MAP sensor relocation

Vmcrdrod · **Joined:** Wed Mar 22, 2017 9:21 am **Posts:** 33

Does anyone know I’d moving the MAP upstream of the fcv will Yield false readings I’m thinking the dynamic flow pressure changes would be sensed faster and could wreak havoc with the vanes and fuel flow but I’m not sure. I want to do a water injection install for towing but because the map is in the intake I don’t want it to get soaked and give bad reading and effect ecm map with air density parameters. Thanks

flash7210 · **Posted:** Thu Dec 19, 2019 1:14 pm

With water-methanol injection the liquid should be spayed in a fine mist that instantly vaporizes when sprayed in the intake path. If done right it will not effect the MAP sensor and the sensor will provide an accurate reading to the ECM.

WWDiesel · **Posted:** Thu Dec 19, 2019 1:57 pm

Totally block off the EGR valve with a block-off-plate and then remove the butterfly plate out of the FCV.
Then you can move the MAP if desired, but keep in mind the MAP is also measuring temperature as well as pressure.

EGR Block Off:> viewtopic.php?f=5&t=76576
FCV Butterfly Plate Removal:> viewtopic.php?p=914265#p914265

Vmcrdrod · **Joined:** Wed Mar 22, 2017 9:21 am **Posts:** 33

OK but at 15 psig the boiling point is something like 250 degree F right i didnt think that the inlet stream got that hot. The way I understood it is that the atomized mist of water absorbs heat through the inlet stream then changes state in the cylinder from liquid to gas to liquid and back to gas as it exits, but while it's in the intake because of the increase in pressure it remains a liquid unless charge Temps raise above boiling point under pressure then the vapor would convert into steam. Now I may have something mixed up here but I know that in boilers pressure is used on heaters specifically the dearator and the steam drum also in hvac and inbottled gas so that's why I'm assuming that it behaves the same under pressure in the charge system. The huge difference being that they're in a vessel as apposed to a pipe but the idea o pressure holding the water in the liquid state I would think would be the same.
Now the methanol I know has a much lower boiling point but I don't really want to run meth if I can get away with it.

Vmcrdrod · **Joined:** Wed Mar 22, 2017 9:21 am **Posts:** 33

WW, thanks for the insight that's my biggest concern about leaving it in the intake is that it will effect the temp reading throwing the maps into a frenzy trying to adjust for the denser charge that It thinks it has. The other thing I'm worried about is that because the sensor is moved from the intake which is much lager than the cac the changes in load will be read much faster causing the turbine vanes to to actuate faster than normal and negatively effect boost pressure and also wig out the fuel injection process.
Am I over complicating this or is it a legit concern?

WWDiesel · **Posted:** Thu Dec 19, 2019 2:55 pm

Vmcrdrod wrote:

OK but at 15 psig the boiling point is something like 250 degree F right i didnt think that the inlet stream got that hot. The way I understood it is that the atomized mist of water absorbs heat through the inlet stream then changes state in the cylinder from liquid to gas to liquid and back to gas as it exits, but while it's in the intake because of the increase in pressure it remains a liquid unless charge Temps raise above boiling point under pressure then the vapor would convert into steam. Now I may have something mixed up here but I know that in boilers pressure is used on heaters specifically the dearator and the steam drum also in hvac and inbottled gas so that's why I'm assuming that it behaves the same under pressure in the charge system. The huge difference being that they're in a vessel as apposed to a pipe but the idea o pressure holding the water in the liquid state I would think would be the same.
Now the methanol I know has a much lower boiling point but I don't really want to run meth if I can get away with it.

But the flaw in your thoughts are, the boost pressure is not constant so the latent heat of evaporation rules cannot be applied in this situation.
If I were going to do this, which I am not as I don't need anymore power, I would put the injection point just after the CAC (intercooler outlet), remove the FCV butterfly, block off the EGR feed, and leave the MAP where it is. I would start off very slowly with very low injection rates and see what effects both power wise and temperature wise it has on the engine.
You certainly need to be monitoring all the running parameters with some good software like the ELM 327 or a similar type to see what benefits if any you get from the water injection and its effects on boost pressure and temperature. An EGT temperature gauge would really be nice as well to see what effects it has on EGTs leaving the cylinder before it hits the turbo turbine blades. :juggle:

Vmcrdrod · **Joined:** Wed Mar 22, 2017 9:21 am **Posts:** 33

I get that it's dynamic but it's still above atmospheric so the BP would still increase. My point is its still a liquid and it would bring the MAP reading Temperature down that along with the pressure reading will effect the density value wouldnt it? If it does would the ecm map demand more fuel?
I get that longer that the vapor is in the line the more heat it could potentially absorb but I'm not planning on removing the fcv.
I'm not doing injection for power I don't even plan on running meth Im doing this for egt control. I've got a k type probe for this very perpose the kit is an aem and I'm planning on setting the end point to the max so that the injection is slow and I don't plan on injecting until I get some good egt data.

WWDiesel · **Posted:** Thu Dec 19, 2019 4:57 pm

Vmcrdrod wrote:

I get that it's dynamic but it's still above atmospheric so the BP would still increase. My point is its still a liquid and it would bring the MAP reading Temperature down that along with the pressure reading will effect the density value wouldnt it? If it does would the ecm map demand more fuel?
I get that longer that the vapor is in the line the more heat it could potentially absorb but I'm not planning on removing the fcv.
I'm not doing injection for power I don't even plan on running meth Im doing this for egt control. I've got a k type probe for this very perpose the kit is an aem and I'm planning on setting the end point to the max so that the injection is slow and I don't plan on injecting until I get some good egt data.

But it is not always above atmospheric pressure; I have a mechanical boost pressure gauge and unless you are accelerating or pulling a hill, the boost reads "0" psig. Way to much fluctuations in the pressure.
The spray is going to absorb heat no matter what and the longer it stays in the air stream the more heat it will absorb. That is why the closer to the cylinder inlets the better for the injection point. You don't have to remove the FCV, only the butterfly plate inside of it, 2 small torx screws removed and it slides out and blocking off the EGR keeps all the bad stuff and carbon crap along with the additional heat flux density it adds out of the intake.
If it negatively affects the density values of the intake, it could very well affect how the ECM handles the rate of injection, but that's over my head.
But if additional fuel is added with equal or less air density, the EGT's will certainly increase.

flash7210 · **Posted:** Fri Dec 20, 2019 2:49 pm

Vmcrdrod wrote:

I get that it's dynamic but it's still above atmospheric so the BP would still increase.

First off, water starts to vaporize well below its boiling point.
The principle behind water-methanol injection is evaporating cooling.
Its the same property that allows evaporative coolers (swamp coolers) and the sweat on your skin to keep you cool.

Now, you say you want to reduce EGT.
To do that you need to either reduce the fuel or increase the oxygen content of the incoming air.
Naturally, you want to stuff more air in the cylinders.
Increasing boost from the turbo will do this but the side effect is hotter, less dense, intake air.
Intercoolers can only do so much to help with this.
So you inject a fine liquid mist into the intake path. That will cool the intake air, making it more dense, also reducing intake air pressure, but will not increase air volume.
So you need the MAP sensor to detect this drop in air pressure, thus increasing the output pressure from the turbo, and increasing the air volume.
Yes, the MAP will sense the drop in intake air temperature and adjust fuel accordingly, but the increased volume of air will be more effective for what you want.

Also, water-methanol injection is not meant to be run all the time.
Only at WOT or at a prescribed boost level.

I recommend a 50/50 mix water-methanol.
The methanol has a lower BP and will vaporize easier.

And if you havent done so already, delete or block off the EGR valve.
The EGR gasses are reducing the oxygen content of the intake air.

Vmcrdrod · **Joined:** Wed Mar 22, 2017 9:21 am **Posts:** 33

Flash
(With the MAP in the intake) the cooling of the intake fools the computer to increase compressor output by the computer or decrease? Cooler air is generally more dense so it would make sense that if the MAP sensed a decrease in temp the ecm would call for less air (I don’t know this)
I’ve read that the gas guys are installing the nozzles after their air temp sensors which is what I’m doing but they don’t mention absolute TMAPs so that’s what I’m thinking will end up sending me in the opposite direction that I’m trying to go so so to speak.
If the injection is before the MAP the computer will adjust the compressor to reduce output I think and increase fuel. If it’s after the map the computer will not make any adjustment but the injection should yield cooler egt’s.
I’m not trying to argue but discuss so that I get this right.

flash7210 · **Posted:** Fri Dec 20, 2019 5:24 pm

Vmcrdrod wrote:

Flash
(With the MAP in the intake) the cooling of the intake fools the computer to increase compressor output by the computer or decrease? Cooler air is generally more dense so it would make sense that if the MAP sensed a decrease in temp the ecm would call for less air (I don’t know this)
I’ve read that the gas guys are installing the nozzles after their air temp sensors which is what I’m doing but they don’t mention absolute TMAPs so that’s what I’m thinking will end up sending me in the opposite direction that I’m trying to go so so to speak.
If the injection is before the MAP the computer will adjust the compressor to reduce output I think and increase fuel. If it’s after the map the computer will not make any adjustment but the injection should yield cooler egt’s.
I’m not trying to argue but discuss so that I get this right.

Compressed air, from the turbo, is hot.
Hot air expands, creates more pressure, and is less dense.
Cool air has less pressure and is more dense.

You want the MAP to see that pressure has been reduced so it will allow for more pressure from the turbo and therefore more air.
Yes, when the ECM sees lower IAT it will allow for more fuel but it does not reduce boost.
More boost = more air + cooler air = even more air.

IDK why that gassers are injecting water after IAT. Unlike diesels, gasoline engines have a fuel-air ratio that must be maintained. If a gas engine is getting cooler more dense air the ECM needs to see that so that AFR can be adjusted accordingly. Unless they are actually trying to run lean.

Back in the 90's the trick (hidden) with nitrous on fuel injected engines was to put a nitrous only nozzle (no gas) directly in front of the MAF sensor. The MAF sensed the cooler denser air and the ECM adjusted fuel accordingly.

MAP sensor relocation

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