switching from 18 lb/hrs to 22.5 lb/hrs injectors- too much?

[alfa75ba]

Hi,

I used Bosch 0 280 150 702 injectors with flow rate 18 lb/hrs (189 cc/min) on my car ( FIAT 1.4 engine, 4 cyl. N/A) and had Idle PW of 2.1 ms (when cruising goes sometimes as low as 1.8 ms)

Now after mounting intake trumpets and mounting cold air box, set of injectors 0 280 150 152 which flow 22.5 lb/hrs (237 cc/min) low impendance (have original resistor pack) would be physically better match.

The calculation shows that for 18 lb injectors, Idle PW=2,08 ms (My datalog shows 2,1 ms) which is OK.
For injectors 22.5 lb calculated Idle PulseWidth=1,88 ms

Now that is pretty close to that recommended limit of 1.7 ms

Shall I go for it ? Can someone please share their experience with big injectors?

I use MSnS-extra 29q ,board V2.2

Regards, Drazen

[keithmac]

I`d have a go and see how well you can get it to idle, I went from 22lb to 42lb injectors on my 1.8 16v and the idle`s fine (2.2ms approx when hot, 14:1 afr).

If you`re prepared to spend 15 mins to tune the idle for the new injectors give it a go.

[alfa75ba]

Hi,
thanks for response.
Unfortunately, those injectors are not interchangable, they differ in shape, lenght and fuel rail shape ( the first are with o-rings, the second are barbed).
Since I had to do some fabrication to mount either set on my new ITBs I decided to go with my old injectors- they have been proven after all. Even they are quite big for this small engine, and 2.1 ms warm idle PW seems just about low enough.
Thanks, Drazen

[PSIG]

If the 237's are a bit big then turn your fuel pressure down a bit - no biggie at all.

[Big Creek]

Are you running more than one squirt? If so, turn the number of squirts down.

Todd