[s-cars] Re: Need more info on Water Injection

[Joe Pizzimenti]

Manny, comments inserted:


On Sat, 19 Mar 2005 14:25:38 -0500, manuel <manuelsanchez at starpower.net> wrote:
> S-Heads,
>  
> For frame of reference, this guy is a mechanic (although not Audi), has a 9
> second Honda that only runs 15 psi of boost. He's also an instructor at a
> local track.  Other than that I don't know him from Adam.

His Honda only runs 15psi because it probably has 11:1 compression.  A
stock AAN is 9.3:1 so you can get away with more boost without
detonation

> 
> 
> His comments were as follows;
> 
> 1. Your running way too much boost on pump gas, if you want my opinion
> you'd better reduce your boost on your tiny turbo. (I had actually
> instructed Mihnea to tune conservatively due to my concern regarding
> detonation (car previously had MTM 1+ that would ping on occasion))

No you're not, not for this motor.  22's right around the limit on US
premium pump gas.  A little water will help this.  (Note I said a
little)

> 2. Running that much boost is beyond the turbo's efficiency range (I
> actually have not seen the boost maps for the RS2, but had confidence in
> Mihnea's tuning)

22's not killing the turbo, by any means.  Haven't seen a compressor
map in a while, but I did run upwards of 26psi on my RS2 snail for a
while with no problems other than the occasional speeding ticket.

> 3. Water Injection is old technology (when I asked what  he had installed
> he said one of the early Aquamist Systems) and is a band aid for my use. In
> about a years time the new gel heatsink materials will reduce the costs of
> intercoolers.

So is the internal combustion engine and turbocharging.  Not
necessarily a bad thing, either.  Yes, it is a band aid for a good
intercooler, but it works well enough that most people don't need it.

> 4. I should save my money and put it toward a bigger intercooler (although
> he did offer up that using a small turbo to push thru a bigger intercooler
> would reduce the turbo's efficiency)

A properly set up water injection system will give you all the
benefits of a big intercooler without the pressure loss drawbacks. 
Granted, you need to make sure the pump is working and the reservoir
is full, but that's less opportunity cost, IMO, than hacking up a nice
German car's bumper to put a ricey intercooler in the front of it.

> 5. If you want more power you'll need a bigger turbo and bigger intercooler
> (obvious, but I didn't want to aggravate him, I just wanted to get his
> feedback on water injection)

Not necessarily.  If you mix methanol and water (or even run straight
methanol), you can make slightly more power with increased boost and
timing.

> 6. It will get expensive buying alcohol to add to a other than pur water
> mix.

This is true, but for everyday driving and typical s-car use, water is
just fine to get the benefits of detonation resistance from an
injection system.

> 7. Water Injection will lower the horsepower by about 30-40 horsepower.

If you overdo it, yes, it may.  You may bog the car down with too much
water and slow combustion down enough that the car is making less
horsepower.  You can do the same thing by putting 118 octane leaded
fuel in the gas tank, though.  It's all in choosing the size of the
nozzle and when you start spraying.  Bruce Mendel was running a 1.0mm
nozzle triggered at 10psi and that worked fine for him on full RS2
battle gear, 28psi and 93 octane on a big racetrack with a crazy
driver.

> 8. When I asked him what type of delta he saw in his intake temperatures
> when he ran his WI system, he said about 30-40 degree's (I am assuming
> thats in Farenheit, not Celsius since he's here in the US).  I believe he
> said from 170 down to 130 F.

He isn't running as much boost as you are, so you may see even better gains.

> 
> I am trying to decide between the FMIC option which I believe is ballpark
> 2k USD and 500-800 water injection. 

If you spend 800 on water injection, I have a bridge in the Brooklyn
area you should take a look at.  You don't need to spend half that to
get going.

 
> I plan on keeping my RS2 turbo because:
> a. I just got it
> b. Most driving is in town where I prefer the quicker spool up of a smaller
> turbo
> c. If I told my wife I was getting a bigger turbo she'd kill me (although I
> have properly instructed my 5 year old to respond this way to any question
> that has to do with any car problem; "Daddy needs a bigger turbo").

Good choice.  As former list benchracer Rod Haney once said, "The road
beyond RS2 yields heartache and a light wallet."

Pizzo