View Single Post
  #3  
Old 08-07-2004, 03:51 PM
robbilau robbilau is offline
Member
 
Join Date: Feb 2004
Location: Los Angeles, California
Posts: 34
Default

OK folks, I have been testing and made some observations. Firstly, water injection does indeed do a good job of cooling - I am seeing on the order of 50C on a given day. However, the effect is not precisely what I thought it would be, so the effect leaves something to be desired.

Anyway, first some log graphs:

http://www.laurenson.com/users/robbi/wigraph.jpg
http://www.laurenson.com/users/robbi/wigraph2.jpg

The basic issue is that I assumed that the temperature change from water injection would be felt immediately at the throttle body and then disappear at the end of injection. Kinda stands to reason, don't it?

But the thermal behavior is far more laggy than I suspected. As can be seen from the first graph I can fairly successfully keep the general AT around where the turbo intake temp is, which is good for general driving. But if you take a look at the second graph you'll see why this doesn't really work under boost.

The thermal change is laggy - as we go into boost the AT starts to rise with the first pull but despite the fact I'm injecting about 25% of fuel in water the cooling effect is not restrained to the duration of injection but rather starts a general cooling trend which itself is laggy. This means that the AT increase continues as we change gear and get back on the throttle so by the time we're in full boost after the gearchange the AT is now higher.

This explains why my initial run into boost sees no detonation but subsequent ones do, because the heat is rising all the time.

What I was hoping to see was a sharp drop in AT dueing injection and a sharp rise as soon as injection stops. This would allow me to get fine control over AT under boost which would be perfect. The current situation may be fine for on-off spurts into boost but multiple runs into boost seem problematic due to the slow response.

Now it has occurred to me that the AT sensor might be slow - I have a call in to MoTeC about that. If not, it looks like a regular IC and a det jet is about the best option for intercooling.

Any suggestions?
__________________
Robbi Laurenson - System 2c
Reply With Quote