The cooler the air before compressor will yield more hp than after compressor.

 

WAY too much tested and confirmed results proving quite the opposite.
Both Rodney @ AIS and Steve @ Steve Morris Engines (ProCharger GURU) highly recommend it for centrifugals.
Plenty of track tested results from guys running both pumpless and pump set-ups as well.
(see link in post #43)

Not saying that the power increase will be huge...but consistency should increase significantly vs having a heat soaked compressor.

 

Air gets hot from compression and friction not necessarily heat transfer from the housing. Not saying decreasing iats preblower dont help but if your adding something that provides evaporation precompressor vs post compressor you will yeild a greater % change the closer you can get it to the combustion chamber.

I think time and money better spent on proper cooler size/placement and fueling/tuning will net a better result. Plus if this was such a game changer then everybody would be doing it.

 

Also from link: "As already mentioned, positioning the water methanol injection nozzles or nozzles just before the throttle body or carburetor on turbocharged and centrifugal supercharger applications is by far the most common position and one of the most beneficial of all as it offer excellent air charge cooling and exceptionable detonation control and cylinder cooling. "

 

Pre-compressor injection helps cool the output, period. Personally I would never consider "in lieu of" pre-TB injection but I'm certain the application being discussed is for adding incremental cooling/efficiency which will increase power via lower IAT's.

I've seen many posts over the years debating or disputing gains on FI setups with FAST vs LS6 intakes, SC inlet tubes with increased diameters and low restriction air filters, pre-compressor alky injection, etc.. The results are usually minimal (10-20hp) but are legit and measurable. They have all been proven to be incrementally effective so if you are a mechanic/tuner that wants to leave no stone unturned I've always found them to be rewarding. Added together or by themselves they could be the difference to help you achieve a goal whether that be a race win, a lower ET or just a dyno number. Just my $0.02 of real world experiments....the science of hauling ***.