YD25 Compound Turbo

Well its been mentioned in a few other threads but I though it was time to start a dedicated thread for this build. As most of you know I like to be a bit different with the mods I do to my Nav, choosing to do things not many others have attempted or done.

I bought this kit off a tuner in QLD as a one off prototype so its pretty much bolt up with some minor alterations. I haven't made much progress as I only started it last night but the dump pipe is off and the new pipe which link the exhaust side of the primary to the secondary is in place.

Bit of terminology before we start:

Primary - original high pressure turbo, smaller than the secondary
Secondary - aftermarket low pressure turbo, a lot larger than the primary

I'm hoping to bolt the turbo up early next week and put the secondary hot side pipework in as well. With the Unichip, W2A and compound setup I'm hoping for around 170rwkw @30psi. I'm going to run 18psi in the primary and 12psi in the secondary. By keeping the primary well within its map it should make good power.

Will post pics next week

Cheers

Dyl

Cant wait mate

I Always enjoy reading about anyone doing some pioneering! Wether it be sucessfull or failure many lessons are learnt,

The kiddies on the d22 Facebook page are going to explode with relentless claims and questions now. be warned....Lol

dilmah said:

.....compound setup I'm hoping for around 170rwkw @30psi. I'm going to run 18psi in the primary and 12psi in the secondary.

Click to expand...

i'm a little rusty on it but 18psi with 12 psi on the inlet side give you about 45lb boost. which is good because 30lb can be done with a single turbo.

also i thought you have to have primary set to the boost figure you want, otherwise you loose drive pressure. but then again i'm rusty as hell.

Think of it this way, the primary will be receiving air at 12psi instead of atmospheric. Look up compound turbo on google images for a picture on the piping setup. Its different to sequential and twin turbos. 30psi will be the manifold pressure. Don't want to go any higher as it will significantly shorten the life of the head gasket.

been a while since i looked at compounds.
is it worth doing for 30psi ? you could do that with better efficiency with a well sorted single turbo.
but then again a compound is sweet as.

dropping secondary down to 5 psi would give you 30psi. that also will save on intercooling between the turbos.

There isn't really anything on the market ATM for the YD25 that is proven to make good power. No one has done the R&R that companies like United have done for the TD42 or Gturbo have done for the land cruisers. Ill see how this goes first

Are you sure you know what you are doing ?...reason I ask is are you a fiddler--trial and error OR have a sound engineering background that understands

what else are you going to do to support the extra pressures ?

Ah I have heard of these setups before, turbo's in series. Looks like it will be an interesting setup.

I have a degree in physics with a major in materials science. Ive also done a fair amount of research before attempting this. The secondary turbo has already been matched to the stock Navara one in terms of how it flows the air on both the hot and cold side.

Once the turbo is installed I will take the Nav straight to the tuning shop to get it tuned correctly. Im going to start off with 25psi at the inlet manifold and take it from there.

what sort of turbo for the secondary?
normal or variable ?

i don't see any problem running compound turbo's apart from it might be a bit pointless at those boost pressures.
bigger issue will be getting enough fuel in there and also any other restrictions like inlet manifolds etc.

Normal, .60 trim on the cold side and .48 trim on the hot side so it will spool nice and early.
Fuelling will be and issue above 25psi. I'm trying to get Bailey's to send me some bigger injectors but not having much luck.

I would love to make a new manifold but don't have the time or skill to weld cast Ally

New hot side pipe is plumbed up. Old dump pipe is removed then this pipe directs the exhaust flow to the secondary turbo's hot side. This part was a pain in the arse and took me about 6 hours to do. The 4 bolts are in shit spots and extremely hard to get to even with a body lift, they are also pretty tight. Soaked them with WD40 and then hit it with some heat and they came off ok once I could get a socket or spanner on them





Here is the turbo, 0.6 trim on the cold side and 0.48 trim on the hot side. It will spool nice and quick!

Can you post the turbo maps and explain how you have matched them please ?

I didn't, the guy who designed the kit did all of the work. I just have to bolt it up and get it tuned

Made some more progress today, plumbed up the oil supply and oil drain. Pretty much just taps into the existing lines. Was a pain in the arse to fit due to the coil tower being in the way. I had to take the wheel off so I could get close enough to the block

Fair play to you mate. Great to see someone doing things like this. Very interested to see how it goes once done

More pics







After that I had to pack up and go to work. I did sit the turbo on top and had to bend the AC hose from the compressor to the cab around the turbo but now I cant fit the dump pipe on the back of the secondary as the AC piping is still in the way. Will need to move the piping away from the dump pipe which could require me to degas the A/C

This is turning out nice, can't wait to see the end result.

Very nice work, you got custom headers on it? I know it would be tricky to try squeeze in there too but equal length headers would go sweet with this.

How much you going to try work this thing? Have you thought about a custom intake manifold?