Liquid like I said the stock Aux port timing helps with pressure waves ariving at the intake cycle of the other rotor. Thus doing a Aux bridge would totally kill this, therefore having the stock madifold would be a bad idea (take a look at it both the S4 and S5 intakes have LONG runners). You would want a different intake manifold, that would be shorter. Your best bet would be either a IDA or DOCE style carb manifold with Throttle bodys on it, and of course this would mean a standalone.

 

That's ok. I'll stick with my plans and work from there. Noone has posted any new information I was unaware of, so I will continue as I would have.

 

You know once and if you go standalone, try 3rd and 4th and it'll still be a half-bridge

 

I definitely would not use the S5 manifold for any bridgeport. The runners are far too long. The VDI effect will be minimal if not totally non existant with the port overlap of a bridgeport. The excessively long runners will also pose too much of a restriction. I have never seen any kind of VDI on any Mazda racecar. VDI is better suited for engines with very low to no port overlap between intake and exhaust. The S5 manifold is less effective on big streetport engines than the S4 manifold so it will only get worse if a small (or any) bridgeport is used. With extreme porting comes custom designed manifolds. Shorter, straighter runners need to be used. When you have high amounts of overlap (measured in timing duration not bridge length) you need an exhaust that not only scavenges very well (collected) but also an intake that is very free flowing. You can get away with using the S4 manifold on an aux bridgeport but the stock ecu and afm is going to be a big problem. It is more the restriction of the afm than anything else. It goes back to the overlap problem. If the engine has a hard time sucking in intake air due to restrictions then it will take anything it can get that is easy. Unfortunately this is a small amount of exhaust gas since the bridgeport causes port overlap with the exhaust. This will dillute and heat up the incoming air resulting in less power. At higher rpms incoming velocity 'outruns' this dillution effect but the better flowing the intake and exhaust the faster it will reach this point.

As a general bit of info on timing of bridgeports: ANY bridgeport, regardless of length or width, opens at the exact same point during the rotors rotation. Stare at a torn apart engine some time and check it out. This is also the exact same spot that all peripheral port engines open. However, and this is the key, the full port is not open at the exact same time. Basically translate this to camshaft lobe ramp speed on a piston engine. Think of a peripheral port as having a valve that is fully open the exact same instance that it started to open. Now compare this to how different size bridgeports open in relation to duration. They may start to open at the same time as a peripheral port but the entire port is not fully open until the rotor travels much farther. In other words a valve on a piston engine would open from start to fully open more gradually. A larger bridgeport simply has a greater 'ramp speed' (piston engine term) than a smaller one. On a 6 port engine while the aux port closing is around 70 degrees, similar or the same as some peripheral ports, and adding a bridge of any kind will make it open at the same time as a peripheral port, it will NOT have equal timing characteristics to a peripheral port. The peripheral ports just open and close to their entirety much more suddenly.

If you were to do any kind of bridgeport on an engine that is using a stock intake and stock exhaust manifold, you will LOSE power due to restrictions and complete lack of scavenging. Stock exhaust manifolds suck as anything other than a flower pot or paper weight.

 

Very well put rotarygod.

 

This is exactly the kind of discussion I need. I plan on doing something similar for my race car project (bp on aux ports only). But I will do full internals and stand alone so it will be safe up to 9 - 9.5K.
MS7 figured out those runner lengths yet?

 

...any engine w/ stock manifolds will lose power...

care to explan the guy on the teamf3s board w/ an aux-port and stock S5 UIM? he reported a night and day difference between that, and his stock S5 engine... for the better I might add.

 

A stock engine, exactly. My car is faster with 6 ports wired closed than it was with a stock motor and the ports wired open.

 

well do u even know what the stock ecu can handle up to? im using the stock ecu until i get a custom intake manifold. i dont see a need for a standalone, a afc and maybe bigger injectures will do for now until i get custom intake to make more power.

dont u agree that the NA stock ecu already runs rich? rich enough to port and add more fuel pushing the injectures harder?
im going to be doing this and i will show u guys that it can be done and make a good amount of power up to 8500rpm.

 

Go right ahead, but dont say I didnt warn you.

 

do u know what the stock ecu can handle up to? i would like to know, dont get me wrong ms7 i know u know ur ****, but i also know my friend knows alot too.

what can happen? i think jus leaning it out rite? but thats hard to do on an NA. tell me what you think.

 

First, I dont think anyone really knows what the hp limit of the stock ecu is. Second, you dont seem to understand how poorly this will run on a stock ecu withotu fuel correction. Basically, the airflow will be off the map on the stock ecu, and will run drastically lean. Im talking about lean to a point where the car will bog from idle to redline. Leaning out with a stock port or mild SP is hard. Leaning out when the port is WAY too much for the ecu is not.

Feel free to think your guesses are right, and people who have personal experience are wrong, but Ill be the first one to say I told you so.

 

<As a general bit of info on timing of bridgeports: ANY bridgeport, regardless of length or width, opens at the exact same point during the rotors rotation. Stare at a torn apart engine some time and check it out>

not exactly, look at the rotor as it is sweeping up at the end of the exaust stroke, moving the bridge or the p port higher will make it open latter.

<On a 6 port engine while the aux port closing is around 70 degrees>
86+ 6-port motors close at 80 degrees, pre 86 6-ports were 70

 

mazdaspeed7 what equation are you using to generate the ideal runner lengths? i'd very much like to know it.

 

 

The OPENING point for a port on the intake side is where the side of the rotor is in relation to the rotor housing. Since the rotor can not get any farther over it can not open any earlier. Remember the sides of the rotor don't just move around the outside they also move inward and outward in relation to the rotor housings. The closing point is the location where the apex seal crosses the port. This is exactly the opposite on the exhaust side of the engine. If we move a peripheral or a bridgeport up then we can hold it open longer but we can't open it any sooner. I take that back. If you move a peripheral port WAY up it will open later. The only way a bridgeport can open later than a peripheral port is if the eyebrow does not go all the way over to the rotor housing. That would be a very skinny port.

As for the 6 port timing issue. I know there are differences. Thats why I used the word "around" instead of typing out a book on the engine differences between year models.

 

Don't be too hard on M7. It is possible to know the basics as to when different length ports work better even though you may or may not know the actual formula. As a general rule: Runner lengths should optimally get shorter the more radical the port timing is. As a consequence the powerband will go up but also get narrower. Then again that is always understood when porting is undertaken. There now everyone knows when to use what. You've got to sacrifice somewhere to gain somewhere else, at least until technology gets a little farther along. How long should a particular intake runner be for which size port? Who truly can answer that without having their car on a dyno or their engine torn apart and on a flowbench. There are too many variables for anyone to answer that question perfectly. Ever consider that your powerband can shift slightly depending on temperature or altitude? Thinner air is less air and intakes are tuned on a ratio of how a certain amount of air travels through a certain area at a certain speed. Peak power is obtained when the air traveling through the runner is moving at a speed of .6 mach (430 mph give or take). Air moving faster than this will start to lose efficiency and therefore power will go back down. This number helps us to determine optimum intake runner diameter but has nothing to do with length. Length is based as I said earlier on several things. There is one basic formula but minor calculations can be used to revise it depending on use. Unfortunately I have a brain cramp and can't think of the formula off the top of my head. I'll get it later. Then you need to factor in plenum size if one is used or individual throttle plates. These affect tuning because of acoustic ramcharging effects. This is starting to get too complicated and I've already gone far beyond the topic of this thread.

 

I wasn't being sarcastic, I thought he had a specific formula or formulas to find the proper length.
Given that the ideal air velocity is 430mph, it seems you could use some version of the full bernouli energy equation. I'm an engineering student, so this stuff interests me.
It's just fluid mechanics, right?

 

so ms7, what intake mods besides the custom manifold, should i get? what kind of ecu(brand), what do i need to get to make the car not run so lean? im learning as we go on with this.i want to get different opions on this bp of the aux ports.

it sounds like you know what your talking about so tell me what i need to do for this to make it live for a while and have good power. i dont want it to run over 9rpm because thats to much money for all the inturnal parts.
do i need bigger injectures?

explain what u think i need to have in order to run this engine right.
thanx

 

I do have a formula, but it is based on some assumptions for a PP motor, and ill need to spend a little time reworking it for side ports(except BP, since its similar to a PP in port timing).

RX7raca, youre on a budget, so I would get a microtech LTX8 for the EMS. 4 550 cc injectors should be adequate, but the pulsewidth might get too high at high rpm's(above 8K). But I cant say for sure, thats just speculating. For the intake manifold, it depends on how much fabrication you can do, or are willing to pay to have done for you. A simple intake manifold could be done pretty easily, and use the stock TB, or a 2 x 58mm tb thats readily available for LT1's. Ill get back to you on runner lengths/diameter.

 

your rite about the budget, how easy is this microtech LTX8? can i do it myself or do u need some special tuner guy. by the way i have the s4 engine i didnt know if you knew that.

your being a good help ms7, i thank you and keep the info rolling! LOL

 

Im not the person to ask about the microtech, send No7yet a PM, or browse the microtech forum. From what Ive read, theyre very easy to tune, and the base maps are very good starting points. Get a DIY wideband kit($200 or so total), and you could get very close to peak power without a dyno, just tunign on the street.

 

Mazdaspeed7, expose your port design! You guys are making me foam at the mouth. Ah **** it. I will do my own and be the first to publicly show it around. Here it is so far (next attempt will not get into the oil track though).



Just a basic easy street port opening around the same time as the secondary but closing a bit later than stock, with a lot of bowl shaping. I am going to widen the runners a tad and match port the manifold.

 

Care to tell why the LTX-8 and not the LT-8? You think the price is warranted for different coils? That is the only difference in the LTX-8 and LT-8 after all... other than a couple hundred dollars.

 

I've been doing a few empirical calculations on this. I'm not going to post the full calculations until I have managed to format them nicely and have got a handle on a couple of issues wrt to flow requirements I am still wrestling with.

But the upshot is that, for a bridge port with about 430° duration tuned for 8k the tuned length needs to be around 20-22". Interstingly this is very close to the length needed for a street port primary to get a 6000 RPM peak (19-21"). The reason this is interesting is that, if you common the primaries (I'm approaching this from a custom inlet perspective) then you will get a 180° reflection from them at 3000 to give a nice torque boost as per the stock system.

As I am comfortable (actually happy) with cutting holes in the hood/bonnet for trumpets to poke out of this does open up the possiblilty of a IR setup for 6-ports with an aux bridge for not too much outlay. I would be using motorbike EFI throttles as they are cheap and light and about the right diameter. The real advantage of this over the stock setup is that the tuned length can be varied very quickly allowing you to home in on the best length for the power curve you want.

This is all peter (rice racing)'s fault. I was happy as I was until one of his posts planted the idea in my head that this might be workable. So everyone please make sure he doesn't post anything on how good a semi-PP can be or I'll be sleeping in the pit again :-).
Bill