What's happening to my top speed?

[JakeC7R]

I'm sorry in advance if this would be better posted in the Tuning sub-forum, but I knew it'd get plenty of eyes here.

I don't really tune myself. I just take other tunes posted here and tweak them to the PP requirements that I want. In the process of doing this, transmission setups don't always translate to having more or less power than was initially intended.

Because of this, I've been having some issues with the top speed on some of my cars. With default gears, the car will typically redline and hold its top speed over a long distance (such as the Mulsane Straight at Le Mans). However once changes get made, I've been having an issue with cars redlineing, hitting top speed, and then suddenly losing 5-7 MPH before accelerating again to redline. This repeats until I let off the gas for a corner.

So why is this happening? Is it because the top gear is unreachable for the car at certain final gears?

 

[Streeto]

It's done this since GT1 as far as I recall.

 

[CBH]

I'm sorry in advance if this would be better posted in the Tuning sub-forum, but I knew it'd get plenty of eyes here.

I don't really tune myself. I just take other tunes posted here and tweak them to the PP requirements that I want. In the process of doing this, transmission setups don't always translate to having more or less power than was initially intended.

Because of this, I've been having some issues with the top speed on some of my cars. With default gears, the car will typically redline and hold its top speed over a long distance (such as the Mulsane Straight at Le Mans). However once changes get made, I've been having an issue with cars redlineing, hitting top speed, and then suddenly losing 5-7 MPH before accelerating again to redline. This repeats until I let off the gas for a corner.

So why is this happening? Is it because the top gear is unreachable for the car at certain final gears?

This would be better posted in the turning forum because the top turners will help you out. 👍

 

[PsuPepperoni]

It's the rev limiter.

 

[Polsixe]

I'm sorry in advance if this would be better posted in the Tuning sub-forum, but I knew it'd get plenty of eyes here.

I don't really tune myself. I just take other tunes posted here and tweak them to the PP requirements that I want. In the process of doing this, transmission setups don't always translate to having more or less power than was initially intended.

Because of this, I've been having some issues with the top speed on some of my cars. With default gears, the car will typically redline and hold its top speed over a long distance (such as the Mulsane Straight at Le Mans). However once changes get made, I've been having an issue with cars redlineing, hitting top speed, and then suddenly losing 5-7 MPH before accelerating again to redline. This repeats until I let off the gas for a corner.

So why is this happening? Is it because the top gear is unreachable for the car at certain final gears?

You have to increase your top speed setting or reduce the final gear ratio. Ideally you should be just bouncing off the rev limiter at the end of the longest straight.

 

[HBR-Roadhog]

Yep, basically you are running out of gear before you reach what could be the top speed of the car so the rev limiter kicks in and drops the rpm of the engine for a beat. You need to alter the gearing if you want more speed.

I would say that you should not be bouncing off the rev limiter on the track you want to run on but ideally you should be very close to it at the end of the longest straight. There are some exceptions though. I have tested a few cars that turn faster laps with lower gearing on some tracks even though they may be bouncing on the limiter down a good portion of the longer straights just due to the added acceleration on sections where they can not reach the limiter.

 

[FoRiZon]

It's the rev limiter.

Captain Obvious here.

Happen IRL too.

You dont want a crankshaft jump straight through your bonnet, wouldn't you?

 

[JakeC7R]

Thanks for the answers. I have a little bit better understanding of the gearbox now.

 

[jimantonic]

I recall many moons ago during a GT5 WRS week featuring the Merc Sauber C9 at Le Sathe being told by one of the tuning guru's to try as best you can to set your gearing so you reach your top speed on the straight when the RPM is at peak power according to individual car stats.
Might be of some use to you.

 

[eran0004]

As you get closer to the rev limiter you can lift the throttle slightly, this will allow the engine to go a bit higher on the rpm before the rev limiter kicks in. So if your car hits the rev limiter at, say, 250 km/h when you go full throttle, you might be able to reach 255 km/h if you only go half throttle (provided that the engine still have enough power to get you there).

 

[giorgos21]

It's the rev limiter.