White_FC

Wow.....

those primary ports are _HUGE_



I like it...



How'd it drive? (like, low rpm stuff) no hesitations or anything silly? how'd it idle?



Hrmm... I just cut into the tension bolt hole in one of my housings... grrr... and i slipped and cut my finger with my cutting tool at the same time.. grrrrrr... not happy..



having a small (2mm?) hole going into the tension bolt hole wont cause any real damage, no? just carbon up the tension bolt hole a bit huh?

sleeper7

https://www.nopistons.com/forums/ind...howtopic=35643



These ports were done on the suggestion of a rx7 tuning shop here in Japan. I thought he was playing me and saying port up and big for my goals. I took the housing to show him and he said they are only a "spec 1" port to him. Then he showed me some templates of his exhaust ports. You have to see his "spec 3" ports. His spec 3 ports are a lot bigger then the ones pictured. Asked him about overlap, he seemed like it meant nothing to him. Asked him about turbo a/r a wheel trim, his response was he would have to test exhaust back pressure at different boost levels to say which is better, .96 a/r q-trim cut 15deg or a 1.15a/r q-trim. He is real big on testing exhaust back pressure. beginning to see how everything has to match in order to see/feel all the potential of porting. every time I asked about how big a port should be he asked what type of turbo. Had more question to ask him but I have not yet spent a dime at his shop so I did not what to take up to much of his time. I don't understand how one can ask, is there data on huge exhaust ports with everything being the same? It would be crazy to test large exhaust port efficiency with the stock intake ports. The potential gain would be limited. Have to have the intake match the exhaust in order to see the total HP gain. Is what works best is to have the air flow through the motor smoothly. Big bridge ported intakes have to have very large exhaust ports to see there maximum potential. I guess what I am trying to say about exhaut porting is, what type of power are you looking for and what are your supporting mods to see the benifits of large ports? pic below is the same port as the link above. shows diffuser being ported up.

chuck

sleeper7

Here is a pic of his spec 3 port. This is what he suggest for a very large turbo.

These ports of for daily drivers, not only race cars.

chuck

sleeper7

Just another pic of his suggested port for a given turbo.

chuck

mazdaspeed7

The stock comp hates me, but the drivability is better than most modded n/a's Ive driven. It starts right up, holds an idle while warming up, and never stalls. On-off throttle is very very touchy, but what FC isnt. My car has always been like that, even when it was stock. BTW, I have no thermowax or any emissions of any sort, and all 6 ports are always open. I cant dial out the hunting idle, the tps is dead on, and if I drop the idle speed anymore, the doesnt idle as smooth. Thanks to the stock ecu, and its great dislike for my engine, the drivability could be better. To me, the drivability is just fine. But the one friend who has driven my car said it was very hard to drive smooth. But the majority of that had to do with the on-off throttle touchiness, and the clutch.



I ordered myself a megasquirt today. That should take car of my ECU issues, and give me back all that power Im missing thanks to my stock ecu.



Im used to the engine, so to me, the drivability is just fine. I have no problem in traffic or driving around. The car feels as naturalas any other car. The low end, while it wont win you any stump pullign contests, is perfectly adequate for normal driving. 1500 rpm in 2nd gear? No problem.

White_FC

Sounds great Mazdaspeed7, i'm running a microtech so i'm not too concerned about the stock ECU's limits



What center plate is that? is it a S5 one? Do you think I could port out my S4 N/A plate that far?

mazdaspeed7

Thats a S5 n/a block, Ill double check the S4 irons, but the EGR passages may limit it. I need to check the casting thickness. I dont think it showed up in that pic, but the upper edge of th eport is angled quite a bit. I had to do that to not compromise the casting. If you went straight down from the upper edge, you would be around 1/4" past the edge of the casting by the far side of the runner.



The whole package is what determines how good the drivability will be. If you have it set up so everything works well with everything else, and have it tuned well, drivability will be very good. If you just slap a bunch of things together, drivability will suffer. My car is not running anywhere near its potential right now, because the stock ecu and intake manifold are very far from ideal for my engine. Once those are worked out, my car should be a totally different animal. My goal is drivability thats on par with any new car as it sits on the dealers lot. Its definately a tall order, but the pieces are falling into place.

White_FC

Yeah that would be great if I could get your advice on how much 'meat' there is between the S5 and S4 center irons.. i don't _really_ want to stuff this one up as its in pretty good shape



I'm thinking about a dual throat TB setup on a webber manifold for my engine.. A bit easier to play with runner lengths and what not that way. I'd love a quad throttle body setup using the stock LIM, but that just sounds like too much work for me right now, I really just want to drive my Rx again...



I might have to get a new exhaust manifold made up now to take full advantage of the big(no sleeve) exhaust ports now though...

Ranzo

I think most people overlook the importance of having the exhaust port big enough do dispell all the burnt waste in order to fill the chamber on the next go around. On a Rotary the on exhaust port has to flow enough air to empy three chambers one after the other as opposed to a piston engine has one dedicated valve for each cylinder.

kahren

well yea, but the rotary just has more constant flow instead of the pistons longer dwell time.