14 replies to this topic

[firefox]

Hi I have a metro 1275 engine High compression 12HA83AA The book says 11 Degrees BTDC
this is for leaded petrol do i need to adjust it for unleaded, the reason i ask is i had super unleaded with red-ex additive in the tank and engine was running super, today as the fuel was low i put a gallon on regular unleaded in as i thought i had over dosed the redex last time and it ran like crap popping and juddering any thoughts would be great

[Frisco]

Super is 98-99 depending on where you got it and regular is 95ron so yeah the ignition timing is different between the two.
Redex makes no difference

[dklawson]

As Frisco said, the timing settings need altering based on the octane rating of the fuel, not so much whether there is lead (or lead substitute) in the fuel.

In general, you retard the timing more and more as you run lower and lower octane fuel. This will prevent knocking and pinging but it comes at a price in power. More retarded timing = less power. However, advanced timing with low octane = pinging & knocking = reduced engine life. It's a trade off really.

[firefox]

As Frisco said, the timing settings need altering based on the octane rating of the fuel, not so much whether there is lead (or lead substitute) in the fuel.

In general, you retard the timing more and more as you run lower and lower octane fuel. This will prevent knocking and pinging but it comes at a price in power. More retarded timing = less power. However, advanced timing with low octane = pinging & knocking = reduced engine life. It's a trade off really.

so am i better off using super unleaded it seems to run cooler on that

[firefox]

I have changed the petrol back to what i had someting has goge drasticly wrong i have had the timing from 4 btdc th 16 btdc with the vacume off and i cant stop the engine popping and it is quite loud i have changed the coil and still the same the dizzy is a new 65dm4 where do i stast looking carbs ignition for the first time today i turned off the ignition and it run on reved up and died

Edited by firefox, 13 October 2011 - 01:43 PM.

[Ethel]

Have a look at the plug colour after a run at least long enough run up to get it up to temperature.

Ignition advance & fuel mixture both have an interconnected effect. It could also be carbon build up, spark plug or valve issues.

[jaydee]

I've noticed that a tuned a-series engine doesnt like more than 30° maximum advance with modern fuels..
By the way 'the more the advance-the more the power' does not suit very well with higher volumentric efficency engines..
Unleaded also needs higher burning temperature to give its best.

[firefox]

Have a look at the plug colour after a run at least long enough run up to get it up to temperature.

Ignition advance & fuel mixture both have an interconnected effect. It could also be carbon build up, spark plug or valve issues.

just had the head done a few weeks ago new springs stem seals gasket and made sure exhaust was air tight, just checked spark on all 4 plugs they are fine ,i am sure it is fuel related , got the carbs off ebay and spent a fortune on them i could have bought new ones, i have a HIF44 i might put that on and see if it runs better

[firefox]

I've noticed that a tuned a-series engine doesnt like more than 30° maximum advance with modern fuels..
By the way 'the more the advance-the more the power' does not suit very well with higher volumentric efficency engines..
Unleaded also needs higher burning temperature to give its best.

Yeah noticed it is running very hot book says 11* btdc is that about right ??

[firefox]

I have set the mixture as haynes manual with the lift pin contact the piston lift 1mm is revs drop off to weak if revs rise to rich
but the left carb i have had to wind down about another 8/10 turns the right one nill only the basic setting 2 full turns now it wont chuffing start, i am pulling my bloody hair out here

Edited by firefox, 13 October 2011 - 05:00 PM.

[firefox]

Anybody know the needle size for my engine for a HIF44

[diogoteix]

98/99 RON versus 95 RON fuel makes quite a difference. I've experience some pinging issues when putting 95 RON fuel because there was no higher grade available at the station.
Leaded/unleaded fuel makes no difference, except for lubrication purposes. The advance your engine will be comfortable with will depend on 3 main external factors (apart from load/rpm): fuel RON grade, engine intake air and water temperature (the higher the temp, the less advance it will be comfortable with).

Cheers

[jaydee]

BDL ?

[firefox]

BDL ?

i gather that is the needle or are you swearing at me ha ha ha had a bad day which is best twin hs2 or hif44

[jaydee]

BDL ?

i gather that is the needle or are you swearing at me ha ha ha had a bad day which is best twin hs2 or hif44

No thats the needle
Keep your HIF44, really, just set it spot-on and it will be perfect for a 1275.