I will have to say that those dyno's are only good to look at individually but not to compare side by side. Different dyno's is one like you mentioned, but ECU change and temperature difference are the biggest offenders for a VS comparison.
Yes the dyno does SAE adjustments for pressure and temperature, but the MAF and the ECU is to blame for the inconsistency. MAF works by cooling a wire, and the amount of voltage it takes to reheat that wire is what your airflow is determined to be. Colder day means for the same airflow your cooling the wire more, sure you have more oxygen per square inch but that only affects the AFR's. Different temperatures put you in different load columns (TP columns), thus for the same amount of airflow your now running more or less timing. You could tune your car our to run the same timing for both cold and hot day TP columns and have more consistency, but OEM ECU's don't do that.
Either way JWT S3 and S4's is a known 100% bolt on afair, they are also well respected for quality and power gains. Thus if you want something that will drop in and give you gains right away I would stick to JWT. If you want something that may require additional tinkering (cam gears, valve springs, etc.) then go with what ever you want. Another great and cheap option is the 91 intake cam, it's really hard to beat 8whp for $50, S4's will get you 14whp for $400, price per whp is no where near the 91 intake cam's.
Yes the dyno does SAE adjustments for pressure and temperature, but the MAF and the ECU is to blame for the inconsistency. MAF works by cooling a wire, and the amount of voltage it takes to reheat that wire is what your airflow is determined to be. Colder day means for the same airflow your cooling the wire more, sure you have more oxygen per square inch but that only affects the AFR's. Different temperatures put you in different load columns (TP columns), thus for the same amount of airflow your now running more or less timing. You could tune your car our to run the same timing for both cold and hot day TP columns and have more consistency, but OEM ECU's don't do that.
Either way JWT S3 and S4's is a known 100% bolt on afair, they are also well respected for quality and power gains. Thus if you want something that will drop in and give you gains right away I would stick to JWT. If you want something that may require additional tinkering (cam gears, valve springs, etc.) then go with what ever you want. Another great and cheap option is the 91 intake cam, it's really hard to beat 8whp for $50, S4's will get you 14whp for $400, price per whp is no where near the 91 intake cam's.
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