Ignition mapping, getting the basics.
Turbo Mini Forums

Hi,

my engine is slowly comming together in the garage and the EFI is working on a test stand. Fuel programming I have some calculation sheets for to get me going, but how about ignition timing? I think I will copy a standard 1275 mechanical advance curve and vacuum curve to the computer, but how about boost sensitivety, when vacuum becomes pressure? I don't mean to program perfectly in one go, but I'm looking for a good starting point. The enige is a 1293, 8:1 CR, mildly flowed head and SW5 cam. All suggestions / educated guesses etc. are welcom, too.
Thanks,
Hugo

Hugo

*** 1989 Jet Black body stripped for resto ***
*** 1988 Metro engine undergoing turbo conversion ***
*** 1989 BMW 318iS as daily run-a-wreck ***

are you running a wet manifold? I would be interested to hear more about your EFI, what ecu are you using and how many injectors are you running?

Team Racing

start with a std dizzy and work from there!

EFi is going to be interesting!

alex

AlexF

y the guy who did my megasquirt does jenvey EFI throttle bodies, think he emailed jenvey to see if there was one that would bolt straight onto the manifold, or could make an adaptor plate i suppose. Would be interesting to know the implications/effects on putting EFI on a turbo. I'm tempted as the the 42mm body is only about ?120. I know theres more besides the body but is it worth looking into?

yes the jenvey body will bolt on but the pcd is smaller so with minispeed conversion they use overlapping washers , ignition avance will bearound 30 degrees at idle, cruising off boost up to 45 - if you have lower compression than the std engine it will require more advance - basic load settings 15 @2000 ,20@2500 ,24@ 3500, 26@5000,28@7000,are you using a map sensor ?

jenvie make an SU adaptor for there single throttle body

so appart from being 100% ignition and fuel mappable, whats the real benefits of going full EFI?

if done correctly, spot on fueling 100% of the time, better drivabilty, better fuel eco ect. But I don't know how todo it, so I'm still using an SU

Team Racing

hm, i'm REALLY tempted. I have the ECU so i'm half way there, so do i go EFI or stay SU, decisions decisions. Theres also the added expense of having to have a plenum made up too... hmm, i'm torn. I'm at that point right now where i could choose to go either way, AAARGH what to do!

Edited by Mike on 11th Apr, 2005.

if your not sure of the benefits then you really need to read up on the whole "5 port injection" malarky. It certainly doesnt sound easy at all.

Id say double your build cost (including RR time/delvelopment stuff) compared to that when using an SU.

hm, I slept on it last night - i'll go with SU for now but defo gonna look closer into it.

Theres quite a good site here http://www.hotbricks.org.au/articles/guide_efi.html titled "A Basic Guide to Electronic Fuel Injection
for Minis"

Good choice, defo an idea to keep "in the bank" so to speak though

Theres quite a good site here http://www.hotbricks.org.au/articles/guide_efi.html titled "A Basic Guide to Electronic Fuel injection for Minis"

Yep, the references to overcoming the charge stealing issue were very useful for anyone wanting to know what REAL problems they're going to face.

might be a silly question, but how so the SPI and MPI's get around the problem? I have no experience of these two so i might be missing something here!

Spi is like a SU carb... one big injector above the throttle butterfly (plate).

MPi is two injecdtors that uses clever software to stage the injection event. It works... but only to a certian power output, after that you run out of time to get enought petrol in and 2 cylinders run lean enought to misfire!!

Alex

AlexF

they dont use su's on f1 engines ,
i'm on the third brand of fuel injection , seen the benfits -idle control-traction control-air temp corrections - unbelievable drivabillity/fuel enconomy/power/low emissions-, not going back to carbs !
downsides money and time because not much developement has been done yet , but i'm on it

Edited by stuart gurr - vmaxscart on 12th Apr, 2005.

Can of worms time! LOL!

Tom, thanks for the kind words, but my choice of the SU is because there is, according to the distributors of a number of ECU's, nothing out there that will properly fuel inject an A-series satisfactorilly.

I'd love to be on injetion, and hopefully it'll feature on my mini again this year. But i'm not simply going to 'inject and hope'. I'll be running another ECU to replicate and move the injection event such that charge stealling doesn't occur at any RPM or loadsite - basically as MEMS MPi does.

I just can't see any real advantage in going efi if it isn't going to be 100%. You can have that for free with an SU if you spend long enough working it.
All you're gaining is the ability to get rid of a significant restriction in the form of the plenum restrictor, and to control fuelling by a laptop rather than filing a needle.

Jimster sent me an article recently of another turbocharged A-series being tuned on Dave Walkers rolling road. His approach now is to go for a wet manifold.
Once again - why bother ditching an SU for a system that still has a wet manifold?


Mapped ignition, now there IS something that transforms the drivability, torque, throttle response and economy of any engine comared to a dizzy. Only as good as the guy working it though.

I'm just not convinced you'll see enough of a power/drivability difference between a "perfectly set-up 3D dizzyless ignition and a perfectly set-up SU", compared to a "perfectly set-up 3D dizzyless ignition and a claimed well set-up injection system" that warrants the extra money. The ignition is where the big gains are...

Edited by turbodave16v on 12th Apr, 2005.

great thread. my ECU guy has a megasquirt and a jenvey on his girlfriends mini, i'll get him to register and post his findings and thoughts.

Cool, that'd be good.

just thinking... wouldnt 2 bodies help overcome the charge stealing to a point? What with cam overlap etc tho i suppose u still got the possability of neighboring cylinders stealing too? Looks like an arden 8 head will be the way fwd lol.

Mike - basically to get round the charge stealling 100%, you have to make sure the fuel that has just left the injector doesn't make it to the 'beak' between the ports until the 'inner' valve has just closed (eg - 40 degrees ATDC for the outer cylinder).

Now, This means you need a pretty large injector to get all the fuel into the outside cylinder for the 180 degrees the outer valve is now open for (assuming that this valve closes at what is now 40degrees ATDC. This is further complicated by the fact that you should probably want to stop injecting the fuel at around 40 degrees before the valve closes as the gas velocity (which carries the fuel) is really dropping off at this point...
So that's 140 crank degrees to get all the fuel in.

Now it gets even more complicated because the air velocity (which carries the fuel) changes WRT RPM - hence, at high RPM, you need to inject the fuel later than at low rpm otherwise the first few drops 'could' end up going through the inside valve just before it closes...
One way round this is just to inject at (for example) 60degrees ATDC mind...

Another problem - injectors take time to operate - but modern high impedance ones should reduce this down to a minimum - even so, this could lose you valuble crank degrees-worth of injection event - potentially crucial at high rpm.

Twin injectors per inlet tract is definately the way to go - especially for a force induction engine (100% more fuel / 1 bar of boost than a nat-asp engine) that spins at high rpm.

Lots of ways round it - but making electronics do what you want is the hard bit! I'm sure the boffins on the MS forums should have a programme written by now!

I'm pretty sure that a set of decent modern, hi-flow injectors, and a sufficiently late-enough opening on the injectors (relative to TDC and injector position) will get enough fuel in there quite happily for a mild 1275 without dynamically shifting the injection event - so, I must correct what i said earlier. I've just always got my 'turbo' thinking hat on unfortunately!

Problem we're always going to have is getting enough fuel in there at 7000rpm and 1.5 bar of boost! LOL!
But if an SU can do it...



Sorry for the edits guys - a few incorrect words and spelling!

Edited by turbodave16v on 12th Apr, 2005.

Dave, you said

"I'm just not convinced you'll see enough of a power/drivability difference between a "perfectly set-up 3D dizzyless ignition and a perfectly set-up SU", compared to a "perfectly set-up 3D dizzyless ignition and a claimed well set-up injection system" that warrants the extra money."

But you're still going to fit an injection system on a 5-port head?

Or are you getting some extra ports?

Wil

Fastest 998 mini in the world? 13.05 1/4 mile 106mph

There is a Mpi turbo in Norway, but I do not know ANYTHING about it or how it drives..... I should really find this out..

Well Wil,

I've already got an ECU that is EFI ready, All the wiring is in, I've got an EFI fuel pump, EFI regulator, and now I've got an ECU nearing completion that will put the injection event where it wants to be. All of which I paid for a long time ago.
If I didn't have all of that already fitted, it is not very likely I'd be paying - at a guess - something in the region of £600+ to gain a little bit more power (in the region of single figures going off what peeps normally achieve).

"that warrants the extra money."
and
"claimed well set-up injection"
are the key-phrases in that paragraph however.


You are of course correct however, I was definatelly incorrect in generalising that statement. I guess what would have been more correct would be to say something like:
"I'm just not convinced you'll see enough of a power/drivability difference between a "perfectly set-up 3D dizzyless ignition and a perfectly set-up SU", compared to a "perfectly set-up 3D dizzyless ignition and a claimed well set-up injection system" that warrants the extra money until all other power/performance increasing avenues have been investigated"

I'm starting my manifold very shortly, so we'll be able to have a back-to-back test at some point.

Edited by turbodave16v on 13th Apr, 2005.