NoPistons -Mazda Rx7 & Rx8 Rotary Forum

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-   Rotary Engine Building, Porting & Swaps (https://www.nopistons.com/rotary-engine-building-porting-swaps-55/)
-   -   How to do a full 4 port bridge w/ wide powerband and a lil streetable (https://www.nopistons.com/rotary-engine-building-porting-swaps-55/how-do-full-4-port-bridge-w-wide-powerband-lil-streetable-57183/)

Node 02-11-2006 11:58 PM

Looking for widest powerband and strong all around w/ that brap and crazy topend



Was wondering how you would place the eyelids and do the other ports inteh first place.

Would like to use a 4 port turbo motor w/ diff rotors. Full bridgeport



Not sure of how diff the idle and low-end is between half bridge or a full bridge.

Maybe a secondary bridgeport? I don't know of anything to compare

But that seems like it would only work with the stock 3 barrel throttlebodies or a very very complex custom setup.

Would any of the turbo intake manifold and tb setups be suitable for a bridge? maybe FD or BT?



Something with similar to a streetport lowend and just some real nice topend. I've been told and read that bridgeports are streetable if you know how to size them accordingly and have more all around hp but the huge spike makes it not seem like it.





Maybe some nice dyno charts?



I'm just thinking of ideas for a project car.





Thanks,

Ben Martin https://www.nopistons.com/forums/pub...1047683473.gif

j9fd3s 02-12-2006 11:01 AM

i tole a ju, the bridge i drove (full 3 finger bp in to the water jacket, 9.7 rotors, 750 holley, uncollected 2x2.5" exhaust) had more power from 2000 rpm up than my gsl-se. if anything the bridge welt weak up top, it did put down around 230@9600 when the dyno stops reading rpms.

13BTNOS 02-13-2006 03:52 PM

13BT 4 port plates full bridge port with S5 9.7CR rotor assembly. Running a Racing Beat Holley 650cfm double pumper. The plate on the left is the front intermediate and the one on the right is the center intermediate. The ports are about as large as you can go with the sideseals still being supported. And the bridge ports are to the edge of the waterseal withe the water seals still in tact. Hope to see over 200rwhp that should move a Datsun 1200 that weighs under 1700lbs pretty good.

rotarygod 02-15-2006 02:38 AM


Originally Posted by j9fd3s' post='801183' date='Feb 12 2006, 11:01 AM
...uncollected 2x2.5" exhaust... if anything the bridge welt weak up top...



I believe that. A high overlap engine absolutely needs acollected exhaust to get the most out of it, especially on the top end. With an uncollected exhaust (and an overly large one at that), I fully believe it would feel weak up top. Put a nice collected system on that car and hold on.

ArmyOfOne 02-15-2006 07:03 AM

How thick is that edge between the BP and the water seal groove? It has been my experience that anything under 1mm will break off within the first 1k miles. This will in turn expose the water seal to the incoming gas and get ripped up by the sharp edge of the apex seal eventually leading to coolant seal failure. You may want to put some extra RTV and a modified apex seal spring there as insurance.

j9fd3s 02-15-2006 11:19 AM


Originally Posted by rotarygod' post='801917' date='Feb 15 2006, 12:38 AM

I believe that. A high overlap engine absolutely needs acollected exhaust to get the most out of it, especially on the top end. With an uncollected exhaust (and an overly large one at that), I fully believe it would feel weak up top. Put a nice collected system on that car and hold on.



yep, i think so too, but it was streetably quiet. most of the exhaust was muffler

13BTNOS 02-18-2006 10:54 AM


Originally Posted by ArmyOfOne' post='801929' date='Feb 15 2006, 05:03 AM

How thick is that edge between the BP and the water seal groove? It has been my experience that anything under 1mm will break off within the first 1k miles. This will in turn expose the water seal to the incoming gas and get ripped up by the sharp edge of the apex seal eventually leading to coolant seal failure. You may want to put some extra RTV and a modified apex seal spring there as insurance.



They are all above 1mm the thinnest being 1.3mm I have been contemplating just cutting into the seal area since it will be a N/A motor anyways and not a daily driver.

Maccoretti 04-17-2006 04:32 PM


Originally Posted by 13BTNOS' post='801524' date='Feb 14 2006, 09:52 AM

13BT 4 port plates full bridge port with S5 9.7CR rotor assembly. Running a Racing Beat Holley 650cfm double pumper. The plate on the left is the front intermediate and the one on the right is the center intermediate. The ports are about as large as you can go with the sideseals still being supported. And the bridge ports are to the edge of the waterseal withe the water seals still in tact. Hope to see over 200rwhp that should move a Datsun 1200 that weighs under 1700lbs pretty good.



Sounds very similar to my motor - my bridge is longer with more hook but similar width.

I saw 209rwhp @ 8700 with 48IDA stock seals and 2.5" that merged into 3" after diff.

Idle is healthy 2600rpm and will not come down - feels very strong (like VTEC) post 4000RPM still drivable for street but waaaaaaaaaaay too loud and wont sit in traffic for over 3 minutes



A friend had an identical engine but with 12mm J-port and it was MUCH stronger (1.5 secs down 1/4)

kahren 04-18-2006 09:44 PM

the more overlap you add the more peaky the power band will be, if you want a broader powerband stick with a streetport. you can get over 200whp if you things correctly.

2wankel 04-25-2006 10:27 AM

I dont understand why the hp is low for a bridgeppot. I thought a mild streetport was around 200hp, an extended streetport would be around 220hp, and a bridgeport around 250-270hp


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