Hi Ron,
Regarding your post on superchargers, I own a 91 Miata with a Sebring= supercharger (and a 95 M3 among other things...). So I have some= experience and a few comments. There's a lot of marketing hype from all= manufacturers of forced induction systems, and it's difficult to sort= through it all.

First, I disagree with your remarks on intercoolers. Lots of systems for= many different applications don't include intercoolers and they work just= fine. It's a matter of cost vs. power. Turner's 355 HP kit for the M3= ($5500) doesn't have an intercooler. The $7000 400HP kit does. The= Mosselman turbo kit he offers for the 318ti 1.9 is $4500 and is= intercooled, but uses an AFPR like the Sebring (i.e. no chip as far as I= can tell). The Miata has almost no room under the hood for an intercooler,= and unless you put it in front of the radiator, it doesn't do you any good= anyway. More on this later.

And you are misinterpreting what happens on very hot days and why detonation= can be a problem. It has nothing to do with lack of an intercoooler. = Underhood temps on supercharged Miatas run as high as 170 degrees, worse= with a non-insulated header and on hot days. Intercooler or not, you will= have problems compressing air which starts out this hot. Reformulated gas= also plays a role (see below). So the solution (for any type of forced= induction system) is to get cooler ambient air into the engine. Hell of a= lot cheaper than an intercooler, too. Additionally, the intake for the= Sebring sits right by the header, so a little ingenuity and ducting is= called for. There's almost no room under a Miata hood (did I say this= before?).

Second, the Eaton/Rootes design may have a slightly lower thermal efficiency= (82%) than other approaches, but who cares? It's not enough to= substantially impact performance or reliability of a similar boost-level= non-intercooled system, and they are relatively cheap and reliable. Either= that or I guess those 5000HP top fuel dragster dudes don't know what= they're doing. Neither does Mercedes Benz in using an Eaton/Rootes unit on= the new SLK.

Third, fuel delivery/ignition timing systems on supercharger kits are a= function of the car's existing engine management system (and cost target). = The Miata does not have a removable, re-programmable chip like a BMW's. = The only feasible solution short of replacing the entire EMS is an= adjustable fuel pressure regulator (AFPR), and it works rather well when= correctly calibrated. I check my plugs regularly and have an in-line fuel= pressure gauge. I don't believe the Mosselman kit has a chip. The ERT M3= supercharger kit does though. The detonation problems on supercharged= Miatas have nothing to do with whether it has a chip or not. It's mainly= due to too much ignition advance + reformulated gas + high underhood temps.= Many hi-perf non-supercharged cars (even with knock sensors) are having= similar problems with reformulated gas on hot days (like my JimC-chipped= M3). I use Sunoco 94 octane now exclusively in both cars and have no= problems, and I'm running 10 deg initial timing advance on the Miata (kit= recommends 6). There are boost-dependent ignition timing kits available= from MSD (retard timing as a function of sensed boost), but word is they= are a little unreliable.

Bottom line is cost: if you want to pay Turner or ERT $5000+ or so to= super/turbocharge a 318, be my guest. I am sure you will get a very good= kit and it might function perhaps $2000 better than a Sebring. You'll= still need to upgrade the exhaust, suspension, tires, brakes, etc. But= frankly, why don't you buy an M3 instead? I am very happy with the Sebring= unit on the Miata and would recommend it. But there is no hi-perf M= version of the Miata. Would I put a Sebring on a 318 or a 1.8 Z3? Hell= no, I'd buy an M3 or a 2.8 Z3 (or MZ3). Would I supercharge my M3 for $7K?= Hell no, I'd trade up to a used NSX or just buy a Kawasaki ZX-11 outright= etc. etc.

Finally, there are a lot of inexpensive tweaks/improvements one can make to= the Miata Sebring, including properly intercooling it. If you are= interested, check out

http://www.miata.net/garage/hood.html

and follow the links for really good stuff on all different types of= available Miata forced induction systems. Also, check out=20

http://www.matcoland.com/m_s_main.htm

for a cheap way to intercool a Sebring that works. It's basically a Saab= 900 intercooler slapped on with some Home Depot stuff. I am in the process= of doing this to my Miata. Total cost is around $150, including the Saab= intercooler (I bought one at a junkyard for $100). Reports are that with= no other changes, this is worth about 20-25 more peak HP, and tons of= mid-range torque. I currently have a Millen header, a high-flow cat, and= a Jackson Racing stainless exhaust on the car. In it's present state it is= probably putting out 175-180 HP at the flywheel.

Finally, the air flow meter on a 1.6L Miata only flows around 165 cfm max,= and a 6.5 lb boost supercharged 1.6L engine would like something more on= the order of 250 cfm at redline. Turns out the 86-87 RX7 AFM is a drop-in= flowing nearly that at peak. I don't know of anybody who's done this with= the Sebring, but I am going to give it a try. There are also custom= programmable fuel management systems out there with hot-wire air mass= sensors (as opposed to the flapper-door style), but they are very pricey. = I figure I can run 8 or 9 pounds of boost (using a larger crank pulley)= after I get the intercooler installed, and then I'll really need the bigger= AFM. I'll be running out of fuel though, so maybe higher-flow injectors= will be needed. Eventually I want to move to a Haltech programmable unit,= with individual throttle butterflies and an HFM, scrapping the entire stock= intake system from air filter to cylinder head.

We'll see.....

• -Al