Power Vs Fuel Levels

[coyote_dc5]

Has anyone ever noticed a difference in power between a full or Low tank?

I'm not referring to the fact your lighter as my experience is the opposite. For some strange reason (fuel pressure?) my teg pulls harder with a full tank than when low say below 1/4

I actually did a 70-100 test (on private roads) in 5th to test this all on same day to rule out atmosphere pressure and temps

So before light was on I managed a 6.2sec pull but after filling it was 5.8 and that even bring approx 40KG heavier with fuel!

Both pulls were done on a flat road surface too

Anyone experienced the same and know possible causes?

Sent from my Z10 using Tapatalk 2

 

[Crazylegs]

Can't say I've noticed as I never run a full tank but interesting nonetheless Dan.

Something I have noticed is that my car goes better in hot weather rather than cold which you'd have thought would be the other way round with the cold air being more dense.

Unless I'm imagining things, definitely pulls better or feels that way.

 

[beppe786]

Has anyone ever noticed a difference in power between a full or Low tank?

I'm not referring to the fact your lighter as my experience is the opposite. For some strange reason (fuel pressure?) my teg pulls harder with a full tank than when low say below 1/4

I actually did a 70-100 test (on private roads) in 5th to test this all on same day to rule out atmosphere pressure and temps

So before light was on I managed a 6.2sec pull but after filling it was 5.8 and that even bring approx 40KG heavier with fuel!

Both pulls were done on a flat road surface too

Anyone experienced the same and know possible causes?

Sent from my Z10 using Tapatalk 2

might not be anything to do with fuel or car weight

could be intake temps/ oil temp have cooled down in the 10mins , cooler intake + cooler oil more oil pressure.. = more power

ive found shorte hamp oil filter does give slight more oil pressure but car oil temp overall get hotter, maybe larger filter acts as a tiny oil cooler.. im switching back to larger one

 

[davidpingu]

I've always thought the same Dan but can't quite come up with any reason how it could change the characteristics of the car. It would be interesting to know if the car is any more economical on its last 1/4 tank than when full I think. Some modern ECU 's deliberately down power the car slightly to make that last bit last longer but I don't believe it was a feature for our cars?

 

[coyote_dc5]

That's a good point David, never thought of that

Glad other people experience the same though

Not sure on the oil temp one Beppe as this happens all the time not just immediately after filling. So generally first 3/4 of tank feel normal then last 1/4 sluggish where as it should feel quicker as there's a lot less weight almost a small persons worth!

Sent from my Z10 using Tapatalk 2

 

[CaLi]

I notice this when its low on fuel, almost like there is less pressure. But the fuel pump would maintain the pressure. Perhaps the ecu does reduce flow on low fuel

 

[beppe786]

i don't think the ecu on our teg reduces flow.. i get bad fuel cut when im below 1/4 tank as i need more fuel than pump can supply

heard people have modified and upgraded to the s2000 pump as can supply more fuel then dc5 one

 

[coyote_dc5]

So it's not a kpro thing if yours does it too Ian. Must be buried deep within the stock ecu

Wonder if kpro can override it. Imagine how quick we could be going with 1/4 tank of fuel!!

Sent from my Z10 using Tapatalk 2

 

[beppe786]

you should try this when your down to 1/4 tank stop car 10mins and go open the fuel cap let air out and go see if it makes a difference without fueling up..

 

[CaLi]

I do notice when you fill up when low, you open the cap and it hisses out air

 

[beppe786]

could be teg needs to release some air.. lol

 

[Wingnuttzz]

The Evap sensor should control tank pressure though.

Or for those of us who delete it, it just vents to atmosphere, if you block it off you end up with pressure building in the tank.

 

[coyote_dc5]

If it works then I know what I need to do when I'm faced with any private road beep beeps

Sent from my Z10 using Tapatalk 2

 

[Brecht]

perhaps it's because when the tank is full , the fuel gets more time to cool down .
If you are low on fuel , the small amount in the tank gets send back to the engine more often?
just an idea really

 

[C&S Evo7]

the stock ecu doesnt control the flow on the pump or the pressure, the pressure is controlled mechanically via the reg on the fuel rail.

on the track the car always laps faster when its low on fuel

 

[Rom]

Average fuel pumps will draw about 1 amp per bar of pressure.
So you could check the current draw to see if its any different between low and full fuel.

Ive never known any car to cut power at 1/4 of a tank. That would be way too high. Manufacturers already under quote the remaining fuel on empty to give you a fighting chance.

Ive worked for Toyota, Hyundai, and VW main dealers, and have never known, or been taught in my training about any power reduction at low fuel levels. While it may sound logical, conversely, less power, will mean more load on engine, resulting in less fuel economy. Think 6th gear at 2000 rpm, needs a lot more throttle load than being in 4th gear at 4000 rpm to accelerate well.

Its incredibly hard to accurately gauge things like this. You would have to do multiple tests, and take averages. Even on the same day, tyre temps, tyre pressures, intake air temps, oil temps etc will vary.
When dealing with 100ths of a second, it can be anything that can make a difference.

But less weight = quicker, this is pretty much an exact science.

As a side note....these have 1 fuel line running from the tank, so there is no return to the tank itself.

 

[beppe786]

As a side note....these have 1 fuel line running from the tank, so there is no return to the tank itself.

fuel return line help maintain pressure.. on my too do list..

 

[coyote_dc5]

When I was data logging today I noticed by pressure is 5.7kpa if this means anything to anyone!?

Sent from my Z10 using Tapatalk 2

 

[Rom]

Kilopascal.

Though that's only 0.057 bar?!

Manual states 320 - 370 kpa at idle.

Sent from my SM-N9005 using Tapatalk

 

[coyote_dc5]

Surely something not right with that reading as it wouldn't run if it was really that low. Anyone else got kpro to check their fuel pressure (PTANK from memory)

Sent from my Z10 using Tapatalk 2