15 replies to this topic

[oliver122]

Hi Guys ,

 

Its been a while since ive posted on here and its been even longer since my mini has been on the road.

 

ive finally got it up and running and ready for an mot after a rebuild that's taken longer than I expected but that a different story . Now I have drove it down a "private" road to check everything is ok and noticed that during gear changes its hesitant until it gets back up the revs and picks its feet up again . During the rebuild i have upgraded the fuel system ( injection tank and turbo fuel pressure regulator set at 3.5/4psi ) and have had the trigger wheel pully off as well ( I have since pinned this to the crank pully ) as well as fitting a lightened flywheel . I am leaning down the side of it being an ignition issue as I don't believe that the trigger wheel is not in the exact same position as it was originally. I was thinking of getting it rolling roaded again after its MOT but thought if i could sort it before it would be a bonus .

 

I did wonder if it was possible to alter the table to suit the new trigger position and if so what would be the best way about it . I have the software on my laptop and can borrow a timing gun .

 

Any advice would be appreciated.

 

Thanks,

Oliver 

 

 mini igntiton.jpg   43.15K   2 downloads

[PoolGuy]

I've no experience of Megajolt, but in the Polestar software you can adjust the trigger point, maybe MJ is the same, it'll avoid having to change the map?

 

Interesting map.

[Ethel]

You can do the same with mj, just moves the whole map relative to the crank position sensor.

 

Could it be a bit of lag with the MAP sensor (guessing it's on MAP as it's a turbo)? 

 

Plugging it in to your laptop should allow you to figure both out in real time. It can't be far off if it's running.

[Icey]

In the 'Global Controller Options' you can set the trigger offset but I'd just sort out the sensor location if you've moved the missing tooth relative to TDC.

You can always use datalogging to see what's going on, I'd expect the hesitation to show on the load line.

This is the map I've used on our 1275 for a couple of years now without an issue:
 

Edited by Icey, 23 March 2022 - 03:50 PM.

[mini13]

I would say that its idling in the 1000 rpm.60 kpa box ( or close to so is seeing 13 dgrees, and as soon as you crack the throttle the vac dissapears pulling it into the 70/80/90 boxes causing it to retard and bog, I would bump the timing up in those boxes so they are similar to the ones around them.

 

FYI although the dizzy  timing figure is 8 degrees, thats with the vac disconnectoed, usually with the vac attached you'll see closer to 15 deg at idle ( depending on the carb)  my turbo motor used to run about 18 deg at idle.

[sonscar]

Firstly before bodging anything YOU MUST.. verify the actual timing vs the commanded timing using a TDC mark and a strobe and adjust the trigger angle to correct this.This is a fundamental with mapped ignition and MUST always be done.
Once this is verified then think about changing values.Steve..

[mini13]

^^^ this is a good point. Defo check that if you haven't

[oliver122]

Thanks for the replies guys I will take a look , its currently n/a but wanted to plumb it ready for a turbo engine

For info:
1275
276kent cam
Ported polished big valve head
Lightend flywheel and turbo clutch
4 pin diff

I don't think its to far out, as I lined it up to where it should be but it might of been out before when I had it rr'd

[mini13]

the timing on these systems will interpolate between boxes, so in your instance, if your idling at 100rpm and the vacum is 65kpa you'll be seeing approx 10.5 degrees, but with any change in kpa the timing will change quite a bit as the values in the 60 and 70kpa boxes are quite different....  So when you checking your timing you would be best to temporarily set the boxes in the idle area to all the same value so stabilize the reading ( unless of course theres a disable the timing table in one of the menu's for this purpose, its been a while since i dabbled with this system as  I run megasquirt)

 

 

Another tip, check the timing marks are accurate. I use the dead stop method with an old plug with the ceramic knocked out, and a bolt put through it. essentially it stops the piston just before TDC, so you turn one the motor one way til it stops make a mark, the turn the other way and make a mark, then your TDC mark shoul be half way between those two marks, the closer to TDC you can get the dead top to stop the easier this will be.

on my motor Ive made a hole in the transfer case so I can see the ring gear, Ive got one tooth of the ring gear painted white and a TDC mark next to the hole, much easier to get to, and easier to get an accurate reading due to the larger diameter.

[oliver122]

the timing on these systems will interpolate between boxes, so in your instance, if your idling at 100rpm and the vacum is 65kpa you'll be seeing approx 10.5 degrees, but with any change in kpa the timing will change quite a bit as the values in the 60 and 70kpa boxes are quite different....  So when you checking your timing you would be best to temporarily set the boxes in the idle area to all the same value so stabilize the reading ( unless of course theres a disable the timing table in one of the menu's for this purpose, its been a while since i dabbled with this system as  I run megasquirt)

 

 

 

so if for setting up i changed all the values at 1000rpm to say 8 then checked with the timing light that it was reading 8 degrees on the timing case and crank pulley that should give me what i need then i can just put the existing values back in ? im pretty sure on my tdc mark as i marked it all up when i checked my cam timing 

 

i'll fire my laptop up tonight and look , its booked in for its mot on Saturday so want try get it right before then  

[mini13]

Yep, thats it

 

chances are its fine, but worth checking

[Icey]

If you've got your wiring in a module form, you can just unplug the MJ from the EDIS unit and it'll default to the base advance 10°

 

[oliver122]

Yep, thats it

 

chances are its fine, but worth checking

 

4 degrees out it turned out to be which is what the global offset was on , knocked that back to 0 and its running sweet now ! 

 

If you've got your wiring in a module form, you can just unplug the MJ from the EDIS unit and it'll default to the base advance 10°

 

I could remember that i had it running on the edis alone at one point but that was about 8 years ago now so I wasn't 100% sure , also ive got it mounted all behind my dash so its abit of a pain get to !

 

Thankyou all that's helped , its picks up now without hesitate under load 

 

 

just out of curiosity as ive never really looked into it before when looking at my map and Icey's map  , when the load is 40 and transition through 1500-2500rpm i noticed that it is set 22 27 26   should that 27 be more like 24 to be smoother as icey's map looks more in numerical order if that makes sense  (i did wonder if it has something to do with the cam kent 276)  

[mini13]

the odd degree in that 40kpa load site is probably not going to make any difference, you might find the engine never actually runs in some of those load sites except on over run.

If it does then typically it is a fairly lean low throttle situuation where the burn rate will be slow so the engine will probably want a fair amount of advance, I would have no qualms about putting a few more degrees in that area to see how it runs, its the 80-100kpa area's you really need to be careful with as thats where you can get detonation that may damage stuff.
 

[Ethel]

So it was mechanically 4 degrees out with 4 degrees offset in the software? Does that mean you've bolted it back together better than it was before 

 

 

Could you have flipped the trigger wheel over???  4 degs of mech retard with 4 degs of software advance would put you at tdc, but 4 adv + 4 adv would have you 8 degrees out.

 

It really doesn't matter if you're working from the actual tdc, it's just a datum, but it's handy if you can refind it easily - as Mini 13 explains. Also helps for comparing notes & pinching other people's ignition maps.

 

 

As far as timing bins & interpolation: Yes, you'd expect a smooth progression, but the beauty of being able to program each bin independently is  not having to - say you found a particular point where it pinked, you could retard the timing just there to take it away from detonation. Some bins will be used more than others, say it's a road car that you want economic cruising out of at 55mph.