Bosch 7.0 timing adjustment?

Hello all,

A request for information and opinions on the ignition timing of a V6 motor run by a Bosch 7.0 ecu both the injectors and the plugs are feed from this i.e. no distributor. Its a 3 channel system i.e. the plugs and injectors fire twice per 4cycle. I have fitted a LPG system to this (the petrol is still there for starting from cold). It is said that a LPG system will work better by advancing the ignition by ten or eleven degrees. I have a Snap-on MT2500 scanner and it looks like I could advance the timing with it.

Supposing I can do this

(1) will the timing stay advanced or would the various sensors detect this and return it normal?

(2) if it did stay advanced on LPG what would happen when it was run on petrol would the sensors "knock sensor"? retard the timing if it picked up any rough running of the motor?

(3) would experimenting with a 10 deg adjustment do any permanent damage?

BTW the scanner says the ignition advances by about 35 deg when the motor is revved with no load.

George.

Reply to
George Gosbee
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I was wrong I cant adjust the timing. Would it be possible to fool one of the sensors to get the same result?

George.

Reply to
George Gosbee

If the engines got a knock sensor, it should automatically adjust the timing.

Reply to
Moray Cuthill

Thanks for the reply.

It has and I have just tested it on petrol and lpg and get the same advance reading on both or are you saying the knock sensor will retard it if I manage to advance it for lpg?

George.

Reply to
George Gosbee

The ECU will start with a base timing figure, lets say for arguements sake-

10deg BTDC. It always tries to reach this figure but usually doesnt due to engine pinking or knocking, which it reads through the knock sensor. When this happens it will retard the timing a set amount (usually 2 degrees) immediately for 4 crankshaft revolutions before trying to advance it back.

After a while the ECU will have stored what is the most advanced timing it can get away with at various loads / temperatures / revs etc and rarely will it get a 'i'm knocking' signal back from the KS.

Obviously for LPG , you may want a base timing figure which is more advanced than the ECU's base figure, so in practive you will never reach this figure as the ECU isnt programmed to pass it. The only way around this is a custom map, a custom ECU or an RPI style timing advance interceptor, which when you switch to LPG it gives you x amount of additional advance on whatever the ECU is saying...

Tim..

Reply to
Tim..

Thanks,

I agree the remapping would work but would be prohibitively expensive.

Yes but the HT coils are directly controlled by the ECU so cant see how an external device would advance the timing?

George.

Reply to
George Gosbee

RPI's device records timing advance on stroke 1 and lets it pass through. On stroke 2 the device intercepts the timing signal, adds the programmed advance then fires the coil. At the same time it checks to see if the recorded signal on stroke 1 matches that on stroke 2. If not, it recomputes an advance figure for stroke 3. etc etc etc.

Tim..

Reply to
Tim..

I can understand that.

On BRCs web site the modified feed to the coils is by way of the earth so will have to see how the earth is connected as it may be part of the coil mounting. The 3 coils surround the 3 front plugs with ht leads to the back

  1. George.

Reply to
George Gosbee

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