# Can injecting too much "fluid" increase knock?



## Fast VW (Sep 24, 2002)

I am just trying to tune my water injection and I was wondering if increasing the amount of fluid too much can cause more knock sensor activity. I know when you reach a certain amount you get quench, power loss and missfires, but what about before that occurs.
Thanks.


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## greggearhead (Jul 28, 2002)

*Re: Can injecting too much "fluid" increase knock? (Fast VW)*

Nope - won't 'cause' knock. Just like if you went from 91 octane to 116 octane - it won't knock easier.


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## greggearhead (Jul 28, 2002)

*Re: Can injecting too much "fluid" increase knock? (Fast VW)*

Say - have you dynoed your setup? Pretty interested to see your results. What kind of fuel mileage do you get?


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## Fast VW (Sep 24, 2002)

*Re: Can injecting too much "fluid" increase knock? (greggearhead)*

I am not sure were a dyno is within driving distance but I am not done tuning it either. I just added the #30 injectors and C2 chip but I am having a problem with too much timing pull. I switch from the 100ml/min nozzle to the 175ml/min nozzle and it improved it but still too much timing pull. I may have to get the chip reflashed with less timing advance.








If I drive without putting my foot in it, I can get aound 32mpg on the highway.
One thing I can tell you for sure is that it has a very strong powerband from 3000 - 5500 rpms. 
Are you who I think you are? Did Derek just foward some of my VagCom logs to you?


_Modified by Fast VW at 11:00 PM 10-6-2008_


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## theAntiRiced (May 7, 2005)

*FV-QR*

Water doesn't compress, so you are technically increasing your CR. However, likely before your CR overtakes the benefits from the injection you'll hydrolock.


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## greggearhead (Jul 28, 2002)

*Re: FV-QR (theAntiRiced)*


_Quote, originally posted by *theAntiRiced* »_Water doesn't compress, so you are technically increasing your CR. However, likely before your CR overtakes the benefits from the injection you'll hydrolock.

Gasoline doesn't compress either - so why don't engines hydrolock on gasoline? Water-methanol injection only injects a percentage of the gasoline going into the chamber, so there is no chance of hydro lock in a normal setup. 
Think about it this way - pull a plug wire. Run your engine. Didn't hydrolock, did it? 
Now, realize with the heat of combustion, water converts to steam, which pushes down on the piston, just like gasoline burning and making heat to increase pressure. 
Now, also realize that the only thing that determines a static compression ratio is the metal of your piston, combustion chamber. Dynamic compression is a product of a million different things.


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## Fast VW (Sep 24, 2002)

*Re: FV-QR (greggearhead)*

The only reason I asked the original question was because I read on a water injection manufacture's website, in their forums, that it could increase knock if too mch water/meth was injected. I will not say which manufacture it was but I will tell you it was NOT Snow Performance. This information was actually posted by a forum moderator.
It didn't make sense to me so I though I would ask here.


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## Budsdubbin (Jul 14, 2008)

*Re: FV-QR (Fast VW)*

Water/meth doesn't exactly create knock if theres too much. You Simply have a extremly rich a/f ratio which means that you have too much fuel per o2 in the cylinder and you misfire. I donno if you have the 2.0 or a vr6 but is your controller running off the maf or vacuum/boost. 


_Modified by Budsdubbin at 6:05 AM 10-14-2008_


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