ClubRoadster.net banner

1 - 6 of 6 Posts

100% Jakedashian
Joined
7,040 Posts
Discussion Starter #1
Hi all. I've been trying to find info about how the 6psi Jackson Racing superchargers work but since it's such an old piece of kit I'm having difficulties. I hear mentions of two throttlebodies, repositioned throttle bodies, I see some setups with tensioners and a dedicated belt and some that simply use a longer version of the regular Miata accessory belt. For a basic 6psi build, what kind of "architecture" would I need? Could I mount an S/C in a position to use a longer belt on the stock pulleys/tensioner/whatnot, then blow it through the stock TB position while sucking through the VAF, or would I at the very least need to move the TB over pre-SC? The charger I'm using is I believe an M90 from a Buick 3800 that has been "miniaturized" to a ludicrous degree with an adapter plate for use elsewhere than in the valley of a V6.

My thoughts are to fabricate a bracket to screw into the threaded holes in the side of the engine (anyone know what thread pitch/size those are?) to hold the supercharger in place with screw adjustments for tension. If needed I'll just bite the bullet and build in a "traditional" spring-loaded tensioner, but at a middling 6psi I feel that could be overkill. Then just find a four-rib (is the Miata belt four rib? I honestly haven't looked that close) belt long enough to wrap around the Miata accessories, the supercharger, and any necessary idler pulley, then just plumb the outlet over to the throttle body and the inlet to the VAF.

What I don't understand is why people run multiple TBs with a supercharger yet the same sort of thing isn't necessary for a turbo. Is it due to the way the supercharger acts at idle? Would fiddling with the bypass valve eliminate the need for such a thing?

Thanks
 

The colder Adam
Joined
2,194 Posts
I'll preface by saying that I love my M45 set up and am a big fan of superchargers. However, fabricating a set up from scratch sounds like something that falls somewhere between wildly complicated/expensive and totally impossible for most people. I am not of the "just go turbo" mindset, but in this respect, I'd say a DIYer would be better off doing that or just buying a complete supercharger kit. There are lots of little things that would be a total nightmare to start of out from scratch on.

The reason for two throttle bodies is partially related to where the TB is positioned on the kits, which is pre-blower. It'a drivabliity mod, not a power adder or anything. The need for the second TB comes mostly from people who use garbage engine management solutions like power cards, timing retard boxes, etc... (AKA, the management solutions that come with the kits). Using a proper tuning solution like Megasquirt, you really don't need it. My car on MS2 runs great and I've never bothered to go down that path. However, you would probably need one unless you could source a dummy throttle body from a kit. That is not something you could really fab up unless you are really ambitious.

You will need something to keep the belt in tension. They need a decent amount to not get tossed off.
 

Registered
Joined
5,016 Posts
There are a hand full of people that have done custom supercharger setups but, no disrespect intended, they don't have to ask such basic questions usually. Of course this doesn't mean your fabrication skills aren't up to the task, which obviously i have no idea about, but i would definitely read up if you are serious about this path.

Here are two EXCELLENT builds(i can think of off hand) as examples:
Pat aka patsmx5 twin screw whipple build
http://forum.miata.net/vb/showthread.php?t=570530
Highlights: lots of great fabrication, LOTS of information sharing, 30psi making 350whp/300wtq

Richard aka RJW's(currently owned by Wolfmtnbkr) Biggulp coldside m90 supercharged(originally a m45, then mp62 now m90) with nitrous:
http://forum.miata.net/vb/showthread.php?t=362487&highlight=Big+gulp
Highlights: lots of great fabrication, lots of trial and error, several iterations to date, coldside m90 running 17psi with meth and nitrous
 

Registered
Joined
189 Posts
Your willingness to jump into a project like this is admirable but to be honest behind your first set of what could be described as general questions there are many, many, many more layers of detailed questions or at least decisions you鈥檒l have to make. I suggest doing some research first so you鈥檝e moved through several layers of questions then your questions here might be a bit more succinct and easier to answer. I would recommend that you read the Corky Bell book 鈥淪upercharged! Design, Testing and Installation of Supercharger Systems鈥. It鈥檚 on Amazon, $37.53 is not cheap but is a drop in the bucket of what you鈥檒l end up spending on a good functioning supercharger (SC) system, a drop in the ocean of what it may cost you if you build a bad system. Then look at the threads GreaseMonkey linked. I鈥檇 almost say reading the book first is a prerequisite to reading the links so that some of the more complex issues discussed are a bit more familiar to you.

A few comments about your post.
An M90 SC is huge for a Miata, not practical for a 6 psi system. An M45 will reliably give you your 6 psi, an MP62 can also and is cruising, but an M90 is way oversized and will not be running efficiently. The good news is I thought that the SCs used on Buick 3800 were MP62s so that鈥檚 what you might have, anyone care to chime in on that? Or take a photo of the SC you have with a rule in shot and post it.

Throttle body (TB) position. Different answer depending on what type of SC is being used. The M90 (and M45, MP62) are all positive displacement types. For this type your primary position for the TB needs to be upstream of the SC. If you have idle and/or throttle lag issues one solution is a second TB in the stock location.

Belt drive. Too many depends 鈥.. there are other (not related to the SC) limitations that may drive you into one particular configuration or another. For example are you contemplating a cold side installation or hot side (I think hot side?) Does the car have PS? AC? Both? Etc, etc, etc .......

You鈥檝e asked more questions but it would be an lengthy iterative process to answer them. I recommend doing some more research 鈥︹ when you鈥檝e done that I鈥檇 be willing to exchange phone numbers with you (by PM) and talk you through what I can.
 

100% Jakedashian
Joined
7,040 Posts
Discussion Starter #5
Thanks a lot for the informative responses. I'll be doing some reading, but I just finished my turbo build and am probably going to set the supercharger aside for another time. Still going to find out what I can in case I decide to go down this path in the future.
 

Registered
Joined
48 Posts
Your dedication is admirable... but I'm wondering - why not simply buy a used kit?

There are several M45's or 62's for sale across the internet... why not start there, then build bigger as req'd?
 
1 - 6 of 6 Posts
Top