Oops, another 2 month update!
First, pics of the ghost logo after removing the Volvo mask :
After lacquering and at a few different angles :
In other news, it's also gained a 3.54:1 back axle which has improved economy and made it quieter at cruising speeds. It also cured the noisy diff that was rumbling much worse than i originally thought. In fact, i thought i'd gone completely deaf the first time i drove it afterwards!
It gave me two more problems though. First, the speedo read half of what it should have done, Second, the ABS light comes on at 20+mph.
For some unknown reason, Volvo fitted 1988 cars with ABS with a 96 tooth reluctor ring in the diff - all newer ones were 48 teeth.
THe speedo was originally designed to work with a 12 tooth rin, as per earlier 7xx models without ABS so they had Bosch design and build an ABS converter which taps off the signal from the rear sensor and divides it by 8 (96/12 = 8) to make the speedo read correctly. Bypassing the converter on the new axle had it reading 4 x the real speed (48/12 = 4) which gave me a clue to what the converter was doing - dividing ny 8 to give the correct number of pulses to the speedo from a 96 tooth reluctor ring triggering the speed/ABS sensor in the diff.
Now it only has 48 teeth, it showed half the speed.
Pulling the converter out and investigating the insides of it i found a divide by n counter where n is 2 to the power of the bit number used for the output. On the main chip, the 4024, there are 8 output bits, from 2^0 (=1) to 2^7 (128) and the 3rd output bit (2^3 = 8) was used on pin #9 of the chip. That in turn was linked to the op-amp so i cut the track and soldered a coper link wire to the op-amp side of the cut and the other end to pin #11, 2^2 (4) as the output so the input frequency is divided by 4 now instead of 8, correcting the speedo.
First problem solved!
Second problem is the ABS light - the ABS ECU gets the raw signal from the diff sensor so no hope of doing similar with that. Tried a later ABS ECU but overlooked (due to a migraine when i cheked the circuits) an important link that mine doesn't have within the ABS modulator. Anyone that needs a late 9xx ABS ECU, i have one available!
Luckily the ABS light doesn't come on until 20+mph so it passed the MoT today I have a few ideas in mind of how to solve this problem, will add details as and when i find which one works!
Meanwhile i've started the LPG conversion :
Only got the switch mounted so far but, hey! It's a start!
