BHW limp mode with FMIC

iwannajettatdi

Veteran Member
Joined
Jun 17, 2003
Location
Salem, OR
TDI
2015 Brilliant Black Audi Q5 3.0TDI, 2014 Tempest Blue metallic Jetta Sportwagen TDI, 2002 Blue Eurovan Weekender BHW TDI
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
 

Mongler98

Top Post Dawg
Joined
Mar 23, 2011
Location
COLORADO (SE of Denver)
TDI
98 Jetta TDI AHU 1.9L (944 TDI swap in progress) I moved so now i got nothing but an AHU in a garage on a pallet.
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
 

Owain@malonetuning

Associate Vendor , w/Business number
Joined
Jul 1, 2016
Location
Vancouver
TDI
PD jetta wagon
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.
 

Nevada_TDI

Top Post Dawg
Joined
Aug 17, 2008
Location
Reno, sort of...
TDI
2001 Jetta TDI
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.
 

Mongler98

Top Post Dawg
Joined
Mar 23, 2011
Location
COLORADO (SE of Denver)
TDI
98 Jetta TDI AHU 1.9L (944 TDI swap in progress) I moved so now i got nothing but an AHU in a garage on a pallet.
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.
 

iwannajettatdi

Veteran Member
Joined
Jun 17, 2003
Location
Salem, OR
TDI
2015 Brilliant Black Audi Q5 3.0TDI, 2014 Tempest Blue metallic Jetta Sportwagen TDI, 2002 Blue Eurovan Weekender BHW TDI
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.


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?


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.



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!
 

Nevada_TDI

Top Post Dawg
Joined
Aug 17, 2008
Location
Reno, sort of...
TDI
2001 Jetta TDI
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.
 
Top