E Production Ports
 

I was just curious if anyone had any pictures of these ports? I know these cars make pretty decent power for a 6 port and i'm just curious how the ports look. I don't see many people talking about them. Is that because they are un-streetable? . . . or just because they are for race motors and no one wants anyone else to see there port?

It's a street port under this definition -http://scca.cdn.racersites.com/prod/Documents/Club%20Rules/Tech%20Forms/StreetPortDefinition.pdf

With the EProd spec street ports, there's some optimization at play too that isn't obvious; despite what the class rules might seem, the engines *are* still breathing through a restrictor; 40mm choke per rotor is pretty big, but it's still a restriction. So it's a bit more complicated than just hogging the things out.

One version has the 6 port irons basically turned into a single big damn port; Paul Yaw used to have pics of that on his site. I think within the scope of the rules you can add material to the aux port sleeves to reduce the runner volume quite a bit and smooth the transition out; at any rate, some engine builders have. It's not like I'm a top engine builder or anything, but I've seen inside a bunch of Nationals grade engines, and had to rebuild one with new irons, though that was a 12A. It goes pretty well.

Streetable... really depends on your personal taste. There's people who drive bridges or peripheral port engines on the street, you know? Having driven both, I'd rather have a peripheral. ;)

I thought that i had seen a picture of one a long time ago that was made into 1 big port. That was what i was really curious about. It seems almost every time someone mentions doing that they are told that the port would be too big . . . but i'm almost positive i've seen it on an eprod engine which as far as i know is one of the most optimized ports for a 6 port motor.

SCCAITS- how is your car running? I love watching your videos on youtube, but i don't think you've posted any recently.

http://www.mazdatrix.com/sccaportrule.htm

i found this link which describes the rules you posted with pictures to go along with it. Very handy but it still doesn't show how the closing of the port is changed.

This is all my take on it, so take it with whatever grains of salt you want.

Fundamentally, the 6 port aux ports close, from the factory, about the same timing as the full MFR peripheral ports do, maybe a bit later. EProd has induction restictions (stock EFI or 40mm chokes on a Weber) and the MFR motors didn't. So it just can't make power as high in the rev range as the MFR motors did; spin that high, sure, but torque is going to be dropping off due to induction restrictions. So there's no real reason to have the aux ports close later and plenty of reason not to. If you had no rules on induction (meaning big bore ITBs) balanced lightweight internals, etc etc etc... I'm still not sure you'd want to close later than the stock aux ports.

If you don't fill in the runner where the aux port sleeve was a bit somehow, the runner area will be too big and flow velocity (already none too fast due to the size of the port) will likely suffer... that's even ignoring how non-aerodynamic the end of the aux port area is. It's a lot of work to do that without CNC stuff. And the port itself being too big or not... comes down to the question of "too big for what?" They're the right size for racing in EProd, possibly... you could run them on the street if you were willing, but why? I haven't seen direct graph to graph proof, but I'd be willing to bet that a bridgeport built on 4 port irons would make more peak power and more torque across the powerband, with the powerband starting lower in the RPM range.

the 6 ports have some compromises which work in a STOCK car to give a broad power band, but conspire to work against you when you try to make power with them.

1. the late closing ports. they close @75 or 80, the late MFR ports also close @80. so the 6 port stuff closes at the same time as the full race stuff. late closing = high rpm power peak.

2. late opening. the 6 ports open @-32, the MFR ports open @+80.... the 6 ports essentially have zero port overlap, which is what is needed to make it emissions compliant, but the late opening doesn't help power.

3. port size. the 6 ports are actually quite big, they are about the same size as the older MFR p ports. so they are sized well already and this is partly why making them bigger doesn't help much

4. port design. this sucks, i'm not sure why/how exactly, but it just does. so you have a big port that is timed to work @high rpm, which gives a soggy low end, but then the port design sucks, so you don't get any top end either.

the post script is that i've seen the mariah car, which supposedly has the yaw motor in it, run at the track and its slOOOooooooooOOOOOooooow. just based on laptimes its making about half the rumored hp, although the pics are from 2005ish, and i saw the car in 2008-2009, so they had plenty of time to build a sucky motor and put a driver in it that wasn't fast.

like this port?

This is kinda interesting, as I know of a 12A PP that has 40mm intake restrictors as per class rules and makes 265rwhp at just over 10,000rpm (dyno dependent of course). The throttle bores are 48mm, also as per class rules. Even though it's intake restricted (which gives it good mid range power) it still makes peak power at relatively high rpm.

Does anyone know what HP the Eprod engines are making?

Racing this weekend on a new motor, if I have time next week maybe I'll put together a video. Testing yesterday sucked as I spent the day having to change out the clutch at the track.


That depends on the dyno, 12a, 13b, 13b Renesis, etc. Figure about low 200's at the rear wheels. I have personally seen a Mustang read 15hp higher than a Dynojet on the same car on the same day. Numbers don't mean that much.

Big issue you run into with Production is if you desire to use fuel injection you must use the stock intake manifold. You can port an engine to make big numbers at 8-9k, but the stock intakes are never going to support that.

I'll throw this out there for the first time. Motec EFI,13B, stock S5 manifold, ceramic seals, ports to the rules. Built by a team that EVERYBODY identifies with Mazda for a customer that gave them a blank check. 238hp at the flywheel.

185 WHP, although I believe his engine was a bit tired:

http://www.youtube.com/watch?v=6cR1Mp5rqrc

The highest I've heard is 267hp on an engine dyno. Peak hp came between 9200-9400 rpm.
It probably equates to around 220-225 whp on a dynojet.

This was on a well built FC EP car. It was carb though, webber 48 or 51 downdraft, can't remember which one.

That's about what I've always figured. For other reference, in whatever SCCA magazine that featured him before his death, Tom Thrash claimed, I believe, 215hp for the 12A and 230 for the 13B.

Well the thing is, with all of that surface area, you're NOT seeing the same area. There's a good amount of airflow attached to the walls that doesn't flow, so the actual area of airflow is smaller. Additionally, there's all of the additional friction associated with having roughly 1.4x the surface area.

It's my estimation that by the time the port timing is to the point where it's not losing much power from closing so late, the airflow is choked off by the tiny ports.

You can make power with a 6-port, but you can make more power with a 4-port using less timing.

This person also publicly stated elsewhere low 200rwhp for a 13b EP motor.

Maybe this should have been in bold to add more credibility? "Built by a team that EVERYBODY identifies with Mazda"

Let's not give it all away Mark.

Unless he posts something publicly it's never been repeated by me.... and if he does post names are left out as well as a direct quote so no one can Google it to see more :)

Related to the number of points on a rotor perhaps?

Nope, good guess though.

This thread has gotten more responses than i initially thought it would. I appreciate everyone's input and i'm thrilled that almost everyone i've come to respect in this section of the forum has contributed in someway to this thread so thank you!

In summary is it safe to say that the 6 ports are incredibly difficult to optimize because of the timing to flow ratio of the port? (too much timing, not enough flow) I was honestly hoping that it would be possible to see results similar to what Logan achieved on his street ported 13b-re engine, but it appears that might be a difficult task to accomplish.

Next winter i am going to have to start on my senior project for my mechanical engineering degree. I would really love to be able to do something related with naturally aspirated rotaries. I just need to find a good/reasonable topic to test on . . . luckily we have access to a few engine dynamometers in our engines lab that i might be able to borrow :) I'll just have to get permission to use one