6 port n/a turbo questions
 

I have done the searching and i can not find anything on the web so here goes.
I am currently working on a 6 port n/a turbo build. My question is... can I combine the 2 secondary intake ports with the primaries to create one large port like the one on a factory turbo motor. I have heard mixed opinions some say it works great others say it ruins the motor and is impossible but none of them have actually done it and they have no numbers or evidence to back up their claims.

HIT The link:
The (Almost) Complete Guide To Turbocharging The Naturally Aspirated Second Generation RX-7

I went to the link you provided. It has a lot of good information. It did not answer my question about modifying the engine but helped me with all the other questions I had. Thank you.

welcome to the board. :)

it would probably help if you started with what you hope to accomplish.

there are better roads to travel if all you want is more power. if this happens to be one of those i-want-to-do-it-because-it's-unique/uncommon-things, then good luck with it, but you may have to get used to the idea of forging ahead with little help.

the simple answer to your question of, basically, can you Siamese-port the engine and then turbocharge it, is yes. of course you can. however, you're basically creating a huge port with high duration and that may have something to do with why it's not common. you will probably be amplifying all the less-than-ideal situations you have to deal with when turbocharging a 6-port.

The goal isn't to do it because its unique. The 13b-tt has one large port instead of the two. I believe mazda did that for a reason. My goal is to have a motor that is built to the max. I don't want to have to open it back up to do more port work because I found something that works better than what I have. I had planned on doing a peripheral and a bridge until the question ( why does the turbo motor have one large port and the n/a motor have 2?) Came up. Once I figure that out then I will continue the build

well, that's good. :)

well, you're right, but the change Mazda made was not to 4 ports, it was to 6. you're right that the turbo blocks are 4 port, but rotaries (as we know them) have always been 4 ports. Mazda designed the 6 port as a way to deal with a few things, but emissions and a good power/torque balance were the main ones. it helps the normally aspirated engines perform better within the confines of a manufacturer.

the part that concerns your plans lies in the port timing. if you look at a 6 port and 4 port side by side, you will notice how much later the 6 port closes, but that extra timing is only utilized when the auxiliary ports are online. with your idea of conjoining them, that timing will be there at all times and while that can work when modifying a N/A engine, a turbo engine doesn't necessarily need or want that much timing.

suffice it to say, if you plan on building a turbo rotary, your best move right now would be to start with a turbo block of some sort - especially if you plan on running REAL power through it.

i'm not sure what peripherals and bridges have to do with your questions. for a peripheral, side ports are irrelevant because, by definition, a peripheral does not use any of them. for bridges, you can bridge both 4 and 6 port engines. obviously you could even bridge a siamese engine as well, but you would really need to have some concept of timing to do so correctly because there wouldn't be a ready-made template for you.

Don't do it. Combine the two secondary ports that is. Here is why: Per Mazdatrix
"If the separate ports (in the end housings) are simply made into one large port, the bottom and mid-range torque suffer a lot, and the port velocity is compromised as the intake flows from the manifold into the intake runner. The intake port timing of this configuration is: later on opening than a peripheral port, but roughly equal to intake closing on a peripheral port! That's a LOT of timing and port volume for a street car. There are MANY combos that could be tried here. We have spent a LOT of time on our engine dyno and have have been very successful in making this type (VERY large) work on our road-race cars, but only at VERY high RPM-- meaning above 9000!"

6-Port Porting

I know they are talking n/a but when your rpm's are low and your not boosting I think a motor with that port is gonna suck. Really you'd need a different turbo anyway as I don't believe the stock turbo is suited for the rpm range that port requires, stock internals can't sustain those rpm's and you'd need a standalone as well.

If at all possible stay with a four port block. If not leave those secondary and aux ports separate and only street port the primaries and secondaries leaving those aux ports alone. They already close way late.

Technically the n/a only had one port in the side housings until 1984 when the GSL-SE came out with the first 6-port motor. When the TII came along it kept the 4 port configuration while the n/a continued on with the 6-port. Diabolical1 had mentioned this, I'm just giving a little more detail.

Whoops. Accidently resurrected this one. Didn't realize the thread I was reading had ended and this was the related thread underneath it.