So I blew my engine over the weekend

[PercentSevenC]

Anyone else hate the ambiguity of that word?





Yep, I decided to ditch my blow-through turbo Weber plans and instead go with a Camden 7" Roots blower with an Edelbrock 1406 on top. Jeff20B installed it for me on Friday, and I'm pretty pleased with it. I'll get some video once I get the belt to stop squealing.

(And don't worry, the turbo isn't going to waste. It will be installed in my REPU with EFI. )

[P71]

Jealous! If you don't mind me asking, howmuch did that run you and is it available anywhere?

[PercentSevenC]

Atkins/Camden still sell them. They're like $2400 brand new. I got mine for free. Actually, I'm just borrowing it from a friend until he wants it back or I decide to do something else, whichever comes first.

[P71]

What kind of power does it make now? That looks like a great solution to my lack of power...

[PercentSevenC]

My belt slips when I boost hard, so I don't really have an accurate impression of the top-end yet. I will say that it has a good bit more grunt than it did with the Weber 45 DCOE or the Hitachi before it. I barely have to flex my ankle and it takes off.

Atkins estimates a 30% increase, and that seems about right according to my butt dyno. With a better exhaust system and air cleaner, I bet it will be pretty fun. They also have 9" and 12" versions and a variety of pullies if you're looking for even more.

[P71]

I'd expect a lot more then 30HP out of that (and even more torque). How many PSI of boost?

[PercentSevenC]

I was just reading their site, and it looks like they've revised their estimate to "35-50%". Maybe 30% was for the old 5" setup. Or maybe I just have a bad memory.

I've seen as high as 7 PSI before the belt starts slipping.

[P71]

7psi ought to net you pretty damn good, like 50% good! I'd imagine that setup on a stock 105HP 12A with no air pump, a header, and a decent exhaust, plus the removal of the mechanical fan, should make around 190BHP and over 200FtLbs of torque.

[PercentSevenC]

That's probably optimistic for a stockport 12A without a smaller pulley than the -7 it comes with. Well, I plan on taking it to the next cheap dyno day we have, so we'll be able to get a better idea then.

[P71]

Basic physics, air pressure is 14.7 psi and that's what N/A engines run on, if you add an additional 7 psi, that should be 50%. Now granted nothing is perfectly efficient but low-compression engines with low power usually see huge gains from boost (see Ford 2.3 turds and DSM motors). We know what kind of power simple things like exhaust make on even stock port rotaries so I stand by my prediction.

190BHP/210BTQ

So what kind of RWHP/RWTQ should we see at that level? 150/160?

[PercentSevenC]

Originally Posted by P71

Basic physics, air pressure is 14.7 psi and that's what N/A engines run on, if you add an additional 7 psi, that should be 50%. Now granted nothing is perfectly efficient but low-compression engines with low power usually see huge gains from boost (see Ford 2.3 turds and DSM motors). We know what kind of power simple things like exhaust make on even stock port rotaries so I stand by my prediction.

190BHP/210BTQ

So what kind of RWHP/RWTQ should we see at that level? 150/160?

You have to take intake charge temperature into account, too. The thermal efficiency of Roots blowers doesn't tend to be very good. But I'd be very interested in seeing the results if you do go this route.

Basically, if you're looking for monstrous power, look elsewhere. But the drivability and throttle response are outstanding. It feels more powerful than it probably is. And it makes such a lovely sound. Yes, I agree, turbos are "better", but supercharged rotaries certainly put a smile on your face. I'll be able to compare the two directly after I build my REPU's new engine.

[85rx-7gsl-se]

Nice, bet it does some nice burnout But turbo>sc :P

[Jeff20B]

Expect no more than about 170HP and maybe 150TQ. Even less for a 12A.

[Whizbang]

how would the supercharger work with a bridgeport?

[PercentSevenC]

Ask 84stock on the other forum. He's running a 7" Camden with a half-bridge 13B. Some say it's not good to have a lot of overlap on a supercharged engine. I don't really know much about it. The supercharger does, however, smooth out the idle a lot.