lmt0705

iTrader: (7)

Changing up my cold side and have to do some welding and I was wondering if my iat sensor has to be before my meth nozzle or can I put it after? Will it give a bad reading if it gets sprayed on?

3 window

iTrader: (1)

From what I understand, better to have it upstream or before your meth nozzles. Otherwise a soaked sensor will read colder than the actual intake charge.

cmiller8006

iTrader: (1)

I have always wondered how you get an accurate reading then? I am running E85 in the vette and am also seeing 200 degree iat's with no meth at the traps, its set up to not pull timing but am wanting to throw meth at it just to cool the charge a bit.

JoeNova

Most put the IAT sensor in the charge piping so that they don't spray meth on it. You drill/tap it in exactly like you would the meth nozzle.

cmiller8006

iTrader: (1)

But how do you know how cool your getting it if its after the iat that its being sprayed? I have plenty fuel and what not, so was looking into the meth/water just for the cooling of the intake charge since the twins make lots of heat.

JoeNova

You can put the IAT after the meth nozzle, just try to keep the sensor shielded so it doesn't get methanol sprayed directly on it. Otherwise, the IAT sensor will read false temps if it gets soaked in methanol that is starting to evaporate.

3 window

iTrader: (1)

You really don't. Just let it do it's thing. You'll know by the change in your AFRs. Not sure on the drop, but it depends on how much of what (50/50, 100% meth, etc.) you're spraying.

lmt0705

iTrader: (7)

That sounds like it would be really tricky keeping it from getting sprayed

stevieturbo

Wont do it a button of harm getting sprayed.

And it would be silly to place the sensor before the spray, as whether you believe the readings to be accurate or not, after the sensor at least there is a recognition something is spraying and carrying out some charge cooling, and hence any air temp compensation tables for tuning can at least be of some use.

It really would be pointless having the sensor before any nozzles.

stealth355tpi

Meth nozzle before the throttle body and my sensor I have tapped into the back of my ls6 intake. It's an instant drop in temp as soon as my meth comes on.

Forcefed86

iTrader: (4)

I don't agree. What good data comes from a false reading saturated sensor? You can't tune by it. I suppose it would let you know the methanol is "on".

I prefer to know what my actual charge temps are and use that data to trim my timing table accordingly.

Cooling the air charge is a slight side benefit IMO. You aren't cooling the charge air by much as a whole. The major benefits are in the CC. I'd think an EGT probe would be the best way to measure Aux inj. temp drops.

stevieturbo

If your sensor is before the nozzle, you'll never know what your charge temps are near the intake valve, or even close.

And who says it's a false reading ? It's a reading, as long as the reading is repeatable and consistent, it doesnt matter a damn what the numbers say.

Why would you think the sensor would get saturated ? You'd be hoping all the meth evaporates as soon as it is injected anyway, so there shouldnt be any cooling effect on the sensor from that aspect.....but really, even if there is, it really doesnt matter.

But it is certainly far better to have that reading which is affected in some way by the methanol, than taking a reading that is never impacted by it.

It would be like placing a sensor at the compressor discharge, before any charge cooling....It's just stupid for getting any sort of picture of what is happening much closer to the intake valve.

Forcefed86

iTrader: (4)

Of course it matters what the numbers say… The point of an IAT sensor is to give an accurate representation of the true charge temp entering the engine. If the temps reported aren’t accurate the data is crap.

The charge temps aren’t largely effected by aux inj. Compare the amount of fluid injected to the amount of air ingested per minute. It’s easy to see that the aux inj fluid can’t effect the air temps much as a whole.

Even injecting 2gph of 50/50 pre-turbo and pre-IC my sensor would report false over cool readings. If your using your IAT to tune the fuel/ign curve then I want an accurate representation of the true air temp. Esp. if we are talking about factory ECU’s with little adjustability.

It’s nothing like placing the sensor pre-IC. Again, that sensors purpose is to give an accurate representation of the true air temp ingested. That isn’t happening with a saturated sensor or a sensor pre-IC. The difference being the charge temps reported post IC are accurate.

stevieturbo

Well if you have the sensor before the nozzle...then you'll never get an accurate, or even inaccurate picture of charge temps near the intake valves.

And charge temps can be massively affected, of course it all depends how bad charge temps are prior to injection, and how much you're injecting.

No idea why you think the sensor will be saturated. It simply does not happen.

zapp109

iTrader: (13)

My meth nozzle is about 12" before my IAT sensor. Yes my sensor gets sprayed on. Ive never noticed lingering temperature from that. HOWEVER I have replaced the sensor after about 18 months of running it. Stopped working, said it was -29 degrees. But no big deal got another one with lifetime warranty so next year If it happens again just swap for a free new one.

stevieturbo

I've been spraying on the same sensor for several years, never had any issues

Forcefed86

iTrader: (4)

I've got the data to prove it does happen. This is easily seen by the "too good to be true" IAT temps some of these guys report. The temp drops reported aren't physically possible. If the reported IAT's were accurate, then none of us would need intercoolers. Yet an intercooler will make more power than aux inj alone every time.

stevieturbo

And equally I've data to prove it doesnt happen.

I run with/without meth all the time so know my charge temps as they are without and what they are with meth.
Basically anywhere except when drag racing or 1km etc I dont use meth, simply because I dont need any additional power it can yield. So I can as easily run 20psi boost without meth, as I can 20psi with meth and of course there will be differences in charge temps seen
I've tested with the sensor about 3-4" from the spray, and also in the intake manifold itself ( carb intake, sensor at the carb flange spacer ), and really it makes little odds to the readings.

Really though it doesnt matter, as long as the readings are consistent and this is what you're tuning with, that's all that matters. But whilst it is a very slow failsafe, knowing whether anything is offering additional cooling or not just makes sense.

Running meth and having no notion about whether it is or isnt spraying is just silly.

If you really want to get a better picture of intake charge temps, stick a thermocouple in down near the intake valve.....except you'll maybe get a "false" reading there too as you spray fuel there.

A reading is a reading....how you interpret or use it is up to you. No different than a map sensor, temp sensor, TPS, wheelspeed etc etc. But having more useful readings is always better than useless.

Forcefed86

iTrader: (4)

What data do you have that indicates meth/water doesn’t falsely skew temp readings when sprayed pre-sensor? How can you verify the sensor isn’t saturated? I’d like to know how your system can be so different from the many I’ve worked with.

Silly to you maybe. To me it’s silly to record useless data. Measure exhaust temp drop if you want data that’s worth something. A wet exposed element type temp. sensor is will not have the same accuracy as a dry sensor. The readings aren’t consistent or linear to a dry sensors readings.

Use a hair dryer and a water bottle and do a little test. Measure the temps with the hair dryer on low, then on high and measure the difference between. Say you got 150* on low and 200* on high. Now do the same while misting water over the sensor. Not only will the temp readings be falsely low, but you won’t see the same 50* temp spread between low and high. The sensor is NOT designed to work in a wet environment…period. The data it reports in this sort of environment is crap IMO.

My ecu activates my meth and I use a pressure switch and a light. This is more than enough to know the system is running, I don’t feel I need to sacrifice good IAT sensor data in place of an on/off switch, which is all a sensor placed post inj. point is worth. Even used in this way it will not tell you if the pump/system is maintaining “X” pressure.

A reading is not a reading. None of the other examples you make are similar in any way to a saturated open element temperature sensor. The skewed readings are not linear with a saturated temp sensor. Actual temperature data VS on/off data is much better IMO.

stevieturbo

This is going to be one of those things that goes round in circles.

The further away from the intake valves you take your charge temp reading, the less useful it will be.

If you dont allow it to take into account any extra cooling whether you choose to believe the readings or whether they are accurate or not, the reading becomes meaningles if you are ignoring the spray.

As for a reference to an on/off switch, not even sure what that's referring to ? I've never seen any temp readings remotely like that ?

The test you propose is useless. A more comparable to actual conditions test would be placing your temp sensor in a typhoon or hurricane, then spraying some water onto it and see what happens
But even the suggestion of a hair dryer and water sprayer to try and replicate an engine consuming say 1000-1500cfm when a hair dryer might produce 2-3cfm ?

Nope...aint happening.

And again you make an assumption the environment is "wet"....why so ? Are you not expecting any of the liquid to evaporate ? Are you not expecting an extremely fine mist in among that massive volume and speed of air ? Do you think the sensor would have any time to get drowned ?

And a reading is a reading, all of the examples I listed are valid. Whether a reading is linear or not....??? irrelevant. The reading is the reading taken from the environment you're working with close to the engine where it is used.
Placing the sensor far away, would be like placing a lambda sensor prior to the combustion chamber...

It's just wrong.