VNT on a mechanical turbo diesel....

[HDi fun]

We had a Seat Ibiza 1.9d, this was a NA one with the 1896cc 4 cylinder engine, indirect injection and worth about 69-70bhp at best.

It was fine and would pull from idle speed very convincingly. It all went downhill thereon.

Diminishing torque delivery by 2000rpm. Dead in the water by 3000rpm.

[jarrus]

You think it's just turbo lag but then realise that just slow...lol

[Harvey]

Diesel engines do lend themselves to forced induction, the main reason being that there is no throttle.

Just be aware that many modern diesels actually run a throttle flap.

[jarrus]

That's a difficult one, really

They are swirl flap really rather than a device for controlling how much air enters the engine

[Harvey]

The Vauxhall/Opel/SAAB/Alpha/Fiat 1.9 engine actually has 8 runners in the inlet manifold and four of these, one for each cylinder, have a swirl flap. The inlet manifold itself has a single butterfly throttle body. The purpose of this is probably to allow the engine to develop vacum at stages to operate gas recycling and comply with emmission regulations.

I posted photos up somewhere, showing the innards of the inlet manifold which conveniently is in two halves.

[jarrus]

Fair enough,

I would say then that if you're running a bigger turbo and flowing more air you may require some kind of recirculating valve or dump valve in your intake pipe work to preserve your turbo.

[Harvey]

This is not a problem I anticipate and there is no turbo stall at present. If it were to raise its head and become an issue with the bigger cover and wheel, it is easy to deal with.

[jarrus]

What solution do you have in mind?

[HDi fun]

Some multivalve diesels do use such butterfly valves to enhance low end torque. But diesel engine torque delivery is ultimately governed by fuel delivery only. The accelerator pedal does not directly control airflow into the engine.

[jarrus]

Indeed, that's why i'm going for the bosch pump now

[Harvey]

The solution is simply to put on a BOV in proximity to the throttle body just before the inlet manifold. The 4 flaps referred to above are closed at low RPM to give torque as above and open gradually to wide open depending on throttle position and engine load. Having super glued these flaps open on the old manifold before it was replaced I could not feel any difference in operation between them operating and them being wide open.
As an experiment I intend to remove the butterfly from the throttle body to see what the effect might be.

[jarrus]

Maybe worth while it could help with your EGR dilemma.

[Harvey]

Update:
As I have a spare inlet manifold for the Vauxhall 150 engine I have now removed the throttle flaps and need to plug the holes before porting the manifold where I plug it and make light porting alterations on the manifold generally which appears very well designed.
Yesterday I completed the following :
1. An improved feed from the modified air scoop in front of the front mount intercooler to the air box.
2. An improved feed from the MAF sensor body at 70mm dropping to 60mm and down to the compressor cover entry at 57mm.
3. An improved feed from the compressor outlet to the hot side of the intercooler.
I will make a further improvement to this in advance of fitting the turbo with the 56 cover and 60 wheel.
4. I removed the oil breather from the top of the engine that runs to the inlet tract. This now vents to a plastic container with some vents in the top acting as a catch can. I am interested to see what if anything gathers in this container.
5. I removed the butterfly flap from the throttle body but left the spindle in place until I determine what the effects might be. The spindle can be removed at a later stage.

I have probably only done 10 miles with no negative feedback and it will take a trip to the rolling road to determine what gains have been achieved. I would guess the air is flowing better so with a bit more fuel there will be more power.
I am also now looking at water methanol injection both to improve fuel economy and top end power. I already use water methanol injection on one of my Subaru engines, however, diesel operation has a different philisophy.

[jarrus]

Sounds good,

I've been looking into water/methanol injection as well, I've been looking at kits from DevilsOwn as I've heard good things about them.
From what I can work out on diesels the set up is pretty similar,

What is the philosophy have you found? I'd be interested in reading your finds

[Harvey]

My experience on a petrol is that the water methanol kit greatly reduces EGTs so it adds safety. It did not add a lot of bhp, perhaps 12 bhp around 400 bhp (the 2 litre turbo charged engineis now 422 bhp), however, the big advantage was that with the reduced EGTs and use of water methanol I was able to make good additions of ignition advance which resulted in noticably more torque and that is obviously the most outstanding gain with my petrol experience.
On the diesel I expect there will be EGT reductions but until I fit an EGT guage I don't know what these are at present and I expect that the water methanol will lead to cleaner burning of the fuel already there but it should be possible to increase fuelling over the present settings and it may help clean the engine up if it were smokey which this engine is not at present.
Depending how the kit is set up I think there will also be gains in fuel economy when the car is being driven normally.
The previous kit came from Snow and I am in touch with their Technical Department to get as much information as possible.
This is what I expect will happen and it will be another interesting voyage of discovery.

[jarrus]

Indeed,

EGT's will be a lot lower if you are running richer so the benefits are clear as more smoke will raise EGTs somewhat.

[jarrus]

I would go for Snow Performance myself but I do find there products rather expensive, yes they are very high tech but I really don't need that level of control