Fuel tank level and performance
Discussion
Chaps,
Maybe this has been discussed before but putting the obvious weight increase of a full tank aside, I notice a huge difference in performance in my Chim when at 1/4 tank. In fact its a marked difference from even 3/4 or 1/2 full?? As soon as it sits at around 1/4 its a different car.
Fuel filter recently changed and all injectors cleaned....anyone any ideas could it be a pressure issue, pump, regulator?
I'd expect a difference when full but not this much.
Maybe this has been discussed before but putting the obvious weight increase of a full tank aside, I notice a huge difference in performance in my Chim when at 1/4 tank. In fact its a marked difference from even 3/4 or 1/2 full?? As soon as it sits at around 1/4 its a different car.
Fuel filter recently changed and all injectors cleaned....anyone any ideas could it be a pressure issue, pump, regulator?
I'd expect a difference when full but not this much.
Acceleration...torque...from any rev range ...its literally night and day. Theres a straight and a few bends on a country road near me that I always have a blast down from point to point, just a whole different experience today from two days ago. Its not just this occasion I notice it every time which is why I'm thinking there maybe something more to it than just weight of fuel.
You're probably overfilling the tank and flooding the breather and carbon canister. Therefore not enough air is making its way back into the tank so your pump is trying to suck on a vacuum. By the time the tank is down to a 1/4 the carbon canister is probably free of fuel again and letting enough air back into the tank. The pump is then not trying to suck on a vacuum and is able to deliver the full flow rate.
You should replace the carbon canister, check the breather pipe routing, and make sure you never fill the tank past the first click/auto-stop on the petrol pump.
You should replace the carbon canister, check the breather pipe routing, and make sure you never fill the tank past the first click/auto-stop on the petrol pump.
Not 100% sure Qbee but its starting to make sense...I've been a bit disappointed with the performance since the Cam change and this is the first time the fuel has been at 1/4 since it was completed a week back. Its as I would expect a Chim 400 to perform when mechanically its now strong. But even before the work at 1/4 full it was noticably quicker than it is now when loaded.
Thats what I thought maybe easiest to remove or slacken the cap off and try it out.
Thanks for all the suggestions gents.
Thats what I thought maybe easiest to remove or slacken the cap off and try it out.
Thanks for all the suggestions gents.
dvs_dave said:
You're probably overfilling the tank and flooding the breather and carbon canister. Therefore not enough air is making its way back into the tank so your pump is trying to suck on a vacuum. By the time the tank is down to a 1/4 the carbon canister is probably free of fuel again and letting enough air back into the tank. The pump is then not trying to suck on a vacuum and is able to deliver the full flow rate.
You should replace the carbon canister, check the breather pipe routing, and make sure you never fill the tank past the first click/auto-stop on the petrol pump.
If that were the case, would it not be quite obvious from the amount of fuel vapour smell in the cabin? Z3s have an issue where i you over-brim it then fuel gets sucked into the charcoal canister, it then takes like three days to a week before the car stops smelling like it might conflagrate into a fireball if you drive past a naked flame. When I first discovered this little quirk I was convinced I was gonna end up barbequed before the end of the day. You should replace the carbon canister, check the breather pipe routing, and make sure you never fill the tank past the first click/auto-stop on the petrol pump.
PhilH42 said:
Ah see what your saying..yes could do.
Just being cautious. My canister was removed, but the guy who did it was an engineer, and he routed the pipe to the canister across the car to a one way valve that purges under the car by the front splitter. I didn't know if it was safe to simply disconnect the pipe anywhere near the hot engine.
I am assuming the canister is used to avoid unburnt fuel from destroying the main cat.
I think the can is related to the hydrocarbons and emissions...the tank is vented through the rollover valve and the canister...it is supposed to be taken to the inlet manifold from what I understand. The non cat models vent to atmosphere from memory. Agree not sure I'd want to disconnect near the engine..fuel or fume.
Just as a bit of feedback for anyone else with similar issues or for future I filled to just over 3/4 tank and left the cap off...I took it for a good 30-40 minute drive and it performed pretty good..certainly better than cap on...investigation now starts to see if its all purging correctly.
Just as a bit of feedback for anyone else with similar issues or for future I filled to just over 3/4 tank and left the cap off...I took it for a good 30-40 minute drive and it performed pretty good..certainly better than cap on...investigation now starts to see if its all purging correctly.
Have this with my wedge, perhaps helpfull for you.
My theory: Think if below a certain level...., it takes a lot of time for the remaining fuel to go back to the twin tanks in my case, gravity to feed the swirl pot, through a pre-filter, then at the pump, fuel filter and a couple of meters to get back up front to the injectors...
And the fuel regulator trying to maintain fuel pressure at low levels isn't helping either = stopping fuel to return.
Yes it runs perfect up to the last quarter and knowning that, I then only 'TVR-cruise', which isn't bad as other cars still are disappearing in the back
So fill up and 'normal' TVR mode resumes
Rob
My theory: Think if below a certain level...., it takes a lot of time for the remaining fuel to go back to the twin tanks in my case, gravity to feed the swirl pot, through a pre-filter, then at the pump, fuel filter and a couple of meters to get back up front to the injectors...
And the fuel regulator trying to maintain fuel pressure at low levels isn't helping either = stopping fuel to return.
Yes it runs perfect up to the last quarter and knowning that, I then only 'TVR-cruise', which isn't bad as other cars still are disappearing in the back
So fill up and 'normal' TVR mode resumes
Rob
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