Toy Motor

Supragal Class One Homer And a special thank you to our last minute draft in: Alex

Those that were indeed in on it: IanC tDR Branners Mawby whitesupraboy

APRIL FOOLS!!!! Yes, that's right folks - it was all an elaborate hoax dreamed up by us mods to top previous April Fools gags. Bob.

It's fine by me if people wanna bury their heads in the sand. Forget I ever mentioned it! I knew this would just worry people... Bob.

Sorry if folks think I'm taking the piss. I was asked to share info on this so I did. I really am not too bothered whether you believe me or not but I do draw the line at being called an outright liar I'm not saying these failures are guaranteed, just what I expect to happen, with evidence garnered from my work and personal experience of these cars. Mods could you please lock this thread as it's only causing bad feeling and dragging my name through the mud Bob.

Dunno, never tried it I just drove the damned things. Hard. lol Supra-Man - you ain't wrong there! Bob.

To answer Ian and others, We had a target number of operational hours for each test mule. Of these operational hours, we worked out an average in real world conditions that each component or part of the vehicle would see X, Y or Z stress levels. We concentrated on the Z stress loading, Z being full operational load. Testing was done on the real road and non manned simulated testing was also completed on test 'rolling road' rigs which were fully motorised and servo'd to mimic driving over different surfaces, corners etc. Retro fitting a non LSD would alleviate the situation, yes. Extra welding was implemented to extend the floorpan and chassis life in this area beyond any warranty period and potential legal liability period - that being 12+ years. Further durability testing after the modifications put the lifespan to 15+ years which was more than expected, so quite a result, really. Any further welding in that area just moved the point of fatigue failure to a non-reinforced section. By increasing the size of the rails and mounting areas the issue could have been removed entirely, but if you recall, the design brief for the JZA-80 was to be as light as possible. So around 16kg was saved by simply increasing the weld thickness rather than the subframe mounting point size. Management figured that a 15 or so year lifespan was an acceptable tradeoff for keeping the weight down. Bob. p.s. I'm really really sorry to have brought this into the open Please forgive me! I think I'll just not talk about my time with Toyota anymore.

I honestly don't know if there were any improvements made throughout the life of the model Sorry! I left in early '95 during which Supra sales were extremely strong. It was my favourite project from my time there. Bob.

I agree, such an item would only accelerate the fatigue by transferring a greater amount of the operational load to the floorpan. Bob.

Hi Digsy, Nice to meet someone else so involved in such work! Who are you working for? I didn't get involved with the engine stuff myself, I think most of the long term testing and the 'abuse' stuff was done on a dyno cell, although we did get to test the oil sump baffling thing which stops oil starvation on hard turning. I do recall spending a couple of days with another guy, Stuart, going round and round as fast as possible, thinking about it still makes me woozy today lol but at least I was the one driving, he had a laptop to control as well and back then they were as big as a chest freezer hahaha! We did actually break one doing that - the pickup didn't pick up the oil, and suddenly the engine went tight, lost power, and wouldn't restart after we stopped it, nasty. I had to click on the TVD link before I knew what you meant! That's a cool feature of the site by the way! Yes the pulley fell apart, they normally did at about that mileage, probably a few thousand either side, although it depended on if it was an auto or a manual and the way people drove the manual (one day spent deliberately changing down so it hit the rev limiter, honestly, if you had much mechanical sympathy before this job you wouldn't afterwards!). They are just a bit that wears out, 100k miles between component swaps was OK to the bean counters - well out of warranty and they figure a sodding great squeal would get people to the garage before it fell off! As for the strength of the engine, I don't know. I think we fixed all the dodgy bits with parts that were such a leap up from the ones that were the weakest link (goodbye!) that it accidently ended up really strong. I know I threw a conrod once on the downshifting / overrevving stuff, the rod bolt snapped. But I really can't help with that. It's a great engine! Bob.

The ST205 model GT-Four has 5x100 PCD hubs if I recall correctly. Bob.

Have you seen the recent tech thread concerning the rear subframe / floorpan? http://www.mkivsupra.net/vbb/showthread.php?t=104457 Although I would think yours isn't quite old enough to show failure signs as yet. Is it LSD equipped? I distinctly remember those sounds under load which tended to lead to diff failure, they were as a result of awkward diff loadings caused by the fatigue. Other symptoms were twisted / warped driveshafts and occassionally props Bob.

Both the SMIC and the rad look in acceptable condition Ben. We did actually trial front mounted intercoolers in the early development of the Supra, albeit with a side mounted rad to go with it! There wasn't a lot in it between the two in 400PS trim but that was comparing to the 400ps trim beefier SMIC which was later cut when the car was detuned to approx 320ps spec shortly before production. So we went with the conventional setup of front mounted rad and SMIC as the production costs were significantly lower - plenty of cores to choose from for both these items but we'd have needed to go bespoke for the other way round. From my experience, a FMIC should give a good gain if you are running a higher boost level than standard. The same goes for a better SMIC because really you just need more cooling area to accomodate more air being present in the IC at any given time under load. With either, cooling will have to be properly addressed and monitored because you are putting more thermal stress on the motor. Bob.

No, they physically won't fit as the bolt holes won't line up. Bob.

Again, thanks for the warm welcome guys! Ian - I've replied to your thread about it in tech. Bob.

Hi Ian, I was hoping no-one would want more info on this as it's likely to cause concern. From my experience in testing and in my ownership, we found that the Supra's rear subframe has a designed flaw in the rear subframe chassis support. After 15 to 16 years the rear shell will fail where the subframe bolts to it. Accelerated durability tests during the development phase showed that the rear subframe was marginal in supporting the rear wheel drive layout with the torsional forces put through it by a limited slip diff. Over time, this twisting action fatigues the supporting areas, fracturing them. Non limited slip diffs never put enough twisting action into the chassis mounts so didn't ever display this issue. If you have retrofitted a limited slip diff then the issue will manifest itself around 15 years after the installation. If you have modified your car to increase the power output, the lifespan may be shortened even further. This is theoretical however as Toyota saw no point in spending R&D money performing durability testing above the stock power output. As there have only been a couple of reported incidents 'in the wild' so far and none in owners' clubs that we know of yet, an increase in power probably doesn't accelerate the process that much. It was, after all, a twist action causing flex fatigue, and not a torque issue causing a bending force. If the failure occurs, it will be under acceleration, probably from a hard standing start as that induces the most shock loading. This is a good thing because the side that fails will collapse to the point that the rear wheel fouls on the wheel arch - not something you want happening at 80mph! This sudden twist can cause the other side of the frame to fail as well, causing the back to drop fully. At this stage in the car's life it's probably not economical to repair, a re-shelling would be required. Trying to re-weld and patch up the affected areas would be seriously inadequate and could fail at any point while driving, thus making it very dangerous. Please don't hate me for sharing this with you guys! I know it's NOT what people want to hear about their pride and joy - as I've already said the MKIV Supra is one of THE most durable and well engineered cars to come out of Japan, and that's saying something! Bob. APRIL FOOLS!!!

Thanks for the welcome Ian - I'm honoured! I've been reading some of your excellent tech posts and tech articles. That's quite a car you've built yourself there! In fact, it's very much along the lines of what we'd like to achieve with Gary's car On the Intercoolers - the original units used in the test mules were actually somewhat thicker and had metal end tanks. When we decided to de-tune the car shortly before production and the corporate bean counters got a whiff of it (always hated those guys - they always managed to turn a pure diamond into a slightly yellow diamond!!), a new and lower priced supplier was sourced to supply the thinner, plastic end tank'd units that the production cars got. We couldn't really justify the previous unit's cost vs. intake charge temperature when running the engines at 320ps tune We knew the longevity wouldn't be the same but still the production units proved adequate and certainly weren't marginal by any means. There were no final production failures on that front that I'm aware of - perhaps it's more of an age thing given the metal material used on the core. Other achilles heels I'm aware of are probably best discussed in a new tech thread? There's the stuff like the heater matrix, front crank seal, the rear subframe mount weakness where it attaches to the floorpan, the early oil pressure senders, the domestic model brake caliper castings, the LSD's and driveshafts as a result of the rear subframe mount weakness, boot rubbers hardening over time causing that annoying noise etc etc. Some of these things we experienced in durability testing, some of it I experienced throughout my ownership. As I've said though, probably best not getting into that in here! Some of the stuff would probably just scare people so don't wanna get too into it and have people worrying as a result... lets just say the MKIV Supra is one of THE most durable and well engineered cars to come out of Japan, and that's saying something! Bob.

Whoa! Busy place this, I didn't expect anyone to get back so quick! Thank you all for making me feel so welcome The model certainly evolved throughout the durability testing and a good deal of thanks has to go to the Soarer in that respect - we used them as discreet test mules mainly in the early stages of development for parts and concept testing including the 2JZ-GE and 2JZ-GTE powerplants and suspension / brake configuration work. The first Supra bodied test mules were heavily disguised but already highly evolved from all the parts testing we'd already done. That rumour about the power output has an element of truth - Toyota badly wanted to blow the opposition away with the release of the mkiv and early 2JZ-GTE's fitted into the Soarer test mules had in excess of 400ps. In the end, they detuned it a little mainly because of the Japanese manufacturers 'gentlemans agreement' that came about meaning a power cap of 280ps. We quoted that figure but really we had to fudge it a little - the production powerplants were producing in excess of 320ps! As far as this whole j spec / uk spec thing I've been reading about on here - they were different cars for different markets. The domestic model didn't need to do high speed stops (well, above 112mph anyways) so the emphasis was on low to medium speed response and driveability. The export market car (which the UK and US got) had an emphasis on medium to high speed GT style driveability - hence the different cams and smaller steel based turbines. Personally I always enjoyed driving the domestic model more - it felt so much more 'alive' on winding roads. As for the over engineered bit - that's partly down to the originally planned higher power output plus Toyota back then always erred on the side of caution to ensure reliability and the safeguarding of their reputation which was in it's infancy at the time, especially following the whole mk3 head gasket debacle. Bob.

Hi everyone, I'm new here so please be gentle!! My name is Bob Cunningham. I used to work for Toyota as a durability test driver and as part of my job I got to work on the Supra from 1991 to 1993 just prior to it’s release. Absolutely loved it and owned one for 8 years - brilliantly engineered with only a few achilles heels which I won't go into as everyone is no doubt aware of them given the expertise on display on this great site. God knows how I didn't find this place sooner - it's certainly a goldmine of information!! Anyways, I Left Toyota in 1995 and now work at an aluminium fabricators as a general manager (yes, much more boring but I'm getting old!). Technically I've driven in excess of a million miles in a Supra if you count the accelerated durability testing ha ha I learned a good deal about that side of things through my ownership and also learned a great deal of engine stuff through talking to engineers when I got the chance. One of my friends, Gary, recently bought one and he’s looking to go single turbo in the near future. However, Gary is so non-techie (mechanically and computer wise!) that I was looking for some advice and so signed up the this forum to help Gary out. Modifications were never really my strong point as everything was, obviously, focussed around stock setups. So here I am to meet you guys and hopefully learn about modding these wonderful cars and also to refresh my memory on maintenance and troubleshooting. Maybe I can even help out being ex-Toyota? Who knows! Bob. APRIL FOOLS!!!