jg1000

Hi am Jameson here from Kansas City.

I am looking at purchasing a car with a 4 port 13b that's carb'd. Can I buy a t2 intake manifold and exhaust to turbo charged this motor?

RotaryEvolution

iTrader: (30)

you would need more specs on the engine to know what will work, there are older 4 port 13B engines which came carbed which a turbo intake will not bolt to without a bit of modification.

then there is compression ratio, if the engine was rebuilt it could have a number of different ratios in it. you can turbocharge any rotary engine but knowing the engine's limitations is something you will need to know first. running stock boost level for the ECU you use is fine for just about any compression level, if you raise it though then the compression ratios play a role after 10psi.

if it is an unmolested 4 port turbo engine then you could slap all the turbo components back on it from the stock setup and run factory boost without hassle.

jg1000

Thanks for the reply. This is an older carb motor with 3mm apex seal rotors. Not sure what these are compression wise. I have built a few rotaries in my younger years with na rotors and know the threshold or spark knock is something to keep in mind. I would most likely be setting it up for 300-350whp and using water injection. But I was hoping i could use a t2 intake and exhaust manifold and run megasquirt. But am not familiar with the older 13b 4 port motors.

RotaryEvolution

iTrader: (30)

problem with the old carbed 13B is there is no ports in the center iron for the primary injectors. you could modify the lower intake to accept the primaries and also to bolt to the early series block but it is going to take a chunk of fabrication to make it work.

it's almost easier to just do a blowthrough turbo carb on those older engines.

the next best step would be to avoid the old school engine if you want to go fuel injection and use the GSL-SE or a post 1986 engine(preferrably a 4 port turbo engine already rebuilt to handle some power).

peejay

As mentioned the manifolds WILL NOT bolt up, plus IMO the engine really won't take well to turbocharging. 3mm seals suck, the older rotor housings have crappy chrome (not helped any by the heavy 3mm seals!), and the base block isn't as strong... you'd be far better off selling off all of the rare/valuable 4-port 13B parts and just buying a Turbo II engine complete.

jg1000

Roughly how much power does a half bridge ported 4 port 13b make ?

RotaryEvolution

iTrader: (30)

power is relevant to your turbo, not so much the engine.

but an older engine without any reinforcement and the 3mm seals i would be hard pressed to recommend higher than 300whp. a stock S4/5 turbo is good for about 275whp, the FD twins about 350 in stock form and 400-ish modified for non sequential and ported.

the bridge will just shift your power band up slightly, giving room for a little more power up top but it is not a large increase(5-10% at 9k+ RPMs) in power unless the porting and engine built more radically to support a really high revving engine and putting a turbo on it will work against that ideal(turbo engines should normally be limited to 8-8.5K for a street driven car).

jg1000

I was wondering what it roughly makes NA. Again 4 port with GSL-SE rotors , half bridge port , racing beat full exhaust, 48 IDA carbies.

RotaryEvolution

iTrader: (30)

maybe 225whp if it is setup and tuned well.

jg1000

Awesome, Thanks.

placd1

iTrader: (3)

I think that figure is a bit optimistic.

jg1000

Why do you say that? Seems that the 6 port guys with fuel injection are getting close to 200whp. This motor has down draft carbs full RB exhaust and is an early 4 port. Which from my searching seems that 225whp is a fairly good estimate. Of course I can't find a single dyno graph; )

RotaryEvolution

iTrader: (30)

it's a 4 port, bridged and carbed. i could be off on the 48's upper end capability but the engine, porting and intake should be able to handle it. this isn't a non turbo fuel injected engine with built in limitations.

placd1

iTrader: (3)

From personal experience I can attest that the particular setup that he mentioned, i.e. 4 port with GSL-SE rotors , half bridge port , racing beat full exhaust, 48 IDA carb, isn't going to make 225 hp at the wheels. Best he can hope for with that combo is 195 whp. Dare you to find a dyno graph that reports a higher figure anywhere! As RotaryEvolution alluded to, 225 whp is an estimate at the upper end of the spectrum based on aggressive tuning and a top notch setup. That would mean a Weber 51 IDA in place of the 48 to even have a hope of seeing 225 whp.

RotaryEvolution

iTrader: (30)

that was the intent, an upper figure that might be possible given the ideal setup and tune.

peejay

The RB exhaust will choke it.

I'm on roughly 230 crank HP with a full bridge, I know the exhaust is a limitation but I like a quiet car.

I was on about 210 crank HP with a half bridge T2 block with a different (louder yet more restrictive) exhaust on it. Power actually went down after I half bridged it (was slower than when it was a ~200hp street port) but midrange torque went up dramatically. Then I played with intake manifolds some and I got the top end power back along with keeping the mid range.

I still kinda want to try my fancy intake manifold on a non bridge ported Turbo II block again, just to see what it would be like compared to the craptacular TII intake manifold, but that would require putting a non bridge ported engine in my car and I don't think I ever want to go back. They just drive too nicely, the power is everywhere instead of a 5500rpm lightswitch like a street port.