Juiceing the Automatic 3A

[CathodeRayTube]

Im thinking about engine upgrades for my restored Automatic T4 that i have been driving for over a year now... It is my understanding that the automatic trans is more rugged than the 6spd...right? Im thinking about keeping the whole 3A lower end and sticking a 16v head from a 4afe or similar on it...is this possible? as well as both a Weber carb and a turbocharger...any of this sound realistic? The goal would be to keep the 3As small displacement, increase fuel efficiency, allow the engine to be more optimized for revving high as is the case with the automatic, breathe better, and of course increase power...

Maybe even rig a "turbo" button from an older PC, mounted on the dash for grins, allowing the turbocharger to be connected/disconnected and toggled on and off on-demand...with pneumatic or electric valves shifting the airway to either include the turbo or bypass it and allow it to run normally aspirated...

Im seeing about 24MPG with the automatic and stock everything (except i did advance the timing to about 10-15 degrees)...

[irowiki]

24mpg combined?

I get about 20 to 24 on my t4 auto city/highway.

[CathodeRayTube]

Yes 24 combined i guess. I did manage to add up 30 when i was doing alot of mountain driving every day averaging about 40-50mph and lots of hill climbing & descending with no throttle on the descents..

[dlb]

forum member aubrey falconer tracked mileage in his automatic t4 for a while. he averaged 25 mpg, with a best tank of 33 mpg. here's the link to his fuelly page.

http://www.fuelly.com/driver/aubrey/tercel

[Petros]

the 100 cc difference will make no measurable difference in fuel economy, so why bother consider the all the unknown issues for getting the 4afe head to properly interface with the 3a engine. the piston cutouts are wrong for the head anyway. Everything will bolt on to the 4afe engine for a tercel install, so why risk the trouble of making the 3a engine work with a 4afe head? all of the difficult parts of making the 4afe work in the Tercel are because of the head, so you have to do that anyway. The 4afe is tuned for high torque at lower rpms and high fuel economy already, I would not mess with that combo. keep it together as one engine, it will make your life easier. Your fuel economy will greatly improve if you go with a stock 4afe with the same ECM and EFI system, as well as your max available power.

I am not so sure that the auto trans is more durable, several members have had the main shaft link between the auto trans and front diff fail in the auto trans installation. there are threads on the topic.

[CathodeRayTube]

I just figured it would make more sense to attempt keeping everything 3A based because i have about 3 extra 3A engines around...and that the heads would just be interchangeable and the 16valve one would make it breath better. But i see your points, it probably is best to keep either the 3a, go 4a or 4afe without attempting to crossbreed anything. It will most likely stay 3A as it would just be another unnecessary project.

[GotToyota?]

Who said the 3A block doesn't with the 4A heads?

My motor is a frankenstein 4AGE, 3AC block with 4AGE head. Runs great and is very rev happy. Of course there are some things that need to be tinkered but that goes with any swap.

The advantage of the 3A block is that it's cheap to bulk up and has the 6 bolt flywheel as opposed to the 8 of the 4AFE and 4AGE.

[teranfirbt]

The 4AFE uses the same flywheel bolt pattern as the 3AC.

[GotToyota?]

Ah ok, I didn't know that.

After going through my swap and looking back on it now, a 4A-FE swap would definitely be the way to go.

[Petros]

the 4afe has a cross flow head and the distributor off the back of the cam, which is a problem for the Tercel unless you either go distrbutorless (which adds costs) or cut a hole in the fire wall right where your heater is supposed to go. Putting the 4age head solves the distributor problem, but you still have to rig the induction and exhaust system.

if you want a little more 'juice' from the 3ac engine, go with the Delta Cam regrind and a weber if your emissions laws allow it.

[Tercel__jon]

-facepalm- I had two threads open at once and posted to the wrong one....lol

[teranfirbt]

All things considered, if you're going to spend the time/money to do a twin cam swap into a Tercel, it's worth the effort to make EFI work with the car. It's not that difficult to add an EFI pressure fuel system, and the exhaust system has the same issues as a cross flow engine setup that will bolt up to the stock bellhousing.