peejay

People read Felix Miata's FAQ on porting and assume that BP's or PP's are no good for the street or for turbocharging.

HWO

anyone who tries to run a bridge port on the factory ECU weather it be turbo'd or n/a deserves all they get, a bridge port requires VERY different fuel maps and VERY different ignition timing than a stock port motor which is what the ecu's are designed to run

HWO

maybe we should link to the write up on crispeed's car which is making 608rwhp at 32psi using an engine wtih BRIDGE PORTed secondary ports...........

fuzzi

Another thing you guys are leaving out in regards to the 10,000 rpm thing..When you get to about 10,000 or a little less... your eccentric shaft begins to flex quite a bit, which can cause you to but up an apec seal.... In order to get your street car past 10,000 you will have to get some sort of custom one made...although it is entirely possible...

soul assassin

well i was in a shitty mood till i seen this! this is hilarious ! 14lbs of boost on a t51? you surely have no clue what the hell you are talking about!
well to set the record straight take it for what it is worth
1. a bridgeport is fully streetable
2. i am running a to4R with a 1.15 a/r
3 10k is possible but i shift at 9k
4. currently making 520rwhp at 20 psi at 6k soon to be about 600 when i run 30 this spring
5. a bridge motor does not cost 5k maybe 600-800 more than a regular motor depneds how freaky you want to get with it
6 i drive my car everyday to and from work in about 6 inches of snow right now!
7 you WILL make twice as much torque then a sideported motor
8 no problems with over heating
9 loudness depends on your exhaust sytem i have removeable silencers for everyday cruising
i completly agre with HWO views on this subject

bcty

i have seen at a few placs for chips claims to add 25% more horsepower 25% more torque and increase the redline to 9500... only with a chip... so.... i dunoo....

MikeL

Hey soul assassin, I just bought a bridge ported engine. I have your soulbridgeidle.wmv file. I hope mine idles like and, maybe even runs like yours! I'll let you know.

What is your "warmed-up" idle speed?

Mike

Kurgan

MikeL:

so, you gonna be running a t-66 full bridge engine? you getting RP to tune it for you? I hear that a bridge is a bitch to tune.... but I've never done it, so who knows.

No7Yet

...then you're more hardcore than I am...

he won't be running a turbo

he won't be running a turbo, and therefore will most likely be shifting at all of 10k-ish. How long do you think an engine continually shifted at 10k will last? ...and don't say "He'll *****-foot it around town." A ported 13B at full scream at 10k is ******* AWESOME. He'll want to show it off ALL THE TIME. Unless he's got WAY more restraint than I've got

he won't be running a turbo

you're in Japan. what are "extreme" engine mods here are 'commonplace' there (e.g. bridgeporting). A well-built bridgeported engine will require the use of NEW rotor housings, rotors, hardened stationary gears, probably new (though perhaps lapped) side housings, modified e-shaft oiling and oil injection system (unless he goes premix). Not to mention the extensive rotor and e-shaft balancing and hardening required for 10k RPM operation. Carbon apex seals are required as well. He probably won't be installing it himself. I stand by my $5k estimate, and that's low, IMO.

...then you're more hardcore than I am...

yeah, at 7000 RPM! What do you estimate his torque numbers to be at 2800 RPM? 3500 RPM? Where he'll be used to doing all his street driving? He'll have to tach around 4k to make useable power, and thus, his gas mileage will suffer. Hell, I tach about 2.8k in my STOCK 89 TII. Like I've said before, prehaps I'm just a sucker for torque.

and I'll bet you ballocks to a barnyard you're not running anywhere close to a stock-size radiator. Anyway, mea culpa - a std. bridgeport doesn't cut into the water jacket, so okay, I stand corrected.

he won't be running a turbo. and I'll bet your removable silencers are like those sold by Apex'i - good for a dyno-proven 75 hp loss (damnit, now I'm going to have to bug Jay in Pensacola for dyno charts... just take my word for it, okay? ). And anyway, how loud is "streetable" anyway? I consider my stock 89 TII to be pretty loud for everyday driving, esp as compared to my Camry.

Comments? I'm not too arrogant to admit that I know next-to-nothing about turbos or their effects on a highly-ported engine - but it's a moot point, since he won't be running a turbo. I'd like to see some port numbers for your engine, Soul; specifically, port duration numbers. I'm always willing to learn...

Brandon

RETed

The term "bridgeport" can mean a lot of things.&nbsp I've seen everything from a "half-bridge" to a monster "J-port" called a "bridgeport".&nbsp Very small bridgeports could easily last a long time, but larger bridgeports drop engine life (cracked bridge) dramatically.

SPZ510 mentioned "Todd" at Motorsports Dynamics; although Todd doesn't work for MD anymore, I know his RX-3 pretty intimately when I used to life up in Sac.&nbsp If it wasn't for this car, I would probably still be calling a BP motor "unstreetable"!&nbsp I won't drop all of this BP RX-3 secrets (anyone who has ran into this car can ask the owner himself), but it does run a pretty sizable bridgeport and regularly sees 9,500RPM; the car does run consistent 13.0-13.1 @ 105 (Sac Raceway) and has put down an honest 220-230hp to the rear wheels (on a DynoJet).&nbsp The thing that scares me is that the car is VERY QUIET and VERY STREETABLE.

Now, as for turbo'd 13B's running bridgeports, this is something I don't recommend for most street cars.&nbsp Overlap kills (low-end) power, and most street cars don't (stay) rev'd high enough to take advantage of the increased overlap.&nbsp Soul Assassin is justified cause he lives in Japan - the Japanese bridge EVERYTHING!

Personally, I don't listen to anything that HWO says, cause a lot of his posts are regurgitated from stuff other people; I haven't seen proof he has done any of the work himself.&nbsp HWO, you should listen to yourself..."by having large overlap and pulling LOTS of RPM to get the 'natural' supercharging effect going" - WHAT natural SC effect?&nbsp The only SC effect I know of is early closing of the intake, which is also known as the Miller cycle; increased overlap is totally opposite, as you end up blowing the incoming intake charge back into the exhaust - or are you implying that the exhaust blow-by your increased intake "pressure"?



-Ted

No7Yet

Ted, I'm not too familiar with the Miller Cycle. I know it differs from the Otto cycle in that its "phase durations" are not of equal time - it would seem that the rotary would be conducive to a Miller Cycle-type design, due to the fact that the durations of the various phases can be altered much more than is possible in a reciprocating piston engine. Do you have any good links to Miller Cycle Engine info or thoughts about what a "Miller Cycle rotary" would consist of?

Brandon

RETed

I don't remember all the details, but the gist of it is that the engine closes the intake a tad earlier than normal, which allows the intake charge to pressurerise slightly in the intake tract before being allowing into the combustion chambers.&nbsp A supercharger is used to heighten the effect - Mazda has gotten 10%-15% more power doing this with their Millenia S models.&nbsp With the release of the Millenia S, there were wild rumours that a Miller Cycle rotary was in the works; Mazda has not confirmed nor denied these rumours - it would make for a very nice running rotary!



-Ted

MikeL

Me???? I'm just looking for more port than previous.

Kurgan, I haven't seen the inside of the engine but, I soon will. I bought it from someone that I don't know so, my local engine builder is gonna take it apart.

It will be used with my T-66. The only change from my current setup(376 rwhp) is the port and a 17lb steel flywheel. I can't afford a BB CHRA right now. That will come in a month or two.

I figure this:

I was pretty happy with the lag before, with a street port and no BB turbo.

-The lighter flywheel will help the lag on the street.

-When I can get it, the BB turbo will help even more with the lag.

Here's a video of me punching it at about 25 mph in 2nd gear. It takes about 7 seconds to hit about 100. I think I'll be quicker with the bridge, flywheel and BB turbo.

http://brfoundation.com/RX-7/video/MikeL5.mpeg

Wankel7

Where is Soul Assasian. I thought he had a Bridgeport. That car is nice

James

soul assassin

damn you guys always go nuts while i am sleeping! lol! ok lets get back to the topic
my warmed up idle is about 1500-1700 bounce since i have no cold start my cold idle is a 5lb sledge on my gas pedal! lol (i'm not kidding either)

ok well here are some hardcore numbers from my last dyno run
peak torque at 6297 rpms
peak hp at 6767rpm
now granted i don't make much power below 4k but why do you need 500hp at anyhing below 4k? hell i don't even launch at the track that low
if you need 500 hp or even 300 hp below 4 k for crusing in traffic and stop and go driving i think you are retarded, if you want to play around race do what ever it is you do all of it will be done most likely above 4k after 4k it skyrockets straight up
just get over it and accept that a bridgeport is streetable!

peejay

Argh... I couldn't quote you.... so I'll have to go over some stuff manually

You only need carbon seals if you want to go over 8500. Since a well done bridge or peripheral port can and will increase torque over a BRAD RPM curve (I've seen a shart floating around here that shows marked improvements in VE at everything over 2000, and that's just where the chart began) then if you tune the ports for the midrange you will still get great improvements without needing to rev over 8500. (Mazdatrix's drag 20B has bridge ports and an ~8500rpm max because of 1-pc steel apex seals)

All NSU production engines were peripheral port. They were tuned for midrange power. An NSU 10A-sized engine was making 120hp at 5500rpm, when at the same time a side-ported Mazda 12A made 100hp at 7000. The peripheral/bridge port is a MUCH more efficient port. The problem is that "traditional" peripheral/bridge engines made out of Mazda parts are tuned strictly for high-end power. Well you can do that with a side port too... you can make a side port that doesn't begin to make power until the tach needle twists off. (It still won't be as efficient as a bridge though)

Bridge/peripheral engines have 1 disadvantage... poor efficiency/economy at low load. That's a tradeoff that many people are willing to take. I used to drive a lumpy idled 429 that didn't like to run below 2k... I'd get anywhere from 2-10mpg in the city. (Out on the hgihway where it could get into its powerband it'd get 23 or so MPG) Other people I knew at the time had wilder combinations and drove them daily as well. Just because one particular person's idea of "streetable" means things like smooth, low idle and super-high MPG doesn't mean that's everyone's idea. Personally smooth low idles annoy the crap out of me, it sounds like some sort of granny car

HWO

the velocity of the intake air keeps going 'forward' even when the rotor/piston is past TDC and starting the compression phase, this is how you achieve over 100% VE, only once the intake ports are closed does intake air stop going into the chamber, this is achieved easier on a rotary than on a pistom engine

peejay

sweet

as a point of reference my last street port had a cold idle of 1900-2100 bouncing (brap brap brap) and a hot idle with all accessories off it'd idle between 900 and 1100 bouncing slowly, turn accessories like lights and the electric fan on it'd idle down to as low as 700. I usually held the idle up to about 1500 at stoplights. it also made good torque at all RPM, lots more than stock, but the real meat of the powerband didn't start until 5500, and it felt like a turbo spooling up. (This being a non turbo car)

qwck10th

Hey, I've got this porting stuff figured out...

A bigger hole lets more gas and air in. Pulled-in ok, pushed-in even better. More gas and air makes a bigger bang (probably the loud sounds you guys were talking about). Bigger bang makes more power.
See, it's simple

Steve C.
Marietta, Georgia
>Carbide wins

peejay

Pulled in? What do you mean?

Air is always pushed in to the engine. At atmospheric it gets pushed in to the intake manifold at 14.7psi at sea level, under boost it gets pushed in at 14.7+boost pressure (10psi boost (psig, gauge pressure) is 24.7psi absolute (psia).

Once inside the manifold you get into things like resonance tuning effects, imagine the air pressure wave moving in the manifold is a big Slinky moving back and forth - if you can time it so the pressure is highest right before the intake port closes you can force even more air into the engine. That's where goodies like the way the intake manifold is shaped come in to play. Rotaries' secondary side is shaped like it is to actually use the closing of one intake port, which makes a big pressure wave Slinky-ing around, to force more air into the other rotor. Of course this can only be tuned for one specific RPM, but by changing the length we can change the RPM it happens at - this is where VDI comes in.

The port overlap period is more fun. With proper exhaust tuning you will end up with lower pressure on the exhaust side than at the intake side during the critical overlap period. (Same Slinky effect works on the exhaust side too!) The pressure in the intake manifold (remember there is no such thing as vacuum, just pressure below atmospheric) forces the exhaust gases out of the chamber for a more complete fill. Bridge and peripheral ports have a much nicer and better-shaped overlap period so this happens more readily (large street ports to a very small extent, too) which results in better chamber filling at whatever RPM you tune the resonances to occur.

Notice, whatever RPM you tune it for! People who just open the ports up as big as possible and put enormous-diameter short-runner exhausts on are going to only make decent torque at sky-high RPM. If you TUNE the SYSTEM for a lower RPM band, you're going to get shatteringly good results without having a "peaky undriveable" engine. Porting must be done intelligently and with the intended purpose in mind! Of course if you order a race peripheral or bridge port engine it's only going to make power at sky high RPM, because most builders will assume that it's a race engine that needs to make maximal power and forget the rest of the RPM band because the engine never goes that low.

RETed

This is only for boosted engines.&nbsp You're actually losing velocity in an NA engine due to the fact that you're allowing the intake charge to enter the combustion chamber in a much larger winder.&nbsp Remember, velocity is delta distance over delta time; you're increasing delta time so velocity decreases.


It depends on who you're talking to.&nbsp Changing duration and overlap is as "easy" as swapping out the camshaft(s) on a piston engine...



-Ted

peejay

You're only losing velocity if you open up the runners a huge amount! Only open up the parts that are a restriction and leave the rest alone, and get max velocity with minimum volume. Then you start making stupid-big power at decent RPM!

The window of the port isn't critical to velocity... it's more critical as it relates to opening and closing timing. Look at it this way, the airflow is going from high velocity in the runner to very low velocity/large volume when it actually gets in the chamber, you're going to want to make that as smooth a transition as possible so you need to open up the port window BESIDES the obvious benefits from increased port timing. With a good Bridge or a Peripheral the air has more of a straight shot into the runner versus the two or three right angles that the air must make with a stock port or even some badly done street ports.

BLUE TII

iTrader: (9)

On a list of Mazda rotary engines I did see they have a model designation for a Miller Cycle rotary! I have to learn to bookmark stuff more though :-(

BLUE TII

iTrader: (9)

Wow! I never thought I would say this, but Ted you are incorrect. The Miller Cycle engine DELAYS the closing of the intake valves further into the compression stroke and depends upon a strong S/C to provide compression and stop reversion. Typically Millers are 15% more efficient per displacement.

bcty

bump