Building a supercharger car based on the Toyota A-Series engines

In 1986, Toyota released a supercharger car based on the stellar 4age motor found in the corolla. The MR2 with its mid engine rear wheel drive platform was a great everyman’s supercar and was powered by the 4agze supercharged motor…

Now, everybody’s heard of unicorns, these mythical creatures that somewhat similar to horses, but possess more beauty and more power with their visually distinctive uni-horn. However, nobody’s ever seen a unicorn. Some of us may even begin to doubt that this mysterious creature every existed. The same goes for the 7AGZE engine. Almost everyone I know who’s interested in Toyota has either heard of it, thought of it (and thought it was original), or thought of actually trying it? But to date, very few people have seen it.

The 7agze is a hybrid engine of:

4age: a 1.6 liter rev happy engine first introduced in rear wheel drive corollas. Coupled with a 5 speed manual , a Front/Rear drivetrain configuration, and a very light chassis (no airbags, no crumple zones, no sound deadening, no seat massagers, no nonsense) made for a fun commuter car that later became a drifter’s modern classic.

7afe: a 1.8 litre stroker version of the 4age that was used on early 1990s celicas. The 7afe increased displacement by 12.5%, brought peak torque at a very low 2800 rpms. However, the 7afe differs from the 4age in that is uses the Toyota ‘F’ head design with a narrower 22* valve angle for increased low rpm fuel efficiency at the cost of high rpm exhaust scavenging and peak performance.

4agze: The ‘Z’ in 4agZe stands for a positive displacement roots style supercharger. The supercharger was a good compliment for the high revving 4age in giving it better torque at lower rpms and increasing peak power potential to take advantage of the high flow , large port head.

3 way compare:

4age	4agze	7afe	comments
1.6 liter	1.6 liter	1.8 liter	Highest displacement
9.4:1 compression	8.0:1 compression	9.5:1 compression	Lowest compression
115 hp @ 6600	145hp @ 6500	110 hp @ 5600	Highest peak power
100 ft.lbs @ 4800	140 ft.lbs @ 4000	114 hp @ 2800	Earliest torque output
0 psi boost	7 psi boost	0 psi boost	Supercharged
7600 redline	7500 redline	6300 redline	Best flowing heads

 

The 7agze is not a motor produced by Toyota. The 7agze is a ‘unicorn’, it is an enthusiast concoction similar to installing GT-40 heads on a mustang small block ford to come up with a ‘factory parts’ hybrid car that outperforms both the original engines. The goal of the 7agze is to create a hybrid motor using the 7a stroker bottom end with the high flow ‘g’ head from the 4age (with its matched cams and intake/exhaust manifold that are optimized for peak power delivery at 6600 rpms, which is much closer to the 7afe’s redline of 6300 than its current peak power rpm of 5600) and to produce a car that supercharged to about 10psi of boost will produce:

203 hp @ 6600 rpms @ 10psi and 180 ft.lbs of torque at 2800 rpms

By doing so you create a motor that has higher peak power than all three of the original motors, and have a wider power band of 3800 rpms compared to 1800 , 2500 , 2800 powerbands for the 4age, 4agze, 7afe respectively. So not only do we have a more powerful motor, but we now also have a more usable motor that is better performing in mid-gear passing acceleration and on corner exits on the track!

Coupled with a light bodied race-car, and some sticky rubber, 200 measly horsepower can run circles around much more powerful cars with heavier less poised bodies.

The 7agze is a unicorn that is seldom seen on the road for many reasons:

1- It requires a unique blend of junkyard sourced or Japan sourced parts from THREE different motors. This scavenger hunt style engine build can take a long time in planning and sourcing parts before the build can even begin.

2- There is no factory computer that will work for this hybrids as the stroke, piston speeds, peak power figures, and volumetric efficiency of the motor shift all over the place from the unique mix of a shorter bore/stroke ratio, a higher flowing head, and clutched supercharger that can be switched on/off at the user (or the ECU’s desire).

3- Due to the differences between the ‘F’ series head (that utilizes dual overhead cams driven by a single cam gear and a ‘master and slave’ gear set between the intake and exhaust cam), and between the ‘G’ series head (that utilizes a true dual overhead cam setup with two cam gears) then neither the 7afe nor the 4age nor the 4agze timing belt is a direct swap for this hybrid motor. The proper installation and timing of the engine requires an enthusiast with the patience and understanding of cam and crank timing to make sure the rotating assembly is put together properly.

Because of these three reasons, the 7agze has usually been left to enthusiasts that want to showcase their mastery of part sourcing, engine tuning, and engine building as all three skill sets must be present to build one of these (in stock form). Building a modified 7agze with more power requires even more wizardry.

One such example of well put together 7agze is the beast put together by ‘The Boffin’, the list of modifications includes:

Engine
7agze
1800cc 7afe block 1996 celica st overbored & decked
4age big port head polished & ported
HKS 1.0mm steel head gasket
Oil cooler pistons jets machined in
Arias 81.5mm oversized forged pistons
Pauter forged rods w/oil feed to small end
Porsche 924/944 1986 117x19mm timing belt
NA inlet manifold
Celica GT 55mm throttle body
Supra 1ggze/previa sc14 1435cc supercharger w/sc12 125mm small pulley fitted
Fensport oversized pulley kit
HKS adjustable cam gears
AE92 4agze dli & ecu
PFC HKS f-con & gcc
400cc black supra injectors
HKS super header 2 s/s 4-2-1 manifold & super drager exhaust
HKS intercooler

 

Some of the most notable parts on this particular install is the use of the larger SC14 (1.4 liter) supercharger combined with a Fensport 176mm crank pulley and 125mm supercharger snout pulley. The resultant pulley drive ratio is 1.408:1 so with each revolution of the motor we have 1.4 revolutions of the supercharger and a total of 2020.5 cc or air. In comparison, the 4 stroke 1.8 liter 7agze breathes in about 900cc per revolution (half of its displacement) of air depending on its exact volumetric efficiency at that rpm range.

The result of this combination is an easy 18psi of peak boost pressure and a potential peak power figure of 270 horsepower @ 6600 rpms!

Also notable here is the use of a 4-2-1 exhaust manifold. Four into two into one (4-2-1) exhaust manifolds merge adjacent firing cylinders together first, and then merge the two resulting exhaust branches into the final exhaust collector. This creates two distinct exhaust pipe lengths (one equal to the length of the primaries, and one equal to the total length of the header tubes from flange to collector). This in turn produces two resonant peaks (or two rpms where power and volumetric efficiency) is boosted which goes well with the promoting a wide and linear power-band between those two peaks. This header design then matches our engine build with a wide 3800 rpms power band. On cars where power is more peaky or the power delivery is over a narrower rpm range (such as a normally aspirated 4age with only 1800 rpms between peak torque and peak power), then the use of single merge 4-1 header usually does a better job of exaggerating that single power peak, however for this application the choice of a 4-2-1 header is perfect, and it doesn’t reduce any top end power as the high boost and high flow head can take care of those tasks.

Final thing to notice here is the use of the fully programmable HKS F-Con and GCC which give the user the ability to completely remap the fuel and ignition timing delivery during high power demands, but leaves the stock ECU in-place to take care of items better fit for the OEM ECU such as idle speed control, and closed loop fuel tuning (for good mileage and efficiency) during cruise and low load conditions, such as other more delicate controls such as knock detection and active timing retard to save the motor in case of a bad fill of gasoline.

Very neat little motor (that would be a great learner experience for a father-son build due to its coverage of all things automotive from engine assembly , to timing, to EFI and tuning , to supercharging …etc) and also a great example of supercharger performance boosting the power output and competitive nature of a frankly small displacement motor.

Here is a video of a NON SUPERCHARGED 7age taken to 7000 rpms…. just imagine 18psi on top of that!

httpv://www.youtube.com/watch?v=cq6rkt8jZJA

For more information on the remainder of the modifications on this car or to contact the owner directly please visit: Driftworks