Engine

Drivetrain

Misc

Modified MKIs

To do a major engine mod or swap correctly requires money and lots of it.  While some are able to get away with a low budget project, many times these cars do not have the same reliability and/or craftsmanship that the stock car did.  Heavily modded 4As require after market computers, injectors, pistons, con rods, LSD, dyno time, etc..  As you can see, to do it right requires a great deal of time and money.  Be sure to fully prepare yourself if you plan to go down this road, because it hurts when you spend over $10,000 on a car that is only worth $3000.
 

The HKS Turbo and Twincharger Kits:

There indeed was both a twincharger kit and a turbo kit for the MKI made by HKS. Both have long since been discontinued and are impossible to find. The twincharged 4A-GE is an extremely rare beast, as only 5 or so are known to exist.  It joins an elite crowd of engines that employ both a SC and a Turbo, the positive results coming from the low rpm power created by the SC with the turbo working at the higher rpms.

The Twincharger kit starts off with a MKI SC and basically a turbo kit is put on. Much tuning must be done, as a great deal more fuel is needed, along with many other concerns. Probably the most difficult problem to work out is creating a smooth transition between the SC and TC.  The HKS kit started at the turbo, went to a bypass valve, then to the SC.  The engine would begin to draw air from the SC and when the turbo would spool up, the air would be routed around the SC directly into the engine.  While working well, there are a dizzying array of possible combinations in using the turbo, SC, and one or two bypass valves.  At the high end, an estimated 350+ hp can be obtained with a properly tuned twincharger system out of the 1600 cc engine. 

The turbo kit for the MKI is very similar to the twincharger with the difference being that there is no SC. It too is now nearly impossible to find. The most important piece being the turbo manifold. Properly tuned Turbo systems, can yield approx. 250+ hp.

Check out the Modified MKIs section to find out more.
 

4A-GTE

The biggest problem that one faces when wanting to turbo a MKI is sourcing a turbo exhaust manifold.  While its true that HKS did make one for their TC and turbo kits, these kits are very rare and haven't been available for some time.  While some try and track down one of these manifolds, others deal with the logistics of trying to make a custom one.  There are indeed many shops throughout the US that have the skills needed to do this, but it will be by no means an easy task.  When building a custom manifold not only must one worry about the turbo placement issues, the manifold itself needs to be strong enough to support the turbo (if a brace is not used) and be strong enough to not crack. 

While it was rumored that TRD was making a a Turbo kit for the 4A-GE, this never came to pass.  HKS currently makes a 4A-GE turbo manifold, however it was designed for the AE86.  Because of this, the turbine flange faces upwards, instead of downwards like is needed for the AW11.  There have been conflicting reports about whether or not this manifold will work with the AW11 as the turbine will come extremely close to the firewall.  Even with a small turbo, I wouldn't really recommend using this manifold.

Andrew P. Tasi from the MR2 list has found out the following regarding a turbo manifold:

I spoke with Frank and Sean of South Florida Performance in Miami (305 233-8520) who echoed what their ad in SCC read, they build custom exhaust manifolds guaranteed against cracking. 

Once again, check out the modded MKIs section to see other others have created turbo manifolds.
 

Engine Swaps:

A 4A-GZE in a NA?

This one has been done, and it works great. Steve Bagdon from the MR2 list was one of the first if not the first to do this. Take a look at his page:

4A-GZE in a MKI NA

This has been taken to new levels by Mo Moscovitz and Robin San as they both have highly modded SCs that were once NAs. 
 

4A-GE 20V in an AW11?

This is a very tempting option that has been successfully done but has some things to watch out for.  Worldwide, there are probably around 20-30 AW11s with this transplant.  There are two versions of the 20V.  The "silver top" motor has 165 HP with the "black top" having 170 HP, the increase coming from a different ECU along with the addition of a MAP sensor.  These engines are usually imported from Japan and will bolt up directly with the C-52 transmission and with the stock motor mount locations.  Getting it running however is another story.

An early decision that must be made is weather or not to use the stock 20V EFI which is sometimes very hard to get, or to use an after market EFI system. An after market system with an adjustable trigger can essentially do the same thing that the "i" in the 170 HP VVTi does.  That being an adjustable triggering of the switch that changes the cam timing.

The next major problem that must be faced is where are you going to put your starter?  The stock manifold on the 20V is different from the 16V and protrudes into where the stock starter goes.  The can be remedied by modifying the stock manifold or moving the starter over to the other side of the tranny.  This is only an option if you have a C-52.  The C-52 has two locations where you can mount the starter whereas the C-50 does not.  In addition to this, supposedly you can use the E-51 tranny for this swap.  This solves this starter problem as the starter is already on the intake side.   A 16V header will bolt on to the 20V head, but 2 bolt holes will not line up requiring some modifications.

The next problem to overcome is the water lines.  The 20V was never planned for usage in the AW11 and as such does not have the water inlet and outlet locations that the 16V does.  This can be overcome by creative use of radiator tubing.

If you want to use the stock AW11 oil cooler, the 20V pan must be modified to accept it.  Some who have done this mod say using the 16V pan works, while some say it won't reach.

Finally, there is the issue of the distributor.  I have very little information on this, but have been told that the distributor might have to be modified to make it fit into the Mr2.

So is all this effort worth it?  Well it depends on what you ultimate goals are.  The 20V is actually much harder to get 200 HP out of vs the 16V.  While there are indeed cams from TRD and a bolt on turbo kit from Blitz, there is little else.  On the other hand, the 16V head is well known by many tuners in the US along with the fact that there are hundreds of available parts for the engine, some coming directly from the Formula atlantic engines.  It will also be difficult to source things like water pumps, gaskets, etc.. from Toyota dealers when these parts break. 

Soooo what to do?  If you feel like putting up with the install problems and think that the 55 Hp boost that the 20V gives will be enough to satisfy, the ultra smooth revving, rare 20V is the way to go.  However if you are looking for more power from a known engine for the same price, the 16V is the way to go.  Yes, the 20V can make just as much power as the 16V, it will just cost more to do.  So on the other side of the coin, if you are looking for something even more unique than just the 20V in itself or a 200+Hp 16V, by all means go for it and make a monster 20V.  And when you do, let me know! 

If you going to make the plunge, these 20V Install notes by Daryl Munro and Dave Spinnetti are a must!
 

7A-GE in a AW11?

The first problem to over come is the fact that there was never a 7A-GE.  Rather, there is the 7A-FE.  The 7A-FE is a stroked out version of the 4A used in Celicas and Corollas.  The displacement is 1.8L although the block and internal parts were weakened.  Nevertheless it is quite tempting to think of 1.8L of displacement in a MR2 and as a result some have been able to swap on the head from the 4A-GE onto the 7A-FE, thus creating the 7A-GE. 

More info on how to do this mod yourself can be found at the Celi-News site.
 

A 3S-GTE in a MKI?

This is not a swap for the weak hearted!!  Just a few years ago, this swap had never been done by anyone, but more than a couple have popped up recently.  The first person I heard of that did this swap was Peter Power in Australia.  He gives the following:

I've finished bolting a 3rd generation 3SGE NA into a 1st generation MR2 race car and although it does fit length wise it's not a straight bolt in. The motor I've used is a 1995 Japanese Celica type. I needed to make the timing cover engine mount and a bit of other modifying. The only way I could fit the intake was to remove the boot (trunk) section, I got a bit carried away at this stage and made a one piece fiberglass rear body half so it's easy to pull away to get at the engine.

I've still got a couple of problems with in (it doesn't run yet) but when it's finished I'll write something up if anybody's interested.

To many, this may not seem like "as little modification possible", and you would be right.  As can be seen in the modded MKIs section, there have been more swaps done in a more conventional matter since then.  James Voo was the first in North America to do this, with Deno Pumbley being the first in the US.  These swaps were done using custom made motor mounts, and some require cutting the rear firewall.  Whether or not you will have to cut the firewall will depend on how big of a turbo you want to use, as the turbo sits very close to the firewall in this swap.  A search of the Mr2 mailing lists and Mr2 forums will give you all the information you need to do this swap.
 

Other Combinations?

In having many different variations of the A series engine from SC to Turbo to even both, a great many different and unique combinations can be made.  Here are some more:

4A-GTE 20V: Has been done in Japan for non MR2s.  The performance manufacturer Blitz makes a 305 HP bolt on kit for the 20V.
4A-GZE 20V: Has not been implemented..
4A-GTZE 20V: Has not been implemented.

7A-GTE 20V: Has been done by Ray Hall Turbochraging in Australia

7A-GTE
7A-GZE
7A-GTZE
7A-GE 20V
7A-GZE 20V
7A-GTZE 20V

None of the above 7A engines have been implemented.  The major problem for the turbo cars would be to create a turbo exhaust manifold, while all of the forced induction motors would have to have some sort of strengthened block with larger con rods, etc.. as they come rather small stock.  In the long run however, it is not very economical to try and get great grains from a 7A motor.  The author feels that the most feasible 7A swaps would be the already done 7A-GE and the not yet implemented 7A-GE 20V.  When going to forced induction it would be much easier to start with a 4A-GZE block and to go from there.  If the extra displacement is wanted that badly, I am sure a modified crank can be used in the beefier 4A blocks, rather than toiling with the 7A.