Short TCV hoses = Improved boost control Topic is solved

[MadeinGhent]

Boost control issues / TCV hose routing

Summary:
Shorten your TCV hoses. This will improve the ECUs ability to control the wastegate. Improving the ECUs abuility to control the wastegate will prevent erratic boost control behavior and may enable you to run more wastegate preload resulting in faster boost development. This may be particularly relevant if you have a quick spooling and large turbocharger that is already pushing the limits of what the ECU can control.

Introduction:
I have been a lurker on the MVS forums for a long time and have gathered much valuable information from the community, I recently had a tricky boost control problem that I wanted to pass on to the community, hopefully someone can learn from my experience.

Background info:
I am running a TD04HL-19T turbo with billet compressor wheel and 11 blade exhaust turbine. This turbo was built by myself from parts sourced from various places. The car has some intake and exhaust mods. R manifold, 3inch everything, blah blah… The intercooler is stock but everything else air passes through has been upgraded. I have installed green injectors and a custom ARD tune to match the increased airflow. The car currently has forged h-beam rods that I installed during an unscheduled rebuild. (Test fuel injectors before installing!!, one of the greens I installed had a steady drip that filled cylinder #2, this hydrolocked the engine and bent connecting rod #2) I have been running the car for approximately one month after the rebuild. This car has not been run before with this tune or hardware configuration.

The problem:
The car would develop 15 pounds of boost very quickly, drop immediately to 10 PSI, and then slowly build back up to 15PSI. Every time I floored it the car would “stumble” and then slowly recover as the power would build back up to where it should be. I believe the ECU was dumping boost as a result of the boost building too quickly at an uncontrollable rate. My first suspicion was that the turbo was building pressure faster than the ECU could open the waste-gate to keep things in check.

Possible causes:
My research indicated that the most likely cause for this behavior was a waste-gate that was set with too much pretension. Consulting with Lucky at ARD confirmed that this was the most likely cause. With this confirmation in hand I attempted pretension settings from 2.2 Psi up to 7 Psi without any luck.

Resolution:
I had mounted my ARD TCV in the factory location and run new blue silicone hose back to the turbo. The new hose was stowed in the factory retainers near the PCV hoses to help keep the engine bay neat and organized. Mounting the TCV in the factory location and running the hoses via the factory routing resulted in hoses that were approximately 3 feet long. I have relocated the TCV under the crank position sensor and shortened the hoses. The results have been dramatic.

Current situation:
After shortening the TCV hoses I saw an immediate change in the cars behavior. The car was building boost VERY slowly for the first few pulls while the ECU relearned how to operate the TCV. After several pulls the car now goes directly to 15 PSI and holds it steady. I was even able to tighten the wastegate a few turns without getting any spiky behavior.

Happy Volvoing

- Kyle

[precopster]

Interesting find. I have a friend with a stock T5 who has trouble maintaining boost and almost totally loses boost above around 2,500 rpm.

He has a IPD TCV. He has tried a stock TCV. He tried everything including wastegate adjustment. He's was about to have a tune for his ECM to see if that would help.

[jonslave]

This solved my irregular boost problem. After installing a new TCV that I moved up and out of the hot area under the airbox with longer hoses in my 850R I noticed the car would overboost and not function correctly. After taking 18 inches out of the fresh air hose and almost a foot out of the wastegate and turbine hoses the car is way more responsive and boosts as it should.

[Mike Langlois]

Just found this. I am in the middle of upgrading with bigger turbo, intercooler, green injectors, exhaust, TCV, Blah, Blah, Blah. I think I will install the IPD TCV over some where near the crank position sensor, with shorter lines. I just placed the IPD TCV in the stock position, but have not installed (or cut) the hoses yet....
Manic Mike

[cleven]

I redid all my vacuum lines on my V70 and not knowing made them shorter and noticed a difference