007TT

Is it normal to see the cmd pressure lagging the intercooler pressure most of the time on measurement block 20 using vagcom? Thought it should be the other way around. Also, should I be seeing boost (up to 300mbar) even when commanded boost is 0?? Could this be a problem with my N75?

Any help would be greatly appreciated.

Engine Speed | Cmd Pressure | Press @ Intercool
RPM mbar mbar
720 1000 1010
720 1000 1010
720 1000 1010
720 1000 1010
720 1000 1010
760 1000 1010
2000 1060 1000
1800 1040 1120
1920 1000 1260
2320 1000 1200
2720 1000 1140
3080 1000 1170
3520 1000 1230
4160 1000 1360
4880 1090 1420
4640 1000 1270
3760 1000 1100
3480 1560 1290
4120 1700 1900
4840 1660 1810
5200 1000 2010
4200 1000 1190
3640 1000 1070
3600 1000 1090
3640 1000 1100
3640 1000 1100
3640 1000 1100
3400 1000 1120
2760 1000 1060
2080 1000 1050
1440 1000 1030
1120 1000 1020

TTschwing

You will not get a good boost picture that way. You have to be under load. This is a 4th gear run of my car. It's been modded a bit....
Do the same 3rd or 4th gear acceleration run from idle to redline then Plot your numbers in Excel for graphs like those below.

<img src="http://images1.fotki.com/v12/photos/7/7305/130918/postmod-vi.jpg">

A more typical graph might look like this from the early days with my car... (All with APR 91 in these examples)

<img src="http://images1.fotki.com/v7/photos/7/7305/130918/pressures-vi.jpg">

Steve

That damn Dan

increased difference between Manif and IC pressure (in the upper graph) due only to the higher internal volume of the FMIC/hoses?

Or is there a leak back by the IC somewhere?

I know, the second question is dumb but I'm still just a "pupil".

Dan

TTschwing

Mostly efficiency improvements...Smooth hoses, Intake, Exhaust, cooling etc...

Lots of little improvements to get to the end result...

That damn Dan

We can see that the amplitudes are all higher in the upper (all mods) graph.

My question had to do with the increased spread between the IC and Manifold, in the upper graph.

They are nearly equal in the lower graph, but the IC lags the manifold in the upper graph, which means that a pressure differential has developed along the tract between them.

Lower pressure in the IC than at the manifold just a few inches away...???? What accounts for that?

Thanks,
Dan

TTschwing

The manifold value is actually a calculated number, not measured by a sensor. The MAF flow largely determines this number and the VAG maxes out at 2550 Milibars (22.75 psi or so). In reality though Manifold pressure is there or more (depending on where i set it and according to an accurate boost gauge reading off the manifold). Part of the differences have to do with pressure drop across the IC's and part from Intake manifold design/valve timing etc, that actually provides a bit of pressure increase at the manifold..

That damn Dan

"Aye, There's the rub"...The manifold value is actually a calculated number. Thanks!