Tune by exhaust gas readings

[willvine]

Hi All I have finally got some time to have a play with my 88 V8 rangie on gas.
I think the last time i posted here I was replacing the ignition modual Lucas type :o. any way it has only lasted 6 months probably a chep ch#A made one. But it was free So i stuck it in. Last weekend i did the bosh ignition upgrade. Thanks again Bee-uty. Since then i have run though a tank of gas 60L usable and my gas economy was quite crap. I usually get 300km on the open road and 250 around town. I think I only got 190 km on this tank.

So i have checked the timing and set it at 6 deg to start with then stuck my flue gas analizer up the exaust to see what the readings were .......

3 readings...


Idle: Co2 = 10.5%
PPM = 1040 approx
ratio = .0091
O2 = 4.7 @ 28%


1500 RPM : Co2 = 10.6%
PP M = 938
O2 = 4.8 @ 29%

ratio = .0089

3000 RPM : Co2 = 11.4 %
PPM = 4055 approx
ratio = .0438
O2 = 3.7 @ 21%

I am no expert so have no idea what these readings actualy mean. other than the car is running great. I will know if the fuel economy has changed next week. My question to more knowlegable people out there is based on these readings is my engine healthy or crap ? or is it just jibber.

Cheers Will.

[bee utey]

I thought gas analysers read CO not CO2. 10% sounds high, should be below 3%. Find some knobs to adjust leanwards. Set the timing to 10 degrees, you will notice the difference.

[willvine]

Ok thanks Bee-utey. yea should read C0 not Co2. oops. I am going for a run tomorrow so hopefully will go thorugh a tank of gas to be able adjust accordingly.

Cheers.

[willvine]

I thought gas analysers read CO not CO2. 10% sounds high, should be below 3%. Find some knobs to adjust leanwards. Set the timing to 10 degrees, you will notice the difference.

I usually have to lean fowards to find my knob too. :D

Will

[MacMan]

Advancing the timing as bee utey suggests should help considerably with efficiency. 6° is way under what the LPG will bear without pinging. My rebuilt 3.9 with 9.35:1 pistons will tolerate 16° on LPG but I've come back to about 12° or 13° for now just to see how it behaves.

[willvine]

Ok seems we are back to good LPG economy I have just squeezed 270kms out of the 60 lt tank mixed freeway and offroad bush bashing.

Timing set at 10deg. Did another exhaust gas test.....

Idle: Co - 4.2 %
Ppm 700
Temp 116 deg
CF. 1130 ppm
Co2. 11%. @. 940ppm @. 0.085. Ratio
o2. 4.2%. 96.2%. Efficiency

I did some googleing and found my exhaust gas figures represent a engine in excellent condition. Ie. the air and fuel going in is being burnt with not much waste 96.2 %.
I searched what is required in the UK to pass the MOT. And for a old rover v8 my results are well within the scale. So very happy .

The tester I have doe,s read co and co2 and lots of other things. So I gues I have a complete rundown on how healthy my engine is,so a bit of piece of mind.I was thinking of pulling it out and fitting a
3.9. But now will keep the 3.5 in until it dies. It has 310000 on it
Cheers will