Y2KTIBLTD

I've been thinking about going with F/I a lot lately and I've been pondering the benefits/drawbacks of going with S/C instead of Turbo. I like the idea that most of my power comes in early in the RPM range and the fact that that power is much more linear. I was wondering (Red, Random, ???) what would someone need to piece together a home built s/c kit? I have already gathered a list of pieces I think I would need from my limited experience with engines and possibly where I could get them. The only problem I keep seeing is my IM. I could try and build a custom IM but that would probably be disastrous. I could also buy a used IM from a junked Tib and try to fabricate a plate that would allow me to bolt up a S/C of my choice but I'm not sure how easy it is to weld aluminum. I was just wondering what someone else's take on this might be. I want to put together a low end system at first and then gradually upgrade and add parts. Just a thought. rolleyes.gif

[ March 19, 2002, 01:45 PM: Message edited by: Y2KTIBLTD ]

AzzY

well out of all your questions theres only one i can answer. ... wait, it wasnt a question tongue.gif

welding aluminum isnt *hard* but its difficult to get the hang of. first off youll need to find yourself a TIG welder, id recomend you get some extra tips, as youll probibly ruin a few in your learning process. next go and rob a recycling center of a bunch of aluminum cans, now practice welding the cans together. place one on top of the other, and weld around it. its alot like MIG welding; if youve never welded before id suggest getting the hang of a migwelder then move onto TIG. good luck man!

Y2KTIBLTD

My father is an excellent welder. He has been welding for about 30 years. It's what he does for a living. Even if it couldn't be fabricated by one of us. I know Chuck from RC performance has many contacts around here who could build a custom IM for me. I was more curious as to what everyone thought I would need in the way of parts to get this going. Also is there a way to regulate the boost amount from a S/C (Besides Pulley Size, I'm thinking kind of like a blow-off valve) so I could start off running just a S/C with an S-AFC? Then work my way up with bigger injectors, new pistons, rods, Haltech, etc, etc.

Cheuk in Seoul

With premium fuel, I think that a RRFPR should do the job if you are running around 5 psi.

I don't know if the S AFC alone will do it.
Maybe larger injectors and a S AFC.

Make sure you measure everything before you start cutting and welding. The supercharger is a tight fit.

Y2KTIBLTD

The only reason I considered just an S-AFC is because the rumor around here is that Tiburon's are "factory rich" and that you can take the stock injectors to somewhere around 200 BHP before they crap out. I was planning on going much, much lower than that HP figure for my first stage. I'm also wondering if there is any way to incorporate some type of BOV into the supercharger to keep boost levels down until I need it. I don't like the idea of having to change pulleys whenever I want to crank up the boost. Wouldn't it be the same principle/idea as people running turbo's of just routing the BOV back into the intake downstream of the MAF sensor?

Random

Some superchargers do indeed have an internal bypass that is semi-adjustable, that would allow you to "adjust" the level of boost.

A centrifical supercharger would allow you to use a blow off valve, as it is basically the compressor side of a turbo that is belt driven.

Rather than try to fabricate everything yourself and 'reinvent the wheel' there are 2 companies that sell superchargers with intake manifolds that fit the beta motor. Alpine and C.A.P.A. I would reccomend C.A.P.A., as the exchange rate between the USA and Oz is in our favor. (www.capa.com.au)

The stock injectors are good to about 180 HP at stock fuel pressure. If you upped the fuel pressure, 200 should be doable, but that is also the limit of the stock fuel pump, so you would want to upgrade that as well.

The S-AFC can me made to work, but it is less than idea in a n/a motor that is now F/I.

One of the reasons the motors run "factory rich" is detonation. The over rich mixture keeps detonation down. A "pure power" mixture is actually richer than the perfect 14.7:1 rato. A forced induction mixture for "pure power" is usually even more rich, to prevent detonation, as the extra gas cools the intake air charge, and absorbs heat in the combustion chamber. However, there is a point in which adding more fuel and making it "over rich" will not prevent detonation any longer, and will actuallly start to promote detonation. However, in stock trim, our motors are not THAT rich.

Y2KTIBLTD

1.) Why does it have to be a centrifugal supercharger in order to have a blow-off valve?

2.) If I had $3500 to spend on F/I I would. But I would rather create my own. That would allow me to piece together parts as I get money and also build to suit. The luck around here with Alpine has been horrible and isn't CAPA based in OZ hence meaning their cars are MAP based. I thought that would be more trouble than it's worth.

3.) Why wouldn't the S-AFC work fine. S/C more resembles a N/A motor than a turbo would. Basically as RPM's raise so would your boost. Couldn't you simply add to the factory fuel curve and make some simple tweaks with an S-AFC?

I'm not trying to make any body mad here but I am a very sceptical person. I like to think things through myself and see how it could be made to work rather than rely on what someone else claims is the truth. I just was curious as to everyone's opinions on whether something could work or not. And how it could/not work.

Cheuk in Seoul

A BLOW OFF valve can't really exist in a supercharger because it is used to control exhaust gas routing. A BYPASS valve... bypasses the intake air around the supercharger and directly into the intake is possible and a POP OFF valve which releases pressure above a set level is also doable.

The S/C is very much like a NA motor but in a roots type blower boost is not linear with the rpms... usually max boost is quickly reached and stays there. It will act like a larger NA engine in terms of response. You will probably max out the S-AFC and the injectors with stock fuel pressures. I still suggest a RRFPR. If the rest of the fuel system is up to specs... good fuel pump, then it is the most practical way to go. Look at all the roots supercharger systems for different cars... most use a RRFPR.

Once again I am not a fan of roots superchargers in the Tibby's... for multiple reasons. I would not go this route. It's better to squeeze nitrous or just go with a turbo.

Random

Y2KTIBLTD

The reason you cannot really build a supercharger yourself, is the single most expensive part is the supercharger itself.

You can buy the "parts" piecemeal from Alpine or CAPA, however, it is more expensive than buying the "kit" as a whole.

Centrifical superchargers act like a turbo, so they are the only kind that can have a BOV. As cheuk stated, Roots type superchargers need a bypass or a Pop-off valve.

You could try to buy a magnuson/eaton supercharger, then buy an extra intake manifold, then spend your time welding and cutting..etc..etc.. Then fabricating custom mounts....then fabricating a pulley assembly. How much is your time worth? You are easily looking at 80 to 100 hours of fabrication work, not to mention the cost of using the tools, unless you already have them.

An S-AFC is designed to work on N/A or factory turbo/supercharged motors. It is MEANT to be used to "fine tune" the fuel given to the engine by altering the air signal. In a N/A motor that has been changed to Forced Induction, the air flow has been significanly changed over stock, as have the fuel requirements. You now need to basically, create your own fuel curve for the motor. Quite frankly...the S-AFC is not up to the task. It will do it, but the SAFC lacks the granularity and depth that a full fuel map would have. So you are stuck tuning in 500 RPM increments for part and full throttle, and that's it. No provision in tuning for boost pressure.

Sorry, when I mentioned upping the fuel pressure, I assumed a Rising Rate Fuel Pressure Regulator (RRFPR), but did not mention it by name.

Again, it is doable, but it really depends on your level of skill...and the amount of time you are willing to devote to it.

Lastly...corkey bell has his supercharger book out now. (partner to "maximum boost" for turbos). You might want to pick it up and read it cover to cover, and then you will know just what you are getting yourself into.

Y2KTIBLTD

Thanks a lot Random and Cheuk. That makes more sense now. I'll have to check out that book. Cheuk you had mentioned a roots-type blower as coming up to full boost early and then maintaining that boost amount throughout the RPM range. I was actually looking into a whipple charger (or something similar). They are not centrifugal and are supposedly good to 14,000 RPM. Would they also top out early and then continue to make the same boost as RPM's rise?
Check out their website they have a kit for the PT cruiser. Whipple Chargers smile.gif