23 replies to this topic

[Lt-SilverDragon]

Does anyone have any experience with the amethyst mappable ignition system or does anyone have any maps for a lightly tuned 1275? I'm just running the basic map the now (the one that comes with the unit) and my mini is running fine with it but there isn't much top end so I'd like to try and adjust the timing to see if I can get any improvements out of it. I'm in the southwest of Scotland so I don't know of any rolling roads near to me and I've not got lots of spare money the now anyway so can't really get it on a rolling road but I'd like to try doing some adjustments to it.

 

Mini is running bigger then standard head, 1.5 rockers, hif44, 1.75 exhaust and I've got a air/fuel gauge and it sits just slightly rich at about 13:1.

 

Also the one thing I'm not sure about is do I set the dizzy like a normal dizzy with strobe light or do I set it at TDC and let the unit control everything as I've just followed the instructions by putting cylinder 1 to TDC and turned the dizzy until the red light shows on the control unit to start the mini and pretty much left it at that.

[carbon]

Just to check, have you locked out the mechanical advance in the distributor?

Edited by carbon, 30 September 2017 - 04:50 PM.

[Lt-SilverDragon]

Yep, well I just bought the dizzy off aldon because I didn't want to mess around with original dizzy. At the minute, the mini is running just like it was with the original dizzy and low down grunt is actually not too bad.

[NZMini1275]

Can't remember what the base map looked like but from memory it was a safe one to run any engine so won't be giving what the engine wants
I currently have mine set up to mimic Aldon yellow settings
Set at 10 degrees btdc at 1000rpm with the vacuum to the amethyst plugged
Just waiting on dyno session to adjust to optimum

[NZMini1275]

Also a good source for curves is the 123 dizzy site as it has all the maps they use
http://www.tdcperfor...uning_guide.htm

There figures are based on dizzy being set at tdc like yours

Edited by NZMini1275, 30 September 2017 - 07:12 PM.

[Lt-SilverDragon]

That's grand mate, I think I'm getting an idea of what to do with it. I'll need to find the cable that fits into the amethyst and have a play, think I'll try one of the curves from the 123 site.

[Spider]

Given the slight modifications to the engine, I'd suggest starting from a stock 1275 Curve and go from there.

 

Respectfully, I've found that while the idea of the 123 is great, the curves don't suit any A Series Engine too well.

[Lt-SilverDragon]

I adjusted it slightly from the standard curve that was already programmed into the unit, will give it a test run tomorrow and see how it feels. I think it's got a standard cam in it so that will probably be holding it back in the higher rev range.

[carbon]

What compression ratio do you have, and what octane fuel do you use?

 

Both make a significant difference to the advance curve.

[Lt-SilverDragon]

Have no clue on compression ratio, I'll need to figure that out next time I take the head off. Didn't build the engine so not sure on specs.

Use tesco momentum fuel and when I've got it an lead additive with octane boost.

[carbon]

You should be able to get a rough idea of CR from doing a compression test. But really need the battery and starter motor to also be in good condition, otherwise the numbers can be misleading.

 

On a 1275 with fairly tame cam if you get 200psi that's likely to be about 10:1 compression ratio.

 

Does it start pinking if you use Tesco 99-octane without the octane booster?

[Spider]

 

On a 1275 with fairly tame cam if you get 200psi that's likely to be about 10:1 compression ratio.

 

You're scaring me now !

[carbon]

Here's an even scarier test...

 

When I ran a compression test on a fast road 1330 using 21253 pistons, 7 thou deck clearance, MD266, and very lightly skimmed 940 head this test gave about 225psi on all 4 cylinders with cold engine.

 

With hot engine it runs up to about 200 (2 or 3 turns) and then you get big kick-back. This is with throttle wide open but the SU piston not held open.

 

I suspect it's dieselling. So right on the margin for compression ratio, and this was with 99 octane fuel.

[Lt-SilverDragon]

I've been meaning to buy a compression tester but I'm not sure if a cheap one off amazon will suffice or if I should spend a little more on a better quality one?

Batt and starter are both new so should be fine with getting a reading so will get a tester and see what it shows.

Nope it doesn't pink, not even with the morrys bog standard unleaded as I've filled it up with that before.

[Lt-SilverDragon]

Ok got a compression tester coming today hopefully, also took the car for a run and it feels slightly better but I didn't do anything radical to the map. It's got loads of torque, can drive around at 30mph in 4th all day long and I think it accelerates quite well from 30 to 50 in 4th, starts to lose steam about 50 upto 60 tho. Seems like the gearing isn't ideal, could do with long gears.