Lynn E. Hanover

Hello Federal!!!!



You could stick your head in that port and look around. I think we are passed the point of worry about exhaust port size.



However. you can nearly double the port flow jut with what I described above. I would (having seen the intake) go a bit wider than stock and open a bit sooner.



Draw a line across the bottom of the port and go below that lin with another line to port to. I would go 1/8" and port even with the floor to that line, and down another 1/8" with just the front of a very smooth radius.



On the intake port:



Between the arrows on the left, I would add a generous radius. Polished even. This is where the trailing end of the side seal comes back up onto the flat part of the side housing. Of special interest is where the end of the side seal tracks up the end of the port. If you have the end come up after the unsupported part is back on the flat, then it won't wear out for a long long time.



Ink up the area with a marking pen. Bend the end of a side seal spring up so it sticks out of the groove right beside the corner seal Put the rotor on the iron and turn it with the crank. The side seal spring will make a scratch in the ink where the end of the side seal tracks along the iron.



On the inner part of the bridge port opening, you can use strips of a 4" X 24" sanding belt, torn into 1/2" wide strips and strung through the port. Just hold onto the ends and drag it back and forth like shining an upside down shoe, to smooth that radius that no tool can reach. ( the right two arrows).



If I am not being clear, just tell me. (Nice nails).



Lynn E. Hanover

Travis R

MS, I was planning on running an extrude honed S4 manifold. The problem is that I'm penalized with 175lbs if I don't use the stock throttle and intake. I also have to keep the same number and location of injectors.

The lower weight (1900lbs vs 2075lbs) is the only real advantage I have, so I'd rather not give that up if I can get acceptable power with the "stock" intake.

Any thoughts on the power limitations of a well ported S4 intake?

If it turns out that I can't get the car that light then, it makes my decision a lot easier.

mazdaspeed7

That changes things some. Modifying an engine is nothing more than shifting compromises. Racing class regulations will have a strong effect on how you can shift those compromises. Could you give a little more info on your setup? An extrude honed S4 intake shouldnt pose much of a problem. Especially if you only have a SP engine. The biggest downside to the S4 manifold is the narrow runners. But extrude honing should make that less of an issue. With the exception of your circumstances though, Id recommend the money spent on extrude honing could be better spend on a non-OEM of custom intake manifold. The hp/dollar gains arent going to be as good as with a non-OEM manifold, but the weight penalty in your case has a lot of influence on your choice. Weight affects everything, not just acceleration. You will have more tire wear, more brake wear, not as much lateral grip, slower transitions, etc. Basically, everything but ride quality will suffer with more weight.

Travis R

You are absolutely right about compromises and trade offs. This car will be a dedicated autocross car (F-Prepared), and never driven on the street. Ride quality is one of the things that I will galdly give up in favor of better handling. I will probably start out with springs in the 350-450 lb/in range.

My main competition locally is a couple of Datsun 240Z's. They have to weigh 2200lbs, but have GOBS of torque. Nationally there is a stripped out BMW E36 with a fully prep'd 3.2L (talk about power), that also has to weigh 2200lbs. Hopefully they will add weight to that car though. That's why I said the weight was my only real advantage. 2075lbs is still a little bit of an advantage, but not as much as 1900lbs. Obviously I will need as much power as possible to exploit it at every opportunity. We have discussed the possiblilty of an Aux. bridge port motor, with the 5th/6th port actuators still in place, in the past, but obviously there will be a problem of intake tuning once the aux. ports open if I'm using the stock intake... one side bridged one side not.

I thought the aux bridge might provide a reasonable compromise between ultimate HP and minimizing the loss of low end torque.

The other benefit fo a motor like this is cheaper parts. I could say screw it and go all out, full bridge port, custom intake, etc. and rev the **** out of the motor (over 10K rpm). But then more money has to be spent to clearance the rotors, or getting a 2 piece eccentric shaft (not sure if adding a 3rd bearing is even legal), plus it gets harder to find a clutch that can take those rpms.

So basically it comes down to this: How much power can I get out of an engine with a stock manifold (S4 or S5)(with a full stand alone ECU of course), and will that be enough to be competitive against cars with A LOT more torque.

Thanks for the help...

And sorry about hijacking the thread.

j9fd3s

with a stock unported s4/s5 intake you're looking at 150-160rwhp, maybe 5-10 more if you port the whee out of the motor

j9fd3s

what exactly will they let you do to the motor. ie for us in its/ps1, exhaust is open, we can do pullies and a cone filter, and any ecu that will fit into the stock case.



what specifically can you do?

Travis R

Sorry I didn't mean stock manifold I meant "stock", as in "It only looks the same on the outside". I would like to extrude hone it, like I mentioned above, to increase flow.

j9fd3s

ah ok you need to do that. can you run a 4 port?

Travis R

I can port it pretty much how ever I want, but I'm not allowed to "change the volume of the working chamber"... meaning I can't fill in the rotors to up the compression ratio. And I get a 175lb weight penalty for using a non-stock intake and throttle body.

Everything else is pretty much fair game.

j9fd3s

can you run an "old school" 4 port 13b with 9.7 rotors?