Just wondered, I was talking to a couple of mates today and I said that my 1.7cdti vx is a slug compared to the 1.9 TDI pg lump and only 200cc difference. I know one's a 16v the other 8 but diffirence in low grunt/torque is unreal. One of said the older 1.7/9 dtl vx engine was quite torquey as it too was an 8v but still probably not in the same league as the 1.9 tdi pg

We couldn't googled it as phone data connection was also crap

So what design is the 8v tdi pd design that makes it so grunty

16V vs 8V isn't the issue. VW did a 2.0 16V TDI in PD format and that pulled too.

 

IMO that low revs torque is all down to the PD injector system running on an engine optimised for it.

 

I'd also guess that your 1.7CDTi is strangled by Euro-bolox compliant mapping and devices.... If it doesn't have a DPF, get it remapped man!

It shouldn't be, it's the 100hp the 1.9 is 105 plus bigger/heavier.....1.7 doesn't have dpf

I've never found it lacking on a Combo before, DTUK box frees it up slightly as you can't remap it

The vauxhall unit was a slug from the day if its introduction. 

 

The PD = Pumpe Duse or unit injectors as Lucas called them in English.  The VW engine was designed before the common rail was considered reliable enough or capable of sufficiently high pressures.

The old mechanical injection systems, either the very old inline type or "newer" distributor type, were working fine at injection pressures of around 180 bar.

At these sorts of pressures, the fuel was not injected into sufficiently fine droplets to control "knock".  This was the lag between the commencement of injection and the initiation of combustion.  Quite a bit of fuel in the combustion chamber built up, this would then go off rapidly causing the knock.  Pre combustion chambers were commonly used to help control this unwanted, wayward tendency.  Pre combustion chambers are not very efficient compared to direct injection.

 

Unit injection, with the pressure developed right behind the injector by the camshaft, could produce injection pressures of up to 2000bar,  A whole order of magnitude higher.  This meant finer fuel droplets and shorter ignition delay times.   Injection nozzles could now become more sophisticated too.   Leading to less knock and less pollution, more power and torque.

 

Combining the very high injection pressures to direct injection, another technology transfer of the time, was an easier process.  Add in turbos, which also not been universal before, and the path was clear to much cleaner, even more fuel efficient and powerful Diesels.

 

The combination of direct injection, much better injection control and turbos produced the big leap in Diesel output.  PD allowed that to happen, and paved the way to "civilised" Diesels, with power, economy and refinement.  (compared to the old stuff at least).

 

The icing on the cake was the electronic control of the injection process.  Previously restricted to a relatively crudely timed single squirt, electronics allowed interrupted injection.  A small squib to get things warmed up, then stoke up the fired progressively - or however it is found best works.

Initially common rail could only produce injection pressures of just over 1000bar, but the system was easier to control and possibly cheaper too.  Advances boosted attainable pressures to similar values of the now old PD.

 

Sorry, its a bit long for the interweb despite missing lots.  Couldn't think how to put it in a one line quip.

No they were crap, my old man had a couple.

 

I suppose that's why Vx gave up and bought in Fiat diesel engines.

Edited 15 January, 201511 yr by Aspman

Sell it or remap/tune it to the death then. satisfaction either way.... monetary or a feeling of well being that something "crap" has been expunged.

The vauxhall unit was a slug from the day if its introduction. 

 

The PD = Pumpe Duse or unit injectors as Lucas called them in English.  The VW engine was designed before the common rail was considered reliable enough or capable of sufficiently high pressures.

The old mechanical injection systems, either the very old inline type or "newer" distributor type, were working fine at injection pressures of around 180 bar.

At these sorts of pressures, the fuel was not injected into sufficiently fine droplets to control "knock".  This was the lag between the commencement of injection and the initiation of combustion.  Quite a bit of fuel in the combustion chamber built up, this would then go off rapidly causing the knock.  Pre combustion chambers were commonly used to help control this unwanted, wayward tendency.  Pre combustion chambers are not very efficient compared to direct injection.

 

Unit injection, with the pressure developed right behind the injector by the camshaft, could produce injection pressures of up to 2000bar,  A whole order of magnitude higher.  This meant finer fuel droplets and shorter ignition delay times.   Injection nozzles could now become more sophisticated too.   Leading to less knock and less pollution, more power and torque.

 

Combining the very high injection pressures to direct injection, another technology transfer of the time, was an easier process.  Add in turbos, which also not been universal before, and the path was clear to much cleaner, even more fuel efficient and powerful Diesels.

 

The combination of direct injection, much better injection control and turbos produced the big leap in Diesel output.  PD allowed that to happen, and paved the way to "civilised" Diesels, with power, economy and refinement.  (compared to the old stuff at least).

 

The icing on the cake was the electronic control of the injection process.  Previously restricted to a relatively crudely timed single squirt, electronics allowed interrupted injection.  A small squib to get things warmed up, then stoke up the fired progressively - or however it is found best works.

Initially common rail could only produce injection pressures of just over 1000bar, but the system was easier to control and possibly cheaper too.  Advances boosted attainable pressures to similar values of the now old PD.

 

Sorry, its a bit long for the interweb despite missing lots.  Couldn't think how to put it in a one line quip.

That's some explanation and says a lot, thanks for that  

No they were crap, my old man had a couple.

 

I suppose that's why Vx gave up and bought in Fiat diesel engines.

It must be the 1.9s that fiat

Sell it or remap/tune it to the death then. satisfaction either way.... monetary or a feeling of well being that something "crap" has been expunged.

Yes that the choices, it's £350 for a map, I need to decide what one I'm going to keep and put the money in that, as I'm not spending that getting something mapped then getting rid

I've never driven a GM diesel that pulled like a PSA or VAG unit feels to do. Of course, GM have a habit of over-gearing everything.

Probably because there isn't one

That's some explanation and says a lot, thanks for that  

It must be the 1.9s that fiat

 

Yup the 1.9s were fiat designed. Not sure if Vx modified them or if the newer 2.0d are also fiat derived.

 

The 150 had a bit of a reputation for going wrong, don't think the 120 was a as bad.

When I worked in Germany, one job was to replace the V6 GMC Diesel with a proper Oil Burner - a Cummins.  Time allocated - 25hrs.  Time taken - lots more.  Pig of a job.

This was into the US forces fleet of school/military buses. 

The std (rear) engine was normally so noisy, the driver, who was likely stoned, couldn't hear when the big ends went (often) so just pressed on until the thing threw a rod.  Big bang.  Lots of smoke.  Screaming shell shocked Vietnam veterans or kids.

 

GM also tried to Dieselise one of their V8's.  Flopped big time due to severe unreliability.

So no fan of GM Diesels here.

Yup the 1.9s were fiat designed. Not sure if Vx modified them or if the newer 2.0d are also fiat derived.

 

The 150 had a bit of a reputation for going wrong, don't think the 120 was a as bad.

I don't know either

Mine's the 100 but a blocked egr won't help at all, I'd clean it as best I could but the weather's hellish

When I worked in Germany, one job was to replace the V6 GMC Diesel with a proper Oil Burner - a Cummins.  Time allocated - 25hrs.  Time taken - lots more.  Pig of a job.

This was into the US forces fleet of school/military buses. 

The std (rear) engine was normally so noisy, the driver, who was likely stoned, couldn't hear when the big ends went (often) so just pressed on until the thing threw a rod.  Big bang.  Lots of smoke.  Screaming shell shocked Vietnam veterans or kids.

 

GM also tried to Dieselise one of their V8's.  Flopped big time due to severe unreliability.

So no fan of GM Diesels here.

I think gm/Saab/vx diesels are ok, they're maybe not in the same league as vw though

There just wasn't any market for domestic diesel vehicles in the USA so I guess they just didn't bother to develop any. Red diesel is obviously communist as well.

There just wasn't any market for domestic diesel vehicles in the USA so I guess they just didn't bother to develop any. Red diesel is obviously communist as well.

 

But there was a market after the fuel crisis in '73, but the Gm Diesel was so horrific the backwash of disgust and alienation is still there.  So of course there is still no money to develop a decent one.

Cummins make/made a "small" 4 cylinder, weighs in at over 1000lbs, to produce not much more than 100bhp.

You mention fuel it is significantly more expensive than petrol.

I'm driving a vivaro for a couple of days. Goes well when it gets going, but so much turbo lag compared to a proper diesel.

I'm driving a vivaro for a couple of days. Goes well when it gets going, but so much turbo lag compared to a proper diesel.

Yup. Dont reckon much to the vivaro engines. The 1.9 is slowww. The 2.0 115 is okay, but nothing special IMO.

Transits 2.2's are okay but laggy in 140bhp form.

Pd's brill though. Plenty of torque.

Never have been able to drive the old 2.5 straight 5 174bhp transporter. But i know someone with the newer 2.0 twin turbo 180bhp transporter, so im hoping for a go in that at some point

125ps in the rear wheel drive transit is my favourite. Not crazy fast, but a nice linear power delivery.

125ps in the rear wheel drive transit is my favourite. Not crazy fast, but a nice linear power delivery.

Probably a smaller turbo than the 140, so prob less laggy isnt it (:

I've had several 1.9 TDI 130bhp cars, and both 2.0 TDI 140bhp PD and CR's, including a 1.9 and 2.0PD at the same time so a direct comparison jumping from one to the other.

 

The older 1.9 had more torque lower down in the rev range than the 2.0 in both PD and CR formats. The torque figures show them as almost being the same but in reality the 1.9 was much better, I still miss it now. This has been mentioned many times online especially amongst those who tow.

 

If you want something that pulls like a 1.9 TDI PD, get a 1.9 TDI PD.  

I'm driving a vivaro for a couple of days. Goes well when it gets going, but so much turbo lag compared to a proper diesel.

It's obviously the lag, and bloody bad at that!, coupled with a blocked egr that's making hellish to drive, especially low down

The older 1.9 had more torque lower down in the rev range than the 2.0 in both PD and CR formats. The torque figures show them as almost being the same but in reality the 1.9 was much better, I still miss it now. This has been mentioned many times online especially amongst those who tow.

If you want something that pulls like a 1.9 TDI PD, get a 1.9 TDI PD.

As you say....it's the way they designed the 1.9 tdi pd, mine's the 105 (bit think it might be mapped, I'd need to get a go in one I knew was 105 to find out

It puts the 1.7cdti to shame

Must admit....if I could get the 1.7 to pull low down like the 1.9 tdi pd, I'd probably use it and sell octy

Edited 16 January, 201511 yr by Cleo

It's obviously the lag, and bloody bad at that!, coupled with a blocked egr that's making hellish to drive, especially low down

As you say....it's the way they designed the 1.9 tdi pd, mine's the 105 (bit think it might be mapped, I'd need to get a go in one I knew was 105 to find out

It puts the 1.7cdti to shame

Must admit....if I could get the 1.7 to pull low down like the 1.9 tdi pd, I'd probably use it and sell octy

Really odd, is yours in good health or maybe it's just a difference in the Combo lump.

Apart from a blocked egr and probably most of the pipes to and from it, it's fine, but seriously, below 2500 it's totally gutless

Really odd, is yours in good health or maybe it's just a difference in the Combo lump.

 

I had a 1.7Di (Small turbo, no intercooler) Corsavan, and it lacked lowdown torque, although when you got it on boost and kept it there, it fair flew. 

 

The only diesel in a car I can think of with the low down drag the PD's have is the TDDI in the older Fords. The price of progress is they seem to want to make diesels more "petrol like", which I can understand from a noise point of view, but I like low down torque, I don't like having to rev stuff. I generally prefer 8 valve engines to 16 valve, even in petrol vehicles. I used to love that I could do a hill start in the old Transit by putting it in 2nd and letting the clutch halfway up without pressing the accelerator.