Sr20det not holding boost!

[5t341tH]

Hey guys. I've been having this issue for a while now and decided to post up. I have a s13 sr20det in my Datsun that I've been getting dyno tuned for a while. The issue is the the engine isn't holding boost. It will boost up set pressure but would taper off. My tuner and I have boost leak tested this engine and have seen leaks before which we all fixed but now there are none. The engine has a gtx2860 gen 2 internal wastegate with hks actuator, greddy manifold and Tomei poncams. We tested on wastegate pressure only and it would spike to 14 before dropping down to 10 which should be the spring pressure. Very strange for the initial spike in pressure to 14 before dropping off. What areas are common for the boost to drop off to?

[S14rebuild]

Ditch the internal wastegate and go with a larger EXTERNAL wastegate and a good dual port boost controller

[5t341tH]

I am trying to stick with internal wastegate. Also I have a innovate motorsports boost controller

[zombiewolf513]

Sounds like the actuator isn't opening fast enough on low boost, and getting blown open on high boost. Maybe something to do with the positioning of the actuator with respect to its action?

[5t341tH]

Originally Posted by zombiewolf513

Sounds like the actuator isn't opening fast enough on low boost, and getting blown open on high boost. Maybe something to do with the positioning of the actuator with respect to its action?

thats a possibility. The way the actuator mounts is a custom setup that I came up with. In my datsun it has very little room on the turbo side, so I had to mount it on the compressor housing. I will double check it actuates smoothly. But that wouldn't cause it to not hold boost right?

[S14rebuild]

If the wastegate is stuck holdn the flap open...no boost will build

[zombiewolf513]

You might have it adjusted such that the wastegates open position is at the maximum range of the actuator. Making the actuator too weak to reel the wastegate back in when youre at high boost exhaust gas pressures. Just a guess tho. Maybe theres a pinhole or rip in the diaphragm or canister, causing a leak in the actuators pressure differential.

You might want to consider welding the internal wastegate shut and buying a codyace modded exhaust manifold for an external wastegate for your tight fitment issues.


https://forums.nicoclub.com/93-saphi...r-t552332.html

[Dboyizmlg]

Originally Posted by 5t341tH

Hey guys. I've been having this issue for a while now and decided to post up. I have a s13 sr20det in my Datsun that I've been getting dyno tuned for a while. The issue is the the engine isn't holding boost. It will boost up set pressure but would taper off. My tuner and I have boost leak tested this engine and have seen leaks before which we all fixed but now there are none. The engine has a gtx2860 gen 2 internal wastegate with hks actuator, greddy manifold and Tomei poncams. We tested on wastegate pressure only and it would spike to 14 before dropping down to 10 which should be the spring pressure. Very strange for the initial spike in pressure to 14 before dropping off. What areas are common for the boost to drop off to?

HKS actuators can hold around 18psi steady boost before they start dropping off... depending on your turbo choice also..
I had a 2871r on a similar set up like yours before and it held boost at 19psi no issues with spike or drop.

I also had an HKS EBC

[5t341tH]

I am trying to keep this internally wastegated. I bought this turbo new with the t25 flange and 5 bolt so I could keep internal wastegate. The hks actuator is also new. I modified the arm on the actuator so it can clear my steering column in the datsun. The arm has been shortened and bent at an angle.

[S14rebuild]

Originally Posted by 5t341tH

I am trying to keep this internally wastegated. I bought this turbo new with the t25 flange and 5 bolt so I could keep internal wastegate. The hks actuator is also new. I modified the arm on the actuator so it can clear my steering column in the datsun. The arm has been shortened and bent at an angle.

Pull the turbo outlet off and actuate the wastegate and see if the flapper is fully closing and can swing freely... visually look and confirm


Then test the wastegate with compressed air/regulator...

[PoorMans180SX]

Put more preload on the gate. Use more duty cycle in the boost controller on the top end. Test the gate crack pressure with a pump.

I don't know what HKS gates are supposed to open at, but I highly doubt it's 10psi.