A Nissan Sentra Forum banner
1 - 13 of 13 Posts

·
Registered
Joined
·
5 Posts
Discussion Starter · #1 ·
Hi all,

This is my first post here on this forum, I made an account because there seems to be a lack of widespread knowledge regarding the QR25DD.

To provide context, I became a B15 Spec V owner in April of 2020 and after doing a compression test and diagnosing the piston rings as less than desirable condition, I decided to buy a JDM motor to swap into the car this year. I sought out the best deal I could find, and I came upon a JDM seller (I'll leave anonymous for now since I'm still trying to work things out with the guy) who had a good deal on a QR25. Before shipping it to me, he informed me that the intake manifold looked different than the other QR25's he had and he wanted to confirm that I was ok with this. To me, that wasn't a big deal since I could just swap my intake manifold if the one on the JDM motor wouldn't work for me. Flash forward to when I receive the motor and now I'm starting to see that I have made a mistake.

The following is a sort of report that I emailed to my seller to try to explain why this was a QR25DD, not a QR25DE motor like he had listed on his seller's page, and what makes these motors so different.


"To elaborate on our conversation over the phone, I'd like to go over the details of the differences between the QR25DD (the engine I received) and the QR25DE (the engine I need). I was ignorant to the existence of the QR25DD because I had never seen one before and this motor was never used in a USDM production vehicle, hence the lack of widespread information available for it. I haven't written this out to try to say "I got ya", I'm trying to be transparent as to why the engine is different so that there isn't any confusion as to why it won't work for me.

Rectangle Font Water Circle Magenta

Nissan QR engine - Wikipedia

On QR engine page of wikipedia, it details the differences between the QR types such as the QR25DE and the QR25DD. The biggest difference here is that the head of the QR25DD is engineered for direct injection. This means that the fuel injectors are mounted directly to the head rather than the intake manifold as found in the QR25DE. The other big difference is that the pistons increase the compression ratio of the QR25DD, and you must have the correct ECU for correct ignition timing.
Camshaft Font Automotive air manifold Automotive wheel system Gas

CYLINDER HEAD NISSAN QR20 QR25 DD NEO Di FOR SENTRA BLUEBIRD PRIMERA 2003-09 | eBay

The picture above is an ebay listing for a QR25DD head. I've added arrows that point to the key details that make this intake ports different from its QR25DE counterpart which I've attached below.
Automotive design Automotive exterior Gas Automotive wheel system Auto part

Nissan QR20DE QR25DE Cylinder Head

The other main difference is that the back of the head on the QR25DD uses a mechanical fuel pump that is actuated by the exhaust camshaft. I'm adding a photo below of the QR25DD engine sent to me for reference, and a photo of your QR25DE (#XXXX) to show the difference.
Automotive tire Motor vehicle Gas Engineering Auto part



On any USDM production vehicle with a QR25DE, the fuel lines go directly to the fuel rail located on the intake manifold. On this QR25DD, the fuel lines would go to this mechanical fuel pump before the fuel is injected into the engine, but no USDM vehicles can support this without custom modification.

I realize that I was sold a QR25 and that I agreed to pay for an engine with a different intake manifold, but the listing and billing invoice said that it was a QR25DE, not a QR25DD. There are crucial differences beyond the intake manifold that make this motor unfeasible for my application, hence why I'm inquiring about it and why I said that there was another QR25 (#XXXX) that needs the description changed from QR25DE to QR25DD to prevent any confusion in the future."

I will also attach more pictures below of the motor I received so that anyone else who is shopping for a QR25DE will know what to stay away from. I had to pay for shipping to return the QR25DD and to send the QR25DE so I don't want anyone else to have to make that mistake.
 

Attachments

·
Administrator
Joined
·
6,791 Posts
A long time ago I wanted to get a dd head to do a hybrid or just try and run a dd.... might think about it again as they should be really cheap.
 

·
Registered
Joined
·
5 Posts
Discussion Starter · #4 ·
A long time ago I wanted to get a dd head to do a hybrid or just try and run a dd.... might think about it again as they should be really cheap.
They are pretty cheap considering there are no USDM vehicles that use them, so there really isn't a demand for them. The issue is that it seems like these sellers don't know the difference between the DE and DD, so it's all the same QR25 to them.


When I figured out what I had, I was considering throwing my DE head onto the DD block for a higher compression motor, but to do that correctly would require at least a head gasket kit, timing kit, and a tune to make it all function... My budget just isn't there for my B15 at this moment and swapping a DE seems like less work.
 

·
Registered
Joined
·
593 Posts
You can plug the holes for the head for the DI system. Have dowels made that are ~.010 over-sized. have the dowels frozen in some liquid nitrogen. slide them into the holes on the head. they will expand and seal it up perfect. Then you just run a port injection system. Cap off where the hpfp goes. Ready to rock and roll. Literally doing this to port injection swap MR16 engines.
 

·
Registered
Joined
·
5,829 Posts
Thank you for the info on this. Yeah I dont think I was aware of the DD model or just forgotten. It looks like it also has an egr pipe.

Is there any way you can just swap the head form your old DE? Even if the pistons are different it should still run fine. Or just rebuild the DE.
 

·
Registered
Joined
·
5,829 Posts
It sounds like alot of trouble to go through for that conversion for a stock motor
 

·
Registered
Joined
·
5 Posts
Discussion Starter · #8 ·
You can plug the holes for the head for the DI system. Have dowels made that are ~.010 over-sized. have the dowels frozen in some liquid nitrogen. slide them into the holes on the head. they will expand and seal it up perfect. Then you just run a port injection system. Cap off where the hpfp goes. Ready to rock and roll. Literally doing this to port injection swap MR16 engines.
You could do that but it seems like there’s too much work when port injection heads are readily accessible in any junkyard. You would also have to make a custom intake manifold since the DD intake manifold port pattern and bolt pattern is completely different from the DE. If I had to guess, I would say that the DE head probably flows better than the DD head since it has one big intake port per cylinder vs 2 little ports per cylinder, but I can’t back that up with anything.
 

·
Registered
Joined
·
5 Posts
Discussion Starter · #9 ·
Thank you for the info on this. Yeah I dont think I was aware of the DD model or just forgotten. It looks like it also has an egr pipe.

Is there any way you can just swap the head form your old DE? Even if the pistons are different it should still run fine. Or just rebuild the DE.
I haven’t taken the DD or DE engines apart so I can’t 100% confirm this, but the blocks look the same and if I had to guess then I would say the head bolt pattern is the same so the heads should be interchangeable.
I’m afraid of the engine having ignition timing issues with the higher compression pistons (edit: on a stock ECU) , so if I were to use the block then I would absolutely get it tuned and right now that costs more money than it would be worth for me. Would it be cool? Of course. It just makes less sense financially to build a higher compression motor or rebuild my current motor when it’s cheaper to swap in a lower milage motor. But that’s just me.
 

·
Registered
Joined
·
5,829 Posts
I totally understand that and thats what I mean. Piston size or stroke length shouldnt matter. Ive seen qr20's swapped that dont make the power of a QR25 but still runs and no CEL. Its probly a very small difference is anything. But Im sure you can find that info on the specs just to know. The pistons might be a bit higher compression but not high compression pistons. You shouldnt have to tune it. Also assuming the head bolt pattern is the same.

Its a shitty complication to be in but I guess gotta just make out with what you have.
 
  • Like
Reactions: Tritton

·
One of One???
Joined
·
1,514 Posts
At 5l in a qr20. Less power, no cel or timing issues. Runs like a champ. Swap the heads. ;)
 
1 - 13 of 13 Posts
Top