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Discussion Starter #1
Hi,

I recently came across a Mk3 Supra for cheap, and since I always wanted an old Japanese turbo sportscoupe, I couldn't pass it up.
I'm not really knowledgeable about Supras, and looking for some advice. I'm not chasing extreme power - 550bhp at the very most, but I'd be a happy man with 300-350 as well. I'm looking for a car that's fun to drive, not a car that goes as fast as possible in a straight line.

First, the downsides:
  • It has a fair bit of miles (120k), all on the same engine without any major revisions as best I can tell
  • It has had at least three other owners
  • It sat for almost a decade without being driven
  • It has an automatic transmission
Now the good stuff:
  • Not leaking any oil
  • Recently made ready to run and seems to drive fine by the previous owner
  • Previous owner had it for almost 20 years
  • Engine sounds healthy
Eventually, I would like to swap the transmission and maybe change the engine, but that's an expensive project and will have to wait (I'm working on another car that needs my time and money more urgently). For the short term, I just want to make it run well and fun to drive with the current driveline.

So my questions are:
  1. Any important points of failure I should check? Or preventative maintenance other than the generic oil/brakes/coolant?
  2. Any easy mods that I could make that would improve the feel/handling/power of the car substantially?
  3. How much power could the automatic gearbox handle?
  4. I probably want to do some mods to the turbo system (better intercooler, boost controller, dump valve) - anything gotchas I should be aware of there?
  5. How much boost can I safely put into the engine without touching the internals? I've read that the fuel cut happens at 14-15psi with these cars, is it safe to run it at these levels?
  6. Should I replace the head gasket or cams to get good power out of the 7M?
Thanks,

D.J.
 

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Wow looks like you got a nice car! Here's some common fail points and general maintenance I would do:

Head gasket: If you want to push power out of the car, I would highly recommend replacing the head gasket with ARP head studs torqued to 72lbft. It's a very common failure as toyota did not torque it down enough from factory.

Vaccum lines: The 7m is a great motor but can be fussy about vaccum leaks. Follow your hoses and make sure none are leaking or broken.

Oil Pump: This has not personal happened to me (I have a NA), but I have heard the oil pump is not strong enough to properly lubricate the engine. I get a new one to be safe and possible a relocation kit.

Lastly, I would say change your fluids especially because the car is sitting. Make sure they all come out a nice color or you may have some problems.

I don't know how much power the automatic can handle but if you are going to manual swap it, go R154 as it can handle 700hp as apposed to the w58 which can only handle 300hp
 

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Discussion Starter #3
Wow looks like you got a nice car! Here's some common fail points and general maintenance I would do:
Thanks for the great tips! I'm not familiar with the 7M platform, but on other engines of the era (3S specifically), the Toyota gaskets are high quality MLS OEM - is this also true for the 7M or should I get an aftermarket gasket?

I don't know how much power the automatic can handle but if you are going to manual swap it, go R154 as it can handle 700hp as apposed to the w58 which can only handle 300hp
Yes, I was looking at Supras a year or so back (among other platforms) when looking for a project car, before finally getting an MR2, and most models down here are NA w/ W58, so I read about those limitations. Very similar story with the MR2 & S58 vs E153 transmissions. That said, the transmission and/or engine swap is years out, and I might just leave it as is if I turn out to like the 7M.
 

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Thanks for the great tips! I'm not familiar with the 7M platform, but on other engines of the era (3S specifically), the Toyota gaskets are high quality MLS OEM - is this also true for the 7M or should I get an aftermarket gasket?



Yes, I was looking at Supras a year or so back (among other platforms) when looking for a project car, before finally getting an MR2, and most models down here are NA w/ W58, so I read about those limitations. Very similar story with the MR2 & S58 vs E153 transmissions. That said, the transmission and/or engine swap is years out, and I might just leave it as is if I turn out to like the 7M.
Im not 100% positive about the gasket situation, however someone has told me that the factory gasket is high quality, just not torqued down enough. According to him, factory gasket and ARP Studs should do good for you.

I looked up the maximum hp the auto can handle, and another forum says around 350-400hp so you should be fine unless you want more. To get to that number, I recommend looking up the forum that is a step by step to raise hp for the 7m. With pretty basic stuff you can push 300hp and if you swap a bigger turbo and all the necessary stuff, you can push even more!
 

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Thanks for the great tips! I'm not familiar with the 7M platform, but on other engines of the era (3S specifically), the Toyota gaskets are high quality MLS OEM - is this also true for the 7M or should I get an aftermarket gasket?
The OEM gasket is a composite one and not necessarily good for higher than stock boost levels. The golden standard for head gaskets is HKS, but Cometic (often rebranded by vendors as their own, i.e. Titan) is more than sufficient for your stated goal of 550hp.

Any easy mods that I could make that would improve the feel/handling/power of the car substantially?
A decent set of lowering springs will help with the handling, with coilovers being the best option. Pretty much all of the lowering springs are discontinued so you'll likely have to find a good used set. Alternatively, Tein makes a good quality set of coilovers with adjustable ride height.

I probably want to do some mods to the turbo system (better intercooler, boost controller, dump valve) - anything gotchas I should be aware of there?
A non recirculating blow off valve, assuming that's what you are referring to as a dump valve, can cause the motor to stall out when shifting. Not a tremendous issue, just something to be aware of.

How much boost can I safely put into the engine without touching the internals? I've read that the fuel cut happens at 14-15psi with these cars, is it safe to run it at these levels?
How safe and reliable do you want? The stock bottom end has been shown to hold 700hp with a very good tune on a standalone ECU. Without the standalone ECU you're risking sending chunks of piston ring lands into your head and oil pan.

Should I replace the head gasket or cams to get good power out of the 7M?
Headgasket, yes. Cams, no. Stock cams are good for your power goal.
 

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Discussion Starter #6 (Edited)
Thanks for the detailed feedback! It helps a lot (and of course, creates more questions)

The OEM gasket is a composite one and not necessarily good for higher than stock boost levels. The golden standard for head gaskets is HKS, but Cometic (often rebranded by vendors as their own, i.e. Titan) is more than sufficient for your stated goal of 550hp.
Great info, thanks!

A decent set of lowering springs will help with the handling, with coilovers being the best option. Pretty much all of the lowering springs are discontinued so you'll likely have to find a good used set. Alternatively, Tein makes a good quality set of coilovers with adjustable ride height.
I planned on getting lowering springs or coilovers, becase I personally think the car looks a little silly riding so high stock (those different times, and tastes differ). I went with lowering springs on my MR2 for cost reasons (80 euros for new springs vs 1000 euros for a decent set of coilovers). Those Tein ones look like a great value though, so I just have to save up for them.

How is chassis stiffness on these cars? Is it worth while investing in sway bars or shock tower braces?

A non recirculating blow off valve, assuming that's what you are referring to as a dump valve, can cause the motor to stall out when shifting. Not a tremendous issue, just something to be aware of.
Currently it's an automatic transmission, would that also be an issue with those? I do plan to eventually swap the transmission, but at that point I'll probably be doing more changes to the driveline anyway.

How safe and reliable do you want? The stock bottom end has been shown to hold 700hp with a very good tune on a standalone ECU. Without the standalone ECU you're risking sending chunks of piston ring lands into your head and oil pan.
I'd like to make it as reliable as I can, even if that comes at the cost of power. Towing costs are very expensive where I live ;)

I do eventually hope to go standalone ECU (I don't really want to go through all the wiring hacks for using an A/T ECU with a manual transmission, and a standalone ECU seems like a nice learning experience as well). How much tunability does the stock ECU offer, if any? Can you reprogram the mapping tables somehow?

As I understand it, the automatic gearbox is also electronically controlled by the ECU, does that mean I could wire up a transmission controller and build some paddle shifters into the thing? (Seems a bit silly maybe with only 4 gears, but it's the fun factor...). I'm an embedded software engineer by trade, so I'd like to do some electronics projects on the car as well. (I also plan on fabricating an 80's style digital gauge cluster, like the 300ZX and AE86 had as an option).

Headgasket, yes. Cams, no. Stock cams are good for your power goal.
Great!
 

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How is chassis stiffness on these cars? Is it worth while investing in sway bars or shock tower braces?
Hardtop and targa top with the roof on are plenty stiff, you wouldn't be able to notice a difference with strut tower braces. If you have a targa and enjoy driving with the roof off you'll notice a rather significant amount of flex, and some wobble at speed. Unfortunately strut tower braces won't fix this and you have to go to a couple solutions that aren't widely available; targa braces and the elusive Do Luck rear cross brace.
Sway bars will help take out a bunch of body roll in turns but I would wait to do these as the lowering springs will also help significantly with this. You may find that to be sufficient but if not, sway bars can always be added later.

Currently it's an automatic transmission, would that also be an issue with those?
Typically not, and I complete spaced that with that reply. You shouldn't have to worry about that at all.

I'd like to make it as reliable as I can, even if that comes at the cost of power.
Most reliable would be to Use what the stock ECU will give you. The OEM ECU has a way of changing things looking for the exact signals that it wants, therefor changing any tune you may have done with a piggyback ECU. While this can be fixed by pulling the EFI fuse and resetting the OEM ECU from time to time it just tends to be a pain to deal with constantly. I have yet to hear of a piggyback ECU that truly manages to deal with this properly, and if one did exist it would likely cost about as much as a decent standalone ECU.

How much tunability does the stock ECU offer, if any? Can you reprogram the mapping tables somehow?
The stock ECU is for all intents, un-tunable.


As I understand it, the automatic gearbox is also electronically controlled by the ECU, does that mean I could wire up a transmission controller and build some paddle shifters into the thing?
I am sure it can theoretically be done, but that's well beyond my level of interaction with the autos. I'd just swap to a manual at that point.
Just spit balling this here, but you could interrupt the shift signals from the transmission ECU and put together some sort of computer to take a signal from your paddles to send to the proper shift solenoid on the transmission. Sounds like a lot of thinking to me.
254111


(I also plan on fabricating an 80's style digital gauge cluster, like the 300ZX and AE86 had as an option).
The MK3 had one available for RHD models that have been swapped into LHD model clusters. There's a pretty good thread on it right here on this forum: MK3 Digi Dash

If you don't already have it, here's a link to the Toyota shop manual for the MK3, very valuable resource to have: MK3 TSRM
 

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The MK3 had one available for RHD models that have been swapped into LHD model clusters
Mine is a RHD model (originally from the UK), so I get to pretend to have a JDM one 😅 Interesting, I never saw that dash before. Might still make my own, depending on how easily and cheaply I can find an OEM one.

Hardtop and targa top with the roof on are plenty stif
Mine is just a hardtop (sadly, I love the targa look), so should be as stiff as it gets I suppose.

I am sure it can theoretically be done, but that's well beyond my level of interaction with the autos. I'd just swap to a manual at that point.
Just spit balling this here, but you could interrupt the shift signals from the transmission ECU and put together some sort of computer to take a signal from your paddles to send to the proper shift solenoid on the transmission. Sounds like a lot of thinking to me.
I guess. Not on the "urgent" list for me anyway. What document did you get that description from?

Most reliable would be to Use what the stock ECU will give you.
Can the stock ECU properly take advantage of better intake/exhaust/intercooler or would a standalone be able to work (significantly) better in such a setup? I guess you can always tune a standalone conservatively to keep it reliable.
 

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Honestly, going the modded route is going down the downtime route.

Keep the car OEM as much as possible and that 120k miles is actually the break in period. :)
My first supra lived to 225k miles through snow, cold, hurricanes, torrential rains. It was my trusty steed. Mods where the basic bolt on such as cat back and a greddy TD06. No screwing with piggy backs etc as that is a toss in the air.
 

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Many years ago there was an aftermarktet modification called the "Suprashift " for the 4th gen Supra, and I am 99% positive the 3rd gens also received an iteration of the Suprashift too. Essentially, it was a set up for paddle shifters. Those would probably be a 1 in a million find if you can find one to buy for the third gen because very few made it out to the wild. Trying searching the forums here for verification of a supplier and if they existed for the 3rd gen too. I think this mod was a good 15 years ago. Viel Glück.
 

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If not because something is wrong, it's because you want a little bit more.


How was your drivability with the TD06?
It moved the power band towards the right by about 500rpm but it definetly did not run out of "wind" at higher RPM unlike the CT26 that chokes out arournd 5500rpm. I never really got to open that turbo up past stock (no piggy backs or standalone at that time) though i heard that it will go to 20 psi (450ish rwhp) without issues.

Oh the reason for that turbo, CT26 had failed and OEM prices for new turbo was higher than buying the Greddy kit. This was 2000-ish give or take
 
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