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Max boost only with WG hose pinched

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Hi All,

longtime reader, first time poster. Most of my build is a recipe from here and other parts of the community, so thanks. Finally thought Id join and contribute because Im spinning wheels in my head more than the truck on this issue. Also see if I can help contribute to other headaches too.


Issue relates to not achieving max boost out of the turbo, unless the wastegate is pinched. I dont see any boost leaks, and have plenty of fuel, more later.


in case sig doesn't appear or post. (Only listing relevant items)


2001 24v, S&B cai, banks monster ram, afe bladerunner, headstuds, hamilton valves and rods, DFI 7x.010, BD exhaust brake, Quadzilla,  3.54 on 275/70R18 (yes, its a little low on the gearing). Turbo is a Hx35 64/64 its set from factory at 40 psi. Valves adjusted recently.


Ive reached out to the vendor and theyve been helpful. Sent an additional WG actuator but have the same results. Im hoping Im missing something obvious.


Backing up a bit on build. Had RV275, hy35 j hook, original edge j w a. 0-60 8.5s not hard launch, at 34 psi boost (side note, this setup was almost completely clean except for boosted launches on 5x5 or other silly things also 19-21mpg). Bolted on this turbo, 0-60 7.5s at 29 psi.


Cool on right track, need more fuel I figure. Added DFI 150s and a quad. Still 29 psi..


Adjusted wastegate rod in, 34 psi max, about a dozen different times and adjustments. Used shop air gauge on boost reference hose to set 40-60 psi opening, with same results. Removed downpipe and plate, to visually inspect wastegate, appears all good.


Set quadzilla all the way frickin up, also different timing variations. 34 psi, and high egt cutout.(1400).


Built adapter plate for turbo intake to pressure test and look for leaks, all good. New MAP sensor from NAPA


The only way Ive found to go over that is pinching reference hose. Thats why Im leaning so heavy on the WG. Itll shoot up to 44 no problem quick, either my foot or defueler kicks in and backs out, and egts cooler (11-12?) these numbers are mostly from the quad, but had same from the edge too.

Please help, this is supposed to be the end of my build and having trouble. Id like to focus on more tuning soon and getting best mpgs out of this or possibly slight smaller injector setup.


Tomorrows saturday, so open to testing suggestions. Probably at least post a shot of hose pinched and unpinched. Although not handy with the excel to graph it.


Thanks for reading, and getting me this far along.








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Thanks for the replys guys,


So marine engines often dont have WGs. A C18 with twins going wot all day uses cpu to control boost pressure. So there is that route, but I feel theres a lot of advantages to a WG. Having it, Id like it to function semi properly.


Theory speaking. Isnt there a difference in drive pressure, load and egts between running 40 psi wastegate open, vs closed? Engines still getting max boost on intake side, while being able to vent more pressure on exhaust?


I like the boost elbow idea, seems pretty cheap and easy. If it works I know its still on the reference side. The other thought is drive pressure opening it before boost, so I could hook some mechanical gauges on the reference and exhaust. I don’t  think its as likely, and a bit more work. Try and post a screen shot later today.

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5 hours ago, SVALIN said:

So marine engines often dont have WGs. A


This is not surprising as marine engines have a lot more constants than truck engines have regarding air supply.  For example, an ocean going vessel's engine has atmospheric pressure and air temperature surrounding it that is relatively constant.  The engine is designed to move a load that will allow the engine to operate efficiently in a constant rpm range because the engine load is relatively constant.  Consequently, the turbocharger can easily be sized for a marine application that will keep the turbocharger in its efficiency range without risk of over speeding the shaft - so, no wastegate needed.


Truck engines on the other hand operate in more extremes of atmospheric pressure and air temperature - atmospheric pressure from sea level to over 11,000 feet in altitude, temperature from lower than minus 50°F to over 120°F.  They also operate under load within a wide engine rpm band - from just off idle to a high rpm repeatedly during each gear change in the transmission.


With tighter automotive emission standards, smaller turbochargers were introduced because they could supply more air into the engine's cylinders at much lower engine rpm's.  This made diesel engines perform better throughout the rpm range, thus improving engine performance as well as improving emissions.  To control a smaller turbocharger from over-boosting or over-speeding, a wastegate was added.


5 hours ago, SVALIN said:

Theory speaking. Isnt there a difference in drive pressure, load and egts between running 40 psi wastegate open, vs closed? Engines still getting max boost on intake side, while being able to vent more pressure on exhaust?


I think you would be okay to use any of the methods mentioned in previous posts. I don't think there would be a significant difference in EGT's or drive pressure at 40 psi boost whether the wastegate was open or not.  There are only so many oxygen molecules available to use in a given parcel of air at a given pressure and temperature to aid in the combustion process.  


And, of course, this whole post is just my opinion.


- John


Edited by Tractorman
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So I did 3 runs, have 2 data files. Theyre small, someone maybe can make sense before I can figure out how to excel graph them. On the run I dont have data for was canbus only. And that only pegged 36 psi with it closed, so Plugged off and no wire tap could be a ‘safeish’ way to run. On the open run I had wiretap at 5 instead of 6, and was going up slight grade. Only hit like 12xx EGT, Around 31 psi. So 5 of 6 of 1500 Wiretap is max. 

Well explained John for the marine use, they're constant use, constant conditions and ratings. Ex 24kw@3500 all day.


The turbo is a 12cm. The 62/xx are all the s300? This unit was more of a direct bolt on. have an exhaust brake. Was told the 7x.009 would be a better match, but read a lot about the .010 being good, so thought id go bigger, than not big enough and wonder more later. Thoughts on matching? With fuel prices I’m real tempted to swap my 275s back in. Although was seeing over 20 on the lie o meter. So far pretty happy with it, just stumped about this setting. Actually having issues tuning the down low power load egt and smoke, but that should be in a different thread.


Back to basic questions for laymen help. Anything Im missing in diagnosing low boost or leak?


SV WG Closed.csv SV WG Open.csv

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  • Owner

I'm using my stock HX35W turbo against my +150 HP injectors (7 x0.010 popped at 320 bar). Towed my RV and ATV in the back roughly 17,500 pounds total weight. No EGTs issues.20220505_140338.jpg


Gearing is extremely important. I'm 3.55 gears but with 245/75 R16 tires I'm 3.69 final to the ground so EGTs are rarely even an issue.

Edited by Mopar1973Man
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Little late to the party but here goes..


First, a question, why the 64/64/12? Diesels don't generally like the wheels being too close in diameter.. Causes surging in some cases. *not gospel, see he351cw, hx35/40 hybrids*


Second, try the boost elbow first (cheap and simple to swap) then do back pressure measurements. if back pressure is in the 1.5-2x more than boost range (if I'm remembering this correctly), its too high.. might be over 2x boost..  



On 5/21/2022 at 4:34 PM, Tractorman said:

I don't think there would be a significant difference in EGT's or drive pressure at 40 psi boost whether the wastegate was open or not.  There are only so many oxygen molecules available to use in a given parcel of air at a given pressure and temperature to aid in the combustion process.  


This is one of those where setup matters significantly for the outcome. If you are over fueled and trying to squeeze the exhaust into an he351cw's 9cm housing with the 60mm turbine, pressure is going to build up in the manifold and can cause essentially reversion and act as in cylinder egr. Swap it out with a larger turbine and or housing and suddenly things can breathe freer and back pressure drops. 


And here is where I think I'm arguing the wrong point on your statement :doh:


I think the only point that this would be an issue is in an over fueled small turbo. if you have more fuel to add to a wastegated small turbo, the turbo doesn't technically have anymore air to add to the extra fuel to cool things off. 


I think I need to chew on this a bit more.. 

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Thanks for responding more ideas the better!


6x6 Blade Billet Compressor Wheel (Inducer 63.5mm Exducer 86mm)

10 Blade Turbine Wheel (Inducer 76mm Exducer 64mm), 12 Cm housing


I needed direct bolt on and stock appearing. I thought 60/60 hybrids were fairly common, low issues. Thought be happier with slightly bigger.


I have the actuator rod adjusted all way in, about 60 psi to crack. Earns me 34 boost. EGTs on whole run never go over 1200, so when the boost is there, stays cool.


 I got parts and gauges laying around, so rigging together backpressure test after work.


Can drive pressure help pop the wastegate open, along from my reference actuator? As in both sides added together make the 60 psi?


Im having a heck of a time too, compiling graphs with a MAC version of excel (all I got). The secondary axis is all messed up. Any help with that? Already read and tried to follow Me(Nicks) guide.

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I did order an adjustable elbow, but for science, wasn't too hard to run back/drive pressure test. All these gauges/equipment are pretty rudimentary, but does decent job, and illustrates concept. Let me know if I missed a step. 


So Quad screen was with max, 1500ms pump. Previous test said wouldnt add more boost but thought Id try. That run almost went to 60 back pressure, also egt defuel, with 36 boost. Wiretap at 1000ms would’t go higher than 50 back, 36 boost. Normal driving was about 10 back, 7 boost. Accuracy of gauge isn't awesome though. Its 0-400 psi, with me driving and trying to watch it. Im trying to be as honest as possible about this for sciences sake.


Picture of the exhaust port tap, run to a hose, going to cab. Also In pic are boost reference pressure/ wastegate actuator setting. And turbo cap attached for boost leak testing. Obviously only one hooked up at a time. Though about adding a mechanical gauge to reference to compare to MAP, but not tonight. 

Bench pic of equipment. And gauge in cab. Im still leaning towards back pressure helping opening the wastegate. The adjustable elbow should help confirm that.






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Google sheets is what i use to make my quadzilla graphs. I find that since sheets is more stripped down it is easier to utilize.


After doing some digging, your turbo is a super hx40 10 blade turbine with a milled out hx35 compressor.. reverse hx35/40 hybrid essentially lol.


400 psi gauge is a bit on the high side.. 


If you are hitting 60 psi on back pressure, im not sure what the spring preload is, but im guessing that it would be blowing open...


Were those measurements with the wg plugged? Those are more what you would see with a 60/60/9 he351cw.. 

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Turbo is a P1 64/64 from puredieselpower. Sorry, wasnt trying to be obscure. Im doing this for generic data, and concepts too.


It was the gauge I had laying around for the afternoon. Lets say within 5 psi accuracy, maybe better. 

Wastegate unplugged, but max adjust in. Also near 60 psi open with reference hose. So doesn't open very much.


The 60 back pressure was with known overfueling for available boost. After 36 boost, ~50 BP, fuel just turns to egt and BP. About 10 psi for every 200 EGT is what Im calculating. So most accurate reasonable ratio is 36/50, maybe less.


I plugged it and ran for one more run home at 44 boost, unknown BP, but only 1120EGT.

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@dieselautopower, are the numbers he's saying normal? Just looking for some insight and other questions to ask..


@SVALIN, what are you looking to achieve? Figure out the boost difference from the waste gate being pinched off? Doesn't sound like you are having EGT issues or anything like that.. 



10 hours ago, SVALIN said:

Turbo is a P1 64/64 from puredieselpower. Sorry, wasnt trying to be obscure. Im doing this for generic data, and concepts too.


I'm not implying anything other than the turbo you have has hx40 parts stuffed in it. :surrender: Not a bad thing either, I've just never seen those wheels used together.. Usually people go all the way to the 67mm turbine wheel with some combo of the 60, 62, 64, or 67mm compressor wheels available for the HX35. 

Edited by Silverwolf2691
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@Silverwolf2691 No need for white flag brother, Im not married to this thing, just having trouble running in circles trying to get it to work properly.

Achieve, 1) max efficiency out of the unit, its supposed to get or be at 40, and I see good performance when tweaking to get those numbers. 
2) Understand/trouble shooting wastegate actuator settings and effects. Appreciate all going after my specific issue, but I feel theres a lot of generic info to be learned here too.

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42 minutes ago, SVALIN said:

No need for white flag brother


:thumb1: Can never tell with text only, caused more than a few arguments with my ex-gf..


Might be running into efficiency issues with the actual housing.. The compressor housing is only meant to flow like 50-60 lbs of air through it.. you have a wheel that similarly sized s363's flows over 70lbs, with the even larger s364.5 flowing at or over 80 lbs.. I know that there's more too it than just putting up numbers. Especially since the sx-e isn't even from the same company but I'm working with what I got..

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@dieselautopower Thanks for joining!

9 minutes ago, dieselautopower said:

36/60 drive pressure is a lot.


Typically it is best to gate earlier and let the exhaust gas leave the engine. 



For sure, thats almost 2:1. I mentioned I was purposely over fueling for data. Its closer to 36:50, still not optimal. The actuator rod is almost all the way in, so gate isnt far open..


When Im running up at 40-44, the EGTs are a lot lower, so wouldn’t be surprised if staying at 50 BP still. Around 20 boost was closer to 20ish BP.

So thats where Im getting confused at setting. When I make 40-44 boost, EGTs are good, BP prolly closer.. But only can happen when I plug the boost reference hose. But wheel wants to overspeed..(hits defuel setting).

When I leave hose unplugged and adjusted in, Im only making 36 PSI at max adjust, with 300+ Higher egts.


So a plugged off wastegate gives me LESS Egt???

Next step theory I think is to bring actuator rod back to 50 lbs, and close off most of the reference air with the adjustable elbow. 

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I have a feeling you are hitting the choke point on the 12cm housing but that isn't supported by the plugged off wastegate..  :think:


I wonder if the center wall is not drilled.. HX35s only relieve the back 3 cylinders when the wastegate opens..


Could be an efficiency thing? IDK I'm stretching for answers at the moment.. 


Wait.. were your tests wastegate plugged or functioning? and what half of the motor are you reading from? first three or last three?

Might (should) see differences front half and back half of motor with a working wastegate and a non-drilled turbine housing..

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Appreciate the head scratching.


Center wall is drilled, 1”ish port right after bolts to manifold. 

the drive pressure tests were with it “functioning” adjusted to open at 60 psi boost reference.


Drive pressure gauge hooked to bank 2. But can do either or. With the dual volute wall drilled, not sure it matters much. Think thats what you’re getting at. 

I guess I can do another drive pressure test after work today with it plugged off. See if I do get 44 boost/ <50 BP.

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