Technical boost & Vacumme JTD 115

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Technical boost & Vacumme JTD 115

Joined
Feb 10, 2009
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Essex
Hi chaps, just need some advice really, been looking at boost gauges, and some people have said you need one that is 3bar and some people say that 2bar is fine, what one should i be going for? any advice would be much apprecieated...

also where could fine a good vacumme source? as i have been told the boost gauge will not read vacumme on the jtd? is this correct? if it is where can i get a feed for a vacumme gauge.

thanks in advance people for any help you can give me,

cheers

robin
 
Joined
Sep 29, 2008
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Wolverhampton
Really depends on how extreme your tuning is.

All standard JTD's have 3 bar MAP Sensors the reason for this is:

As far as the MAP Sensor is concerned, 0 bar is a vacuum
1 bar is normal air pressure, the stuff around us right now.(approx.)

If a car produces 1 bar of boost raising the pressure to 2 bar(as far as the MAP Sensor is concerned) but would actually be 1 bar of boost.

If the car produces 2 bar of boost, the MAP Sensor see's 3 bar(its maximum) but its only 2 bar of actual boost so a 2 bar boost gauge is sufficient.

There is no throttle on a diesel so there is no vacuum to measure. Throttling the airflow into an engine(petrol engines) causes a vacuum in the induction system between the throttle and the engine. Once the throttle is open and charged air(boost) from the turbo is allowed through the vacuum is turned into boost. Diesels don't have a throttle resulting in constant state of boost, there's no vacuum to measure.


Not sure if that's easy to understand but hope it helps ..

I have one of these partly installed on my XC90 for diagnostic purposes. Its more suited to a diesel IMO, runs a 50 second voltage test before switching over to display boost.
http://www.ebay.co.uk/itm/190843643007
 
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Joined
Oct 21, 2007
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1,057
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north wales
As said above forget vaccum.
Your std car will run around 19psi boost mapped maybe 23-24psi and stuck vanes in turbo possibly spikes well above.
Heres my 0-35psi gauge topping around 26psi

http://youtu.be/pOM8PIC1o6A

A point to shadys post the early 8v might only have a 2.5bar map sensor.
Either way youd be wasting sweep with vac or going too high like 45psi
Id have gone with a 0-30psi but couldnt find one or the 35psi was cheaper.
Mines mechanical, im not sure how the lcd gauges get their reading, off car map sensor or extra map sensor?
 
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im not sure how the lcd gauges get their reading, off car map sensor or extra map sensor?

Basically another MAP Sensor is installed, far less accurate than the original Bosch but adequate for the job. Have attached a pic of the one on my XC90.
 

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rat20v
Joined
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Essex
thank you so much for the advice and pointers extremely helpful thank you i will be purchasing my boost gauge next week thank s again chaps :)
 
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