Talking about the twin turbo 5.3 Truck I'm helping with.

At 23 psi the IAT hits 210 degrees. Meth nozzles are after the sensor.
I have the IAT table set to pull timing above 180 right now.
Of course I have no idea what the real temp in the manifold is.
I've read all the arguments about spraying the sensor.
Seems like putting the sensor in the manifold would make more sense?
Right now we are sort of flying blind.

I also discovered that we have the meth coming on around 6 psi. Which has it coming on while on the two step. I'm assuming we should change that.

Ron

 

Either way I think you will be blasting the sensor with some sort of mist causing faulty IAT readings. I'm assuming no intercooler? What turbos are on this set up? Adding water to the injection will help to get the actual IAT's down.

 

It does have an intercooler.
The whole kit comes from CX Racing.
So I don't know much about the turbos.
The IAT's seem really high to me. Especially since ambient temps were mid 60's.

 

That's interesting, mine is barely above ambient hitting 14psi on a 31 x 12 x 4 intercooler with a billet S475. My IAT is just before the throttle blade, but after the BOV. I was going to put my two 15GPH nozzles between the BOV and IAT.

 

Which intake manifold? I swapped to a TBSS manifold and installed an IAT in the intake. It doesn't protrude into the plenum like it did on the old style truck intake. Since its recessed slightly, I'm going to assume the methanol won't effect the sensor nearly as much as before. If my IATs read differently from the small location change, it might make it viable to keep the IAT in the intake while running meth injection.

Running meth on the 2 step is fine, it may help hold a consistent boost level compared to gas.

 

Where is the sensor located?

 

Normal truck intake.
Sensor is currently in the middle of the charge pipe.

When it gets on the two step, you can hear it struggle when the meth turns on.

 

When you're on the 2 step, you're basically flooding it. Methanol is harder to ignite and will keep it from building too much boost. My setup is a torque monster and builds 8 PSI in 2 seconds on a 3200 2-step and creeps up to 14 PSI in a couple more. With the antilag on, my wastegate is open within 2 seconds on the 3200 2-step.

With water/meth on at 8 PSI, it won't creep up past 8 PSI without the antilag on. If you want to build more boost, raise the PSI that the meth kicks on.

 

I think the issue with the IAT sensor and the meth is spraying too close to the sensor will load it up with the the flud. Same goes for MAFs... too close and it causes issues.

I'm running my IAT sensor in the truck intake where the EGR used to be. I basically run a block off plate that I drilled and tapped for 3/8"NPT. Reason for mine is that I want the IAT to sense the drop in Air temps when the Meth/water is engaged so it knows to keep the correct timing trim. If it doesn't sense the drop in temp then it will retard the timing according to what I program. So the sensor acts like a fail safe. I installed a snow kit with a 375ml nozzle and planning to run wiper fluid. But mine is a stock 5.3 with a centrifugal running 10-12psi.

If it eats the sensor ( and I doubt with wiper fluid) then its only a $20 sensor but I'll know the IAT that the motor is actually adjusting.

 

Kevin Jewer did some extensive straight meth testing on his compound setup. He found at 1000ish CHP levels (100lb/min airflow) it takes 8gph to drop the charge temps 15*. Double the temp drop for 500CHP worth of air. So 8gph will drop charge temps roughly 30* at 500lb/min. He was spraying 48GPH+ pre-compressor however with no IC on a compound setup. So his results won’t apply directly.

Personally I’d mount the IAT sensor just after the intercooler outlet. To get your actual charge temps. Then spray your fluid pre TB. Using the math above you can roughly calculate what your charge temps are. Shoot for 150-160* “safe zone” and you should be golden IMO. Last week’s passes I was around 110* at 17-18lbs and 62* ambient. 1200HP treadstone IC, 370”, S476.

Your temps sound super high to me. I’d guess those turbos are out of steam at the current boost levels on that engine. The cheap IC could also have a huge pressure drop and not be very efficient to start with, which will make the turbos work a lot harder.

Temp probe on the turbo outlet will also give you a good idea how hard you are pushing the turbos. (Typical plastic sensor will probably melt in short order though.)

 

I tend to agree with this. For me, if you are putting the IAT pre meth, then the tune is obviously wrong. Because if you are on a speed density setup, then your tune is obviously using the ideal gas laws to come up with airmass. And the IAT is a big one for that calculation. So basically you are having to skew the VE table to make it all work correctly. I would spray meth directly after the intercooler, and then put my IAT right before the TB.

 

How does that make sense? As you say SD tune relies on correct charge temperatures. Putting the sensor downstream of a ton of methanol will give you a horribly inaccurate IAT measurement. Most don’t spray enough methanol to drop the actual charge temps more than 30-40* anyway. Yet if you saturate the sensor with fluid it can report 100+* temp drops. So in most cases it’s much more accurate to tune with the actual charge temp than the skewed charge temp.

 

Well you say for most cases, but in every meth car I have tuned, I have noticed no discrepencies in IAT activity. Maybe it is different if you are spraying 20GPH directly onto a sensor.

 

And ignoring the fact the spray will be cooling the charge by placing the sensor before the spray will also result in an inaccurate IAT reading because it cannot take into account whether charge has or has not been cooled...as it will never know.

So it's a choice between possibly skewed a little with spray before the sensor, or completely wrong ( ie ignoring it ) by placing sensor where no spray will ever touch it.

But we've been over all this before.

 

Thanks for chiming in guys.

This is an Alky Control system with two nozzles. 10 and 15 gph.

In spite of repeated phone calls and detailed emails, our questions have been ignored. So bottom line on that, I don't know exactly how the setup works. It seems that it increases volume with boost.

We put one new plug in cyl 1 several times during the day, and all was well.

I agree completely that the PCM is adjusting fueling based on what the IAT reads, and that I'm skewing the VE to keep the AFR at 11:1.

I've no clue how well the truck intake deals with distribution when more than simple airflow is involved. A check of all plugs after the day revealed no issues.

That said, it makes sense to me to know what the actual temp in the manifold is.

Which leads to, why are the IAT's so hot to begin with?

Bad IC? Restrictive IC? Turbos way past their efficiency range?

All possibilities! And to really sort it out will require sensors and measurements to see what's really happening with these parts.

 

Exactly what controller is it ? That will tell you what it might do in relation to boost...as you need to configure it.

And the PCM will only alter fuel/spark based on any parameters you tell it whether in relation to IAT or otherwise.

And you're skewing the VE because you've just dumped in a load of fuel from an external source....that's just called tuning !

First off do you know your IAT sensor reads sensible values ? ie is it correct ?

After that temps are down to efficiency of the system and how much cold air it starts with, and can try and keep it cool thereafter.

Is the turbo drawing in cool or hot air to start with ?

 

In reality, you can tune either way. Its safer to tune with the IAT in the cold side before the nozzle because you are tuning for 'worst case' IATs. Is it reasonable to tune with the IAT in the intake? Yes, because I do it. However, my IATs with the water/meth on never go above 100 degrees, so if something happened and the pump failed or the tank ran out, I would suddenly have 200 degree IATs at the end of a pull that I haven't tuned for. The flipside to this is that I can force it to pull lots of timing once the IATs go above 100 degrees as a fail-safe for the pump dying or washer fluid running out.

There are obviously upsides to tuning it either way....

 

Wont matter a damn, and I never understand why people fixate only on IAT's as that is only one aspect of what water/meth does.

If meth fails almost regardless of which method you choose ( worse being not spraying on IAT sensor ), you've instantly removed a ton of fuel and octane, and detonation suppression from a system that was reliant on it.

Things will get nasty.

And if as you describe your'e spraying onto the sensor and temps suddenly go from 100 to 200 deg ( baring in mind even so called fast sensors are still very slow in engine terms ), at least you could try and apply some failsafes based around these hot charge temps which is what you're doing and to me seems the most sensible approach

If the sensor never sees spray and always the inaccurate and high charge temps pre-spray, there is no possibility of any safety based around this...or any way really. Failure of meth flow in any shape or form will be catastrophic unless you are implementing some other form of failsafe externally based on actual meth flow.

 

The moral of the story is was giving is that you put the IAT before the meth nozzle, and then don't tune based on the meth. You tune for high IAT without the methanol injection on, and then use the methanol as supplemental fuel/safety cushion. This works very very well for a pump gas and 50/50 mix as it effects your A/F ratio less.

Ron, does this truck run gas or E85?

 

I agree with some on this thread and obviously it's why I had set mine up with the IAT in the intake (after the meth). I'm not using the IAT as the only form of tuning but it's a fail safe for or if there is a problem with anything before the intake. Say something happens with the meth kit or something before that would cause a drastic change in IATS? I would want the ECM to be able to react in some form to keep the engine from destroying itself.

By putting the IAT in the intake you measure the actual... ACTUAL IAT temp of the air going into the motor as about as accurate as it can be. Things like heatsoak etc in the intake will change IAT temps even after going through an IC. So what's the point in measuring the temp before or after the IC if it changes by the time it gets into the warm motor. Sure someone could argue that the air is moving so fast that outside temp doesn't affect it much but the whole point of sensors is to be as accurate as possible. This is why fuel pressure regulators are on the fuel rails... As things that regulate pressure or sense temp, pressure are at their most accurate at the source. Regulating fuel at the tank is not going to react as well as it on the fuel rails and you only care about the pressure at the regulators for instant accurate changes and tuning depends on it! So why not apply that to IAT sensor? Putting it at the last point before its ingested into the conbustion chamber is the most accurate way to measure actual IAT temps. Remember the IAT will sense he final air temp before being burned this means after IC, heat soak, chemical cooling etc. Putting the sensor before the meth means your tuning for a much higher temp and not actual temp. Putting the sensor after the meth means your sensing actual temp which could be screwed by meth/water on the sensor but it's not going to be as inaccurate as the sensor before the meth. Both have their inaccuracies but I believe in tuning for the most accurate reading on any sensor. Remember if the meth doesn't work then the IAT will still read actual air temp with the system not working and can continue to pull timing. Think of it as arming a NOS system which requires a window switch to activate, if something happens and the window switch/wot switch doesn't activate then the NOS doesn't fire. If it does and all goes to plan then the NOS setup will and should pull timing. So if the IAT sensor sees a large drop in temp then it should signal to the ECM that it should pull "less" timing that it would normally at higher temps. In the off chance the sensor reading is skewed by the meth/water and that would vary on application of the system, setup, quantity and sensor I feel that it's still the way to go. Same application goes for inter cooler... You wouldn't put the sensor before the IC where your reading max turbo/SC heated air... You want the cooler air on the otherside of the IC.

Heat soak is a real problem and everything in the engine bay will get warm but the engine is still the warmest spot and therefore all sensors should be installed there. Most of us run stock thermoplastic intakes so heat soak is less of an actual problem than it used to be with older aluminum or iron intakes where hot oil was splashing on it from the lifter valley. OEM ran the IAT in MAF cars in the MAF for packaging and ease of install.

To the OP:
High IAT temps could be turbos being out of steam, outside of their efficiency range, heat soak from turbo Hotside plumbing, lack of engine space and not enough engine bay cooling/air flow. Can also be cheap inefficient or undersized IC, lack of airflow through IC. I also know that not all meth kits are created equal and droplet size, flow, pattern and the amount of water affects how efficient the system is. Not familiar with the alky setup but they don't use high pressure pumps right? They rely on boost pressure etc to force/pull the fluid in which is why they are rated at GPH and not CC/ML. I personally prefer high pressure pump and a super fine mist/droplet size for the most cooling and distribution.

Sorry for the rant, this is just my opinion. I like my sensors to be the most accurate. My fuel pressure sensor is in the fuel rail or the regulator, engine temp/coolant in the engine, oil temp in the oil pan, tranny temp in the pan, MAP sensor in the intake etc. I also run my meth kit with wiper fluid or 30/70 mix as I want it more for cooling and detonation control vs octane. This is because I don't run an IC and should see 10-12psi and meth activation is at 5.5psi with a 375cc/ml nozzle for now.