I am trying to find out what kind of differences there are between the 1985 GSL-SE and the 86 second generation engine as far as compatibility goes for aftermarket parts. I want to put on an aftermarket air filter, I have been told that second generation sparkplugs would not work for this engine and that I should use first generation sparkplugs despite the displacement difference and fuel delivery method being closer to 13b motors of ’86 and up.

While the user manual I have on the car is great for maintenance I am not sure what differences the engine has so I can get certain aftermarket parts for a 1986 13b motor to use on my GSL-SE 13b engine. Any advice would be greatly appreciated.

~Spike~

 

The 1986-1988 Second Gen and 1984-1985 GSL-SE First Gen engines are fairly similar.

Mounting:
The first gen mounts to the front cover. The second gen mounts to the center iron housing. (As a result, the oil pan is different.)

Fuel injection system:
The GSL-SE engine has only two injectors, 680 or 720 cc injectors in the center iron.
The FC engine has four 500 or so cc injectors... Two in the center iron, two in the intake manifold. It improves the idle as well as top end. (As such, the manifolds are different.)

Ignition system:
The GSL-SE uses a distributor to fire the ignition coils.
The FC uses a Crank Angle Sensor and the ECU fires the ignition coils. The FC has a more efficient 'waste spark' setup.


Both engines use similar 9.4:1 compression rotors.
The GSL-SE uses heavier rotors. They have a 3mm apex seal.
The FC uses lighter rotors. They have a 2mm apex seal.
http://mazdatrix.com/faq/rotorwgt.htm

 

The easiest answer is that regarding aftermarket parts, everything is different. As Pele points out, this is not really the case as the engines are similar in concept. But in reality, they are totally different. No parts are shared between the two except some hardware and a few internal seals.

The exception to this is that any 13B header should fit the GSL-SE 13B.

2nd gen spark plugs are fine. I do it all the time.

 

Thank you for the information, quite helpful. I guess I will just have to fabricate my own air intake filter assembly. I was wondering about the headers so that is good to know.

I was planning to get a direct fire setup to replace the distributer anyhow, I will not waste anyone's time asking how since I have seen the posts on how to do that. I noticed the mounting difference as I just changed the oil a few minutes ago.

One thing I will ask is in anyone's opinion would it be a fools endeavor to upgrade the engine to make it more like the FC? Or should I just keep this one going fairly stock until I have enough to get a Third Gen?

~Spike~

 

No, there isn't much point in putting S4 2nd gen stuff on the GSL-SE block. GSL-SE made 135 HP, the S4 NA made 145HP. Just make sure the GSL-SE stuff is working properly.