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Low boost reading

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JP
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PostPosted: Tue Jun 02, 2015 5:10    Post subject: Low boost reading Reply with quote

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?
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Red Robbo
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PostPosted: Tue Jun 02, 2015 10:41    Post subject: Reply with quote

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  Smile
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 ?
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PostPosted: Tue Jun 02, 2015 10:42    Post subject: Reply with quote

And amount of air flow through I/C.....Speed dependant.
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Gribble
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PostPosted: Tue Jun 02, 2015 21:41    Post subject: Reply with quote

With  due respect to me learned friend  Smile  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 .
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JP
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PostPosted: Tue Jun 02, 2015 23:19    Post subject: Reply with quote

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  Smile
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.
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PostPosted: Wed Jun 03, 2015 9:41    Post subject: Reply with quote

Gribble wrote:
With  due respect to me learned friend  Smile  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  Embarassed
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.
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PostPosted: Wed Jun 03, 2015 10:17    Post subject: Reply with quote

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
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Red Robbo
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PostPosted: Wed Jun 03, 2015 12:19    Post subject: Reply with quote

I stand corrected.... Embarassed  Embarassed  Embarassed
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  Rolling Eyes Either something completely different or badly fitted gauge  dontknow
It could however just be old(er) age  Laughing  Laughing  Laughing

Once again aplogies and hope this sets it straight    Smile
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JP
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PostPosted: Wed Jun 03, 2015 12:59    Post subject: Reply with quote

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
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PostPosted: Wed Jun 03, 2015 13:03    Post subject: Reply with quote

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  Shocked
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PostPosted: Wed Jun 03, 2015 13:56    Post subject: Reply with quote

Bypass the intercooler with a length  of pipe and run the tests again ?
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PostPosted: Wed Jun 03, 2015 19:28    Post subject: Reply with quote

Only chart I've got for an Isuzu 4 pot but it gives you some idea of whats going on .


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PostPosted: Wed Jun 03, 2015 23:16    Post subject: Reply with quote

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?
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PostPosted: Thu Jun 04, 2015 8:51    Post subject: Reply with quote

With deference to the previous posters I would not say your EGT readings are high,a little Internet research will bear this out.
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PostPosted: Thu Jun 04, 2015 8:52    Post subject: Reply with quote

Is the turbo in good condition ?
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