Turbos: to boost or not to boost...that is the question.

[S4TAN]

There's no way i've ever seen those kind of boost levels at those revs uphill in 5th in my car! What's your boost pressures at similar revs (1500, 2000, 2500 etc) on a flat road through 1st 2nd 3rd 4th gears...?

Does the DNA map run extra high boost at low revs?

Am i talking arse..?

[s4woody]

i,ll check tomorrow..i wouldnt call my boost extra high..it shows 20psi on the gauge..is that high?? 1.2 ta 1.3 bar??

[S4TAN]

not high overall - it's more to do with the boost at those revs: 5psi at 1500rpm, 10psi at 2000 and 20psi at 2500rpm etc - that's the bit that seems high to me..

[stimp]

It's not a log so I might be off by a few revs but thats pretty much right. By about 2200 you can really feel it starting to pull hard as the boost I guess is winding up past the previous stock levels. Going through the gears you just slot the next one in at 4k and it flys without a lot of fuss. the last 2.5k is only if you've got something to prove. It's actually pretty damn quick even if you only use up to 3k.
Woody, does this sound similar to yours?

[S4TAN]

it shows 20psi on the gauge..is that high?? 1.2 ta 1.3 bar??

Interesting; i'm guessing your boost gauge is tapped off your FPR hose? From my last vagcom log my peak actual boost (measured at the MAP sensor) is 2360mbar which equals about 1.36bar when you subtract atmospheric pressure - so same peak boost as you're running (20psi), but my boost gauge only ever registers about 17psi max - i guess this is because of the ~3psi pressure drop between the charged air pressure actually entering the throttle body to what comes out of the engine manifold and up to the boost gauge......

....so if you get 20psi on your gauge maybe you're getting ~23psi actual boost, which is nearly 1.6bar - can that be right? What's your max actual boost on your vagcom logs..?

[s4woody]

my boost gauge is taken from my fuel pressure regulator hose..theres a post on fitting boost gauge and i posted a pic on there..its T'd into the red hose in the pic..when i had a dyno day at QST i was told the bar pressure was 1.2-1.3..

[S4TAN]

yep - my boost gauge is T'd into my FPR hose too - but surely there has to be a pressure drop between the boost pressure that goes into your engine to what your gauge reads. You got any logs you can post woody?

[s4woody]

i had logs on the thread the deed is done..but im not sure if the boost is shown..markB is going to do some more with me when i get dwn to him..

[S4TAN]

Here's a pic of a set of logs graphed for FATS runs (all 3rd gear pulls) in my car...i don't see all my peak actual boost levels until around ~4.5Krpm upwards (between 18 and 20psi).....but you guys make +5psi at 1.5Krpm and up to +20psi at 2.5Krpm on the DNA map....(!)

..must be that the custom MRC map doesn't make peak boost until much later in the rev range i guess... Anyone else have any logs/graphs of their maps (MRC, DNA, MTM etc)? Would be interesting to compare when the different maps make their peak boost pressures...

[stimp]

Woody, did you get a chance to check your RPM versus boost on the gauge today. Be good to know if yours is similar to mine. My gauge sounds like it is fitted in same place.
Just tapped into the line going into the fpr with a T-piece as normal.

[S4TAN]

Yeah - c'mon all you dudes out there with re-maps and vagcom - post your logs/graphs so we can see when and how the different maps make boost .....(i can make the graphs for any logs if anyone is unsure of how to do this - just pm me the spreadsheet)...

[MarkB]

It's been done before, i posted about boost logs a while ago...

[S4TAN]

Great - got link?

[MarkB]

http://www.rs246.com/index.php?name=PNp ... ight=boost

[S4TAN]

That's some good work Mark - exactly what i was after. Do you fancy resurrecting this thread temporarily and factor in my logs to your master graph if i send you the spreadsheet?