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Discussion Starter · #1 ·
I've been very happy with my VEA D4-engined car since getting it last year, but recently I made a simple tweak which has made me even happier with it, enabling a big improvement in part-throttle pick up and throttle response, especially in the up-to-2,500rpm range.

Having a look under the bonnet of my car, I noticed that the vacuum hose highlighted in the image below was curved at a rather sharp angle:



That hose delivers vacuum to the actuator that controls the bypass valve for the high-pressure (smaller) turbo. At idle, or when there is zero throttle input, the bypass valve is open (no vacuum in the hose). The open bypass valve allows the exhaust gas to flow equally to the high-pressure (smaller) and low-pressure (larger) turbos. This minimises boost pressure at zero throttle to avoid surging and unexpected acceleration.

When you touch the throttle, the solenoid immediately switches the vacuum supply to the hose, in turn applying 'suck' to the actuator, which closes the bypass valve. This diverts all the exhaust gas to the high pressure (smaller) turbo, to rapidly increase boost pressure off-idle. It's this solenoid, hose and bypass valve that governs driveability, throttle response and pick-up in everyday driving conditions up to half throttle and around 3,000rpm.

With the hose curving at a sharp angle, I wondered if it wasn't narrowing or kinking the internal diameter of the hose, reducing the rate of vacuum increase seen at the actuator - and thereby affecting the bypass valve actuation.

The factory-fit hose was a 155mm length of conventional 6mm internal diameter, 11mm external diameter rubber vacuum hose. It's only just a long enough length to fit between the solenoid and the actuator.

I replaced it with a 200mm length of 6mm ID/11mm OD silicon vacuum hose from my local car parts shop. The extra 45mm length is easily enough to allow a nice, smooth rounded curve in the hose with no risk of it narrowing, kinking or getting 'sucked flat' by the vacuum. The factory hose simply pulls off the nipples on the solenoid and actuator, and the new hose fitted simply by pushing it into place on the nipples. You don't even have to remove the engine cover to do it.

Total cost: £1.50 ($2) for a new piece of hose. Total time: 5 minutes. Throttle response is now more sensitive, sharper and more positive around town and on the open road. It was good before, but this has made it better and consistent in all conditions.

Of course, this particular vacuum hose was a just a bit too short on my specific car. Other cars might have a slightly longer piece of hose fitted from the factory, in which case they might not experience any difference from swapping the hose. But I'd recommend that any owner of a car with a D4 VEA motor has a look under their bonnet to check if their car might benefit.
 

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Very nice.
 

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Yes, very nice write-up! Curious, what made you look there? Did you see a kinked hose, fixed it, and noticed better driveability or were you trying to find ways to improve driveability from the start?
 

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Discussion Starter · #4 ·
Yes, very nice write-up! Curious, what made you look there? Did you see a kinked hose, fixed it, and noticed better driveability or were you trying to find ways to improve driveability from the start?
Thanks! Every time I get a new car, I always like to spend a while poking around the engine bay to see what's what, and make sure that things are as they should be (intercooler & boost hose clips properly aligned and tightened, vacuum hoses with nice smooth runs and not getting kinked or trapped anywhere, that sort of thing).

I always find something that could be improved ... after all, the guy on the production line is never going to be as careful about aligning that hose or clamp as an owner would be -- especially if it's getting near a lunch break ;)

Overall, my car was pretty good, and it actually took me a while to look properly at that particular hose, because the factory fits a slip-on mesh protector on it. It always looked a little short to me, but I didn't really see that it was kinking slightly until I removed the mesh. For the price of a beer, it was well worth trying a longer piece of hose :beer:
 

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Great mod and well presented. I hope you don't mind but I've taken the liberty of posting a link to this thread on the VolvoV40club forum where an increasing number of people have the Drive-E D4 in their V40/V40CC.

Tony
 

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Are you D4 VEA engine guys getting EGR related check engine lights as well over there?
 

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Discussion Starter · #8 ·
Are you D4 VEA engine guys getting EGR related check engine lights as well over there?
Yep - loads of them. There's an extensive thread about this issue over at the UK Volvo forums but basically it boils down to this:

- the EGR system is cooled by engine coolant, to help reduce NOx emissions
- the factory-fit EGR cooler seems to be allowing small amounts of coolant to leak into the EGR chamber and mix with the exhaust gases (it's not known if the casting is somehow porous / faulty, or if there's a seal in the EGR cooler which is prone to failing)
- the coolant mixes with the soot in the exhaust gas and makes a sticky, gloopy mess, which causes the EGR valve to stick
- the sticking valve then burns out the electric motor which opens & closes the EGR valve.

This usually throws a Check Engine light, but without limp mode. In the overwhelming majority of cases, the car still drives as normal. Owners that do mostly town / urban driving were getting this issue much earlier than those that regularly cover long distances at highway speeds, as you might expect.

Volvo's original advice was for dealers to remove the EGR valve & cooler, clean it all out and refit. However, in December 2014, they revised this and started fitting new, updated EGR coolers and EGR valves. This implies that the original components had a manufacturing or design fault.

This replacement was done on my own car a couple of months back, and the dealer told me they're doing loads of them. It seems that they are doing this job on pretty much every D4 VEA engine. I've had no repeat of the problem.
 

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Ok, good to hear that they have a proper solution to solve this issue.
 

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Yep - loads of them. There's an extensive thread about this issue over at the UK Volvo forums but basically it boils down to this:

- the EGR system is cooled by engine coolant, to help reduce NOx emissions
- the factory-fit EGR cooler seems to be allowing small amounts of coolant to leak into the EGR chamber and mix with the exhaust gases (it's not known if the casting is somehow porous / faulty, or if there's a seal in the EGR cooler which is prone to failing)
- the coolant mixes with the soot in the exhaust gas and makes a sticky, gloopy mess, which causes the EGR valve to stick
- the sticking valve then burns out the electric motor which opens & closes the EGR valve.

This usually throws a Check Engine light, but without limp mode. In the overwhelming majority of cases, the car still drives as normal. Owners that do mostly town / urban driving were getting this issue much earlier than those that regularly cover long distances at highway speeds, as you might expect.

Volvo's original advice was for dealers to remove the EGR valve & cooler, clean it all out and refit. However, in December 2014, they revised this and started fitting new, updated EGR coolers and EGR valves. This implies that the original components had a manufacturing or design fault.

This replacement was done on my own car a couple of months back, and the dealer told me they're doing loads of them. It seems that they are doing this job on pretty much every D4 VEA engine. I've had no repeat of the problem.
an extensive thread about this issue over at the UK Volvo forums but basically...

It never occured to me that it was "UK" :confused::confused:
 

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V40 D4 VEA - vacuum hose

I've been very happy with my VEA D4-engined car since getting it last year, but recently I made a simple tweak which has made me even happier with it, enabling a big improvement in part-throttle pick up and throttle response, especially in the up-to-2,500rpm range.

Having a look under the bonnet of my car, I noticed that the vacuum hose highlighted in the image below was curved at a rather sharp angle:



I can't upload the picture, can you please post a new? Sounds amazing!
 

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2016 S60 D4 FWD
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I've been very happy with my VEA D4-engined car since getting it last year, but recently I made a simple tweak which has made me even happier with it, enabling a big improvement in part-throttle pick up and throttle response, especially in the up-to-2,500rpm range.

Having a look under the bonnet of my car, I noticed that the vacuum hose highlighted in the image below was curved at a rather sharp angle:



That hose delivers vacuum to the actuator that controls the bypass valve for the high-pressure (smaller) turbo. At idle, or when there is zero throttle input, the bypass valve is open (no vacuum in the hose). The open bypass valve allows the exhaust gas to flow equally to the high-pressure (smaller) and low-pressure (larger) turbos. This minimises boost pressure at zero throttle to avoid surging and unexpected acceleration.

When you touch the throttle, the solenoid immediately switches the vacuum supply to the hose, in turn applying 'suck' to the actuator, which closes the bypass valve. This diverts all the exhaust gas to the high pressure (smaller) turbo, to rapidly increase boost pressure off-idle. It's this solenoid, hose and bypass valve that governs driveability, throttle response and pick-up in everyday driving conditions up to half throttle and around 3,000rpm.

With the hose curving at a sharp angle, I wondered if it wasn't narrowing or kinking the internal diameter of the hose, reducing the rate of vacuum increase seen at the actuator - and thereby affecting the bypass valve actuation.

The factory-fit hose was a 155mm length of conventional 6mm internal diameter, 11mm external diameter rubber vacuum hose. It's only just a long enough length to fit between the solenoid and the actuator.

I replaced it with a 200mm length of 6mm ID/11mm OD silicon vacuum hose from my local car parts shop. The extra 45mm length is easily enough to allow a nice, smooth rounded curve in the hose with no risk of it narrowing, kinking or getting 'sucked flat' by the vacuum. The factory hose simply pulls off the nipples on the solenoid and actuator, and the new hose fitted simply by pushing it into place on the nipples. You don't even have to remove the engine cover to do it.

Total cost: £1.50 ($2) for a new piece of hose. Total time: 5 minutes. Throttle response is now more sensitive, sharper and more positive around town and on the open road. It was good before, but this has made it better and consistent in all conditions.

Of course, this particular vacuum hose was a just a bit too short on my specific car. Other cars might have a slightly longer piece of hose fitted from the factory, in which case they might not experience any difference from swapping the hose. But I'd recommend that any owner of a car with a D4 VEA motor has a look under their bonnet to check if their car might benefit.
Hows it going, I know this message is from 2015 but I recently bought a 2016 S60 D4 and was wondering if you still have this pic so I can identify this hose?
 
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