I have a 1 Liter (62 cubic inch) twin screw supercharger. The plan was to put it on this summer, but I'm not sure I could reach my power goal of 300whp+ with it, so I began to consider a turbo setup instead. Problem is the SC only turned 9 or 10K snout speed stock, and I'm not sure I could spin it the needed 15-17K to reach my power goal and still be reliable, plus those speeds put it outside of it's efficiency range.

I bought another millenia SC a couple weeks ago. I'm considering installing both SC's, one hotside, one coldside, running in parallel. I would have to fab up a custom intake manifold to gain the needed clearance for the coldside SC. The coldside SC brackets could be integrated into the manifold for added rigidity. The intake manifold would be a flange with four primairies going to a collector, similar to a header. The throttle body would mount to the collector. The intake would be below the coldside supercharger. When the bracket/intake was finished, it would bolt to the head and to the stock points where the old intake was braced. Then the SC would bolt onto the brackets.

The hotside would be done similarly, but would be hinged on one side, similar to an alternator. This would allow me to tension the belt, eliminating the need for a idler pulley/tensioner assembly. Since I will be running two in parallel, the snout speed of the SC's can be cut roughly in half. Both have 4" 8 rib snout pulleys stock. With both SC's in parallel, I would only need a 4-5" crank pulley to make 300whp, where as I would need a 9-10" crank pulley if I used 1 SC, and I can't find round stock that big. So this would simplify the pulley making problem as I have 6" round stock and a lathe.

The good:

• I already have both SC's.
• I have brackets made already for the hotside SC, though I may redo them.
• I have an arc welder and access to a mig and can weld fairly decent.
• I can make my own intake manifold, exhaust header, and 3" exhaust, the only cost will be materials and my time.
• Making crank pulley would be easier and cheaper.
• Two SC's in parallel would use less HP to move the same volume of air at any given pressure ratio above 250CFM.

• Reducing snout speed will ensure the SC's will essentially last forever, as heat and case flex are the main killers, and both are caused by high RPMs. (heat increases linearly to about 9K snout speed, then increases exponentially. Case flex increases exponentially as well)
• Would be capable of moving up to 900 CFM efficiently.

The bad:

• Increased initial cost
• Increased complexity of adding another SC
• Will have to tap oil pan for two oil drains instead of just 1.(unless I can find away around this)
• Will need two oil feed lines.
• Will have to make new intake manifold
• reduced belt wrap, though that should not be a problem as the SC's won't use as much HP.
• Less initial boost at lower RPMs (below 3-4K) as the SC's efficiency is low at slow snout speeds. Probably only half of full boost available at 2K RPMs, reaching full boost by 3-4K.

Interested to hear everyone's opinions and suggestions to improve the setup.

 

if you must stay supercharged i'd say just sell off both superchargers and get a bigger one like an m90, could always do centrifugal supercharger since there's units that will easily meet your goals. other than that a turbo sounds like a really good idea, maybe even twin charged would be a slick route

 

Well, an M90 is a roots blower, not a twin screw. I would much rather have the twin screw from an efficiency standpoint. They have will make higher boost, heat the charge less, and use less power doing it. They also make boost sooner. A twin screw SC is better in every way except for initial cost. Plus I already have these units and am familiar with them. I don't want a centrifugal either, that's all the downsides of a turbo, combined with the bad things from a positive displacement SC. I'd rather turbo it then do that.

I don't want to twincharge it either. That would be expensive and complex. The dual SC's would be too, but not as bad. Again, I also have 2 SC's but I don't have a turbo and don't know much about turbos.

Perhaps a 1.6L or so twinscrew would be better, but I don't have one and they are expensive.

 

very interesting.... please be one of the first to do the setup

 

can't wait to see/hear to video... the whine is going to be crazy.

 

Yea two twin screw superchargers running unthrottled is gonna be pretty loud. I'm gonna do it. I think it will be a very efficient SC setup and very capable. I need to do some math to calculate SC speeds, but I'll be running them either 1:1 with the engine speed or maybe a little faster. The good thing about it is it will be 500whp capable.

 

just dont twincharge it.

TRIPLEcharge it.

 

I did some math from Corky's book Supercharged and I think I want about 460CFM going in the motor, so 230CFM from each SC. Looking at the compressor map, I'll need the blowers turning.....8K to do that, so a 4.4" crank pulley from SOT would put the SC at 7700 at 7K engine speed, so that will do fine. I know it's a 6 rib pulley, but I think I could just run the 6 rib belt and it would probably be fine. If it slips, I'll make a 8 rib pulley. It's only 75+ shipping for the 4.4" pulley, but the next size up is 120. Ha, with a 6" crank pulley (the stock size crank pulley the millenia had), I would be pumping out over 600CFM with both SC's......

 

Looking forward to seeing some good results. Good Luck

 

Actually, a twin-charge set-up could be done rather easily. Have the s/c mounted hotside like you're already doing, then do a rear-mount turbo. The r/m turbo can be utilized here because there is no worry about lag. Heat wrapping the exhaust will also help keep exhaust gases nice and hot for the turbo. Not to mention there is sufficient room where the muffler is. Hard part would be running a charge pipe to the s/c. Though I don't know what would be better, for the s/c to breathe into the turbo or suck through the turbo. (i.e. filter coming off the s/c and the s/c outlet going to the turbo or having the filter on the turbo and then the charge pipe off the turbo going to the inlet of the s/c). Not to mention the better weight distribution. Getting oil back to the oil pan would be rather easy as scavenger pumps are easy to get a hold of.

I think this would make for some interesting numbers. I brought this idea up on m.net awhile ago and didn't get much response. I also do not think it's been done yet with a Miata....you should be the first!

 

I like the OP's idea and you should do it.

 

Don't you have to rebuild one of those blowers though? I like dopplegayer's sc + rm turbo concept.

 

One of them does need a rebuild. I may rebuild it, or i may just get another that is in better shaper. I know where another is that may not need a rebuild.

I don't think I'm gonna do a turbo and SC setup. I have two SC's and it wouldn't cost too much money to get it going.

 

And turbo+supercharger has been done already on a Miata. Do the double supercharger. I love silly **** like that.

 

Could you have one of the superchargers blowing into the hotside of a turbocharger that blows into the motor?

 

I dont know... rebuilding s/c + fabing' a custom intake + pulley system + al lthat weight on the front and it sounds like a lot of stress for the front bearings/crank/pulley area.

I'd love to see 2 s/c's under the hood though.

I still also want to see a hotside s/c + r/m turbo...an easy 300+rwhp car with the best of both worlds.

 

Well the new intake will probably be lighter than the old one, but 2 SC's and all the brackets it will definately be heavy. The new header will be lighter than the stock cast manifold. I don't think I have to worry about the crankshaft, I won't have to run a lot of tension, only about 1/2 or what all the other SC owners run. Plus if I make my own crank pulley it will be 8 rib, so that will reduce the pull on the crank as well.

 

I need some advice on the intake manifold and charge pipe design. The SC's have a 2.5" outlet on top. I'm not sure but I was figuring on having the two pipes join and go into an intercooler, then out and to the intake. Problem is the pipes for the oultets are 2.5" To join them both into one large pipe I would need a 3.5" pipe to keep the area about the same.

Pipe Size /Area
2.5 /4.9
3 /7.1
3.5 /9.6

So what should I do here, use 3.5" charge pipes? I could say let them combine into a 3.5", then taper it down to 3" and buy an IC with 3" inlets and outlets. I doubt Ebay has IC's with 3.5" Outlets.

Also since I'm building a custom intake manifold anyway, I could make the collector for the intake say 3" or 3.5, but would need a really big TB, and that would make it touchy.

Ideas are welcome.

 

interesting idea...if you already have them...why not?

 

I think you'll be fine keeping 2.5" charge pipe...two 2.5's into a single 2.5' "Y". If you are doing the charge pipes in stainless you can get a very beautiful "Y" from Burns Stainless. Routing 2.5" would be much easier than 3" or 3.5", if you can even find 3.5" piping.



You can get them any way you want, Burns is very flexible. Well worth the price to not have to do it yourself.

If you want to do the charge pipes in aluminum then I'd still do it the same way, with a 2.5" "Y", but do it myself cause cutting and fitting aluminum is much easier and quicker than stainless.

I'd keep your intake plentium at 2.5" and try to use your stock TB. I'm not a big TB guy at the moment, especially if the TB is after the superchargers.