A £1.50 engine upgrade for D4 VEA owners

[The Tinkerer]

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, improving part-throttle pick up and throttle response, especially in the up-to-2,500rpm range.

Having a look under the bonnet, 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 as there is 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 low rpm / zero throttle.

When you touch the throttle, the solenoid switches the vacuum supply to the hose, and the actuator closes the bypass valve. This diverts all the exhaust gas to the high pressure (smaller) turbo, to quickly increase boost pressure off-idle. It's this hose and bypass valve that basically governs driveability and throttle response in everyday driving conditions.

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 - thereby affecting the bypass valve actuation.

The factory-fit hose is an approx 15cm length of conventional 6mm internal diameter, 11mm external diameter rubber vacuum hose. It's only just long enough to fit between the solenoid and the actuator.

I replaced it with a 20cm length of 6mm ID/11mm OD vacuum hose from my local car parts shop. The extra 5cm length is easily enough to allow a nice, smooth rounded curve in the hose with no risk of it narrowing or kinking. The factory hose simply pulls off the barbed nipples on the solenoid and actuator, and the new hose fitted simply by pushing it in place. You don't even have to remove the engine cover to do it.

Total cost: £1.50 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 even better.

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

[Flux]

Thanks for that info..............only would that be classed as a modification and (potentially) invalidate warranty?

I know that might sound a little daft as you haven't effectively 'modified' any aspect of the telemetry but you know how any excuses can be given sometimes ..... .

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A few minutes later.............the post just reminded me that I need to add some screen wash. Had a look but my engine doesn't look anything like the one on the picture (OK I know it's got an engine cover) so will be leaving mine well alone as would probably end up doing something fatal and the tortoise might return...and not leave....or tell the dealer I've been 'tinkering'.....just like The Tinkerer!

[The Tinkerer]

Originally Posted by Flux

Thanks for that info..............only would that be classed as a modification and (potentially) invalidate warranty?

I know that might sound a little daft as you haven't effectively 'modified' any aspect of the telemetry but you know how any excuses can be given sometimes ..... .

Simple - keep the original factory piece of hose and swap at service time.

Also, the above pic shows the engine from the rear (i.e. from the side nearest the bulkhead). I will try and get an underbonnet picture that highlights where the hose is, but it's fairly easy to find. It's at the back of the engine bay, just behind the top right-hand side of the engine cover as you look at it with the bonnet open.

[Gilesme]

impressive !

from the pick above i wonder if the tube is so short and kinked to meet a height restriction for a certain installation ?

[The Tinkerer]

Originally Posted by Gilesme

from the pic above i wonder if the tube is so short and kinked to meet a height restriction for a certain installation ?

Even with my custom 5cm longer hose, it's still lower than the top of the engine cover so there's loads of clearance all around, both under the bonnet and from the bulkhead.

I believe it's simple cost-accounting by Volvo - using the minimum amounts of material possible.

[The Tinkerer]

A quick update for anyone interested in this little mod. I did it 3 weeks ago and it really has noticeably improved driveability and pickup in all conditions - urban / town driving and open-road / motorway.

I measured the factory-fitted hose that I removed from mine and it is 15.6cm in length, which was just a bit too short to connect the vacuum solenoid to the actuator without a sharp curve.

I firmly believe that when vacuum is switched to the hose (which only happens when you touch the throttle), the sharp curve in the hose was sometimes being tightened by the sucking action, restricting the vacuum seen at the actuator.

My replacement silicon hose (6mm ID, 11mm OD) is 20cm long, making a nice smooth curve.

[volvorocks]

Thought I would bump this thread as it is interesting and useful.

Regards

[GMcL]

The reason being ? The ongoing turtle message.

[volvorocks]

Yes hence why I linked to it, and as post #7 plus when I first read it I thought 'interesting that,worth remembering for a later date'

Regards

[RoyMacDonald]

Originally Posted by The Tinkerer

Even with my custom 5cm longer hose, it's still lower than the top of the engine cover so there's loads of clearance all around, both under the bonnet and from the bulkhead.

I believe it's simple cost-accounting by Volvo - using the minimum amounts of material possible.

Computer probably said it was long enough. They are not owned by Ford anymore.