Not Holding Boost! Hks 2835 Pro S .87 A/r

[89CAL]

It may be your issue if you modified it. Do you have access to a compressor, pressure reg and some airline so you can actuate it with air to test how well it moves?

Might be able to pick up a "notchy"section of movement or perhaps it gets stuck somewhere etc

Worth a shot

[LaurelPWR]

I did do all that at the start when all this first started but I can't remember for sure how it all went... Worth another try tho for sure

[89CAL]

I think it definetly couldnt hurt. I had a HKS GT2835KAI on my old engine and boost held perfect even though it used the nissan 6 bolt flange instead of the HKS flange which I believe flows a little better

[LaurelPWR]

So I put around 22-23psi through the actuator and it opens and closes no worries and the linkage has roughly 10-15mm of travel out & in....

Everything in this situation has checked out normal and ok.... The only thing left to do is drop the exhaust completely and test boost again and then remove the turbo and have it inspected

[LaurelPWR]

I did another boost leak test last weekend as my usual preventative maintenance... I normally put my "tap" tool into the start of the cooler hot pipe directly after the compressor outlet... But for a change I pressurised the compressor as well this time.. I put the "tap" at the statue of my air intake where the air flow meter normally goes and then put the usual 30-35psi through the system with my compressor and controlled via twin regulators and than spray soapy water on everything and look/listen for the bubble..
I found that the screws that hold the comp housing to the backing plate are leaking through their threads as the threaded holes go all the way through to the inside of the comp housing. I removed each bolt one at a time and liberally put some loctite 567 heigh pressure thread sealant on each one drove them back home... Retested and Problem solved. No leaks anywhere else. Then I checked and Re-tightened my four t3 flange bolts just to be sure (one was a little loose for my liking), hosed all the soap off and started the car to dry out the engine bay.

This is when I noticed a strange reverberating, tinny, rattling sort of a noise at the dump/front pipe area... I had always heard a similar noise from that area since the HKS 2835 pro S went on the motor and always just assumed it was engine reverberation noise caused by the stainless HKS dump and Hpi stainless front pipe that went on at the same time as the turbo swap...my previous exhaust on the previous turbo was mild steel from turbo back..
I used a large screwdriver and long piece of aluminium angle as a stethoscope and located the exact location of the noise and turns out its coming directly from the internal waste gate mechanism...
I'm guessing the gate poppet isn't fully seating and rattling around in there hahaha..
As seen earlier in this thread, I replaced the actuator with a bew turbosmart unit and put 21psi Springs in it and pre-loaded the f**k out of it to get it to maintain some sort of boost and get a tune happening... Now I finally think nice located the issue!!
Dump is coming off hopefully this weekend and I might get to the bottom of this once and for all!!

[LaurelPWR]

Here's a video of the noise in the specific area and then the noise through the diy "stethoscope" ..

waste gate noise.MOV

[LaurelPWR]

SO.......,

It turns out the actuator bracket wasn't fixed stable and had movement when the actuator was loading and unloading boost...

The noise it was making in my last post above was the internal gate flapper rattling around in the breeze at idle [emoji17]

Because the actuator itself was moving around, the gate preload was changing or being lost altogether.

I ended up welding the actuator brackets together to eliminate any movement and then I cut the linkage down and loaded a bit more preload and back to the dyno today.

 

It now makes boost earlier than it ever has, made 20ish more peak HP and picked up 100hp at 3700rpm

 

For a turbo of this size, it's quite a stout result and I now feel it's performing like it always should have... Remembering it's the .87 ar rear as opposed to all other 2835 pro S results on rb25's are .68 ar

 

The car feels much faster on the road now and even my 315/30 nt01's can't cope anymore with this small but decent gain hahah [emoji4]

 

 

 

[Lithium]

That all makes sense, very nice result - always good to see threads like this updated after resolution, too

[LaurelPWR]

That all makes sense, very nice result - always good to see threads like this updated after resolution, too [emoji4]

Thanks Lith [emoji4]
Would be interesting to see this setup with an external gate set up now [emoji848]
But that won't be happening haha

Now I'm just hoping my new hta3076 twin scroll setup can give same sort of response and a father mid/top end power band

[kingtube69]

Great news! I just saw your post in the RB dyno results page and quickly came over here to check what the fix was. Response still looks great too. 

[LaurelPWR]

Great news! I just saw your post in the RB dyno results page and quickly came over here to check what the fix was. Response still looks great too. 

Thanks man (:
It's very responsive having 240kw at 4krpm makes for a very fun street car indeed.

[iruvyouskyrine]

Chuck some pics of the engine/car up! Looks like it would be extremely fun on the street

[LaurelPWR]

[LaurelPWR]

Dropped these to 5psi tonigh for roll racing and still getting the odd wheel spin on launch and change to 3rd haha