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Home > Beginners Tech > Megasquirt on an MPi engine

Cooper1999

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Evening all,

I've built a modified MPi engine and the MEMS can't cope. I had thought about the Specialist Components MPi system as the easiest (but more expensive) option (I should say I'm an electronic biff and while willing to learn, know nothing about programmable ecu's).
But it has been suggested that (with help) Megasquirt might be a cost effective option.

A few questions I have if anyone can help me:
- Can the megasquirt work with the standard MPi set up? Is anyone doing this and if so, what problems have you encountered?
- Does a trigger wheel need to be added to the MPi engine to use Megasquirt? How easy is this?
- Are the MPi injectors high impedance? Does anyone has a spec sheet or information on the standard injectors?
- Is the standard MPi coil pack up to the job?
- Perhaps most importantly (for me), is the programmable element easy to navigate?

I've spent the last hour or two using the search function, but haven't found a thread on using Megasquirt on a standard (components) MPi set up.

Thanks in advance.


Andy500

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Hi I’m not sure how it’s costs in comparison to the other options but I would also consider an Emerald ECU, pretty straightforward to use and extremely well supported by emerald👍


shane

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I’ll second Emerald, it’s a superb system with great aftermarket support.

Shane

Edited by shane on 31st Oct, 2020.


Cooper1999

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Andy, Shane - do you have any experience of the Emerald ecu? Do you know if it uses the original MPi sensors or does it need additional items (uprated fuel regulator, trigger wheel etc)?
I'm going to have to learn this stuff but need it to be as (relatively) simple as possible - I really am starting from the electronic standing start!
Thanks,


Rod S

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On 31st Oct, 2020 Cooper1999 said:

A few questions I have if anyone can help me:

Before the questions, bear in mind the MPI is a very different beast to the SPI. The SPI is a simple batch injection wet manifold setup that ignores the charge robbing issues that the "A" (and "B") series engines exhibit. To meet the emissions regulations of the last couple of years of production Rover had to come up with something that overcame charge robbing. To do so, they opted for port injection as close as possible to the valves they could and then they took a 4 channel MEMS, programmed its four outputs to match the 4 inlet vale opening timings - taking into account transit times, wall wetting and much more - the paralleled up pairs of outputs to feed the two single injectors. The inlet valve timings (open to close) are not symmetrical because of the inlet vale opening overlap so to make sure the fuel goes to the correct cylinder the injectors are very large compared to what you'd expect on a 1275 engine because they only get to inject when the inlet vales are open so need to run a very low duty cycle compared to an eight port engine. To try and keep them as small as possible what they then did with MEMS was programmed it so that at a certain RPM/load point, instead of four individual pulses corresponding to the inlet valve timings, they switched to a single "long" pulse that covered the combined openings of the inner and outer cylinder valves. Again, this has to be timed precisely to get the correct amounts of to offset the differing mass of air from charge robbing.
If you ignore Rover's second tweak, then any programmable ECU that allows different injection timing tables for individual cylinders and allows four outputs to be paired as twos would achieve the same - so long as you have separate widebands on the inners and outers to be be able to tune the timings.
An alternative is to ignore the fundamental single timed pulse per cylinder method and use the "long pulse" method. Again, any ECU where you can set the timing of two channels to specific values (which can be varied with RPM and load) would achieve the same.

I must stress, the only reason I say all this is because the MPI setup is port injection.

The majority of people take the much simpler approach of throttle body (sometimes called wet manifold or electronic carb) which is why the Specialist Components throttle body setup is so popular. I wasn't aware they now have something specific for the MPI port injection setup but if it mimics the specially programmed MEMS then I'm sure it can be made to work.

But with any port injection, you will need two widebands or run the serious risk of all the fuel going into the inner cylinders.

But, back to the questions

On 31st Oct, 2020 Cooper1999 said:
Can the megasquirt work with the standard MPi set up?

Yes, the MS2 can replicate all the features of the MEMS, the MS3 can use the timed long pulse method.

On 31st Oct, 2020 Cooper1999 said:
Is anyone doing this and if so, what problems have you encountered?

There are several of us doing port injection on the "A" series, so pretty similar to a standard MPI, but I don't know of anyone who's done it to a "standard" MPI. Graham T uses a lot of MPI parts but he's modified his MPI inlet manifold for additional (staged) injectors for higer power.

On 31st Oct, 2020 Cooper1999 said:
- Does a trigger wheel need to be added to the MPi engine to use Megasquirt? How easy is this?

If your chosen ECU recognises the totally weird tooth pattern of the reluctor ring on the back of the MPI flyheel, then no. Some aftermarket ones do because Lotus used the same pattern on their flywheels but it is most definately not commong (Megasquirt does although I'm not 100% sure anyone has used that bit of the code). Other wise just put a 36:1 trigger wheel on the crank pully like all the megajolt users do.
Also note, any timed sequential injection ECU needs a cam trigger. The MPI does have one but it's a VR sensor (in the old fuel pump hole) and only works with an MPI specific cam (or a cam modified to match the MPI pickup).

On 31st Oct, 2020 Cooper1999 said:
Are the MPi injectors high impedance? Does anyone has a spec sheet or information on the standard injectors?
Yes, high impedance and Paul or Graham may have their datasheet, I don't, I use low-z injectors.

On 31st Oct, 2020 Cooper1999 said:
Is the standard MPi coil pack up to the job?

Not one I'm familiar with but I don't see why not (although there will be much better newer stuff available)

On 31st Oct, 2020 Cooper1999 said:
Perhaps most importantly (for me), is the programmable element easy to navigate?

With Megasquirt, I find the interface (TunerStudio) very easy to use.
However, knowing what to adjust, when and why, is a completely different matter.
You have to have two widebands to se what is going on with the inner and outer cylinders and you have to understand the effects changes will have and why.
So, the overall answer is No....
But I like a challenge.

On 31st Oct, 2020 Cooper1999 said:
I've spent the last hour or two using the search function, but haven't found a thread on using Megasquirt on a standard (components) MPi set up.

If it's "standard" then why is MEMS not performing ? It should work fine with any MPI setup so long as the power hasn't been increased by much (I think it has a 10% margin). But beyond small increases it's just not programmable (in the normal sense) so little use on tuned engines.

FINALLY, I must stress - because some will say I have over-complicated the issues - everything I have said is about port injection.

If you want a simple life, go throttle body (wet manifold/electronic carb with batch injection four squirts per cycle) and it gets so much easier - hence the popularity of Specialist Components throttle body setup.

Schrödinger's cat - so which one am I ???


Cooper1999

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Just had a look at the Emerald website.
I see this is a system developed/sold by Dave Walker. I've enjoyed reading articles written by Dave Walker for many years, first coming across him in Cars & Car Conversions.

One of the articles on his website refers to fitting FI to a midget A-Series car:
http://www.emeraldm3d.com/articles/cat/pro...midget_Project/

Reading this he comes to the same conclusion I think as SC, in so much as it isn't really possible to efficiently port inject the A-Series because of the siamese ports, better to run an 'electronic carb' wet manifold solution as efficiently as possible.

Now I've read the threads on here for many years regarding the difficulties in injecting the A-Series because of the Siamese ports. I suspect a couple of things:
- It may be possible to run MS on the standard MPi set up to allow better control of the fuelling/ignition etc. but with limitations.
- an electronic carb set up (as described by Emerald and sold by SC) might be a compromise, but have 'higher' limitations.

Anyone got any thoughts on this?


Rod S

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On 1st Nov, 2020 Cooper1999 said:

Reading this he comes to the same conclusion I think as SC, in so much as it isn't really possible to efficiently port inject the A-Series because of the siamese ports, better to run an 'electronic carb' wet manifold solution as efficiently as possible.

The only thing I would disagree with is the "it isn't really possible to efficiently port inject the A-Series because of the siamese ports"
Even the article you linked states that Rover achieved it.
Rover did it to meet the then required emissions requirements, I guess that's my best definition of "efficiently".....
SC haven't been able to match the MEMS of its time (over twenty years later) hence why they push their throttle body solution.

No, it's not easy to do port injection but perfectly possible as Rover showed (and a few of us on this forum)...

But it's not for the faint hearted....

But if yours's is a genuine MPI of the age range it should be, how you intend passing a current MOT with the emissions you will get from a batch/wet manifold/electronic carb setup (ie, an SPI which would fail emissions on the age range of an MPI ?)

Why not just sort out your MEMS which will pass the emissions standards ?

Schrödinger's cat - so which one am I ???


shane

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Yes I do, I run one on my K build.
I use no MPI sensors, I used those that emerald sell which are off the shelf available items.

Shane

On 1st Nov, 2020 Cooper1999 said:
Andy, Shane - do you have any experience of the Emerald ecu? Do you know if it uses the original MPi sensors or does it need additional items (uprated fuel regulator, trigger wheel etc)?
I'm going to have to learn this stuff but need it to be as (relatively) simple as possible - I really am starting from the electronic standing start!
Thanks,


Cooper1999

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Rod - some great info in your reply - Thank you.

Yes it's my lack of knowledge which has led me to use the phrasing I have regarding being able to port inject the A-Series. Perhaps I should've said 'easily' rather than 'efficiently'.

I've rebuilt my MPi engine as 1342cc, SW5i cam, 1.5 roller rockers etc. and it seems the MEMS cannot cope with these mods which is leading to emissions problems. It's this that I'm trying to address. I need to meet the emissions for an 96-00 MPi car as I've built the engine to go into a Mini Marcos and it needs to go through IVA testing - the emissions relating to the age of the donor engine.

I suppose I'm thinking of taking the easy way out thinking of going the electronic carb route - I've been building the car for 10 years and really just want to get the thing on the road now to enjoy it! But which ever way I went (Megasquirt with MPi set-up (if possible) or Emerald/SC), it'll still be a significant investment which I'd want to get right and hopefully learn something on the way.

Thanks again all - this is new territory for me.

Edited by Cooper1999 on 1st Nov, 2020.


Rod S

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On 1st Nov, 2020 shane said:

Yes I do, I run one on my K build.
I use no MPI sensors, I used those that emerald sell which are off the shelf available items.

Shane


To be fair Shane, a K build can use any ECU you choose, pretty much. Even a Speeduino (about as cheap as you can get and, yes, I've built one just for fun and it works).

Because what you get from a K build is a standard 8 port engine.

The question was about a 5 port MPI using the basic MPI port injection system and mostly standard MPI parts and trying to replicate what the MEMS (programmed for the MPI) does.

I'm sure Emerald is fine on any 8 port engine but I'd like to hear how it can deal with a five port siamese with only two direct siamesed port injectors.

Note, again, I said port injection , not throttle body, which any ECU can deal with.

Schrödinger's cat - so which one am I ???


Paul S

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I have the Mpi manifold and sensors running on an MS3. As Rod says the MS can handle the flywheel and Cam sensor from the Mpi. You should be able to run the Mpi coil in wasted spark mode off the Ms.
http://www.turbominis.co.uk/forums/index.php?p=settings

Saul Bellow - "A great deal of intelligence can be invested in ignorance when the need for illusion is deep."
Stephen Hawking - "The greatest enemy of knowledge is not ignorance, it is the illusion of knowledge."


Paul S

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I have the Mpi manifold and sensors running on an MS3. As Rod says the MS can handle the flywheel and Cam sensor from the Mpi. You should be able to run the Mpi coil in wasted spark mode off the Ms.
http://www.turbominis.co.uk/forums/index.php?p=settings

Saul Bellow - "A great deal of intelligence can be invested in ignorance when the need for illusion is deep."
Stephen Hawking - "The greatest enemy of knowledge is not ignorance, it is the illusion of knowledge."


Paul S

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Some useful info:

http://jbperf.com/sequential/Fuel_Injectin...e_A_Series.html

Saul Bellow - "A great deal of intelligence can be invested in ignorance when the need for illusion is deep."
Stephen Hawking - "The greatest enemy of knowledge is not ignorance, it is the illusion of knowledge."


jbelanger

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To use port injection on a 5-port engine (MPi or otherwise), you need to be willing to learn and understand why injection timing is essential and how it works.

On a 'normal' engine (non-siamese), you adjust fueling by changing the injection pulsewidth and injection timing is just icing on the cake. On a 5-port engine, you still need to adjust the pulsewidth but injection timing is not the icing, it's the cake.

Check the link Paul posted and search the forum for more on tuning and using AFR from 2 wideband O2 sensors to get the right timing. The 2 sensors are essential as Rod mentioned above.

http://www.jbperf.com/


shane

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Rod,

That is totally fair comment (and if anyone wants me I shall be in the corner with my dunce cap on), but my original comments re Emerald where seconding Andy's acknowledgement for Emerald and the support received by those at Emerald.

I'll happily and openly hold my hands up and express my knowledge and understanding of the siamese code is limited and wether the Emerald system could be used to run the MPI engine I cannot say.

"I'm sure Emerald is fine on any 8 port engine but I'd like to hear how it can deal with a five port siamese with only two direct siamesed port injectors." I'm more than happy to say that you would know more than I on this subject.

Shane


On 1st Nov, 2020 Rod S said:
On 1st Nov, 2020 shane said:

Yes I do, I run one on my K build.
I use no MPI sensors, I used those that emerald sell which are off the shelf available items.

Shane


To be fair Shane, a K build can use any ECU you choose, pretty much. Even a Speeduino (about as cheap as you can get and, yes, I've built one just for fun and it works).

Because what you get from a K build is a standard 8 port engine.

The question was about a 5 port MPI using the basic MPI port injection system and mostly standard MPI parts and trying to replicate what the MEMS (programmed for the MPI) does.

I'm sure Emerald is fine on any 8 port engine but I'd like to hear how it can deal with a five port siamese with only two direct siamesed port injectors.

Note, again, I said port injection , not throttle body, which any ECU can deal with.


Rod S

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No offence intended Shane, I just wanted to ensure anyone who might read this in the future (from searching the subject) that the MPI injection (or any other port injection) on an "A" series is quite different to port (or throttle body) injection on 8 port engines.

Rod.

Schrödinger's cat - so which one am I ???


shane

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Rod,

Absolutely none taken, I should of been clearer.

Shane

On 2nd Nov, 2020 Rod S said:
No offence intended Shane, I just wanted to ensure anyone who might read this in the future (from searching the subject) that the MPI injection (or any other port injection) on an "A" series is quite different to port (or throttle body) injection on 8 port engines.

Rod.


Andy500

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Hi Guys,
Great thread and I’ve certainly learnt more, what I can say is that I know the emerald supports at least some of the MPI sensors. I used one on a supercharged 5 port that ran two standard Mpi injectors but the charger ran wet so fuelling was only controlled by adjusting the pulse width. It no longer used the Cam sensor but all other sensors including the flywheel trigger sensor and the coil pack were standard mPi items.

Admittedly it was a bugger come MOT time but it could be done with a second map.

Edited by Andy500 on 4th Nov, 2020.


Rod S

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I've got to love this bit

On 3rd Nov, 2020 Andy500 said:

Admittedly it was a bugger come MOT time but it could be done with a second map.

I did get dragged into one of Anna's (wifey's) friends Lotus with an early Emerald setup about 15 years ago (so, before I learnt Megasquirt/TunerStudio) and his comment was that the MOT map was fine but slow and the performance map was crap and an MOT fail.

It was just the "MOT map" phrase that was just so... well you know what I mean.

I found his problem was a bad joint on the exhaust downpipe - his custom manifold just had an open sliding joint rather than a sealed bellows so was leaking in masses of air before the wideband sensor.

I'd just never heard the "MOT map" phrase before....

But the Emerald software interface was fine to me at the time and I'm sure it's probably a lot better now.

I just don't think it would cope with a five port, but those of you on eight ports it's probably one of the best "off the shelf" solutions if you don't want too much DIY.

Schrödinger's cat - so which one am I ???


Cooper1999

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Okay - so I'm talking to someone who can build up the Megasquirt for me (one of my worries) and a new engine loom, who advises possibly using a VW coil pack (they have they're own 'drivers', and are relatively cheap and easily available I'm told), a wideband sensor and a 36-1 trigger wheel if possible (I read the comment in an earlier reply that the MS2 can utilise the standard items).

But my question is - can a trigger wheel be fitted with the engine in situ? There's not a lot of space in the MM to begin with and I can't easily take the engine out these days (needs to come out with the subframe from below) so if I were to retro fit a trigger wheel would hope it's 'bolt on'.

Trigger-wheels.com show these (three) items as being required: https://trigger-wheels.com/store/contents/en-uk/d30.html
Anyone used these? Any reason these wouldn't work on an MPi block?

Once again - thanks for answering what I'm sure are 'billy-basic' questions.
*smiley*


Rod S

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First, let me say again, if you are going to do any form of port injection, MPI based or otherwise, you need TWO widebands, one for the inner cylinders and one for the outer.

If you do not understand the reasons why then just do a TBI/wet manifold/electronic carb setup.

Do not try any form of MPI type port injection without two widebands. The only alternative is to stick with MEMS where it has already been pre-programmed to deal with the siamese charge robbing issues so you know the AFRs are balanced - Rover spent a lot of time, money, research to perfect it. To use any aftermarket ECU on a port injection siamese engine you absolutely have to be able to see the AFR variation, understand why they are different, and tune the settings accordingly.

As already stated, an MS2 or MS3 will read the weird Rover (also some Lotus) flywheel pattern, there is no need for a 36:1 wheel but if you prefer to go down that route, it depends on how easy it is in your engine bay to get the crank belt pully off as that's where a 36:1 wheel would normally go.

To run port injection (MPI or similar) you need a cam signal for phasing. The MPI has one but it's VR rather then the normal Hall.

A standard MS2 or MS3 (an MS3 without an MS3-X) needs an additional circuit for a cam VR sensor.

Whowever is building this should know that.

Likewise, the VW coilpack which uses logic level drivers inbuilt is a very good - and more modern than Ford wasted spark coilpacks - but it does need someone who knows how to install the TC4427 driver chips to make it work.

EDIT - 3rd para re-worded to make it more clear (I hope...)

Edited by Rod S on 10th Nov, 2020.

Schrödinger's cat - so which one am I ???


Steve220

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Not sure why you're so hell bent to use the MPI manifold when you're going to struggle unless you have taken heed of what Rod has written. I ditched it and went SC wet TB and getting good results on an MPi engine with a turbo 👍🏽


Rod S

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As Steve says, unless you fully understand (or want to learn) the complexities of port injection just use a well proven TB/wet manifold/electronic carb setup and set it as lean as can get away with to pass the emissions test on your IVA (or find a way of avoiding the IVA...).

Schrödinger's cat - so which one am I ???


Steve220

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Mine passes the MOT emissions for a 2000 plate car perfectly each year *smiley*


Cooper1999

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Some great info in the link. I've much to learn I think.
Definitely easier to go wet manifold but let's do some homework and see which way I want to jump.

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