slingshot is tuned. The Slingshot uses what is called speed density for tuning. That means that it does not actually measure how much air is coming into the engine, but instead calculates the amount of air based on several things - Engine RPM, intake air temperature, intake manifold pressure, throttle position, etc. So, when the exhaust was closed on the Alpha muffler, that causes exhaust gas to back up into the cylinder head and raise the pressure in the intake manifold and also at the same time decreases the flow of air through the engine. The ECM sees only the increase in pressure and can not tell that the increase was caused by exhaust backpressure and therefore thinks that with the higher pressure, everything else being equal, more air must be coming in. If the ECM thinks that more air is coming in, it injects more fuel and the air fuel ratio drops.



That is all pretty much what we thought would happen, but it is always good to test it and see it happen. In the end, @lrobbi has a really nice cruiser that has a nice punch to it and even more with the push of the button on the remote. The install came out great and we really appreciate him coming to us for the install and the very special gift :)



Let me know if you have any other questions about the supercharger or the exhaust configuration.

Dave
 

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Very nice and informative write up, as always!

Good looking machine!
 
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Discussion Starter #4
Would your supercharger work with the Alpha header and side exhaust? Do you have a package deal for your supercharger and fuel rail?
Hello,

We do know that the Alpha header does not work with the supercharger kit, but the side exhaust should be just fine. No package deal on the supercharger with the fuel rail right now, but that is a good idea and it has been pretty common for people to order both at the same time. I will see what we can do and post that up on our website.

Thanks for the suggestion!
Dave
 

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Hello,

We do know that the Alpha header does not work with the supercharger kit, but the side exhaust should be just fine. No package deal on the supercharger with the fuel rail right now, but that is a good idea and it has been pretty common for people to order both at the same time. I will see what we can do and post that up on our website.

Thanks for the suggestion!
Dave
why doesnt it work with alpha header?
 

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