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JP ***
Joined: 31 Dec 2006 Posts: 157 Location: Christchuch, NZ
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Posted: Tue Jun 02, 2015 5:10 Post subject: Low boost reading |
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I've just installed an Auberins dual boost/EGT gauge, and calibrated the sensors to give 0psi when in the ACC possition. MAX boost is 9psi. It is plumbed into the EGR blanking plate on the intercooler.
12-13psi is normal, but is usually taken pre-intercooler. Could this be why my boost reading is low? _________________ 93 3.1 LWB Auto |
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Posted: Tue Jun 02, 2015 5:10 Post subject: Google Ads keep this community free to join! |
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Red Robbo Lifetime member
Joined: 17 Feb 2008 Posts: 4129 Location: Where ever I happen to be in my imagination but mainly Far East Sussex
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Posted: Tue Jun 02, 2015 10:41 Post subject: |
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Depending on the ambient temp I would say that that is about right.....Ive run at 16psi showing 11 at manifold.....so intercooler is doing its job
I see in another post your exhaust temperatures.......way too high !...where is the sensor ?. The calibration on it.....was that to just set the zero or does that also alter the span ? _________________ Khotso........... |
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Red Robbo Lifetime member
Joined: 17 Feb 2008 Posts: 4129 Location: Where ever I happen to be in my imagination but mainly Far East Sussex
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Posted: Tue Jun 02, 2015 10:42 Post subject: |
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And amount of air flow through I/C.....Speed dependant. _________________ Khotso........... |
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Gribble *******
Joined: 11 Oct 2007 Posts: 8448 Location: Holset H221W
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Posted: Tue Jun 02, 2015 21:41 Post subject: |
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With due respect to me learned friend if you got a pressure drop on yer intercooler then maybe its restricting the airflow ?
If the I'coolers matched to the turbo and engine then there should be no pressure differential across it since a restriction to airflow would cause a temperature rise .
According to the Forge tech pages if the intercooler can get the post turbo inlet air temps down to the ambient air temp or lower on intercooler exit its efficiency can be rated as x/% and this will be reflected in boost figures in colder air in cubic cc's / density as a ratio.
Most mass produced intercoolers do the minimum needed to make the makers stated hp the green ovals 200 &300 being big offenders here .
Whats the Auberins say at idle and going downhill with your foot off the skinny pedal ? it must show some bit of vac for sure . _________________ 2 New Troopers ! |
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JP ***
Joined: 31 Dec 2006 Posts: 157 Location: Christchuch, NZ
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Posted: Tue Jun 02, 2015 23:19 Post subject: |
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Red Robbo wrote: |
Depending on the ambient temp I would say that that is about right.....Ive run at 16psi showing 11 at manifold.....so intercooler is doing its job
I see in another post your exhaust temperatures.......way too high !...where is the sensor ?. The calibration on it.....was that to just set the zero or does that also alter the span ? |
Sensor is pre-turbo about 40mm from the turbo/manifold gasket. I'll post some pics in my readers ride post soon.
In a related question. If my boost gauge is showing 9psi and I up the boost to say 16psi, are you suggesting the turbo would be producing closer to 20psi?
If you go to the Auberins page you can click on the manuals at the bottom of the page for setting up the sensors. Mine has been changed to degress celcius. _________________ 93 3.1 LWB Auto |
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Red Robbo Lifetime member
Joined: 17 Feb 2008 Posts: 4129 Location: Where ever I happen to be in my imagination but mainly Far East Sussex
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Posted: Wed Jun 03, 2015 9:41 Post subject: |
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Gribble wrote: |
With due respect to me learned friend if you got a pressure drop on yer intercooler then maybe its restricting the airflow ?
If the I'coolers matched to the turbo and engine then there should be no pressure differential across it since a restriction to airflow would cause a temperature rise .
According to the Forge tech pages if the intercooler can get the post turbo inlet air temps down to the ambient air temp or lower on intercooler exit its efficiency can be rated as x/% and this will be reflected in boost figures in colder air in cubic cc's / density as a ratio.
Most mass produced intercoolers do the minimum needed to make the makers stated hp the green ovals 200 &300 being big offenders here .
Whats the Auberins say at idle and going downhill with your foot off the skinny pedal ? it must show some bit of vac for sure . |
I would agree to a certain extent, but consider the following.
Anything but a straight pipe is going to restrict airflow to a greater or lesser degree, a FMI because of its size can be designed differently to a TMI as room is not such a restraint and can be made more efficient.
The 3.1 I/C is a very compact unit and I would suggest quite restrictive, as compared with the 3.0 I/C.
The figure I stated is 16/11 psi is with the 3.1 I/C. I did do the same test with a 3.0 I/C but can't remember the figures
I'll rig another gauge up and redo the test and post it up.
Perhaps the OP could repost his temps and pressures when he's had the pump reworked and back to stock. _________________ Khotso........... |
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Rhanagar Lifetime member
Joined: 12 Jan 2010 Posts: 4861 Location: Preston, Lancs.
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Posted: Wed Jun 03, 2015 10:17 Post subject: |
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To sort of qualify what Robbo says the Frontera 2.8 uses a FMIC. That along with the later 3.1 turbo the chaps at VX managed to get performance figures almost the same as the 3.1 in the Trooper. I have always maintained it was due to the better airflow and also the more efficient cooling of the larger FMIC _________________ 1990 Isuzu Bighorn LWB Mk.I 2.8TD Manual Lotus Edition
1994 Isuzu Bighorn LWB Mk.II 3.1TD Auto Lotus Edition
Deceased
1994 Isuzu Bighorn LWB Mk.II 3.1TD Auto LS
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Red Robbo Lifetime member
Joined: 17 Feb 2008 Posts: 4129 Location: Where ever I happen to be in my imagination but mainly Far East Sussex
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Posted: Wed Jun 03, 2015 12:19 Post subject: |
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I stand corrected....
My humble apologies, especially to the OP, for erroneous information.
Running at 12, 16 & 20 psi measured at the turbo there is no significant pressure drop across the I/C.
So in answer to the original question...No that's not right.Possibilities are choked I/C, throttle flap, air leak.
I do however stand by what I said about exhaust temps...I take it you used the EGR takeoff off the exhaust manifold ?
Now where did I get my original figures from ? Gawd knows Either something completely different or badly fitted gauge
It could however just be old(er) age
Once again aplogies and hope this sets it straight _________________ Khotso........... |
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JP ***
Joined: 31 Dec 2006 Posts: 157 Location: Christchuch, NZ
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Posted: Wed Jun 03, 2015 12:59 Post subject: |
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I'm going to check the intercooler. Previous owner had not cleaned the intercooler once the turbo had blown - I soaked it in petrol and there looked like bits of rubber being flushed out.
I think the intercooler is blocked! Idle reads 0pi (Diesels by nature do not create much VAC) and 180C, 50kph is 4-5psi and 450ish C, 100kph is 9psi and 750-850C, acceleration is very slow compared to my previous 3.1 _________________ 93 3.1 LWB Auto |
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JP ***
Joined: 31 Dec 2006 Posts: 157 Location: Christchuch, NZ
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Posted: Wed Jun 03, 2015 13:03 Post subject: |
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I have mounted/tapped the EGT sensor in the collector about 40mm in front of where the turbo gasket sits - not in the EGR blanking plate. Temps are worrying _________________ 93 3.1 LWB Auto |
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Gribble *******
Joined: 11 Oct 2007 Posts: 8448 Location: Holset H221W
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Posted: Wed Jun 03, 2015 13:56 Post subject: |
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Bypass the intercooler with a length of pipe and run the tests again ? _________________ 2 New Troopers ! |
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Gribble *******
Joined: 11 Oct 2007 Posts: 8448 Location: Holset H221W
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Posted: Wed Jun 03, 2015 19:28 Post subject: |
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Only chart I've got for an Isuzu 4 pot but it gives you some idea of whats going on .
_________________ 2 New Troopers ! |
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JP ***
Joined: 31 Dec 2006 Posts: 157 Location: Christchuch, NZ
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Posted: Wed Jun 03, 2015 23:16 Post subject: |
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Gribble wrote: |
Bypass the intercooler with a length of pipe and run the tests again ? |
I'm not sure I'm confident enough to try that yet......The EGT temps are already high and if the intercooler is not at fault I could be asking for trouble? _________________ 93 3.1 LWB Auto |
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Gribble *******
Joined: 11 Oct 2007 Posts: 8448 Location: Holset H221W
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Posted: Thu Jun 04, 2015 8:51 Post subject: |
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With deference to the previous posters I would not say your EGT readings are high,a little Internet research will bear this out. _________________ 2 New Troopers ! |
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Gribble *******
Joined: 11 Oct 2007 Posts: 8448 Location: Holset H221W
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Posted: Thu Jun 04, 2015 8:52 Post subject: |
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Is the turbo in good condition ? _________________ 2 New Troopers ! |
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