[DeTomaso] CR, Detonation, and water injection

[Ken Green]

JB,
   
      I was thinking about scenarios like Dennis running fast for 100 miles.  I don't like the idea of dropping compression or retarding timing to avoid high RPM detonation because both reduce power and efficiency.  It looks like the only other simple approach seems to be a rich mixture to cool the chamber, but that's wasting gas, and if that goes too far, may require carrying more gas for a 100 mile run.  Since water has about 4 times the heat of vaporization of gas, it seems a lot better to add a small water tank and water injection than add to fuel capacity.  I know Dennis is going to EFI, so there is a possibility that the ECU can be programmed to control the water injection (I need to read the instructions that came with the TEC3r I bought).  
   
      I know water injection has been used in aircraft for years (I didn't realize on jets? do jet engines experience something equivalent to detonation?), but seems to have struggled to gain acceptance in the auto world.  I suppose the aircraft systems may be a lot more complex and expensive?  I assume water injection works a lot better in turbocharged applications where the issue is that the air has been greatly heated?
   
  Ken

"John Bentley (jab)" <jab at cisco.com> wrote:
  All you need is a separate injection system for the water (like on a
dc-8)! :)

JB



-----Original Message-----
From: detomaso-bounces at realbig.com [mailto:detomaso-bounces at realbig.com]
On Behalf Of Ken Green
Sent: Wednesday, October 03, 2007 9:06 AM
To: detomaso at realbig.com
Subject: [DeTomaso] CR, Detonation, and water injection

It seems to be common practice to use a rich mixture to cool the
combustion chamber under high HP output conditions. I looked up the
heat of vaporization of gasoline, and it's 135 calories per gram
compared to 540 for water. This would suggest that you need a lot less
water than extra gas to cool the chamber and it makes a lot of sense to
use water injection to control detonation versus rich mixture. The math
seems pretty simple. 

Ken
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