BP, the yays, the drawbacks, the limitations and reliability

Oyvindjs · 05-02-2012, 07:56 AM

Hey!
I have recently aqquired this little beauty, and i want to give it that real "BRAP-BRAP"- rotary sound it deserves.

Rice, i know about your testings and findings of the stock ports, but i just love the BRAP-sound, and it sounds so baws when you see an oldschool mazda.

I know the bridgeport configuration is slightly less dailydrivable, higher mpg, tend to be "jerky" when close to idle coming off the clutch, and has low power down low, but flows lots of air, especially in N/A configuration. I want mine turboed.
Car is supposed to be a pure and simple fun car.

I have read abit here and there over the years about BPs eating seals due to the contact area between seal and sidehouse being too small and shortening the engine lifespan. Also, i have seen people having cracked the bridge from time to time. I do also recall people trying to fix some of the seal-eating by making the edges on the port less sharp?

expected lifespan on a BP is?

Please, give me the breakdown here

thanks

Sharingan 19 · 05-05-2012, 05:45 AM

A properly engineered an executed bridge will not eat seals and should not significantly shorten the lifespan of an engine.

I say "should not" because I don't know anyone who putters around in a bridgeport like its a daily driver. They are typically hard on their cars and when they are not beating on the car it is sitting (the only thing worse than beating on it). So yes, there does seem to be a positive correlation between bridgeports and shorten engine life, however I think one would be hard pressed to establish a causal relationship , assuming the porting was of reasonable quality.

That being said, you can obtain a certain level of brap with a large streetport, although not quite the same, it may be a compromise you are more comfortable with. If you are insistent on a bringe, consider a half bridge, which leaves the primaries alone (aside from perhaps a streetport) and bridges the secondaries which helps slightly with idle and low rpm manners.

N.RotaryTech · 05-05-2012, 01:57 PM

Im going to say: do it, go for a bridge port.

Since I've had a bridge port running I can provide some truth to some of the things you've heard or read about.

The breakdown, my interpretation:
The Brap: Of course this is one of the greatest things about BPs. You might find yourself letting your car idle more than normal. And Purposely driving in high traffic areas, just to hear you car idle more. You might find yourself sitting at a stop sign in the middle of nowhere...you guessed it, just to hear your car idle.

The power & drivability: Once you get over listening to the idle (for the moment), its time to take off. The low end (anywhere below 3k-3.5k rpms) will suck and drive you mad. You will hate driving in traffic. Starting off is tricky, especially on a incline.

When cruising around, you'll find the rpms at 4k comfortable. Cruising below that? No. When its time for fun and to get your car anywhere quick, put the pedal to the metal. At first if starting at low rpms it'll be like "yeah whatever". Then once the rpms hit 5k and up it will be like "Whoa! Yes! HaHaHaHa!" Then you shift into the next gear and repeat that last part.

Gas mileage: It will suck. 12-15 mpg. That is all.

Flames: Yes Flames. Out the exhaust pipes. On command.

Reliability?: I cant say much on this cause my motor ate a coolant seal pretty quickly after the build. But I can imagine that a bridge port motor can be built to last. Just be very careful building it.

Other notes: Your engine will run hotter. And it will warm-up quicker. And will rev quicker too.

I think that's it.

mazpower · 05-05-2012, 04:33 PM

Just to touch on what N.RotaryTech said...my FD's been running a half-bridgeport since '05. Its been daily driven, raced, beat on, everything you can imagine. Aside from chunky off-idle response, it can be daily driven with no problems. If the ports are done correctly they won't eat seals. IMHO there's nothing like the powerband of a well-sorted boosted bridgeport.

As far as mileage is concerned, I see 15 mpg city and have seen up to 23 mpg on the highway. Not too far off from a stock FD.

05-02-2012, 07:56 AM	#1
Oyvindjs Rotary Fan in Training Join Date: Apr 2012 iTrader: (0) Posts: 78 Rep Power: 13	BP, the yays, the drawbacks, the limitations and reliability Hey! I have recently aqquired this little beauty, and i want to give it that real "BRAP-BRAP"- rotary sound it deserves. Rice, i know about your testings and findings of the stock ports, but i just love the BRAP-sound, and it sounds so baws when you see an oldschool mazda. I know the bridgeport configuration is slightly less dailydrivable, higher mpg, tend to be "jerky" when close to idle coming off the clutch, and has low power down low, but flows lots of air, especially in N/A configuration. I want mine turboed. Car is supposed to be a pure and simple fun car. I have read abit here and there over the years about BPs eating seals due to the contact area between seal and sidehouse being too small and shortening the engine lifespan. Also, i have seen people having cracked the bridge from time to time. I do also recall people trying to fix some of the seal-eating by making the edges on the port less sharp? expected lifespan on a BP is? Please, give me the breakdown here thanks

05-05-2012, 01:57 PM	#3
N.RotaryTech Home-brew Rotary Join Date: Feb 2008 Location: GooseCreek SC iTrader: (0) Posts: 552 Rep Power: 17	Im going to say: do it, go for a bridge port. Since I've had a bridge port running I can provide some truth to some of the things you've heard or read about. The breakdown, my interpretation: The Brap: Of course this is one of the greatest things about BPs. You might find yourself letting your car idle more than normal. And Purposely driving in high traffic areas, just to hear you car idle more. You might find yourself sitting at a stop sign in the middle of nowhere...you guessed it, just to hear your car idle. The power & drivability: Once you get over listening to the idle (for the moment), its time to take off. The low end (anywhere below 3k-3.5k rpms) will suck and drive you mad. You will hate driving in traffic. Starting off is tricky, especially on a incline. When cruising around, you'll find the rpms at 4k comfortable. Cruising below that? No. When its time for fun and to get your car anywhere quick, put the pedal to the metal. At first if starting at low rpms it'll be like "yeah whatever". Then once the rpms hit 5k and up it will be like "Whoa! Yes! HaHaHaHa!" Then you shift into the next gear and repeat that last part. Gas mileage: It will suck. 12-15 mpg. That is all. Flames: Yes Flames. Out the exhaust pipes. On command. Reliability?: I cant say much on this cause my motor ate a coolant seal pretty quickly after the build. But I can imagine that a bridge port motor can be built to last. Just be very careful building it. Other notes: Your engine will run hotter. And it will warm-up quicker. And will rev quicker too. I think that's it. __________________ '89 RX7 GTU, half-Bridge-port S4/S5 NA, E6K, Full RB exhaust, weekend warrior. '83 RX7, The "this might take awhile" project. '87 RX7 GXL, Rest In Pieces. '98 Subaru Impreza Outback-sport, rx7 rescue vehicle, down for repair. '94 Ford Ranger, daily.

05-05-2012, 04:33 PM	#4
mazpower Rawr Bearclaw Join Date: Feb 2008 Location: The Souf iTrader: (1) Posts: 197 Rep Power: 17	Just to touch on what N.RotaryTech said...my FD's been running a half-bridgeport since '05. Its been daily driven, raced, beat on, everything you can imagine. Aside from chunky off-idle response, it can be daily driven with no problems. If the ports are done correctly they won't eat seals. IMHO there's nothing like the powerband of a well-sorted boosted bridgeport. As far as mileage is concerned, I see 15 mpg city and have seen up to 23 mpg on the highway. Not too far off from a stock FD. __________________ Illicit Performance Rotary building, porting, tuning, chassis dyno services www.illicitperformance.com

05-05-2012, 05:45 AM	#2
Sharingan 19 Rotary Fanatic Join Date: May 2010 iTrader: (0) Posts: 138 Rep Power: 15	A properly engineered an executed bridge will not eat seals and should not significantly shorten the lifespan of an engine. I say "should not" because I don't know anyone who putters around in a bridgeport like its a daily driver. They are typically hard on their cars and when they are not beating on the car it is sitting (the only thing worse than beating on it). So yes, there does seem to be a positive correlation between bridgeports and shorten engine life, however I think one would be hard pressed to establish a causal relationship , assuming the porting was of reasonable quality. That being said, you can obtain a certain level of brap with a large streetport, although not quite the same, it may be a compromise you are more comfortable with. If you are insistent on a bringe, consider a half bridge, which leaves the primaries alone (aside from perhaps a streetport) and bridges the secondaries which helps slightly with idle and low rpm manners.