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mS3 1500 Herald


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I have fitted a MS3 system to my 1500 herald. After a bit of a fight I got the ignition working very well.

I have now moved on  to the fuel injection and finally got it started last weekend. Its runs, but is very very rich.

For the VE map I used the wizard to generate one (which does not look very different from what other people have used on 1500 Spitfires). But it runs far too rich. So I have gone into the table and multiplied all the cell by 0.5 and now its running at about 13.5 AFR.
What I don't understand is why my VE table is so different from others? I feel I must have got some other setting wrong but cant see what it is!

BTW the AFR values in the tuning software agree with the AFR gauge and you can smell and see when it runs very rich


Below is the VE table and the engine settings.
The car has Jenvey Throttle bodies (probably a bit big for the engine), Bosch 747  injectors (200cc/min at 3Bar, again maybe a bit big for this engine), wasted spark ignition.
I have tried both MAP and ITB control but don't yet see much difference so am using ITB control. The engine is a standard spitfire 1500 block with standard cam but with a gas flowed stage 2 head (whatever that means!).

At the moment I haven't driven the car but am testing it in the garage, with the exhaust vented out of the garage. It starts, runs thru the WUE and then settles down to a nice tickover. It seems to rev ok and really needs to be road tested now.
I have disconnected my idle valve for the moment as it had some air leaks and so blocked the pipes.

This has been a steep learning curve, but very interesting, but would really like to understand why my VE table is different from others before going on.
Any suggestion very welcome!

cheers

mike

ve table 30 jan.jpg

injector setting 30 jan.JPG

ve table 30 jan.jpg

injector setting 30 jan.JPG

injector 30 jan.JPG

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Not sure about MS3 but MS1 and 2 have a basic setup parameter call "required fuel" where you enter the injector flow rate, engine displacement, number or cylinders and injection strategy (batch/sequential, no of squirts per cycle etc).  The resultant "required fuel" number factors the whole VE table (like winding the jet up and down on an SU) and if this number is well out you get strange numbers in the VE table.  Having said all that I've spotted your screenshot and all looks quite sane......

Nick

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Thanks Nick

I think the problem is that the injector I have used has too big a flow rate so is very sensitive to pulse width. 

I had set the dwell time to the default of 0.9mS, as I understand it this is added to the calculated pulse width from the fuel equation. As the injector is too large for the power of the 1500
engine any small change in pulse width has a significant change in fuel going to the engine. When I reduced the dwell time and went back to the calculated VE map I started to get a
a good AFR.
So I think I understand what's going on. Ideally I should reduce the size of the injector but the one I have used is a short body one, the usual Rover ones that  others have used will be a bit long and interfere with my airbox (yep design fault..)....

So still learning!
Hope to take it for a drive out of the garage tomorrow!

Mike

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Reducing the fuel pressure reduces the injector flow proportionately.  So your 200cc/min injectors become 167 cc/min at 2.5 Bar.  IIRC the injectors used on the Vitesse are nominally 214 cc/min at 3 bar but I run a 2.5 Bar regulator so get 178cc/min.  May be worth trying a lower pressure regulator?  Maybe some slight reduction in atomisation efficiency.

The dwell time can be worth fiddling with (there used to be a methodology for working out the actual dwell time of your injectors on the MS website) but mostly affects idle and light cruise where pulse widths are short.  Not convinced it's you biggest issue.

Good luck with your drive!

Nick

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  • 2 months later...

Thought I should update this.

Just done a 1600 mile trip from Cambridge to northern Scotland in my 1500 Herald to do the North Coast 500 route with some friends .
The car was wonderful, much quicker and nicer to drive than I ever managed with SU carbs. It did a good job of keeping up with some MX5's and a Tr5 around the single track roads of the highlands, plenty of torque and revs. And even though it was thrashed around it still managed over 36 MPG (useful as there are not many petrol stations up there).

I think there is till room for improvement with the maps (it hasn't been on a rolling road yet as I think of it as work in progress), but it has certainly been worth all the effort to get it working. The whole EFI system just worked, had no problems with it at all.

The speedo broke, the horn has packed up, the drivers mirror fell off and the sync on second has had it. Oh and the engine is burning rather a lot of oil....
Apart from that had a great time, but do have a list of jobs for the future (rebuilt engine, refurbish gearbox etc).
I had fitted Uniroyal Rainmaster tyres on it and Mintex front pads, both worth the money all helped to make the car more enjoyable, it would go round corners and stop!

One strange think that did happen was that it did not like going over the mountains even though they were only 2000 feet or so. It felt like  a TR6, very rich and misfiring. I have added a extra pressure sensor to compensate for altitude but had not enabled it yet and really did not want to change it while the rest of the time it was fine.
I also think the AFR sensor was effected by the oil, I had it setup to correct the VE table for AFR readings and this did some strange things at times. Something else to add to the list of jobs.

BTW The NC 500 route is really excellent, and its good to do it this time of the year as there are not to many camper vans or supercars and the midges haven't woken up yet.

cheers

Mike

 

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Thanks for the update Mike.  Glad it's working for you. :biggrin:

Without barometric correction you will seen some richening as you go up, but I would not have expected significant, even noticeable effects at under 2000 feet - unless it was on the rich side already.  In those situations, if you stop, switch off and restart you will zero the calibration, which should cure the problem - until you go up further or go back down - at which point it will go lean.  Barometric correction is better and seems to work well.  The Vitesse has done many passes over 2000 metres with no problems (the economy suffers due to the uphill thrashings it gets, not from running rich!), although it won't idle at altitude unless I manually turn the idle up as it doesn't yet have active idle control.

The Bosch wideband sensor I'm using (with Innovate LC-1 controller) survived several tens of thousands of miles breathing the gack from my old engine (about 500 miles/litre without Wynns, though mostly I ran it with Wynns for obvious reasons) without apparent harm.  Maybe I was was lucky......

Carry on the good work and keep us posted

Nick

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