Jakor

Well, I finally blew a coolant seal, so it's time for a rebuild. I'm also gonna take this time to build a custom intake and install megasquirt. I've been throwing out ideas, but have a few questions.



For clarification, I own an 86 base model. I'm also going for a giant streetport tuned for around 7500rpm. In a year I'll probably add a 100 shot of nitrous for drag racing.



One of the biggest questions I have is about the secondaries and sixth ports. What happens to drivability if I streetport the primaries as large as I can, and build an intake that is around 10-12" long? (doing the math the primaries with a reflective value of 3 is right around there.) And then I combine the secondaires an sixth ports into one large port. I would end up with 3 throttle bodies (one for the primaries, and two for the outside secondaries/sixth ports.) And then open up the secondaries/sixth ports later just like the sixth ports open when stock. If I'm running solely off the primaries with a streetport, am I going to make enough power to be streetable down low?



I am figuring that running it like this will make it drive almost like stock maby a hair less power down low, but a giant monster when the other two throttle bodies open up. With just the primaries, I'll probably keep enough velocity to be able to drive the car through town, but when I open the secondaries I'll have enough airflow to support power up to 7500rpm with a redline at 8000. I'm thinking this would be like a streetported four port motor with the velocity down low to keep more driveability.



Reminder: I will be running megasquirt, so tuning/opening up of the secondaries shouldn't matter as the timing will all be in the tuning.



This is just one of my possibilities that I'm working on. I'd like to have enough power down at the drags, but I also enjoy autocrossing. Any ideas are welcome as I'm still brainstorming the whole project. Thank you!

Jakor

Not to double post, but I have more to add which would warrent it's own post.



So a friend and I were throwing together designs for this intake. I have two n/a throttle bodies and we were thinking of using both of them in the setup. We would turn them sideways so it looked kind of like this:

[8o o8]

.^--Secondaries (normally the top two throttle plates)

...^--Primary (normally the bottom throttle plate)

.......^--Primary (normally the bottom throttle plate)

.........^--Secondaries (normally the top two throttle plates)



We would use both the primary throttle plates (bottom of the three) to feed into a plenum. This plenum would then have two pipes each feeding a different rotor's primary port. Each of these pipes would have fuel injectors + the stock oil injectors running into them.



I could then cut the top throttle plates in the throttle bodies and run four seperate pipes (or not cut them and combine the secondaries/aux) each with their own injector (and nitrous injector later), one to each secondary/aux port. These runners would all be to the right size for each of the ports opening/closing timings. As well as keeping the runners tapering down from throttle plate size to port size to increase velocity on each pipe. The plenum for the primaries would help keep low end power the same way a plenum does on older muscle cars.



I could time the primaries to start openning one side of the throttle plate first then the other one and have them both open full at the same time (like a four barrel carb) in order to keep low end response and a bit better gas mileage while cruising. The secondary throttle plates (leading straight to their ports) I would run an electric stepper motor through megasquirt in order to open them when I wanted (To be determined while tuning).



My friend and I are going to work the design out in Autocad soon so I can get pictures.



This is one of the best combinations we could come up with so far. It seems to offer all the high end power that I am looking for while still offering for me to drive to work at under 80mph.

j200pruf

What would be HUGE. think the FD had 3x50mm this set up would be 6x45mm for every single port.



I have dreamed up something like yours but using GSXR throttle bodies (cheap and range between 4x45mm too 4x48mm). They are really cheap on ebay and they have aux throttle plates controlled by stepper motors, most ebay auctions have the motors included with injectors.

Jakor

Hmm. I did decide that the two throttle bodies would be too much air flow. At first I figured with them all tapering down I could keep some velocity, but in the end, it would have been too much. GSXR throttle bodies huh? After a quick look, I do believe that those would do it. and the stepper motors would save me much trouble and research into finding some! Thanks for the pointer! Is this the 01-03 model or just the 04+ model GSXR?



Do you think I'll be able to keep decent enough power running through just the primaries alone? If I am running just the primaries down low, will I need to make my runner length longer to shift the power lower? I've lived with the sixth ports wired open most of the time on my old motor and didn't mind the little loss of low end.



I'm off to do more research on the gsxr =p

inanimate_object

The gixxer tb's are good because they're not all moulded together like on some other bikes - means you can alter the distances between them to suit different engines - or use less of them which is handy for a rotary. Alternatively you could take a look at some big v-twins, same advantage and you're only paying for 2 and the injectors that would come with might be enough for a rotary?



Anyway here's a great link all about the gixxer ones: http://www.everettmail.co.uk/mods/mo...tle_bodies.htm

j200pruf

Lots of bikes have the secondary throttle plates controlled by stepper motors, something about making on-off-on throttle trasitions less choppy.



I found what I think to be a better TB based on size alone (trying to see about mounting). They are 45mm inner diameter and also have the secondary throttles controlled by a stepper motor.

BLUE TII

Regardimg your idea of porting the primary ports huge and the 2ndary and Aux ports together into one large port.



This has been done on race engines (Dave Lemon @ Mazdatruix) and the result is it is very hard to get the power to peak below 10,000rpm playing with full race intake and exhaust manifold designs and it is hard to get the engine to hold together for a race at 10,000rpm.



The problem is the port volume is so large that it requires those rpms to get the velocity up high enough to counter reversion from the late aux port timing.



The NA 6 port motors I have seen dyno high near stock rpm have had mild porting done to them. The stock Aux ports overcome their late closing timing with their small runner diameter and Dynamic Effect Intake tuning that provides nearly 2psi of boost!



You have to design an intake system that takes advantage of velocity and DEI better than mazda did. The S5 manifold has more advanced DEI tuning than S4 manifold and RX-8 manifold has much more advanced DEI tuning and velocity/flow tuning than S5.





For bigger ports without going too big I would think you could make your stock 2ndary ports your small primary ports, port your stock primaries huge as your 2ndaries and clean up the Aux ports. Some stock mazda engines used tall intermediate plate ports as the 2ndaries before primary inectors were put there.



Now your intake manifold will have to seperate the runners for the Aux ports, but as you seen from the RX-8 manifold you should do that anyways.

iceblue

Over looked to often is the relationship to port timing and runner design. It fathoms me how so many people think they can just slap something together and out engineer Mazda. They key advantage when running stock redline and port timing comparison is just improving the design of the factory. Mazda already did the homework for you stop trying to reinvent the wheel. Just improve on what they were cost prohibited to do. Such as multi staged TB's and individual runners and lengths. This takes allot of skill and knowledge but does yield good improvements. I am easily seeing in the 35% range of increase and higher.

Jakor

AH.. Now that's an interesting idea I'm going to have to play with. I had been meaning to go talk to you about my design, but having a blow up 7 and gas prices the way they are... =p I'll probably meet up with you at the next autocross if i'm off from work.



@iceblue:

I'm not trying to reinvent the wheel. I'm just changing the tires on the wheel for a different application =p



Mazda did a real decent job on their intake runners (casting could've been better, but it's mass produced...) I'm looking for as much top end as I can get while still keeping street driveability. I'm not trying to just throw stuff together. "Shorter is better" isn't my thing(otherwise I'd just shell out the money and buy the short runner setup from tweakit.net). This is like saying "Bigger is better." I may have been throwing out idea's about combining the secondaries/auxillaries, but that was because I figured it would make a slightly bigger four port motor. I am getting my information together and doing some rough planing so that I don't just run in as soon as my motor is apart and start randomly cutting. I think I can add a couple of trix or plan something well enough that coupled with extensive tuning, I can make more power on top, and still keep driveablity on the street.



I'm sure the cost to get a somewhat complex manifold into mass production would out weigh the the profits one would make, so why design anything like this manifold from a business perspective. If you are going to sell it, make it either pure streetable, or pure race. People who want in between can make their own or do what they can off the streetable manifold. This is why I believe that I can make a better intake than anything available on the market.



I'm willing to build it myself for the edjucation. A year and six months ago, I did my first oil change. I've now fixed many major problems on the few car's I've owned. I only had fun fixing my seven up. Just about everything I know about cars I've learned from working on my 7. And I've been working at Kragen for over a year now. I have discovered that I didn't hate cars, but I liked working on them. Same thing with fabricating a manifold. I love reading everything I can about any of the physics behind it as well as designing and theorizing about how to make it better. It's stuff I havn't done before, but I'm finding out that I like doing it. It may not be the most practical thing, but if I can gain 1% performance increase from other possibilities and/or I learn and have fun along the way, it's all worth it in the end for me.



We learn from out mistakes, but our tries must still be as edjucated as we can make them.



I apologize for my extremely long posts (They don't start out that way =p), I try to keep them as informational and "non-stupid" as possible. =p Thank you for all your continueing comments and pointers.