D5 163 acceleration, flat spot after 3,000rpm?

[abrli]

Hi Guys,

Was having problems with hard acceleration on my D5 and the engine service light used to come up. Had it looked at very quickly at a specialist and computer shows low boost pressure.

However after driving long distance with heavy throttle in the past week, the engine service light doesn't show up again even at full throttle.

The question is, the car's quite punchy all the way upto 3,000 rpm, then after that (especialy when pushed beyond 3,500 rpm) the car seems to hit a soft spot and on uphill climb (speed around 60-65 mph) the car struggles to push past 3,500 rpm.

Is this normal peformance on the 163 bhp D5? It's difficult for me to say cuz I used to drive a 3.2 petrol jag and car absolutely flies at 40mph+ (240bhp).

thx!!

[Blue693]

Not sure if this helps, but have a look at www.polestar.se and select english.....have a look under performance and xc90 and you can check the performance graph for the standard and enhanced versions of the engine.....

When you check the D4 - which is the current 163 hp model, you will see that maximum torque is available up to 3000 revs after which it rolls off quite quickly, although maximum power is rated at 4000 revs......You can see on the graph that there is a drop in torque before the power output reaches peak at exactly the rev range you mention......The lowest point on the graph being at around 3250 revs....

Even with this roll off, the car should not struggle though.....

[abrli]

Not sure if this helps, but have a look at www.polestar.se and select english.....have a look under performance and xc90 and you can check the performance graph for the standard and enhanced versions of the engine.....

When you check the D4 - which is the current 163 hp model, you will see that maximum torque is available up to 3000 revs after which it rolls off quite quickly, although maximum power is rated at 4000 revs......You can see on the graph that there is a drop in torque before the power output reaches peak at exactly the rev range you mention......The lowest point on the graph being at around 3250 revs....

Even with this roll off, the car should not struggle though.....

Thanks! I thought 163bhp should at least get you somewhere, but have to say rather disappointed to see how the torque drops so quickly past 3,000 rpm.

Will have it checked over on Monday regardless, so it's either gonna be a mechanical thing (hopefully problems are with vacuum tubes rather than the turbo itself), or that i'm still getting used to the way this 2 tonne heavyweight drives..

[Thassos]

What year is yours?

[t5_monkey]

Hi Guys,

Was having problems with hard acceleration on my D5 and the engine service light used to come up. Had it looked at very quickly at a specialist and computer shows low boost pressure.

However after driving long distance with heavy throttle in the past week, the engine service light doesn't show up again even at full throttle.

The question is, the car's quite punchy all the way upto 3,000 rpm, then after that (especialy when pushed beyond 3,500 rpm) the car seems to hit a soft spot and on uphill climb (speed around 60-65 mph) the car struggles to push past 3,500 rpm.

Is this normal peformance on the 163 bhp D5? It's difficult for me to say cuz I used to drive a 3.2 petrol jag and car absolutely flies at 40mph+ (240bhp).

thx!!

vacuum leak, dodgy pipe or sensor issue methinks.

Ask the garage to drive another one... see if it 'feels' a lot different - Turbo diesels do run short of puff towards 4k

[gwmckay]

Hi Guys,

Was having problems with hard acceleration on my D5 and the engine service light used to come up. Had it looked at very quickly at a specialist and computer shows low boost pressure.

However after driving long distance with heavy throttle in the past week, the engine service light doesn't show up again even at full throttle.

The question is, the car's quite punchy all the way upto 3,000 rpm, then after that (especialy when pushed beyond 3,500 rpm) the car seems to hit a soft spot and on uphill climb (speed around 60-65 mph) the car struggles to push past 3,500 rpm.

Is this normal peformance on the 163 bhp D5? It's difficult for me to say cuz I used to drive a 3.2 petrol jag and car absolutely flies at 40mph+ (240bhp).

thx!!

Not sure if this helps, but I had my previous car (BMW 330d) dyno'd before a remap and discovered a considerable power drop off after 3000rpm (approx 30bhp below what it should be). It turned out to be the fuel filter which was a cheapish aftermarket one that had only been fitted a few months prior, swapped it out for a geniune BMW one and hey presto! Apparently flow rate wasnt up to scratch at high load.
Other suggestions..possibly air flow meter, or air filter?

[abrli]

What year is yours?

it's a 53 plate

[abrli]

vacuum leak, dodgy pipe or sensor issue methinks.

Ask the garage to drive another one... see if it 'feels' a lot different - Turbo diesels do run short of puff towards 4k

hopefully.. so long as it doesn't need a new turbo, i can deal with a few pipes.

[In Reverse]

Definitely check your fuel filter. I've posted before re my 163bhp XC90 showing all sorts of problems which ended up being an extremely dirty fuel filter, which resulted in dirt getting to fuel metering valve and throwing up fuel pressure fault codes.

I also cleaned out egr valve. It was quite simple job, few bolts etc, albeit messy.

I should also point out that they are under powered, especially with the earlier 5 speed auto box, and definitely wont have the power band that a 6 cylinder petrol car will have.

[abrli]

quick report here guys. had the car looked at today and turned out to be a faulty turbo pressure valve.

will have to take the car out for longer journeys to feel any difference at high speed. :-)