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:

[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"

[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"

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.

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.

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.