Jump to content
The mkiv Supra Owners Club

Swapping j-spec engine for a UK engine


Simon

Recommended Posts

Nothing in search so I guess no one has done this yet but I'll ask anyway.

 

2 prime questions.

 

Apart from the physical engine and turbos,

 

1. would the wiring and piping be the same?

2. is the UK ecu a straight swap for the j-spec?

 

Secondary question

Has anyone investigated doing this yet?

Link to comment
Share on other sites

Perhaps the J-spec engine has gone the way of the dodo, and the replacement is UK spec?

 

Simon, let us know the story behind this madcap plan of yours :)

 

Things that immediately spring to mind are:

The turbo downpipe may not fit to the exhaust

The fuel injectors will need a resistor pack wiring into the j-spec loom as they are low impedance

The j-spec ECU may be different for emissions control stuff that is on the UK specs, including the second CAT

The j-spec ECU will have a fuel map for smaller injectors and the different turbos may be a factor as well -> this is a biggie, and says to me you need a UK spec ECU

The j-spec fuel pump may not be up to the job with the UK spec engine-side fuel system

 

There is a good chance the ECU will be a straight swap, as I have used a UK/US spec ecu wiring diagram and pinouts map for all my electronics tinkering and fixing and have had no discrepancies so far, apart from some pins not doing anything because I don't have the stuff they control.

 

Are there seperate ECUs for auto and manual models? Might be worth checking.

 

-Ian

Link to comment
Share on other sites

Guest Martin F
Originally posted by Ian C

Are there seperate ECUs for auto and manual models? Might be worth checking.

 

-Ian

 

Yes there is, it's stamped on the ECU sticker.

Link to comment
Share on other sites

Martin, to answer why, because it could be relatively cheap if there was one in a breakers. But mainly it was an enquiry as to whether anyone had played about with the idea and had a better feel for what it would entail.

 

Ian C - Thanks very much for your input, I had thought about the other stuff (autobox etc after posting) but it was late so I didn't add anymore.

Link to comment
Share on other sites

If someone went this route then you might as well replace the ecu with aem or something similar at the same time.

 

I just thought it may be an option that could be cheaper (if sourced from a breaker) than making all the changes to a j-spec regards injectors etc.

 

Downpipes/exhaust is something that most people replace anyway so cost wise it can be ignored.

Link to comment
Share on other sites

Guest Martin F

I think i'm correct in thinking that your reasons for doing this are because you want the additional performance from a UK spec engine.

 

IMO this is not the best or cheapest way to go about it. An engine from a scrappies is most likely going to be somewhere between £1000 and £1500 unless you find a scrappie who really does not know the value of the car\engine. Then there is the work (if you do it yourself) or labour costs on top.

 

All for the sake of gaining what ? A few more HP, a little more headroom on the injectors and perhaps a bigger wastegate if you brought the turbos with you.

 

I'm not trying to put a dampner on things, but it seems like a lot of work (and money) for not much gain in my opinion. Better off doing the injector\resistor upgrade and changing the cams.

 

But at the end of the day it's up to you.

Link to comment
Share on other sites

I just thought I would say while we are on the subject of UK spec engines that hopefully a friend of mine has sourced a fairly low mileage UK spec engine which I am going to dismantle and re-build.

 

I think its going 6to take a while but I thought about changing all the internals for uprated parts (low friction small skirt racing pistons, balances 1 piece conrods etc) will have to be one part a month until i have done it, but I managed to squeeze 160 bhp out of an old crossflow once so im sure i can make this one fly.

 

Anybody got any useful stockists for racing parts?

 

Is this going to be hideously expensive?:flame Dev

Link to comment
Share on other sites

Engine swap - there are far better things you can do with £1500 (or even £1k) than swap in a UK engine. Pretty pointless IMHO.

 

Rebuild: Budget on £1k for pistons and about the same for rods. If you want an uprated crank you probably want a JUN kit which is about . . . £:eek: or thereabouts. How much power do you want? Stick with the stock internals until you get over 500bhp I reckon.

Link to comment
Share on other sites

Guest Martin F
Originally posted by 400BHP

but I managed to squeeze 160 bhp out of an old crossflow once so im sure i can make this one fly.

 

 

You can't really compare what you managed to achieve with a 60's technology engine with a late 80's engine. Especially when you begin to look at the engineering standards on a Toyota compared to a Ford.

Link to comment
Share on other sites

Yes the power outputs of a 60's engine may not be relevant but engine building practices are the same on any reciprocating internal combustion engine, and the fundamentals are what you NEED to know in order to correctly build an engine.

 

Head flowing, vacuum testing, port polishing, engine balancing etc are all still the same principles no matter who the engine is made by!

Link to comment
Share on other sites

Originally posted by 400BHP

Yes the power outputs of a 60's engine may not be relevant but engine building practices are the same on any reciprocating internal combustion engine, and the fundamentals are what you NEED to know in order to correctly build an engine.

 

Head flowing, vacuum testing, port polishing, engine balancing etc are all still the same principles no matter who the engine is made by!

 

The general consenus from what I have read is the the Supra engine is very well designed and built in the first place. Gains from porting and polishing only come into play when very high BHP's come into play. Uprated internals are usually reserved for high boost pressures with medium to large turbo's although opinion appears divided on the matter in the US. Cams only come to play with larger turbos.

 

I'm no expert but I would have to question if, other than better engine pick up from lightened internals, you could improve the standard engine output dramatically.

 

When you consider even the basic cost of the parts it's much easier to turn up the boost or have a bigger turbo installed.

Link to comment
Share on other sites

Guest Martin F
Originally posted by 400BHP

Head flowing, vacuum testing, port polishing, engine balancing etc are all still the same principles no matter who the engine is made by!

 

But as Gavin states the yields from doing that depend on how well the engine has been designed and built in the first place.

Link to comment
Share on other sites

  • 1 month later...

Ive got the same initial question as the title of this thread. But the thing is, i need an engine. Mine is a J spec at the mo, but the engine is knackered. Broken piston rings, blown turbo's and a scored bore. rather than payin a forture to repare, ive been lookin at replacement engines. Ive been offered a 49000 mile Uk spec engine complete with turbo's. Was just wondering if i need to change the ecu too. Also the one they have offered me is from a Uk 6 speed. Will it fit ok to an auto?? Will i have to change anythin else or will it be best to just get another J spec engine???

Link to comment
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.
Note: Your post will require moderator approval before it will be visible.

Guest
Reply to this topic...

×   Pasted as rich text.   Restore formatting

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

×
×
  • Create New...

Important Information

We have placed cookies on your device to help make this website better. You can adjust your cookie settings, otherwise we'll assume you're okay to continue. You might also be interested in our Guidelines, Privacy Policy and Terms of Use.