300tdi's with boost gauge fitted

[weeds]

i have never driven a car with a boost gauge before

plumbed it all up yesterday.....not so straight forward as i first thought

i noticed that it doesn't take too much right foot for the gauge to whip around to 15/16psi

is it because of the small capicity of the engine or turbo that makes it spool up so quick

had a quick run on the hi-way tonight..........sits around 10psi @ 100km does this sound about right, any small high and she get up to 14/15psi

i plan to make an adaptor up so i can can compare manifold pressure

[LOVEMYRANGIE]

Where did you connect the pressure line to?
Usual spot is to the plenum. Connecting it to the compressor outlet will tell you what the turbo itself is doing, but not actually what is in your manifold plenum which is more accurate of what is being fed into the intakes.

[weeds]

at this stage its at the turbo

from what i have read on here, fueling is controlled by the turbo pressure and pressure drop over the intercooler can be measured at the manifold

i figure so long as i know what the pressure drop is its probably best to have it connect att he turbo most of the time so that i get an indication of fuel

happy to listen and learn as i know bugger all about boost/fuel/connection points

[justinc]

Hi Kelvin,

At the manifold is better, as it is a true indication of the ACTUAL pressure available. Even better again is blocking off the fitting completely at the turbo, and using actual manifold pressure to control fuelling and wastegate operation by connecting it all up to the manifold itself. There is a handy plug already in the manifold that you can unscrew and either substitute for a designated hose fitting, or just drill and Gas tap the plug.
10psi at cruise on the highway is good, 15 to 16 under load is good, this is why these engines are so fuel efficient also, plenty of air forced into them.

:):):D:D:twisted::twisted:

JC

[weeds]

Hi Kelvin,

At the manifold is better, as it is a true indication of the ACTUAL pressure available. Even better again is blocking off the fitting completely at the turbo, and using actual manifold pressure to control fuelling and wastegate operation by connecting it all up to the manifold itself. There is a handy plug already in the manifold that you can unscrew and either substitute for a designated hose fitting, or just drill and Gas tap the plug.
10psi at cruise on the highway is good, 15 to 16 under load is good, this is why these engines are so fuel efficient also, plenty of air forced into them.

:):):D:D:twisted::twisted:

JC

while driving to work this morning i was thinking about what would happen if i changed the plumbing so that the fuel pump receives its boost pressure from the manifold

you have just answered my question, reckon i will give it a go

[rick130]

I don't think it matters where you read it from, at least at the T piece on the turbo you are seeing what the boost compensator and wastegate see. It's all relative.

BTW, has anyone actually measured the pressure drop through the IC ?
I'm curious to know what it is.

FWIW I usually see around 12 psi cruising at 100km/h. Can drop to 10, but depends on road surface, head or tail wind, slight incline or decline, etc.

[Disco_owner]

Thanks Rick ;

I also didn't think it really mattered where you read the Boost pressure from , at the T-piece or the manifold , as long as the Compressor is doing it's job putting out a healthy 15-16psi of boost ,as long as all plumbing was intact .

Would be handy to have both to measure pressure drop accross the intercooler.:)

Edit :

Kelvin 10psi crusing around 100km seems about right , and you're right about not giving it a bootfull for Boost to get up to 15psi , 300 tdi engine is brilliant engine IMO.

[Pedro_The_Swift]

wont finding the pressure drop across the cooler just be an arguement for a better cooler???:angel:

[weeds]

wont finding the pressure drop across the cooler just be an arguement for a better cooler???:angel:

good point......don't think the account will release the funds though

[Bush65]

The boost compensator is fitted to the injection pump for environmental reasons. It's function is to reduce the fuel when the boost pressure is low (not enough air to burn fuel completely).

By connecting the line to the boost compensator from the manifold instead of the compressor outlet, you are fooling the compensator into thinking the boost pressure is lower.

So it should reduce the fuel, causing power to drop. Less energy in the exhaust gasses will reduce the performance of the turbo and boost pressure should drop ...

[weeds]

The boost compensator is fitted to the injection pump for environmental reasons. It's function is to reduce the fuel when the boost pressure is low (not enough air to burn fuel completely).

By connecting the line to the boost compensator from the manifold instead of the compressor outlet, you are fooling the compensator into thinking the boost pressure is lower.

So it should reduce the fuel, causing power to drop. Less energy in the exhaust gasses will reduce the performance of the turbo and boost pressure should drop ...

good to know land rover were environmently friendly in the mid 90's

pick up some fittings today, if i get a chance over the weekend i will switch the pipework over and see what happens

[PAT303]

Finding out the pressure drop was going to be one of my over xmas projects.I was going to chamfer,polish,smooth out the system from the turbo to the manifold and see what the actual drop with two gauges was going to be.I wanted to replace the pipe with a mandrel bent piece and silicon hoses but I can't get it made in Kal.It would be interesting to drive around for a week and record the findings. Pat

[justinc]

Finding out the pressure drop was going to be one of my over xmas projects.I was going to chamfer,polish,smooth out the system from the turbo to the manifold and see what the actual drop with two gauges was going to be.I wanted to replace the pipe with a mandrel bent piece and silicon hoses but I can't get it made in Kal.It would be interesting to drive around for a week and record the findings. Pat

Hey Pat, check out ThermoGuard Instruments (http://www.thermoguard.com.au) , Ian, a member here (leo109) has done some excellent research on this with his Tdi Disco...Makes great Pyro kits too!

JC

[Blknight.aus]

The boost compensator is fitted to the injection pump for environmental reasons. It's function is to reduce the fuel when the boost pressure is low (not enough air to burn fuel completely).

By connecting the line to the boost compensator from the manifold instead of the compressor outlet, you are fooling the compensator into thinking the boost pressure is lower.

So it should reduce the fuel, causing power to drop. Less energy in the exhaust gasses will reduce the performance of the turbo and boost pressure should drop ...

urmmm.....

putting the boost pressure sense on the turbo side of the intercooler tricks the boost compensator into thinking that its got more air to play with than it really has. This lets it inject more fuel which then raises the EGT's without giving you more boost.

its a lot more complicated balancing act than that but at the end of the day for optimal preformance and longevity the compensator needs to know whats going into the cylinders not whats coming out of the turbo..

[PAT303]

Hey Pat, check out ThermoGuard Instruments (http://www.thermoguard.com.au) , Ian, a member here (leo109) has done some excellent research on this with his Tdi Disco...Makes great Pyro kits too!

JC

Mate that was what I was going to do.I want a MUD center dash and fit up one of Daveys coolant alarms,pyro,tacho etc and I have the money in my pocket but right at the time I was going to buy the dollar dropped through the floor!. Pat

[LOVEMYRANGIE]

urmmm.....

putting the boost pressure sense on the turbo side of the intercooler tricks the boost compensator into thinking that its got more air to play with than it really has. This lets it inject more fuel which then raises the EGT's without giving you more boost.

its a lot more complicated balancing act than that but at the end of the day for optimal preformance and longevity the compensator needs to know whats going into the cylinders not whats coming out of the turbo..

2nd that one!

[Michele]

There is a handy plug already in the manifold that you can unscrew and either substitute for a designated hose fitting, or just drill and Gas tap the plug.
JC

Hi, any pic of this?

[nikjt]

The injector pump adds more fuel when the boost goes up to ensure the correct mixture, this is calibrated by land rover to change fuel dependant on boost pressure from the turbo, not the manifold pressure.
By changing the detection from turbo to manifold, due to the pressure drop across the intercooler the diaphragm will essentially sense a lower boost pressure therefore add less fuel and therefore a drop in performance.
I would leave the boost presure sensing from the manifold, by all means connect your boost gauge to the manifold to measure manifold preesure rather than turbo output pressure, two gauges would help you when upgrading the intecooler to understand the effect on pressure drop.

Nik

[pawl]

By switching your pickup for the boost gauge and compensator from turbo outlet to the manifold you will still get to your max boost pressure, as the turbo will keep pushing air and pressure right up to when the waste gate says no more and won't let it go over 15psi or where ever it is set to(the waste gate is connected to the boost compensator hose as well). The pressure drop over the intercooler relates to static and dynamic pressure, where static pressure is the drop in pressure from drag or resistance of the intercooler as the air passes through it and dynamic is the static pressure plus the drop in pressure from the reduction in temp of the intake charge(this is what gives you the efficiency of an intercooler). A cooler charge is more dense and so lower pressure for given volume. So by moving your pickup the gauge and boost compensator is reading the pressure entering the engine, which in my view is the better spot for it and you won't get a reduction in power.
Well that's my understanding of it anyhow.

[nikjt]

If you put a pressure gauge on the manifold there will be compared to the turbo outlet the pressure will be lower due to intercooler pressure drop, and also the pressure will slightly lag that of the turbo outlet.
Therefore the pressure that the diaphragm spring on the injector pump will be less than if it was sensing pressure on the turbo outlet, therefore the pump will only add fuel for the pressure sensed which is lower than that of the turbo outlet if connected to the manifold.
therfore a reduction in power, however you could adjust the diaphragm positioning toi take into account the drop in pressure across the intercooler, as you would have to if upgrading or changing your intercooler to anything other than OE to take into account the change in pressure drop.

Hope that makes sense.

Nik

[Bush65]

urmmm.....

putting the boost pressure sense on the turbo side of the intercooler tricks the boost compensator into thinking that its got more air to play with than it really has. This lets it inject more fuel which then raises the EGT's without giving you more boost.

its a lot more complicated balancing act than that but at the end of the day for optimal preformance and longevity the compensator needs to know whats going into the cylinders not whats coming out of the turbo..


2nd that one!
:angel: :angel:
You guys should check the stock 300Tdi arrangement.

Both the line to the wastegate actuator and the line to the boost compensator on the injection pump pick up the pressure signal from a tee piece on the outlet of the compressor.

There are no lines from engine side of the intercooler on a stock 300Tdi.

[isuzu110]

Just a follow up to this rather old thread ...

I purchased a 30PSI VDO boost gauge and plumbed it into the inlet manifold where the metric plug is at the back. Pirtek sell metric fittings and tapped a new brass plug to NPT to accept the supplied VDO fitting kit.

I'm seeing boost peak momentarily to about 16PSI on the inlet manifold before settling back to about 14PSI at full boost. I was expecting a bit more loss across the IC and am pleasantly surprised. I don't believe the boost has ever been wound up at the turbo. I have a slightly thicker JASE IC on the 300Tdi.

[sobloodyobvious]

Hi

Just read your now old post re fitting a boost gauge. You mention buying a brass plug from Pirtek. Can you recall the size of the plug? Any detail that will help me track one down would be appreciated.

Regards

[jboot51]

Found the receipt for my fittings.
Got them from Queensland diesel spares. (Truck spare parts place)
They were on the shelf in small blister packs.
21-327M1202- 12mm x 1/8" BSP Reducing Nipple
21-011001- 1/8" Tube x 1/8" BSP Female connector

1/8" is the hose size on my boost gauge.
12mm is the thread size on the intake plenum, thread pitch unknown.

[sobloodyobvious]

Fantastic. Thanks for that. The plug is not easy to get at so didn't fancy having to take it out and put it back more than once!