black_sunshine

Okay, so now I magically have access to any and all types (anything from aluminum, iron, steel, stainless, all the way to titanium) of tubing, mandrel benders, and fabrication equipment (new career!).

Anyhow, let's see. I've got a pretty mild street-port motor (88 GTU). No 5/6 port sleeves or actuators. The intake timing was left alone, but the 1/2nd and the 5/6th ports are enlarged (no timing change). The exhaust ports are matched to the sleeves (TII sleeves).

Currently, I have the stock intake manifold and exhaust manifold with no cats and no presilencer(s).

I don't want to buy something that costs ~$200 when I can build it for $50 (and be a better quality part).

On the exhaust, I was either going to BUY the mazdatrix true-dual exhaust setup, or just buld the headers and misc. pipes (I'd have to buy the mufflers and presilencers). Should I keep it 2.5" all the way? Use a megaphone and expand it to 3"? Kill the true dual exhaust idea in favor of a collected (single) setup? Remember, I DO have a pretty decent street port.

On the intake, I was going to fab a custom manifold. I'd still be using the 88's Dynamic chamber. Everything else would be beautiful 440 electroplated stainless. My question: Where to put the injectors? The RPM range I'm looking at is going to be in the 4k-8k range. Also, should I just ditch the Dynamic chamber in favor of a "surge tank?"

And don't bother feeding me that crap about the roughness of the runners helping to atomize fuel. I've worked closely with many fluid-dynamics engineers. The air-charge doesn't travel within 1/32" of the wall anyways. The help in atomization occurs from the changes in direction of the charge. Even on carbbed systems, the effect is rather nominal at best (given an average roughness of less than 1/32"). In otherwords, I'm not looking for a boost in performance from smoothing the runners, I'm looking for a way to better my powerband through injector placment and killing a restriction (the LIM, which kills the inertia of the intake charge).

Back to the issue: Where should I place the injectors? The runners are going to be stock length and .75" flanged to .5" x 1.5" for 1/2nd ports, and 1.5" flanged to .75" x 2.25" for the 3/5th and 4/6th ports (no actuators).

Planning on running a Haltek E6K, so the AFM isn't an issue. Any input is greatly appreciated!

WHaCKo

Liquid Anarchy

iTrader: (2)

Well I can help a BIT Matt.

1st, collect streetported exhausts. Measure the ID of the sleeves, and match the runners to that. Collect w/ a megaphone, and collect to 2.5'. Anything bigger isn't a good idea. And make 2... I have $50 :-D

Oh... and TURN YOUR IM'S ON!

black_sunshine

IM's are on and ready!

Collected SP? I don't understand why, but sounds good to me (and is a helluva lot cheaper!). $50 for a header? Man, that's MY cost LOL.

Any input on the intake? BTW the measurements I gave above are just approximations.

OC_

i want to see a car dyno'ed with a performance "normal" exhaust vs. the same car with true dules. You would think on an engine with only 2 exhasut ports, have true dules would decrease perfromance.

your going to need pretty short runners to make power at 8,000 rpm. The current runners seem to stop at 7,000. i dont know exactly how long the runner should be on a rotary engine. Surge tank? do you mean plenum? the plenum and runner setup is the best you can have.

injectors should be as close to the engine as possable and aimed directly at the cumbustion chamber. theres some resources on the net, though, very few.

Jimmy325i

I have to disagree on lots of assumptions you guys are making here.

First, You have an extremely mild street port. If you can even call it that. That you're still using the stock exhaust manifold means you're not making any more power than stock anyways.

Second, RB makes a damn fine header for the money. Its chrome plated and 1st rate all the way. You don't sound competent enough based on your reasoning alone to better their dyno proven design. Not only do they have lots of research and developement into their header design, but they have lots of happy customers. How many hours will you spend making a header? I guess you work really cheap because for less than 2 bills delivered they also give you the block off plate to go with it.

Third, The lower intake manifold can be ported quite easily to flow far better than the stock casting. I'd be very impressed if you could make a manifold out of bent tubing that could bolt in and flow better with less than 50 hours of time spent on it. The runner length on the intermediate intake manifold are of proper lenght to make power from 2K up to 10K in N/A form. The intake dynamics of the rotary are quite different than those of a piston engine. You also don't speak as someone with a firm grasp on fluid dynamics. Increasing the diameter of the intake runner reduces the intake velocity and reduces the natural supercharging effect of the port charge velocity. (while the valve is closed there's enough air in the runner to push on the side of the rotor and actually force air into the next intake chamber) Reducing this has been proven to reduce horsepower. The S5 intake manifold is a perfect example of this. Street ported motors actually perform better with the S4 manifold.

Fourth, Changing the intake plenum to a square box will hurt flow. If you want to make a single chamber plenum, by all means go for it. (I'm in the process of designing one myself) But, don't make it a giant box like the honduh guys. Make it out of 5-6" round tubing and make smooth transitions to the runners. You'll also want to convert to a single butterfly throttle body when you do this to maximize the gains seen from such a change in design.

Fifth, Relocating the injectors higher in the intake runners will most likey cause pooling of the fuel as it settles on the runner walls at low revs if you go ahead and increase the runner diameter. Keep in mind that the 7's use a side firing injector spray pattern. (much like that of a ceiling mounted fire extinguisher nozzle) So locating them in "direct firing" orientation will actually cause them to spray the walls of the runner rather than shoot more fuel directly into the port. Someone had posted a very popular thread about putting the secondary injectors in the 6-port actuator rod holes for an attempt at this concept. What he ended up with is a good way to eliminate any possibility of atomization from those injectors.

I'd keep going but I have a doctors appt. I'll continue this later.

Jimmy325i

Reducing the primary intake runners to .75" tubing will cause more restriction than any single point in the original casting.

I'm not saying all this stuff to flame you or try and make myself look smarter than you. I just want to save you a great deal of hastle and headache for a design which is inherently flawed.

If you want to try different runner lengths, make a 90 degree bend manifold which mates up to a flat flange at some height high enough to clear the top of the engine and low enough to clear the hood in which you can make prototype plenums and runners bolt up to. Understand what I'm saying here? Make an adaptor that'll fit the staggerd ports of the lower intake manifold and house the secondary injectors and oil injectors. This will leave you with an easily mated flange to fit new designs to.

I'm pretty new to the theory behind tuning intakes as well, but what you want to do is make the runner small enough to keep the intake velocity at half the speed of sound, but make it large enough so that all the air the engine will need can get through without being a restriction. It's a balancing act. You also want to have the runners long enough so that you keep the natural supercharging effect in place. It's been proven to be worth 5 free horsepower.

Hope all of this helps.

OC_

i thought the shorter you make the runners, the higher the rpm where the "natural supercharging" takes place. so you would want to have short runners for a high rpm application. Thats why the NA engines have the VDI setup, so they can switch to shorter runners for the big rpms. I would really like to see a diagram of how the stock intake manifold is. I admit, im not professional either. but iv always wanted to mess around with this. How do you solve for plenum size, runner length and volume?

Jimmy325i

VDI actually opens the passeges between the runners so the back wave (pressure pulse produced when the port is closed) can increase the pressure on the other rotor which has its port open. Shorter runners in general are ONLY good for the top end because they don't provide the additional characteristics lower in the rpm range. Turbo'd cars don't need the longer runners either because they make up for lost dynamics with boost. All the carb's manifolds I've seen also fail to provide sufficient runner length to utilize this free power.

I'm working with a professor on my revised plenum ideas and haven't gotten to that point yet. We're still working on making a new casting of a single chamber plenum based off modifying the stock unit. I just had knee surgery so I haven't been on campus in a couple weeks. I'll be posting my findings when I come up with something worthy of sharing.

OC_

"all the carb's manifolds" ?

are you designing one for a carburetor?

I dont think id ever convert to carb...

You know, you can easly make a plenum and runners out of fiberglass or carbon fiber, and simply bond them to an endplate that can bolt onto the engine. It would really be easy to make internal velosity stacks too.

OC_

i always thought about making a NA race engine thats pure rpm goodness. Somthing like a F.I. peripheral port engine sounds like a great track setup....

Jimmy325i

I'm not designing a carb setup. Simply threw that in there for compairison sake.

The problem with track engines is that they only have to run well at WOT. Anything less than that is for getting it to the starting line and onto the scales.

I've also been curious about the combo port engines I've heard of where they use a small PP along with the standard intake ports. If you could run some kind of actuation mechanism like the 6-ports use to bring those online and off again. You'd have a motor that would run from 2K till it blew itself to pieces from exceeding the limitations of the rotating assembly. If you used a 2 piece E-shaft and center bearing, you could potentially see power to 15K.

OC_

i was just reading about the PP combo port setup. i guess they call it a "mild PP". From what i hear, there hasnt been much sucess doing this, but i dont know how people are even doing it since theres so little info on it. I guess you could make it so that theres a whole different throttle body, plenum and runners for the PP ports and only have that come on once a certain rpm is reached. It might even be wise to close off the other ports since they might become so inefficent. maybe an iris type valve could be used on the PP? Also, the size of the PP doesnt have to be super 'race' huge, a smaller PP might be better for the street.... we should do this

Jimmy325i

Some kind of butterfly valve would be sufficient and simple enough to implement in the PP intake runners. It would leave you multiple paths to go with routing the intake and actuating them. The problem I've seen with all these mild PP setups is that they still try to use the stock lower and intermediate intake manifolds. This would be a perfect application for something custom which would allow the use of another runner to pass through the area of the primary and secondary runners.

You'd need to keep the intake charge coming from the same source as the primary and secondary ports because of the difficulty of managing fuel of another setup.

I just thought of a rather complicated means to implement such a dual purpose engine. Use single barrel carbs on the PP's and run the stock fuel system on the side ports. Have an rpm activated switch bring the carbs online when the revs reached beyond the capacity of the side ports. The CAS would still fire the ignition, but cut the fuel computer off and run it old school from that point up. There would be more than enough flow to allow proper metering and the carbs would be more easily tuned in such a layout.

I'm game to build it if someone else wants to finance the project. hahahaha