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Old 04-19-2007, 03:34 AM   #1
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Default How good is WI for lowering intake temps?

Got a thermocouple hooked up to my intake after my rx7 t2 intercooler. Seems to heat soak at about 50F above ambient temps when I'm driving aggressive. So on a 90F day I would be running 140-150F intake temps (the intercooler is too small for 11psi). Would just running straight distilled water lower my intake temps alot or would I lose some power caused by not taking advantage of retarding my timing too. I may not start retarding my timing until I can build a safe guard system like mentioned in another post.
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Old 04-19-2007, 04:02 AM   #2
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You will see ambient temps very quickly. I would feed in at least a degree or two of timing to give your self a little taste of the gains to come.
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Old 04-19-2007, 06:07 AM   #3
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Is there an "ideal" target intake temp- ?
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Old 04-19-2007, 08:36 AM   #4
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Well obviously ambient would be the best.....unless WI is capable of lowering past that!? I guess a couple of distilled ice cubes in the tank might bring the temps down. I'm just looking for better effeciency over my rx7 intercooler. The cost of WI is far cheaper than going with a completely new intercooler setup.
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Old 04-19-2007, 09:04 AM   #5
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Quote:
Originally Posted by MiataNuTca View Post
Well obviously ambient would be the best.....unless WI is capable of lowering past that!? I guess a couple of distilled ice cubes in the tank might bring the temps down. I'm just looking for better effeciency over my rx7 intercooler. The cost of WI is far cheaper than going with a completely new intercooler setup.
Ambient could be 40degC in the desert- could be -2degC!

My question is - is there an "optimum" temp?
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Old 04-19-2007, 09:12 AM   #6
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Probably get flamed here but what the hell

I think you've got things **** about face Mate, surely the object is a more reliable and consistent power no?

If you want cooler intake temps by far the best solution is to just bang on a bigger IC.

Surely WI will only drop your pre combustion temps up to a point, once your blow 100c then the waters no longer going to evaporate, no evaporation no cooling effect.

The way i see it is WI is by far more useful in the cylinder, as temp's here are over 1000c evaporation is a given, this in turn cools inside the cylinder reducing those hot spots that can often cause knock.

For me personally i've found that with WI i have been able to advance my timing 6 degrees over peak torque.
To my mind that's really the major benefit of WI, not reducing intake temps.



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Old 04-19-2007, 09:14 AM   #7
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Quote:
Originally Posted by rockdoc View Post
Ambient could be 40degC in the desert- could be -2degC!

My question is - is there an "optimum" temp?
The lower the temp the more dense the air.

The denser the air the more you can fit in your combustion chamber.

There must be a point of no return, but i'd say within the realms of 99% of drivers the colder the better mate.
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Old 04-19-2007, 09:18 AM   #8
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actualy i wsa seeing cooling of below ambient but i ran methanol as well the water is being disperesed from high pressure system so naturally it will saok up the haet of the intake very effectivly it doesnt have to change state to absorb heat energy just look at any hot water heater, or pot of water on the stove to see that the real issue is keeping the water suspended in the air mass so that puddeling does not occur. You my freind have it all wrong WI is not a bandaid IC's are. they introduce way to much volume into the intake equation in order to give the haet time to dissapate over a larger surface area driven by the prevailing winds. WI soaks up the heat and adds mass to the exhaust aiding spool and is the only way to do things. Provided you are in + C weather and or the tank does not freeze.
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Old 04-19-2007, 09:36 AM   #9
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what about injecting pre intercooler?- (post supercharger)
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Old 04-19-2007, 09:52 AM   #10
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I tried a water/Methanol mix, but found i had to retard the timing around 2 degrees, so from my limited tests it seems as though a water/meth mix is not as good a knock suppressor as water alone.

I'm not knocking WI mate, hell i've clawed back 6 degrees of timing, i love it

What i'm saying is that from what i've seen and read WI is not really the best device to use if you want to lower your pre combustion temps.

Someone a damn sight smarter than me showed me the calculations on the amount of heat water can physically take out of air, i'll see if i can dig em out.

From what i remember though WI gave a maximum theoretical heat reduction of no more than 40c.



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Old 04-19-2007, 12:47 PM   #11
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that 40 C number is fully dependant on the amount of water injected. I know the formulas you speak of. FWIW i run about 20-25% or so by volume vs most people at 15% or so. This might make abit of difference i dunno. some figures
Consider the following liquids and their heats of vaporizations.

Water 40.655 KJ / mole or about 2259 KJ/Kg water
Methanol 35.2 KJ /Mole or about 1102 KJ/Kg Methanol
Pentane 25.77 KJ/mole or about 357 KJ/Kg Pentane
Octane 38.8 KJ/mole or about 339 KJ/Kg Gasoline.

Last edited by magnamx-5; 04-19-2007 at 12:57 PM.
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Old 04-19-2007, 12:57 PM   #12
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Those equations are usually based on perfect conditions not in an environment that is being artificially biased with heat and pressure. Just like eunos said, the real benefit of WI is the cooling inside the combustion chambers. That is where the true magic happens. The temp sensor just ends up saturated because of the liquid, so that is not a very good indicator.
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Old 04-19-2007, 01:00 PM   #13
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http://forum.miata.net/vb/member.php?u=23048 from a discousion on the pointy baord
Quote:
Originally Posted by FormerDatsun510Man
Interesting Corky, then based on what you have said I know my calculations aren't far off. Here is the longhand.

Taking for example a Coldside MP62 running a 105/65 pulley at 7000rpm:

cfm = CID(blower) * VE * RPM(blower) / 12^3
cfm = 62 * 75% * (7000*105/65) / 12^3
cfm = 395.6
m^3/min = 395.6 * .3048^3
m^3/min = 11.2
airflow gram/min = 11.2 * airdensity
airflow gram/min = 11.2 * 1200g/m^3
airflow gram/min = 13441.7

For a 12:1 a/f ratio this would mean we would inject a total of 13441.7/12 grams of fuel per min.

fuelflow gram/min = 13441.7/12
fuelflow gram/min = 1120.1

It takes 1 Joule to raise the temp of 1 gram of air 1 deg C. Likewise, removing 1 Joule of energy from 1 gram of air reduces its temperature 1 deg C. So for our massflow of the air above there is a total of 13441.7 Joules of heat energy needed to be removed per minute to lower the temperature 1 deg C.

The latent heat capacity of gasoline is 349 Joules/gram, meaning 1 gram of gasoline absorbs 349 Joules of heat energy in going from a liquid to a gas. So for the total fuel flow of 1120.1 gram/min this comes out to:

Joules absorbed = 1120.1 gram/min * 349 Joules/Gram = 390914.9 Joules/min

Dividing this by the Joules per deg C per minute for the air massflow comes out to:

Temp drop Deg C = 390914.9 Joules/min / 13441.7 Joules/min-deg C
Temp drop Deg C = 29.1

Converting to Deg F:

Temp drop Deg F = 29.1 deg C * 9/5
Temp drop Deg F = 52.4 deg F

So with a 12:1 a/f ratio it looks like the total amount of fuel going into vapor state would cause a drop of air temp of around 52 deg F.

Now the thing I am interested in is what temp drop would E-Cool (aka the extra injector) would cause in the intake manifold. I am figuring at most the extra injector would inject 1/3 of the total. So at most, in the intake manifold, the temp drop because of E-Cool would be around 52.4 deg F / 3 = 17.5 deg F

So, something else must be the cause for an observed 100 deg F temp drop from E-Cool?

In comparison to gasoline with 349 Joules/gram, water has a latent heat capacity of 2260 Joules/gram... about 6.5 times as much! Running water injection for the above calculation with a typical 15% water to fuel ratio yields:

fuelflow gram/min = 1120.1
waterflow gram/min = 1120.1 * 15%
waterflow gram/min = 168.0
Joules absorbed = 168.0 * 2260 Joules/min
Joules absorbed = 379680 Joules/min
Temp drop Deg C = 379680 Joules/min / 13441.7 Joules/min-deg C
Temp drop Deg C = 28.2
Temp drop Deg F = 28.2 deg C * 9/5
Temp drop Deg F = 50.8 deg F

Interesting the total temp drop from injecting water at a 15% water to fuel ratio is slightly less than the total temp drop from injecting the fuel... however you inject both so you get a double temp drop. With the E-Cool it looks like you would get 18 deg F temp drop in the intake manifold and then the remaining temp drop of 34 deg F in the combustion chamber (before ignition) for a total of 52 deg F temp drop. With WI you would see a 51 deg F temp drop in the intake manifold and then a 52 deg F temp drop in the combustion chamber from the fuel injected (before ignition) for a total of 103 deg F temp drop. The thing that confuses me is from this analysis it looks like the temp drop would be the same for a larger injector setup vs. an E-Cool setup if they are running the same a/f ratio. Unless, not all of the fuel is vaporized that is injected in the combustion chamber?

Bill
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Old 04-19-2007, 01:02 PM   #14
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Quote:
Originally Posted by magnamx-5 View Post
http://forum.miata.net/vb/member.php?u=25657 251 ml/min spray has a capacity of 567620 J capacity
16989.6 g/min air flow AF of 12.5
1359.12 fuel flow
33 C heat removal potential from the WI alone
474332.88 J from gasoline gives me another 27.9 C
and 33.4 C from the WI for 61.3 C reduction
My system comes out to be 18% considering i optimize at 12+psi and flow more than 500cfm wich is doable. I run a 20-30% methanol content as well and have noticed that works alot better than striaght water, and or lesser or more agressive mixturers
MMkay
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Old 04-19-2007, 01:04 PM   #15
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Colder is always better unless your ecu cant compensate correctly our stock ecus for example are way to rich in the cold meaning we lose to much power on untuned AF ratios, and incomplete combustion.
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Old 04-19-2007, 07:26 PM   #16
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Well, I guess if E-cool didn't lower intake temps, the E-cool would be a farse.....just a fifth injector adding some extra fuel. I'll post my results once I get a WI system hooked up. I should be able to video tape my intake temp guage before and after.
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Old 04-20-2007, 04:12 AM   #17
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As boostinsteve says,
Unless you've got some sort of deflector around the temp sender the temp readings are not going to be accurate as it will become saturated.

Can't say as i've got the patience or Mathematical aptitude to do the calculations,
But from what i've seen and read on various posts and white papers it's not physically possible to get the temp drop most are seeing, so the only thing i can put it down to is temp sender saturation.

As for the air volume and IC debate, for most SC'd |Miatas your right, i'm really nervous that i'm going to lose that instand throttle response with a IC.

But if you Turbo'd, Coldside'd Rotrax'd the TB is after the air pump so air volume before the TB is not as much as a issue.

I'd love if WI would enable me to run the stock timing curve at 11psi, that way i've still got decent airflow to my AC and radiator, i've got a managable throttle volume, and i save some money

But it's just not possible, i'm having to pull 6 degrees, this in turn ramps up my EGT's, not much of a problem now as the ambient is in the mid 20c's.
But when summer kicks in and it start creeping into the high 40c's, i'll have to either go back to 9psi or fit a IC.


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Old 04-20-2007, 11:01 AM   #18
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ahem i ran it at 12 psi with my 16g turbo hell i ran it at 15-16 psi on stock 10 btdc timming, with no timming controller. WTF man. Hell steve is running 10 psi. and pulling no timming. I think you are being abit to pessemistic with your tunning man.even Jesus needed to be asked before he healed some one most of the time. Let WI prove itself for you. I for one think the reading most get on there temp probes is to high and they are either doing something wrong or dont want to let everyone in on just how effective it is. you might just surprise yourself with WI man. If you can take care of the fueling part of the equation then it will support any boost level you like. I intend to prove this once my MS is up and working right. I only want 17 psi on this turbo but if a upgrade i might run 18-19 psi or so. On a bigger turbo.
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Old 04-20-2007, 11:11 AM   #19
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Only just upped to 11psi, i was running 9psi without any timing being pulled, 14btdc base and the stock timing curve.

I guess at 11psi the lil old MP62 has reached a point of it's efficiency and output heat, that my car just can't seem to handle it any more.

How you guys monitoring knock?
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Old 04-20-2007, 11:24 AM   #20
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the old listen and lift technique. fWIW yeah the stock MP62 is reaching 100% VE at 10 psi. you might look into porting the blower or, tunning the boost you have better. here is a site with the specs. BTW more boost is not more power, so you migth just need to optimize at 10-11 psi. to save your blower abit of wear and tear for little to no gain and probably a HP loss up top. Also here is a site with abit of Info for you. http://www.capa.com.au/eaton_mp62_4th.htm
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