Fuel Economy

[JonW]

Hiya,

I'm running a Falcon .21 engine and would like to increase my runtime.

Currently it is running very well and can last around 7mins, however I'd really like to last 10mins so I only need to pit once in the finals.

Can someone recommend a good pipe/manifold comb to use? Or should I try something else?

I am running 25% Byron Gen2 fuel with a HN 2027 pipe

Cheers,
JonW

[MR Piraterc]

what carb venturi are you running ?

[JonW]

I knew someone would ask that
Its the standard one, i'll try and find out...

cheers,
JonW

[MR Piraterc]

As it happens now im home from work and just by the off chance have a brand new Falcon .21 on my desk i have had a look and its a 7mm venturi 

[JonW]

Thanks MrPirate

It's actually a really nice motor too.

cheers
JonW

[MR Piraterc]

The 7mm venturi will give better run times better fuel economy opposed to the 8mm venturi which gives you more power and less fuel economy. Around DRT its a high horsepower track as its got 3 straights where people tend to open up and this will cause you to battle to do 10 min runs. yes there is certain engines capable of achieving this but if you have a hevy love for the gass like me driving very much on power its rather hard to achieve. I timmed the GRP .28 to 11.5 mins but still play chicken and come in around the 5 min mark as not to have a fuel stop too late in the heat 

[JonW]

I read that if you use too small a venturi on a fast track you will need to keep on the throttle longer to get speed. This in turn would make it less in fuel economy than a larger one. One more thing to think about I guess.

JonW

[Bren]

Achieving longer run times has many governing factors.

fuel generally 25% gives a longer run time over 30%
Venturi the smaller the hole the better the economy but going to small will reduce power or engine grunt, it will also struggle on long straights.
Another way is to limit throttle throw on the servo to 1/2 or 3/4 this so carb is limited, then tune engine to that. This is an art & very hard but will give better economy.

The biggest difference though is on track design or grip & how much power you use to get around track.

For example Neo this year i was getting 13 minute run times the following week 9 minutes, it was all down to track design as i had not altered engine tune.

to be honest 7 1/2 minutes is a point most engines achieve easily & leaning it out to get better will shorten its life.

[JonW]

Thanks for the reply Bren.

Do pipe & manifold combinations make much difference to fuel economy?

cheers,
JonW