At what water to fuel ratio do you have to start worrying about hydrolock?

Interesting comment on rotor inertia -- I had never thought about that. I know that I have been concerned about how fast a water injection system could ramp up pressure if you go from no or low boost in mid-rpm conditions to WOT and a sudden spike in boost, which you would see on an autocross course all the time. I guess the rotor-less design of the Aquamist/Perrin pumps would help there.

 

I have received a video sometime ago from someone running a pump-speed progressive system, the water flow was captured on video. This might help you identify some issues rarely mentioned.

dead link removed

 

^^^^^
That link doesn't work. When it comes up there is a "..." in the url rather than the rest of the address. Please try again. Thx.

 

I have contacted the poster, hope he will reload it. It has been there nearly six months, may be photo-bucket took it off. If this is the case, it wil be lost forever.

 

I have found another video he posted, it is not as good but the car was on boost rather ramping up.

http://s8.photobucket.com/albums/a32...3092006011.flv

 

This is awful! I like to see his datalog of AFR!

 

This guy was complaining of unstable AFRs...

https://www.evolutionm.net/forums/sh...d.php?t=185062

 

slow car,

I am afraid there are hundred and hundreds of this type of "progressive pump speed" systems out there and no one seemed to notice this pitfall. The fluid flow always lags behind the boost.

The pump also takes time to decellerate when the throttle is snapped shut. It will continue to make pressure and inject fluid - an inline solenoid valve will
solve this problem, lowering the component cost plays a big part - much cheaper to put a loaded checkvalve than a good quality inline solenoid valve.

The link you gave above stated this problem very clearly. you just get what you paid, no short cuts.

 

The solution to the 'inconsistent' flow problem is to use some kind of feedback loop to tune the AFR. A signal from the alky system that 'fluid is actually flowing' (which doubles as a 'decent' saftey net [I'm well aware that it doesn't cover all situations]) combined with some closed loop feedback from a wideband works well for a cost effective setup. Or closed loop fueling based on a flow meter would work as well, but obviously a bit more costly.

From personal experience, a feedback signal from the pump pressure switch to the ECU eliminates 95% of the problem, which for is a 'good enough' solution for most.

 

Hey, bullfrg, I had to go through all this crap last year when I started doing SCCA autocrosses, since I set my car up for power before even getting into autocross. What I ended up doing was to just get another custom tune for race gas without the alky. When I go to the auto-x, I remove the fuse, show tech, toss in the race gas, and load my race gas map. I actually even crank my boost to the absolute max, since there is less load in 1st and 2nd, and I want all the wtq I can get, but I could have just as easily left my boost at the same exact setting and been tuned for that.

It's very simple, because my MBC has clicks that make it easy to set my boost at different levels, and it's very easy to load my separate maps. I also have 2 other maps - one for drag with race gas + alky, and one for road racing with a 91/110 mix + alky but more conservative.

 

After my BSP Evo was totaled in July, I raced my new SM Evo with alky at 6 events with no questions about my alky. I only found out it was illegal after finding some of your posts on here and the SCCA forum. I guess the race gas would be a nice solution, I would just need to find a local source.

 

how about on the stock ecu?

 

Yeah, I ran it in my first event only and was "informed" that it was illegal through indirect means. I won SM in that event, and I was brand new, so some of the other high finishers were coming over and asking me about my mods. I rattled them off, and mentioned alky injection like it was nothing special. My guess it one of them brought it up to someone else who got it to the chiefs who got it to the safety steward, and then I received an email from someone I'd never met. Got it all sorted out after that (painfully) and came up with an alternative solution.

 

That is what I am trying to avoid, need to get it figured out before the season starts along with getting a new clutch installed.