Megajolt - now what? Where next?
David Jenkins - 14/1/07 at 11:07 AM
OK - I now have a working megajolt with a basic 2D map. The car is running very smoothly and accelerates well, but I suspect that it would benefit
from a 3D map as it now hesitates very slightly when I floor the pedal after pottering along on mid-revs (this didn't happen with the old dizzy,
but that had vac advance).
The problem is that I know three-fifths of very little about ignition tuning - I need some clues about how to develop the map. I could go to a
rolling road, but:
1. How many RR operators would know how to test and set up MJ using my PC?
2. I don't really have the spare cash to pay for an hour or two's worth of RR time.
So, all in all, a bit of guidance would be appreciated!
BTW: I'm using a MAP sensor connected to the vac advance outlet on a Weber down-draft carb. This gives me near-atmospheric pressure (~100KPa) at
tickover and low pressure (~20KPa) when revved up and under load. I think I've got that the right way round! 
My current map is
HERE
All help appreciated!
David
graememk - 14/1/07 at 11:33 AM
TURBO next
MkIndy7 - 14/1/07 at 11:57 AM
Firstly close up the Vacume figures so the table only displays what figures your engine achieves.
If its 20kpa on full load and 80kpa on idle then any values on your table outside of this are a waste, and space them evenly across this range.
Where there is little Vaccume (load) i.e 80kpa) you can advance the timing, and where there's alot of vaccume it may need retarding.
A figure like setting off or flooring it might be say 2000rpm with 30kpa vaccume.. this would probably need retarding to get it to pull well without
hesitating or pinking.
A figure of 2500rpm with 60kpa vaccume would be a cruising speed or over run so it can be advanced.
Bugger can't find my maps on this computer.. .the Vaccume figures could be the wrong way round it takes some figuring out!.
Its best to try and tune it with 2 in the car.. the passenger just watches the run time display for where it pinks and then retards it in that area of
the grid the cursor is on when it pinks. Some sample maps of the net might be useful as a guide to compare yours with.
David Jenkins - 14/1/07 at 02:32 PM
quote:
Originally posted by MkIndy7
Its best to try and tune it with 2 in the car.. the passenger just watches the run time display for where it pinks and then retards it in that area of
the grid the cursor is on when it pinks.
Could be tricky - my old laptop has a knackered battery (I only ever use it with mains connected). 
Need a new battery, or a car 12v power supply.
David
TangoMan - 14/1/07 at 02:32 PM
quote:
Originally posted by David Jenkins
This gives me near-atmospheric pressure (~100KPa) at tickover and low pressure (~20KPa) when revved up and under load. I think I've got that
the right way round!
David
Yup. Wrong way around. Atmospheric will be at Wot and there should be substantial vacuum at tickover.
You total advance looks about right. I think I used to run my crossflows at about 38 max.
You should also be able to advance the low to mid range a bit on low throttle openings as this will help pickup and economy.
As I guide, under load you are most likeley to get pinking so at WOT you need to be careful how fast the advance comes in. Under light load and high
vacuum conditions the mixture burns slower and needs more advance. How much is really trial and error. I would suggest moving in small steps adn
progressive work through your map over the course of a few weeks.
I would start by bringing the advance on 3 degrees earlier at 30 or 40 MAP all the way through to max revs. Max advance here is not really relevant as
you are unlikely to see max revs on low throttle except overrun. Lots of advance is then useful to control popping through the exhaust.
Drive with this and see how it feels/sounds then move up one MAP range and start again.
I found logged my rpm and throttle settings at cruising speeds and them tuned that area first. After tuning, once the settings seemed good I would
find a hill and abuse the engine with lots of load to ensure no pinking.
Have fun but do it progressively. Don't rush it as you will likely jump in too large increments and will miss the sweet spot.
MkIndy7 - 14/1/07 at 02:45 PM
quote:
Originally posted by David Jenkins
Could be tricky - my old laptop has a knackered battery (I only ever use it with mains connected).
Need a new battery, or a car 12v power supply.
David
Ours was the same, we used a 300W inverter we had to power the mains charger.. maybe a worth wile investment was only about £30.
Or of you've already got a 12v laptop transformer, we got a 12V lighter socket from Maplins thats ment for mounting on a cable.. and then 2
crocodile clips onto the battery brought wither through the bulkhead or from under the bonnet and over the scuttle.
Thats if its not worth installing a lighter socket in the car or inside the glove box.
David Jenkins - 14/1/07 at 03:01 PM
I have the lighter socket - I use it as a power outlet, and to connect the trickle charger.
Unfortunately, my laptop needs 15v so I'll have to find a suitable power supply (I suspect that Maplin has one, but their prices are high!). As
you suggest, I could go for an inverter to get 240v, which is another option.
cheers,
David
MkIndy7 - 14/1/07 at 03:08 PM
If you have a suitable plug end lieing around the cars 12V+ with the engine runnin might just be close enough to the 15v required to run, Might be
worth a try.
The inverters can come in handy... Mobile fone etc charging if you have't got a car charger.. Mains Solidering Iron, Small Dremell etc
martyn_16v - 14/1/07 at 06:22 PM
I've used this method to generate a table as a starting point for a couple of engines,
they've turned out to be pretty close to bang on so far. There' also some info about working things out on the
MS2 instructions that may be of use 
paulf - 14/1/07 at 06:53 PM
I had a working map for a crossflow with Map sensor and downdraught carb a mild cam and 1300 pistons as was the spec of mine before injecting it. I
think it is still on my laptop and will look for it later this evening.
Paul.
David Jenkins - 14/1/07 at 07:04 PM
Well, apart from the 1300 pistons, that describes my engine quite well!
I would like to see that map, if you can find it - not necessarily to use it as-is (although it won't be too far away) but more to get an idea of
the shape of graph I should be aiming for.
cheers,
David
quote:
Originally posted by paulf
I had a working map for a crossflow with Map sensor and downdraught carb a mild cam and 1300 pistons as was the spec of mine before injecting it. I
think it is still on my laptop and will look for it later this evening.
Paul.
paulf - 14/1/07 at 07:16 PM
It should be a starting point and ran ok on mine , just need to find it as i have loads on the laptop and there not all neatly filed.
I have to go out shortly but will get the laptop out later and try and find it , if I can I will email it to you.
The info on the thread sounds much like I did with mine, at high loads and low vacuum you need the basic advance with a maximium of 36 deg and as the
load decreases the advance should increase .it is really a trial and error type of thing but after some trials you will get a feel for it.
I got a car psu for my laptop from maplins in a sale last year for £19 so may be worth a look.
Paul.
David Jenkins - 14/1/07 at 07:20 PM
Martyn,
Now I've got even more reading up to do! 
quote:
Originally posted by martyn_16v
I've used this method to generate a table as a starting point for a couple of engines,
they've turned out to be pretty close to bang on so far.
Paul,
I've ordered an inverter from Scan Computers - special offer today, just under £17 + P&P & VAT, with multi-standard output socket and a
USB socket that can be used for charging stuff. When I looked up the manufacturer NorthQ I expected it to be Taiwanese or Chinese - turned out to be
Danish. Should be very useful for several things...
cheers,
David
[Edited on 14/1/07 by David Jenkins]
David Jenkins - 17/1/07 at 10:44 AM
Paul,
Thanks for your map - it looks like a useful starting point.
David