Alcohol Injection Instead of Bigger Intercooler

[BLASINTEBO]

For months I have been wanting to upgrade my stock intercooler but in the wake of recent rebuilding, that has been low end on my list of priorities.

Though, as far as performance goes, the cold air charge is among highest in making a lot of power with low boost... and from what peaple say, Upgrading the intercooler shows a huge bottle neck on throngs of stock II intercoolers out there mine included. But I love the way it fits so perfectly stock from the Skunkworks factory...

So I have been thinking about other ways to cool the charge withough doing drastic measures...

I have been thinking of a way to make a home brew alky or methanol injection tank, pressure switch and injector... does anyone have a good home brew using distilled water mix?

I'm not sure about which inkectors are suitable either so bear with me.

Does adding the water/alky lessen the bottleneck of my stock intercooler?

I wonder because soon I'm switching to 3 bar map, and soon boosting around 20 PSI on 91 octane pump gas, with my stock T3 garret turbo that came stock on the GLHS.

I want to make max power on my *near stock set up! But don't want to blow up my motor in the process.

[Frank]

Using Alky substitution is worth it, if you are willing to use it all the time. The intercooler plays a big part while in street conditions. You can't run alky all the time. Spring for a good intercooler.... will cost you closely to the same costs. If you are getting a calibration, then there is absolutely no need for alky injection because your fuel is good to go.



Frank

[Pat]

Alky will help you cool, but it won't change the fact that the stock IC's do not flow enough to make good power.

Pat

[Frank]

I havent really looked into it much, but the alky injection doesnt cool as much as we lead everyone to believe. Dont get me wrong... alky is very good because of the naturally high octane, the way it burns, and the fact that it doesnt cool some. Detonation is down overal because of it. However it doesnt cool until it gets hot enoughs from either being in the port and/or cylinder... unless you are running a really inefficent turbo like a mitsu. Of course I think that all changes when you start using it as your primary fuel... the evaporation of the alky (which cools the cylinder) is probably greater then say a 15-25% alky mixture that we would run. However I dont dare say anymore, because this is just my personal opinion which I have yet to prove.


Frank

[WLKIVETT]

The reason alky/ alky water injection resists knock better than gas is 2 fold.

Part 1 (I'm not going into heat gain due to proximity of combustion, or anything the combustion proself itself. This all happens before the combustion happens)

For 1 pound of air we will burn about 1.5 oz of gas. That is about 10.6:1 air fuel mix.

Air temp is 300 x 1 = 300 deg
Gas temp is 100 x (1/10.6) = 9.4 deg
Mixed air temp = 290.6

Same problem with alky

For 1 pound of air we will burn about 3.0 oz of alky as it takes about 2 times the fuel per HP. That is about 5.3:1 air fuel mix.

Air temp is 300 x 1 = 300deg
Alky temp is 100 x (1/5.3) = 18.75 deg
Mixed air temp = 281.25

When using water / alky of 25% mix with the same alky to air per HP ratio we get the following:
Air temp is 300 x 1 = 300deg
Alky/ water temp is 100 x (1/1.33) = 75
Mixed air temp is then 225 deg

Part 2 deals with the lower combustion temp of alky that reduces the combustion temps that helps prevent knock but is a little more complex than what could be discused hear.

Landon Kivett

[Frank]

I agree that the different mixtures can pull heat out of the air. However its not quite a simple as that... real world mixing is not uniform, so those numbers wont be as good. In addition, the energy transfered from the air into the fuel mixture wont always be enough to truely change the state of the alky and/or water from a suspended liquid mixture to a gasous state. This is where large reductions in air temperature occurs. Yes it happens some, but that is a small factor into the benifits of alky.

The big factor is what you stated in Part 2. The flame front in the combustion chamber is much cooler and in turn keeps the cylinder cooler. This allows for more timing with an intercooler, or to achieve the timing that you would run if you had an intercooler.


My point is that with an intercooler AND a planned future calibration, I would not recommend alky.


Frank

[Casper]

Landon,

From what I gather from your calculations the lower temps are simply because of the different characteristics of the various mixtures, correct? Or do those figures include any impact from evaporative cooling?

[Frank]

I interpretted as just a characteristic of the various mixtures. It has to do with adding mass of a different temperature.


Frank

[WLKIVETT]

Also the last calc. assumes you can get that much water / alky combination to burn. Highly unlikely it's on the verge of hydro lock. Almost 1 pound of liquid to 1 pound of air) it was provided as an extreme example of heat mass averaging.

landon

[BLASINTEBO]

I don't know if our car respond well to water injection, but my friend uses distilled-only water injection to let him run 20+ psi in his STI with red turbo (*he had a green one now he wants 400+ WHP) and he says it work very well. IF alky mix doesn't give me any more power or efficiency, at least for the sake of a safer high boost situation I'm am still thinking about it ( I have plenty of space for a tank by the wiper tank), that is, trying water only. That's why I want to know why kind of results TD guys have had using it and tuning it for our TDs.

[BLASINTEBO]

I just found this current thread on a guy using water...

http://www.turbododge.com/forums/sho...463#post750463

[Frank]

Alky/Water injection is better then just water. Its just that it becomes very inconvinent to run it all everytime you want to run just a little bit of boost over what you do now. This is why we have suggested an Intercooler.


Frank

[The S is Silent]

Quote:

Originally Posted by WLKIVETT Same problem with alky For 1 pound of air we will burn about 3.0 oz of alky as it takes about 2 times the fuel per HP. That is about 5.3:1 air fuel mix. Air temp is 300 x 1 = 300deg Alky temp is 100 x (1/5.3) = 18.75 deg Mixed air temp = 281.25

You can't simply average temperatures in this case. The inherent assumptions that you used while doing this are grossly wrong. You are assuming 2 things...1) No phase change, and 2) identical specific heats.

The whole premise behind injecting alcohol is that you are putting a liquid into a vapor to utelize the latent heat of vaporization...ie the energy associated with the phase change. The latent heat of vaporization of EtOH is MUCH greater than the specific heat of air. (838 kJ/kg vs 1 kJ/kg K) The calculation should be (using 1lb of air and 3 oz of EtOH like you did):

3 oz = 0.154 lb = 0.07 kg EtOH (using 789 kg/m^3 density, and some other conversion factors to get the units right. I'm going to use SI because those were the numbers I found in a google search)

0.07 kg * 838 kJ/kg = 58.66 kJ energy from vaporization

to calculate a final temperature, we use Q = m*Cp*dT, where Q is the heat transfered to the ethanol and Cp is the specific heat of air (above)

58.66 kJ = 0.454 kg*1 kJ/kg K*dT
dT = 129.2 K

300oF = 422 K, so the final temp would be 292ish K, or a little less than 70oF

This is assuming that all the alcohol vaporizes, which probably isn't the case. Also, this is just a kJ for kJ comparison. Eventually you would hit a limit to how low you can get the temp. The final charge temp would be higher than 70oF, but much lower than 281oF. I think the temp of your alcohol would limit this in some regard.

[beyond_audio]

http://www.rbracing-rsr.com/waterinjection.html

its a good read up on the basis behind the whole cooling and controlling detonation effect of water injection

[bfarroo]

Check the Water/Alcohol injection portion of the Engine management section. There is some good info there and people to answer your questions better along with many people who use it.

Benji