RobT Posted September 3, 2018 Share Posted September 3, 2018 I need to change my clutch fairly soon which will mean pulling out the mk2.5 1.6 engine. I've had a cunning thought to drop a mk2.5 1.8 in its place as ill get an extra 35 bhp for a few quid. Do any of the sdv experts know if the engine is any taller or if the wiring and ecu are the same? I don't want to start messing with the loom too much as it's a bit beyond me but would like a bit more oomph. Maybe best to trade up to one already fitted Your thoughts will be much appreciated Quote Link to comment Share on other sites More sharing options...
darve Posted September 3, 2018 Share Posted September 3, 2018 Vvt doesn't fit under the bonnet Think your wiring will need a bit of adapting. What's your plan for ecu? Quote Link to comment Share on other sites More sharing options...
Mark (smokey mow) Posted September 3, 2018 Share Posted September 3, 2018 Yes the 1.8 is roughly 3/4" longer and a similar amount taller than the 1.6. Quote Link to comment Share on other sites More sharing options...
darve Posted September 3, 2018 Share Posted September 3, 2018 http://ox.mx5oc.co.uk/guide_technical.html Quote Link to comment Share on other sites More sharing options...
darve Posted September 3, 2018 Share Posted September 3, 2018 How about a high compression mk1 1.8 - 160bhp. I need to rebuild the bottom end though Quote Link to comment Share on other sites More sharing options...
Dommo Posted September 3, 2018 Share Posted September 3, 2018 The 1.6 uses smaller clutch, flywheel so saves weight outside the engine itself. I'd stick with it unless you want many powers. Quote Link to comment Share on other sites More sharing options...
RobT Posted September 4, 2018 Author Share Posted September 4, 2018 23 hours ago, darve said: Vvt doesn't fit under the bonnet Think your wiring will need a bit of adapting. What's your plan for ecu? Wanted to stick with the original. Perhaps that's not possible. Quote Link to comment Share on other sites More sharing options...
Gary Taylor Posted September 4, 2018 Share Posted September 4, 2018 The mk2.5 1.8 vvt uses a totally different Ecu from previous versions in that it is “adaptive “ so as to control the vvt aspect and includes extra sensors as well it also has to run through the immobiliser and instrument binnacle circuit boards from the mk2.5 i spent a long long time trying to avoid this to no avail on my s/c conversion in the end I used it as is sorry for the bad news and as above the vvt actuated is on top of the engine making it significantly taller Quote Link to comment Share on other sites More sharing options...
darve Posted September 4, 2018 Share Posted September 4, 2018 The map would be wrong. Doubt MAF would compensate enough. Ecu connectors probably different so doubt could swap ecu due to wiring differences You'll be able to see here: http://neomiata.com/garage/index.php?path=Wiring+Diagrams%2FWiring+Diagrams+1997-2000/ Quote Link to comment Share on other sites More sharing options...
RobT Posted September 5, 2018 Author Share Posted September 5, 2018 Thanks for all the comments guys. Since going through these I've found that I've made a slight boob in that I reckon my car is mk2 and not mk2.5 as its a T reg which is 1999. I'm sure it doesn't have an immobiliser but as has already shown in this thread - what do I know?? Does this news mean that a mk2 1.8 is a much better option now? I realise that my exhaust will need modifying but will this run on a 1.6 ecu? I think the throttle body, coils and a couple of sensors need fiddling but could this be back on? Also has anyone tried to lighten a standard flywheel? I wany to use a standard clutch but am considering adding some holes for extra reviness. I think I can get an aftermarket one for about £300 but may be able to mod one for next to nothing so its an attractive mod. Quote Link to comment Share on other sites More sharing options...
darve Posted September 5, 2018 Share Posted September 5, 2018 your 1.6 ecu won't run a 1.8. the map will be all wrong please don't drill holes in your flywheel these need to be well balanced. I had mine very carefully lightened and balanced by a machine shop @Mark (smokey mow) can you remember what it's called think I have a stock 1.8 flywheel kicking around (unless I took it to the tip after dropping it on my wheel arch.....) you're welcome to have. you could use the 1.6 flywheel and clutch with a 1.8 if not running lots of power you really need to think about going aftermarket ecu if you're going to complete engine upgrades / swap. you could of course install a wiring loom and ECU from a mk2 1.8 Quote Link to comment Share on other sites More sharing options...
Geezergs Posted September 5, 2018 Share Posted September 5, 2018 Rob if you get a MK1 1.8 it will fit, you will better fitting a ME221 ECU, I have a manifold and down pipe you can have also a very lightly used clutch and flywheel, I think you will do better dumping the MAF and using inlet air temp sender (BMW) and vacuum pipe back to the ecu.If you get Dave's Blink head the package should see about 160bhp ish can't remember if you need bigger injectors , look on the MX5 forums it's a very popular swap or contact Motorsport Electronics for advice ECU wise.. That will be a big increase for a nominal outlay I'm sure we will all give you a hand Quote Link to comment Share on other sites More sharing options...
Mark (smokey mow) Posted September 5, 2018 Share Posted September 5, 2018 38 minutes ago, darve said: your 1.6 ecu won't run a 1.8. the map will be all wrong please don't drill holes in your flywheel these need to be well balanced. I had mine very carefully lightened and balanced by a machine shop @Mark (smokey mow) can you remember what it's called think I have a stock 1.8 flywheel kicking around (unless I took it to the tip after dropping it on my wheel arch.....) you're welcome to have. you could use the 1.6 flywheel and clutch with a 1.8 if not running lots of power you really need to think about going aftermarket ecu if you're going to complete engine upgrades / swap. you could of course install a wiring loom and ECU from a mk2 1.8 It was CTM performance in Dagenham Quote Link to comment Share on other sites More sharing options...
Geezergs Posted September 5, 2018 Share Posted September 5, 2018 Rob regardless of what engine you go for you will need to change the ECU if you want to up the performance as the standard ECU can't be tuned it's fixed.. Quote Link to comment Share on other sites More sharing options...
Dommo Posted September 5, 2018 Share Posted September 5, 2018 When at similar stages of tune (standard, induction kit, 4-1 manifold), @Mooch's 1.6 was mostly just a quick on track as my 1.8. The power deficit being offset by the lighter weight. Stick with the 1.6, it's a good little engine Quote Link to comment Share on other sites More sharing options...
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