Checking Drive Pressure on a Holset Powered TIII

[DoubleD]

I have a ported exhaust manifold on the way from LWP/ FWD. I want to add a 1/4 npt hole into my manifold so i can get a pressure reading out of it. I want to see what the drive pressure on my set up is. Ported T3 manifold, HE341, Jackson's 3" Down pipe, 3" Straight back exhaust. I want to see if my exhuast is free flowing enough or a 4" downpipe and cutout are in my future.
Where should I put my fitting? I have a 1/4 NPT to 1/4 Stainless Steel compression fitting on on the way so I need to tap a 1/4 npt hole into my manifold.

[zin]

1/4NPT is pretty big! That's a 1/2" hole, so if you have to use something that big, your choices will be limited to wherever you can fit the thing, I'd suggest using 1/8NPT instead, either way, I'd probably try to mount it close to the manifold/turbo flange.

Mike

[Kryp2nitE]

Cindy did my drive pressure tap and EGT tap:
http://img.photobucket.com/albums/v308/Kryp2nitE/Spirit%20RT/cc719dd0-da7c-446d-aaa5-3f9466964ad5_zpstn0sbrdn.jpg (http://smg.photobucket.com/user/Kryp2nitE/media/Spirit%20RT/cc719dd0-da7c-446d-aaa5-3f9466964ad5_zpstn0sbrdn.jpg.html)

[5DIGITS]

I have a ported exhaust manifold on the way from LWP/ FWD. I want to add a 1/4 npt hole into my manifold so i can get a pressure reading out of it. I want to see what the drive pressure on my set up is. Ported T3 manifold, HE341, Jackson's 3" Down pipe, 3" Straight back exhaust. I want to see if my exhuast is free flowing enough or a 4" downpipe and cutout are in my future.
Where should I put my fitting? I have a 1/4 NPT to 1/4 Stainless Steel compression fitting on on the way so I need to tap a 1/4 npt hole into my manifold.

The thickest material near the turbine housing convergence point will yield the best signal without the influence of individual cylinder pulsations.

[supershadow]

I used 1/8"npt to 1/8" tube. The longer you make the tube the less fluctuation you will see. This is how I made mine almost 8' and only took up a few inches. Plus everyone asked me "What is that spring for"http://i1116.photobucket.com/albums/k580/ryan_buechel/0BC45945-F3F2-4EE0-B5B5-051C7E429609.jpg

[Pat]

I used 1/8"npt to 1/8" tube. The longer you make the tube the less fluctuation you will see. This is how I made mine almost 8' and only took up a few inches. Plus everyone asked me "What is that spring for"http://i1116.photobucket.com/albums/k580/ryan_buechel/0BC45945-F3F2-4EE0-B5B5-051C7E429609.jpg

What were your results?

[zin]

Ken, can you shed some light on how to install a port that will read accurately if installed in the same fashion from turbo to turbo? I'm concerned about dynamic effects of high-speed gasses creating low or high pressure. In a one-off/one-time, A to B type of test, it might not matter, but I'd like to know that info attained in the same fashion would be comparable, even on different applications, say TII vs TIII, or a TU log, etc.

Pitot tubes don't seem like a good fit here. :p

Mike

[5DIGITS]

Ken, can you shed some light on how to install a port that will read accurately if installed in the same fashion from turbo to turbo? I'm concerned about dynamic effects of high-speed gasses creating low or high pressure. In a one-off/one-time, A to B type of test, it might not matter, but I'd like to know that info attained in the same fashion would be comparable, even on different applications, say TII vs TIII, or a TU log, etc.

Pitot tubes don't seem like a good fit here. :p

Mike

The key is sensor heat isolation without generating too much signal delay.
In most test applications, a sample tube 24" in length and 3/16" ID will allow a sensor to live and have good response.
"Ametek" and "transducers direct" sensors work well in these environments while MAP sensors can even be used if heat isolation is supported, to be budget wise.
I favor the turbine housing for these measurements, both EGT and pressure, as its the critical point of pressure accumulation while accounting for all cylinder pulses collectively.
Taps in this location will minimize individual cylinder signal pulses and provide EGT measurement relative to the exhaust energy at to the second engine that drives these cars - the turbine engine.
The highest 'reasonable' EGT at this point will yield the lowest exhaust back pressure due to the focus on gas expansion where it counts.
Why? Increased gas expansion at the turbine increases turbine efficiency and this excites the turbine wheel which causes the WG to open farther for the same boost level.
An additional upstream or downstream EGT probe will also aid in identifying where the flame front truly exists and whether enrichment or enleanment is needed.

I hope this helps.

[glhs875]

The key is sensor heat isolation without generating too much signal delay.
In most test applications, a sample tube 24" in length and 3/16" ID will allow a sensor to live and have good response.
"Ametek" and "transducers direct" sensors work well in these environments while MAP sensors can even be used if heat isolation is supported, to be budget wise.
I favor the turbine housing for these measurements, both EGT and pressure, as its the critical point of pressure accumulation while accounting for all cylinder pulses collectively.
Taps in this location will minimize individual cylinder signal pulses and provide EGT measurement relative to the exhaust energy at to the second engine that drives these cars - the turbine engine.
The highest 'reasonable' EGT at this point will yield the lowest exhaust back pressure due to the focus on gas expansion where it counts.
Why? Increased gas expansion at the turbine increases turbine efficiency and this excites the turbine wheel which causes the WG to open farther for the same boost level.
An additional upstream or downstream EGT probe will also aid in identifying where the flame front truly exists and whether enrichment or enleanment is needed.

I hope this helps.

Good info!

[zin]

Thanks Ken, it really does help.

Mike

[Force Fed Mopar]

The key is sensor heat isolation without generating too much signal delay.
In most test applications, a sample tube 24" in length and 3/16" ID will allow a sensor to live and have good response.
"Ametek" and "transducers direct" sensors work well in these environments while MAP sensors can even be used if heat isolation is supported, to be budget wise.
I favor the turbine housing for these measurements, both EGT and pressure, as its the critical point of pressure accumulation while accounting for all cylinder pulses collectively.
Taps in this location will minimize individual cylinder signal pulses and provide EGT measurement relative to the exhaust energy at to the second engine that drives these cars - the turbine engine.
The highest 'reasonable' EGT at this point will yield the lowest exhaust back pressure due to the focus on gas expansion where it counts.
Why? Increased gas expansion at the turbine increases turbine efficiency and this excites the turbine wheel which causes the WG to open farther for the same boost level.
An additional upstream or downstream EGT probe will also aid in identifying where the flame front truly exists and whether enrichment or enleanment is needed.

I hope this helps.

Where would a good place be for said downstream probe? Still in the turbine housing, or in the swingvalve or downpipe?

[Shadow]

IF you're going to tap the turbine side, just be careful not to go too far into the scroll, it will give a false higher reading. Also, IF you tap the mani side, you can change turbos in the future and never have to screw with it again.............

[5DIGITS]

Where would a good place be for said downstream probe? Still in the turbine housing, or in the swingvalve or downpipe?

Avoid any measurements after the elbow/exhaust connection.
Under elevated boost levels the seal can relieve pressure and allow air intrusion that can skew both A/F and pressure readings.
Auxiliary probes/sensors near the O2 bosses on standard elbows and upstream from the exhaust pipe connection will work best.

[Reaper1]

Which seal can allow air intrusion? How? The exhaust environment is hot and under more pressure than ambient, so if anything I would think that exhaust would escape and the readings would be off because of that.

[5DIGITS]

Which seal can allow air intrusion? How? The exhaust environment is hot and under more pressure than ambient, so if anything I would think that exhaust would escape and the readings would be off because of that.

I agree with your logic but due to the exhaust gas velocities it's been proven that instrumentation O2 readings can read lean conditions when the exhaust joints separate or leak.
You'd think (I would too) that this would not be possible but it a consideration during emission testing and gas sampling and why exhaust joint sealants are used during testing.

[Force Fed Mopar]

Interesting. You are talking about the donut gasket where the downpipe bolts to the swingvalve right?

[5DIGITS]

Interesting. You are talking about the donut gasket where the downpipe bolts to the swingvalve right?

Correct.
Considering the sealing surfaces, movement during the drive cycle, even when the seal has not been pushed off due to back pressure, the potential for intrusion exists which results in disrupted measurements.

[Reaper1]

I suppose if you look really close at the joint when it starts to fail you might see some strange things happen around the boundary layer.

I have heard of O2's reading lean after joints, but I always thought it was just because not all of the gasses were passing the sensor.

So, here's a great question...most people I think are running wide band sensors after the donut because the instructions say that the sensors need to be a certain distance from the turbo for longevity (makes sense). What would be the best course of action here in that situation do you think, Ken?

[5DIGITS]

I suppose if you look really close at the joint when it starts to fail you might see some strange things happen around the boundary layer.

I have heard of O2's reading lean after joints, but I always thought it was just because not all of the gasses were passing the sensor.

So, here's a great question...most people I think are running wide band sensors after the donut because the instructions say that the sensors need to be a certain distance from the turbo for longevity (makes sense). What would be the best course of action here in that situation do you think, Ken?

The first item of concern would be is an oxygen sensor that cant handle the heat.
I have never done this and have always installed an extra O2 bung adjacent to the existing sensor to avoid this very issue.
If an understanding of potential signal error is acceptable, then the sensor could be placed anywhere within the exhaust stream.
Although, the further the sensor is placed from the engine/turbo the greater the chances of transfer delays especially when transient fueling is being monitored, for calibration purposes.

I'd suggest mounting a temperature limited sensor within the elbow during the calibration process and subsequently moving it downstream when the cal is completed, only as reference thereafter.

[Force Fed Mopar]

I think Shelgame is running a wideband in the stock O2 bung without any issue so far. I've been thinking of trying the same since he now has Turbonator capable of computing the narrowband signal for the computer from the WB reading.

[Reaper1]

The interesting thing is the OEM's use WB sensors very close to turbos and catalytic converters, so why would the same sensor be limited in an aftermarket application? Using that reasoning I understand why people look at those instructions and go"....pshh...whatever" and just put them in the stock location.

[turbovanman²]

The interesting thing is the OEM's use WB sensors very close to turbos and catalytic converters, so why would the same sensor be limited in an aftermarket application? Using that reasoning I understand why people look at those instructions and go"....pshh...whatever" and just put them in the stock location.

Because OE sensors are built to a different standard knowing they have to last at least 60-100,000 miles. The WB sensors we use are cheap and old technology. Price out a newer OE wideband, :confused:

Most of us on a diesel forum I am on check drive pressures, my van is currently 1.5:1 around town and 2:1 towing and at WOT. Going to drop my exhaust and see how much that changes it, if a lot, then its going 4".

[DoubleD]

Back to my original question,
Does anyone have a picture of their fitting installed into the stock exhaust manifold so I can see where to drill and tap mine?

[DoubleD]

I'm thinking of installing it in the boss, on cylinder 2, is this a good location?
http://images.tapatalk-cdn.com/15/05/16/467fa1589b52b3ef6fc4e8455204476b.jpg

[turbovanman²]

YOu want it as close to the 4 bolt flange as possible.

[rx2mazda]

Put it in that "Y" right before the flange.

[acannell]

Drive pressure doesnt rise any faster than boost pressure, no reason to be concerned with "signal delay". Its not a spike you are looking at, its a very slow signal with a time constant of seconds.

Your pressure gauge is not going to show cylinder pulsations regardless of where you put the pressure sensor. I used an instrumentation grade sensor with a khz bandwidth sampled digitally and saw no pulsations. Even if you could observe pulsations, they overall signal will be dominated by the average pressure in the manifold. It wont make your measurement any less useful.

Why the desire to measure pressure pre-turbo, instead of pre-exhaust manifold? Isnt the idea here to get an overall picture of how much pressure the exhaust valve is seeing, and therefore the closer to the head the better?

http://www.turbododge.com/forums/f4/f279/728610-1990-dodge-daytona-es-turbo-2-a.html#post3571297

http://i242.photobucket.com/albums/ff197/acannell/20141120_160513_zpspxq3335k.jpg
http://i242.photobucket.com/albums/ff197/acannell/20141120_160500_zpsbyezwmfr.jpg
http://i242.photobucket.com/albums/ff197/acannell/20141120_160454_zpspxlt0yze.jpg

[turbovanman²]

Why the desire to measure pressure pre-turbo, instead of pre-exhaust manifold? Isnt the idea here to get an overall picture of how much pressure the exhaust valve is seeing, and therefore the closer to the head the better?



I am assuming he wants to check drive pressure in the manifold, hence why he posted a pic of the exhaust manifold. Its not so much the pressure the exhaust valve is seeing but how good the turbo drive pressure is, as the higher it is, the less efficient the engine is.

[Vigo]

The only reason 'drive pressure' matters is because of its effect on pumping losses and exhaust valve sealing. I think Acannell is correct although i dont think the location matters much within the few inches worth of options that we realistically have.

[DoubleD]

The reason I don't want to put it in the y is the material is pretty thin right there. The boss is flat and has some thickness. I will look at putting it in the turbo scroll, that's probably the best spot and the thickest point. I'll look tonight.

[DoubleD]

Here's where I put it.
http://i84.photobucket.com/albums/k6/brmsnowboarder/IROC%20RT/D04C1C75-CD03-41C5-8835-16532D1638F1_zps4b1zypoq.jpg (http://s84.photobucket.com/user/brmsnowboarder/media/IROC%20RT/D04C1C75-CD03-41C5-8835-16532D1638F1_zps4b1zypoq.jpg.html)

[turbovanman²]

That will work. :thumb: