Boost Spikes - analog or digital gauge/pros & cons???

hutchman

Veteran Member
Joined
Sep 6, 2005
Location
Virginia
TDI
2006 Jetta TDI Pkg 1, 5 Spd, Graphite Blue / 2002 Jetta GLS, Black w/tan leather
I guess I should have called this mechanical vs digital!

I've been searching these forums trying to educate myself on boots gauges, boost valves etc.

I'm leaning toward getting the in dash DIY digital LED boost gauge that goes in the dash around the tach that ShokWaveRider (IMP) has.

From what I've gathered it is important to keep the hose from the IC to the gauge or sensor as short as possible which would favor a digital solution.

On the other hand, I've read where mechanical gauges (where the hose has to come into the cabin to the gauge) is better at showing boost spikes.

Is my understanding so far correct?

Anyone care to comment on pros/cons of digital vs mechanical boost gauge.

Also, I may go with a VNT17 in the future and all my reading makes me think I need a boost gauge that goes to at least 30psi? Is this correct.

Thanks in advance for the info.
 
Last edited:

Fix_Until_Broke

Top Post Dawg
Joined
Aug 8, 2004
Location
Menomonee Falls, Wisconsin, USA
TDI
03 Jetta, 03 TT TDI
hutchman said:
I guess I should have called this mechanical vs digital!

I've been searching these forums trying to educate myself on boots gauges, boost valves etc.

I'm leaning toward getting the in dash DIY digital LED boost gauge that goes in the dash around the tach that ShokWaveRider (IMP) has.

From what I've gathered it is important to keep the hose from the IC to the gauge or sensor as short as possible which would favor a digital solution.
There is only compressible flow in this hose (ie: almost none unless you also have a boost valve connected to the same hose - see below) so the length of this hose won't matter for what we're doing here unless you are using 50 feet of it or it is 1" in diameter (ie: lots of volume inside it)

hutchman said:
On the other hand, I've read where mechanical gauges (where the hose has to come into the cabin to the gauge) is better at showing boost spikes.
It depends on the damping/response of the mechanical gauge and the sampling/display rate of the digital gauge. I've seen both significantly faster than the other. In theory, ShockWaveRider's digital gauge is the best of both worlds (no buzzing possible and fast and tunable response/filtering) I don't know the specifics of the sample/display rate of the hardware he is using so I can't comment. A digital "gauge" with a bunch of seven segment displays will be the absolute worst in catching/seeing boost spikes. Any kind of "analog" sweeping motion is much easier to read be it a needle on a mechanical or electric gauge, or an arc or row of 25-30 led's

hutchman said:
Is my understanding so far correct?

Anyone care to comment on pros/cons of digital vs mechanical boost gauge.
See above

I have a Stewart Warner plumbed into the vertical riser of my intake manifold and it buzzes over ~12 psi. This is where my boost valve will eventually connect. My boost gauge will be able to connect either at the turbo outlet bell or somewhere near the intake manifold (race pipe maybe?)

See my posts in this thread (http://forums.tdiclub.com/showthread.php?t=134320) for why to put the boost valve as close to the head as possible without tapping into individual runners.

I would caution against running the boost valve and gauge off of the same port as you could get inaccurate boost readings depending on how much flow the boost valve lets through and how restrictive the plumbing is between the manifold connection point and the boost valve/gauge. If it works for some - great, if it's the only option you are willing to do - fine, if you have the option to seperate them - do it.

hutchman said:
Also, I may go with a VNT17 in the future and all my reading makes me think I need a boost gauge that goes to at least 30psi? Is this correct.
From what I've read, unless you are headed for the other side of 200hp, 30 psi will be plenty, 25 would be fine as well and give added resolution.

hutchman said:
Thanks in advance for the info.
 
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