mguire

I'm thinking of adding a supercharger this summer to my NA, and a 3rd pair of injectors with a piggy back computer to supply the fuel. (and new fuel pump). I am wondering how much boost I can safely run and what issues I might run into (I'm trying to keep it emissions legal, no visual inspection). At what level of boost will I need an intercooler? I would like to avoid the expense of an FMIC for now.

Thanks,

Eric

scathcart

Depends on your supercharger. Level of boost does not necessitate the requirement of a IC/AC.
What kit (if any) were you gonna go with?
Sean

Evil Aviator

Yes, the boost level does matter, as the boost level is very closely related to the amount of heat produced by the compression process. However, there are many other factors for detonation, such as type & brand of supercharger, fuel octane rating, compression ratio, ambient conditions, etc. It is always best to just ask the supercharger manufacturer what they recommend, and use that as a starting point.

If you post what brand and model of supercharger you are considering, you may find a few people who have previous experience with the same supercharger, and they may be able to give you some tips.

mguire

Thanks guys, I talked with Pineapple racing about it a couple months ago. Rob had an idea about which supercharger to use but I forget which it was. I'll get back to you after I get my plans firmed up a bit.

One more question for now though, is the boost level adjustable on most superchargers as it can be on turbochargers? Do they make superchargers with an clutch so you can turn them on and off? I'm new to the forced induction arena.

vaughnc

The one's I've seen control boost by the size of the pully. Note MOST superchargers require a special pully to keep the unit from overrevving due to the NA/s 8K rpm redline. Make sure to ask about that.

I think it's either 6-8 or 12-14PSI with the pullies.

There might be a clutch system as well. I never figured out which type of supercharger to get, but I think a few are intercooled but most are not.

-- vaughnc

Evil Aviator

Yes, the boost level is adjustable by adjusting the speed of the supercharger through the pulley ratio. However, some superchargers are only offered with certain sets of pulleys and have a given operation range as mentioned in the previous post, so make sure that your supercharger is made for a rotary engine and is capable of the boost level that you want.

Many modern superchargers have a vacuum-controlled bypass system which recirculates the air when boost is not needed (part-throttle or off-throttle) to reduce fuel consumption.

I highly recommend Corky Bell's "Supercharged!" book. It is geared toward piston engines (like everything else), but it gives a great overview of the different types of superchargers, math on how to choose a supercharger setup, and some fantastic information on exhaust, intake, intercooling, etc., so that you can build your own complete project or at least learn what to look for in a kit. It only costs about 1% what you would spend on a supercharger kit, and it just may save you from frustration or an expensive mistake.
http://www.amazon.com/exec/obidos/AS...075067-2140004

XLR8

iTrader: (52)

I thought of doing this also but decided on a TII.

I would recommend www.atkinsrotary.com. Their supercharcher is durable and basic.

86-88 FC's have 9.5/1 compression and 89-92's have 10/1. Either way I would not recomend running more than 6 psi, unless if reliability isn't an issue. Understand, TII's have 8.5/1 and they boost 6psi reliably.

Also check out www.camdensuperchargers.com. It's the same that Atkins offers but their site has more info, check out the instulation instructions. It has a little piece about boost and high compression motors there.

Good luck

scathcart

You can run 20 psi into a psiton motor without detonation with a huge NOVI 300O. With a NOVI 1000, you detonate with that much boost.
The size and brand of the supercharger does determine the maximum amount of boost before an intercooler or aftercooler is required. What kit were you going with?
I do not know of a supercharger that has a clutch. With a centrifugal supercharger, you build boost as you build revs. Max boost usually comes just before redline. Maximum boost is determined by the pulley size, and the efficeincy of the supercharger.
Basically, you make more boost by spinning the unit faster, but there is a point at which the supercharger will make less boost as you spin it faster. Talk to you s/c dealer for this stuff.
It would be possible to go with a positive displacement superchager, but more fabrication would be required. With a positive displacement supercharger, you get full boost from usually around 2000-2500 rpm, like a turbo unit almost. Boost level does not climb as revs climb.
Let us know more of your plans before we can try and help you more.
An intercooler or aftercooler is never a bad idea though....
Sean

vaughnc

can't remember if atkins makes TII intake adapters as well, but if so that's a great opion.

Phu5ion

I heard the old Nelson/Paxton kit could run at ~7 psi without an IC. Of course the stock kit was designed without the RX-7's redline in mind and the supercharger would be over spinning before you got too 7000 RPM.

You know i emailed those guys a couple of months ago asking if they made an EFI setup and i never heard back. I imagine they probably do but all their information leads me too believe it's for carb engines. Wierd .

NZConvertible

When deciding whether to use an intercooler, it's not boost level that should be considered, it inlet air temperature (seems obvious really). Whether turbo or supercharger, there are many factors that determine this temp, but some compressors are a lot more efficient than others, meaning they air the air less for the same amount of compression. The type of supercharger (roots, centrigugal, etc) makes a difference, as some are better than others, so do some research into what type of supercharger you want before picking a supplier (who'll recommend only what they sell!).
Personally I feel any form of forced induction should have an intercooler, otherwise you're missing out on some of the potential performance you've spent all your money on.
I also think supercharging a car when there's already a turbo model available isn't the wisest way to spend money, but that's just my opinion.

mguire

I've thought about selling and buying a TII, but then I wouldn't have the fun learning experience of doing it myself. Besides, my car is in great shape and I've already done alot of suspension and exhaust work on it, it runs and handles great! I just want more power.

Thanks for the info.

scathcart

go custom baby!
I would go with an ATI procharger. They are self contained oiling systems, and require no drilling for fitment of oil feed and drain lines. Plus, all of them can be pullied up to 24 or 36 psi, depending on model. That's great for when you swap to lower compression turbo rotors.
Plus, some of the new ones are built with DUAL ball bearing units (one ball bearing inside the other) for less paarsitic losses. They have a beautiful whine to them too.
That, or I would go with a big ol' NOVI 3000. This big mother would run so happliy on your motor, it would be on a vacation at 30 psi, and hardly working at all at a measely 7-10 psi.
But, I'm all about big boost....
Your best choice may be a kit, or something smaller like a vortech s-trim, or novi 1000 or 2000 with a good aftercooler.
Sean Cathcart