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Boost issues - exhaust flow opening waste gate possible?

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Hi guys ,

Greetings from the UK . I’m having some weird issues with boost on one of my cars and I’m kind of in a dead end, so I decided to get some more opinions and thoughts. Car is a Volvo 940 2.0 Turbo. My old TD04-16T gave up after severely cracking waste gate port and not being able to make more than 6-7Psi, so I had a TD05H-16G from a customer’s EVO 6 , which turned out to be spinning in reverse direction , so I converted it to a t3 exhaust housing(brand new one )in order to fit it to the Volvo , replaced the turbine wheel with new 9 blade upgraded one with forward rotation one , billet 6/6 compressor wheel with forward rotation, ported the exhaust manifold to turbo and to head as well(head is ported as well ), using a EVO Forge internal waste gate, modified to fit the Frankenstein I made, All good by now, except when testing,it didnt boost more than 6 psi, ran it only on the waste gate spring ,same boost , then Blocked off the Recirculating valve so I rule it out of the picture , then did a boost leak test, turned all good. As a last resort I did preload the waste gate more and managed to get only 9psi of it with boost control or without ( Manual Boost Controller).The only thing in my mind left is exhaust flow opening the waste gate, but the weirdest thing is with the same actuator I did run 18 psi on the 16T turbo, and before that 18psi on the EVO 6 as well, so I’m kind of out of ideas except gate opening under the pressure of gases. I would be extremely grateful if you give any opinions !

Regards

Michael

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Have you considered testing this theory by measuring the back pressure in the exhaust manifold, and then replicating that on the bench to see if the wastgate opens?

That would be possible if you have the means to measure back pressure, on this one I’m using the original Volvo manifold modified, so that’s not an option I guess, I’m planing on checking flapper surface area on the different housing that the wastegate was used before , as it is significantly greater it would probably force it open, also the wastegate has a lower port that when presented with pressure membrane should try to keep it closed.

Have you tried free boost exercise - is it able to give higher boost? 99 percent of the time the problem is wither with internal waste gate, boost solenoid or incorrect hoses connection...

Have you checked the waste gate is actually sealing correctly? There have even been times when the seat has been left out by accident.

Housing is brand new and before putting it all back together that was the first thing that I checked , flapper seals properly and moves freely, sleeve of the push rod is checked as well no matter it’s new, as I’ve seen sleeve popping out causing the flapper to move away from housing opening and loosing boost. It’s an absolute bummer as I do have quite fair amount with Turbos and pretty much checked and ruled out everything so far.

So how much is it giving you in free boost mod?

This is a Volvo , not a Mitsubishi running a stock solenoid that has a restrictor on it , if that’s what you refer to as free boost mod , I run a simple manual boost controller.

Ok, I'll put it this way - what is the maximum boost without boost control?

Same as the max I can reach with boost control - 9psi

Impossible. If your hoses connected properly and the waste gate seals as it supposed to you should get overboosting big time. Chech it out one more time. I have seen it in a few different cases - people were absolutely sure everything was 100 percent right but it wasn't.

I don’t think we understand each other , but that’s fine thanks for trying to help .