Turbo boost, International 2.8L engine with VNT - Defender Source
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  #1  
Old September 13th, 2013, 06:52 AM
Santiago
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Turbo boost, International 2.8L engine with VNT

Hi there,

I have a question related to the turbo boost in Tdi engines.

For the first time since I have my Defender today I checked the turbo pressure of my VNT (TGV as it is known in Spanish) turbo.

The engine is an International Powerstroke 2.8L. It is installed in a year 2000 Defender 110 (former Td5). The engine has 130,000kms, it
has a moderately tweaked fuel pump (1.5 clockwise turns on the full power screw) , it runs well and has had no problems so far. I have
a small (same size as the original IC) uprated Allisport IC and new air hoses all around. I have an EGT gauge installed and with the current IP setup I have to control the throttle in order to keep the exhaust gas temperature below 700C.

The thing is that I have just found that my turbo is sending only 15 psi of air to the intake chamber (I am measuring the pressure
near the rear of the intake chamber or inatke manifold, don't know the exact name, where the 2.8 has a screw). According to the
International 2.8 L manual my turbo should deliver 1.2 bars of pressure (17.4 PSI), but apparently is is currently not achieving this
pressure.

When stepping hard on the throttle in fourth gear and going up a pretty significant slope, between 2500 and 3000 rpm (the conditions under
which I imagine that I should achieve full boost) I only get 15 constant PSI. Just after I step hard on the pedal it goes up to 16 or at
the best 17 psi but just for a fraction of a second (maybe for 1 sec?) and then it decreases to 15 PSI. I imagine that the 16 to 17 PSI
short peak in pressure must be the overboost stage that I have read about.

Given the description given above, do you agree that I should adjust (shorten) the screw in my VNT turbo in order to achieve the 17.4 psi
it should deliver? Or am I missing the point and the 17.4 psi (1.2 bars) that the engine's manual refers to is related to the overboost
pressure which I am almost achieving for a very short period of time? The manual states that 1.2 bars or 17.4 psi is actually the
"operation pressure" of the Garret GT 22 (56V) VNT turbo which I have.

My objective is to have the engine recieve the amount of air it is supposed to recieve (as from factory) or perhaps maybe a little bit more.

In this regard, any opinions as to Which would be the highest relatively safe operating pressure for my engine / turbo combination?
According to what I have read in this forum it appears that a maximum of 18 to 19 psi appears to be the consensus for the 300 Tdi engine.
What about the International 2.8 VNT turbo engine? The same should apply or slightly higher?

Perhaps Overlander and others have some experience to share related to the 2.8's turbo boost.


Thank you.
Regards,
Santiago
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  #2  
Old September 13th, 2013, 08:55 AM
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Not the same engine (I have 300tdi+VNT) but I am curious to know more as well. At no point have I ever gotten 18 -19 PSI. It may briefly dip into 15 PSI but it never stays there for long. I don't know if this is normal behavior as I just installed the boost gauge.
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Old September 13th, 2013, 08:59 AM
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Have either of you tried a boost leak test?
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Old September 13th, 2013, 09:02 AM
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How does that work?
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Old September 13th, 2013, 09:17 AM
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I've never done it on a Tdi or International, but on my S60R you pressurize the system through the turbo's air intake pipe and pump a smoke/vapor through the system. Follow where the smoke/vapor leaks and fix it. It's pretty common in the R.
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Old September 13th, 2013, 10:14 AM
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Santiago does the spec say manifold pressure or are they taking the 1.2 bar measurement @ the turbo ?

You loose several psi through all the plumbing etc

Boost pressure limits have more to do with blowing gaskets than anything else so don't see why the 2.8 would handle more than the 2.5
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Old September 13th, 2013, 11:12 AM
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Quote:
Originally Posted by Manimal View Post
Not the same engine (I have 300tdi+VNT) but I am curious to know more as well. At no point have I ever gotten 18 -19 PSI. It may briefly dip into 15 PSI but it never stays there for long. I don't know if this is normal behavior as I just installed the boost gauge.

Hello Manimal,
What is your max boost then? Above 15psi or below it?
Cheers,
Stgo

------ Follow up post added September 13th, 2013 12:14 PM ------

Quote:
Originally Posted by Uncle Douglas View Post
Santiago does the spec say manifold pressure or are they taking the 1.2 bar measurement @ the turbo ?

You loose several psi through all the plumbing etc

Boost pressure limits have more to do with blowing gaskets than anything else so don't see why the 2.8 would handle more than the 2.5
Uncle Douglas,
I understand they refer to 1.2 bars at the turbo exit. mmmmm it looks like the 2 psi I am missing are probably lost through the plumbing and IC then.....
If this is the case then maybe there is nothing wrong with my turbo.
Cheers,
Stgo
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Old September 13th, 2013, 12:04 PM
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My boost measuremebt is taken at the signal T. I have always been at 16 psi, hitting 18-19 momentarily in full throttle. Since your signal is at intake, you are probably spot on. I will move my signal to intake at some point.
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Old September 13th, 2013, 01:22 PM
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I would recommend changing the source for the wastegate pressure line to the intake manifold past the intercooler and its plumbing. This may bring the boost pressure you expect to see. I have set up many of the VGT turbos in that engine to boost 22psi.
The engine needs fuel to make boost also. So be certain the fuel delivery to the injection pump is in good order. You might adjust the injection pump somewhat before making an adjustment to the wastegate.
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Old September 13th, 2013, 02:28 PM
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Quote:
Originally Posted by pendy View Post
I have set up many of the VGT turbos in that engine to boost 22psi.
Would a 300 with the VGT also handle 22psi ?
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Old September 13th, 2013, 02:49 PM
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Quote:
Originally Posted by pendy View Post
I would recommend changing the source for the wastegate pressure line to the intake manifold past the intercooler and its plumbing. This may bring the boost pressure you expect to see. I have set up many of the VGT turbos in that engine to boost 22psi.
The engine needs fuel to make boost also. So be certain the fuel delivery to the injection pump is in good order. You might adjust the injection pump somewhat before making an adjustment to the wastegate.

Thank you Pendy. How were the results of 22 psi boost in those turbo's? Are the 300 Tdi's and the 2.8's capable of dealing those kinds of pressures without blowing a cilinder head gasket too soon?

Cheers,
Stgo
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Old September 13th, 2013, 03:03 PM
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In my experience, we've always run MAP sensors or gauges directly from the intake plenum. The momentary 18-19 psi some of you are seeing is called a boost spike where the wastegate doesn't open quickly enough or fins of the VNT/VGT turbo can't slow the turbine wheel in time to reach the preset boost limit. Usually, in a standard turbo configuration this means the wastegate is undersized or the spring tension is too high. In some cases it helps with acceleration as you don't lose all of the turbine shaft momentum between shifts.

If you are already having to throttle the accelerator to keep your EGT low you need to increase the fuel input to the engine. Too much boost and not enough fuel causes a lean condition which leads to high EGT and eventually melted pistons or worse. For this reason when tuning, it's always better to richen up the fuel mixture before turning the boost up. An EGT gauge is very helpful, but a wideband would be a better aid. I know on my Eclipse, I tune relatively conservative, so it's not uncommon for my datalog to read 35+ psi with my AFR in the 11's.

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Old September 13th, 2013, 04:39 PM
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Quote:
Originally Posted by SafariHP View Post
In my experience, we've always run MAP sensors or gauges directly from the intake plenum. The momentary 18-19 psi some of you are seeing is called a boost spike where the wastegate doesn't open quickly enough or fins of the VNT/VGT turbo can't slow the turbine wheel in time to reach the preset boost limit. Usually, in a standard turbo configuration this means the wastegate is undersized or the spring tension is too high. In some cases it helps with acceleration as you don't lose all of the turbine shaft momentum between shifts.

If you are already having to throttle the accelerator to keep your EGT low you need to increase the fuel input to the engine. Too much boost and not enough fuel causes a lean condition which leads to high EGT and eventually melted pistons or worse. For this reason when tuning, it's always better to richen up the fuel mixture before turning the boost up. An EGT gauge is very helpful, but a wideband would be a better aid. I know on my Eclipse, I tune relatively conservative, so it's not uncommon for my datalog to read 35+ psi with my AFR in the 11's.

Scott
Hello Safari,
Are you talking about Diesels? I understood too much air did not lead to high EGT's in diesels. I understood that the opposite was the case (that too much fuel in diesels translated into high EGT's). Sorry if I am messing things up. Just want to get it clear.
Stgo
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Old September 13th, 2013, 04:54 PM
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My experience is based on gasoline or E85 powered engines. You are correct about the diesel side of things. This is a very good article to read regarding those:

http://www.dieselpowermag.com/tech/1...t/viewall.html

Scott
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Old September 13th, 2013, 05:00 PM
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I do not think the 300 tdi is built to take tuning on that level. The powerstroke engine is a much stonger unit in many respects.

Quote:
Originally Posted by Trey C View Post
Would a 300 with the VGT also handle 22psi ?
Thank you Pendy. How were the results of 22 psi boost in those turbo's? Are the 300 Tdi's and the 2.8's capable of dealing those kinds of pressures without blowing a cilinder head gasket too soon?

Cheers,
Stgo
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Old September 14th, 2013, 05:15 PM
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Just got some 300tdi VNT turbo kits. Will be installing one shortly... Can't wait
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Old September 14th, 2013, 05:23 PM
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Old September 14th, 2013, 06:31 PM
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Originally Posted by TDI Guy View Post
Attachment 79868

Just got some 300tdi VNT turbo kits. Will be installing one shortly... Can't wait
You have these for sale? Can you pm me a price if so? Thanks
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Old September 30th, 2013, 08:21 PM
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Just a brief update of the developments: when I took out the actuator rod (without taking out the turbo) to shorten it a little bit in order to give the engine a little more boost I realized that the vane moving lever was not moving freely. The cause was soot inside the turbo which was jamming the movement of the vanes. The cure was taking the turbo out (I did it at home) and having it properly cleaned by a specialised turbo shop. 90U$ later I was given my shiny turbo back. The turbo guy said my turbo is in perfect conditions, almost like new, it was just full of soot inside (blame the full power screw, not me..........).
I reinstalled my turbo and adjusted the length of the actuator rod almost as it was originally (maybe just only 1mm shorter). When I gave it a try everything was working almost the same as it was before, with max boost at around 15 psi.
After a few messages with Pendy I decided to follow his advice and connected the airline which controls the actuator directly to the intake manifold. Result: NICE, noticeable change. Immediate and clear reduction in EGT's (by more or less 100 to 120F driving around town), max boost increased to 17-18 psi and a much more stable (less oscilation) reading in the boost gauge. Perhaps a tiny bit more power as well.
Bottomline is I am very happy with the change. I find it great given how easy and cheap it is to do. Especially when compared to the PITA it is to shorten the length of the actuator rod in the 2.8 TGV engine without taking the turbo out.

So my conclusion is that my 2.8 TGV engine with a tweaked IP (1 full clockwise turn in the full power screw and a little rotation of the diaphragm) and an uprated but standard size IC (Allisport) was needing a little bit more air. The change suggested by Pendy gave the engine the 1.2 bars (17.4 psi) of boost that the turbo delivers and it made a significant change.

Maybe there is a little space for little bit more boost but the engine feels with excelent power now and EGT's seem to be improved (need to do some open road testing still) so I plan to leave it as it is for some time.

Cheers,
Stgo
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Old September 30th, 2013, 08:40 PM
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report on mpg when you have the numbers in! I'm at + .25 on the power screw and 90deg on the diaphragm right now. going to add another .25 very soon and move the boost signal to the intake as well.
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