Japanese MR2 turbo information: practical information and tips

Oil filter

Toyota part number is 90915-10004 and costs about 6 pound (June 2000). Toyota part has an anti-drain back valve to assist cold starts. Position of the oil filter moved from top of engine to bottom of engine for revision 3 (maybe the anti-drain valve isn't an issue for the later cars?).

Coolant

Ethylene glycol based anti-freeze with corrosion inhibitors suitable for aluminium engines mixed with distilled or deionized water. Use 'Toyota Forlife' if you wish, but you don't have to according to any Toyota repair manual I've ever seen, although bear in mind coolant manufactuers say not to mix different brands of coolant. Use of radweld is probably a very bad idea. Deionized water is available for as little as 2 pound for 5 litres in good car part shops and is definately worth using when you consider the coolant litterally boils in the turbo when the engine is switched off and the pipes leading to and from the turbo are only a few millimeters in diameter. (Add 200ml of tap water if you want to be cautious about the corrosive properties of large volumes of super-pure deionised water.)

Those unfamiliar with MR2s should read the appropriate section in an MR2 engine repair manual describing coolant filling procedures. Bleeding the air out isn't rocket science, but air-locks are a common cause of overheating problems, which could be very serious especially considering the turbocharger is watercooled. Its not a job a DIY mechanic should fear though as long as they are pretty cautious that air-locks sometimes happen. (Warning: never use a mains voltage inspection lamp under the car when draining the coolant).

Removing trim

Plastic fasteners that are used to hold in trim such as the carpet in the boot can allegedly be removed by pressing the centre in. This is a useful thing to realise as Toyota allegedly charge 90p each for them.

Known problems

Solid, non-metallic paint fades somewhat.
Rear boot can let in water, probably from water sprayed off from rear tyres onto wheel arches and underneath of car, rather than leaking from the top.
Toyota CD players may spit out CDs.
Wipers may have problems staying smoothly on the screen when being used at high speed, regardless of brand or whether they have the little spoiler thing or not. Stiffer spring tension in the wiper arm is thought to help.
Radiator drain and bleed valves may start leaking, requiring the O ring seal to be changed.
Catalytic converter cores can start to break up after a few years and can block the exhaust somewhat, leading to poor performance and poor fuel economy.
Old / contaminated clutch fluid can cause problems when it gets warmed by engine heat. If the clutch pedal acts improperly, try changing the clutch fluid first of all.
Front fog light screws are reported to be prone to corrosion related seizure. Might pay to grease them up, before you need to replace a bulb.
Engine number is virtually impossible to see whilst engine is in the car.
Coolant header tank level is difficult to see. Shining a torch down the neck in the dark might help, but you're probably better just using a piece of tube to gauge the level - push it down the neck whilst blowing down the other end until you hear bubbles or something.
Petrol filler cap can sometimes get stuck on, requiring some sort of implement like an adjustable spanner or an OEM toolkit wheel chock to remove.
'Transmission tunnel' coolant pipes of certain model years can crack due to bad bracket design.
Power steering relay contacts oxidise causing power steering to stop working and the light to illuminate on the dash. Switching the ignition on and off multiple times usually fixes the problem at least at first.
Rear ABS speed sensors can seize solid into holes with the slightest amount of corrosion. If you can manage to get them out, grease the hole up. Front ABS sensors are of a different design and should be ok.
Rear ABS rotors are open to bits of debris getting in leading to iron fillings getting stuck to the end of the speed sensor degrading the quality of their signal to the ABS system, possibly effecting performance or causing the car to pull dangerously to one side.
Cam cover bolts tend to loosen and should be retightenned to prevent oil leaking past cam cover gasket.
10mm head screws holding plastic untrays are slightly unsatisfactory: if you don't grease them up they can seize in and snap when undone, if you do its all too easy to overtighten them stripping the thread in the body or cracking the plastic undertray.

Speedometer accuracy

Speedometers often may be a little inaccurate. The repair manual for the UK car says the allowable reading at 100 MPH is 104 to 108.5 MPH, i.e. they are designed to over-read. Also needles may be placed in the wrong position if speedo faces are changed etc, as zero is alleged to be behind the stop. As far as I can establish so far, each 1100 rpm in fifth gear corresponds to pretty close to 25 mph with standard 225/50 15 rear tyres. E.g. 2200 rpm is 50 mph, 3300 rpm is 75 mph, etc.

Turbocharger

Revision 1 and 2 cars use the Toyota 'CT26' turbocharger, whereas revision 3+ use an alledgedly slightly smaller turbo that's popularly known as the 'CT20B' (the CT26 has 'CT26' on the compressor housing, but I don't know what the source of the 'CT20B' name is). The turbos are made by Toyota which reduces the amount of turbo rebuilders that deal with them in comparison to manufacturers like Garrett who 'approve' rebuilders. Rebuilt CT26 are probably a lot more readily available than the less common CT20Bs. The CT26 has six studs on the exhaust outlet, the CT20B seven, although I gather people interchange them by removing the extra stud.

Original turbos on Japanese MR2s use ceramic exhaust turbine wheels, rebuilt units will use some kind of steel instead - the amount of difference this makes to turbo lag is unknown to me. The ceramic turbine wheels are absolutely slated by turbo rebuilders as being unreliable, but I've not really heard any first-hand accounts from MR2 owners which back this up compared to turbos failing for other reasons such as wear or the oil seals going, and in my experience the ceramic CT20B will stand very heavy use at standard boost pressure; it will just wear out a lot quicker than with normal use. It does however sound like Toyota use steel not ceramic for the UK Celica GT4 turbo, but not for Japanese Celica GT4s (well a 1994 Japanese ST205 had the exact same part number as my revision 3 turbo at least).

I also found it unclear whether other aspects of rebuilt units will be the same as original spec, such as whether the turbine and compressor wheels are matched to the original. One turbo rebuilder had problems obtaining the shafts used in the CT20B but solved this using a thicker one, others may readily try to sell you a CT26 with no mention of any downsides. None of this is an issue for people that wish to have their turbo upgraded in order for it to run higher boost pressures, but there may well be a noticable penalty in responsiveness compared to a turbo highly matched to an engine (and vice versa) by Toyota's extremely large research & development budget.

For price comparision purposes, Turbo Technics and Fensport wanted about 700 pound (inc VAT & carriage) for an exchange CT20B unit ('Turboforce' are also worth speaking to) whilst the list price for a brand new unit for a revision 3 from Toyota GB is 1032 pound (excluding VAT, excluding any discount) (Aug 2005).

A possible myth that exists is that you can check the condition or a turbo by feeling the amount of play on the compressor wheel by hand. A brand new turbo has loads of radial play if not axial play and the service limits for both I think are generous. The real issue is probably whether the wheels are rubbing on the housings, or if they've gone out of balance. You might not be able to feel play in a used turbo because of oil film or something.

Tyres

Revision 1: 195/60 14 front, 205/60 14 rear.

Revision 2 onwards: 195/55 15 front, 225/50 15 rear.

These sizes give about the best handling, deviate from them with caution. Minimum speed rating is V. Yokohama were fitted as original equipment and rumour has it Yokohama designed a tyre specially for the MR2. Bridgestone S03s, a once popular choice with UK owners, are no longer available in standard MR2 sizes (Jun 2005) leaving Goodyear Eagle F1 GS-D2s or Toyo Proxes T1-Rs as the most recommended options from owners. Sourcing a specific pattern in both sizes can be frustrating.

Your door sticker should give you more reliable information. Generally you can fit better or, within reason, bigger, but using smaller than the manufacturer's recommendations is probably illegal and may affect your insurance.

Note that theres a particular kind of clip on balance weight for the OEM wheels, probably something to do with European verses Japanese car makers. An uncaring tyre fitter can manage to hammer the more common kind onto the wheel, and it will probably stay on, but it won't fit very well or look right. Note ideally for perfect balancing you'll probably need weights on both the inside and the outside of the wheel. You may still want to request they only use one weight on the outside (as opposed to 2 or 3 smaller ones) for cosmetic reasons. Adhesive stick on weights have a reputation for falling off, but are an option for the majority of tyre dealers that don't seem to have the Japanese weights.

Tyre pressures

According to the Toyota manuals for the U.K. car:

14" Wheels: 29 PSI (200 kPa) front, 32 PSI (220 kPa) rear.

15" Wheels: 30 PSI (210 kPa) front, 35 PSI (240 kPa) rear.

The Japanese door sticker on my revision 3 turbo seems to specify 2.0 Kg/cm2 front, 2.3 Kg/cm2 rear. By my calculation thats 28.4 PSI front, 32.7 PSI rear. However I don't see any reason to use lower pressures than the UK model which is lighter and slower, assuming the speed limiter on the Japanese car isn't operative. 4.2 Kg/cm2 (59.7 PSI) seems to be listed for a 135/70 16 tyre, which I presume is the compact spare? Please note my use of the word seems, I can't read Japanese.

Wheels

Front: 15x6 JJ 45 Rear: 15x7 JJ 45

- or at least those are the numbers cast into my stock toyota alloys on my revision 3 turbo. (Revision 1 is different with 14" wheels.)

Currently the second hand value of original toyota MR2 15" alloys is less than 150 pound, probably due to the amount of people fitting 16" and 17" aftermarket wheels for their cosmetic appeal. OEM 14" wheels are virtually given away, sadly.

Note 14" wheels wont fit on the front of revision 2 onwards because of bigger brake disks. Similarly compact spares from revision 1 wont fit later cars. A standard 15" OEM front alloy wheel will fit on the rear of revision 2 onwards cars, and seems to work fine for emergency use but bear in mind that its probably illegal and may affect your insurance even if it probably is a lot safer than a compact spare. A standard front 15" alloy plus tyre weighs about 16 kilograms.

http://www.mr2turbo.info/