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Wallby

Mi16 twin Dellorto fueling issues

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Wallby

Hi all, 

 

I managed to get my new 205 out at Llandow last weekend for my first track day with it. I've had it running on the road for a short while and put it in for a tuning/carb check the week before the track day. They had a few issues with the pump jets leaking, but once that was sorted it was dynoed at 170bhp.

 

The main issue at the track day was that every time I came off the last corner, a long right hander, there was no power.

 

My immediate thought was fuel surge, but I'm not sure how that works with the bowls in the carbs holding an amount of fuel. The current setup is a facet cylinder type pump on the inner wing, feeding a fuel regulator set at 3psi and then on to the carbs. The fuel pick up is also non standard, just an alloy tube into the tank with no return. 

 

I haven't had the car that long so still trying to work through all the things that need attention. Any suggestions/ideas on how to sort it before I start fiddling? 

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Tom Fenton

Easiest way to see if it’s surge is fill the tank right to the top. If that makes it better the chances are it is fuel surge/starvation.

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Wallby

The tank was between 3/4 and full which I thought would have been plenty. I can't get it to do the same on the road either. Maybe it's an issue with the pump not keeping up? I'll have to check if the pump is OK. 

 

I did try hooking up a fuel pressure gauge yesterday on the regulator outlet, and the pressure did drop when accelerating, not sure if that is normal or not 

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Richie-Van-GTi

is the Facet having to lift from the tank? It seems like a long lift from the tank to inner wing. If it gets even a small amount of air in a line that long it will take a while to recover. Try modifying the pick up so its still in a complete housing as it will retain a small amount of fuel around the pick up a little bit longer. If you intend to track it a lot I would suggest a swirl pot and a low pressure in tank pump to keep it full.

Edited by Richie-Van-GTi

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Reebmit

I had same but now run a swirl pot and all good now..... you don’t want too much pressure with carbs.....

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Edited by Reebmit
Additional info

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Wallby

Thanks guys. I've ordered a fuel pump housing so hoping that will make a difference. If it doesn't then I'll be getting a swirl pot.

 

I've also just bought and fitted some 'anti-surge' top cover gaskets for the DHLA's, anyone know anything about those? Described as 'for motorsport use', but can't find much info about them.

 

Reebmit - Do you run a return line from the swirl pot to the tank?

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Reebmit

Hi Rhys, yes I do run one, I retain tank injection pump which feeds swirl pot, out of swirl pot to Facet red top pump into regulator filter then to carbs. Run about 2.5-3.0 psi under load.. the return line comes from near top of swirl pot to tank... never had any fuelling issues since... obviously this suits me and others may have other solutions... each to their own... hope you sort out okay.... cheers

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