HDi to rev higher...

any factors that affects it for you to come to such a conclusion..???
 
It is to do with the way diesel burns. Once the piston crown is moving down at the same speed as the flamefront then there's no more revs.

But you are getting a usable slug of torque from below 1500rpm all the way up to, say, 4500rpm.

The HDi 16 valve I had was red-lined at 5300 - very high for a diesel. And pointlessly so.
 
It is to do with the way diesel burns. Once the piston crown is moving down at the same speed as the flamefront then there's no more revs.

Is this due to the higher compression available on diesel engines...?
 
Not really, it's to do with the fact that diesel is a slower burning fuel that petrol. The massive torque outputs are due to what's known as high BMEP, which is brake mean effective (cylinder) pressure.

THere's not a lot you can do to increase the peak revs of a diesel engine, and if you do it's usually not beneficial to performance anyway.

But you should have plenty of go between 1500rpm and 4500rpm.
 
I think if you decreased the displacement you could get it to rev faster =] but I don't think that would gain you any power
 
I think if you decreased the displacement you could get it to rev faster =] but I don't think that would gain you any power

It wouldn't work. Diesels tend to have longer strokes than they have cylinder bore diameter to take advantage of the slower burning fuel.

An undersquare diesel would lose out on overall performance ie. both in terms of power and torque.

They're designed the way they are for a reason.
 
Maybe this is why they are left better to be used with far heavier chassis for vehicles such as lorries etc...

and if considering a remap, would it cause the engine to rev faster...?
or any other mod that can be made for it to do so..?
 
Losing weight on parts of the engine. Flywheel, crank, pistons, rods even the valvetrain.


None of this will make the flamefront propagate any faster towards the receeding piston crown. One thing that will promote faster burning is higher cetane fuel. Theoretically you could then increase the maximum possible and maximum permissible revs.

If you do this then rotating balance becomes ever more important, more so than rotating mass.
 
Last edited:
audi managed to make there diesel rev and make power up to 5500 rpms

if you have an 8v hdi then you can get a piper cam for it, and also a bigger turbo might help things and running an lpg mix and some bp ultimate fuel

I have seen people make useful power to 6k with them might be worth a look if you are that way inclined

http://www.allardmotorcompany.com/filestore/list/documents/Allard-A3-TDI-quattro.pdf

it can be done,

the bloke goes by the name of "devonmikeyboy" on various vag and diesel forums
 
Last edited:
audi managed to make there diesel rev and make power up to 5500 rpms

if you have an 8v hdi then you can get a piper cam for it, and also a bigger turbo might help things and running an lpg mix and some bp ultimate fuel

I have seen people make useful power to 6k with them might be worth a look if you are that way inclined

http://www.allardmotorcompany.com/filestore/list/documents/Allard-A3-TDI-quattro.pdf

it can be done,

the bloke goes by the name of "devonmikeyboy" on various vag and diesel forums

I've got a 0 valve now!

The 2.2 HDi 16 valve I previously had was redlined at 5300rpm at would go to it quite happily, if pointlessly.
 
Yeah I know he's running a new engine and had it all cryogenically treated as well i didn't know it was a 20v (i'm assuming thats what you ment) but still that is a wickedly fast car with nearly 500lbft before the new engine
 

Please watch this on my YouTube channel & Subscribe.


Back
Top