Howard Coleman

iTrader: (6)

as many of you know there are at least 2 hp calculators readily available to rotary owners... max cooper and rx7.com ari yellen's site.

both ask you to enter your injector sizing and injector duty cycle and will calculate your rwhp.

i have fiddled with this a bit and corrected my afrs to my target (they weren't far off) and also corrected the hp for SAE std temp/pressure/humidity.

most of my calculated hp readings seem to be about right except for the 2000 to 3000 rpm area where they are high compared to most other rotary results.

for instance, running 850 and 1600s i get:

2000 rpm 17.9 inj duty cycle
2400 27.1
2800 36.7
3200 37.7
3600 44.5
6800 74.6 at 10.1 psi

boost turns pos at 2800

as i mentioned, the lower rpm numbers may be off. i am wondering if anyone has any answers and how close the hp calculators are to the real thing.

thanks,

howard coleman

maxcooper

Could it be related to the sequential injector control?

At low RPM, only the primary injectors are being fired, so the duty cycle should be higher than you would expect if all the injectors were firing. At some variable RPM, it switches to firing both sets of injectors (pri and sec) at the same time. The switch-over RPM is variable because I think it is based on inj duty cycle rather than RPM. On the stock system, it seems to switch over at any positive boost pressure or about 4000 RPM if you stay in the vacuum side of the gauge.

-Max

Howard Coleman

iTrader: (6)

that concept crossed my mind. the problem is that the injector duty cycle (IDC) has a nice smooth curve to it. it would seem if the IDC related, say, to the primaries until the secondaries kicked in you would have a bump down... which i don't have.
do you have a log that you could check?

howard coleman

maxcooper

The secondaries get phased in, but I still recall seeing the IDC drop I think. I'll try to find a log (or make another one) and check it out.

-Max

maxcooper

Here's another thought: where are you getting the IDC numbers from? Perhaps there is some funny math going on to provide a single number. The Datalogit logs both primary and secondary IDC separately (even though they might be different between rotors if you set the injector sizes to be different).

-Max

books

iTrader: (8)

Howard,

In the Optimum EGT thread I placed a text file of a dyno run. It included injector duty cycles from around 1,9xx rpms and up. This was on stock twins, 550s and 1300s running about 15psi. I believe injector transition is around 40%. I also have an excel spreadsheet that includes horsepower numbers with that log.