Last post on Sep 21, 2001 at 8:15 AM
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Sep 18, 2001 (2:42 pm)
Mazda turbocharged the rotary very effectively with the RX-7 turbo. It was a seriously fast car, but did suffer some detonation problems.
I don't think a twin turbo setup would make much sense on a rotary, since twin turbos work best on large displacement engines that have lots of air volume being pumped by the cylinders. Twin turbos are also nice for V-engines as it makes for a nicely balanced and tidy package on a V. There is a misconception that twin turbos give you "twice the power". This is quite incorrect. You don't get any more power, as in fact, one large turbo is just as good if not better. Also, there are practical limits to turbo size.
No bolt-on turbo should be run of the mill. Aftermarket turbos need to be very expertly designed, and some of them aren't.
Sep 18, 2001 (11:09 pm)
Aren't the third gen RX7's twin turbo? I take your point though, I doubt they are peers. (Perhaps a low and high speed setup?).
Sep 19, 2001 (8:10 am)
Yes, but I never knew why they designed the rotary turbo system the way they did. Twin turbos give you twice the heat, remember, (well, two heat sources to cool I mean) and that was certainly an issue with the RX-7. Of course, mazda engineers are smarter about those things than I am, but I have done some studying and really don't grasp the logic of what they did.
I suspect it was a space-saving compromise, and in a sense, it may have been easier for this particular application to service each rotor separately. But if Saab, say, can effectively turobcharge a 2.0 liter inline 4 with a turbo the size of a softball, I don't see why Mazda needed two.
Sep 19, 2001 (11:33 am)
That's a problem I have with turbo's generally. Aside from the clean air and clean oil needs, you've got this red hot heat sink under the hood. A few years of cooking the connectors / hoses / wiring and just generally hotter conditions are bound to take their toll.
Sep 19, 2001 (6:44 pm)
I always thought the reason to have twin turbos was that small turbos spooled up quicker, so you got less lag.
#19 of 23 Twin turbos.
Sep 19, 2001 (8:33 pm)
On a V8 (or 6 I suppose) you also get shorter and equally sized path lengths from the blowers. I expect that if you talked to someone from Garrett, that there is a lot of strange science to housing sizing and design to achieve desired results.
#20 of 23 Just to hijack the discussion
Sep 19, 2001 (8:43 pm)
But it is project related. Has anyone driven one of the V8 conversion (215 BOP) MGBs? The procedure seems to be well documented (and the factory *has* been down that road) and I kind of like the idea. I expect there are cooling issues (as always) but those engines are good to 300 cid or so.
Another one I'd like to see would be a V8 Jensen-Healey. It wouldn't bother me to see one torn up for a hotrod project and they are kind of pretty. A really bitchin' result would be something as fast as a modern Cobra kitcar without all the Shelby nonsense attached to it. (I'm seeing wwwway to many of those nowadays, must be Factory Five's success).
Speaking of Shelby, I say a Boss 302 this weekend with a real live, official Carroll Shelby signature on the glovebox door. Considering he had zipola to do with those cars, what in the heck is that all about? Maybe I can get him to sign my refrigerator or something (or get Larry Shinoda <rip> to sign a Cobra).
Sep 20, 2001 (8:12 am)
The 215 is a lazy engine and a gas hog and really, you can modify an MGB 4- cylinder engine to just about equal the performance without all the hassle of a conversion. The MGB V8s are called Costello V8s but were never imported into the US.
if you want a Camaro, buy a Camaro, I think you'd be disappointed in a V8 MGB.
#22 of 23 back to the 66 vette
Sep 21, 2001 (7:24 am)
i'm wondering if anybody out there has any educated guesses as to how much horse/torque the existing components can "safely" handle. I understand that 700+ might be pushing it a little, but what would be a "reasonable" level.
Sep 21, 2001 (8:15 am)
Quite honestly, aside from the drivetrain, I'd guess that the stock 66 Vette is already overstressed for the power it has.
I think you'd reach a point where, if you increased HP tremendously, you'd end up with just a "shell", like a NASCAR racer...it's a completely different car underneath.