Corolla AE86 SR5... My little corolla has had a supercharged 4AGZE with a turbo in it since 1999. It has passed 2 IM 240 emissions inspections, and has been a fairly trouble-free thrill ride since it was built. I have melted 2 speedometer cables, but hey, I have a lot of hot pipes to try to avoid. I also got some wiring tangled up in the steering linkage under the hood and a sharp right turn ripped the wiring harness to shreds. Hey, I was keeping the wiring away from the pipes that melted the speedo cables!
I think twincharging is having the best of both worlds! I get the instant throttle response of boost provided by a roots-style supercharger, and the much higher boost levels that can only be attained by a turbo.
Here is a diagram outlining the system. The 1-way valve is necessary to keep supercharger boost from escaping, while also allowing more air to get to the turbo when it is spooled up.
This is the engine after about 5 years in the car. A turbo failure made me have to remove the engine. A part fell off of the 1-way valve and lodged in the turbo. There has been no problems with either the turbo or the supercharger caused by the compound forced induction setup.
Oops, oh well, it will be back together and better than ever soon. But while the engine is out, I thought I would take some pictures to show you how this whole thing comes together.
Here is a picture of the turbo on the 4agze, it is mounted behind the supercharger and there is a custom manifold that feeds air to the turbo. It is supplied air from the supercharger, and the 1-way valve.
My turbo drain is very low, and I had problems with it. The car would smoke when the turbo was spooled. I finally got it to stop by putting an air vent into the oil drain line. That way the return oil would never have to drain back into the pan under the level of the oil in the pan. The air bubbles in the return line can escape out of the vent line and does not have to be pushed into the oil pan.
Here is a view of the turbo and mount from the bottom. You can see the turbo oil vent line here.
Here you see how the exhaust goes thru a full sized header, crosses underneath the transmission and comes forward to the turbo. There is probably 8 feet of pipe between the head and the turbo. This is the cause of lots of turbo lag.
It is a really tight fit to have the turbo there. In this picture, you can see that there is very little clearance between the back of the supercharger and the front of the turbo intake manifold. The bottom of the intake manifold and the top of the turbo were both ground down for clearance issues.
Here is a hollow spacer plate I made that sits right under the throttle body (the throttle is removed in this picture) It brings air thru a short blue silicon hose down to the 1-way valve, then to the turbo.
Here is a view of the assembly out of the car.
This is the engine without the turbo. Note that the supercharger output points to the rear.
The supercharger's output blows into the large opening, and feeds the turbo. The supercharger's boost closes the 1-way valve, and then the boost enters the turbo. Then the turbo is spinning fast enough to use all of the air that the supercharger puts out, then the turbo sucks the 1-way valve open, and more air is available to the supercharger.
The system works with the supercharger clutch engaged or disengaged. The turbo spools slowly when the supercharger is off, and gave me about 9 psi in the latest tuning session. When the supercharger is on, I get 8psi instantly, and the turbo quickly spools up and boosts to around 14 psi. I have blown my wastegate diaphragm, so I really don't use the wastegate to control boost. Just the spring pressure in the diaphragm holds the wastegate shut until exhaust pressure forces the wastegate open. You'd think a 25 year old wastegate diaphragm would hold up, wouldn't you?
All of the bracketry has been heavily modified. Unfortunately my 4agze was stripped of brackets when I bought it, so they are mostly 4ac brackets that are slotted to allow for clearance of the supercharger belt.
Note a very, very long exhaust path.
ENGINE and here for more about TWINCHARGING
Here's a link to the first dragstrip outing for the car. Drags
Since then, I have installed a LSD rearend with 4.10 gear ratio and a Centerforce dual friction clutch and replaced the rearend control rods with aluminum rods and spherical ends. I replaced the 4AGE ECU with a Celica ECU and re-calibrated it by changing resistor values inside the box. I have some tips for anyone re-calibrating a factory ECU... Don't! (Just kidding) You can make general fuel mods, but the spark timing is written in stone (on the chips anyway). There really isn't any good way to make an AFM-based ECU conrol spark for a turbo/forced induction setup. When you install bigger fuel injectors, your 'accellerator pump' circuitry can be fooled into decreasing the amount of fuel it gives per throttle movement by attenuating the TPS signal, but then the spark advance circuit doesn't sense load correctly. You can regain the throttle response you had with the smaller injectors, but the AFM and TPS signal are not enough to determine if you have boost or not, so the spark timing can not be optimised.
I now run a Megasquirt ECU that controls Fuel and Spark.
Try my Supercharged Engine Page
Or the Twincharging Page
Or the Engine swap guide
The finished and running car is here
My Megasquirt-N-Spark page.. Megasquirt-N-Spark.
Any input would be appreciated and hey, how did you like the page? Twincharger@hotmail.com
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