First problem is that I've messed with it again

Car is laggy and horrible, then all hell breaks loose

But as I shift gear the fuel pressure drops 0.5 bar

It appears to be just a transient "thing", but my tame mechanic Ben says I need a lift pump and a swirl pot, plus a Bosch to feed the engine, which I'd rather not bother with if I can.

Currently using a Walbro and a Fuellab regulator at 4 bar static, but Mark @ Lateral is bringing me some bigger injectors on Sunday, so hope to reduce this back to 3 bar once re-re-re-mapped !

Any advice or experience of similar issues, feedback appreciated.

dunx

P.S. Ben laughed as much as I did at my laggy monster's behaviour...

 

Dunx,


Fuel pressure tracks boost pressure, so when you lift off, or change gear, pressure will drop.

 

Hi Mark, will call you later...

I didn't mention that I'm running Defis in differential mode, so the fuel pressure usually used to be rivetted to the 4 bar marker.

And under flat-chat acceleration the pressure is fine.

It just droops whilst shifting, which it never did before...

Cheers,

dunx

P.S. Mark, add your phone number to your user I.D.

 

You could avoid the hassle of the swirl pot and external pump and go for a larger walbro fuel pump from Mark. Number for Lateral under my avatar

Banny

 

Mark's bringing me one Op Narth at the wekend...

But I don't understand why the fuel pressure is drooping as I shift gear, it was fine with the "H" fitted...

As she does get some track action a swirl pot was inevitable TBH.

dunx

 

can u plug a laptop in and log the pump duty?, you will see it drops to 33% at normal throttle and increase when you WOT etc,
This could explain the change.

 

Just a thought- had similar issues for a while, and ended up going through 3 different fuel pumps til one worked properly.

Perhaps at 4 bar the pump has had enough and is behaving erratically?

I presume you have checked no probs with the vacum lines to the fuel pump? Or maybe the fuel pump is fine, and its just the Defis being weird.

 

Driving it carefully nothing is seen, but with a 2nd pair of eyes... so I could concentrate on pointing the car, this droop was observed.

The only difference is the bigger turbo, pump is fine under flat-out acceleration, then dips as I change up... and instantly goes straight back to 4 bar ! The reason it's annoying is that I have the alarm set at 3.9 bar...

Odd... next test is to swap the boost hose to the regulator

Yes, Grant it's had over three years of use, only the last two at the increased pressure.

Cheers guys,

dunx