Some of you would have read of my negative dyno experience after switching to a Evo Highflow intake. I've talked to several people locally to find out the reason. Finally, I got to speak to a rather prominant local racer/tuner today and what he said started to make a whole lot of sense. I don't think it's totally new as I believed I've read it somewhere before. Anyway, here goes :
- In all combustion engine, cylinders fire in sequence
- Hence, air is drawn into the cylinder in 'pulses' (Intake) and waste gases expelled in 'pulses' (exhaust) as well
- The piping length and diameter for the intake are designed with this intake flow in mind. Apparently, a longer intake route will result in higher torque at lower rpm. That's why some top end cars uses variable length intake routes
- Because air is drawn in 'pulses', the resonance chamber along the stock intake piping acts as a 'reserve' air tank to ensure sufficient intake air volume during peak 'pulses'
- Hence, rather than causing obstruction, the resonance chamber actually assist in boosting torque along the low/mid range
What do you guys think? I recalled reading a few posts where the major tuners from Europe (Techart, Gemballa, etc) does not replace the stock airbox or piping but just the filter element. I guess the stock piping along with its resonance chamber and heat shielding are very effective as it is.
So the big question is whether an ECU retune will resolve this issue ie. higher bhp/torque throughout rpm range with EVO intake kit (in my case) with ECU retune compared to stock intake with ECU retune.
I guess there's no concrete way to find out except to do another series of before/after dyno runs
My intention now is to get a GIAC program for BOTH the EVO Highflow and stock intake kit. And then do dyno runs to compare... I wonder if GIAC will sell them both to me for US$1k or do I need to pay US$1k for each program. GIAC has a Flashloader that I can use to switch in between programs. This will certainly save me the hassle to send my ECU back for re-programming each time I wanna change it.
Having said all the above, it doesn't mean the exhaust manifold are very efficient on our cars. These are not equal length manifold and are manufactured with cost in mind. They also do not have a central merge collector where the manifold piping meets. As exhaust gases are expelled in 'pulses', there is a scavenging effect. Meaning for example, as the exhaust gas travel out of cylinder 1, the gases from cylinder 2 (assuming it's the next cylinder to fire) will just be ready to exit. The 'momentum' created by the gas from cylinder 1 will help 'pull' the gas from cylinder 2. Hope someone understands me here. So I think replacing the exhaust manifold and cats on our cars will definitely yield positive results across the rpm range, as shown in my previous dyno reports.
Ok, somebody say something
