Stock fuel injector size?

[tornado34]

Are the stock OEM injectors on the 2012 260HO engine 48lbs injectors?

[NateRXP]

Yea and they love 153% DC @ 8580rpm

[tornado34]

I hit 100% at 7100 when stock with just an air intake upgrade!!

[Spanners]

How lean do your mixtures go from 7100-8500?

Can someone explain how more than 100% duty cycle is possible

[tornado34]

How lean do your mixtures go from 7100-8500?

Can someone explain how more than 100% duty cycle is possible

They don't, I run VT1100's which max out at WOT at 60%. Sweet.

[skidoochris]

when at 100%ds (when the injectors do not close) the cmd looses rpm
and the data log can get some strange info

I was trying to get 48lbs injectors to work on my 05
it did not take long for me to give up
even with a rrfpr I could not get the afr under control

[Spanners]

This was a question to open up a discussion - Ive been tuning race cars all over the world for a number of years, and have a fair idea on how things work you could say.

What I want explained, is how 42s with an X wheel as standard in a 255, can possibly run, when apparently 48s are at 100% @ 7100rpm on the same wheel.
Thus 42s being tapped at 6500...1500rpm to go and no additional fuel being supplied.. infact less as you go up in revs as you end up with more manifold pressure and rail differential pressure.
Dont try and palm off ignition timing as fuel requirements dont change up to 20% with a couple of degrees and the engines are identical mechanically.

If the above dutys can be believed, then mixtures head lean from that rpm point onwards.. BUT from the factory we dont see any of these engines having meltdowns.
Do you believe that Rotax with its racing history would fit injectors to 3 generations of tune that are well undersized?

When I do the maths based on inj sizing that Ive used for the last 15 years it tells me that a 215 has 25hp headroom, 255 10hp and a 260 around 30hp

[whittlebeast]

7100 rpm sounds low to hit 100% dc on 48s. Are you trying to tune with too low of fuel pressure. 8000-8100 would be more typical.

Andy

[NateRXP]

12.2 afr at 8580 rpm rising rate, stock 48's, feeding a hungry cam

[tornado34]

I've just pulled the log of the last ride I did before swapping to VT1100's.

My mistake.

I hit 100% @ 7810

90% @ 7485

60% @ 6846

All averaged from accelerating data.