Overboosting on a VNT15

vwcaddy2126

Active member
Joined
Jul 14, 2007
Location
Singapore
TDI
VW caddy 1.9
Hi all,
I have this overboosting problem on my stock vnt15 which i can't seem to solve. A while ago I thought it was probably due to the DP digi z box being set too high in the range. But after removing it, I did some driving and its still going up to the 20psi range. I did try swapping a new N75 and a new map sensor but it still had overboosting problems. I've also taken my turbo apart to clean off all the carbon which were on the vane side of the housing, taken my intake manifold out to clean off the carbon deposits and disabled my EGR system. Mods I have on my car are a 2.5" cat back exhaust, K&N cold air intake, Diesel Power Digi Z box, .216 Nozzles, 11mm Injector pump rotor, Injector pump camplate upgrade, VR6 clutch. Could anyone come up with any suggestions?

Mark
 

G2 GofF

Well-known member
Joined
Aug 14, 2006
Location
Alberta
TDI
2011 Jetta
Sounds to me like a sticky VNT actuator. Do you have any air mods because it seems like you have alot of fuel which causes soot but little boost. Could be a leaking vacum line too. Lots of diffrent things. Do you have any codes?
 

vwcaddy2126

Active member
Joined
Jul 14, 2007
Location
Singapore
TDI
VW caddy 1.9
I did get it to a VW workshop and did a vagcom check. Resetted some faults like the N75, map sensor and I did install new silicon hoses all round when I put the turbo back together.

Mark
 

G2 GofF

Well-known member
Joined
Aug 14, 2006
Location
Alberta
TDI
2011 Jetta
What exactly did you do when you cleaned the turbo. I remeber there is a thread or PDF file with all the info you need to clean your VNT vanes. Did you complete disassemble the turbo and clean it. Sorry for the spelling, its getting late. I will try and find the thread.
 

vwcaddy2126

Active member
Joined
Jul 14, 2007
Location
Singapore
TDI
VW caddy 1.9
Some of the vanes are totally jammed at some point. All I did was completely remove the housing and cleaned off the carbon deposits which were inbetween the vanes. Before putting it back on, I put a bit of 2 cycle oil on the vanes to ensure it lubes it good.
Thanks for the help pal.
Mark
 

G2 GofF

Well-known member
Joined
Aug 14, 2006
Location
Alberta
TDI
2011 Jetta
Have you tried moveing the actuator by hand. It should be loose and move very easily. If it's tough to move it needs to be cleaned. Try applying vacuum to the actuator and tell us how much pressure is required to make it move. A vacuum pump is required here.
 

LurkerMike

Veteran Member
Joined
Feb 1, 2006
Location
Atlanta Jawja
TDI
-Whitey: 2000 Jetta GLS, Red: 2000 Jetta GLS 5-speed
vwcaddy2126 said:
I have this overboosting problem on my stock vnt15 which i can't seem to solve. A while ago I thought it was probably due to the DP digi z box being set too high in the range.
How would you know if or when you set the box too high? I mean before you damage something? Is there a calibration method or adjustment specifications that you omitted? Or do you turn the screw and pray?

I know this probably sounds like I'm a total arsehat, and I am. And it probably looks like I'm hijacking your thread, and I suppose I am... But seriously, I know a a bit about TB's in general but very little about the Diesel Power boxs specifically. Do you mind enlightening me on the DP box tuning method... I'm thinking at least it is a free bump and may keep your legitimate questions at the top longer potentially for a better answer.

And I get to re-post this:



A win-win if you ask me.... :D

If you are not happy discussing the DP box here in your thread, please let me know and I will delete this post... ;)
 

vwcaddy2126

Active member
Joined
Jul 14, 2007
Location
Singapore
TDI
VW caddy 1.9
The actuator moves easily by hand. I will try the vacuum test which you told me about at my workshop later. I was also wondering if there might be a leak inbetween the compressor housing.
Mark
 

vwcaddy2126

Active member
Joined
Jul 14, 2007
Location
Singapore
TDI
VW caddy 1.9
LurkerMike said:
How would you know if or when you set the box too high? I mean before you damage something? Is there a calibration method or adjustment specifications that you omitted? Or do you turn the screw and pray?

I know this probably sounds like I'm a total arsehat, and I am. And it probably looks like I'm hijacking your thread, and I suppose I am... But seriously, I know a a bit about TB's in general but very little about the Diesel Power boxs specifically. Do you mind enlightening me on the DP box tuning method... I'm thinking at least it is a free bump and may keep your legitimate questions at the top longer potentially for a better answer.

And I get to re-post this:



A win-win if you ask me.... :D

If you are not happy discussing the DP box here in your thread, please let me know and I will delete this post... ;)
Dear Lurker,
I was told that not all cars respond to the box highest setting. How I judge my box setting is by the manufacturers recommended setting which is 'C'. Apart from that it should spike for a mere second or two & boost levels should back down if it doesn't, it is set too high. What are yr comments on that?
Mark
 

LurkerMike

Veteran Member
Joined
Feb 1, 2006
Location
Atlanta Jawja
TDI
-Whitey: 2000 Jetta GLS, Red: 2000 Jetta GLS 5-speed
vwcaddy2126 said:
Dear Lurker,
I was told that not all cars respond to the box highest setting.
By all cars, do they mean all ALH's or all TDI's? I mean how many different year/make/models will the box fit?

Does DP offer a deal where you do some VAG-COM logs and send to them to be analyzed for fine tuning recommendations?

Obviously we know the Q-loader is based on this principle. Jeff did this with every tune he did at the GTG where he tuned me and he has even let me email him logs to look at to verify everything was still kosher.

Of course they were runs that I wouldn't do with Jeff's son in the car when he ran the VAG-COM at the GTG... they were solo zero mph on an interstate on-ramp to spinning both front wheels through 1st and 2nd gear then pound on it WOT to 130 mph indicated in less than a mile and then brake hard and 4 wheel drift a little to make the next exit ramp and back to zero. :D Whitey only makes 125-ish indicated in this test and must brake much harder as terminal velocity takes more road to get achieve and this leaves less room to slow down to make the ramp.

I say all of that to say that while I know first hand the after sales support that KERMA and RocketChip give, I never hear much about TB tech support here. Am I overlooking it or perhaps it is lost in the "fog of war"? :D
 

ini

Well-known member
Joined
Apr 11, 2007
Location
Lancashire, UK
TDI
A4 TDI SE 110
If you have massively increased fueling, removed EGR function and reduced back-pressure, your turbo will be spooling up faster and probably spiking/overshooting higher.

If your mapping is not set up for a higher steady charge, try backing off the vnt actuator, or using a 'boost valve' at the N75 to help kill spikes etc.

If you are getting 20psi solid boost (not spike) this is the limit of vnt15 charge returns (temps will greatly increase, lowering the density of the charge + impeller will grenade)

Most likely small boost control leak, dodgy check valve or actuator, or you have upset something when you cleaned your turbo.
 
Last edited:

LurkerMike

Veteran Member
Joined
Feb 1, 2006
Location
Atlanta Jawja
TDI
-Whitey: 2000 Jetta GLS, Red: 2000 Jetta GLS 5-speed
vwcaddy2126 said:
DP offers boxes for all ALH's and PD vehicles. You should contact jose@jsperformance.ca for more technical insight on the DP boxes. Thanks

Mark
Thanks Mark.

Pretty much I ignore what Jose, Charlie and Jeff have to say about what they sell. It is unimportant to me.

I judge a product by the happiness of its end users... lots of end users... lots of end users who are happy using the product the same way that I plan to use the product.

I'm weird like that.

I'm not a box hater, really. I admit I know little about them and while I don't see a box in my personal future, I would like to know lots more about them, but from the end user perspective.

I am looking into a boost spike management idea that is probably 2 years from market if it even proves to be workable. That's what caught my eye with your post... and what has me thinking that box users might benefit the most.

Here is something to ponder... for years when you would turn on a water faucet in older homes the first time in the morning or after several minutes or hours of non-use, the water would GUSH out for a moment and then settle down. This "gushing" is a result of a water "PRESSURE SURGE!" It is a momentary pressure spike that once vented, does not affect the steady water flow for as long as the faucet then remains open.

Why the gushing pressure surge? Because hot water tank heaters tend to form some steam pockets as they heat the water and hot water displaces more area than cold water. Also most water pressure regulators that are standard plumbing requirements for years in most areas of NA, act as a one-way valve and do not let the expanding water and steam pressure escape back into the city water system.

There is a solution and it is now a plumbing code requirement in many areas... it is simply adding and air bladder surge tank that absorbs the pressure surge as it builds and it releases the surge pressure back into the home plumbing slowly when a faucet is opened.

;)
 

vwcaddy2126

Active member
Joined
Jul 14, 2007
Location
Singapore
TDI
VW caddy 1.9
Hi,
I really understand your plight about these products being sold and marketed by those you have named. To tell you honestly, I'm new to diesels and I've always been a gasoline junkie from my mitsu evo3 and all my pass hot rods. The reason I switched was due to my job which required me to travel around alot. Figured that diesels were the way to go. What I'm actually looking for in a diesel is pure horsepower and not a box which tells lies to your ecu and other sensors. Thats #$%@*&! BS if you ask me. Its only temporary hp increase till I figure this whole set up.
About your other ideas that you said about, well I would seriously agree with you on it. Get a prototype going soon. Cheers pal:)

mark
 
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