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TDI Power Enhancements Discussions about increasing the power of your TDI engine. i.e. chips, injectors, powerboxes, clutches, etc. Handling, suspensions, wheels, type discussion should be put into the "Upgrades (non TDI Engine related)" forum. Non TDI vehicle related postings will be moved or removed. Please note the Performance Disclaimer.

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Old June 2nd, 2019, 15:13   #1
iwannajettatdi
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Default BHW limp mode with FMIC

I've got a 2004 BHW in my 2002 eurovan. All of the turbo tubing and intercooler piping had to be fabbed up. It ran fine when still in the passat before my swap. My issue is a limp mode that comes on when over 2400rpms or so, or any sort of sustained throttle driving when cruising. I've been able to lessen it by tightening up all of the joints and making sure there aren't any boost leaks. It also helped quite a bit by adjusting the turbo actuator rod so it doesn't make as much boost, but, it's slow now. really slow.

I'm wondering if there is an issue with using a front mounted intercooler and the length of piping that is involved. Is this enough to cause surges or enough lag to cause issues with the MAP sensor and cause a limp mode? The sensors are stock, the turbo is stock. I've got a Malone 1.5 tune with immo and EGR delete and a cold weather idle increase.

What scans from VAG-COM would be helpful here to help diagnose an issue? Any thoughts on what could be causing it? Do I need a SMIC instead of the FMIC?

Thanks.

-Ryan
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2002 Eurovan TDI BHW 02d syncro project - The Adventure Bus
2014 MK6 JSW, DSG, 33k miles -
2011 MK6 Golf, 6MT, 120k miles - Just emissions fixed
Gone-2006 V10 Touareg TDI
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Old June 2nd, 2019, 18:07   #2
Mongler98
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Turbo lag, NO your confused, Turbo lag is a latency in time that it takes the turbo to make full boost or an operating boost from an idle to its boost curve in RPM

Spool Lag, Maybe (i think thats what you mean)
Spool lag is the delay in time for the turbo to make boost between deceleration or changing gears, not from idle.

2 completely separate issues and common ways to solve them.

What boost are you making, and at what RPM, and waht size BAR MAP do you have. possible that now that your engine is in a heaver vehicle that its making a boost spike or issues with full load.

The best thing to do here is take a bit of logging and post the graphs here.

i highly doubt that the FMIC would cause any issue, its highly possible you have a boost leak.

Pressurize the system with smoke and find the leak.
see waterbong
oh lord not again lol
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Old June 2nd, 2019, 22:02   #3
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vcds measuring block 11 for drive cycles to replicate the limp mode would be best, it will show actual boost vs requested along with the N75s behavior. Roughly 1500-4000 wide open and some variable hard driving will give you a good idea of behavior, then you can accurately adjust the actuator.
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Old June 4th, 2019, 07:56   #4
Nevada_TDI
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You don't mention if you are tuned or not, but it is not at all uncommon to have turbo issues with a FMIC. Think of it this way: a compressor in your garage produces less CFM at higher PSI, than it does at a lower PSI setting. Your turbo is designed to produce x-number of pounds of air (CFM, sort-of) at a given pressure. The more piping that is installed, the less potential for "full boost" pressure there will be.
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Old June 4th, 2019, 18:44   #5
Mongler98
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Quote:
Originally Posted by Nevada_TDI View Post
You don't mention if you are tuned or not, but it is not at all uncommon to have turbo issues with a FMIC. Think of it this way: a compressor in your garage produces less CFM at higher PSI, than it does at a lower PSI setting. Your turbo is designed to produce x-number of pounds of air (CFM, sort-of) at a given pressure. The more piping that is installed, the less potential for "full boost" pressure there will be.
PV=NrT

TLDR:
its not the loss of PSI or CFM, as thats not an issue in these systems, its the ECU demanding boost at specific RPMs within a specific time, key work Specific time.
Get a tune if you dont have boost leaks or up the boost a few ticks and use an absolute gauge to dial it in.
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Old June 7th, 2019, 20:10   #6
iwannajettatdi
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Quote:
Originally Posted by Nevada_TDI View Post
You don't mention if you are tuned or not, but it is not at all uncommon to have turbo issues with a FMIC. Think of it this way: a compressor in your garage produces less CFM at higher PSI, than it does at a lower PSI setting. Your turbo is designed to produce x-number of pounds of air (CFM, sort-of) at a given pressure. The more piping that is installed, the less potential for "full boost" pressure there will be.
Malone stage 1.5 tune, the shop told me 160-165bhp. No dyno tests as of yet. Also have 2.5" piping. But I'm not happy with it, so a rework is planned.


Quote:
Originally Posted by Owain@malonetuning View Post
vcds measuring block 11 for drive cycles to replicate the limp mode would be best, it will show actual boost vs requested along with the N75s behavior. Roughly 1500-4000 wide open and some variable hard driving will give you a good idea of behavior, then you can accurately adjust the actuator.

Block 11, got it. I've got an egt and boost gauge finally ordered and on the way. Should the boostgauge measure post intercooler or just before it goes into the head?


Quote:
Originally Posted by Mongler98 View Post
Turbo lag, NO your confused, Turbo lag is a latency in time that it takes the turbo to make full boost or an operating boost from an idle to its boost curve in RPM

Spool Lag, Maybe (i think thats what you mean)
Spool lag is the delay in time for the turbo to make boost between deceleration or changing gears, not from idle.

2 completely separate issues and common ways to solve them.

What boost are you making, and at what RPM, and waht size BAR MAP do you have. possible that now that your engine is in a heaver vehicle that its making a boost spike or issues with full load.

The best thing to do here is take a bit of logging and post the graphs here.

i highly doubt that the FMIC would cause any issue, its highly possible you have a boost leak.

Pressurize the system with smoke and find the leak.
see waterbong
oh lord not again lol
I'm worried I still have a boost leak too. I know as I've been buttoning up all the small leaks it's definitely running better. I still have the stock MAP sensor, and a mild stage 1+ tune from malone. Still have the stock vnt-17 turbo on the BHW. I'll try and grab some logged runs in the next few days, working nights the next few.



Quote:
Originally Posted by Mongler98 View Post
PV=NrT
TLDR:
its not the loss of PSI or CFM, as thats not an issue in these systems, its the ECU demanding boost at specific RPMs within a specific time, key work Specific time.
Get a tune if you dont have boost leaks or up the boost a few ticks and use an absolute gauge to dial it in.
The tune is there. Had to delete the immo and get the auto to manual maps loaded. I wonder if it could be related to that? As above, the gauges are coming, should be here Monday. It might take a bit to get them in though. I'll get lots and post up what I find.

Thanks, folks!
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2002 Eurovan TDI BHW 02d syncro project - The Adventure Bus
2014 MK6 JSW, DSG, 33k miles -
2011 MK6 Golf, 6MT, 120k miles - Just emissions fixed
Gone-2006 V10 Touareg TDI
DEAD-99.5 A4 Jetta, 349,919 miles RIPieces
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Old June 9th, 2019, 16:57   #7
Nevada_TDI
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I understand the Ideal Gas Law, but that is not relative here. If you look at the turbo compressor plots, a given turbo will produce only so many pounds of air at a given pressure and RPM. Asking the turbo to provide more pounds of air at the same pressure is a losing battle using a stock size turbo.
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2001 Jetta GL TDI, Tinted, Vented, No Kitty, EGR-ectomy, TDTuning, HIFLO .216's, TurboLabAmerica Hybrid 15-17/56, VCDS Hex+CAN, S-B Daily Driver 2 Clutch, DG Short Shifter, Frostheater, Baldwin Fuel Filter, Koni Orange, New Paint. Previous Diesel: 1983 Rabbit Diesel
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Old June 9th, 2019, 21:31   #8
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would put the boost line at the egr delete port, can compare values to MAP as well that way.
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Old June 10th, 2019, 18:09   #9
QuickTD
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I've set up quite a few B7 audi A4's with BHW TDI's and have used the stock B7 dual side mount intercoolers, no problems. There must be 10 feet of pipe plus the 2 intercoolers. I think you either have a boost leak or low vacuum to the N75 valve. If you're getting limp mode you should be getting a code, either under or overboost.

Also check that the N75 is connected to the correct plug on the harness, the CCV heater uses the same type plug and they are easily transposed. This will cause near instant limp at any steady throttle, don't ask how I know...
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