I am planning a half bridgeport build up with a divided housing gt4088r turbocharger and am trying to figure out what is a good route as far as exhaust port size and shape. I'm using a racingbeat bridgeport template on the secondaries and street porting the primaries of my s4 4port block. does anyone know of a good exhaust porting template to use on a turbo bp application? I plan on porting down 4 to 10mm on the exhaust port opening to increase the spool up rate and maybe move the port closing a mm or two. I don't want to cause anymore port timing overlap due to the fact i will be using a 8500rpm cut off. Im looking to make a broad porwerband and to have a narrow transition to full spool around 3500rpm. would a square port be a better choice to maximize the volume of exhaust gases expelled through the port while sending a square pressure wave to the turbine or would a round progressive exhaust port be better to keep the port velocity consistent as the rotor progresses towards bdc. I know that on a periphreial port motor they tend to utilize a more square exhaust port to maximize flow while keeping port open duration low because of the length of time the intake is open to reduce overlap. The square port would have a lower velocity at lower rpms but could flow more at a higher rpm. im wondering which port will be a better choice are there any advatages/disadvantages to each type of port. I havent found very much information on turbo bp exhaust ports and i would like to know what other people are doing for there engines.

 

this one I use on my large street port http://www.pineappleracing.com/ep3ae...t-13b-rew.aspx

This one is recommended for bridge ports:

http://www.pineappleracing.com/ep4ae...eripheral.aspx

It says n/a and peripheral ports, but I called Pineapple about a year and a half ago and they said you can use the 4A on turbo motor. The larger the exhaust port though the more overlap you are going to have (engine vacuum will be worse) and you will have a loss of low end power.

 

I ended up with a very large square port with my own sleeve for my 1/2 bp motor. Spool is insane, 10psi by 2200rpm, on a 61mm turbo (holset h1e) with 4" exhaust.

 

Be careful how much is taken out on the opening edge. The more you go down, the more you reduce the power stroke. Especially for a bridgeport, the tendency in porting ought to be focusing on the closing edge.

What's this about your own sleeve?

B

 

Brian, what are your thoughts on the Pineapple EP3A



and EP4A templates?



I used the 3A template. Once I ported down to the bottomof the sleeve, I beveled it from there to the edge of the template. Then I polished everything. I'm not sure if that was the best way to do things, but I guess it's too late now (motor has been running for a year).

Motor is s4 T2 with 1.00 divided T04R running about 17psi on pump gas.

 

good im glad someone who has exsperience with turbo bp motors like you brian is replying on this tread. ive seen your work and the craftsmanship is very good. i was also wondering about those templates ive had my eye on them for a while. do you think the exhaust opening event would be to soon with the 4a template? extending the port duration by moving the closing edge is more desireable in ithis application, closing the port later will increase the flow of the port during higher rpm operation correct? i just had a thought, would moving the exhaust port closing higher cause a supercharging effect of the intake opening event because the exhaust gases are flowing out while the intake is opening?

 

BDC is right in what he says. Dont take much off the bottom. I have had alot of success with square exhaust port WITH SLEEVE.

 

these are for my semi-peripheral project. i made my own template for these ones.


EDIT: i mindlessly posted this. i forgot that this is a turbo application, so i don't know if mine would be of much use to you.

 

Those will work for turbo.

 

I've got the same questions as the OP, although my setup is quite a bit different. I'm running a streetport 12a with a t04b. I did my porting without templates, for the exhaust I did all the porting from the sleeve side and just opened up the port to the size of the sleeve. I'm looking for a quick spool and won't be revving above 8k. Should I leave my ports matching the sleeve, or square off the corners? The rotor housings are perfect, just dirty and some carbon buildup, the pics make them look bad, but all the chrome is there.

 

You got any more info on this port, i will be porting mine this week and want to do something similar. sizes ect..

 

I really don't remember any of the dimensions of the port as I cut it probably 3 years ago... I will probably end up doing a set similar in a few weeks for a buddy's motor, so I can try and get some details for you if you haven't cut yours yet. I've also got the port I modeled this one after at the shop from one of our customer's EP n/a motor that got trashed, however its much larger than mine..

 

well by that photo I will be able to work something out.

Did you make the port wider??? or did you just go up and down??

 

https://www.rx7club.com/rotary-car-performance-77/critique-my-square-exhaust-ports-904758/

Cause I like starting fires. lol

 

Did you purchase or machine your own sleeve for this port?

 

It might be a little wider, but not much. Sorry, I wish remembered more. It was originally a more standard shaped port that I cut a few years prior and decided to square it out during a rebuild (bad coolant o-rings...) so I'm having a hard time remembering exactly what I did.

Trots, I machined the sleeve myself.

 

I done my port today, just needs finishing touches made. I need to get some finer grit sanding bands tomorrow. The one on the right, the left is ****, from a Uk builder/tuner.

 

how much does square vs round really matter?

 

Not sure but I will find out in a couple of weeks. If you read the thread it is meant to help spool better.

 

Opening that pretty early. Better to focus on closing end.

B

 

Its not to bad, the housings arnt lined up perfect so looks like it does. Maybe went down 5mm for the standard port and 3mm up, but made it more square.

What angle and width of the chamfer does the closing edge need to be??
The photo is a bit **** as its from a camera phone.

 

Looks good.

 

closing edge chamfer stock is around ~2mm, and at roughly 45*. You can go over it lightly with some fine-ish sandpaper after to smooth the sharp edges.

2a+ron's closing edge seems a bit smaller, so if he's used it with success, it would seem to flow better

 

Cheers for that Trots, its at a 45ᴼ angle now and about 1.5mm so should be Ok, getting 2mm means cutting in a fair bit more and I dont want to screw the port up by doing that.

I have chamfered the closing edge and the sides, the sides have a small chamfer at the bottom gradually getting bigger at the top so this should help.

The stock sleeve is still in there aswell, this seems as big as you can go without moddifying the sleeve.

 

To be honest that porting looks ****, it doesnt look tidy. Remember both your ports in both housings should be the same.
The closing edge has no chamfer on either, not good for your apex seals.