Blitz DSBC and HKS Gauge Blues !?!?!?

[dandan]

Hi Guys, after a bit of advice.

 

Previously running 1.00 - 1.05 bar with a bleed valve until i connected the DSBC and took off the bleed valve.

 

Now, regardless of settings on the DSBC the boost gauge won't read above 0.55-0.60 on the peak hold. Yet the DSBC can hit its limit of 1.05 or 1.10 bar and knock the boost back below this.

 

The car does seem to be a little slower as if it's not makng boost above 0.6bar. So i think it is not making any boost above the 0.6bar and the dsbc is malfunctioning and reading too high and cutting boost when really it's not actually making any decent boost.

 

Boost builds to 0.5 bar, then drops sloghtly before rising slightly again to the 0.55-0.60 bar. So i think the bleed off to no. 2 is working ok but the boost is just not very high.

 

As far as i can see there are no leaks anywhere and everything is blanked off and connected correctly. The boost gauge and DSBC take their pressure feeds from the same place.

 

What do you think guys, any ideas???

[Thorin]

I'd still reckon it's probably a leak somewhere. Either that or possibly turbo's on the way out

 

I'm sure there are other things it could be though.

 

 

What boost do you make on just turbo #1? Does this then rise to 0.6 when the second comes online?

[dandan]

i dont think it can be a knacked turbo, i was driving in the day with the bleed valve in, did the dsbc in the evening and went out testing/setting up that same night.

 

I can't think where a leak could appear from in that space of time but i will triple check.

 

I think no.1 is making about o.5 bar and then this rises to 0.55-0.6 when no.2 comes online.

 

But...........why would the dsbc give a different reading to the gauge. e.g. a gauge peak hold of 0.55 and dsbc displays peak of 0.86 for example.

 

Surely if there was a leak then they'll both read low? I thought at first the dsbc was reading a real quick spike which the hks gauge could not pick up. However the gauge won't go above 0.6 at all even giving it WOT in any gear for any length of time, whereas the dsbc may read 0.95bar.

[dandan]

The way i see it there are two options:

 

1. The gauge is wrong, boost is as indicated by the dsbc and i have no real problems and have obviously gotten used to the performance of the car ans it no longer feels as fast.

 

2. The gauge is correct and for some reason, boost won't get above 0.6bar with the dsbc in place. In this case either there is a problem with the dsbc(failed pressure transducer or similar) or something else has occured such as a leak.

 

Come on people, help me out, what do you think i should try/check next?

[Thorin]

Strange one.

 

I'd usually be more inclined to believe a mechanical boost gauge rather than a boost controller. Perhaps you could check the piping to your boost gauge for leaks and that it's secured properly on the back?

 

0.5 on the first turbo rising to 0.8ish when the second turbo comes online is probably about right for a standard car (didn't have a boost gauge when mine was standard). So maybe the boost gauge is a bit dodgy and the controller is to be believed after all? I dunno, but you certainly get used to the power. I remember thinking my car was unbelievably fast as standard but didn't take long to get used to it.

[Guest Martin F]

This is a hard one without knowing how things are plumbed in.

 

Is your DSBC installed as described by the article on MKIV.com ?

 

I would start with your DSBC and it's installation first and then start looking at the boost gauge plumbing.

[Adam W]

My DSBC has always read much higher than my boost gauge, even when I plumbed them into exactly the same vac line. No idea why, I choose to believe my boost gauge as it makes more sense (I have had it checked as well) and set the warning level on my DSBC at, say, 1.8bar, which equates to 1.2 bar on my gauge.

[dandan]

The dsbc is installed EXACTLY as per mkiv.com. I did wonder whether the vacuum cap over the spare wastegate actuator could cause any problems if it had air trappe under it, but i had a fiddle with it and can't see anything wrong at all installation wise.

 

I would normally put more faith in a mechanical gauge than the dsbc but my HKS gauge is electrical. There are no pipework connections to it. It has (what i think) is a pressure transducer under the bonnet and this feeds the actual gauge an electrical signal coresponding to the boost sensed at the transducer.

 

I wondered if a poor connection (12v or similar) to the gauge or transducer may be preventing it reading higher than 0.6bar - not enough voltage perhaps?

 

When i increased the gain up to about 11 or 12 and set the ration to 58 i can get 1.08bar on the dsbc and still only 0.55-0.6 bar on the hks gauge. The car does feel fast so i have a feeling the dsbc may be correct and something has happened to the gauge.

 

Unless i have a leak somewhere then it would be next to impossible to generate a max of 0.6bar with a Trial exh and large 2nd cat replacement pipe. I am intending to check the gauge soon with another pressure source. The next step i think will be to see if i can find anyone kind enough to let me borrow their dsbc display and see if there's a difference.

 

Adam, (or anyone else) are you not a little dissapointed that the two pressure displays are so different? Have you ever heard of anyone who calibrates boost equipment such as the dsbc?

 

Martin the pressure line for both the gauge and dsbc come from the same pipe (from plenum) with a T piece installed to feed both.

 

Thanks for all the advice chaps, please keep giving me ideas..

[Guest Martin F]

I wonder if there is a blockage in the pipe to the sensor for your HKS gauge or maybe some oil or crap in the sensor.

 

Just to add i have a similar setup but with my DSBC boost reading plumbed in near the BOV and my Greddy boost gauge plumbed into the inlet manifold. Both always read the same and peak holds on both are always in agreement.

 

Be a good start to get your pressure gauge checked out on a calibrated pressure source.