Dudemaaanownsanrx7

iTrader: (23)

From my experience water doesn't drastically change or reduce air temps. But it does seem to keep them from sky rocketing. I'm running a relatively small ebay intercooler 12X24 X3 IIRC and even on a long 1st through 4th 23 psi pull my air temps stay about the same through out the pull.

I think when air temps start exceeding the mid 200* F level that water will pull a lot of heat out of the intake charge. The advantage of that is clear in a Water only injected car, but in a car injecting methanol as well I see at least one advantage of reducing the amount of methanol required to pull temps down.

Pre-turbo also has the advantage of becoming extremely well atomized after colliding with the compressor wheel, this makes it easier to ignite the mixture, and from others experience has allowed lower water injected requirements. For what reason I'm not sure.

BDC

If an air temp gets that high, then there's already been a serious problem if one is running a pump fuel. I've seen IAT's on a hot dyno get close to 200*F on a race gas setup and it was still fine even though vastly less efficient than it could be if it were 100* colder. On a pump gas car, I don't like anything 140*F and above. It's begging for pre-ignition knock.

I still honestly would like to see some more data on this. I've heard the talk but haven't seen anything demonstrated that would show definitively why it's more preferable than post-turbo. Rx72c? Got anything to add about this? Is pre-turbo done because of siphon-style water injection or is there truly a benefit besides theoretically making the compressor more efficient?

If it's strictly for chopping the air up to better atomize it then that has merit even though I think the external air atomizing nozzle you've run across should do the job.

B

WaachBack

iTrader: (21)

Ill chim in since I have used water for a while now.

When I used to run non seq stock twins at 18psi, my air temp used to be around 55c. I added 315ccs of post turbo water and it dropped to about 45c.

On my current setup (GT35/74) which I have tuned for 23psi on 92 pump with 11 a/f, I had about 50c IAT readings. With the addition of 550c water post turbo, it dropped down to around 40c.

Keep in mind also, I am in Hawaii and ambient is on the hot and humid side.

Like mentioned, yes water will cool down the intake charge a bit, but not close to meth, BUT it will serve as a great chamber coolant and nothing can beat it at that. I have high teens to low 20s knock. I think thats more then enough proof of how awesome water is.

Dudemaaanownsanrx7

iTrader: (23)

Well the external atomizing nozzle is designed for low pressure systems. If it's being run mechanical, driven by the turbocharger it has to be preturbo. Otherwise the pressure would equalize and no water will flow.

As far as the high air temps, i was refering to turbo outlet temps which can be in the 250-300 degree range before any chemical or physical intercooling. I would never allow temps that high in the engine. By cooling the 250-300 degree temps down to 200 with water, it will require less alcohol to cool them to 56 or whatever.

BDC

That's significant.

I believe it. That's what I am betting on. I'm curious to see before and after EGT's!

B

BDC

Personally, I like the low-pressure setup. It's simplicity is it's genius. Good job on it, Brent. I'll probably duplicate it even though I'll dress it up some as well as and add a couple of other pieces to it (low-level tank sensor, turn-on and low-level LED's, check-valve and filter, and locate the nozzle pre-throttle).

Ok, makes sense. I misread you, then. The discharge temps on my T70 at 25psi are 296*F. The alcohol volume I sprayed in (about ~1500-1600cc/min or so) took 200* of heat out!

B

84stock

iTrader: (5)

You say alcohol, don't you mean methanol??

BDC

In my case, yep. Methyl alcohol.

B

84stock

iTrader: (5)

Ditto, very effective in my lower intake under my camden for me, been using it for a couple years now.

Dudemaaanownsanrx7

iTrader: (23)

How do you plan on installing the nozzle pre-throttle body? Unless you're running a water pump you won't get any water in the engine with a low pressure system. The low pressure system is run by boost pressure. If 25 psi pressurizes the tank then your pre TB pressure will also be 25 psi, the two pressures will fight each against other (equalize) and you will have zero water going into your engine. You MUST run preturbo, OR install a pump. Won't work otherwise.

Yeah, I'm saying in your case preturbo water could easily pull about 80* F out, leaving 120*F for the alcohol to pull out = less required alcohol. Maybe instead of 1600cc meth, you could use 800cc and have the same drop in air temps. Just a thought. In practice it could turn out differently.

BDC

Doh! You're right. I didn't think about that.

Well, even if I do pre-turbo, I'm still sticking with the larger amount of methanol. I'm using it to run big boost on a big turbo... well, trying to.

B

BDC

Alright. Screw it. It'll be pre-turbo, then.

B

Dudemaaanownsanrx7

iTrader: (23)

Lol welcome to the club. Anxious to see the results. Honestly the water depending on injected amount is enough to run big boost on a big turbo. The meth sure won't hurt though, and without the intercooler It's probably required, I don't think the water will cool the intake temps enough without an intercooler. I like to stay under 120*F personally.

SirCygnus

iTrader: (1)

look at bdc, becoming a man and growing hair on his chest.

BDC

I would hope so, by now. I'm 37 years old.

B

BDC

Some more numbers for the data geeks out there.
http://www.engineeringtoolbox.com/fl...eat-d_147.html
http://www.journeytoforever.org/biof...manual1-2.html

Heating Value (BTU/LB)

~Gasoline 19000-20250
Octane 19080-20570
Methyl Alcohol 8640-9770
Ethyl Alcohol 11550-12780

Latent Heat of Vaporization (BTU/LB)

~Gasoline 127-140
Octane 128-141
Methyl Alcohol 473-474
Ethyl Alcohol 361-364
Water 970

300cc/min is 0.6615lbs. 300cc/min of gasoline used as a chamber coolant will extract just over 92BTUs. That's assuming the higher figure of 140btu per pound.

300cc/min of water injection, however, replacing that gasoline, will extract over 640BTUs, which is over 7 times better, still assuming the best gasoline. Using the 127BTU/LB figure, it's over 7.5 times better.

500cc/min will yank about 1070BTUs out.

The equivalent cooling BTUs for methyl alcohol, volume for volume compared to water, are right at half.

B

BDC

To answer my own question:

472cc/min of gasoline (what the difference is between race gas and pump gasolines for this example I am unaware of) would be 1.04lbs. Using the higher 140BTU/LB cooling figure for gasoline, this comes out to be about 145BTUs. If he were to take the setup, remove that 11.1% in boost to aim for a 12:1 AFR and replace it with 472cc/min of water, he'd be replacing that 145BTUs with a hair over 1000BTUs.

Yeowzer.

B

rdahm

iTrader: (6)

lol i read that quickly and it sounded like it was a bad situation. I had to read it word for word to understand the reason for the yeowzer.

:-)

Thats pretty compelling in that situation

BDC

Seems to be that roughly 100cc/min of WI is required per 100hp when replacing 10% of the overall fuel duty with that water.

B

BDC

800cc/min = 1.76lbs gasoline
1600cc/min = 3.52lbs methyl alcohol

246.4 BTUs cooling on the 800cc/min gasoline I yanked. 1668 BTUs cooling with the 1600cc/min of methyl alcohol I put back in the gasoline's place to achieve the target air/fuel ratio. A 30% change out of gasoline with alcohol at 25psi of boost on my setup yielded 6.77 times more chamber cooling. That same degree of cooling is achieved by just over 700cc/min of water injection.

These figures correct? Or, am I mistaken in alcohol's mode of cooling as most of it, if not all, has already flashed into a gas in the hot-air pipe, bringing IAT's down?

B

Dudemaaanownsanrx7

iTrader: (23)

That is a good question. That maybe the alcohol having already dropped IAT's by 200*F, that it did very little cooling once inside the engine. That could explain why the engine knocked and died despite having a large % of methanol being injected.

BDC

Possibly. But even still, the alcohol produces a colder end gas during combustion than gasoline. /shaking head

I'm still trying the pre-turbo WI, though.

B

prjct87rx7

iTrader: (7)

I was tossing this around in my head also. pre- or post turbo. i keep reading about the pre and i think im going that route also.

what cc nozzel should i get running 15-18psi on pump gas with 550 primaries and 1680 secondaries and a to4r

Sandro

iTrader: (1)

xzl6b1 thought of using the air pump for the atomizing nozzles. Sounds to me like a good idea to possibly send more air and achieve better atomization...

https://www.rx7club.com/showpost.php...7&postcount=37

BDC

The more I look at Brent's idea the more I really like it. Even though it's got a low-pressure back end to it (it's pneumatic; works off of manifold pressure), using the correct air atomizing nozzle it should and will still work just fine. It's simple, there's very little in the way of electronics (what, a pressure switch, a solenoid, and a couple LED's potentially?), and there's no worry of pump failures. Given the requirements of water injection being low on the actual injection volume end, this setup makes perfect sense. Not to invalidate your idea Sandro, but I think you should look into this one a bit more closely if you haven't.

B