Megasquirt choice

If you want the cheapest possible the MS1 on the version 2.2 board will do the job. You'll need EDIS for the ignition but that's not a great problem on a 4 pot.

If you want the least possible messing with electronics then Microsquirt is probably the one.

For anything else, MS2 on version 3.0 hardware has most of the bells and whistles (and what it doesn't have can be added). You can use EDIS for the ignition or add another ignition driver (easy) to fire a wasted spark coil pack directly.

Nick

There's 3 main revisions of Megasquirt; 1,2 and 3. But each main option, by it's very open source nature, has numerous firmware options which give different features. On top of this the amount of assembly and soldering required ranges from a bag of components and bare circuit board to a complete plug&play ecu. To add insult to injury some suppliers use their own naming conventions that won't match the manuals…. I'm about to build my 4th Megasquirt (the 7th vehicle I'll have been involved with using squirt!) and I use www.diyautotune.com religiously. They are american based but really really helpful guys and the parts arrived really well packed and lab led making life easy, all for a good price with the exchange rate too.

So really I'd say get on www.megamanual.com, www.msextra.com and www.msefi.com and get reading! From personal experience of doing it the hard way, if you follow someones guide letter for letter and just kinda 'paint by numbers' to end up with a working car it's all well and good but if it hoe's wrong or you want to modify anything you run into trouble. It's harder work but working your way through the hardware and software manuals on msextra.com really means you have an understand of why you need to make 'this' modification and why you pick 'that' build option.

That said…for pretty much any retro car I'd be looking at using the Megasquirt 2 hardware with the MS2extra firmware. MS3 has got some nice features but a lot of the real gains are for very high performance cars and modern cars (can bus etc) and it just adds unneeded complications for a first time user IMO.

EDIT: That ECU in the eBay link is a Megasquirt 1 ECU on the V3 board (cost about £180 new if unassembled), which will happily run your engine but won't have some of the useful options that ms2 has. MS2 runs at higher resolution, has better input signal filtering/smoothing options, has better acceleration enrichment options and better options for starting and warm up running. The circuit board on that ECU will have been modified specifically to work with the 1.8t engine sensors, so you'd either need to find a way to use the VW crank angle sensor and stuff, or get in there and change some components on the board to match your micros set-up anyway. Again if it were me I'd say build it from scratch, you get the ECU just right for your car with no compromises and have a better understanding of whats going on along the way.

wouldn't advise buying a used megasquirt [especially when the price is more than a new DIY assembly kit or microsquirt!]

Check out ExtraEfi.co.uk and diyoutotune.com, and triggerwheels.com for loom components, EDIS & coilpacks (& microsquirt)

Brilliant, thanks

What sensors would I need to go with it?

for MS1 with EDIS ignition - 36-1 trigger wheel & sensor on the crank.
For MS2 with twin coil-drivers fitted (or microsquirt) you can use any known trigger wheel pattern & sensor.
You can use pretty much any inlet air temperature (IAT) and coolant temperature sensors(CLT) from an Efi-era car & if you can't find their resistance tables on the web, you can do your own tables by testing the resistance at various temperatures.
MAP sensor (manifold absolute pressure) reads the inlet pressure and calculates air flow - suggest 3 Bar GM type (will read up to 29.4psi, if you want to boost over that you'll need a 4 bar MAP)
Throttle position sensor (TPS) again from any Efi era car and probably free on the side of whatever throttle body you use, megasguirt software (megatune) can calibrate any TPS automatically. Most of those could be robbed from the Micra K11 Efi

I would (and did) go with www.diyautotune.com as GoldNRust suggests. They were great with my kit, as he says, cheap, well packaged and helpful. Other than the price being too much to bother with in my opinion, the 1.8t set-up could work, management wise they're fairly straightforward once converted to a single coilpack (72 tooth trigger wheel iirc, and common Bosch sensors) the only unusual thing's the stepper motor throttle body used to control idle, but that could easily be retrofitted to your engine, and is quite a neat solution to idle control. Personally I'd build a new one up though. As has been said, it'll mean you know and understand the system, which is a hugely useful position to be in if you want to play with your engine.

I was about to post the same thread - looking at doing this on a 3 cylinder carbed engine. Only really want to use a GM SPi throttle body and a throttle position sensor and a crank sensor. Would Megasquirt V2 do this OK?

www.ebay.co.uk/itm/megasquirt-/131104300464?pt=UK_CarsParts_Vehicles_CarParts_SM&hash=item1e866cddb0

I have been thinking of doing something similar as well. I've got a 1.1 106 and it has SPI. I was thinking that if I could get it to run using all the original sensors and adding a MAP sensor I could just make an adaptor lead to go from the OE plug. This way when I mess up adjustiong it I can just plug the old ecu back in.
It's really just a project to learn how to do it but it will hopefully make it go a bit better and do away with the nasty immobiliser thats just waiting to play up.

Good idea with the Old ECU. Might as well make the old one into a nice sealed enclosure for the connector plus it looks standard. If I do actually get round to doing it I will probably have more questions, thanks.