Jet size help

[Tom86951]

I am installing an hfs-4 system. I'd like help validating my jet selection. It's a 4 cylinder engine running 850cc injectors (one per cylinder) and I'll run up to 22psi boost. What jet(s) should I use? I decoded the graph chart in the materials that came with the unit, and the jets it suggest seem bigger than most people seem to be running.... Of course this motor does make a lot of power...

What type of fluid will you inject?

In rough terms, for 100% meth 25% = 850cc jetting

50/50 = 680cc of jetting

[Tom86951]

I'll start with water but then planning for 50/50. Based on the chart, would I be in the right ballpark with two jets one .7 and one .8?

[Tom86951]

I'll start with water but then planning for 50/50. Based on the chart, would I be in the right ballpark with two jets one .7 and one .8? And the largest restrictor....

For 100% water I'd run 1 jet, somewhere from .8mm to 1.0mm. After the move to 50/50 you can run more jetting.

[Tom86951]

I must be reading the chart wrong. Once I go to 50/50, would a .7 and .8 be too much still?

A .7 is only 300cc or so. for 50/50 we usually jet at 20% of injectors or:

850 x 4 x .20 = 680cc

[Tom86951]

Originally Posted by Howerton Engineering

A .7 is only 300cc or so. for 50/50 we usually jet at 20% of injectors or:

850 x 4 x .20 = 680cc

Ok, so 680cc means two .8 jets if I am reading the chart correctly. Is that right?

Yes. That is correct.