Well just got done installing the new secondary charger...a John Deere take off BW S3A. This turbo has a 66/94 compressor wheel, and a 91/76 turbine wheel inside a .07 A/R turbine housing. The compressor is a very potent secondary, but the turbine, though very free flowing, is a little large for good drivability. Being a twinscroll housing, I decided to fabricate a throttle valve style butterfly in one of the volutes, and control the valve with a Big Head wastegate actuator referencing total boost. Under no or low boost, all the exhaust flow is directed into one volute (the manifold divider was removed BTW), simulating a much tighter turbine. Once total boost comes up, the actuator gradually opens the valve and allows exhaust energy to flow through both volutes. The result is no wasted exhaust energy, but a good spool-up. Look at it as a wastegate that doesn't bypass any of the exhaust energy. Anyway it works great, so I figured I'd let all you tinkerers know that it is possible.

At the same time of the secondary upgrade, I switched up my intercooler plumbing. I placed the intercooler between the two turbo compression stages to help get the inlet air cooler and denser to the secondary. I also am going to place a second cooler between the secondary compressor and the engine, though for now I have the secondary plumbed directly to the manifold, and am letting the methanol chemically aftercool the air charge under full power.

Here's a few images to look at.

Chris

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that is awesome man. That is a custom setup like I have never seen.

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It's a lot of fabwork for it to MAYBE work, but it turned out good to my pleasant surprise. Haven't had time to absolutely time and tune the secondary, but I know a little more can be had. I have to get that intake plumbed to the outside though, the Florida heat definitely makes for some high underhood temps, and you can definitely tell a difference from mid-day to evening as it cools off some. That and getting an aftercooler on the secondary.....so many projects so little time.

Chris

Well that is awesome. I wish I had the guts and know how to tackle something like that. How long did it take?

I have a local guy doing the intercooling between stages and direct from the secondary and I just don't understand how it can be more effective. Your thoughts?

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I have mapped temps at all the intake tract changes....primary, secondary, pre and post intercooler, and have found interesting results.

Everyone knows we use multi-stage compression to get manifold pressure up to squeeze more oxygen into the cylinder. But that increased pressure is only beneficial if it maintains its density. Hot air will compress just the same as cold air right? My primary outlet temps we approaching 400* full power, which makes for extremely inefficient air mass for the secondary to gobble up and second stage compress into a usable air charge. In addition, our factory IC's were not really flow designed for 70 psi and 100 to 150ft^3 of potential air flow. By putting the IC in the low pressure turbo stream, we lower the operating pressure to 35 lb or so, as well as get inlet temps to the secondary down closer to 150*, which is still hot for inlet temp standards, but a lot better then 400*. The resulting "thicker" air makes for a more efficient second stage, which both helps with the drive ratio of the secondary, as well as thermal loss to compression. Now of course the way I have it now, I'm still jacking pretty hot air into the intake manifold due to the lack of an after-cooler, but that will change before long once I get the cooler made . I am, however, running a 1600cc water system on the secondary charge when total boost is over 40 psi, presently, for "chemical" aftercooling, and it works....dropping intake temps to just over 150* full power. In a perfect set-up, however, dual charge air cooling is the most favorable....and my plans for the second stage aftercooler will be an air over water unit, as heat transfer is far superior in one of these types, than the conventional air over air type.....space savings and nightmarish air plumbing not withstanding. So in a nutshell, cooler air is better air...we all know and practice this theory, EXCEPT in compounding turbos. Have we forgotten that the secondary suffers from high inlet temps just the same as if it were a stand alone single? The moral is keep the temps as low as possible the entire path of the intake tract and the final results are more favorable. BUT, high volume plumbing systems bring their own problems such as constantly changing the velocity and direction of the air flow through multiple coolers and the myriad of piping to support them. It's the proverbial balancing act......and the quest goes on. BD actually was playing with multistage charge air cooling and even had prototypes, but for a bolt-on business, logistics did not favor the thought of the MANY applications they would have to support to do it at all...and the idea was tabled in trade for finding more efficient turbos design and combo choices. For the DIY'er though, trials pay dividends, and I urge anyone to play with the idea as they won't be dissapointed!!

how are you suporting the turbo, the pipes can't be the only suport, or are they?. i was looking to do some what of the same thing with my set up. do you have any pics of the build up? Also what type of temp gauge did you use to check the air temps? also it looks great.