R.P.M.

Hey Guys, just a few questions about porting a bridge port.



I cut this port using Ito's agressive street port template and then used the Racing Beat bridge port template as a guide for the bridge.

I measured the actual width of the bridge and its roughly 4mm wide. Discuss.......



I talked with BDC about cutting bridge ports and he tells me he likes to have a 6mm wide bridge, which would make it essentially last forever. So I'm wondering if my 4mm wide bridge is too small? I'm going to be using solid corner seals and I'm going to build the motor with the corner apex seals facing the center iron since this motor only going to be a half bridge.



Anyways tell me what you think, its a Cosmo RE motor I'm working on.

sidewinderx7

Im no pro, but 4mm seems to me like it would be fine. The corner seal itself shouldnt be bigger than that and if it is, barely.



I cant really tell if the bridge is beveled or not. I do know it helps out a lot when it is and is technically the proper way to do a bridge.



But it looks good!

13BTNOS

That bridge is fine the only thing I would be concerned with is the path of the side seal across the bridge. Make a template out of lexan and see where the leading edge of the side seal is going. If the leading edge of the side seal goes into an area that is unsupported it may catch on the port and end up eating a sideseal.

BDC

Hey RPM, I typically do about 1/8" to 9/64" wide by about 1.5 to 1.7" in heighth for the cut.



From what I've noticed, any small variation done to the cut will have a fairly dramatic effect on fuel consumption, idle, drivability, and peak torque/power band. This is why I am reluctant to do an FBP.



B

j200pruf

BDC, but do you have to take the stock port up a little bit and then have a ~6mm bridge, or is the location of the bridged opening not as important as the bridge itself?

alaskarotorhead

A 6mm bridge should support about 90-95% of the side seal.I have run a 4mm bridge with the bridge centered under the corner seal with great luck,as mentioned earlier use plexiglass,trace your seal paths,as long as the front of yourside seal does not drop into the port,Not the upper one bt the side seal that will ride on the bridge,and your corner seal is supported well you should do okay.BDC is right about tuning with a full eyebrow on turbo motors,on n/a applications it does not seem to cause problems though.flipping the apex seals around is the right way to go,the first 1/2 bridge I built was set up this way,abused and is still running

2 1/2 years later,atkins seals have the cut about 4mm in from the end of the apex seal so th corner piece dropping in after some wear shouldn't be an issue,but flipping them around is failsafe.ports look good,if you want to drool check out bdc's pics.....



Nick

BDC

Thanks for the compliment, Nick. On the Atkins seals, I use these primarily and they work well with bridgeports. I spoke to Dave Atkins once about them regarding the corner piece that you guys have mentioned and, as Nick already said, they will work in either position. Apparently he cuts the corner piece to be thicker than the Mazda one as they were originally designed with bridgeporting in mind. They are cut to prevent themselves from falling into a bridged intake port. The sharp, triangular corner pieces (like stock Mazda) however will get stuck and fall in the port so do not put those on the bridged side!



B

13BTNOS

How important is the closing edge of the sideseal in regards to it's path over the port. Does it need to be supported or not? If you look at the port you can see the scribe mark that is the path of the leading edge of the sideseal it is supported across the whole bridge. Port is ruff cut haven't cleaned it up yet.

BDC

I think that'll be fine. What I do when making a bridgeport cut is to not extend the width of the standard secondary port by much at all. I try and keep it fairly close to stock as far as the short radius side of it goes to help ensure a thicker bridge as well as keep some metal for the side seal to ride across.



B

Node

do you have to go to 1 piece seals with a full bridge or can you get away w/ stock 2 piece seals?

What rpm should you stop using the new mazda 2 piece seals? I've heard in general 8500 for most stock parts, but been told they can go higher with no problem.