In reply to Pete. (l33t FS) :
the RE ports are just big so I guess there isn't much room left to grow them, just comparing that streetport to a stock t2 port just dwarfs them.
observe:
In reply to Pete. (l33t FS) :
the RE ports are just big so I guess there isn't much room left to grow them, just comparing that streetport to a stock t2 port just dwarfs them.
observe:
fidelity101 (Forum Supporter) said:In reply to Pete. (l33t FS) :
the RE ports are just big so I guess there isn't much room left to grow them, just comparing that streetport to a stock t2 port just dwarfs them.
observe:
Having just done some reading on this topic, the reason REW irons are more desirable than RE irons is that the stock manifold is less restrictive due to the way it bends.
This means that despite the massive ports on the Cosmo RE, they flow more poorly in applications that use the stock manifolds. Obviously this isn't a problem with a custom manifold though.
I like your car by the way, I've been reading this thread for a long time but only recently made an account here. I always find all-out NA builds fascinating.
Pete. (l33t FS) said:...Judge Ito...
Where's that Obi-wan meme when I need it.
I try not to use drag engines as a point of reference. They make stupid power through all sorts of tricks but they just don't have to run for long. I remember an article in some import magazine probably 20 years ago talking about drag Civic that was making more than 300 hp with a D-series block and head. Awesome, no doubt, but I've yet to see any street or even track-driven cars with D16 engines making that much power.
Logan's RE build was my motivation. The fact that engine made 230 whp with so little modification (e.g. still ran the stock RE intake) showed me there was some promise in a dedicated N/A build. I seem to recall him mentioning scalloped rotors, though. I'm running one iteration of his "race" street port. Best I can tell it brought my 13BT ports to RE or REW size but I've never had them sitting beside each other to confirm for sure or compare timing. His porting was small on that RE engine but compared to what's possible on an older 13BT it's big. My favorite anecdote is we knew we were at the limit because we broke into the water jacket on the first front iron. I'm always half-heartedly looking for a set of RE irons for this reason. It's the only way to get a larger street port than what I have today. The REW would get me most of the way but since I'm not planning on building an engine any time soon I can be picky. Can't say I've seen any RE parts in the while though...
Logan did certainly not use the stock RE intake. He shortened the LIM by quite a lot.
RE/REW ports look larger than they are because you are seeing a diagonal cross section.
In reply to infernosg :
I made this very point on my instagram. Look at the center iron port on a current renesis, now compare that to a S4/S5 center iron port, its HUGE by comparison. Then add the streetport template from the FC overlaying on the renesis port and is really only extending the renesis port maybe 4mm. Mazda ported everything themselves with different castings as their intake manifold/EFI tech grew but you put the large/race streetport over the S4/S5 iron and it looks like a massive port.
In reply to Pete. (l33t FS) :
this is also my fear, that my runners are far too long (intake and exhaust) that all this extra work isn't for much of anything because I won't rev it to the moon. potentially but the car drives really well for rally this way, far more broad than overly peaky.
In reply to fidelity101 (Forum Supporter) :
Things happen in somewhat unpredictable ways. My bridge port with Holley manifold has a torque peak at 3500 or so. My S4 N/A manifold on a half bridge screamed past 9k.
I think good shape and CSA is more important than lengths. Length would be a last nine-tenths thing to worry about.
In reply to Pete. (l33t FS) :
You're right. I totally forgot about the modified LIM and was just picturing the cone filter bolted to the stock RE throttle body on a largely stock UIM.
In reply to fidelity101 (Forum Supporter) :
If I had the resources I'd like to just stack 13BT, RE, REW and MSP irons next to each other for comparison. I'd be tempted to use whatever plates have the largest ports as the base for a non-bridge/peripheral port N/A build. A 13B/RE/REW-MSP hybrid could yield interesting results. I know it's been done but not on an N/A build to my knowledge and I've never seen the results. Now I'm thinking about a hybrid 13B-MSP with a semi-peripheral port intake...
My experience is intake length is MUCH more important than exhaust. Provided the exhaust is well-designed (equal-length, smooth bends, good collection and expansion) you're really only chasing that last few hp like Pete says. Again, my anecdote is I halved my intake runner length and went from dual 55 mm straight bore TBs to dual 55 mm tapered bore TBs and went from 190 whp to 240 whp. Granted it was on different dynos but the all important butt dyno definitely noticed the difference.
In reply to Pete. (l33t FS) :
CSA?
In reply to fidelity101 (Forum Supporter) :
Cross sectional area.
I have a feeling the tapered throttle bodies made more of a difference than the runner length. The (in)famous Laird intake manifolds that the Aussie IPRA racers hold in high regard are remarkably long for engines that allegedly run up in the 11k-12k range, but they are tapered, have a beautiful shape, and the throttles are part of the overall manifold and not generic bolt on solutions. They make crazy power for engines where no part of the intake port may pass through the peripheral housing, meaning they are unrelieved bridge ports. Well into and past MFR p-port territory, and these are road racing engines not 8 seconds and shutdown drag engines.
I forget the exact numbers, because it was a long time ago in a galaxy far away, but a runner with a taper (2 degree? 7 degree?) flows a lot more than a straight pipe with the same outlet CSA because it isn't fighting the boundary layer all the way down. This also affects the effective runner length because of the velocity change, but I forget if the taper makes the runner act like a shorter or longer straight pipe.
WondrousBread said:fidelity101 (Forum Supporter) said:In reply to Pete. (l33t FS) :
the RE ports are just big so I guess there isn't much room left to grow them, just comparing that streetport to a stock t2 port just dwarfs them.
observe:
Having just done some reading on this topic, the reason REW irons are more desirable than RE irons is that the stock manifold is less restrictive due to the way it bends.
This means that despite the massive ports on the Cosmo RE, they flow more poorly in applications that use the stock manifolds. Obviously this isn't a problem with a custom manifold though.
I like your car by the way, I've been reading this thread for a long time but only recently made an account here. I always find all-out NA builds fascinating.
Appreciate it! I need to go back through and re-host some images this build spans so far that most sites have come up and gone under since its inception lol but I managed to save most of the photos/context on an external hard drive but I'm just so lazy and that takes a lot of effort haha.
engine is assembled!
however it has not passed the 24hr cooling system leak test, played wack a mole with a few drain plugs/ports but then noticed a prior repair unearthed a pinhole leak:
the irons and rotor housings are all re-used in this build, actually so is the bulk of the rotating assembly and stat gears.
I'm a big fan of frankwankels but sometimes stuff like this happens. Off to drag this block to my friends shop so he can TIG it or I will partly disassemble the motor and handle it from there. Really trying not to JB weld it right away but I have had plenty of JB weld on my intake manifolds the past 10 years so we shall see...
While I wait for his availability I will set/check the endplay of the motor and have that ready to go.
nope - no good. weld still keeps having pinhole, cant get the cast iron hot enough while the motor is together because the aluminum rotor housings is acting as a giant heat sink and sucking the heat away.
Looks like I need to tear it down and start over with a different rear iron. Luckily (I guess) I have the old motor which could have some salvageable irons from it but this delays my car's 'first start' date and most definitely makes me miss ice racing season. Which sucks because its a crapshoot if we ever have any. I will still need to port match and likely resurface the rear one but I can't open the old motor yet because I need to use the current motor that's in the car for mockup of the new intake. I have had delays with my fabricator friend on that part which has stalled a lot of this.
The plan was to build a motor in parallel out of the available spare parts I had then have then have the intake fabricated and tested on the old motor and then do a big swaparoo when ready and start the new motor on the new intake, begin break in and enjoy. Now I am left with 2 non functioning engines and missed my window of holiday time off to fix this.
TBD on whenever this will get resolved now, just waiting on my intake to proceed so I can pull the motor and tear that one down.
okay well... after much consideration and given my "announcement" on the rx8 for a future 3 rotor build. This motor will be the 2 rotor parts of the 3 rotor so when I decide to upgrade to the 'big block' the cost hit wont be as bad since I will already have the bulk of the motor ready. This 'best of my spares' build is not necessary anymore since I wasn't able to have the block crack free and opening the other block up to resurface items and yadda yadda, I would rather put that towards the end goal than kicking that further down the road. everything else is business as usual so meanwhile I play the waiting game.
okay project no longer on pause time to get crackin'
Cosmo 13B motor on the left (stock ports), turbo 2 motor on the right (ported)
now the actual ports isn't going to be a huge change but because the casting insert to make this port is so much larger it saves me a lot of grinding time and reduce the opportunity for me to poke through.
but when you look at what I'm going to port its not much larger than what is stock currently:
its the same template I have been using on my prior motors but the path of air to this point is far more free flowing, center iron will be a mix of renesis streetport and large streetport
this is actually really interesting video series (3 parts) and has lots of good content
it shows how the ports changed through the years and variety of port styles, flow data and how to flow it (which i had theorized would look something like this) instead of incremental valve lift it would be the degrees of BDC/TDC.
also interesting that because of the extra 90 degrees of duration these motors have very little overlap compared to a piston engine.
Adding duration does not decrease overlap.
A lot of piston engines have negative overlap, even before VVT. Either way it is great if you want a rock solid idle and sacrifice a lot of low end and midrange torque.
In reply to Pete. (l33t FS) :
i told you I struggle with camshaft stuff - it does translate into rotary problems for me. godbless there are templates.
Fascinating videos. I feel vindicated regarding my decision to use S4 turbo plates. I wish I could say I knew what I was doing when I made that decision but it was more guessing and dumb luck. It's neat to see him conclude mildly ported S4 plates could support 300 hp. That's in line with what I'm seeing with my 240-260 hp at the wheels. On the other hand it does mean I may have tapped out my current configuration. Things like further optimizing intake and exhaust, higher compression, etc. would likely provide small gains over what I have now. Just further reinforcing my decision to not go running off and dumping money in those efforts until I need to.
One of the cars I wish I imported when they were cheap was a cosmos with a 20b.. back in the day I saw a few go through auction around 8-10k. The other one is an FD RX7, back when they were similarly cheap.
Anyways! Nice thread, informative and great pictures.
In reply to infernosg :
yeah which means on my cosmo route I will have a huge drop in velocity so its going to make the engine spin more to make peak power higher. should be interesting. right now I am awaiting on some printed parts via help of NONACK for the CAD design work and then the manifold construction can begin.
In reply to fidelity101 :
Yeah, at this point I'm convinced I'm going to stay with the S4 turbo plates until they're unusable. Obviously it's not a direct comparison since mine are ported but the stock S4 turbo plates seem to have a very good balance of flow and intake velocity. With the data presented it's clear why they make good power AND torque (for a rotary). The videos do call out some less-than-ideal geometry but I'm convinced that's a result of Mazda working within the available castings. I have first hand experience trying to open up the backside radius only to end up breaking into the water cavity.
its all coming together now... and the engine cooling system held 19Psi for the whole sno*drift weekend so we are back on track.
proof of finished motor:
oh yes, it will be a busy weekend.
That's awesome! Do want!
okay so it wasn't THAT weekend but had some misc/random delays and such but back on the tracks for the most part.
good start
uhh too much mad max. 
it sticks about 8" out of the hood so this won't do as much as this is really awesome.
the middle straight pipes are coming out which means I need to take double that distance out of the exhaust which I have plenty of room to remove and that way i can keep my primaries "matched"
The intake primaries are half the length of the exhaust primaries but the exhaust runners are too long in general and the manifold itself is difficult to install so that is going to get re-worked a bit too and then the filter should only stick out of the hood 2-3" which is much easier to cowl.
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