MR2 SW20 Technical Information

Technical Information of MR2 SW20 models.

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Overview:

The second generation MR2 went through a complete redesign in 1989; the wheelbase had been increased by 3.2 inches (94.5 inches), the overall length had been increased by 9.3 inches (164.2 inches) and was 66.9 inches wide. The new MR2 weighed 350 to 400 pounds (2650-2789 pounds) more than its predecessor and had smoother bodylines. The new styling resembled that of a Ferrari (348 and F355) rather than a “space wedge”.

The differences between the AW11 and the SW20 are easy to see. The AW11 was a much smaller and lighter car. Many people regard the AW11 as a much better drivers car because of it’s light weight and agility. The SW2o is arguably a much more beautiful car inside and out. The interior styling is still not outdated and is quite functional. The SW2o was designed to be a bit more comfortable and to fit into the GT (Gran Turismo) class.

A lot of people argue that Toyota “ripped” off Ferrari when they designed the MKII (SW20) MR2. However the concept design was released before the Ferrari 348 or the F355 were released. Many people still refer to this car as the poor man’s Ferrari. There are many kits you can buy to convert an SW20 MR2 into a Ferrari F355 Replica. There are many MR2 Body Kits and some are better than others but I personally wouldn’t waste my time and money to make a car heavier.

The MR2 is one of the last true affordable Mid-Engine Rear Wheel Drive sports cars you can buy.

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Model Differences:

There were two different models offered for the MKII (SW20) lineup here in the US.

• MR2 NA (Naturally Aspirated) – 2.2 L I4 (5S-FE) making 130 bhp, 145 ft-lb (91-92) and 135 bhp, 145 ft-lb (93-95)
• MR2 Turbo (aka GT/GT-S) – 2.0 L I4 (3S-GTE) making 200 bhp, 200 ft-lb (91-95)

There were a few other models offered in Europe and Asia:

• MR2 NA (Naturally Aspirated) – 2.0 L I4 (3S-GE) making 150 – 177 bhp, 129 – 137 ft-lb (90-90)
• MR2 BEAMS (G/G-Limited) – 2.0 L I4 (3S-GE BEAMS) making 197 bhp, 137 ft-lb (I believe)
• MR2 Turbo (GT/GT-S) – 2.0 L I4 (3S-GT 3rd Gen) making 242 bhp (95-99)

There were several options for roofs on the SW20. There was the base model Hard Top (see picture) which has become extremely rare. This model is often the choice for auto crossers and track racers because of it’s reduced weight up top and slightly more rigidity frame. The weight saved up top by having a hard top vs. a sunroof or t-tops is around 25 lbs. Reducing weight from the top of the car is beneficial to the car’s handling because it lowers the center of gravity. The Sunroof (see picture) was a popular option. It had the ability to raise up as a vent or be removed completely and stored in the Frunk or Trunk. The T-Tops (see picture) are the most common models to find. The two tops are removable and can be stored behind the seats. The t-top MR2’s are notorious for leaking when it rains or when you wash the car. This can sometime be fixed by replacing the eccentric rod guides. However most of the time a complete fix require new weather stripping which can be quite expensive. There are temporary fixes that can be found in my DIY Section. There have been a few companies that have made fiberglass and carbon fiber t-tops to help reduce weight, however none are in production currently that fit well. The last roof option was never offered here in the states. That is the rare factory Spyder (see picture) trim. There are very few around but you may see pictures of them from time to time.

There are many visual differences between the MR2 NA and MR2 Turbo models. The turbo models came with the “turbo” emblem in the US on the rear trunk, a fiberglass engine bonnet with “raised” vents (see picture), fog lights (see picture), and an added interior center storage compartment located between the two seats which is often referred to as a CD box (see picture). The turbo also had larger exhaust pipes. This difference is probably one of the least noticeable. All MKII’s came with a staggered wheel setup, which was slightly wider in the rear. The NA and Turbo models shared the same wheels and stagger from 91-92 (14×6 and 14×7) with 195/60/14 tires up front and 205/60/14 tires in the rear. In 1993 the wheels grew in size to 15 inches in diameter (see picture). The new stagger was now 15×6 in front and 15×7 in the rear with 195/55/15 tires up front and 225/50/15 tires in the rear. The larger stagger was implemented to help reduce oversteer (I will comment on later). The turbo models also received seats with lumbar support, adjustable side bolsters, and adjustable head rests (see picture). In the U.S. there are two different chassis codes, SW21 for the MR2 NA model and SW22 for the MR2 Turbo model, as opposed to the usual SW20 reference.

Once you look in the engine bay the differences are quite clear (see picture). Here are examples of 4 different MR2 Motors. The turbo motor is easy to spot. You can see the intercooler piping and the turbo plate on the intake. The BEAMS motor is fairly rare here in the US but you may see one from time to time. Easy to spot because of the big BEAMS writing on it and the design of the intake. The regular NA motor looks pretty plan and you can see the 2200 CC sticker on it indicating the 5S displacement. The last is the V6 swap. Becoming more and more common you will start to see these more and more. The engine looks like it belongs there.

The turbo motors also came with a stock rear x-strut brace as  you can see in the picture. The NA did not come with a stock rear strut brace. TRD makes an after market one that is incredibly strong. You can see it in the NA engine bay picture.

Other differences include the size of the sway bars. The NA ones can vary in size depend on the year and trim but they are generally between 16-18mm. The Turbo sways are 19mm front and back. TRD, ST, and Tanabe as well as some other tuner companies make after market sway bars for the MR2 ranging from 19-22 mm in diameter. The TRD sway bars are hollow reducing weight while the ST bars are solid. The brakes are also different on turbo models. NA models had the same brakes from 91-95. The turbo models had two piston calipers up front with single piston calipers that were shared with the NA’s from 91-92.

Other mechanical differences between the NA and Turbo models include, but are not limited to: Turbo model received an intercooler, a different exhaust system (2.5 in.), a more powerful fuel pump, a larger radiator, larger rear axles which also required different hubs, and a different transmission (E153) vs the NA (S54) transmission. The Turbo transmission (E153) was immensely stronger than the NA’s transmission (S54). The Turbo transmission has been known  to hold up to over 350 bhp and 350 ft-lb. The NA transmission can hold around 200-250 bhp but have been known to fail around the 200-250 ft-lb mark. This strength does translate to more weight. Axles included the Turbo transmission (E153) weighs around 50 lbs more than the NA transmission (S54). The gear ratios on the two transmission were different as well (see chart). As  you can see, the NA transmission has shorter gear ratio to allow it to have decent acceleration with less power. The Turbo transmission’s longer gear ratios allowed it to take advantage of it’s more narrow power band. The turbo transmission does yield lower RPM’s at cruising (freeway) speeds than the NA transmission.

A few extra tidbits about the two engines available in the MR2 here in the US. The 5S-FE was called a DOHC (Dual Over Head Cam) motor. However, it shared the twin cam design the all other “FE” Toyota motors share. Twin Cam means there are two separate camshafts that control the valves, but they are only driven by one of the camshafts. The camshafts are connected via gears attached to the camshafts themselves. The Turbo motor 3S-GTE was a true DOHC motor. Both Camshafts were driven by their own gears off the timing belt. All Toyota “GE” motors share this design.

My advice: If you want a sports car type motor you need to get a 3S-GE or 3S-STE depending on your application. The 5S-FE is in all reality a Camry motor which should never been put in a sports car.

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Year to Year Changes:

For 1993 models Toyota changed the rear suspension geometry for both the NA and Turbo models. The rear toe rods (that control the toe-in of the rear tires) were lengthened by around 6 inches, and the inner pivot point for the toe rod was relocated on the cross-member (see picture). The front suspension geometry very little. The control-arm/strut rod design eliminated caster adjustments. Springs that lowered the ride height at both the front and rear were installed, and the anti-roll/anti-sway bars were increased in diameter (Turbo model only?). The wheels were changed from 14″ diameter to 15″ diameter wheel. The increase in size was mainly to accommodate larger brakes on the Turbo model but all models were fitted with the new wheels. The tire sizes were increased in width at both the front and rear on both the NA and Turbo models.

“These changes to the suspension geometry and tire sizes were made in response to journalist reports in their reviews of the MR2 that the car would ‘snap-oversteer’. As a counterpoint to the snap-oversteer phenomenon of the MR2, other journalists point out that most mid-engine and rear engine sports and super cars exhibit similar behaviour, and that a change to the driver’s response to oversteer is really the problem, and not the fault of the car. A suspension issue Toyota did decide to address was the dramatic toe’ing out of the rear suspension under certain conditions, mainly lift-throttle under aggressive cornering. In any car, braking shifts the weight forward, and acceleration to the rear. Because of the MR2’s exceptional ability to accelerate out of corners due to its rear-drive, mid-engine arrangement, many drivers would apply the throttle too aggressively, too early, gaining too much speed, and inevitably lifting the throttle. This lifting would shift the weight forward while causing the rear suspension to toe-out–the recipe for non-power-on oversteer, or even a spin.” – Wikipedia (MR2 page)

Turbo models received upgraded two piston calipers up front with larger rotors and larger single piston calipers in the rear with larger rotors compared to the NA models. This is a popular upgrade for a couple reasons. It is relatively inexpensive compared to other after market big brake kits and larger big break kits are arguably less helpful in improving stopping power (see Big Break Theory article).

Other refinements in 1993 are a slightly revised electrical system. The speedometer became electronic instead of cable driven. A shorter shifter lever (see picture) and smaller shifter knob were also installed and are a popular upgrade for 91-92 MR2 owners. For the 3S-GTE the boost engine cut sensor was changed to allow for a maximum boost of 17-18 psi, where as the earlier switch that shut down the engine at over 12 psi boost (this can be overcome by simply disconnecting a vacuum line and plugging it). The 1993 model year also offered a Limited Slip Differential (40% lockup) as an option on Turbo models only. The transmission was changed internally with additional dual synchros on the lower gears which allows for smoother shifting on Turbo models. The front lip was also changed to a new shape that increased downforce at the front. The new design resembled more of a splitter (see picture).

The next big change occurred in the 1994 MR2 models when all MR2’s received new round tail lights also called “Kouki Lights” (see picture) and a color-coded center panel. The corner section of the tail lights in the US were red (see picture). However the JDM and Euro models received amber colored corner lights (see picture). The original three-piece rear spoiler was replaced with the one-piece spoiler which attached only to the trunk lid (see picture). The side molding and skirts were also color coded, and the “dot matrix” edge pattern on the glass was replaced with a solid pattern. The steering wheel was also replaced with a slightly smaller one that was shared across many Toyota models. A passenger side airbag was aslo added. The upholstery in the 94 model cars was also updated and has a different pattern than the 91-93 models. Also the front lip became color coded. One other modification that was done was rather subtle. Toyota upgraded the wiper arms from a screw on style to a hook system.

For JDM models in 1996, Toyota added turn signals mounted to the front fenders and the front signals were changed to a clear lens instead of amber like the previous years (see picture). The original side markers behind the turn indicators were removed and replaced with solid molding (see picture). These have become popular modifications made to USDM cars. The 1998 model, known as the “Revision 5″ model, came with more modern looking five spoke 15” Alloy Wheels and a 3 Way adjustable more aggressive “Combat“ rear spoiler. The interior upgrades include: a instrument cluster with red rings, leather shift knob with red stitching and on the JDM Turbo Model Red Stitching on the Leather Seats.

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Common Modifications:

Modifications are not unusual. They include everything from Cold Air Intakes to Coilover Suspensions. Now I won’t get into the theory and practicality of all the upgrades that people do in this article but I will provide links to articles explaining the ups and downs of the different upgrades.

All upgrades are really dependent on what your goals are for the car and which car you have (turbo or NA).

The most popular upgrades usually start with the suspension since the MR2 is generally regarded as a sharp handling car. Also the stock 91-92 springs (which make up the majority of MR2’s in the US) make the MR2 look like a 4×4. Two options for lowering your car are Springs and Shocks or Coilovers. There are advantages to each however most people fail to address the worn parts of the suspension when upgrading. Let’s be honest, the majority of us have never driven an MR2 with a good condition suspension. I have replaced all the ball joints, tie rods, bushings, shocks, springs, sway bars, and end-links on a SW20 and it changes the way the car drives. Stock blow suspensions are far from ideal. If you want to take my advice…invest a little extra money in your suspension and wait on the exhaust and intake.

Now lets talk a little about speed. If you bought an NA it either because you wanted a light weight, nice handling canyon carver, or you couldn’t afford a turbo. If you bought a turbo it’s because you want a fast sports car and probably fancy boosting your way into oblivion. Whatever the case is…you work with what you’ve got. The most popular upgrades for NA’s engines are Cold Air Intakes (CAI), and Cat-back exhausts. Now lets talk about the reason behind this. I won’t talk about the benefits or lack there of regarding these upgrades. However I will say that if  your goal is to increase HP you will have success to the tune of maybe 5-10 BHP (whoop-di-doo). If you look at the cost of an Cat-Back (~$200-$500) and a CAI (~$50-$150) you have paid between $25/hp up to $100/hp. What kind of a difference will that make in real life? It’s pretty negligent in all reality. What I want everyone to understand is that if you have an NA MR2 with a 5S-FE it’s not going to be very fast without dumping a good amount of money into it. Now if you want something different and want to make a lot of work for yourself then go head and spend money on it. If you want to save yourself time and money simply do a Turbo or V6 swap which I’ll discuss later. CAI and Exhausts are good for making the MR2 sound better and look a little cooler, but in my opinion kind of a waste of money. Now Turbo MR2’s are a completely different animal. The HP potential of the 3S-GTE is amazing. Now the stock turbo (CT-26) is a piece of crap. Most turbo cars are limited by this initially. Even though the stock turbo is rather poor, it can still be helped by some simple upgrades. The easiest way to up your performance is with a boost controller. Next big upgrade would be a Down Pipe and full exhaust. A new intake might be next. After that you get into Turbo upgrades, upgraded intercooler, new injectors, stand alone, etc. I’ll explain more about those in other articles.

Now the MR2 has been blessed with aerodynamics about as good as a shoe. The car becomes rather unstable above 80 mph (I do not endorse doing this on public roads) because of the airflow under the car. The rear spoiler is actually functional however mildly. The drag coefficient is rather impressive but doesn’t really mean a lot to stability. Upgrading the front lip to a 93+ does assist some with the aerodynamics. Lowering the car can help as well, however most people won’t notice the short falls of the airflow. One of the biggest upgrades you can make to the aerodynamics are flat under body panels.

Brake upgrades are my favorite cause I think slowing down is more important that speeding up. Brakes can make you faster and you can read about that in the Big Brake article. Most popular upgrades are 91-92 Turbo calipers for the NA’s and 93+ turbo brakes for both turbo and NA MR2’s.

Wheels can be an upgrade. They can allow for bigger brakes and reduce rotating mass depending on the size. More details in why wheel tech article.

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Engine Swaps:

Engine Swaps are fairly common in the SW20 MR2’s. The engine bay can fit everything from a little 3S-GE to the hefty 5VZ V6 from a Tacoma. The most common swaps are simple 3S-GTE motor swaps which are pretty much plug and play. Other common swaps include 3VZ-FE V6’s as well as 1MZ-FE’s and now the powerful 2GR-FE motor.

Is it possible to fit other motors into the MR2? Yes of course…anything is possible with enough time and money. Is it practical…no. People frequently ask about putting 2JZ-GTE supra motors in the MR2. Simply won’t work without MAJOR work…and even then I’m not sure. I have seen someone put a 2JZ in the front of an MR2 but that kind defeats the purpose of having a mid engine car. The 2ZZ motor that is in the Celica GT-S and the Lotus Elise is a common motor to be asked about. This is a great motor to swap into the newer MR2 Spyder, and fairly straight forward. The SW20 on the other hand is just too heavy to really take advantage of this motor’s strong points.

I’ll talk a little about the benefits of the different motor swaps and will include some write ups on how to perform some of them in the future.

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Thanks For Reading!

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