S4 Turbo, rebuild and porting questions
 

Hello,

I'm currently driving a 1986 Turbo s4 it has about 130000km and no engine issues. I have a spare engine with about 120000km. It's already disassembled, and in good condition. As I will rebuilt it, I thought why not porting it ?
I looked all over the web to find informations but it's quite difficult to search with the good english words as I speak french.

So let's ask some questions !

I was thinking of going on a bridge port. I like so much that brap brap brap at idle, but what exactly make this noise ?

Is there any way to pass smog with a bridge port ? I don't know in the US but here in Switzerland, smog is at idle (850rpm).

What will be the lineaments (not sure of the word) of a bridgeported 13bt ? Where will I have torque and power ? (I know it will depend a lot of the ECU and the turbo but...)

I was thinking of porting the engine without templates. What would be the minimum width of the bridge ? And how much material should I leave between the port and the water seal ?
What would be the differences if the bridge is as long as the main part of the port or only the half ?

I have thousands of questions but I try to order them... :P

thanks for your answers

Im not sure ur regulations with smog thier. But I wouldnt recommend porting without a templete and expirence. If you want to port get a template from a republe seller like Mazdatrix. Also you will want a ecu that is pre programmed for Bridgeport and supporting mods. Since bridge port is very agressive on AF without the right pcm and mods its a guarentee your engine won't last 2 minutes on first start up.

Yes I know that I shouldn't :blush: but I'd like to learn to make my own port design.

Maybe you're right. I should port with a template the first time, but if somebody could answer my questions about a bridgeported engine's character and what are the influents parameters, that would be nice :)

Is it possible to run a mild bridge ported 13b on the stock ECU with some hardware modifications ? Juste for the break-in procedure, and then make a fine ecu tuning ?

You can with mild bridge port but the stock ecu with raise rpms to near 2k for cold start and you can risk lean conditions and possibly bust a apex due to wrong ignition timing

The sound comes from port overlap a point measured in degrees of eshaft rotation. The more overlap (longer duration) the idle quality suffers. Manifold vacuum also decreases due to the overlap. A Bridgeport makes power high in the powerband. To take full advantage of the effects you need proper supporting modifications. Like intake, exhaust, tuning etc. I would recommend doing a streetport for your first to learn the basics. I would recommend a Pineapple Racing mild streetport template. Your also gonna want to port your rotor housings to match the intake.

I thought about it again and I won't effectively go with a bridgeport for my first engine.

So if I go with a mild streetport can I break in the engine with the stock ECU ?

And what are the gains with the mild streetport on a same setup ? By same setup I mean same injectors, intercooler, turbo, etc. (For exemple 2x750cc, bigger intercooler and a gt35r.)

There is no possible way to pass smog with a bridgeport. Period. Going with a bridgeport also requires a host of other upgrades: turbo, EMS, etc.

A mild street port, if you keep the boost around stock levels, is fine on the stock ECU.

Any turbo upgrade requires a standalone.

I will go with a standalone later but first I need to break in the engine. If I go with the xtreme rotaries streetport template, stock turbo, will it run on stock ECU ?

It will run stock boost on the stock turbo.

thanks, and do you know if the main part of the port is the same on their streetport/bridgeport templates ?

Everybody's porting template is (well, should have been) developed over years of practice and testing. It's like going into a restaurant and asking for the recipe for their secret sauce. You'll probably just have to buy the template from them.

I have no information about their porting either, sorry.