www.tdiclub.com

Economy - Longevity - Performance
The #1 Source of TDI Information on the Web!
Forums Articles Links Meets
Orders TDI Club Cards TDIFest 2016 Gone, but not forgotten VAG-Com List Unit Conversions TDIClub Chat Thank You




Go Back   TDIClub Forums > TDI Model Specific Discussions Areas > VW MKIV-A4 TDIs (VE and PD)

VW MKIV-A4 TDIs (VE and PD) This is a general discussion about A4/MkIV Jetta (99.5-~2005), Golf(99.5-2006), and New Beetle(98-2006). Both VE and PD engines are covered here.

Reply
 
Thread Tools
Old February 20th, 2019, 20:38   #1
BeetleDragon737
Member
 
BeetleDragon737's Avatar
 
Join Date: Jun 2014
Location: Hagerstown, MD
Fuel Economy: 40.5 MPG
Default Boost Spikes - turbo actuator and boost valve questions

I've been searching and reading so many threads about boost that it's getting exhausting. I still have questions, so hopefully some wise folks can chime in.

Background:
The car is a '99 Beetle, ALH engine. I'm pretty sure it was stock when I bought it. After connecting a boost gauge to the upper intercooler hose a few months ago, I saw that my boost spiked to 19 psi max and leveled off around 14 at WOT (don't know why we use that term when these cars don't have throttles). After some reading, this seems pretty normal.

After getting DLC 520s installed, my boost spikes to around 22 psi max, and levels off around 14. The turbo can only handle 18.5 psi sustained, so the increase concerns me a bit. I'm going to RocketChip to get RC3 in about two weeks, and I know the tune will increase boost, so I called Jeff. I asked about a boost valve, but he called it a band-aid and said that even if it was installed, the spring is tuned to a certain psi and can only operate in a dynamic fashion. Thus, if sustained overboost occurred, a boost valve would stop relieving boost eventually and could not adequately protect the turbo. He said I should address the underlying problems instead (ie, turbo actuator, vanes, etc).

So, questions:
1. If the boost valve is really just a relief valve with a spring that gets compressed at a certain pressure, why won't it stay open as long as overboost is still occurring? If that's true, what's the hesitation with using one? Surely installing one is far simpler than disassembling the turbo to clean out carbon from the vanes, etc.
2. If I choose to use a boost valve, where can I purchase one that does not have a vent hole? I know a vent hole is not desired for these turbos/actuators. Why?
3. If I decide to adjust the actuator, do I only adjust the stop, or is there more adjustment that can be made? Will this only affect the max boost, or will it decrease my sustained boost as well?
4. Is it straightforward to access the actuator on the Beetle's turbo, or will I have to remove things to get to it?
5. If it's carbon on the turbo vanes that's slowing the turbo response rather than a misadjusted actuator, can some of that be burned off by revving near redline and keeping the EGTs high for an extended period of time?

Thanks for any help.
__________________
Current things:
DG skid plate, South Bend S2D clutch w/ SMF, DLC 520 nozzles
Planned things:
RC3, racing stripes

Last edited by BeetleDragon737; February 20th, 2019 at 20:40.
BeetleDragon737 is offline   Reply With Quote
Old February 20th, 2019, 23:10   #2
Nero Morg
Veteran Member
 
Join Date: Oct 2017
Location: Beaverton Oregon
Default

Short answer... Yes.. Yes. Yes. No. Yes. Maybe. Lol.

Yes your turbo vanes are probably jamming up causing the delay.

Yes you'll need to replace your turbo or at the least take it apart and clean the vanes.

Yes you should check your actuator movement.

No there's only the actuator rod you need to adjust. Don't move the stops. Rod should start to move at 3-5inhg, full stop at 16-18inhg. With the actuator disconnected, it should have almost no resistance to move.

And yes a boost valve is a bandaid. It doesn't limit boost pressure, but limits the vacuum to the actuator to lessen the boost, but it will creep back up.

No there's nothing fancy you need to take off to get access to your actuator. Just jack up the front end and put on stands, you'll see it easy.

As for the vent hole on the boost valve, that I don't know anything about.
__________________
2003 Jetta Wagon silver- DLC520 VNT15 11MM pump 5 speed
ESP retrofit, MFSW retrofit
Malone Stage 2 w/ South Bend stage 3 endurance
Midwest Light Creation's HID headlights
Nero Morg is online now   Reply With Quote
Old February 21st, 2019, 07:38   #3
gforce1108
Veteran Member
 
gforce1108's Avatar
 
Join Date: Aug 2006
Location: Newburgh, NY
Fuel Economy: Jetta: 44.5 summer / 47 on snows
Default

Make sure that the "vent" line / hose that gets clean air from the side of the air box is not restricted. This is what allows the N75 to release.

There is another band-aide you can do... if you Tee into the boost and run it to the N75 (instead of the vent), it will move the actuator back to rest faster than just the internal spring. I've used it along with a boost limiter ("dawes device") - to tune in my max PSI to 24 on my BEW. It was supposed to be a temporary thing until I got my 3bar MAP installed and retuned, but it works so well I've left it for years.
__________________
I hate rockauto.com http://forums.tdiclub.com/showpost.p...&postcount=236
04 Jetta GLS 5sp - EGR delete, RC3, VNT17/22, 3" turbo back exhaust & 2.5" FMIC+PD150 intake. SBC Stage 2 Endurance w/SMF. Eibach lowering springs
gforce1108 is offline   Reply With Quote
Old February 21st, 2019, 08:31   #4
BeetleDragon737
Member
 
BeetleDragon737's Avatar
 
Join Date: Jun 2014
Location: Hagerstown, MD
Fuel Economy: 40.5 MPG
Default

Hmm

I don't have the time/resources at the moment to fight through all the rust to get my turbo off. So with that option out the window...

Regarding adjusting the stop on the turbo, in certain situations moving the stop is the proper treatment, right? Why not here?

And could you explain why the boost valve will allow the boost to creep back up? My understanding is that a certain boost pressure (determined by the spring force) will open the valve. At that point, boost pressure will be sent to the vacuum side of the actuator. This opens the vanes in the turbo, thus decreasing its rpm and the boost it can generate. This is essentially the same thing the N75 does, right? I would assume the boost valve won't close till the pressure drops, so why is it not functioning as effectively as the N75?

Without fully understanding the creep issue you mentioned, is it possible this is a result of using the wrong boost valve? That is, one with an open vent rather than one with the vent plugged?

gforce, thanks for the idea about sending boost pressure to the N75. Is there a chance this will decrease its lifespan?

And if all of this won't stop the boost fast enough, as a last resort, why not just stick a standard pressure relief valve into the lower intercooler hose? Extra boost would get dumped to atmosphere. Obviously this isn't how the system is designed, because the turbo would still be "trying" to generate boost. But does that really matter if the boost is sent overboard? Will the turbo overspeed?

Also, here is the boost valve Kerma sells.

The site says, "The BoostValve has always had a very small vent hole to release any air trapped in the waste-gate line after boost pressure drops... For vacuum controlled waste-gate setups such as the VW VNT turbo use a non-vented cap for a completely sealed valve." I guess I'll contact Kerma to see whether that cap is included with the kit.
__________________
Current things:
DG skid plate, South Bend S2D clutch w/ SMF, DLC 520 nozzles
Planned things:
RC3, racing stripes
BeetleDragon737 is offline   Reply With Quote
Old February 21st, 2019, 08:56   #5
Rrusse11
Veteran Member
 
Join Date: Jan 2014
Location: PA Deutsch Country
Default

My advice, listen to Jeff. Clean your turbo and check the adjustment.
The spike is the turbo spinning out of control, if the vanes are sticky,
the ECU can't brake it to bring the vanes under control fast enough.

I had the same problem recently, turned out the locknut on the actuator
was loose. Reset to 5psi, no more spikes.
__________________
RC Stage 4: 11mm pump, 17/22, .230 nozzles, 3barMAP,EGR Delete, PD150Intake,2.5" Exhaust: Koni Sp Reds, Wagon Springs, ~1"/2"lift:VR6 fr swaybar, Top strut & rear tie bar: 215/55ZR16 GMax AS05's, 10mm/20mm spacers, 35# @: skid plate: 02J, SBC2 End, .717 5th, Peloquin LSD, Fluidampr: TT Short Shifter: : VR6 fr Brks:
Rrusse11 is offline   Reply With Quote
Old February 21st, 2019, 10:35   #6
BobnOH
not-a-mechanic
 
Join Date: May 2004
Location: central Ohio
Fuel Economy: 50/45/35
Default

I'm confused (happens). You have a boost valve, N75 and you have a throttle. Are you wanting to troubleshoot just the high boost value? I don't believe that value represents anything dangerous, does it set a CEL? Howz it run? You will need to remove the lower engine cover and put the car up to access the actuator, might be worth checking it's operation, maybe evaluate the turbo.
BobnOH is offline   Reply With Quote
Old February 21st, 2019, 11:03   #7
gforce1108
Veteran Member
 
gforce1108's Avatar
 
Join Date: Aug 2006
Location: Newburgh, NY
Fuel Economy: Jetta: 44.5 summer / 47 on snows
Default

Quote:
Originally Posted by BeetleDragon737 View Post
Hmm
I don't have the time/resources at the moment to fight through all the rust to get my turbo off. So with that option out the window...
Regarding adjusting the stop on the turbo, in certain situations moving the stop is the proper treatment, right? Why not here?
I don't think I've ever seen someone need to adjust that stop on an existing turbo. Unless someone messed with it - it shouldn't need adjusting. The turbo I just removed off my 03 was a little sticky and had bunch of play due to wear in the VNT internals.
Quote:
Originally Posted by BeetleDragon737 View Post
And could you explain why the boost valve will allow the boost to creep back up? My understanding is that a certain boost pressure (determined by the spring force) will open the valve. At that point, boost pressure will be sent to the vacuum side of the actuator. This opens the vanes in the turbo, thus decreasing its rpm and the boost it can generate. This is essentially the same thing the N75 does, right? I would assume the boost valve won't close till the pressure drops, so why is it not functioning as effectively as the N75?
Without fully understanding the creep issue you mentioned, is it possible this is a result of using the wrong boost valve? That is, one with an open vent rather than one with the vent plugged?
That kind of boost valve is designed for a wastegated turbo, which the VNT does not have. It gets used in a different manor on a VNT turbo but will only work if the VNT/N75, etc is working correctly already. The N75 is not a ON/OFF only - it is a fully variable vacuum controller so the VNT can be in any position, not just fully one way of the other.
Quote:
Originally Posted by BeetleDragon737 View Post
gforce, thanks for the idea about sending boost pressure to the N75. Is there a chance this will decrease its lifespan?
I've put probably 100k miles with it this way. I still recommend people get their hardware and tune straightened out instead of doing what I did, but it works well for me.
Quote:
Originally Posted by BeetleDragon737 View Post
And if all of this won't stop the boost fast enough, as a last resort, why not just stick a standard pressure relief valve into the lower intercooler hose? Extra boost would get dumped to atmosphere. Obviously this isn't how the system is designed, because the turbo would still be "trying" to generate boost. But does that really matter if the boost is sent overboard? Will the turbo overspeed?
Also, here is the boost valve Kerma sells.
The site says, "The BoostValve has always had a very small vent hole to release any air trapped in the waste-gate line after boost pressure drops... For vacuum controlled waste-gate setups such as the VW VNT turbo use a non-vented cap for a completely sealed valve." I guess I'll contact Kerma to see whether that cap is included with the kit.
If you bleed off boost but allow the turbo to keep trying to make it, you risk overspeeding it. See above about wastegate...
__________________
I hate rockauto.com http://forums.tdiclub.com/showpost.p...&postcount=236
04 Jetta GLS 5sp - EGR delete, RC3, VNT17/22, 3" turbo back exhaust & 2.5" FMIC+PD150 intake. SBC Stage 2 Endurance w/SMF. Eibach lowering springs
gforce1108 is offline   Reply With Quote
Old February 21st, 2019, 13:12   #8
BeetleDragon737
Member
 
BeetleDragon737's Avatar
 
Join Date: Jun 2014
Location: Hagerstown, MD
Fuel Economy: 40.5 MPG
Default

Quote:
Originally Posted by BobnOH View Post
I'm confused (happens). You have a boost valve, N75 and you have a throttle. Are you wanting to troubleshoot just the high boost value? I don't believe that value represents anything dangerous, does it set a CEL? Howz it run? You will need to remove the lower engine cover and put the car up to access the actuator, might be worth checking it's operation, maybe evaluate the turbo.
No check engine light. It runs ok. I haven't checked VCDS for any codes yet. I know that max sustained boost for the VNT-15 is 18.5 psi, so I'm concerned that having overboost at 20+ psi for anything other than a moment will damage my turbo. I'm definitely going to check the actuator operation when I can. My guess is it will stick, so the 5 psi - 18 psi range will probably be more like 10-25 or something.

Quote:
Originally Posted by gforce1108 View Post
That kind of boost valve is designed for a wastegated turbo, which the VNT does not have. It gets used in a different manor on a VNT turbo but will only work if the VNT/N75, etc is working correctly already. The N75 is not a ON/OFF only - it is a fully variable vacuum controller so the VNT can be in any position, not just fully one way of the other.
My understanding of the N75 is a little lacking, but from diagrams posted frequently on the forums, the way I described the operation of the boost valve is correct, yes? It tees into the vacuum line between the N75 and the VNT actuator and ports boost pressure to that line if overboost occurs.
__________________
Current things:
DG skid plate, South Bend S2D clutch w/ SMF, DLC 520 nozzles
Planned things:
RC3, racing stripes
BeetleDragon737 is offline   Reply With Quote
Old February 21st, 2019, 13:32   #9
gforce1108
Veteran Member
 
gforce1108's Avatar
 
Join Date: Aug 2006
Location: Newburgh, NY
Fuel Economy: Jetta: 44.5 summer / 47 on snows
Default

Quote:
Originally Posted by BeetleDragon737 View Post
My understanding of the N75 is a little lacking, but from diagrams posted frequently on the forums, the way I described the operation of the boost valve is correct, yes? It tees into the vacuum line between the N75 and the VNT actuator and ports boost pressure to that line if overboost occurs.
That is correct - search for "dawes device TDI" for better information on how it relates to VNT turbos. But it's still assuming that the VNT is working properly. It doesn't matter how much boost you put to the vacuum actuator if the VNT is sticky. I still can peg my gauge at 35psi sustained if the VNT gets sooted up.
__________________
I hate rockauto.com http://forums.tdiclub.com/showpost.p...&postcount=236
04 Jetta GLS 5sp - EGR delete, RC3, VNT17/22, 3" turbo back exhaust & 2.5" FMIC+PD150 intake. SBC Stage 2 Endurance w/SMF. Eibach lowering springs
gforce1108 is offline   Reply With Quote
Old February 21st, 2019, 13:47   #10
BeetleDragon737
Member
 
BeetleDragon737's Avatar
 
Join Date: Jun 2014
Location: Hagerstown, MD
Fuel Economy: 40.5 MPG
Default

Quote:
Originally Posted by gforce1108 View Post
It doesn't matter how much boost you put to the vacuum actuator if the VNT is sticky. I still can peg my gauge at 35psi sustained if the VNT gets sooted up.
This must be if it is very sooted up, right? If it's a sliding scale, with a little soot, it won't respond quite as fast. But if there's a lot of soot, it won't open the vanes at all, no matter what you do? The idea with the boost valve is to tell the actuator, "NOW", and with the increased pressure against the diaphragm, sticky vanes will yield more easily. Yes?

Kerma's page on the boost valve says this,
"Boost spike can be a major issue with the VW TDI VNT turbo. Back pressure or excess fuel can cause the boost to rise faster than the turbo's vanes can react. With age soot tends to accumulate and cause restrictions in the catalytic converter or exhaust Spike and surge can cause the ECU to react by pulling out timing from the motor, this results in lower torque output. By installing the BoostValve as shown above this excess boost can be prevented.
The BoostValve is not used to raise max boost but to control spike/surge and effectively give better control of the turbo's wastegate. No more surging or dangerous boost spikes." (I'm assuming by "wastegate", they really mean "vane actuator", as the VNT has no wastegate.)

And regarding testing the actuator, if I find that the actuator does not move and stop at the proper vacuum pressure, does that mean my actuator is bad, or does it mean my turbo vanes are sticky? How do I differentiate between those?
__________________
Current things:
DG skid plate, South Bend S2D clutch w/ SMF, DLC 520 nozzles
Planned things:
RC3, racing stripes
BeetleDragon737 is offline   Reply With Quote
Old February 21st, 2019, 14:27   #11
Rrusse11
Veteran Member
 
Join Date: Jan 2014
Location: PA Deutsch Country
Default

Bite the bullet and fix your turbo & actuator. Buy a used one for
$2-300, clean it up, and then swap it out.

You can talk yourself into the Kerma marketing if you want,
but it will only work for a while. Your turbo will grenade,
or just die, from what you've told us, it's already got some
problems.

Good luck with your decision.
__________________
RC Stage 4: 11mm pump, 17/22, .230 nozzles, 3barMAP,EGR Delete, PD150Intake,2.5" Exhaust: Koni Sp Reds, Wagon Springs, ~1"/2"lift:VR6 fr swaybar, Top strut & rear tie bar: 215/55ZR16 GMax AS05's, 10mm/20mm spacers, 35# @: skid plate: 02J, SBC2 End, .717 5th, Peloquin LSD, Fluidampr: TT Short Shifter: : VR6 fr Brks:
Rrusse11 is offline   Reply With Quote
Old February 22nd, 2019, 06:21   #12
gforce1108
Veteran Member
 
gforce1108's Avatar
 
Join Date: Aug 2006
Location: Newburgh, NY
Fuel Economy: Jetta: 44.5 summer / 47 on snows
Default

Quote:
Originally Posted by BeetleDragon737 View Post
This must be if it is very sooted up, right? If it's a sliding scale, with a little soot, it won't respond quite as fast. But if there's a lot of soot, it won't open the vanes at all, no matter what you do? The idea with the boost valve is to tell the actuator, "NOW", and with the increased pressure against the diaphragm, sticky vanes will yield more easily. Yes?
Kerma's page on the boost valve says this,
"Boost spike can be a major issue with the VW TDI VNT turbo. Back pressure or excess fuel can cause the boost to rise faster than the turbo's vanes can react. With age soot tends to accumulate and cause restrictions in the catalytic converter or exhaust Spike and surge can cause the ECU to react by pulling out timing from the motor, this results in lower torque output. By installing the BoostValve as shown above this excess boost can be prevented.
The BoostValve is not used to raise max boost but to control spike/surge and effectively give better control of the turbo's wastegate. No more surging or dangerous boost spikes." (I'm assuming by "wastegate", they really mean "vane actuator", as the VNT has no wastegate.)
And regarding testing the actuator, if I find that the actuator does not move and stop at the proper vacuum pressure, does that mean my actuator is bad, or does it mean my turbo vanes are sticky? How do I differentiate between those?
They are copying someone else's verbiage related to the boostvalve - it looks like there used to be links in there to hooking one up on a VW VNT TDI. The search I recommended on the dawes device will be more relevant to a VNT. It's designed for a little extra insurance, not a "fix".

If you haven't watched some youtube videos on the VNT internals - look them up. I'm not sure that you are thinking about how it works correctly (sounds like you are still thinking more like a wastegate) since you mention it "opening" the vanes. It's just redirecting the internal flow.

As far as mine - If I drive it gently for too long, typically in the winter with snows (it'll spin into 3rd), it gets sooted up. I hook up my trailer (~1000lbs or so total) and take a full throttle run up a long grade. Cleans it right out. The boostvalve does not prevent the overboost.

The VNT actuator is a pretty simple part - 99% of the time it'll work or leak. I have had one be a little crusty inside and still work. It is very easy to tell if you remove the clip and disconnect the VNT arm from the actuator. The VNT should move fully with very little effort. A new OEM actuator is like $115. I haven't bothered with a chinesium ebay/amazon special.
__________________
I hate rockauto.com http://forums.tdiclub.com/showpost.p...&postcount=236
04 Jetta GLS 5sp - EGR delete, RC3, VNT17/22, 3" turbo back exhaust & 2.5" FMIC+PD150 intake. SBC Stage 2 Endurance w/SMF. Eibach lowering springs
gforce1108 is offline   Reply With Quote
Old February 23rd, 2019, 23:26   #13
BeetleDragon737
Member
 
BeetleDragon737's Avatar
 
Join Date: Jun 2014
Location: Hagerstown, MD
Fuel Economy: 40.5 MPG
Default

An update. I checked the actuator under vacuum today. It started moving right at about 4" Hg and stopped moving right around 19". When I rapidly released the vacuum, the actuator arm smoothly extended out again as the pressure increased with no sticking whatsoever. So the actuator isn't the problem. The vanes could have slightly higher friction than desired, so maybe that's causing some boost spikes. But if they do, it's minimal, and it was too cold and wet outside to continue messing around with it.

At the moment, I'm thinking my boost spikes are likely caused by crazy soot buildup in my intake manifold. When my shop cleaned my EGR a few years back, they said there was a ton of gunk in the EGR. If there's buildup in the intake, the flow would be restricted, causing back pressure. I'm not prepared to take that off now either. I'm considering the Dawes device a temporary fix.

Quote:
Originally Posted by gforce1108 View Post
If you haven't watched some youtube videos on the VNT internals - look them up. I'm not sure that you are thinking about how it works correctly (sounds like you are still thinking more like a wastegate) since you mention it "opening" the vanes. It's just redirecting the internal flow.
Here is the video sometimes referenced for the VNT. When vacuum is applied, the gaps between the vanes decrease. Some describe that as closing. When vacuum is released, you could say they open.

Quote:
Originally Posted by gforce1108 View Post
As far as mine - If I drive it gently for too long, typically in the winter with snows (it'll spin into 3rd), it gets sooted up. I hook up my trailer (~1000lbs or so total) and take a full throttle run up a long grade. Cleans it right out. The boostvalve does not prevent the overboost.
If I understand it right, the only reason overboost could still occur with a boost valve is because the vanes are not just "sticky"; they are "stuck". If the vanes are stuck, even with the boost valve open and full boost pressure hitting the actuator diaphragm, the vanes do not want to move. Hence, they will remain in the high boost / closed position and the turbo will produce the maximum boost it is capable of. Does this seem right to you? After you do your full throttle run and blast the soot out, is it still capable of overboosting like this?

After some more reading and looking around, I found this thread describing how oven cleaner can be used to clean soot from the turbo. That would be much easier than taking the whole thing off!

And here's a great tutorial from myturbodiesel on vane/actuator testing, diagnosis, etc.

There's also this massive thread describing a number of causes of overboost, but specifically related to limp mode.

Regarding overboost and limp mode as opposed to boost spikes... Why would a vacuum leak cause overboost? Vacuum is what positions the vanes to create boost in the first place. If there is a leak, that should decrease boost, not increase it, yes?
__________________
Current things:
DG skid plate, South Bend S2D clutch w/ SMF, DLC 520 nozzles
Planned things:
RC3, racing stripes

Last edited by BeetleDragon737; February 23rd, 2019 at 23:31. Reason: Grammar/clarification
BeetleDragon737 is offline   Reply With Quote
Old February 24th, 2019, 04:45   #14
JB05
Veteran Member
 
Join Date: Oct 2005
Location: Il.USA
Fuel Economy: 43/41/40
Default

Lack of vacuum keeps the vanes in the opened, full boost position. At low rpm the vanes will be closed or partially so as shown in your 12 second video. The vanes will open further at higher rpm's as the vacuum will decrease. So if the vacuum is leaking you will get full, over boost at the lower rpm's which you don't want. The actuator on my turbo could not hold vacuum and as a result I was getting full boost at low rpm's which resulted in sluggish performance.
JB05 is offline   Reply With Quote
Old February 24th, 2019, 12:32   #15
BeetleDragon737
Member
 
BeetleDragon737's Avatar
 
Join Date: Jun 2014
Location: Hagerstown, MD
Fuel Economy: 40.5 MPG
Default

Quote:
Originally Posted by JB05 View Post
Lack of vacuum keeps the vanes in the opened, full boost position. At low rpm the vanes will be closed or partially so as shown in your 12 second video. The vanes will open further at higher rpm's as the vacuum will decrease. So if the vacuum is leaking you will get full, over boost at the lower rpm's which you don't want. The actuator on my turbo could not hold vacuum and as a result I was getting full boost at low rpm's which resulted in sluggish performance.
Well, this is confusing. You say the "full boost position" is when the vanes are open. Why do you say that? As this video shows, for a given rpm, closing the vanes will create more boost (that is, higher turbo speed). At low rpm, you want the vanes closed, because you don't have high exhaust flow rate already. Closing the vanes forces the gases through smaller channels and provides that higher flow rate at a more dramatic angle which will drive the turbo speed up. At high rpm, to prevent overboost, the vanes open. This allows the already high-flow-rate exhaust to pass through the vanes without accelerating too much and overwhelming the turbo.

If the actuator cannot hold vacuum, this would lend it to keeping the vanes partially open. Thus, at any engine speed, the boost would be lower than desired, causing sluggish performance. Regardless of rpm, how would full boost cause sluggish performance (unless it triggers limp mode)? Higher boost pressures mean more air is being drawn in, and thus, more fuel can be requested by the ECU while maintaining efficient fuel/air ratios. More fuel should always result in higher power.

What is the misunderstanding here?
__________________
Current things:
DG skid plate, South Bend S2D clutch w/ SMF, DLC 520 nozzles
Planned things:
RC3, racing stripes
BeetleDragon737 is offline   Reply With Quote
Reply


Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
 
Thread Tools

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump

Similar Threads
Thread Thread Starter Forum Replies Last Post
No vacuum on the turbo actuator - full boost or no boost? dalchri TDI 101 3 May 1st, 2012 21:47
New turbo & ECO -> boost spikes! Bryan42 VW MKIII-A3/B4 TDIs 0 February 5th, 2007 20:10
Explain turbo boost spikes donvieira TDI Power Enhancements 9 April 9th, 2006 07:43
Is a Boost Valve Necessary for 22-24 PSI Spikes? PDJetta TDI Power Enhancements 13 December 16th, 2005 13:24
.205's installed, turbo boost ( spikes )seem high auld Atlantic Canada 7 June 15th, 2005 11:23


All times are GMT -7. The time now is 23:35.


Powered by vBulletin® Version 3.8.5
Copyright ©2000 - 2019, Jelsoft Enterprises Ltd.
Copyright - TDIClub Online LTD - 2017
Contact Us | Privacy Statement | Forum Rules | Disclaimer
TDIClub Online Ltd (TDIClub.com) is not affiliated with the VWoA or VWAG and is supported by contributions from viewers like you.
1996 - 2017, All Rights Reserved
Page generated in 0.17320 seconds with 13 queries
[Output: 155.11 Kb. compressed to 132.73 Kb. by saving 22.38 Kb. (14.43%)]