New motor build Idea
 

I'm not sure if anyone has tried this but i think it would be interesting. I want a P-port, really bad, but I was thinking what would be better, what about a P-port and leaving the stock side ports. I was thinking just put a little valve(butterfly or slide) into p-port side and run the stock ports or maybe even smaller(play with some Devcon) at lower RPM's then have a the p-ports open about 3500ish to bring in the extra power. I was thinking use a little vacuum(but more than likely electric on a rpm switch). everyone knows the p-ports make their power up top and mazda designed the smaller ports for the streetcars power is in mid to high rpm range.

I think use a smaller port than stock and slowly mix in the p-port and you could have the ultimate engine. the 4 rotor le-mans car was set up similar to that as it had adjustable intake runners. it was short for the hight rpms and long for the lows and it was controlled in the car. I was thinking use a stepper motor to open the valve in stages.

Imagine being able to control your engine like that, you can use it to step up the power and vise versa to slow it down an maybe pull some decent gas mileage.

I know the hardest part would be making the intake manifold but if it were to be made to work with the valves exactly like I said do you thing it would be worth playing with. I know it would look really crazy under the hood and if it works the potential for power should exceed the standard p-port, right.

I am going to take some welding classes at my school to learn to tig. I plan on making a p-port motor either way and really plan on living my life fabbing up some crazy sh*t,LOL

Really dont what to say but.............:dienewbie lol

First off... the reason peripheral ports make their power up at high RPMs is because that's the way the race motors are built. It's perfectly possible to make a pport that is stronger in the low/midrange, it just needs less timing. So what "everyone knows" is wrong. The reason Mazda eventually went to side ports is that peripheral ports have problems under low-load conditions.

Second, Mazda did some experiments with combinations of peripheral and side ports. Their testing didn't show much advantage over just straight peripheral, but then again I don't think they followed it in too much depth. There's various others who have done combinations of peripheral and side ports; Judge Ito for one. Then again, I'm not 100% sure whether or not his comboport motor is making more power than a modern full-out peripheral port; the ones doing the most development on them are drag guys, and they're wary of letting people know specifics because of how much time they have in development. Maybe Crispeed could comment with more certainty, I can't.

Thirdly, you're far from the first person to suggest the idea of switching between the side and peripheral intake ports depending on engine load. If you think the hardest thing would be fabbing the intake manifold, you don't know enough... the real trick is going to be tuning. You don't want to just vary the peripheral opening based on RPM, because that's a lousy way to do it, and even if you did it'd turn into a bitch to tune well.

Frankly, most people who want the "ultimate" engine just go turbo. Personally, I was kicking around the same basic idea quite a few years ago. I decided against it because... frankly, it doesn't seem worth the bother. According to some you can civilize peripheral ports somewhat with well tuned EFI, and from driving EProd spec motors on the street (for break in, heh heh heh) I've come to the conclusion that all this bitching about engines with no lowend being useless for street use is silly.

Feel free to play around, just might want to do some more digging.

on the street, its tough to beat a turbo setup. you can have power, driveability, it can pass smog, be quiet, and get decent mileage, depending a little on how you set it up.

only real downside to the turbo is that its more complex.

not knocking the semi pp setup at all, but its not really practical on the street.

here's an idea for ya, the NSU wankel spider is a PP motor, but its got 2 intake ports, and a 2 barrel progressive carburator. at low speeds it runs off of a really small 6-8mm intake port with real moderate timing, and then when you step on it, the carb secondary opens, which feeds a larger more radically timed intake port.

oh what the hell ... since you brought it up, might as well use your thread to get some questions answered.

by the way, welcome to the board. it's not a "NEW" idea by any means, but i'll give you 3 points anyway. :)

J9, have you ever driven one? by the way, that's not meant with the challenging tone of skepticism it may appear to have, i'm sincerely asking because i don't know anyone with semi-peripheral, therefore, i've never seen much less driven a semi-peri in real life. i'm curious as to it's characteristics because that's the port configuration i plan to experiment with on my '84, if i can ever get started. hopefuly i haven't just jinxed myself. seriously, i've already decided to do it, so this isn't a question to make up my mind as much as it is for me to gather info for what i'll be dealing with when it comes to life.

fuel consumption aside, what other bases are you using for your statement? (and if you want to take this to PM's that's fine, too)