Hi everyone

Here is a question for you all:

Given an unmodded Fabia vRS, what would be the best change up points in gear for maximum acceleration?

I realise all the torque is down low, so is it better to change up in 2nd (say) at 2500 to fall into 3rd at around 1800 revs OR would better acceleration be achieved from changing up at the max power rpm of around 4000, to drop into 3rd at around 3400?

Coming from a petrol car I'm curious to see whether it is better to use the torque in each gear (so there is less time in each gear) or to use the revs in each gear instead?

Any ideas?

I once had a bit of fun with a type R civic and found that I could just keep with it when changing at about 4000RPM. If I let the revs go any higher the Civic would pull away as its engine thrives on the revs.

I know mine is remapped but the VRS diesel engine characteristics are the same.

it takes a bit of getting used to if you come from a revvy multi valve petrol engine but you need to ride the torque curve.

Have fun!!

Change so the revs don't fall back past 3000. In practice this means changing around 3600-4000.

Also, don't come all the way off the throttle during gearchanges. If you keep the revs up, it'll drop smoothly into the next gear without lurching.

Too much of the above though and the intercooler will be overwhelmed, you'll get which will slow you down as the ECU cuts the fuel back.

J.

I think this discussion has been done before and there were two conclusions. The right () conclusion was that you should be changing up at around 4k rpm and this was also the most mechanically sympathetic as you don't put the DMF under max torque on every gear change!

Just drive it like a petrol and you'll be fine

Chris

Disagree - the most efficient way of accelerating is at peak torque and if it was a CVT and held at 1900rpm that would be the best compromise.

Also none of you are considering the big issue of huge noise at those rpms from the TDI unit.

Disagree - the most efficient way of accelerating is at peak torque

Surely it's the power which actually moves the car though, hence changing at peak power would be better? But yes, we have been here before...

Also none of you are considering the big issue of huge noise at those rpms from the TDI unit.

The OP only listed the criteria of accelerating at the quickest pace, not doing so quietly!

Rob.

but it doesn't feel like you're accelerating better at the higher revs.

Disagree - the most efficient way of accelerating is at peak torque and if it was a CVT and held at 1900rpm that would be the best compromise.

Also none of you are considering the big issue of huge noise at those rpms from the TDI unit.

As mentioned though keep changing at 1900rpm and kiss you DMF goodbye.

4k will give best results.

A CVT (old school) would zap up to max revs and speed would catch up. Ever wondered why the redline is at 5(ish)k? Might as well redline it at 2500 so as not to induce too much NVH

Changing up that early at WOT shows a certain lack of mechanical sympathy :haha:

Audi Multitronic (CVT) boxes rev like mad when changing up then settle down to a low rev. But tap the throttle again and the revs go back up very quickly.

So much for 1900 rpm if you want to accelerate then

gotta be 4k.......

Deffo 4k, aim to keep 3k+ when changing it up.

Remapped it depends on my mood, but with my current setup I go up to 5k or a shade below if I really want to go for it. Remember torque is great but the torque that matters is that at the wheels, and when you use that torque converter called the gearbox, you'll find the higher the gear, the less torque ends up relatively at the wheels

I usually aim for about 3.5k to change up, then it drops back to 2.5k-ish in the nest gear, ready to ride the torque wave. The uprated clutch helps enormously with this style of driving (The standard one died due to me driving like this!) lol

Disagree - the most efficient way of accelerating is at peak torque and if it was a CVT and held at 1900rpm that would be the best compromise.

Also none of you are considering the big issue of huge noise at those rpms from the TDI unit.

He wanted fastest acceleration though. No limits were put on noise... or even NOISE!

J.

He wanted fastest acceleration though. No limits were put on noise... or even NOISE!

J.

Yes, fastest acceleration irrespective of engine noise, stress on components, engine life etc.

I was thinking that it would either be:

1. use the torque, so if max torque is (somewhere) around 2000 then after this point the torque curve falls (while the power curve is still rising) so change up around 2000 so the next gear falls into (approx) 1600-1800

OR

2. use the power like I did in the petrol, which means revving up to 4000, the only problem I can see being that changing up to the next gear then results in the revs dropping to say 3000, which is beyond peak torque (but not peak power)

My petrol car was an Accord Type R where peak power was 7200!!

Blimey... I may have to adjust my driving style then. I usually change up quite early and feel the torque (as said, it FEELS faster)... so this isn't good then?

Peak BHP on the TDI is at something like 4,700 rpm, wheras peak torque is about about 1,900rpm. IMO changing at about 3,500 to 4,000rpm is the best of both worlds as you keep the turbo on the boil and keep within the best power band. Allowing the revs to drop too low during a gear change will not only kill the DMF but also give you lag before the turbo spools up again and off you go.

You need pikey mod no 1 for this though to keep the SMIC from suffering too much heat soak.

An engine CANNOT accelerate faster than when it makes peak power. Fact, fullstop.

Where does the Fabia make peak power?

Power is BHP as far as I'm aware Power is the combination of torque and revs so must be BHP. That means it's about 4,700rpm. Or something.

Fab vrs redlines at just over 4k though... lol

Power is BHP as far as I'm aware Power is the combination of torque and revs so must be BHP. That means it's about 4,700rpm. Or something.

I think peak is around 4.1k rpm (according to Skoda's published figures) so around this would seem the optimum change point

Chris

Nope, peak power is at 4000rpm, redline at 5000rpm.

Nope, peak power is at 4000rpm, redline at 5000rpm.

Agree. 130BHP @ 4000RPM, so no need to go above that:thumbup:

Ah ok, 4k rpm. nice. In which case the 'change at 4k' statements are spot on.

Thing is though, on some cars they made it so that a longer gear made the sprint to 60 a little quicker. Take the Pug 106 GTi and the Saxo VTS....effectively the same car with the same engine, just slightly different boxes. The Saxo can do 60 in 2nd whereas the the 106 can't and so that made the 0-60 dash a bit quicker as there's no change to 3rd. This is where the CTR excels....it can rev high and so fewer gearchanges are required which slow you down.

Gearchanges are the killer for 0-60 sprints, hence why diesels are cr4p at it. They need to be changed so often.