Intercooler Water Spray - Trigger Point

[MearCat]

I am designing an automated intercooler water spray (kind of based on the intelligence of the Autospeed one, but will be much cheaper and smaller) where the spray will activate when 1) The air flow through the AFM is above a configurable point AND 2) The intercooler is hotter than ambient by a configurable amount.

What I would like to know is what you guys/gals think is a reasonable temperature set point for a spray trigger. ie How much hotter than ambient should an intercooler be before the water spray is activated?

Please consider what would actually be beneficial to both performance/cooling advantage and water saving when voting in the poll.

Cheers!

Alan

[BAMR33]

Don't bother, just get a FMIC (which you will probably do anyway) and put a thermo fan behind it.

[MearCat]

I do have a FMIC, but this design is not just for me. It will be for my mate with a TMIC on his WRX as well and another with a 300ZX.

This intercooler spray module design will include an output for a water pump anf maybe an (optional) thermo fan as well

[Craved]

my exaust guy does rally panel beating too, he has a WRX rally car that he works on, for the rally the water spray is activated over a certain boost pressure, and only if this pressure is active for X seconds.

just an idea rather than a temp sensor

[BAMR33]

I do have a FMIC, but this design is not just for me. It will be for my mate with a TMIC on his WRX as well and a few others.

This intercooler spray module design may include an output for a water pump as well as an (optional) thermo fan as well

Tell your mate to sell the rex and get a skyline

[MearCat]

my exaust guy does rally panel beating too, he has a WRX rally car that he works on, for the rally the water spray is activated over a certain boost pressure, and only if this pressure is active for X seconds.

just an idea rather than a temp sensor

In rally situations - yeah fine, but personally I don't think that's such a good idea in a street car because there's no point in activating a water spray if the intercooler is not hot. The intercooler is doing it's job fine until is starts getting heatsoaked. It's just a waste of water otherwise.

[CEF11E]

Hi Mearcat.

I am in the process of desigining a cost affective water spray kit for the inter cooler and was just going to activate it with a hobbs switch and temp sensor just before the TB.

I would suggest the best place to put the temp sensor would be before the TB. it will give you a better reading of what is going into the engine. The only dis advantage will be you loose the ability to measure heatsoak. Seeming as it is a FMIC heat soad should be minimal

So Will you be using AFM load between say 1 and 5 volts as a trigger? That's a good idea.

[paulr33]

1 and 5 volts its too narrow

its at 1.2v at idle, i would suggest around 4 volts its on max load / full load

the ideal way to activate the system would be on intake air temp

that is airtemp inside the pipeing after the compressor outlet

that way, regardless of environment, once the intake temps are over X it will activate, and help with heat extraction on the core. you should also tie it into AFM v or load so that even if the airtemp is say 60deg but afm is only 2v then theres no need to activate it

[MearCat]

Let me clarify what the proposed kit will do :

It will have 3 main inputs to it - AFM voltage so that you can set anywhere between 0 and 5V as the first trigger. There are also 2 thermistors (one mounted somewhere in ambient ie bumper area; one mounted in the fins of the intercooler). There are some jumpers on the circuit board which allows you to set how much hotter than ambient the core will be as the second trigger. These triggers WILL be tied together so that when the air flow is higher than eg 4.1V AND the intercooler is eg 10degC hotter than ambient, the kit will activate a relay (for a water pump up to 7.5 Amps) and keep spraying while either triggers are above the set point. If the AFM voltage drops below eg 4.1V, the spray will stay on for ~2 seconds, unless it detects that the intercooler is REALLY hot, then it will stay on for a further 3 seconds.

Paul, I like the idea of using the intake temps as a trigger I want really want to keep the cost down for a kit so will be using relatively cheap themistors instead. I think using a quality thermocouple probe that can be fitted to your intake would increase the cost too much. I believe that by taking time and effort in changing the "how much the core is hotter than ambient" setting correctly (by trial and error) it will give you a similar improvement than using intake temps as a trigger.

[mokompri]

the ideal way to activate the system would be on intake air temp

that is airtemp inside the pipeing after the compressor outlet

that way, regardless of environment, once the intake temps are over X it will activate, and help with heat extraction on the core. you should also tie it into AFM v or load so that even if the airtemp is say 60deg but afm is only 2v then theres no need to activate it

generally speaking water spray kits are used to combat against heat soak or the core reaching heat saturation. if the core isnt saturated and is giving say temps only 10deg above ambient post intercooler then it wouldnt make much sense to use the spray based on compressor outlet temps, because that would be whenever it reaches a certain boost pressure/rpm but could still pumping out reasonable post cooler temps.

it would be much more effective, efficient and economical to use the spray based on temps POST intercooler, once the core is saturated either through constant boosting or heat soak and you start seeing temps say 25 degrees above ambient, then the spray will come to good use to bring it down and remove excess heat from the core.

personally i dont think AFM voltage or load/TPS voltage are needed as parameters either. the goal of the water spray setup is to stop temps into the engine (post cooler) from being too high. regardless of what the afm or tps is doing, if the temps are too high, it should be activated. if the temps are low, and your afm output is activating the spray, then its pointless because the temps were already fine. running all the inputs in series wont be as effective either, because you may have a situation with high post cooler temps but the tps voltage is still too low to activate the spray.

[Abo Bob]

Hmm, there's no point spraying your cooler when the car isn't moving so a purely temp based trigger is not good. I think AFM voltages over 3 would be fine.

[mokompri]

Hmm, there's no point spraying your cooler when the car isn't moving so a purely temp based trigger is not good. I think AFM voltages over 3 would be fine.

consider everything, outlet temps arent going to much over ambient when the car isnt moving because your not on boost and in vacuum and thus it wont switch it on, because those conditions (high temp + stationary) will never be met !

if somehow you are getting overly high temps when your on vacuum, then your cooler must be SERIOUSLY cooking and over saturated, in which case the spray should come on anyways, to reduce the cores temp and bring up its efficiency again

[Bass Junky]

I think that you should take two air temp sensors.

Ambiant air temp and inlet air temp.

you will never get the intercooler below ambient temps.

Maybe if there is a difference between the two up more than a certain amount for a pre-determined time, then you activate the spray.

you could also say that you wouldn't need to activate it until the temp get's above a certain amount also.

ie, it's 0 degrees outside and your inlet it 25. no point really until the inlet is about 35-50 as that's pretty cool anyway considering.

[Bass Junky]

If you used AFM over a certain amount, give it two laps of a track and you would be all out of water and your mates behind you would be pretty pissed at the stream of water coming out the back of your car.

[Bass Junky]

I think the Autospeed one is very clever in the way it works.

They have identified that the intercooler is a heat sink first and foremost.

They identify that the inject pulses are the key to showing how much the car is being driven.

I think the only other way to do it would be to use an inlet and ambient sensor as mentioned above.

But you have to add a switch off also.

Imagine a thrash around the track, you heat soak your cooler.

Then you park it and let it cool down. The heat sink is going to be transferring it's heat back into the air flow, and surely the temps will be high enough going into the inlet.

You would want to cap the sprays at maybe 2 seconds every 10 when the AFM is low, otherwise you will end up with a wet intercooler which isn't really doing much cooling as the water heats up and insulates the heat.

[mokompri]

Imagine a thrash around the track, you heat soak your cooler.

Then you park it and let it cool down. The heat sink is going to be transferring it's heat back into the air flow, and surely the temps will be high enough going into the inlet.

well if its setup to spray when temps go up, it shouldnt ever become heat soaked as its cooled by the water.

it depends where the switchover point is, but if you set it at around 55-60 degrees, then intake charge temps should never reach that whilst in vacuum, no matter how much the cooler has been heat soaked.

and yes the autospeed ones are quite good !

Edited October 26, 2006 by mokompri

[MearCat]

If you used AFM over a certain amount, give it two laps of a track and you would be all out of water and your mates behind you would be pretty pissed at the stream of water coming out the back of your car.

If assuming the spray is activated on a high inlet temp AND high AFM voltage - If you're doing track work and your intercooler is heatsoaked enough to activate the spray constantly, I think you're concern would be the efficiency of your intercooler more than anything else.

[MearCat]

Well it seems I've opened a can o' worms here with how the spray should be activated.

I ask this then - if the spray is triggered based on a temp, then what advantage would reading the the inlet temperature be over having the temperature read at the outlet side of the intercooler. After a good workout, an intercooler core inlet side will be hot and the outlet side will (hopefully) be cool. Having the thermistor mounted in the fins right next to the outlet end tank should read a very similar temperature to the engine inlet temps. I don't think there would be much of an advantage using an inlet temp instead of intercooler core temp as the comparison against ambient temps.

Even if you think that the air temps pickup say 5degC between the intercooler to the engine, then simply keep the temperature read at the intercooler core outlet and set the trigger point to be 5degC lower.

[Bass Junky]

I just thought the faster response of the air temp sensor in the air stream would activate it quicker.

what you don't want is a soaking core.....

[mad082]

i would either go a hobbs switch or just an intake temp sensor. i wouldn't do it as ambient vs intake, otherwise on a 40 degree day you are going to have very high temps before the spray starts, and on a cold day you are just wasting water.