When should I change up?

[joesmad4it]

Just had the best tear up since having my Cupra TDI and it was with an old Fiesta RS Turbo. He was obviously much lighter and therefore my extra 30 BHP or so evened it out and there was nothing in it.

I thought I'd pull at least a few feet on him in the lower revs being a diesel and expected him to pull it back in his higher rev range but that didn't happen at all! Does anyone know at what RPM on a standard Cupra TDI the most torque is and when's best to change gear as I reckon I'm still leaving it too late.

Thanks

 

[thePHILosipher]

its all down to your engine, generally speaking on the derv its around 3500rpm, best advise i can give is stick it on the rollers and see what it comes back with. when the power starts tailing off, thats when to change gear.

this is my graph (as unhappy as it is)

as you can see on mine, the powers almost gone after 3500rpm, so for me thats when best to change up.

PS: dont surprised if this tread gets removed mate, could been seen as street racing bud, just edit the text a bit mate to keep it alive.

 

[chispadete]

err how can changing at 3,500rpm be the best for you when your PEAK power is 3,900rpm!?

 

[joesmad4it]

PS: dont surprised if this tread gets removed mate, could been seen as street racing bud, just edit the text a bit mate to keep it alive.

It's OK it was on a closed road

 

[chispadete]

infact looking at the graph who ever RR'd that was stupid, they let off at 4k!? err you still want to know what powr you have further up dont you? To then look at when to change gear, based on that graph alone, your best bet it to change 4,000rpm. However if you own a cupra tdi your either running the the worst remap in the world, that just increase torque, or something is wrong with those figures.. big time.

 

[thePHILosipher]

yep that was a typo from me was supposed to stick in an 'around'

if you look at the graph again it says FR, im not running a cupra , i only put the graph up to give an idea of a TDi's power delivery

 

[L17KKE]

when im giving it some in my 1.8se i change at about 6k jus before it redlines am i doing the wrong thing to squeeze the most out of the engine as this thread suggests.

 

[thePHILosipher]

when im giving it some in my 1.8se i change at about 6k jus before it redlines am i doing the wrong thing to squeeze the most out of the engine as this thread suggests.

petrols deliver the power differently to diesels

A dervs power is all low down and petrols if im not mistaken is higher up the rev range (and they rev more), the same rule applies tho, when the power starts trailing off, change

 

[knight85]

after about 4k on my remapped FR there is not alot left...i usually change around then

 

[DEAN0]

I was always told that to make the best of a good diesel engine you should be aiming for a gear change point that drops the engine in to the max torque area each time.

So based on the graph below you would want the car to be around 2000 rpm just after the change up to get max thrust forwards.

 

[dirk1978]

I'm fairly confident in my Cupra TDI the best change point is about 5k. The power doesn't drop off a lot until about 5500rpm.

After quite a few (ahem) runs I still keep coming back to that conclusion.

 

[chispadete]

I'm fairly confident in my Cupra TDI the best change point is about 5k. The power doesn't drop off a lot until about 5500rpm.

After quite a few (ahem) runs I still keep coming back to that conclusion.

Really, as the rev limiter would stop you at 5,200rpm give or take, so how do you figure that one out?

Depending on EACH gear's power delivery will depend on at what stage you change gear from that gear to the next. As a rule of thumb, 4k none mapped, 4.5k mapped, 5k hybrid

 

[dirk1978]

Really, as the rev limiter would stop you at 5,200rpm give or take, so how do you figure that one out?

Depending on EACH gear's power delivery will depend on at what stage you change gear from that gear to the next. As a rule of thumb, 4k none mapped, 4.5k mapped, 5k hybrid

Oops yes I've just been out for a drive and realised I mean 4k and not 5k.

 

[thePHILosipher]

Depending on EACH gear's power delivery will depend on at what stage you change gear from that gear to the next. As a rule of thumb, 4k none mapped, 4.5k mapped, 5k hybrid

I think that probably sums it up prettly sweetly, but your only really ever going to no for certain on your car once you stick it on the rollers

 

[chispadete]

I think that probably sums it up prettly sweetly, but your only really ever going to no for certain on your car once you stick it on the rollers

Indeed, the issue there being each gear is different, so youd have to RR each gear.....

 

[joesmad4it]

Nice one thanks everyone. I'm gonna get it booked into AMD next month (as I'm Essex based) for a stage 1 and get in on RR

 

[Trappy]

If you're looking to extract the most straight-line performance you can out of a car, then forget the torque; it's largely irrelevant. You want to focus on the bhp; it's where all of the work is.

The ONLY reason you would change up earlier than the redline in any vehicle, is if the bhp at the change up rpm in the next gear is more than the last few rpms you're given up. The only way you will be able to see this clearly, would be to plot bhp against speed for every gear on a single graph.

This is extremely unlikely to be the case for a petrol engine, but entrirely possible on a diesel.

Before saying you would change up at say 4krpm (1krpm short of the redline for argument's sake), you have to consider that the rpm in the next gear will be a good 800rpm lower than the 'red-line change-up point'. This might very well mean you're off the power and result in you losing straight-line performance.

If someone could give me 'standard' dyno (although it would be nice to do a remapped also) numbers for the car in question, I'd run it through excel, see what it comes up with and post it up. BHP for every 100rpms would be best for accuracy.

Give me;
bhp for every 50rpms,
all gear ratios,
mph/1000rpms for any one gear,
co-efficient of drag,
frontal area,
and weight
... and I'll give you an approximate idea of it's actual performance

Joe, get your car over to tracknroad.com and get a dyno print-out and I'll tell you what she can do

 

[joesmad4it]

Joe, get your car over to tracknroad.com and get a dyno print-out and I'll tell you what she can do

Cool, I'll give em an email and see how much it is. Do you recommend them to do remap too? Would be handy as they are pretty local

 

[Trappy]

A dyno run is £45. After I had mine mapped I asked them to do a run on all 4 boost settings; £50!!

Steve Greenald is a tower of knowledge, I always end up yapping on with him for hours in there. You even get a bit of inside knowledge about up-and-coming Fords. He told me the map for the new Focus RS makes only 270bhp when it's warmed up... Ford wanted it that way

No idea about diseasels mapping though. He was exlaning these new flash type maps and how he does the Mountune stuff for Ford, but he never mentioned diesels. Can't hurt to ask though.

I always recommend them because the rollers seem extraordinarily accurate, most standard new cars making quoted figures, repeatedly.

I've no idea what rollers these mappers use, but some of them seem to be all over the place so I wouldn't trust them.

 

[mymorph]

im with knight on this, my remapped FR peaks about 4000rpm but pulls well to about 4200 so thats when i change. had a little spat with a saxo last night poor thing didnt take well to me pulling well clear up a long gentle hill...