random misfire fuel supply related?
Discussion
I've had my GT4 for 6 years and get a strange thing happening when I have 1/4 of a tank of fuel or less. The power totally dies if I go round a roundabout or sharp bend at a reasonable pace. I understand this will be due to the fuel sloshing about in the tank and moving away from the pickup.
I also get a strange misfire occasionaly (when I have less than 1/4 of a tank) if I'm poodling along and then floor it to overtake for example. It isn't the same as when turning right sharply (power just dies) but it pops and bangs and has no power about 1 to 2 seconds after flooring it, the power will then come in and all is well, it's not overboosting as all the gauges state no real boost levels reached. Any ideas? What else related to engine running could possibly change when low on fuel? (still at least 2 gallons of fuel left in a 68 litre tank) The reason I'm thinking it is a different thing happening is the added popping and banging I get.
I have an aftermarket ECU (Apexi power FC)which was professionaly mapped a couple of years ago to 356bhp running safe parameters and the monitor for that shows no alarming levels of injector duty, knock, boost, revs or intake temps.
I know the simple answer is not to have less than 1/4 of a tank of fuel but wanted to know if the misfiring would also be caused simply by the pickup not getting fuel momentarily (?sp?) as gravity pulls the fuel to the back of the tank, if it is then why do I get the banging but dont when I go round a roundabout?
1/4 tank isn't a guarantee it will do it but the only time it does is when at those fuel levels.
Any suggestions (other than keep the tank topped up) gratefully received.
I also get a strange misfire occasionaly (when I have less than 1/4 of a tank) if I'm poodling along and then floor it to overtake for example. It isn't the same as when turning right sharply (power just dies) but it pops and bangs and has no power about 1 to 2 seconds after flooring it, the power will then come in and all is well, it's not overboosting as all the gauges state no real boost levels reached. Any ideas? What else related to engine running could possibly change when low on fuel? (still at least 2 gallons of fuel left in a 68 litre tank) The reason I'm thinking it is a different thing happening is the added popping and banging I get.
I have an aftermarket ECU (Apexi power FC)which was professionaly mapped a couple of years ago to 356bhp running safe parameters and the monitor for that shows no alarming levels of injector duty, knock, boost, revs or intake temps.
I know the simple answer is not to have less than 1/4 of a tank of fuel but wanted to know if the misfiring would also be caused simply by the pickup not getting fuel momentarily (?sp?) as gravity pulls the fuel to the back of the tank, if it is then why do I get the banging but dont when I go round a roundabout?
1/4 tank isn't a guarantee it will do it but the only time it does is when at those fuel levels.
Any suggestions (other than keep the tank topped up) gratefully received.
I suspect all the issues are down to fuel surge.
Simple answer is to fit a surge pot.
The injection pump will then need to be diectly below the pot so may mean you need to buy another pump.
Low pressure loop.
Fuel is pumped from tank to pot and any excess is returned to the tank. There is no pressure regulation on this loop so a fairly basic pump could be used provided it has sufficient flow.
High pressure loop.
Fuel is pumped from pot to fuel rail then from pressure regulator back to the pot.
You should include filters in both loops.
The principle is that there will always be about a litre of fuel sitting right above the high pressure pump even if the tank pickup is pulling air due to surge.
Steve
Simple answer is to fit a surge pot.
The injection pump will then need to be diectly below the pot so may mean you need to buy another pump.
Low pressure loop.
Fuel is pumped from tank to pot and any excess is returned to the tank. There is no pressure regulation on this loop so a fairly basic pump could be used provided it has sufficient flow.
High pressure loop.
Fuel is pumped from pot to fuel rail then from pressure regulator back to the pot.
You should include filters in both loops.
The principle is that there will always be about a litre of fuel sitting right above the high pressure pump even if the tank pickup is pulling air due to surge.
Steve
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