84-91 Emissions Removal Option, Electric Fan, Custom intake

(fuel injected engines)


  We all know that stock rotary engines come with a lot of unnecessary, complex “stuff” on and around them. Metal vacuum spider, air pump, brackets, control valves, hoses, and just “stuff”. Most of us live in areas where we don’t have to pass visual or sniffer tests. For those who do not, you have the option to remove all the stuff. Generally you don’t gain much if any horsepower from doing so, but you get a nicer, clean engine and enginebay, and often a better running engine as far as reliability and response. Most importantly you gain the ability to work on the remainder of the engine in as little as 25% of the time it would have taken you with all the stock stuff in place. Removing the stock clutch fan and shroud and replacing them with a nice shrouded electric fan can allow hp and response gains as well as free up a LOT of engine bay space. Removing the stock air box and snorkel and installing a cone filter can add power and tone as well as clean up the bay even more.

Emissions Removal

When I do emissions removal, I do the following pretty much standard on all engines:

-remove vacuum spider and hoses

-remove air pump and brackets

-remove air control valve (acv) from intake manifold (the funny looking part with wires and round pieces on it above your exhaust on the intake manifold)

-remove some dashpots, brackets, and secondary throttle plates from throttle body (commonly called throttle body mod or TB mod)

-remove subzero start assist bottle and valve (89 an earlier models may have this)

-remove bypass air control valve (BAC) and associated coolant lines. The function of this valve is supposed to be to raise idle under “load” situations such as a/c at idle, p/s at idle, brakes at idle, headlights at idle, etc. Often this valve doesn’t do its job properly anyway. A healthy engine can usually overcome any of the above obstacles without use of the valve, but those individuals really picky about these things may wish to leave it in place.

-remove EGR valve.

-everything that is now open gets capped off with vacuum caps or aluminum blockoff plates (I purchase mine from an online supplier).

-remove cold start thermowax. This is a device on the throttle body that is fed by 2 coolant lines. It is a cylinder filled with wax, and when cold, the piston is retracted into the cylinder. An adjusting screw rides on the cylinder, and by way of a pivot, rides on a cam which is connected to the throttle plates. When cold, the setup holds the plates a hair open all the time (as if your foot were on the gas) to keep the cold engine idling a bit higher. As the engine and coolant warm up, the wax melts, the cylinder expands out, and pivot moves off the cam, and the plates close up to normal position (slowly) and normal idle speed.

Removing the thermowax is not a great idea for everyone, but it does get rid of a couple of coolant lines. In general I remove the thermowax and BAC valve (see above) either both at once or not at all, since the coolant lines route through them both. IF you get into your car and drive immediately, removing it wouldn’t much affect you. If you like to start your car in the morning and let it warm up, you need the thermowax left in place. The benefit of removing it is the lack of coolant lines connecting the intake to the engine, meaning it is much easier to remove it if need be. ON turbo models this is especially important…on nonturbo models it is not hard either way.

You also have a few other options at the same time:

-remove stock oil metering system **to allow user to run 2-cycle premix in the gas at all times**. The benefit to this is a cleaner engine externally, less oil consumption by the engine, and cleaner 2-cycle premix burning internally (necessary to lubricate the apex seals, which is what the OMP system did with crankcase oil) leaves fewer deposits on the internals and probably does a better job of even lubrication internally. Note that you will have to religiously pour in premix with your gas, without fail, after removing the system.

OMP, rod, oil lines, vacuum lines and oil injectors get removed and blocked off. Note that on 89 and later cars you can perform this mod but the pump itself must remain plugged in to the harness or the computer will spit codes and cause poor running. The pump can be tied back out of the way, and does not need to be installed on the engine, for the computer to remain happy. 88 and prior cars do not have this issue.

-remove a/c and p/s. Hardcore owners often wish to clean up the engine bay and remove weight and complexity from the car by doing this. You remove the p/s pump and lines, and leave the stock rack in place. You remove the a/c compressor and lines, and in some cases the drier and condenser. Then you take the bracket off the engine, and you’re left with a very basic engine block and intake/exhaust manifolds, water pump and alternator, and that’s about it.

-on nonturbo engines, some people choose to remove the 5th/6th port sleeves, rods, and actuators for a simpler, bulletproof setup. The 5/6 ports are a variable intake system that open at higher rpms for better airflow, sort of like a vtec for a rotary. However sometimes they get stuck and don’t function properly, leaving you with less power on top end. Removing the stuff leaves these ports open all the time, which is great for high rpm power, but not so great for idle and low-end pull (like taking off from a light or on a hill). This will vary from owner to owner, but personally I don’t mind having removed/open 6th ports at all. It will cause your idle to be a bit poorer, and low end response to lag a bit more as well, but you never have to worry about whether or not your ports are opening for full power on top end.

Note that I can perform any or all of these modifications to anyone’s car, but they’re best done during an engine install, such as while your car/engine is here for rebuild. Keep this in mind when considering a rebuild, even if I am not doing the install, I can still set up your engine this way while it is here.

Emissions removal during a rebuild/installation costs $100, in addition to the other charges. Emissions removal for an engine already in your car (drive in with stock motor, drive out with a stripped one) is $200.

Injector Information
Fuel Cut Off Switch & Unflooding Procedures
Rebuilt Engine Start Up and Break In Procedures
N/A to TII Conversion
Automatic to Manual Transmission Conversion,

1986-1988 Pulsation Dampner
Airpump 6 PI

Internal Engine Damage
Coolant Seal Fix
ECU Application List
Engine Removal
Engine Teardown: Longblock to Shortblock
Series 4 to Series 5 Engine Swap
Series 5 to Series 4 Engine Swap
Emissions Removal
Compression Check

Cone Filter/Intake Modification
Electric Fan
Electric 6 Port Conversion
Series 4 turbo engine emissions removal
Series 5 turbo engine emissions removal
Water injection treatment for all rotary engines
Back to Tech Section