Half bridge port on stock ecu.

[N.RotaryTech]

So a little history on my '89 rx7 gtu, s5 na

When I got it, it had 145k miles on it, got a rebuild, Ive daily driven it since Nov. 2005, it now has 199k miles.

Ive done a few upgrades to it the past few years,
racing beat mufflers an pre-silencer,
emissions removed including aux actuators and sleeves removed, and vdi wired open,
intake filter w/heat-shield,
clutch-masters stage 2 clutch,
And other misc. things like window tint an speakers.

This car has gone through two alt belts, two drive-shafts, two clutches, and a set of tires lol.
Its never left me stranded but gave me a scare when cruising the mountains one weekend when it had sever cut-out problems.


Now for the bridge port:
Why?
I got a screw come loose in my brain at dgrr'10 when I saw ErnieT's FD brap'n away at the lodge.
Ive always wanted to do a bridge port or something of that caliber but never had the mind (or screw loose, in my case) to actually do it.

So I had an s4 na parts car with a engine that I rebuilt with a large street port with only 8 miles on it just sitting.

I took the s4 engine out, took it apart, added the bridge port, cleaned the engine parts up alittle, put it back together, took the perfectly good running s5 engine out of my daily driver, swapped the s4 bridge port engine in.
And I did all this with no expense. Reused everything.

How I got it running:
At first it would start but not stay running.
My brother was helping me the day I got it running. He happened to have a pair of 550 injectors with him. We swapped them in place of the primaries, also had to swap the s5 injector connectors with s4.
We tweaked the throttle body adjusting screws for the idle. Installed a fuel-cut switch. We had a wide-band o2 sensor to check the ratio's, which were rich all across the rpm range.

It ran like shit the first two weekends. Rough start-offs, bad hesitation at cruising, and it would bog down after 7k rpm's. The first two tanks of gas were guzzled at 11.9mpg then 13mpg.
I took it down to my brothers to install two 50ohm resistors in parallel inline with the secondary injectors. That fixed the really rich issue in the upper rpm's. The 3rd tank of gas was about 15mpg.

It still has hesitation at cruising. Ive gotten used to the way you got to drive a bridge port. Most of the time its got to be on an off. lol. It revs faster than before, and goes faster too.

Next comes proof (pictures, etc).
Ill post em up soon. They are also in the link in my signature.

[project86]

all on the stock ecu eh? sounds like an accomplishment. i may be wrong but it seems like you would at least want to run a piggyback. A BP would be awesome though.

[GorillaRE]

Why?

[88turboii]

Originally Posted by GorillaRE

Why?

why stock ecu? um maybe cause its free?? maybe everyone doesnt have $500+ to drop on a standalone

[project86]

why to what i said?

[sen2two]

Friend of mine did this a few years back. Ran super hard for a long time. But a simple SAFC would make a HUGE difference.


Its much easier to do bridge ports on stock S4's. If you pop off the casing on the S4 MAF. You can "tune" it enough to be happy. But not to its potential...

[N.RotaryTech]

Taking out the s4 engine from the parts car.
This is what came out of the manifold when I took it off.

The engine only had 8 miles put on it from the last time I rebuilt it, and that manifold was clean I thought.

Engine out.


Result of Dremel tool meeting the old, worn pilot bearing.


Parts.




Smoothing the edges, primaries.


Small amount of porting and lots of oil build up.


Secondaries. Before.

[N.RotaryTech]

Secondaries after.




The day my daily driver changed, ripped its heart out just for spontaneous curiosity.


The girls meet for the 1st time.


The beast is in.


The s5 manifold didn't fit over this area, so i grind-ed it down. I actually grind-ed a lot more than that.

[need RX7]

Originally Posted by N.RotaryTech

Secondaries after.

Cat litter?

[N.RotaryTech]

A few more details:

I just have the s4 block in there, most every thing else is s5, manifolds, etc.
I had to swap the water pump an housing, from s5 to s4, cause the s5 didn't fit with the s4 front cover.
As mention before, I had to swap the injector connectors, I also swapped the coolant temp sensor connectors.

Why? See 1st post.
Just a spontaneous decision, with the backing that Ive always kinda wanted to do this.

In other news, a week ago or so, my power steering pump decides to go loony on me, leaking an making lots of noise. So I took the belt off.

And as of last weekend, I believe I have a hot start issue.

[N.RotaryTech]

The bridge port could of been made bigger.
I only made it 1/8 inch. I should of made it 3/16 inch.

I probably will redo it over again sometime. Hopefully nothing will majorly blow up inside.
Bigger bridge port area. Maybe a full bridge. With new water seals, one piece apex seals, maybe solid corner seals. Etc.

Future plans?
Megasquirt, rebuild as mention above, turbo application.

[lh6601]

Definitely different and well done.

[Whizbang]

birdgeport is the way im going for my next engine for my silver 82. Now what im doing battle with is going with either full bridge or 1/2 bridge.

[sen2two]

^full bridge...

[RETed]

Here's the problem...

You increase the breathing of the engine, but it's still being choked by the (stock) intake manifolds and (probably) the exhaust.

Ask the BP gurus and flow is everything...
There's a reason why they run short intake (manifolds) and big exhaust systems.

This is why people ask: "why?"

Sure, it'll run...
Run efficiently?
I personally doubt it.

I personally think the ports are cut really bad.
"Well done" would not be the words I'd use to describe the port job.


-Ted