RealStreet

iTrader: (1)

I'm not here to tell you what your cars do and don't do. I'm just helping people understand the sizing of the two units. I don't know what is done to your two cars aside from compression ratio, fuel, turbocharger and the same cams. (And I don't know which turbo had which fuel running through it)

Ethanol is going to spool a turbo quicker, easy enough. Ball Bearing (I don't know if your 6262 was or not) is worth 3-400rpm in most cases I have seen. I don't know the turbine housing on your T04Z, I don't know the turbine housing on your 6262. But every one of those things is worth a couple hundred RPM. You could have a .61 A/R T04Z with ethanol and 11:1 compression and a .96 A/R Journal Bearing 6262 with gasoline and 9:1...you've got yourself a scenario where the bigger turbo is going to come up as quickly or even quicker.

36psi to 36psi also depends on a bunch of things. If you have the same exhaust pressure in the system, yes it will be similar, but if one is higher than the other, boost will increase quicker due to it stacking exhaust gas in the cylinder effectively reducing dynamic compression ratio and hurting power. There are tons of factors that come into it. Now obviously based on your signature you know this, but I'm trying to help other people understand the dynamics of the system. If the T04Z was the high compression ethanol car, this would all make sense, as the mass flow through the turbine would be higher but the larger turbine wheel would be able to cope with the flow delta, which - as you said would yield a similar power output due to the 62's fantastic compressor wheel. (Or is the 6262 the ethanol car?)

All that I'm saying is one dyno graph is not the alpha and omega of turbocharger selection - not that you were implying it was, but a lot of people reading on the forum wont know what to look for or what questions to ask.

JohnBradley

iTrader: (30)

Very good point, there is a lot that contributes that I cant account for 100%. I know what you mean though about data looking absolute. This reminds me of an old saying about absolutes