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Working on installing gauges. My boost gauge has an electric sensor, instead of running plastic tubing to the gauge.
Instead of cobbling together a brass "T" with adapters and barbs to go in the MAP sensor hose, what about drilling and tapping the front side (away from hotside of turbo) of Y pipe for sensor? Would seem to be pretty straight forward, and look better than a brass T with adapters.
On the back side of the stock y-pipe there is a flat spot that is easy to mount the sensor on, just put some shielding on your wires to protect them from some turbo heat.
And be careful as well to not over thread, its a pipe thread, so you wanna not drive that tap in to far.
If you got a welder, then, even easier. just put some more metal on there to tap.
it's been tested by somebody a long while ago.
Can be 3 to 5 lbs low in the map line.
Plus you're only reading the passenger head pressure at that point too.
Hmm I might have to take the Pepsi challenge on that one. I've tuned a number of gas cars that use very long vacuum lines to a map sensor that lives inside the ECU casing in the car. There's never been an appreciable difference in pressure or signal lag with even 10 ft of line compared to the manifold directly.
The factory map signal is on the passenger head but the passenger plenum, the driver plenum, and the y-pipe all create one single plenum volume. Pressure changes in that volume travel at the speed of sound which is pretty quick.
I didn't see the test and won't dispute that they saw something but I'm not sure that the problem wasn't something else.
If I can find another y pipe cheap then I'll do some testing.
Hmm I might have to take the Pepsi challenge on that one. I've tuned a number of gas cars that use very long vacuum lines to a map sensor that lives inside the ECU casing in the car. There's never been an appreciable difference in pressure or signal lag with even 10 ft of line compared to the manifold directly.
The factory map signal is on the passenger head but the passenger plenum, the driver plenum, and the y-pipe all create one single plenum volume. Pressure changes in that volume travel at the speed of sound which is pretty quick.
I didn't see the test and won't dispute that they saw something but I'm not sure that the problem wasn't something else.
If I can find another y pipe cheap then I'll do some testing.
A lot of guys run it T-d into their Map line.
But, were talking Diesels vs Gas as well.
Map systems don't quite work the same.
You can clearly see the MAP system not reading the same on our trucks if you have a scanner as well, cause you can read the map sensor.
Pressure is pressure, yes, but volume is important also.
You're better off reading it in the y-pipe where you're getting pressure and volume, vs cutting half the volume, then shoving half that volume down a 1/8th inch tube that will flex based on how many PSI you're pushing, which will then also give you a false signal.
While the map sensor is important in our trucks, it doesn't seem to have to be very accurate, because as I understand it, it's more looking for "overboost" more than any other information on fuel to air.
Which is why you had to use a boost fooler with a lot of the older tune styles, though I think you can tune it out on the hydra system.
First off, I decided to put the sensor in a T in the MAP line. The Y is not very thick material, and could be difficult to get a good pipe thread seal. I just got a 1/8" NPT T with two 1/8" to hose barbs. Doesn't look too cobbled together...
Second, I doubt this "reads low". I saw 15 psi on gauge on a short romp.
The way I understand PIDS, when read with a scan tool, is that there is a math conversion from what the PCM value is to make it make sense on a "gauge". This math conversion only happens in the app, as Ford referenced the value as the PCM sees it.
So...just because you see a "low PSI reading" on a scan tool, does not mean you will get a low reading with an actual sensor in the MAP line. Pressure is pressure.
Holley uses a MAP sensor on their Terminator X product line, built in to the "brain" box you mount in the car. Works well for boosted or NA applications. I doubt they would use this method if it lead to low boost readings...
First off, I decided to put the sensor in a T in the MAP line. The Y is not very thick material, and could be difficult to get a good pipe thread seal. I just got a 1/8" NPT T with two 1/8" to hose barbs. Doesn't look too cobbled together...
Second, I doubt this "reads low". I saw 15 psi on gauge on a short romp.
The way I understand PIDS, when read with a scan tool, is that there is a math conversion from what the PCM value is to make it make sense on a "gauge". This math conversion only happens in the app, as Ford referenced the value as the PCM sees it.
So...just because you see a "low PSI reading" on a scan tool, does not mean you will get a low reading with an actual sensor in the MAP line. Pressure is pressure.
Holley uses a MAP sensor on their Terminator X product line, built in to the "brain" box you mount in the car. Works well for boosted or NA applications. I doubt they would use this method if it lead to low boost readings...
IMHO.
You asked for help.
I gave the consensus over years of discussion and trial from FTE forum 170. =)
Honestly I don’t doubt it’ll read a little low. Pressure is pressure but getting that pressure through a hole 1/4 inch compared to 2 inch is much easier obviously. But if anything your gauge will only read a few psi less than is in the intake. It Don’t make it run any different whatever your reading is as long as there’s no leaks
Nah the 1/4 inch doesn't hurt anything but I'm pretty sure it's 1/8 or 3/16 so even smaller. Still there isn't any flow, that's where the size would matter. The MAP line is dead-headed, almost no flow and just pressure. Pressure moves at the speed of sound, as sound is pressure. The equivalent arrangement has been used to greater extremes in the Holley EFI systems as cbrown pointed out, and also in Megasquirt EFI systems and their variants. I understand it's long-held forum wisdom so I won't discount it out of hand, but I'm keeping an eye out for a spare Y pipe. Once I get one I am going to add a bung and another pressure sensor. I'm going to log them both, then I'm going to swap sensor positions and do it again to account for any sensor and wiring tolerances. I have $20 on anybody who wants to take it the bet that after the correcting for variations in sensors and wiring they track each-other within 1% and any lag on the sensor in the map line is less than a millisecond.
