That's good data to see and ponder over. I wonder how close a reasonably sized air to water system could get to ambient?
Air to water wins on ever performance level because it's smaller and has a near zero pressure drop in the system. It also takes less time to spool up because there is less volume that you have to compress compared to an air to air system.
Below is a link to Borg Warner’s Matchbot page. VERY informative and interesting tool! Highly recommended. Along with Wes’s thread on choosing turbos and Corky Bell’s book “Maximum Boost”, I had a lot of my misunderstandings clarified.
Quoting from the MatchBot Intercooler efficiency estimator—
“Use 90-95% at low engine speeds with typical intercooler.
Use 85-90% at high engine speeds with typical intercooler (range depends on intercooler placement, size and quality.)
Use 100% if using air-to-water cooler (forces air outlet temp to be equal to ambient temp.)
Use over 100% if using ice water cooling for drag racing.
Set to 0% if not using an intercooler”
http://www.turbos.bwauto.com/aftermarket/matchbot
These estimates proved optimistic for the CAC on my ‘95 IH, as well as other posted readings I’ve seen. A consistent 100% for air-water especially seems unrealistic. Perhaps high 90’s for a well designed system??? Granted, the purpose of Matchbot is estimating, and they are going to have to generalize numbers...
What this DOES tell me is that an air-water system has more potential effectiveness.
MatchBot is an engine power estimator to help determine what turbo you need for your power goals. It gives a LOT of flexibility for user input parameters. For example- Volumetric Efficiency (VE). In his turbo thread Wes estimates our IDI’s at 85%VE iirc. This means the MatchBot default VE is also optimistic. Frankly I think everything MatchBot gives is optimistic. But if you know your yardstick is about 10% longer than a yard, you can still take reasonably accurate measurements.