fidelity101

iTrader: (11)

Due to some racing classes rotaries are poo-poo'd on and simple things like a streetport bumps you out of a class and/or turbos are not allowed. So how have some of you overcome this stock port rules for a 13b?

Whats the best (biggest) stock ports if you had to piece together something?

REW irons + s6 housings? Where are some other good suggestions? I've seen the mazdatrix using the renesis center iron that looked pretty cool and scalloping the rotors is an option. It is costly but nothing NA and rotary is cheap these days...

lastphaseofthis

iTrader: (8)

13b-RE from cosmos have the largest ports. i guess if they knew about scalloping rotors they would deny that too..

j9fd3s

iTrader: (3)

the cosmo end irons with the FD center, i believe is the biggest stock porting setup.

peejay

If you're looking at entering stage rally, look closely at what the Group 2 rules say. I think they say the engine must be "Improved Touring" legal which means basically you're stuck with a 6-port since that's what's legal for your car.

fidelity101

iTrader: (11)

Its pretty vague:

strictest

so 20bs are allowed and any porting go nuts basically.


somewhere in between.

peejay

OE porting and induction = hunt down a 13B-RE. Assuming that they mean OE for the engine and not OE for the chassis.

An engine with Turbo II rotor housings and FD intermediate housing and 13B-RE end housings is not "OE porting" by any stretch. For that matter you can buy bridge ported side housings from Mazda Motorsports.

Gilgamesh

Improved touring s5 6port motors make between 190-200 on well built motors.

Banzai has this on their website:
Banzai Racing (Keefer 13B RX-7 Engine Installation)


I have tried looking for other stock porting 4 port 13B NA dynos but i haven't came up with anything. SCCA STL class allows engine swaps, you can submit an engine to be added to a list and i thought about the 4 port turbo motors minus the turbos, but they would need to make more power than the S5 NA motor to make sense.

fidelity101

iTrader: (11)

Nope, you can swap engines to update/backdate in open class you can't for production. 2WD are classified as open. Hence why you see old jettas/gtis with newer 2.0s or VR6s. You must keep the engine within the same OE generally because apparently people were stuffing 13bs into starlets and rally the pants off them and that's how the rule started.

peejay

I think the best option would be a Duratec with good rods and pistons with some compression, ITBs, and headers. Make waaaay more than any stock port/stock manifold rotary.

With mild cams this is a 300 crank HP engine. And you'll never put that much power down anyway. Group 2 legal. And you probably won't have to change the catalyst at every service!

Or just run anything in there until you get enough coefficients that you can run Group 5. Fun rotaries will always be hampered by the catalyst rule unless you find an SA rally car.

fidelity101

iTrader: (11)

yeah some of the rules are bullshit for what the equivalent piston engine can do modification wise.

oh well, see you at snowdrift!

I also plan on putting the catalyst on the very back like so:

Kenku

I talked to Mike Hurst about this via email - he said basically the rules were written to keep peripheral ports out of Group 2 but floated the idea of allowing street ports if anyone was going to bring a car. Especially given performance potential of other legal options in the class.

Following the rules as written, I think there's an argument for a Renesis, in the "bang the engine in and go run it" sense, or an S5 NA engine with aggressive tuning.

I do want to do a Duratec build though, just not in a 7. Peejay, did you see what Esslinger parts bin engineered? Apparently the TIVCT Focus head is really really good.

fidelity101

iTrader: (11)

I dont know whats harder... turning my rx8 into a rallycar or putting a renesis in my FC using all the whizbang intake manifold/injection from the rx8.

peejay

So someone should suggest upgrading the ruleset to E/Prepared, then. That allows a lot of leeway as long as the port window doesn't extend beyond both side seal tips.

No idea, all I know of Esslinger is the stuff they do with Limas. Last I heard of them was a tall deck 3.1l that was pushing 400hp with one of their fancy heads.

What I did remember from years back was a company in Kansas that was putting stacks, headers, and 12:1 compression in the Ranger-sourced Duratec, and getting 250hp from 5500-8500, stock head and cams. (NEED better rods to increase redline, period!) Upgrade the cams and the powerband doesn't fall flat, engine making about 300hp peak. Still untouched head casting.

I understand that the 2.5 has much bigger ports, but do you really need that if you can make that much power on untouched early castings? I believe that ports should be as small as possible to meet power goals, this helps make the powerband nice and broad.

Kenku

Esslinger apparently moved to doing Duratec stuff too. They did a motor package for... I don't know what midget class exactly, but it mandates unported head, production block and crank and a 2.4L limit. So it's the Focus head with the direct injection ports plugged, which apparently has a really good port angle for tumble and in-cylinder motion, on a 2.5 block with a Ranger crank. Making well clear of 300hp apparently.

I actually want to get one of those heads to cut up and put on work's flowbench. Well, after I get my 13B flowbench adapter made.

peejay

2.4l, 300hp, rear drive, makes me think of the Opel Manta 400s.

A friend of mine HAD a Manta. He sold it before he did much with it. Kind of sad to see it go, that car was awesome and incredibly light too! Makes you understand how you see four or five people bodily lifting them out of a ditch somewhere in rural Finland

"Unported head, production block and crank" makes me think the class structure was written to allow K24s to run. At least, when I was looking up displacement breaks for pushrod vs. OHC engines, I saw that they were letting K24s run with heavy restriction.

TonyD89

iTrader: (10)

Hybrid K24's are awesome. I dayly a K20 Z1 and know all about putting the head on a K24. The mods to make this even better are endless. I'm surprised at the offers I get for the car just because of the engine and the guys running this **** have fast cars. The first time I saw a K24 with a K20 head (with other performance goodies) go I was amazed. I'm now really searching the duratec just to get the info.

j9fd3s

iTrader: (3)

we're considering an S2000 with a K24 swap as the next race car. ST something is just hp/weight, so more torque is better. plus the K24 is cheap, and the S2000 engine (rc10? jtm45?) isn't.

either that or an FD look good. torque is hard with the FD, but it looks good, and Mazda pays you if you win...

Mustang is choice 3, its expensive, and heavy.

j9fd3s

iTrader: (3)

the 1 point in favor of the 13B-MSP is that the ECU is setup to keep the cat alive as long as possible. if you plug in a code reader you can watch it, it keeps cat temp really steady.

turns out cats want 3 things, which really dictate how you tune the engine.

1. they want an AFR that is 14.7 +/- about .5. 14.7 is almost optimum, the cat actually wants to see the AFR vary slightly.

2. the cat needs to be over 450c to work, and under 650c not to melt. the eagle eyed will notice that if the engine makes max power around 920c, and the cat melts at 650c, the cat may not live very long. i have an EGT on an FD ecu right now, and so far preturbo EGT's have been between 650-800c the whole time. or we all know that the OEM tune is rich up top, and this is partly why.

3. the exhaust pulses on a rotary are super sonic. piston engines are lazy, and the exhaust opens slowly, and velocity is slow, and it only happens once in a while. the Rotary is not lazy, the exhaust happens all the time, and it goes supersonic. its like hitting the cat with a hammer. anything you can do to slow down or even out the pulses will help a lot here.

fidelity101

iTrader: (11)

who cares about boingers?

j9fd3s

iTrader: (3)

billy!

peejay