YD25 Compound Turbo

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The bloke with the d40 manifold and turbo was making 228Hp. You are right he had a hi flow'ed core put in with 11 blades. +30% injectors, 4" snorkel and air box and was running a HKS module. The majority of the work was done by just autos, a well respected tuning company who have great success with the D4D found in the Lux's and Prados I suspect he is running a very rich tune with the amount of black smoke he is blowing. This is fine for smashing around town but for sustained racing it wont last long.

Yes I would still go compounds again. I believe they are the best way to achieve the highest mass flow rate of any turbo system at both low and hi rpm. I have focused my latest efforts on improving my intercooling system with a larger pump and radiator. I have calculated I can pull 8 x more energy out of the water than what my previous setup could achieve.

I think a lot of people don't understand the importance of IAT (Intake air temps) and Mass Flow Rate when building a turbo system. Keeping the IAT's cool is far more important than how much boost you are running.

Another point to consider is oil temp and water temp, if you keep these fluids at their working temp then this will greatly aid in keeping the turbo cool and also reduce the heat compressing the air generates
 
^^^ and extending the life of the components and our engines...ive found cooked oil....even 4000km old oil thats had a hard life will greatly increase my egts.
 
I've been doing a fair bit of research into it, although I still know bugger all compared to a reputable tuner.
 
Ok, sorry to butt in, and i love seeing people thinking outside the box and getting their hands dirty making it happen, but have you considered just using a Borg Warner EFR if you want super response and stupid boost?

I havn't looked into it for this application, but i dare say there would be something in their line up that will do what you are trying to do, although just buying a nice shiny hi-tech bit of hardware wouldnt be in the same spirit as what you are doing!

Just thinking about it and correct me if I'm wrong, but for arguments sake you want to push twice the air mass and you want twice the spool, so you run a compound set up with a turbo twice the size feeding a turbo of std size - but do you have enough exhaust energy to make all that get up and spinning sooner rather than later? Not to mention the added complexity of it all!

http://www.turbos.bwauto.com/files/pdf/dimensional_reference/efr/EFR 6258-A.pdf
 
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You have pretty much hit the nail on the head of the coffin with that Rabbid-chop. Extracting the most energy out of the exhaust gases at any given time to produce the required mass flow rate of air at a useable temp. This is why I think compounds are so effective as you are using the exhaust gases twice, extracting the most energy out of them as possible before passing into the exhaust system.

Ive done some calcs on turbo sizing and with a 3:1 pressure ration and 36 lbs/min flow rate to get the desired 30lbs of boost I want for racing this turbo would easily achieve that with 74% efficiency.

The secondary turbo on my setup has a 0.6A/R on the cold side and the hot side is 0.5A/R. Its designed to spool quick and only makes 10 - 12psi at say 3000rpm, but that's all the system needs, the stock primary turbo runs at say 18 - 20psi, well within its map and together make the desired 30psi of boost by about 2500rpm.
 
Im hoping by running lower IAT's. I can use less fuel to achieve similar Hp while still running a 19:1 AFR which is safe for 2 hrs of hard racing
 
Must say if turn the chips down to get the 19ish:1 AFRs my temps are totally managable and well within limits for a lengthy spirited run.even at 17-18:1 its not too hot.
 
Well we only made 166RwHp and 383Nm so I was pretty disappointed with the numbers. It actually drives really well but I seem to think that's more to do with the diff gears.

We tuned the compound system by keeping the stock Nissan turbo set to 16psi and wound the secondary turbo up to between 16 - 18 psi.

After doing some considerable research and speaking to a turbo expert from Germany we have discovered that we have tuned the system the wrong way around. We essentially need to run 10 - 12psi through the secondary and then tune off the primary turbo.

I have bought another boost gauge and some copper piping so we can measure the drive pressure generated by the engine going through both turbos to determine the efficiency of the exhaust wheels.

I have all of my EGT gauges working now so we can plot EGT vs RPM on logworks. This will show us how hard the turbos are working and how much energy they are pulling out of the exhaust gases. I will post up my findings in the coming weeks

Dilmah
 
Well at full noise its over 35psi.... and thats just off the primary turbo

I guess we will find out during the testing sessions

I will eventually need bigger injectors too
 
Good luck bro

If your keen on fiddlin wid turbos you should probly buy a skyline 😂

That said good on ya for givin it a go, hope it works out for you

Keep us posted on the results
 
The Compound Turbo is up for sale $1500 gets you the complete kit. I have changed directions with my turbo setup due to needing more space for shock towers. PM me if interested. Price is firm but willing to split shipping
 
Is there anyway of browsing your photos mate? They won't load for some reason, just want to get an idea of how you positioned them and room etc. I'm working in with G&L performance and starting to compound mine in 2 weeks, will be chaseing high 300's on gas.

If I was you I'd use a turbo similar to my current one, a gtx2056v, a hi flowed d40 128kw motor turbo. You'll see good figures and early boost ��
 
hmm not really....photo bucket has changed all of their privacy settings so you cannot 3rd party host on forums unless you pay a yearly subscription. Room was at a premium in my engine bay and you will struggle to make big power unless you can somehow fit an interstage cooler in between the 2 turbos.

Yes my VNT is based off a 2056 but it has different wheels in it and the front housing is slightly bigger. It also has a thicker shaft
 
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