Denso IDI injector nozzle tech? (1 Viewer)

[GTSSportCoupe]

Wondering if anyone has a link to technical information on Denso IDI injector nozzles? I'd like to learn more about flow differences, spray pattern differences, etc. And the consequence of these differences on diesel knock, efficiency, power, EGT, etc.

I recently replaced my 2LTE injectors with a brand new set of Toyota injectors. The injectors I went with are from the later 2LTE 1995-2001. The nozzles are different in these, and actually match nozzles used in all of the 2LT-II's also (1990+). The early 2LTE nozzle is DN10PD76. The late 2LTE (and all 2LT-II) nozzle is DN0PD58.

I was fine trying these different injectors, as the pre-cup, cylinder head, fuel return rail etc. are the same between the two models. The injector pumps are same pressure also, with the only difference being change of some sensors in the later pumps.

One thing I noticed though is the pintle is different between the two nozzles. The 2LTE nozzle has a longer pintle with a cone shape on the end and the 2LT-II nozzle has a shorter pintle. I can only guess this impacts the diesel spray pattern.

Since the new injectors I've notice my engine has more of a normal diesel sound. Most other 2LTE's I've heard have almost a gas engine sound. The sound my 2LTE has now is more what I've heard from other 2LT-II's; and other mechanical injection IDI diesels in general. I've always wondered about the sound difference, and now I wonder if it could be partly injector nozzle design. I have put brand new early 2LTE nozzles into my original injectors before and re-shimmed them to the proper crack pressure, and they still sounded quieter. So I don't think this has to do with simply going to a brand new injector.

Apparently depending on nozzle spray pattern, the fuel ratio that burns in the pre-cup vs. cylinder can vary. A less atomized spray is more likely to burn in the cylinder. More atomized will burn more in the pre-cup.

One of the very interesting consequences of this is: The more fuel burning in the pre-cup, the more energy lost to the coolant. ie. More impact on coolant temps and more likely-hood of overheating problems. The 2LT-II seems to have fewer overheating issues than the 2LTE. I'm wondering if this is partially a result of injector differences. Maybe Toyota sacrificed functionality for a quieter diesel knock? As the Prado was a 'luxury' vehicle? I'll report on any difference in coolant temps when I tow my trailer this summer (if I get out camping with this COVID crisis).

Here is a pic of one of my new injectors with the 2LT-II style nozzle:

 

[gerg]

Interesting. Something to consider too is the length manufacturers go to reduce emessions. Unfortunately all to often emessions improvements comprimise power.

 

[GTSSportCoupe]

Interesting. Something to consider too is the length manufacturers go to reduce emessions. Unfortunately all to often emessions improvements comprimise power.

That is a very good point; I agree that could be reason for the difference also. Hopefully the topic of emissions differences would come up in a technical document also.

A few of the differences I've noticed with these injectors, is quicker turbo spool, more of a typical diesel sound, instant perfect clean start all the time, but less peak torque.

Granted, I suppose my old injectors could have been flowing more due to nozzle wear and a lower crack pressure from wear (longer injection duration)? Less ideal spray pattern. Not sure.

 

[GTSSportCoupe]

Well, not sure how true this is, but here is a start. From the interwebs. Using a VW DN0SD273 nozzle as an example. If this is right, it would indicate the 2LT-II injector has a narrower spray cone than the 2LTE. This could mean more burning in the cylinder than the precup if I understand right. Meaning lower coolant temps and more diesel knock for the 2LT-II.

D = Nozzle
[D]N = Pintle Nozzle

[DN]0 = Spray cone Angle

[DN0]S = 6 mm nozzle diameter

[DN0S]D = Delay type nozzle (with obturator) the needle restrictor

[DN0SD]273 = Unique Identifier (special features)
These include pintle profile (converging/diverging), flow lift curve details, anti-coking flats etc. This number simply increments as a new design requirement is requested.

Remember those last digits changed often as perceived design improvements were made in an effort to get quieter and more efficient burning, rendering older numbers ‘obsolete’

 

[GTSSportCoupe]

And another interpretation:

Ex. DN0SD273

D= Nozzle

N= Pintle nozzle; L= hole type; S= hole type seat nozzle (additional: L= long nozzle collar; without initial= short collar) (A/B/Z/without initial= details about fixing of the inlet)

0= spray cone angle

S= 17mm collar diameter; P = 14mm, R = 16mm, S = 17mm, T = 22mm, U = 30mm, V = 42mm, W = 50mm

D= standard nozzle/ P= experimental type

273= serial number

 

[GTSSportCoupe]

More interwebs finds. List of denso nozzles for Toyota diesels. Very interesting to see various types for various applications. Attached.

 

[John in Utah]

I had to look up some videos of the 2LTE but I can definitely see what you mean about less diesel knock. My 3L and 3B sound nearly identical, and much more like a tractor than a 2LTE.

Interesting to note the NA 2L,3L, and 5L share a different nozzle entirely. I believe it’s DN4PD57

 

[GTSSportCoupe]

I had to look up some videos of the 2LTE but I can definitely see what you mean about less diesel knock. My 3L and 3B sound nearly identical, and much more like a tractor than a 2LTE.

Interesting to note the NA 2L,3L, and 5L share a different nozzle entirely. I believe it’s DN4PD57

I'm really loving that my 2LTE sounds like a proper diesel now. I always loved the way 3B's sounded, and my motor is very similar now. I never thought minor injector differences would change the way a given engine could sound!

 

[GTSSportCoupe]

OK, I think I'm getting this figured out. I've basically been right in my guess work above. I read some of this and started to learn more about diesel injectors: Fundamentals of Medium/Heavy Duty Diesel Engines

What I learned, is that the regular 2LT-II injector is a standard 'pintle nozzle' and the early 2LTE injector is a 'semi-throttling' nozzle. The point of throttled nozzles is to introduce fuel in a staged sequence to reduce the sudden rise in pressure and heat during initial combustion.

A quote from the book above: 'It limits the amount of fuel in the combustion chamber at the beginning of injection, which in turn reduces the quantity of fuel accumulations during ignition delay period. Doing this minimizes the characteristic diesel knock and pressure spikes in a cylinder that produce NOx. Less fuel means less heat and combustion noise when it ignites. This injection strategy is somewhat similar to pilot injection, but with a throttling pintle nozzle, injection takes place uninterrupted. The throttling effect on fuel delivery is most effective at idling when the valve lift is low.'

So yes, in a nutshell, less diesel knock and less NOx for the early 2LTE version. These effects are most noticeable at idle. I do find it interesting that Toyota scrapped the idea in the later generations of the 2LTE. Makes me glad I've scrapped the early nozzle too....

Here are some pictures showing what I've been going on about:

DN0PD58 Pintle Nozzle (2LT-II and late 2LTE)

DN10PD76 Semi-throttling Nozzle (early 2LTE):

 

[John in Utah]

Fascinating. Any way to determine this type of nozzle from the part numbers?

Seems to me the reduction in pressure spike and NOx should correspond to lower combustion temps? How does this jive with your theory regarding coolant temps? The early nozzle design dates do seem to correlate with the cracked head issues of the 2lte - but lots of variables at play there.

 

[GTSSportCoupe]

Fascinating. Any way to determine this type of nozzle from the part numbers?

Seems to me the reduction in pressure spike and NOx should correspond to lower combustion temps? How does this jive with your theory regarding coolant temps? The early nozzle design dates do seem to correlate with the cracked head issues of the 2lte - but lots of variables at play there.

I'm not sure how to tell from the Denso part numbers.

In reading more, it sounds like the progressive nature of the throttled pintle type matters most at idle. The heat problems of the 2LTE don't happen at idle. So maybe the two injector types are basically the same once the engine is under load - and that is the point where heat would become a problem. So it's likely there is really no difference in this regard.

If you're fascinated by this tech stuff, you'll find it interesting to know that Toyota also made ceramic precups for a version of these engines called the 2LTHE (see attached). Apparently that ceramic ran significantly hotter as it did not conduct the heat (as energy loss) into the coolant nearly as well as a regular metal precup does. From the little I've been able to find on the 2LTHE, they did not have the head problems of the 2LTE. I've always wanted to buy one of these 2LTHE heads and try it....but they're just too darn expensive. 1110154141 Toyota HEAD SUB-ASSY, CYLINDER, Price: 1257.59$, Weight: 33.23kg - PartSouq - Auto Parts Around the World PartSouq Auto Parts Around the World

 

[Nas90tdi]

Clearly too much time at home Nick!
My newly rebuilt injectors made my engine sound much different at well when I did my head. I had all the nozzles replaced. Much more diesel sound now than before.

 

[John in Utah]

I'm down the rabbit hole now.

In reading more, it sounds like the progressive nature of the throttled pintle type matters most at idle. The heat problems of the 2LTE don't happen at idle. So maybe the two injector types are basically the same once the engine is under load - and that is the point where heat would become a problem. So it's likely there is really no difference in this regard.

Found some interesting info on nozzle coking, and an SAE paper (that I didn't pay for) seems to suggest an old variable geometry (throttle) pintle nozzle with more deposits will lead to fuel being blocked during initial combustion, basically negating the throttling. But sounds like general experience is the opposite? That newer nozzles have louder knock and older ones - which should have more deposits/blockage/coking - are quieter.

I'm still not sure what would make Toyota go away from the throttled nozzle, it seems like the better design all things considered. Be interesting to know what on that list of nozzle numbers is throttled vs straight. Thinking of the 1HZ, 1KZTE or other more "modern" IDI engines.

A Procedure for the Assessment of Pintle Injector Nozzle Blockage (Nozzle Coking) In Indirect Injection Diesel Engines

The use of small indirect injection (IDI) diesel engines in passenger cars has gained popularity, as fuel economy becomes a salient feature of vehicle running costs. The broadening in the application of this engine from light commercial vehicles has placed a greater emphasis on customer acceptabilit

www.sae.org

https://pdfs.semanticscholar.org/f0e2/32961963defb3610ec28599284fea16a23d9.pdf

 

[KiwiDingo]

I'm still not sure what would make Toyota go away from the throttled nozzle, it seems like the better design all things considered.

Throttled nozzles aren't needed with modern injection systems as they can replicate it with pilot injection and variable injection set points compared to the basic mechanical injector pump of the past.

 

[GTSSportCoupe]

I'm down the rabbit hole now.

Found some interesting info on nozzle coking, and an SAE paper (that I didn't pay for) seems to suggest an old variable geometry (throttle) pintle nozzle with more deposits will lead to fuel being blocked during initial combustion, basically negating the throttling. But sounds like general experience is the opposite? That newer nozzles have louder knock and older ones - which should have more deposits/blockage/coking - are quieter.

I'm still not sure what would make Toyota go away from the throttled nozzle, it seems like the better design all things considered. Be interesting to know what on that list of nozzle numbers is throttled vs straight. Thinking of the 1HZ, 1KZTE or other more "modern" IDI engines.

A Procedure for the Assessment of Pintle Injector Nozzle Blockage (Nozzle Coking) In Indirect Injection Diesel Engines

The use of small indirect injection (IDI) diesel engines in passenger cars has gained popularity, as fuel economy becomes a salient feature of vehicle running costs. The broadening in the application of this engine from light commercial vehicles has placed a greater emphasis on customer acceptabilit

www.sae.org

https://pdfs.semanticscholar.org/f0e2/32961963defb3610ec28599284fea16a23d9.pdf

That's interesting about the nozzle coking....

Regarding which models may have gotten throttled nozzles: a laborious method could be to look at pictures online by typing each number in one at a time. The 'blue stars diesel' website seems to have good pictures of them.

I guess there are a few reasons why Toyota may have abandoned the throttled nozzle on the 2LTE. They seemed to stop using it around the time they revised the engine to be more robust against the overheating/headcrack issues. So there is a faint possibility the nozzle did cause higher temps in the pre-cups. Maybe not so much the throttled part, but the wider spray pattern could have caused high temps. Or, maybe it only had to do with emissions laws for various vehicles/markets at that time. Or maybe they just wanted to reduce costs by using the same injector across the board. They never used the throttled one with the 2LT-II from what I could tell - so maybe it did not work well with the mechanical injection pumps.

Throttled nozzles aren't needed with modern injection systems as they can replicate it with pilot injection and variable injection set points compared to the basic mechanical injector pump of the past.

He was just referring to the early and late 2LTE models. Both old.... Just trying to figure out the injector differences....

 

[teachmetosurf]

Very interesting.

I was about to purchase some *new* complete injectors from a place in Australia. The exchange rate puts them cheaper than having mine rebuilt, plus I'll still have my used injectors to rebuild/reuse in the future if needed.

As much as I'd like to purchase my own nozzles and do it myself, I don't think I am equipped/wise enough to replace & test new nozzles.

Do you think it'd be worth trying a set of injectors with the updated nozzle design?

 

[GTSSportCoupe]

Very interesting.

I was about to purchase some *new* complete injectors from a place in Australia. The exchange rate puts them cheaper than having mine rebuilt, plus I'll still have my used injectors to rebuild/reuse in the future if needed.

As much as I'd like to purchase my own nozzles and do it myself, I don't think I am equipped/wise enough to replace & test new nozzles.

Do you think it'd be worth trying a set of injectors with the updated nozzle design?

Don't try to rebuild them yourself. I had quite a few resources at my disposal when I did mine, and it was quite tough and they did not operate well very long. Best to leave it to the companies that specialize in this sort of thing.

I recommend just buying the injector that is the best price from a reliable source. I think you'll be just fine buying the part number that matches your motor. I have not run my new style injectors long enough to say with confidence they are a substantial advantage yet. Although I think that any of the 1990+ 2LT-II/2LTE part numbers will run fine.

Just FYI, these are the ones I bought: Toyota 2LTE 95-01 Diesel Fuel Injector Set 23600-59235 | eBay

But I see now the same seller has actually just listed the proper injectors for my vintage of 2LTE: Toyota 2LTE 90-93 Diesel Fuel Injector Set 23600-59155 | eBay

They're actually a really good deal compared to all the other brand new sources I looked at.

 

[teachmetosurf]

Just FYI, these are the ones I bought: Toyota 2LTE 95-01 Diesel Fuel Injector Set 23600-59235 | eBay

But I see now the same seller has actually just listed the proper injectors for my vintage of 2LTE: Toyota 2LTE 90-93 Diesel Fuel Injector Set 23600-59155 | eBay

They're actually a really good deal compared to all the other brand new sources I looked at.

Cheers - I'll have a look. Did yours come with injector washers/seals? The set I priced out from AUS had washers included. My trouble was, I could get my injectors rebuilt here in Alberta for around $460, but they couldn't source washers. I was then looking at around $100 (postage) just for a set of tiny washers from overseas.

For under $400 CAD I can have injectors + washers shipped to my door.

 

[GTSSportCoupe]

Cheers - I'll have a look. Did yours come with injector washers/seals? The set I priced out from AUS had washers included. My trouble was, I could get my injectors rebuilt here in Alberta for around $460, but they couldn't source washers. I was then looking at around $100 (postage) just for a set of tiny washers from overseas.

For under $400 CAD I can have injectors + washers shipped to my door.

Mine came only with the aluminum washer that goes between the injector and fuel return rail. So I still had to buy the washers that go in the head (the aluminum crush ones that go under the nozzle). I re-used the copper washers that go between the fuel rail and the nut that holds it on. I also re-used the larger non-crush washer in the cylinder head.

The aluminum crush washer that goes under the nozzle is the most important hands down. You cannot re-use those (been there done that...LOL). If you re-use them, exhaust gases get by and overheat/foul the injector nozzle. I bought mine locally from Rocky Mountain Imports. They were pretty cheap.

$400CAD to your door for everything seems like a pretty reasonable price.

 

[GTSSportCoupe]

Be interesting to know what on that list of nozzle numbers is throttled vs straight. Thinking of the 1HZ, 1KZTE or other more "modern" IDI engines.

OK, I just wasted 15min running through the list of nozzles pounding them into google and looking at images. I did not find any other 'throttled' nozzle like the one used in the early 2LTE/2LTHE.

One thing that I've discovered in my reading of SAE papers, is Toyota used the 2LTE/2LTHE as a bit of a test bed for more advanced technologies. They used it to develop the ECD (electronic controlled diesel) technology, they used it to try out ceramic pre-cups, and they also used it to develop ceramic fiber reinforced piston rind land technology. So a lot of what came out in later diesels came out of 2LTE/2LTHE testing. So it's very possible the throttled injector nozzles were sort of a 'high tech' feature that ultimately they decided not to continue. The ceramic precups I thought had huge potential, but they also dropped those. I think this is all in because they recognized TDI (turbo direct injection) engines were the future - and that is where they decided to invest development.

I do like some things about IDI turbo motors over TDI motors though. The higher compression ratio gives better out of boost low rpm torque. I like that the injectors can handle lower quality diesel with less filtration. The injection system on a whole seems more forgiving. They're easy to work on. Good 'apocalypse' motors, haha. Loss of heat energy into coolant from the pre-chamber is the main problem with them. This is why I really want to try those ceramic precups some day.