[sammyboy]

Started wondering if there is a problem with my car after today's high speed run through Espagna.

Can anyone confirm if this is normal for a MKIV PD150 with REVO. Get to 120 and car will not accelerate any more- on the flat. Just puts on a few MPH very, very slowly indeed (like 30 seconds to reach 130 from 120). Very strange considering the top end is meant to be more like 130. 130 was only achieved with the benefit of a downhill run. Speedo indicated 140 but GPS confirmed that 134 was the true figure.

All my previous cars (petrol) seemed to be able to reach their max speed much quicker. Pretty peeved really if this is all the performance I can expect at the top end. I don't mind 130 or so but would like to be able to reach it within an acceptable time.

On an up note I was cruising at 110mph and saw a 36mpg average, not bad really. All this over roads that Autocar described as the "craziest motorway in the world"- think hairpin bends, fast sweepers and nobody giving a toss what speed you drive at- I overtook a police car at 110 for example.

 

[budgie]

maybe the cars still tight ..mines limbering up more and more and i had it serviced yesterday ...ist variable(21000 miles) and its a lot looser...only a theory...although my RA 2 has shown 134 too on the flat in germany ?

who knows ..maybe more pd150 owners can shed some light

 

[micky 32]

could be maf problem? it depends on your bhp, as i recall did you not have a scooby with 300bhp?? no wonder you had better top end.

 

[Reflex TDI]

Sounds a bit odd. Mine is Superchipped not Revoed but doesn't need a hill to max out. 145 indicated, 141 GPS. Sure, it slows after 120 but you are losing torque in the higher rev tange. With all this cold air about the car seems gagging for it at the moment.

 

[NikB]

Doesn't seem right to me. I've done around 142-143 indicated and my speedo is only 1-2mph out at that speed. That speed also wasn't flat out I just didn't have any more road to go faster.

Know what you mean about the car gagging for it James. I've been having great fun when it's dry.

 

[sammyboy]

Was just pointing out this thread to my girlfriend and she made an interesting point.

The car was fully laden (with some really heavy stuff), perhaps that had something to do with it?

[]

Stupid me[:I], perhaps I'll update this thread with the unladen top speed when circumstances permit.

 

[NikB]

Nope shouldn't matter. Being fully laden will have an impact on acceleration but should have a minimal effect on potential top end speed. I'd certainly not expect it to knock 20mph off the top end.

 

[sammyboy]

That's the point exactly, the car just seemed to top out but if I'd had the space perhaps it would have got up there eventually. It was so slow to put on speed after 120 I'd describe it as like wading through treacle.

I intend to find out just what the car can do next time I get on a smooth arrow straight autovia or autoroute and will reprt my findings.

 

[Haddock]

Sounds exactly like the problem I had with my Tdi 110, and a new MAF cured it... Got a 150PD like you now and I asked my dealer to change it while still in warranty to be safe.

Certainly the car should pull swiftly to 130, and then gain the last 10 or so slower. (indicated speeds)

Chris

 

[Richard]

I'd mimick Reflex and Nick B's comments, with my Jabba.

Had a little fun with a clio 172 yesterday, showed 135 on Road Angel with out too much fuss.

Have you noticed anything else which might indicate a problem, lower down the speed range?

 

[sammyboy]

Gonna run vag-com on it today and see if it throws up any errors.

Then road test on the way back from work, here's hoping the gendarmes don't catch me.[]

 

[nrgizerbunny]

if your car is fully laden you Won't be able to travel as fast, the rolling resistance of the tyre is proportional to the load on the tyre. So if you increase the weight of the car then the rolling resistance increases. However the difference in rolling drag is small in comparison to to the aerodynamic drag.

sammy, also make sure you were in 4th gear. Gears 5th and 6th in the golf are economy gears, you get maximum speed in 4th -> this is what ford use and i don't think that the other car manufactuers vere much away from this.

 

[sammyboy]

OK ran vag-com no error codes. So took it for a blast down the autoroute.

Results different this time- accelerated well to 130 and then I ran out of road.

Difference was- 4 17" alloys, 8 cases of wine, a few cases of beer,pallet of Vimto (my girlfriend is addicted to the stuff and we can't get it here)and my luggage removed from the car.

Can't wait to try out the top end when I have more road to test it on.

Seems that a fully laden car suffers a bit!

 

[Haddock]

Quote: posted by nrgizerbunny on 09/03/2005 10:01:24

if your car is fully laden you Won't be able to travel as fast, the rolling resistance of the tyre is proportional to the load on the tyre. So if you increase the weight of the car then the rolling resistance increases. However the difference in rolling drag is small in comparison to to the aerodynamic drag.

sammy, also make sure you were in 4th gear. Gears 5th and 6th in the golf are economy gears, you get maximum speed in 4th -> this is what ford use and i don't think that the other car manufactuers vere much away from this.

Maximum speed in 4th Gear?? What?!

 

[sammyboy]

Should add that at 130 if you put in 4th you'd be bouncing off the limiter.

 

[Spin 150PD]

I'd have to mirror Reflex comments, my superhipped 150 'stormed' to 130 with ease and onto the 140 mph mark without too much trouble, did this on a few occasions and the terminal speed was due to running out of road & bottle[:I]

Now my wifes 130 Bora Tip accelarates pretty well up to the 115mh mark then struggles to get to about 120 so perhaps I should get this checked although she is unlikely to find this out for herself[!]

 

[dc]

Quote: posted by nrgizerbunny on 09/03/2005 10:01:24

sammy, also make sure you were in 4th gear. Gears 5th and 6th in the golf are economy gears, you get maximum speed in 4th -> this is what ford use and i don't think that the other car manufactuers vere much away from this.

[?]

 

[nrgizerbunny]

Manufacturers design their cars to achieve max speed in 4th gear (5 speed transmission) or in the case of vag 6 speed it appears to be 5th gear (I haven't been that fast!). the "top" gear is there for fuel efficiency only. if you do a search for arithmatic and geometric gear ratios you will see the plots of this.

if you think about it, if your car engine did not have a rev limiter, it would have max speed in 1st gear because you have max torque. the gear ratio difference between 5th and 6th gears is so small, 5th gear will result in higher speed because you have more torque at the wheels.

i could do the mathematical proof if anyone was that curious

 

[Jiiim]

if your car engine did not have a rev limiter, it would have max speed in 1st gear

Didnt quite think that all the way through before posting, eh? [:I]

 

[nrgizerbunny]

no i stand by what i said, if you have a car with no rev limiter and stick it in 1st gear you WILL go faster than if you were in 5th because there is more torque at the wheels in 1st.