Thread: TD5 Inlet Manifold pressure

Originally Posted by B-A-S

For reference/advise.

The ambient pressure sensor is fitted in the air box to give the ecu the atmospheric pressure .
The inlet manifold pressure sensor is to give the ecu inlet pressure.

The ecu calculates the difference between the 2 and it then knows what the actual charge pressure is for injecting the correct ammount of fuel to match and able to alter/change with the boost modulator if fitted on some cars easy lol.

It ECU cant just relie on a sensor in the inlet manifold if it does not know what the outside atmosperic pressure is to take away from the actual seen manifold pressure so it uses both to calculate it.
It also uses this calcualtion for adjusting fuel and others maps depending on altitude which it can work out from the seen pressures.

There is abit more to it than that but from this you get the basics and my fingers are hurting now lol, and i dont type or spell to well either

Boost cut for the ecu is actualy 242Kpa, if you are hitting this then you have a charge pressure problem in most cases, or it coud be a bad raading sensor.
Normaly it is when the wastegate has been tampperd with it will give boost cut if over done.
Remember you can drive normaly one day and the next under some different load and ambient pressure you an hit boost cut.
So an ideal reading to see on th inlet side is actualy 220-225kpa as a mximium on a standard car.


Also its worth making a log of the car and see if there are any other sensors hitting a limit, the problem with nanocom is that it does not im my opinion record live or log as fast as some other tools so it can take time to work out the cause of a problem.

Pete

that makes so much sence now that its been explained! thanks pete.
so if 220-225kpa (31.9-32.6psi) is ideal on a std car what would be one looking at for an agressive remap, full 3'' zorst, one of your boost boxes, I/C, hoses and no egr??
i know ive hit 30 psi between turbo and I/C with trailer on up a large 40kph hill, blew the I/C hose off too, there was a fair bit of surging/cutting out when it happened. dose your boost box over ride the ecu completley or dose it have a safety in it?

cheers phil

Originally Posted by discowhite

that makes so much sence now that its been explained! thanks pete.
so if 220-225kpa (31.9-32.6psi) is ideal on a std car what would be one looking at for an agressive remap, full 3'' zorst, one of your boost boxes, I/C, hoses and no egr??
i know ive hit 30 psi between turbo and I/C with trailer on up a large 40kph hill, blew the I/C hose off too, there was a fair bit of surging/cutting out when it happened. dose your boost box over ride the ecu completley or dose it have a safety in it?

cheers phil

X2 for me too?

Our max pressure according to our Nanocom was 201Kpa with the right foot firmly planted, mine is chipped, silicon hoses, larger I/C, no EGR, 3" exhaust and wastegate turned 2 full turns for more boost.

Baz.

220 kpa is including atmospheric pressure, it's not all charge pressure.

I'll type more later I'm on a iPhone now so hard to type a lot.



Pete

Originally Posted by B-A-S

220 kpa is including atmospheric pressure, it's not all charge pressure.

I'll type more later I'm on a iPhone now so hard to type a lot.



Pete

I had another play today and recorded 225Kpa, 2nd gear flat to boards, mine is not standard.

Baz.

Originally Posted by B-A-S

220 kpa is including atmospheric pressure, it's not all charge pressure.

I'll type more later I'm on a iPhone now so hard to type a lot.



Pete

Correct, 1 bar..100kpa...14.7psi.....or near enough to, altitude dependant, atmospheric pressure, the rest is boost pressure

Thanks guys,

This makes so much more sense to me now...

As I am seeing pressures of 235, it looks like i need to take a look at winding back the wastegate adjustment - I haven't moved it - but it looks like it was replaced by the previous owner. Mine is chipped, silicone hoses and now no EGR....

I was also talking to someone today that showed me an example of a cat that had started to block up with black gunk. The owner of that car was also seeing a sudden drop off of power around 2500 rpm..

Thanks for all the great help.... I think I am finally starting to get my head around what is happening under there....

Cheers Mark

235kpa is on the limit of been ok or causing boost cut as you have found.
if you wind back to about 225kpa you should get rid of the problem.


remember this, evn if the wastegate is/was a a standard setting.
tuning will produce more exhaust gas, this inturn will produce more boost even tho the wastegate is not alterd.

In some cases a tuned car does need backing of on the wastegate to stop boostcut simly because the new produced exhaust smoke spins the turbo harder and increases the boost pressure without even having to alter it.

hope that makes sence


pete

Originally Posted by B-A-S

235kpa is on the limit of been ok or causing boost cut as you have found.
if you wind back to about 225kpa you should get rid of the problem.


remember this, evn if the wastegate is/was a a standard setting.
tuning will produce more exhaust gas, this inturn will produce more boost even tho the wastegate is not alterd.

In some cases a tuned car does need backing of on the wastegate to stop boostcut simly because the new produced exhaust smoke spins the turbo harder and increases the boost pressure without even having to alter it.

hope that makes sence


pete

Makes heaps of sense Pete...

God I love this place!..

Cheers, Mark