White_FC

Well just treat the secondary and aux as one duration and 8kRPM is where i'd idealy want it tuned for...



I havn't completly decided on a port style just yet, so I don't know the exact duration.... I dont want it closing much later but i'll be having it much earlier opening with the bridge though.



What are you using to work this out with mazdaspeed7? is this from the excel spreadsheet you were talking about earllier in this thread?

Drago86

Shorter the runner= higher the rpm its tunned for



More port duration = longer runer required to tune for the same rpm (compared to ports with shorter duration)



both of these are established principles, and shouldnt be disputed.



Its commen sense, port opens earlier, pressure wave is created earlier, so it needs a longer runner to arrive at the same time as a port with a shorter duration.



also i'd like to refer you to this page http://personal.riverusers.com/~yawpower/dectech.html which proves that j-ports open earlier then mazda factory P-ports, also the 6-port timmings on that page are only valid for 1st generation 6-port 13b's, the proper timming can be seen here http://www.rotaryengineillustrated.com/RE1...4-ports101.html which is 80 ATDC, which once again closes latter then a PP.



And to prove it all id like to refer you too this page: http://www.mymazdarotary.com/mazda_rotary_..._paper_html.htm

Where it shows the r26b's intake length and the rpm its tunned for. Note that the +175 would be 175+175(the non moving section of the intake) or 350mm, which is 27.4 inches, which is considerably longer then the stock S4 intake, but tunned to the same rpm, of 6500(its also probably worse then that because the r26b is most likly using a lower R value) alos note that changing the length of the intake results in a higher rpm tune, so



an aux bridge would need an intake runner that is considerably longer then the stock manifold, unless of course you were trying to tune for 30,000+ rpm

Drago86

Also if you just take the equation and work it out youd see that

more duration = longer runners, and more rpm = shorter( in relation to the runner, so aux runners would still end up longer then stock runner because of the huge increase in duration)





also mazdaspeed does your spreadsheet take runner diameter into account?, aswell as port runner length?

Drago86

Also i made a mistake in the previous post, the runner length with trumpets extended is greater then 27.4 inches because i forgot to add in the runner that the statonary part of the dynamic intake bolted too, this adds probably 4+ inches, so ~31.4 inches, which further emphisiszes my point.

White_FC

Drago86, J-ports are totally different to an aux bridge port though with regard to port timing......



Just wondering how you measured the S4 (i assume n/a?) intake? and what value did you come out with for it?



Not that I want to sound like an *** or anything, but 350mm definatly does NOT equal 27.1inches... in fact, it's not even close to that..

It's alot closer to 13.7795276 inches actually



So... a 13.8in long runner for a port with much longer duration than an aux bridge port or any sort of bridgeport short of a monster-port/j-port...



Now thats interesting, thats 13.8in for 'only' 6500rpm or whatever mazda designed it for for the r26b, so going by all the design principals, i'd want one much shorter than 13.8inches with my aux/secondary bridge port motor with a redline of 8k?

mazdaspeed7

How many times do we have to tell you that a an aux bridge, or most bridge ports for that matter have more port timign than the lemans 4 rotor????



For any sort of bridge or PP, the port opens as soon as the apex seal passes it. And a BP closes then the side seal passes over the top edge of the port, while a PP closes whent he apex seal passed over the top of the port.

White_FC

How many times do we have to tell you that a an aux bridge, or most bridge ports for that matter have more port timign than the lemans 4 rotor????



For any sort of bridge or PP, the port opens as soon as the apex seal passes it. And a BP closes then the side seal passes over the top edge of the port, while a PP closes whent he apex seal passed over the top of the port. [/quote]

Dude, your gonna have to tell me an aweful lot of times that your aux bridge motor has more port timming than a PP, a monster port or j-port or whatever, yeah i'll believe that, but I don't believe an aux bridge would, or even most 'normal' BP's.....



But hey if you say so Mazdaspeed7, i'll believe you.



So how long would an optimum manifold for a 'normal' BP or even a MFR PP, be for a redline of 7,500rpm by your calcs Mazdaspeed7?

mazdaspeed7

You agree that the aux port closes much later than a PP, or bridge, or ANY port for that matter, correct? Then why is it so hard to see that if it opens at the same time, its goign to have a longer duration? Let me dig up my formula, Ill put the numbers up in a few minutes.

mazdaspeed7

i cant find the formula I used, and im goign to bed. If I have time tomorrow, Ill post it.

Drago86

hmm,.. i did kinda mess up the measurement, but it doent matter because the r26b is tunned for a lower R value anyhow, hence why it ends up shorter( i think its 2 whereas the stock manifold is 4?) L= ( (1080-(EPD - Z)) X 650 / (RPM X RV) -1/2 D



epd= port duration



rpm=rpm



rv= refractive value



D= runner diameter(only significant because the pulse is reflected half the

diameter of the runner, from the end of the runner, if that makes any sense)



Z= how many degrees before the port closes you want the pressure wave to arrive , 25-30ish is a good starting point



1080= duration of a full rotor faces cycle



650= and average calculation for the speed of sound in some units(i forget which) if you wan to find a runner length at a specific humidity/temp kock yourself out, just seaxh for the piston version, which is on a number of sites and shows how to get this





also with this equaton, dont forget to add in the runner length inside the port runners



mess with the equation, it will prove everything MS7 is saying



also we allready proved that a STOCK aux port closes latter then a P-port, and thats before porting