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Old 12-17-2009, 04:29 PM   #57
Former Vendor
Member#: 160427
Join Date: Sep 2007

You can go either way there. We usually go pre-blower for two major reasons:

1) This allows you to cool the blower case and the air charge, which does a lot for under-hood temps. In many cases it actually gets a bit more boost from the blower as well. I had one customer with a Jag that claim he picked up 4 psig that way. The blower in that case was being drastically overspun (And Eaton making 20-24 psig on a 4L V8).

2) It is much easier from an installation standpoint as well in many cases, as there is no need to remove the blower etc.

We do NOT recomend injection pre-compressor on turbos or even centrifugal blowers, as they are a completely different system with much higher velocities involved and of course the thin compressor blades. If you look around online you can find pictures of the damage from over-injection pre-compressor with a high RPM turbo. On many of these applications you have the tips of the compressor blades moving at 900+ MPH. IF you then start hitting that leading edge with a droplet of liquid (even partially evaporated) you can cause issues.

The thing about spraying pre-blower on a positive displacement unit (like a Whipple, Eaton, KB, etc) is that these blowers do make a lot of heat relative to a properly sized turbo. So the injection volume is often much higher. An employee here had an '04 Mustang Cobra that we did a lot of work with. That car was fairly stock, at this altatude probably only in the range of 500HP and a bit more than stock boost. Yet it would handle a 625 nozzle just fine. A 375 probably would have been more appropriate had it been a centrifugal car at the same overall power and boost levels.
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