Nat-Asp engines with extra injectors outside the ram-pipes
Turbo Mini Forums

I am curious....

In respect of these (nat asp) engines you occasionally see running two sets of injectors (one located near the head, the second usually at at the trumpet.

Time and again, these setups are proven to make more bananas when they bring in the second set and half the duration.

I am sure it is partly to do with fuel atomisation / improved mixing of the fuel with the charge air, and also in some way helping to further cool the charge - but surely this is turning into a wet manifold (although you are switching in the second injectors at higher RPM usually when there is plenty of airflow that doesn't promote fuel drop-out or puddling)?

Or is this second set of injectors (typically used on batch-fire systems rather than sequential if we are honest) bascially in some way spreading the fuel atomisation over the induction event, so the engine does have a greater "window of opportunity" for the fuel being pulled in at the point the inlet valve is open, rather than 180-degrees out...

I don't read CCC anymore, so this has probably been proven by some testing somewhere, but I'm just curious what the REAL reason is - and why some engines respond better than others.

My White 205 is running a setup like this, the second set are well away from the head off down the trumpets, staged to come in over 5000rpm and more than 75% throttle opening. When it was mapped the headline top end power didn't change much, but the torque did make a useful increase. As I understand it the benefits are down to improved atomisation and mixing of the incoming charge, how true this is I don't know, injection timing is something I have never really messed with.

Edited by Tom Fenton on 7th Sep, 2012.

I believe John Hastons K head sprint runs this configuration.

If something is worth doing, it's worth doing half of.

http://www.turbominis.co.uk/forums/index.php?p=vt&tid=373199

Sounds like as per Toms 205 you get a torque increase.

Edited by John on 7th Sep, 2012.

If something is worth doing, it's worth doing half of.