My Octavia A7. Model 2015 1600 cc with 80000km. Does not exceed 150 km/h on gear no 6 even there is more space under the fuel peddal but I can accelerate on the gear no 5 and when it comes again to gear no 6 the speed comes again to 140-150. I checked the computer many times with no errors existed. Also checked fuel pump and air filter and they are good. Could you please if any one knows what’s the problem don’t hesitate to tell me

 

thanks in advance 

 

Mohamed

Hello Mohamed

 

Does your car have the option to set a speed limiter in the menu options?

 

Gaz

If it is a diesel, then speed is restricted to about that during regen.

 

Maybe that's just as fast as it will go

150 km/h is about 94 mph, so I’d guess a 1.6 TDi could go a little faster. If I’m understanding the OP correctly the car seems to hit a wall at 150 km/h in 6th gear, but it will pull faster in 5th gear. Could be that the gear ratio in 6th doesn’t have the engine on the power enough to pull the car any faster but it does in 5th. I have never driven a 1.6 TDi at that speed to tell really. The manual 1.6 TDi’s only have 5 gears in the UK unless they are the Greenline or 4x4 models so I guess the OP’s car is one of those or DSG if that makes a difference.

Most everyday cars will get to their maximum speed in a lower gear. 6th is normally too tall for the engine to reach max power or push through the wind resistance at high speed.

As above - 6th gear is an overdirve

 

 

Even if 6th is an overdrive, it still should be able to maintain the speed that has been reached in 5th gear, even if it can't accelerate from there.

 

Mohamed

How many RPM is it doing in 6th at 150kph?  maybe you are just totally out of the torque curve.

7 hours ago, brad1.8T said:

Even if 6th is an overdrive, it still should be able to maintain the speed that has been reached in 5th gear, even if it can't accelerate from there.

 

Mohamed

How many RPM is it doing in 6th at 150kph?  maybe you are just totally out of the torque curve.

 

If 6th is an overdrive ratio then its perfectly possible that there simply isnt enough power engine available at the rpm its running at.

 

power = torque x rpm

 

Torque at wheels =  torque at flywheel x transmission ratio (less transmission loss)

 

Modern vw engines, max torque is limited and more or less flat throughout the main operating range then drops off at high rpm.

 

If the rpm/torque curve is still on the flat part, 5th will develop more torque at the wheels at that speed due to the gearbox ratio.

 

I had a golf 6 1.6 tdi, 5 speed manual, for several years. the octavia is pretty much the same car. The golf would hit it's speed limiter at 199km/h.

In my opinion, the car should be able to reach at least 190 km/h, even in 6th gear.

 

Has it had a cambelt changed and timing not set up correctly?

There will be nothing wrong with the OP's car. Test work i did in the past showed that stock mainsteam cars were not likely to reach Vmax in the highest gear and almost always reached it in the next one down. If they were able to increase speed in top gear, it required one heck of a lot of time and road distance on the level with the throttle buried to get peak speed. Otherwise a gradual downhill section would need to be utilised as well. Vauxhall used to quote max speed in their brochures along with gear used and expected revs, always was in the slightly lower gear.

 

Gearboxes are over-ratioed in top for fuel economy. Hence if you up the engine output on the standard engine, its rare a new gearbox will need to be fitted or even a new set of ratios installed to prevent hitting the limiter. It will still work adequately. However, if a significant engine power gain is made, then a purpose built/modified gearbox would also be most likely installed to handle the extra load in low gears as well as defining where Vmax occurs for power gain and chosen ratios. Thats a different ball game though.

Having said that my over geared 1.4tsi Superb II with only 125ps , in sixth 1000rpm =30mph so peak power 6000 rpm would be 180mph if you could ever do it - er no!!

However just after I got my car (unfamiliar with it) crusing at 130kph in Germany on a no speed limit Autobahn  in the outside lane passing some slower cars I became concious of a long flashing Merc descending onto me in the outside lane so I squeezed the throttle a bit to push past the line of cars to allow the Merc to pass. I signalled and pulled into the inside lane and wondered why the Merc pulled in behind me - until I looked at my satnav - my little throttle squeeze in sixth had pushed the 125ps overgeared Superb up to 195 kph .

 

So I would expect the original posters car to easily push past 150kph.  I did peviously have a 100ps 1.9pd Superb I that was comfortable at speed but it was not fitted with a six speed box so it's hard to compare.

 

Edited 2 November, 20187 yr by bigjohn

On 01/11/2018 at 14:45, V6TDI said:

Hello Mohamed

 

Does your car have the option to set a speed limiter in the menu options?

 

Gaz

 Hi Gaz,

 

there is is no options for speed limiter. By the way it’s petrol

On 01/11/2018 at 21:56, JamiePvrs said:

Maybe that's just as fast as it will go

Why??? My friends got with their cars about 200 km/ h . Same model

On 02/11/2018 at 00:09, SashaGrace said:

150 km/h is about 94 mph, so I’d guess a 1.6 TDi could go a little faster. If I’m understanding the OP correctly the car seems to hit a wall at 150 km/h in 6th gear, but it will pull faster in 5th gear. Could be that the gear ratio in 6th doesn’t have the engine on the power enough to pull the car any faster but it does in 5th. I have never driven a 1.6 TDi at that speed to tell really. The manual 1.6 TDi’s only have 5 gears in the UK unless they are the Greenline or 4x4 models so I guess the OP’s car is one of those or DSG if that makes a difference.

Hi,

thanks for your reply. My car is not DSG it’s normal gear. The thing that my friends have the same model and they reach to 200 km/h speed without any problems. It’s Automatic transmission 

On 02/11/2018 at 00:12, BigEjit said:

Most everyday cars will get to their maximum speed in a lower gear. 6th is normally too tall for the engine to reach max power or push through the wind resistance at high speed.

Hi ,

Thanks. I know that to achieve the max speed it will be in a lower gear but I am searching for speed lower than the max speed and easy to be achieved with the 6th gear it’s lower than 180 km/h

Scan the car for error codes

19 hours ago, brad1.8T said:

Even if 6th is an overdrive, it still should be able to maintain the speed that has been reached in 5th gear, even if it can't accelerate from there.

 

Mohamed

How many RPM is it doing in 6th at 150kph?  maybe you are just totally out of the torque curve.

At 150 km/h the RPM is 3100 and I think this normal and when it goes to the 5gh gear it can reach to 170km/h at RPM 4000

19 hours ago, brad1.8T said:

Even if 6th is an overdrive, it still should be able to maintain the speed that has been reached in 5th gear, even if it can't accelerate from there.

 

Mohamed

How many RPM is it doing in 6th at 150kph?  maybe you are just totally out of the torque curve.

What does it mean that the 6gh gear is overdrive??

9 hours ago, xman said:

Has it had a cambelt changed and timing not set up correctly?

Good idea And actually I thought about it and checked it again but it was in the right way and I re adjust it again to be sure and try the car and I got the same problem. By the way there is no significant wind resistance during my trials

4 hours ago, BigEjit said:

There will be nothing wrong with the OP's car. Test work i did in the past showed that stock mainsteam cars were not likely to reach Vmax in the highest gear and almost always reached it in the next one down. If they were able to increase speed in top gear, it required one heck of a lot of time and road distance on the level with the throttle buried to get peak speed. Otherwise a gradual downhill section would need to be utilised as well. Vauxhall used to quote max speed in their brochures along with gear used and expected revs, always was in the slightly lower gear.

 

Gearboxes are over-ratioed in top for fuel economy. Hence if you up the engine output on the standard engine, its rare a new gearbox will need to be fitted or even a new set of ratios installed to prevent hitting the limiter. It will still work adequately. However, if a significant engine power gain is made, then a purpose built/modified gearbox would also be most likely installed to handle the extra load in low gears as well as defining where Vmax occurs for power gain and chosen ratios. Thats a different ball game though.

I think you are right but this in case if it reaches to a speed near to the max speed then it will go to lower gear to achieve the max speed. But I am talking about normal speed not near the max speed it suppose that it’s max speed is around 200km/h not 150km/h so according to your notes that it will goes from 150 to 200 on the 5th gear. I think this not good for the engine and even for the gearbox. By the way There is no modifications in the engine or the gearbox they are the original

2 hours ago, bigjohn said:

Having said that my over geared 1.4tsi Superb II with only 125ps , in sixth 1000rpm =30mph so peak power 6000 rpm would be 180mph if you could ever do it - er no!!

However just after I got my car (unfamiliar with it) crusing at 130kph in Germany on a no speed limit Autobahn  in the outside lane passing some slower cars I became concious of a long flashing Merc descending onto me in the outside lane so I squeezed the throttle a bit to push past the line of cars to allow the Merc to pass. I signalled and pulled into the inside lane and wondered why the Merc pulled in behind me - until I looked at my satnav - my little throttle squeeze in sixth had pushed the 125ps overgeared Superb up to 195 kph .

 

So I would expect the original posters car to easily push past 150kph.  I did peviously have a 100ps 1.9pd Superb I that was comfortable at speed but it was not fitted with a six speed box so it's hard to compare.

 

This why I am confused and I think there is a problem with the car but I am not able to find it

By the way the motor is 1600 cc mpi 

8 minutes ago, MohamedElghorab said:

By the way the motor is 1600 cc mpi 

 

Ah - that changes it a bit - is this the old 8 valve 1600 old timer? These are normally fitted with a 5 speed box and have high revs at speed.

 

All engines in the UK are turbo charged. The 1600 should be an over 100mph engine but being normally aspirated gearing could be important.

 

 

 

 

Edited 2 November, 20187 yr by bigjohn