Nitrous Additional Fuel PW Calculations

[fj1289]

I've seen a couple methods for calculating a start point for the Additional Fuel PW's for the Nitrous System settings.

Matt Cramer posted this: http://www.msextra.com/forums/viewtopic ... it=nitrous

After doing a bit of reading on the internet, it seems the nitrous "community" tends to work mostly in PPH of nitrous and fuel and works around a range of nitrous/fuel ratios. Attached is a spreadsheet I came up with based on this info to help with setting up initial fuel settings.

[Z32 TT]

This is sooooo handy. Was racking my brain about this. Running dry pre turbo with e85 through 2200cc injectors.

Would you be able to provide an example calculation? Just to make sure I’m doing it right?

[fj1289]

First example from my motorcycle:

820 cc/min injectors
4 injectors (1 per cylinder)
100 HP nitrous jet
8:1 Nitrous to Fuel Ratio -- this is the big "adjustment" factor to your tune. This number will vary according to the type of nitrous injection (fogging an airbox, nitrous plate, individual injectors per cylinder, etc). LOWER number is RICHER.
N2O Min RPM 5500
N2O Max RPM 9500

The results are 3.405 added PW at N2O Min RPM, and 1.971 added PW at N2O RPM.

If I find I'm running an AFR about 10% RICHER than what I'm targeting, I'll multiply my Nitrous to Fuel Ratio number by 1.1 to get 8.8. (edited - corrected to RICHER)

Plug in 8.8 and get 3.095 added PW at N2O Min RPM and 1.792 added PW at N2O Max RPM.



For turbo applications (I HAVE NOT RUN NUTROUS ON A TURBO PERSONALLY) the effect of nitrous is greater than on a normally aspirated engine due to the cooling effect -- nearly double the "jetted" gain in some cases. You have two choices as to how to compensate - first would be to enter double the actual jetted HP for the nitrous as a starting point, OR second to lower the nitrous to fuel ratio number.

Also for E85 - you will need to adjust your nitrous to fuel ratio to a lower number (lower number = richer) as compared to gasoline - anywhere from 15% to 40% seems to be a guess at a starting point.

As an example, assuming
550 cc/min injectors
4 injectors
50 HP nitrous jet (actually using a 25 HP jet)
6:1 nitrous to fuel ratio (fairly conservative starting point considering the jetted HP adjustment)
Min N20 RPM 3000
Max N2O RPM 6000

Results are 6.205 added PW at N2O Min RPM and 3.102 added PW at N2O Max RPM.


Same setup, but keeping the jetted HP to actual and halving the nitrous to fuel ratio:
550 cc/min injectors
4 injectors
25 HP nitrous jet
3:1 nitrous to fuel ratio
Min N2O RPM 3000
Max N20 RPM 6000
Results are the same 6.205 added PW at N2O Min RPM and 3.102 added PW at N2O Max RPM.

Note - this does not take into account at all what your max duty cycle is available and whether this will exceed your injector capacity - still need to ensure the entire fuel system can handle the total fuel flow requirements for your setup (the reason for 820 cc/min injectors on the motorcycle!)

Also - you will need to log your results and adjust as needed!!