tuned derv ZS update - Page 35

p_b82 · 15-02-18, 08:54 AM

A set I had made up a while back.

6 smaller holes & a higher break pressure - you were going to test them for me, but took the car off the road before you had a chance.

Wouldn't re-sizing the holes on the SDI spec nozzles just bring us right back into the 200 issues with poor droplet size and atomisation though?

We've been there - 200's just aren't suitable for a VNT setup due to the soot they emit due to the poor combustion we get with them.

dakta · 15-02-18, 01:29 PM

Quote:

Wouldn't re-sizing the holes on the SDI spec nozzles just bring us right back into the 200 issues with poor droplet size and atomisation though?

Depends, these days i recommend the smallest nozzle you can get away with for obvious reasons. However ultimately (and this is taken more from tuning other manufacturer diesels) you do/should get significant gains from merely enlargening the holes.

Its why people have mulled over the fact that poor combusiton is caused by other factors, but the data to provide a proof isn't easy to come by.

best option is the most expensive and thats literally to get a custom set made. However even then you can't get away from the experimental nature of it nonetheless I wish thee luck

meetings now concluded succesfully so all good.

ZS Phil · 15-02-18, 06:40 PM

Quote:

Originally Posted by p_b82

A set I had made up a while back.

6 smaller holes & a higher break pressure - you were going to test them for me, but took the car off the road before you had a chance.

Wouldn't re-sizing the holes on the SDI spec nozzles just bring us right back into the 200 issues with poor droplet size and atomisation though?

We've been there - 200's just aren't suitable for a VNT setup due to the soot they emit due to the poor combustion we get with them.

Ah ok, I remember now. Was 2 years ago that now, where does the time go?!
Just got my clutch delivered back from CG today so can pop the engine back in now.
I'm not convinced the orifice size is the problem with the 200 tdis, I have mapped them to give almost a smoke free burn (and very little power). I think the problem is more the position of the holes rather than the size of them.
What I want is the standard spray pattern with a larger orifice. Injection stage pressures can be played with to help with atomization (if needed), I found an interesting paper on this once. But of course that will put more load on the pump.

ZS Phil · 15-02-18, 06:43 PM

Quote:

Originally Posted by dakta

best option is the most expensive and thats literally to get a custom made

Agreed but try finding a place to do just 1 set!

dakta · 15-02-18, 07:27 PM

I never said it would be easy!

We sort of come back on the old problem of what being possible not being viable. You could (once upon a time, anyway its got a bit saturated now) make a nice economic case for developing an injector upgrade say for a VAG PD or VP engine. The test set you'd take a drastic loss on but you could break even in your first batch of sales and profit on the next

That said it can be done im sure, question is what people will consider value enough to proceed with

p_b82 · 16-02-18, 03:33 PM

Quote:

Originally Posted by ZS Phil

Ah ok, I remember now. Was 2 years ago that now, where does the time go?!
Just got my clutch delivered back from CG today so can pop the engine back in now.
I'm not convinced the orifice size is the problem with the 200 tdis, I have mapped them to give almost a smoke free burn (and very little power). I think the problem is more the position of the holes rather than the size of them.
What I want is the standard spray pattern with a larger orifice. Injection stage pressures can be played with to help with atomization (if needed), I found an interesting paper on this once. But of course that will put more load on the pump.

The problem we have is that as soon as you change the flow rate, you will change the flow pattern away from "standard"

I think I un-earthed the same paper, or you linked me it, as I spent a good while trying to understand the very complex nature of atomisation VS burning characteristics - especially under a compression ignition system.

What could not be denied was that the finer the mist, the better the combustion.
The longer time ignition has - the cleaner the burn too; the combustion becomes more complete as it has longer to use the available oxygen.

It isn't just a single simple factor as droplet size, but I do think that for our engines, with the limitations of the head and the flow characteristics we have, 200's just aren't the way to go; if they were easily tamed then it would have been done by now IMO.

From what I've read, more smaller holes should burn cleaner, if we're still top end limited by the pump, then so be it; but what I didn't want is to build something that coked the vanes up and needed a turbo rebuild after only a few K miles. That seems to be the net result of any-one with a VNT that tried to use 200's.

Hopefully I'll know in the not too distant future, and can feedback any findings... Not that many people here will go down the route I am!

ZS Phil · 17-02-18, 10:09 AM

Quote:

Originally Posted by dakta

I never said it would be easy!

We sort of come back on the old problem of what being possible not being viable. You could (once upon a time, anyway its got a bit saturated now) make a nice economic case for developing an injector upgrade say for a VAG PD or VP engine. The test set you'd take a drastic loss on but you could break even in your first batch of sales and profit on the next

That said it can be done im sure, question is what people will consider value enough to proceed with

This is the problem, not enough people willing to spend the money. To be fair though, can't really blame them. I think you have to be pretty keen to be doing what we are doing with clanger old rover diesel engines.
Getting a set modified, for a one off at least, will work out cheaper I imagine. Trouble is the possible place is in Poland

. Well see what happens though.

ZS Phil · 17-02-18, 10:28 AM

Quote:

Originally Posted by p_b82

The problem we have is that as soon as you change the flow rate, you will change the flow pattern away from "standard"

I think I un-earthed the same paper, or you linked me it, as I spent a good while trying to understand the very complex nature of atomisation VS burning characteristics - especially under a compression ignition system.

What could not be denied was that the finer the mist, the better the combustion.
The longer time ignition has - the cleaner the burn too; the combustion becomes more complete as it has longer to use the available oxygen.

It isn't just a single simple factor as droplet size, but I do think that for our engines, with the limitations of the head and the flow characteristics we have, 200's just aren't the way to go; if they were easily tamed then it would have been done by now IMO.

From what I've read, more smaller holes should burn cleaner, if we're still top end limited by the pump, then so be it; but what I didn't want is to build something that coked the vanes up and needed a turbo rebuild after only a few K miles. That seems to be the net result of any-one with a VNT that tried to use 200's.

Hopefully I'll know in the not too distant future, and can feedback any findings... Not that many people here will go down the route I am!

That's pretty much my understanding of the matter too but as with everything it is a compromise, all very well having optimal atomization but if you can only get 40mg/stroke of fuel in the it defeats the point, May be better to have slightly less than optimal atomization (but still got enough for minimal smoke) but ultimately allow more useable fuel in per stroke than SDIs allow for.
Just doing some quick maths looking at combined orifice area looks like this:
Sdi (5 x 0.22) total area is 0.190
At a guess your proposed nozzles (assuming the part number ends 882) (6 x 0.205) total area is 0.198
Sdi modified (5 x 0.23) total area is 0.210
200 tdi (5 x 0.24) total area is 0.225

My concern would be at what angle do those 6 hole injectors enter the head in the engine for which they were designed? Is there an offset bowl in the piston? What is the clamp angle in the original engine? It is these factors which I believe makes the burn so rubbish with the 200 tdis.
There is so little info about those 6 hole nozzles and even less about the engine for which they are designed so finding the answers to the above questions is very difficult by simply looking online. Either pull a scrap engine to bits and get the measuring tape out or as Kris said, get them fitted and suck it and see. The letter being the much easier option I imagine.

ZS Phil · 17-02-18, 10:39 AM

Quote:

Originally Posted by p_b82

The problem we have is that as soon as you change the flow rate, you will change the flow pattern away from "standard"

I think I un-earthed the same paper, or you linked me it, as I spent a good while trying to understand the very complex nature of atomisation VS burning characteristics - especially under a compression ignition system.

What could not be denied was that the finer the mist, the better the combustion.
The longer time ignition has - the cleaner the burn too; the combustion becomes more complete as it has longer to use the available oxygen.

It isn't just a single simple factor as droplet size, but I do think that for our engines, with the limitations of the head and the flow characteristics we have, 200's just aren't the way to go; if they were easily tamed then it would have been done by now IMO.

From what I've read, more smaller holes should burn cleaner, if we're still top end limited by the pump, then so be it; but what I didn't want is to build something that coked the vanes up and needed a turbo rebuild after only a few K miles. That seems to be the net result of any-one with a VNT that tried to use 200's.

Hopefully I'll know in the not too distant future, and can feedback any findings... Not that many people here will go down the route I am!

That's pretty much my understanding of the matter too but as with everything it is a compromise, all very well having optimal atomization but if you can only get 40mg/stroke of fuel in the it defeats the point, May be better to have slightly less than optimal atomization (but still got enough for minimal smoke) but ultimately allow more useable fuel in per stroke than SDIs allow for.
Just doing some quick maths looking at combined orifice area looks like this:
Sdi (5 x 0.22) total area is 0.190
At a guess your proposed nozzles (assuming the part number ends 882) (6 x 0.205) total area is 0.198
Sdi modified (5 x 0.23) total area is 0.210
200 tdi (5 x 0.24) total area is 0.225

My concern would be at what angle do those 6 hole injectors enter the head in the engine for which they were designed? Is there an offset bowl in the piston? What is the clamp angle in the original engine? It is these factors which I believe makes the burn so rubbish with the 200 tdis.
There is so little info about those 6 hole nozzles and even less about the engine for which they are designed so finding the answers to the above questions is very difficult by simply looking online. Either pull a scrap engine to bits and get the measuring tape out or as Kris said, get them fitted and suck it and see. The letter being the much easier option I imagine.

p_b82 · 17-02-18, 01:24 PM

Agreed it is all a compromise indeed - there is a balance (was reading some stuff on the early cummins yesterday and 5 hole VS 6 hole (with 4 and 7 being debated rages).

They are using injectors in inches not cms, but their "small" 6*0.33mm (0.013") flow slightly more than the 5*0.35 (0.014")

It is a stupidly complex situation, there is no "definitive" article out there, and so it is experimentation. Simple % area increase doesn't easily translate to X bhp or Y smoke.

What seems to be pertinent is making sure you get the right angled injection pattern rather than the number of holes - EG don't stick a set of 155's in a 145 piston crown config. As is getting a flat plane injector VS an angled one...

Finding out the injector angle to the head is not easy though - nor is always finding the relevant nozzle part number for a given injector at times... That's where the risk factor comes in.

I'm willing to experiment, I can burn through a few sets and types of nozzles if I need to, to find what I am looking for. If I do it alone then I'll not be sharing precise details... I was bitten hard by testing the headlift theory and helping to prove it conclusively for the masses, and I frankly am not willing to spend the £ on research for others to just benefit from the rewards anymore. Selfish I know, but I've not seen any-one else share that sort of cost burden in the years since...

If some-one shares costs then they'll gain from the knowledge we accumulate - all I know is that there are loads of potential options open to us - one has to think beyond the given part numbers that are floated about as gospel....

If my rig had been built when it was supposed to be, I'd have worked through a few options by now - unless I got lucky with my first choice... I'm not expecting it, but time will tell.