anyone have a near stock zr-1 with the secondaries removed? - ZR-1 Net Registry Forums

gmonsen · 07-30-2011

smmy... Please don't misunderstand me. When you increase the amount of air fuel running through the motor, you make more power. Since these cars still use proms rather than aftermarket EMS, your tuner has access to changing the basics of timing and fuel injector duty cycle. So what your friend did was to reset the injector duty cycles such that the air fuel ratio was adjusted upward -- for the added air flow -- back to wherever the motor likes it, but somewhere around 13-13.5:1, I would guess. That would make more power pretty much everywhere except the high end where the secondaries had come on before. The reason I suggested that the low end would suffer -- relatively -- is that there's a lot of air now down low and the secondary runners were not designed for velocity there, so there would be a lot of volume, but less velocity. The only way you could see this effect would be the shape of the torque curves before and after. However, it sounds as though the overall change is much for the better, though I would be curious to see the duty cycles for the injectors.

Just noodling about it, I wonder about keeping the primary-secondary setup and just have the secondaries come on earlier -- lower rpm or load -- rather than have them both open all the time, and increasing the size of the plenum, since the larger plenum would cause more air to go through both the primaries and secondaries.

However, running both all the time will certainly get you more power and its easy and doesn't cost anything, but the reasons for using variable valve timing go further than raw power or Honda would just run the upper end lobs all the time... And, despite the notes about passing various tests using "normal" versus power settings, that should not have been the primary reason for the design.

Gordon

07-30-2011	#20
gmonsen Join Date: Jul 2011 Location: Pennsylvania Posts: 64	Re: anyone have a near stock zr-1 with the secondaries removed? smmy... Please don't misunderstand me. When you increase the amount of air fuel running through the motor, you make more power. Since these cars still use proms rather than aftermarket EMS, your tuner has access to changing the basics of timing and fuel injector duty cycle. So what your friend did was to reset the injector duty cycles such that the air fuel ratio was adjusted upward -- for the added air flow -- back to wherever the motor likes it, but somewhere around 13-13.5:1, I would guess. That would make more power pretty much everywhere except the high end where the secondaries had come on before. The reason I suggested that the low end would suffer -- relatively -- is that there's a lot of air now down low and the secondary runners were not designed for velocity there, so there would be a lot of volume, but less velocity. The only way you could see this effect would be the shape of the torque curves before and after. However, it sounds as though the overall change is much for the better, though I would be curious to see the duty cycles for the injectors. Just noodling about it, I wonder about keeping the primary-secondary setup and just have the secondaries come on earlier -- lower rpm or load -- rather than have them both open all the time, and increasing the size of the plenum, since the larger plenum would cause more air to go through both the primaries and secondaries. However, running both all the time will certainly get you more power and its easy and doesn't cost anything, but the reasons for using variable valve timing go further than raw power or Honda would just run the upper end lobs all the time... And, despite the notes about passing various tests using "normal" versus power settings, that should not have been the primary reason for the design. Gordon