Reason I am opting for the eaton is that you can get one on ebay for 200 or less. I'm not looking for extreme boost and whatnot. I realize that the centrifugal is a lot easier of a set up, but I can't find a get-up that I would consider a "budget deal". basically I'm looking to add the pep for under 1k, otherwise I'd just go with the t2 swap.

 

If you can do it for under $1000 then thats awesome! Otherwise definetly go turbo.

 

This is a common misconception. Boost is not free. Turbochargers require energy to spin the compressor just like superchargers do. Turbos just happen to take it from exhaust gasses. The result is restriction and turbulance in the exhaust stream.

 

why is it that whenever everyone debates this issue, that no one seems to figure out just what the desired result is first? IMHO, if you don't care about top end, and just wanna smoke at the stoplight, then the Eaton is not a bad way to go--it gives full boost quickly and that is when you would want it, right? It all depends on what you want the car to do, just like any other mods, but that gets lost. How many of you guys with turbos or s/c's run flat out all the time? Many of you don't ever max it out anyway, so why push the issue about which is the fastest, or which gives more power, or whatever? Fact is there are lots of people who have run high boost in both sc and turbos, so we all know they both can get there.

Figure out what you are looking for BEFORE you decide what to drop the $$$ on! I have lots of experience driving the T-Bird SC compared to the T-bird V6 non-s/c, and I can tell you that the SC just flies like hell compared to the NA version. And it is the same block too. Who cares if it won't break 150? Or if the boost comes on lower in rpms? Hell, that car redlined at 5500 anyway. and I never needed to go that fast to prove my point--that car would smoke stock Mustang GTs off the line every time. BTW it was all stock too. Try telling the mustang owner that you just ran that he got whipped by a V6 and see the look on his face! And since the Eaton M90 can spin to over 13K rpm safely, it is not as much a matter of overspeeding--you just have to do your homework with the pulley size.

I am going with the sc too. Mainly because I want more power but I dont want the same turbo car that everyone else has. oh, and for the ones that keep saying "dude just go buy a TII", get a clue already. We all know that the TII is faster. Most of us NA guys would have gotten the TII if we could have found a good one that wasnt beat to hell or overpriced. If there are so many out there just waiting for us to convert to the turbo side, then go show me where they are. I have not seen a single one on the road where I live, and only saw ONE where I used to live in Kansas. I was there for over four years and only saw ONE. It was beat to **** too....

 

Here ya go--"Just go buy a TII"....

eBay has two whole pages of RX7's right now. There were like FOUR TIIs listed. One of them had 110K with a blown motor and no brakes, along with some body work needed. so far the bidding is up to $1000 and it is not at reserve yet. Another one is an 87 with 45K on it. It is bone stock--even has the original radio still--and they want $7500 for it!! for an 87!! I love FCs man, but before I lay down 7500 for a stock TII I will put that cash right into my 86 GXL, and mine will end up being a much better car! For that kinda cash mine will be faster, handle tighter, and look better too.

I am glad for you that you got your TII. But if they were really out there like that we all would already have them...sorry for the rant but every time this comes up there is always some tool who jumps up and says "dude just get a TII" when what is really asked for is a real answer....

 

It's always good to look at what your goals are.

If you are going to stay below 10-15 psi you can probably get both a roots supercharger or a turbo to work well. The turbo can be designed to have reasonably small lag with a fat torque band that doesn't lose too much at the top end. The roots supercharger would be within it's zone of acceptable efficiency especially if you can manage a good intercooler. I keep dreaming about a fuel injected, intercooled, roots supercharged Rx7, I think it will surprise a lot of people.

Above 15 psi you'll have a hard time getting the roots supercharger to work because of heat, belt slip and internal leakage. The turbo will begin to be harder and harder to design without significant lag but it will be possible to get the boost. You kinda have to go with the turbo.

As you pass 20 psi you'll have a harder and harder time getting anything useful out of anything except bragging rights because the power band will either be so narrow or so sudden that it will be nearly unusable except for dramatic burnouts. (except possibly a two stage roots SC - that would be interesting)

I haven't even mentioned centrifugal superchargers because I have never seen even one setup that worked anywhere except the last 1000 rpm unless the boost was below 5psi. Very impressive numbers though.

ed

 

The end result was already stated by the author of this thread, and it was simply a quest for "more power". There was no mention of "bling" factor, high end vs low end, or anything else.

... get cheap, skinny rear tires for $40 each, and then you don't need a supercharger or a turbo to smoke at a stoplight. In fact, my 1Gen smokes at stoplights because the seals are bad.

Did you totally miss my list of superchargers?

How can you complain that " no one seems to figure out just what the desired result is first?", and then write "why push the issue about which is the fastest, or which gives more power, or whatever"? So which is it, do supercharger characteristics matter or not? Did you forget to take your lithium today?

I have a clue already, and that clue is that a TII is the cheapest way for most people to enter the forced induction realm. I think it is irresponsible to not mention the TII option when somebody is looking at spending $3,000-4,000 on a supercharger setup that will have the same or less power than a TII. Once the options are layed out via a group discussion on this forum, then each individual can choose whatever they like for their car.

That is just how they are.

 

I am NOT looking for any "BLING BLING"! I just want to put some throttle in that waddle on my FC! Honestly, keeping it stock is sounding pretty good. Don't get me wrong I definately want a turbo, but those are a rare item in my area and I don't have the money to have one shipped or to travel to get one.

Maybe I'll put my 13b in my 73 VW Bug that I'm working on.........YEAH RIGHT, but it would be quite a sight!

Oh, and by the way thanks for all of the feedback....these forums really help w/ the decision making on the RX!

THANX TO ALL!

 

Yeah, if you don't have $80 for a bus ticket, you certainly don't want to get a loan for several thousand dollars for a supercharger kit. The stock FC NA is pretty nice, and it probably won't kill you to keep it stock. I sold my TII because I didn't like it as much as my other cars, even though it had more hp.

That is more common than you may think.
http://www.geocities.com/zenjoe/conversion.html
http://www.geocities.com/MotorCity/1309/vw.html
http://www.mrec.homestead.com/files/...es/rotabug.htm
http://frost.bbboy.net/vwengineconversions

This shop is local to me and has lots of goodies:
http://www.fisherbuggies.com/

 

A bug with a 13 b in it.

That be like putting a rocket in a beer can.....

Personally though, I'd put it in a rusted 81 toyota corrola. The sleeper effect would just be hilarious.

 

DUDE THOSE LINKS ARE AWESOME! I NEVER would have thought about actually doing that seriously!

I could put my rotary into the V-Dub and a TII engine into the Mazda.....If I only had the $$$$$!!!

They fit pretty freakin good into the bugs too!

Thanks again for the links...VERY interesting!

 

Here is how I see it on this topic SC vs turbo chargers in the end BOOST is BOOST and its all in how you want to get it [boost].
Dan

 

you get what you pay for too. some people can do the SC for less than a turbo swap, so let em go for it. Dont get me wrong. I am all for picking up a T2, but when I like most people have their upgrades revolve around money and available resources.....you gotta go with what gives you the best bang for the buck.

 

Not all boost is created equal.

1) Pressure Ratio is not as important as Density Ratio. In other words, the amount of boost doesn't mean much if a lot of heat is also produced. For example, an efficient 12psi boost will produce more hp than an inefficient 15psi boost.

2) Each type of supercharger has a different boost profile. (Turbos are also a type of supercharger). See this diagram of different superchargers all producing the "same" 7psi boost. Looking at the centrifugal supercharger boost profile, do you still think that "boost is boost"?

 

Hey,

where's the graph for the Leafhog? That's got to be up there in 7 psi or so.

 

 

With modern turbo technology, turbochargers make great low end power, and lag is non-existant.  I have not seen the superior low-end of a supercharger (versus turbo) on dyno sheets in reference to FC installs.

Turbos are just cheaper to build and install at this point.  Used turbos abound, and a stock FC Turbo II exhaust manifold and turbo is a very easy starting point for FC NA owners.

Superchargers, in comparison, are VERY expensive to purchase and install.  Don't be fooled with that Atkins(?) SC kit for like $3k(?) - it requires you to change over to carburation which is a lot of work and effort for the power gains.

"Buy a Turbo II" is a way more viable option.

Be patient, and don't expect the car to drop into your laps.
There are several online car for-sale websites available, and you're bound to run into one soon.

I have a list of them on my website in the How To Buy page.


-Ted

 

Your graph of the centrifugal is not entirely correct. The Paxton, when installed with the Nelson kit, drops off drastically at about 6000rpms where the friction planetary drive bearings start to slip and fail due to overspeeding. I personally have known of three cars with the Nelson kit (one was my car) - all three blowers had failed at least once by 8000 miles....

 

So are we now defining an entire genre based solely on the failings of one particular model?

 

Nope - just telling you what happens to the only one that was offered in kit form out there. The part about your graph not being correct was a joke - similar to the leaf hog reference!

 

though, with the amount you'd pay for a supercharger, or a turbo conversion, youre better off buying a whole nother TII.

 

as far as intercoolers are considered any one ever done a water to air intercooler, or considered doing water injection, which seems more cost effective especially if you DIY, though more annoying to have to fill up the water every time you fill up your gas tank.

 

yes, air to water can be used with great results (BDC made ~440whp running one). you only fill up water squirts "tanks" as much as you spray the water -- or until evaporation takes it toll. i wouldn't say "OR" water injection. thats like saying seatbelts Or airbag. you can use the intercooler (seatbelt) by itself, but i wouldn't run the water injection (airbag) by itself. [i wouldnt. but hey, some people also dont seem to mind risking their life by not wearing a belt; in my opinion, my life is more important than my engine. though my engine just died.. ]

 

Just out of curiosity, why do they still run roots type superchargers in top fuel rails and funny cars. Seems like a turbo charger and nitromethane would work better. Is there something agianst it in the NHRA rulebooks? just wondering.

-E

 

1) Turbos are banned.
2) (Electronic) fuel injection is banned.
3) Nitromethane is mandatory for top-tier NHRA drag racing.



-Ted