Without getting into a flame war, was would be the optimum iron config to do a n/a side port engine? Is it still s5 n/a end's with turbo center irons or has a better combo been found?

hooray for an n/a section

 

I dont see where one would benefit from using a turbo center iron arent they basically the same just slightly larger ports? However I could be wrong.

 

It all depends on what your goals are...

A street ported six port with functioning sleeves would give a really nice torque curve...

Street ported TII irons would give a bit more power up high...

A half-bridge isn't worth it IMO for an NA, its too many of the drawbacks of a full bridge without enough benefit. If your going this far just full bridge. UNLESS you plan on designing a custom intake/throttle body setup to make it work right.

Judge ITO built a sweet full bridge on a 6 port and I BELIEVE he used the auxiliary port sleeves to bring back a bit of the midrange and achieve a livable idle.

Other great irons for a full bridge are the pre 85 4 port irons from either a 12A or 13B all pre 85 are interchangeable with each other. You'd just need to use GSL-SE rotor housings.

 

You can port the n/a center plate just as much as you can port the turbo2 center plate. The turbo2 just comes with a bigger port.

As far as the best combination, the 4 port is known to put out more but the six port shouldnt be too far behind. I havent seen enough of both done to compare.

 

sounds like you're limiting this to 6-ports, so in that case, i don't really think it matters much which block you start with. i think a decent streetport on any of the blocks is the best place to start. where i think the significant differences will be made are in using the lightest balanced rotating assembly you can afford (which would probably be S5), and careful attention to intake and exhaust choices (custom work with both is what i feel is best) and of course, your engine management choices. do your homework and i think any 6-port block will get you very pleasing numbers and a good powerband to boot.

if i misunderstood, then i think my choice would have to be building something around the REW block. in fact, that's exactly what i'll be doing as soon as i finish getting a few more parts.

 

I'm using FD Irons for my BP N/A sandwich...

 

Depends on how much work you're willing to do. I'm tinkering with a max-effort streetport build using GSL-SE end irons with a 12A center. Hog out the 6-port end irons EProd style (poke around Yaw's site) and there's far more port and runner area than *any* of the 4-port stuff. Perhaps too much, so I filled in with devcon and smoothed it out to smooth out the slope.

The 12A center iron... I'll put it this way. I've cut up the 12A and S4/S5 EFI center irons, and the 12A not only has larger center ports and runners stock, but it has more meat to port out. On the 12A builds, I use the same template for all 4 ports, and these are not mild streetports by any means.

Of course, this is for an FB. Not sure offhand how you'd make the 12A center irons work for an FC (I think the motor mounts bolt to it somehow, haven't paid much attention, and to use it with the FC end plates or rotor housings you'd have to mill o-ring grooves in it. And needless to say there's no injector holes.

LIS, a bit of work.

 

On the Yaws website, they are using a 13b 4 port turbo2 block, with the s5 rotors. there not using the the 12a center plate. And from what I understand, I think that you can port all the center plates the same. They all have the same amount of meat in them. I could be wrong because I dont know how much meat the 12a's have in them but I know that all the 13b's center plates can be ported the same

 

Not that one, the other one; http://www.yawpower.com/dec2004.html. And I know they're not using the 12A center plate; that motor's built for an FC anyway, and I'm pretty sure the Prod rules wouldn't let you run the 12A plate. I was using it as a reference for the end plate ports.

And from comparing those pics along with some other Nationals-level EProd 13B primary ports that I've seen... again, like I said, the EFI center irons can't be ported as far as the 12A ones, and the runners are smaller. Seriously, the full out street ported primaries are about the same size as the stock ones on the 12As.

Compare http://ham.and.cheese.on.rye.sandwic...s/DSCF0648.jpg to http://ham.and.cheese.on.rye.sandwic...s/DSCF0649.jpg and http://ham.and.cheese.on.rye.sandwic...s/DSCF0650.jpg and see what I mean; in order they're stock S4 NA, stock S2, and street ported S2. You can sorta make the EFI primary ports have the same timing, but it has to be soooooo shallow to avoid breaking through into the water jacket (ones I've seen had that part CNC'd) and the flow capacity's not anywhere near the same.

*edit* Oh yeah, and ignore the condition of the plates; those are all from my junk pile.

 

Yea a 12a center would be the way to go if it could be used.

 

Ok dumb questions and i didnt turn anything up on my search (could have searched wrong too).

But what is the advantage of the 12a center iron?

The RE Cosmo motor is that the same as the FD motor?

 

Like I said, and like the pics I posted show... compared to the EFI 13B center irons, the ports are bigger, the runners are bigger, and there's more meat to open them up.

 

If you are going with a FC motor, you need to use S4.

You can open the 5/6 ports nicely large.. and there isnt a EGR passage in the end housings.

The Center S4 housing is the trick. I have pics at home of the initial porting of the S4 center iron, and a little.. work within the rules of the SCCA. "You can block off or plug EGR and emissions passages" But you cant epoxy the housings. No adding material.

If Im awake enough when I get home, I will find and post the pics. But YES you can port them heavily. And come a world closer to the timing you have on the end housings. (A world closer compared to the S5 housings that is)

 

the words "budget", "bridge" and "EFI" don't belong in the same sentence.

 

Thinking* Couldnt one use Devcon to close the 5th/6th port up a bit to make it more streetable w/o the sleeves? I know I seen Devcon used already w/ the port sleeves.

 

What about the RX-8 rotors. Aren't they lighter? Maybe I'm remembering wrong though.

 

Theres a thread somewhere, possibly the rotary performance or race car tech that sheds some light that the rx8 rotors give very, very little if any gains

 

Even if they don't give any actual hp gains if they are lighter then they would allow for easier revving, right?

 

the problem is they don't seal as well.

 

RX-8 rotors are slightly lighter. Due to their design, you still want to keep the cutoff seal that the Renesis needs. You can leave them out but strangely enough it has been reported that the rotors make less power without them. The RX-7 rotors don't even have them so go figure. When you factor back in the weight of these seals, the total rotor and seal weight is the same as the light 13B rotors. No weight advantage.

They don't seal as well if you use the standard Renesis seals that are stamped for each groove. These have excessively high tolerances. You can purchase seals that are overly long and clearance them yourself though so sealing isn't an issue. The apex seals are only half as tall though. This isn't really the issue that some claim it is either as the stock 3 piece 13B seals are only this high each. They are just stacked. I personally still prefer to use 13B seals (2 piece) but this requires machining the rotors. That takes away any price advantage to using these rotors in the first place.

You do not want to use Renesis corner seals if you can help it. They are very hard and will kill 13b side housings. They don't exactly treat Renesis housings well. However, to use these seals, you need to be using the taller 13B apex seals.