1963 Triumph Spitfire Mk1 Maps

Nige · Post by **Nige** » Fri Jan 22, 2010 4:53 pm

First a quick explanation of how these maps came about....

The attached are the maps worked out from the factory workshop manuals. These are very different from any other spitfire mark as the amount of advance required decreased dramatically from the mk3 onwards. If my conversions, or any of the working out seems wrong please let me know?

I used the following calculator in my conversions...
http://www.convertunits.com/from/inch+o ... kilopascal

First, just as a comparison. I noticed from the manual that from the mk3 spitfires (1300cc) the maximum kPa for maximum vacuum advance was at a much higher kPa than the earlier mk1 (1147cc) engine.

I've simplified here, i.e not considering the higher vacuum from overrun when closing the carbs from high rpms and I've removed the decimal (converted up/down) in the conversions.

For instance, the mk3 1300s vacuum advance at is at a normal sounding 22 inHG (22 inHG = 74 kPa). As the MJLJ reads absolute, that would be 102-74 kPa = 28 kPa on the MJLJ. This is, I believe, what you'd expect to see.

In comparison, on the Spitfire mk1 1147cc engine, the specs give a full vacuum measurement at only 10 inHG. 10 inHG (10 inHG = 34 kPa). For the megajolt reading, this would be 102-34 kPa = 68 kPa !!!.

The inHG figures are straight from the factory workshop manual and for the mk1 read as the following.

Idle Speed 700 rpm
static advance: 13 deg
dynamic adv at idle 15 deg (it originally had SU carbs with the ported vacuum behind the butterfly valve, so no vacuum at idle)
Max mech advance 39@3000 +-2
Max advance with vacuum 59 +-4

(Sorry about the formatting here)
MECHANICAL ADVANCE
distributor Rpm - distributor adv - crank rpm - crank adv
1450 - 11 to 13 - 2900 - 22 to 26
1200 - 9.4 to 11.4 - 2400 - 18.8 to 22.8
900 - 7.4 to 9.4 - 1800 - 14.8 to 18.8
500 - 0 to 1.5 - 1000 - 0 to 3

VACUUM ADVANCE
Inches HG - MJLJ kPa - crank adv
2 - 95.2 to 100 - 0
2.5 - 93.5 - 3
3 - 92 - 6
5 - 85 - 6 to 14
6 - 82 - 10.5 to 16
7 - 78 - 14 to 18
8 - 75 - 16 to 20
9 - 71.5 - 17 to 21
10 - 68.1 - 18 to 22 Maximum

If the above conversions are correct, the maximum vacuum for the standard mk1 required would be at 68 kPa and 102 kPa would be atmosphere as normal.

These maps gave me an excellent starting point for my current map.

Anyway, here are the current maps, please feedback if any of my conversions seem incorrect and I'll improve as I can. As there is a range in the manuals, the maps are set up for the low range, mid range and the high range. I've also included the one that I'm currently running with on a heavily modified engine.

I'll be getting this on a rolling road within the next couple of months, so I'll post the map that results here too.

vehicle: Trimph Spitfire Mk1
year: 1963
Engine Mfg: Triumph
Displacement (cc): 1147
TPS or MAP: MAP
Boosted or Normally Aspirated: NA
relevant external mods: Sports header/exhaust, twin Kehin CR Special carbs, MJLJ 4.0.2
engine mods: larger stainless exhaust valves, compression 10.1:1, port/polish, lightened flywheel, balanced (crank(shaped), flywheel, clutch, conrods), race valve springs, hardened valve seats for unleaded, rebored +40, piper 270 cam

Additional: I've now posted the spreadsheet that I used to calculate these maps from the factory manual. It also includes a simple inHG to kPa converter for the Megajolt measurements. It's posted here, http://www.autosportlabs.org/viewtopic.php?t=2632.

***UPDATE***
The spreadsheet has been updated with a clearer layout and a much better converter. http://www.autosportlabs.org/viewtopic.php?t=2632.

Nige

Nige · Post by **Nige** » Fri Jan 22, 2010 5:00 pm

Here's my current working map. It's modified from the mid range map above and I've tried to simulate the original ported vacuum type for idle advance.

As the original vacuum on this car was the ported type (no vacuum registered at the distributor at idle), I've set the idle rpm/Kpa advance value to 15 dgrees , the same as it would be when using a ported vacuum.

The only problems I have is that although a vacuum gauge shows 19 inHG at idle, the megajolt registers this as 54Kpa, hence the higher vacuum Kpa range on the map at idle.

***UPDATE***
I've also ended up a long way from stock with my current map. Still working on it, but it's pulling hard to redline and running at fairly good AFRs across the board, so far. Rich off idle, but that's a fueling issue,

. Latest map attached below.

Latest map attached. See car spec at the end of the previous post .

Nige