[DeTomaso] CR, Detonation, and water injection

[John Bentley (jab)]

Ken,
 
I think the bottom-line is race gas is cheaper and requires no
maintenance!  If you are running 11:1 or less CR,  race gas, normally
aspirated, aluminum heads and 38 degrees or less of timing advance, I
don't think you need to worry about detonation.  If you are running a
turbo or supercharger, you'll see reduced cylinder head temps with water
injection, but an intercooler is a better choice (IMHO).  
 
JB
 

________________________________

From: Ken Green [mailto:kenn_green at yahoo.com] 
Sent: Wednesday, October 03, 2007 10:22 AM
To: John Bentley (jab); detomaso at realbig.com
Subject: RE: [DeTomaso] CR, Detonation, and water injection


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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