Thread: Boost gauge - 300tdi

G'day

Couple of comments/points.

My boost guage is a VDO. It has no "sender" as such. Simply a plastic tube that runs back to the guage.

Secondly, If you using a same of similar guage and you have drilled and taped a hole in the manifold near the entry point of the top i/cooler hose AND its not blocked AND you are not getting a reading, then you have a problem with the guage (assuming you tested this in working conditions).

Mine is presently plumbed into the line that goes to the Bosch pump but I intend to re locate it shortly now I have my workshop set up.
At 2500 - 2700 RPM in a decent rise mine will boost to 15.5 PSI at the compressor which I believe is spot on spec wise.

A reading from within the manifold is better when attempting to understand what is going into the engine. My assumprton here is that it will tell me how blocked the I/C is.

Personally I'd also like a temp probe in the snorkel and one in the inlet manifold as well to understand the temp difference. Ah, a man can never have too many guages.

Originally Posted by Lucus

Sorry I have to disagree with you Disco_owner Imho turbo outlet pressure is irrelavant, the pressure being recived in the intake manifold governs your a/f ratio and needs to be monitored if any tuning worked is carried out, I feel this is much more important as it will governs engine power output. A partially clogged intercooler or colasped intercooler hosing will still give you a good turbo outlet pressure but a decrease in manifold pressure and engine performance.

Errrm , If all the plumbing has been checked, no leaks or blockages in intercooler then there should be no pressure drop on the intake side
if any doubt have your intercooler pressure tested.

In my case:

> Silicon Hoses on turbo and intercooler side of
the alloy pipe clamped down with proper Clamps
> Brand new Intercooler.

AFAIK , there are no tuning adjustments on Turbo side and Only adjustment that can be made is increasing Max boost , the amount of fueling that controls boost and how quickly it's delivered to the engine is done via the Bosch Fuel Injection Pump adjustment, and it's important PumpTiming is correct for optimum performance,
Another thing that worth mentioning is Valve Clearances are also require checking and adjusting.

So What Boost Pressure the Compressor is Putting out is Relavant.

Originally Posted by Disco_owner

Errrm , If all the plumbing has been checked, no leaks or blockages in intercooler then there should be no pressure drop on the intake side
if any doubt have your intercooler pressure tested.

In my case:

> Silicon Hoses on turbo and intercooler side of
the alloy pipe clamped down with proper Clamps
> Brand new Intercooler.

AFAIK , there are no tuning adjustments on Turbo side and Only adjustment that can be made is increasing Max boost , the amount of fueling that controls boost and how quickly it's delivered to the engine is done via the 1.Bosch Fuel Injection Pump adjustment, and it's important PumpTiming is correct for optimum performance,
Another thing that worth mentioning is Valve Clearances are also require checking and adjusting.

2.So What Boost Pressure the Compressor is Putting out is Relavant.

1.Your saying there is no boost compensation on a bosch injection pump?

2. turbo outlet pressure is irrelevant, manifold pressure must be correct for the engine to preform.


ps there will always be a pressure drop across an inter cooler. Some super exotic mega $ coolers will get this down to less the .05 psi but i wouldn't be at all surprised to see 2-3psi drop across a 300tdi cooler possibly more if the engine has been tweaked up and the boost level is increased.

Thanks for all the replies guys!

I personally am interested in what boost the engine is getting that way i know if any thing else is playing up.

i have tapped the intake manifold where the red dot is should this be ok?



The sender i have is rated to 25 psi so it should be will with in the range! I am going to fit a mechanical psi gauge this arvo to find out if the sender setting are wrong with in the ems system

Originally Posted by Lucus

1.Your saying there is no boost compensation on a bosch injection pump?

No that's not what I'm saying , There is Boost compensation within the VE Bosch Fuel Injection Pump , but Boost is governed by the amount of exhaust thru delivery of Fuel into injectrors & combustion chamer , so if your Pump is optimised then there is correct compensation.

Someone can Correct me if I'm Wrong

2. turbo outlet pressure is irrelevant, manifold pressure must be correct for the engine to preform.

How does one control the intake manifold pressure ?

ah and there must be Plenty of Air pressure on the intake of the Engine if its Pulling away nice and hard and Boost gauge is reading max 15psi otherwise ah hang on there must be black fumes pouring out of the Exhaust Pipe if the engine is being starved of air.


ps there will always be a pressure drop across an inter cooler. Some super exotic mega $ coolers will get this down to less the .05 psi but i wouldn't be at all surprised to see 2-3psi drop across a 300tdi cooler possibly more if the engine has been tweaked up and the boost level is increased.

yes I agree There is pressure drop accross the Intercooler , When I say there is no pressure drop I mean Minimal.

No worries Mick and Good Luck with the Project , sorry for Hijack .

no worries Disco_owner i don't mind a good hi jacking at least it was still on topic

[
The boost compensation on a VE pump takes its boost pressure supply from AFTER the intercooler. This is the pressure that dictates the extra fuel. Not the pressure at the outlet of the turbo.

If it was taken from the outlet side of the turbo (pre aftercooler and thusly major restriction in the intake system.) You would have excess fuel.

We covered this pretty clearly ten years ago when i completed my apprenticship as a diesel mechanic. I dont want to get involved in pedantics or overly simplistic explainations of how a diesel engine works but if you would like to illustrate the point to your self go and buy a cheap boost gauge and fit it to the manifold and compare the difference in boost. 2-3psi may not seem like a lot but as far as the fuel pump is comcered t has a major effect on performance.

I think we should agree to disagree on this one.


Luke