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1992 MR2 turbo project

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I'm well on my way into my MR2 project. Purchased it last year with the stock ECU doing some funky things which made for a good project. I'm doing it in two parts. Part 1 is to remove all the stock engine management and anything that no longer needs to be in the engine bay along with any simple mods I can do to the stock engine, Replace it with a standalone and make tune it. Part 2 which I'm doing concurrently is building a more serious replacement engine in my garden shed which I can eventually swap into it.

Part 1: Have used a diy megasquirt ms3x. It has a pretty awesome feature set but you have to build the board and harness yourself. However the online instructions and support are excellent. I'm using LS coils instead of the dizzy because I had them from another project but I had to mount them in the boot. Sensors are stock toyota except for GM air temp. My wiring is a bit of a mess for now as I want to finalise it before I tidy it all up.

I tried to use the toyota dizzy with its 24 tooth wheel to give a tach signal but found the VR sensor struggled to get a good signal at cranking rpm despite making some adjustments to the trim pots on the board. However I was able to cut the dizzy body away so it was just the 24 tooth wheel on the shaft. Then ground 1 tooth off to make a 24-1 wheel and mounted a hall sensor. This worked much better and gets a good signal from zero RPM.

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Stock injectors are the rather hard to replace side feed variety and there are a few manufacturers selling top feed kits for these engines. But you don't need to buy a kit. The 3sge (non turbo mr2 engine) has a top feed fuel rail with the correct spacing. Get some top feed injectors and it fits right into place. However the mounting tabs are on the wrong angle. But you can cut them off and then bolt a piece of angle aluminium to the fuel rail (theres plenty of extra material to drill and tap into). As for the injectors - I've used stock red rx8 260cc injectors with the tips cut off. This allows them to flow 590cc/min. These red rx8 injectors go for peanuts because everyone wants the 440cc yellow ones. I tested them with tips cut off and flow is not quite as consistent as stock - however I brought 10 of them and matched the best 4 which were within 2%.

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As for the spray pattern on the modified injectors. It has become a smaller cone but still atomises well. Has not stopped me from getting a smooth idle. Video attached shows modified and unmodified injectors spraying side by side.

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Water/methanol system is a mix of devils own and aquamist parts. I have 5L tank in the boot and a 320cc/min jet post intercooler with a 110cc/min jet pre turbo. I will upgrade that to port injection setup later to ensure all cylinders get the same amount. It is controlled by FAV valve which behaves like an injector. I am running it from the staged injection settings on the ECU as if it were a secondary injector. Obviously I had to lie about the injector size in settings because it thinks its running 1 secondary per cylinder and also because of the water meth/mixture having very different stoich value to petrol/gasoline. I put a brake line pressure switch in the meth line and that triggers the ECU to switch boost map as a simple failsafe. Basically the closed loop boost settings won't come on until the meth line is pressurised. If the water/meth pump fails the turbo will only make wastegate pressure. MS3x ECU is mounted in the boot along with relevant relays etc. Fitted a bigger ebay sidemount intercooler with a fan that runs all the time off the fuel pump relay. Made my intercooler pipework in an attempt to keep runs of silicone hose to a minimum. It also demonstrates my incredibly inconsistent welding skills (I'll do a lovely weld one day and just melt big holes in my work the next). Engine internals and turbo are stock. Stock turbo is an incredibly weird combination of big compressor and small turbine. It makes No power til 3k rpm. Then 270bhp by 4k rpm. By then the turbine side is choking the exhaust and it starts loosing power all the way to redline. Still not a bad amount for now. Mapping the MS3x was pretty straightforward. The menus are logical and I had done a bit before on MS2. Had it on old bosch inertia dyno with someone who really knows megasquirt inside out so he was able to pass a lot of good info on. It's a nice, fun reasonably quick, easy to drive car for now and will be a whole lot more fun when I've finished building another engine for it.

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Part 2 - the engine build:

So at the same time as doing the other work on the car I've been building an engine for it in my garden shed. In keeping with the rest of the build I'm trying to creatively reuse OEM bits.

The block is 3sge non turbo block. It is basically identical to the turbo one and I got it for free. One main difference is that it doesn't have piston oil squirters. I'm taking a calculated risk here but should be ok without them (I hope!). Bored out to 0.5mm to 86.5mm and a skim over the top. Crank is also stock with ACL bearings. Manly rods and Wiseco pistons. The rods came with weights specified on the box however when I actually weighed them they were up to 2.5g wrong at the big ends. Fortunately due to Andre's awesome videos I was able to remedy this. Pistons despite being dished turbo pistons want to increase the compression ratio from the factory 8.5:1 up to 9:1. Cleaned up the casting marks in the ports on the head. The ports are enormous from the factory so nothing to enlarge there. Cleaned up all the sharp edges in the combustion chamber and removed a little material to drop the compression ratio. Realised you have to remove quite a lot of material to make a difference so I stopped there and just got them all to the same volume. Final compression ratio is 8.7:1.

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For the top end I've used a 3sgte turbo head, original valves cleaned up and lapped and Engle valve springs. I've replaced the shim on bucket lifters which the 3sgte uses with later Toyota 31mm shimless buckets which are a straight swap. Obviously you need to work out what sizes you need and them buy them individually to size. I also discovered that you need to turn the cams a few times to make them settle before you measure the clearances...as I've had to buy a few more buckets now. Exhaust cam is stock but intake cam is from a mk6 celica which uses a more modern 3sge engine. It has a longer duration and and extra mm of lift. I did have to dremel the head slightly to clear the cam lobe. Cam gears are ebay specials. Quality on them looks good but the advance and retard markings are in the wrong direction! Worth paying attention to. I was surprised when I did the piston to valve clearance check that despite putting quite a bit of plastercene on the piston crown the valve didn't even contact it. These engines have a huge piston to valve clearance of about 4mm which means you can fiddle with your cam timing quite some distance without a worry. In fact I think with a thick head gasket it might even be a non interference engine. I'd rather not put that to the test!

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For the turbo I've chosen a Kinugawa GTX 3067 ball bearing turbo. It imitates the Garrett turbo of the same name. How well does it imitate - well I'll have to find out for myself. As a road car my goal is for it to spool up really quickly and pull all the way to redline. Ultimate power is not my goal although I hope I can see around 400bhp. I brought a set of turbo adapters from ATS in the states. I could have probably made them but sometimes it's just nice to be able to bolt something on. They are intended for Garrett T28 turbo and almost fit perfectly. The Kinugawa wastegate arm contacts the exhaust adaptor but I've milled it to get a bit more clearance and hopefully the wastegate will open far enough. We shall see! I've removed the TVIS throttle valves from the inlet and used the plate they come on to place the jets for port injected water/meth.

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I found instructions on youtube to make a raspberry pi dash from the pi3 with touchscreen and bluetooth keyboard. If you look up ducksport on youtube you can find the tutorial. It fully connects with tunerstudio and the MS3x ecu so as well as being a dash you can make any changes to the ECU that you would on your laptop (albiet a bit of a fiddly job with a little mini bluetooth keyboard but useful). It does take 80 seconds to start up which is annoying but no big deal since your engine will be cold anyway and you won't be pushing it. Cost less than £100 to put together. I also have the ECU controlling the electro hydraulic power steering so you can set how much assistance you get at with speed (none in my case but with full assistance below 5mph when you actually want it).

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curious about your dizzy set up, what are you using for the home signal?

any photos?

2nd photo on the first page Josh. Basicially the stock dizzy with the vr sensors and the 24 tooth wheel removed (it all presses together and its not super tight). Then hacksawed the body off it and bolted a 90 degree bracket to it to take a hall sensor. Ground one tooth off the 24 tooth wheel and pressed it back on the shaft.

this is some awesome stuff. I've always been into the mr2's and this makes me want to buy one a lot more now. Although everyone here in the US is swapping out the engines for a K20/K24 swap (which ill probably do if I got one) but still good to see some people still using the good ol Toyota power to make these babies move! good work bud.