Hi,
Just got my Marcos on the road after 4 years, happy days.
I have the engine (5.0 rover v8 with Edelbrock carb) with a Megajolt system and already mapped out for me and is working as confirmed by laptop and sounded sweet on the testbed when i collected the engine.
When i quckly rev the engine i get a loud bang from the exhaust and when driving normally it bangs also intermitentally.
I have adjusted the 2 idle mixture screws which i understand as it says only adjusts the mixture at tickover.
So, is the banging noise a lean or rich mixture when running, i have a fuel pressure regulator set at about 4 and the adjusting screw is almost fully in on the regulator and i have used the original fuel pump which has been sitting for 4 years and does make a knocking noise when pumping fuel but, i am guesssing its not either of these perhaps restricting fuel as the fuel already in the carb chambers would overcome that.
My knowledge on these matters is very limited so are loath to start messing without some advice, over to you please,
Martyn.
Exhaust banging noise
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Hi,
Thanks for the reply, that could be a good indication as i have done much messing with the exhaust system trying to get better ground clearance. I shall have to investigate further.
Question, if there was a leak what would the bangs be and do you think the leaks would be connections to the silencer boxes or the downpipes, i have had to put a couple of extra gaskets between heads and downpipes to help get chassis clearance,
Martyn....
Thanks for the reply, that could be a good indication as i have done much messing with the exhaust system trying to get better ground clearance. I shall have to investigate further.
Question, if there was a leak what would the bangs be and do you think the leaks would be connections to the silencer boxes or the downpipes, i have had to put a couple of extra gaskets between heads and downpipes to help get chassis clearance,
Martyn....
Hi
The banging and popping in the exhaust when you let air in is detonation of the residual unburnt hydrocarbons left over after combustion, it normally occurs on very light throttle or over run as the combustion mixture is usually so mixed with exhaust gasses that most of it is still unburnt by it reaches the exhaust, add more oxygen to this hot parcially combusted exhaust gas and it explodes, hence the popping.
If the chemestry is of any interest then the reaction can be thought of happening in two stages, hydrocarbon (nX(CH2))H2 fuel plus oxygen (O2) partially combusts to carbon monoxide (CO) and hydrogen (H2) then the next stage burns this mixture with more oxygen to carbon dioxide(CO2) and water (H2O) releasing most of the energy. On over run or cruise where you get dilution of the charge with burnt exhaust products you get some conversion of the oxygen to oxides of nitrogen (NO, NO2) and the second half of the combustion does not take place properly. . When you add more heat and more oxygen as it enters the leaky exhaust system you then get very rapid burning and detonation as the extra oxygen completes the combustion to CO2 and water and the oxides of nitrogen then brakek down aswell with the CO and H2 to give H2O and CO2.
Most likley to be leaks in the down pipes and probably where the primaries join as this area has pulses that return to the port area where at a guess this is where the actual pops and bangs are happening.
best regards
Mike
The banging and popping in the exhaust when you let air in is detonation of the residual unburnt hydrocarbons left over after combustion, it normally occurs on very light throttle or over run as the combustion mixture is usually so mixed with exhaust gasses that most of it is still unburnt by it reaches the exhaust, add more oxygen to this hot parcially combusted exhaust gas and it explodes, hence the popping.
If the chemestry is of any interest then the reaction can be thought of happening in two stages, hydrocarbon (nX(CH2))H2 fuel plus oxygen (O2) partially combusts to carbon monoxide (CO) and hydrogen (H2) then the next stage burns this mixture with more oxygen to carbon dioxide(CO2) and water (H2O) releasing most of the energy. On over run or cruise where you get dilution of the charge with burnt exhaust products you get some conversion of the oxygen to oxides of nitrogen (NO, NO2) and the second half of the combustion does not take place properly. . When you add more heat and more oxygen as it enters the leaky exhaust system you then get very rapid burning and detonation as the extra oxygen completes the combustion to CO2 and water and the oxides of nitrogen then brakek down aswell with the CO and H2 to give H2O and CO2.
Most likley to be leaks in the down pipes and probably where the primaries join as this area has pulses that return to the port area where at a guess this is where the actual pops and bangs are happening.
best regards
Mike
poppet valves rule!
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Hi,
Exhaust taken off and refitted and confident no leaks in system however still banging under acceleration and not smooth under power, starting to think it's maybe a timing issue, especially as I recall that when putting the engine in I did move the trigger wheel slightly however have adjusted it exactly as per the book going by the auto sport labs website.
The engine builder is miles away so not really an option to take it there and not aware of any tuners in the West Midlands area who have any knowledge of the Megajolt system unless you can recommend somebody for me.
A ignition Timing light on the crank pulley shows 8 degrees before with the Megajolt system unplugged when idling and when I plug the Megajolt system back in on idling the laptop shows ignition advance 15, it idles at 900rpm.
The global controller options shows the following,
Cranking advance 12 degrees
Trigger offset 5 degrees
Edis pip filter level. 10
Can somebody tech minded point me in the right direction please, I think I can post a copy of my map on here if this will help,
Regards,
Martyn
Exhaust taken off and refitted and confident no leaks in system however still banging under acceleration and not smooth under power, starting to think it's maybe a timing issue, especially as I recall that when putting the engine in I did move the trigger wheel slightly however have adjusted it exactly as per the book going by the auto sport labs website.
The engine builder is miles away so not really an option to take it there and not aware of any tuners in the West Midlands area who have any knowledge of the Megajolt system unless you can recommend somebody for me.
A ignition Timing light on the crank pulley shows 8 degrees before with the Megajolt system unplugged when idling and when I plug the Megajolt system back in on idling the laptop shows ignition advance 15, it idles at 900rpm.
The global controller options shows the following,
Cranking advance 12 degrees
Trigger offset 5 degrees
Edis pip filter level. 10
Can somebody tech minded point me in the right direction please, I think I can post a copy of my map on here if this will help,
Regards,
Martyn
Given that you moved the trigger wheel, you should check the gap at the sensor. It should be between 0.5mm and 1.0mm from the trigger wheel. The timing at tickover with the megajolt disconnected should be 10 btdc steady, not 8 btdc.martyn123 wrote:Hi,
Exhaust taken off and refitted and confident no leaks in system however still banging under acceleration and not smooth under power, starting to think it's maybe a timing issue, especially as I recall that when putting the engine in I did move the trigger wheel slightly however have adjusted it exactly as per the book going by the auto sport labs website.
The engine builder is miles away so not really an option to take it there and not aware of any tuners in the West Midlands area who have any knowledge of the Megajolt system unless you can recommend somebody for me.
A ignition Timing light on the crank pulley shows 8 degrees before with the Megajolt system unplugged when idling and when I plug the Megajolt system back in on idling the laptop shows ignition advance 15, it idles at 900rpm.
The global controller options shows the following,
Cranking advance 12 degrees
Trigger offset 5 degrees
Edis pip filter level. 10
Can somebody tech minded point me in the right direction please, I think I can post a copy of my map on here if this will help,
Regards,
Martyn
If you move the wheel anticlockwise slightly and get this value then you need to set the trigger offset to 0.
It would be interesting to see the map if you can load it on here.
Regards Denis
1950 A40 Devon Hotrod with 5.0 twin turbo RV8.
EDIS8 wasted spark, Holley Injection.
Been as far as the Moon and back in 57 years of driving. Same Car, 5 engine upgrades !!!
EDIS8 wasted spark, Holley Injection.
Been as far as the Moon and back in 57 years of driving. Same Car, 5 engine upgrades !!!
Phew,
Engine now pulling like a train, I had number 7 & 8 connected the wrong way round, and number 8 was not sparking at all, found out by putting a timing light sensor on each lead and getting no repsonce on number 8. Changed the spark plug and all sorted.
Will run engine in properly now and then get it on a rolling road for fine tuning,
Martyn.
Engine now pulling like a train, I had number 7 & 8 connected the wrong way round, and number 8 was not sparking at all, found out by putting a timing light sensor on each lead and getting no repsonce on number 8. Changed the spark plug and all sorted.
Will run engine in properly now and then get it on a rolling road for fine tuning,
Martyn.
I'd make sure your trigger wheel is adjusted correctly before the rolling road session.
Ideally it should be spot on with no need for trigger offset, however it is almost impossible to get it dead right so give it a go and any remaining angle should be accounted for with trigger offset (My trigger wheel is 1 degree out).
You say you have it running at 8 degrees with Megajolt unplugged - you should be seeing 10 degrees when EDIS is running standalone. However from your post your trigger offset is set to 5 degrees when really you actually need to correct only for 2 degrees.
Best way to correct trigger angle in software (because I can never remember which way is positive and which way is negative) is to:
1. Backup your current map to a file somewhere.
2. Create a map with 10 degrees advance in all cells.
3. Upload this new map to the Megajolt.
4. Start car.
5. Verify the advance actually being commanded with timing light.
6. Make any corrections to this with the trigger offset value until what you see on screen matches what your timing light sees.
7. Now resend your "real" map back to the controller, ensuring that you keep the same trigger offset value you just worked out.
8. Done.
Programmable ignition was one of the best upgrades I have done to my motor- can't recommend it enough!
Have fun
Ideally it should be spot on with no need for trigger offset, however it is almost impossible to get it dead right so give it a go and any remaining angle should be accounted for with trigger offset (My trigger wheel is 1 degree out).
You say you have it running at 8 degrees with Megajolt unplugged - you should be seeing 10 degrees when EDIS is running standalone. However from your post your trigger offset is set to 5 degrees when really you actually need to correct only for 2 degrees.
Best way to correct trigger angle in software (because I can never remember which way is positive and which way is negative) is to:
1. Backup your current map to a file somewhere.
2. Create a map with 10 degrees advance in all cells.
3. Upload this new map to the Megajolt.
4. Start car.
5. Verify the advance actually being commanded with timing light.
6. Make any corrections to this with the trigger offset value until what you see on screen matches what your timing light sees.
7. Now resend your "real" map back to the controller, ensuring that you keep the same trigger offset value you just worked out.
8. Done.
Programmable ignition was one of the best upgrades I have done to my motor- can't recommend it enough!
Have fun
1974 Rover 3500s
1984 3.5 90
1959 2.25 series 2
1984 3.5 90
1959 2.25 series 2
