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EJ20H Single Turbo Conversion... Info please!


Guitar_Guy
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Hi guys, so I'm slowly gathering bits (thanks Clint) for a single turbo conversion in my BG5.

I've done a bit of research and the conversion itself isn't super difficult but I'm struggling a bit

with engine specs and what limitations I might have with the EJ20H.

I gather the heads don't flow as well, the cams aren't as good as the EJ20R and the compression is higher meaning a v3/4 STi ECU might wet itself.

A few key questions below...

a) Looking to see if anyone here has successfully done this to an EJ20H?

b) Can I solve the compression issue with thicker headgaskets?

c) Do I just run the TT into the ground as is and drop in an EJ207 sometime in the future?

Thanks!

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Koom's post from the above link:

 Koom said:
Thats one of the harder ECU conversions and I don't believe that a straight swap is worth it i.e. using equivalent WRX 4-plug ECU and keeping the grey injectors.

You need to swap about 80% of the pins on the ECU and change a couple of wires around under the bonnet.

The old pinout list for this conversion is this one;

ECUPinoutsBC5BG5aWRX4plug-1.jpg

But I also have a colour coded one here which has a few more instructions on it: https://www.dropbox.com/s/fo77a7bk8l51eg2/ECU%20Pinouts%20BC5%20BG5a%20WRX%20%284%20plug%29%20-%20Single%20Swap.pdf

But if I was to ever approach this conversion again myself, the only way that I would ever consider bothering with the work would be to use a 3-plug STI ECU and convert to V3/4 STI single turbo. So would also require yellow injectors, correct AFM etc.

Takes more work and parts to achieve the conversion but gives a much better result.

The electrical side isn't much different to swapping in a 4-plug WRX ECU (Tip: 3 of the 4 plugs on the 4-plug ECU's can be used for a 3-plug conversion as they're the same plugs. You just leave out the 12pin plug).

In this case you'll need to use a V3/4 ECU pinout list to compare and swap around the relevant pins. Some sensors may also need to be changed but if you buy a complete manifold then most of that issue should be solved.

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No worries man, but yeah looks like a headache for minimal gains. Be better to change to a complete EJ20K V3/4 STI engine/ECU and re-pin or re-loom for probably less effort, better gains and a matching CR.

Or like you say hold off and go the whole hog, V7 STI engine/ECU/loom/cluster. It's just jumping in at the deep end if you haven't done much engine/ECU wiring. Then there's the cost on top.

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 Rosssub said:
No worries man, but yeah looks like a headache for minimal gains. Be better to change to a complete EJ20K V3/4 STI engine/ECU and re-pin or re-loom for probably less effort, better gains and a matching CR.

Or like you say hold off and go the whole hog, V7 STI engine/ECU/loom/cluster. It's just jumping in at the deep end if you haven't done much engine/ECU wiring. Then there's the cost on top.

Yeah it's all pretty new as far as actually doing the work is concerned. A v7 STi complete swap would probably be more achievable in some areas and give me the reliability I want as well.

Just a $$ thing but would rather do it all right the first time and the TT is keeping me relatively happy for now. Finally got the shell I want so just a matter of filling it with the right goodies.

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  • 2 weeks later...

I didn't see mention here what EJ20H was in use. Is it a BG5A HLA (ribbed rocker covers) 20H, or a facelift auto solid lifter (smooth rocker cover) 20H?

I'm going to assume it's the former hydraulic type. I've come to love these engines over the years, I used to hate the hydraulic engines, but I see their charm these days. Good old school blocks that make an awesome noise, and can still be made to make a bit of power. If it's a good block, don't feel obliged to pull it out and put something wanky and modern in it when you don't have to.

Just use a WRX ecu for the conversion, or better yet, a link if budget allows (even an old possum link can be had for about $200 these days). If it's a 4-plug loom, it will not be pleasant you re-pin, but you can choose to go to either a 3-plug or a 4-plug. Going to a 4-plug is probably the harder choice, as you'll have to revert to older sensors (though will let you run V2 WRX ECU's which are perfect for that block/combustion chamber/head flow etc), going to a 3-plug would be fine. in which case, a V3/4 WRX Auto/wagon ECU will be the go, and should make the same power as the factory BG5A ECU.

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  • 2 months later...

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