4A-GZE Intake & Exhaust

We used an intake hose from Carl's box o' spare parts for his GT-S. The AW11's original intake hose placed the AFM too high and would interfere with the hood. The stock GT-S hose angles downward and is longer. The larger 3" diameter adapter (I believe HKS makes these, and we purchased it from CAP) was mated to a K+N cone filter. Presently, the cone filter is laying in the hot engine bay, but eventually the filter will be relocated into the left side wheel well space using 3" O.D. mandrel bent aluminized tubing from JC Whitney. The AFM wires needed to be extended to reach the new location which was accomplished with some additional wires, solder, and shrink wrap.

The intercooler mounting poses a big problem for the GZE. The AW11 setup doesn't clear the hood in its OEM position, and believe it or not, the intercooler itself is too big to fit in a front mount position. We are currently working out a location to mount a SAAB 900 intercooler (aluminum core, manufactured by Blackstone), but until that time, we had a muffler shop bend us some piping to connect the S/C inlet and outlet. Stay tuned for more info.

The exhaust setup that was initially used was as follows:

The primary + secondary + catalytic converter match up perfectly, however, there is about a 6" gap between the catalytic converter and the remaining piping. After we got the car started, it was necessary to drive the car, essentially unmuffled, to a muffler shop to get the piping connected. We fired up the car, and drove it the long several miles until we found a muffler shop who would do the welding for us. Let me tell you, an unmuffled 4A-GZE is pretty damn loud. Driving through an alley, the exhaust note ricocheted off the adjacent buildings, setting off car alarms like nobody's business, and even rattling the lawn chairs in the back of Carl's girlfriend's SUV. Literally deafening.

I'm actually a bit disappointed that I didn't bring my video camera with me. That morning, JoAnn dragged me along to get some concert tickets with her. Immediately afterwards, we picked up Alan at the BART station and headed over to my uncle's shop to pick up the car and bring it to a muffler shop. First thing outta my girlfriend was, "That's awfully loud, isn't it?" She included some colorful expletives, but we'll leave 'em out of here! Anyway, I was following chase and was totally amazed at how loud the exhaust was. And Alan told me that he was short shifting around 1500 rpm the entire time! Hahaha. The most tense moment was when I saw a police car in the adjacent lane, coming up fast. It just happened that the light turned red and Alan and the cops were side-by-side! The exhaust tone was even louder when starting from a dead stop, so I had a sick feeling that the cops would nail Alan. For some odd reason, they just kept on going. Whew! Just to be on the safe side, we pulled over for a quick minute and made sure that there were no other cops around. Honestly, I think you could've heard Alan coming from 3 blocks away... -Carl

Well, the above combination works in terms of getting the car around, however, since the 4A-GZE is a forced induction engine, it is very sensitive to exhaust flow changes. This combination was seriously choking down on the power, not to mention it had one of the ugliest exhaust notes you have ever heard, so something had to be done. First, I dusted off my old Ultraflo Muffler, and got to work, with help from a local muffler shop. With the Ultraflo welded in place, and new 18" long resonator, the exhaust note changed dramatically. Gone was the harsh, raspy noise, and in its place, a nice, mellow rumble. No fancy tips here, just 2.5" O.D. aluminized piping to finish off the system.

Back up at the engine bay side of things, we decided to swap out the 4A-GZE exhaust primary and 4A-GE secondary for something a little nicer and lighter: a ceramic coated KBD header. (insert pict)

The header itself is a quality piece, and the ceramic coating has an aluminized appearance to it. Specific details of this header can be found on Carl's writeup in the tech section. Although meant for the 4A-GE, the header fits perfectly, well, almost perfectly, into this application. Problems? Well, firstly, good luck getting the mounting holes on the flange to line up. I recommend test fitting and enlarging the hole (Use a 7/16" drill bit. -Carl) before getting too down and dirty with the rest of the install. Secondly, do the KBD before any additional piping is done to the rest of the system, because for some reason, the entire setup was about 1" too long. We had to fight to get the KBD to fit with the other piping. Finally, the O2 sensor dilemma...

The 4A-GZE came with a 4-wire sensor. Some corolla's came with a single wire sensor, whereas others came with the 4-wire. Initially, I forgot that the 4A-GZE had the 4-wire, so I snagged a single wire one off a wrecked car. No good. Although we could track down the signal wire and splice into that, the single wire was giving the ECU an error, and I dealt with the dreaded check engine light for several months. The visual deterrence of the check engine light is not as bad as what it does to both your gas mileage and performance--both decrease dramatically. The engine will run rich as a result, so it's best to pony up and get the correct sensor from the start. You will probably save the money via better gas mileage, anyways. The 1988 Corolla GTS also came with a 4 wire sensor, however, the harnesses and flanges are slightly different. The 4A-GZE's 4-wire sensor has a flange that measures approximately 44mm center-to-center (as measured from the mounting holes), whereas the GT-S's measure about 54mm. Be sure to measure the KBD's flange, as there seem to be some inconsistencies with this throughout the KBD lineup. Carl's KBD has a flange measurement of 54mm, working perfectly with his 4-wire, however, my KBD used the 44mm spacing. Trial and error, but eventually we figured it out. By using the 4A-GZE sensor, you don't have to splice any wires here, and the sensor will just barely reach the flange (assuming you use the same AW11 harness in an AE92 and the KBD header for the GT-S. -Carl).

One major problem with the KBD is that the EGR pipe doesn't even remotely line up. The location of the EGR boss on the AW11 header is slightly different than that of the GTS. Remember, the KBD I used was designed for the GT-S, so when we swapped out the OEM unit for the KBD, problems arose. Currently, we are using the differential drain plug from my TE31 corolla to take the place of the EGR. No idea how to smog it yet. (If you're so inclined, you can always fabricate an EGR pipe that'll mate up with the AW11's EGR valve and the EGR boss on the GT-S primaries. -Carl)

Well, with the KBD and Ultraflo, I am pleased to say that the combination pulls like a freight train. As of yet, we still have not completed the ABV mod, for lack of proper intercooling. Meaning, of course, that the Blue Bomber is running at the stock 8 psi of boost. Better watch out when we hit 14.