20V

Here is some 20V install info courtesy of Daryl Munro and Dave Spinnetti


 
From Daryl Munro

Hi. Congrats on a great site. You (and your readers) might be interested in the following comments
from a New Zealander who has installed a 20v into an AW11, and races it regularly, although it is still road-registered, and used for cruises from time to time. The transplant was simple and straight-forward, and created no headaches at all.

Following the order of your comments:


 
  • As I understand it, the 20v 4-AGE was a Japanese domestic market only version. They are reasonably plentiful here as we import a lot of used Japanese cars (we are still right hand drive), and parts. After the original 16 valve engine blew its head gasket comprehensively, it was a simple decision - rebuild it at a cost of over US$1,000, or transplant a 20v at a similar total cost, but with some horsepower advantages (in stock spec), and incorporating an adjustable computer. The 20 v engine itself was US$500.00 - the balance made up of the Link Computer we installed, which is fully adjustable. I paid on the high side for the engine, because it came from a car which had a guaranteed mileage of less than 20,000 miles.

  • I am not sure what you are getting at in respect of the EFI system. The 20v engine was complete, and we used all of it in that form. The VVTi is controlled by the adjustable computer. We have lowered the revs at which it comes in to 2,900, and that makes it go real well. But, that is about engine management, not the EFI system.

  • The problem you mention about the starter is one we didn't strike. The 16v had headers, and they fitted straight on to the assembly without problem. We are about to re-use the factory headers to see whether that gives more torque, and maybe will strike the problem then. I can't see how it will, though. Essentially, everything just bolted right up, and after almost a year of racing and driving it, nothing has rubbed, chaffed, broken or fallen off. You are right in that the attachment of the headers requires a modification - the outer bolts are in different positions. But, this takes a competent welder about 5 minutes to rectify.

  • Water lines. Yes - they are different, and you are quite right - creative use of waterlines overcomes. And, it took all of 30 minutes to do it.

  • Oil cooler. We didn't strike this problem.

  • Distributor. Yes, the distributor had to be modified. We made up a "combo" dizzie, which took about an hour, and has worked perfectly since installation.


Is it all worth it?  For me, yes. With a stock engine (apart from headers and a lightened flywheel - oh, and we removed the aircon pump, etc) I now have 110KW (145 bhp) at the wheels which translates to something like 170 bhp at the flywheel. I race against purpose built racecars such as supercharged Corollas, and regularly beat them. It is usually assumed that my car is turbocharged. 
And, even better, I have reliability. For this car, race preparation consists of checking the oil and water level (I have not yet had to add anything) and tyre pressures. I was, for example, the only competitor in a recent open class one hour race who drove the car 120 miles home afterwards - the rest went home on trailers. I beleive that you are right about the ultimate development power
outputs - the 16v in formula atlantic form currently achieves 240 bhp. I don't know of anyone who has reached that with a 20v. The reason seems to be that the 20v was a Japanese domestic market only engine, and no-one has worked on it. But, it will produce 170 bhp all day long in stock form. BTW - it has 25 more ft/lbs of torque, and revs at least 1,000 higher than the 16v. We set the rev limiter at 8,700 revs in my car. 10,000 revs are possible, but I find that in practice there is little point
in exceeding 8,000. My AW11 will comfortably exceed 100 mph in third gear (stock original box and diff). I can source 20v engines for anyone interested. I don't know shipping costs, or import charges, but the basic complete engine cost would be about US$500.00.

Cheers
Daryl Munro

 
 


 
Dave Spinnetti:
 
 

20v Levin engine installation notes

 Comments:
The conversion of the stock 112hp MR2 to the 160-165hp (depending on Map/AFM type) 20v is a reliable way to significantly boost power in the MR2, adding 15-20hp over the 4agze motor, with a neater, less cluttered engine bay with weight savings as well. This is not a particularly difficult installation, but it is time consuming and the electrical modifications are daunting if you are not experienced in automotive wiring. Do not attempt this unless you are comfortable doing plenty of welding, fabricating, soldering, trouble shooting etc. I removed the A/C from my car, so the installation was simplified quite a bit, both mechanically and electrically.
 

This outline assumes the following:


 
  • No A/C. If You want A/C, it requires plenty of extra work, but the same techniques apply.
  • Wiring harness will contain no extraneous wires or circuits.
  • The completed harness will look as good or better than the original harness.
  • All functions including the gauges and check engine diagnostics will work correctly.
  • All mechanical functions and connections will be as good or better than the factory produced.
  • The 20v motor comes complete with ecu, engine wiring harness, and some of the body harness. If there is no ECU, you will have to integrate an aftermarket EFI system to the motor.


Mechanical notes:

  • Remove the old motor (with engine harness still attached), transmission and wiring from the engine compartment and put it side by side with the 20v. This makes the swap over of functions much easier.
  • Many of the vacuum tubes on the back of the 20v motor can be blocked off. There is one available that works nicely for the brake booster, which now will route on the back side of the motor with the other lines. The motor lifting hooks and all the associated vac. plumbing on the rear hook can be removed once the engine is in place.
  • Use the front motor mount from the MR2 (2 bolts, 1 stud) as opposed to the 20v mount (2 bolts). This seems to be a little sturdier, but you can make the 20v setup work too.
  • Use the crank pulley from the MR2 and timing belt tensioner bolt from the MR2. The timing mark location on the 20v is not easily visible unless using the original MR2 pieces. While you are at it, replace the timing belt.
  • Use the alternator bracket from the MR2. This is simpler and lighter than the 20v version, which has an additional idler pulley.
  • For the exhaust, you can use the header that came with the 20v if you also have the 20v bell housing which mounts the starter on the  intake side. Note that the down pipe may be very hard to get, and fabricating one is complicated by the lack of an available flange to bolt to the header. Alternatively, the crappy TRD header will work, but the flange mounts needs to be lengthened for the #1 and #4 cylinders so it will bolt up. This will require good welding and fabricating skills, or a good shop. The following photos show what it takes to make it  work: cutting off the outside 'ears' and rewelding them out further. I just used about 12" of pipe and a stainless steel Supertrapp welded to   it for my 'Exhaust System'. This proved to be way too noisy, so I used sections of 2" pipe and a free flow muffler to weld up a custom system.
  • The 20v motor did not use an oil cooler, and it may not need it, but its still a good idea, and routing the coolant lines away from the exhaust is simplified.
  • Use the Oil pressure sensor from the old engine. The 20v sensor is a different voltage range and will not drive the dash gauge properly.    Later MR2's may use the later sensor, so this may not be required. It is easy to tell the difference between the sensors: the old one is about twice the diameter of the new one. If your old and new sensors look the same, you will most likely not need to swap them.
  • The coolant overflow tank will no longer fit in the stock location, so move it or replace with a smaller unit which will fit the space (a 81-84 Starlet tank works great in the stock spot).
  • Reroute the cooling system connections. Actually, the 20v configuration is better than the original. All the connections come off the back  of the motor. Mount the filler neck towards the back of the motor near the fire wall. It took me quite a bit of experimentation before I was happy with the job. I ended up using 1 1/4" od .065 6061 aluminum to connect sections of hose and for straight runs.
  • The fuel line from the fuel filter to the engine needs to be 2-4" longer, or move the filter so it will reach. I was unable to get the correct   fittings to make up a new fuel line (such as Aeroquip or Earls), so I spliced together half of the original line and half of the 20v line to get what I needed.
  • The throttle cable is at least 4" too short to work well. A cable should be made up which is 1-2 feet longer so it won't hang across the top of the motor.
  • If installing the motor in a formerly supercharged car, make sure the intake plenum is bolted on the engine before you install it. The right  side allen head screws are difficult to access due to the placement of the engine cover latch. The engine cover latch also needs the bottom 1/4" or so ground off so it won't contact the intake plenum.
  • If you want to keep the 20v starter on the intake side of the motor, and/or want to use the factory header, you will need to mate the bell housing section from the 20v transaxle to the original MR2 transaxle. You will also need to replace the speed sensor with the speedo  drive from the MR2. This is a good time to replace the syncros or in general service the transaxle. Most likely, you will want a shop to do this part.
  • The motor and transaxle bolt up differently on the 20v than how the MR2 is configured. The 20v uses a fairly large aluminum stiffener to   attach the engine to the bell housing. If you are using the TRD header, the stiffener will not fit. This requires that the right rear engine (to  transaxle) mount be drilled out so that the large bolt can pass through it and thread into the transaxle (this hole was not used for the 20V).
  • Use the full back plate (behind the flywheel). If using the TRD header as it will help secure the engine and transaxle together better than if using the two piece plate from the original motor.
  • The 20v flywheel is like the late model MR2s. Any years flywheel and clutch will work, but they need to be used as a matched set due   to variances in the clutch diameter. I used the HKS/TRD flywheel (and metal/ceramic clutch), which is of the same diameter as the 1985 flywheel, and is the lightest steel flywheel available.
  • Replace the Timing belt and belt idler if needed. The 20v motor uses a 111 tooth timing belt as opposed to the 112 tooth belt of the MR2. The distributor cap and plug wires also may be a problem to get.
  • You can use the original O2 sensor, or get a generic 3 wire sensor to mate to the 20v harness. There will be a 4th wire left over.
  • Here's what mine looked like when I was ready to put it in (after a little custom paint, K&N breather and bolting on the HKS/TRD lightweight flywheel):

Electrical notes - The heart of the conversion:


 
  • To do this correctly, it will take lots of time - be patient and make sure you know what each wire is for, or you may ruin the ECU,  which is probably irreplaceable. If you start to tag everything you know on both the 20v motor and the original, the remaining wires are a lot easier to figure out.
  •  Decide which accessories you will use - this will also determine how much of the 'old' engine harness you will need for the new motor. I   used the main battery and power supply wiring (to the starter and to the body) from the old harness, as well as various bits and pieces where convenient.
  •  It is not necessary to remove the 20v harness from the motor, or to strip down the wiring which goes to the injectors.
  •  Some relays/functions are in different places, e.g. the starter relay is mounted on the transmission for the 20v and in the fuse box for the MR2. This will take some figuring and tracing of wires to hook these up correctly.
  • Remove the wiring harness from the body and lay it out as it would appear in the car - this requires the removal of part of the interior, especially to get the fuel pump wires out.
  • Tag all plugs and remove the complete engine harness from the 'old' motor
  • Tag all plugs and remove the complete rear body harness, including the fuse box and rear lighting wiring. The harness starts on the DR.   side kick panel, goes behind the DR. side seat at the fire wall, to the fuse box and several plugs in the engine compartment, and finally to all the rear lighting and a plug near the ECU.
  • Strip all electrical tape and wire protectors off both harnesses, but leave everything in its original shape.
  • Trace and label every wire on both harnesses and match by function (not just wire color as they vary some, and some of mine were different than shown on other published 20v ecu pinouts).
  • Trace and remove (complete preferably) the engine bay cooling fan circuit from the MR2 Engine harness and transfer to the 20v (This is  a simple circuit and easily transferred, but like the cooling fans, this fan is not needed in my car dure to the extra cooling vents in the engine    cover and the reduced load from the significant weight reduction. I have run with no cooling fans for years and never had the temp go over 1/3). The ambient air sensor is on a bracket at the top of the motor close to the firewall on the left side. The Relay is bolted to the ecu. This entire circuit will need to be grafted into the 20v engine harness.
  • Eliminate unused circuits. There are a number of circuits you may not be using (there was an unused emissions box on mine along with   a/c and others), which you can remove from the harness. Eliminating all the unnecessary wiring is a great first step to see what you really need to do and saves about 10lbs.
  • The 20v ignition coil, ignitor pack and capacitor (?) are standard late model Toyota parts. You can also just clip off the connectors and attach the old type connectors in order to use the original coil, etc.
  • There are only 3 plugs that connect the engine harness to the body (2 gray plugs under the fuse box and a square white plug in the   trunk). Now that all the wires are labeled, it is fairly easy to match the 20v harness wires to the MR2 body harness. For now, just twist  the matching wires together and put some tape on them to keep them from falling apart. Note: Most of the wires will match in color/stripe, but not all.
  •  On my motor, I had a few plugs that were not immediately obvious what to do with like the speed sensor connector and the MR2s injector resistor pack. The 20v car used an electronic sensor instead of a speedometer cable. This connector goes to another mystery connector, which is a Black, 2 row 22 pin connector with only 9 or so pins used. Most of these pins map to the square white plug in the trunk, and some are just eliminated. The MR2 uses a big aluminum resistor (for the injectors) that mounts on the battery support bracket.  The 20v motor does not require this resistor, so it can be removed. The 'INJ' relay in the fuse box is also no longer required.
  • The original 20v wire routing will work pretty much as-is on the MR2. This will end up much neater than the original MR2 rear harness and eliminates the wiring going through the passenger side trunk area. The ECU connections will be mostly all set to go. The tedious part of the job is getting all the ancillary functions swapped over.
  •  The ECU will now mount on the driver’s side of the trunk instead of the passenger side. Make up brackets to hold it securely - vibration can easily damage the ECU.
  • After all the wiring is done, and temporarily laid in the car, adjust wire lengths and solder everything together and put all the wires in looms.
  • For ultimate neatness, shorten the trunk harness to adapt to the new ECU location.