@nascarMy vehicle is used only on petrol during it
s tenure of usage.NO CNG---vehicles with CNG loose there piston compression ratio by 30-40% after 10-15000km running.This adds in loss of economy/km.3.00`,it can be taken to 2.80 but vehicle feels like dragging itself rather then accelerating(mild feeling is there but not noticable)
Setting a vehicle on Petrol is very easy rather than CNG(Stable tune up/settings attained with no retune up hassle till 7000-10000km).CNG now days is not good quality and pressure mostly is poor thus mostly resulting in bad mileage.Pump in islamabad having good gas pressure with auto facility to check pressure in cylinder of vehicle and then refill it according to the difference with monitoring main pipe pressure and temperature of surrounding is PSO pump on road going towards China chowk or polyclininc hospital from Super Market(Mr.book/famous book side).Pumps in Islamabad having excellent quality feul and no cheating issue during refills is PSO f-8 markaz Islamabad & PSO diplomatic Enclave Islamabad.
My vehicle setting:-
1. Timing at company advised angle done via mechanic.
2. Spark plug(Autolite AP-3923 Platinum) Gap 0.63mm(Company recommended is 0.80mm)
3.Sprayed carburator feul points and nozzles with WD40
4.CO mixture setting
I run my vehicle(In local) under 60km/hr speed in 4th gear.Shut my engine OFF on long waiting signal lights.Avoid sudden braking and acceleration.A/C 30% usage.Check tyre pressure weekly and keep them inflated around 29psi (Dunlop Lemans701 175/70 R13).Clean air filter element weekly. Local mileage 12.6km/L
Same specs as above with engine rev to 4000rpm with every gear.Hard braking.Trip to Rawalpindi(Morgah) from Islamabad via Airport with full load 100% A/C.Daily rash driving above 110km/hr speed.local mileage 10.9km/L.This way of driving was used to see the difference on mileage with driving style.Mehran city 8.5km/L and with rash driving 7.8km/L
CNG Potohar had issues of having problem in maintaining idle speed and would tend to accelerate when idle when vehicle attained working temperature(Warm).Pick was poor and hardly could be run on Petrol.Engine would tend to heatup at idle state--more than 6 min(The vehicle engine has been completely overhauled some 800km ago)Things i did:-
1. Spark plug cleaning Gap 0.63mm(Recommended 0.80mm)
2. Installed Vacuum pipes as they were missing
3. Covered all exposed wires with insulating tape
4. Opened and cleaned distributor cal contacts and rotor.
5. Cleaned the air filter element(No obstruction material present for air flow--standard unit)
Still problem solved by 30% but pick poor and idle engine missing extensive
Then I opened the pipe for air connected to Carburator and sprayed WD40 in the carburator.Disconnected vacuum pipe between distributor and carburator and sprayed WD40 in them.Opened the slow jet adjuster screw protector and unscrewed the adjustor.Sprayed WD40 in it.Opened the cover over a small pit over which lies the one way valve of vacuum and sprayed WD40 in them.On examining adjustor found a 3 holes meant for feul and sprayed them with WD40.Started engine.Excellent Idle engine with no missing.Shift to petrol on one sulf not more than 6 sec or in running condition in 1 sec.Pickup exceelent with top speed of 122kmHr on CNG and if road leveled or slightly downward then 136km/hr on CNG.Problem is that feul has minor deposit issue which mostly cleans with usage of high octane but need to clean carburator or Injector body via WD40 after 6000km usage is recommended whereas Gas is dry which leaves high level of deposits then petrol and recommended cleaning time is 2000km.Petrol is liquid and thus it mostly washes the mild dust particles entering carburator via air duct thru filters whereas CNG is liquified(Under pressure as Law of Physics)gas which when released changes to gas form.While conversion, it gives the passage an oily nature which results in attachment of mild dust particle deposit which over the usage becomes increased and cause obstruction to normal function & flow of feul and Gas thus requiring frequent cleaning.
For heatup Issue,as fan is belt type runs with engine thus slow at idle state.I installed a new electronic fan with relay which is connected to a button inside the cabin.When at idle state and engine temp starts to rise, i just turn it on and engine temp goes down.Daily filling of water in reservoir.This example is there for you to get an idea.
As for the CO setting method,Buy a good digital meter.Set it at 20dcv.Connect the red wire to the CO setter centre wire after removing covering rubber,located near the right shock assembly near the fendor.Connect black wire to engine body block.be careful that loose wires should not get entangled in the engine belts.Remove plastic yellow cap from the adjusting screw over the CO setter unit.Start engine and set reading.Best reading is 3.33 then 3.80 and 3.00 or 2.80(rarely.good mileage,low acceleration).Lower the settings better mileage.After setting to new location,observe your engine RPM for missing.Mild Rpm variation between 900-1000rpm is normal but if sudden decrease of RPM for .2 sec occurs below 800rpm then readjust CO to knew setting.Keep the best suitable setting.
NOTE:- Always perform this procedure when engine temp in green area or after 5min driving minimum with temp in green position