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Can't boost above 22psi with the wastegate plugged


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Long time reader first time poster. This is most likely my last resort since I've searched all I could to find out the issue. My truck has never boosted correctly since I got it. I'm running a V2 tune from on this forum and it's been great until I get to 22psi. Then that's all she's got. My boost gauge just sits there. And that's with my foot to the floor. Clamped the wastegate line and still nothing. Any insight would be greatly appreciated. Thank you!

Edited by Rather Be Wheeling
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Sounds like maybe the boost fooler in the quad  may not be working. 20 to 22 psi is about where the ECM would start defuelung the engine to protect it from over boosting. Have you checked for trouble codes? I would expect to see an over boost boost code.

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Valid point on yhe boost leak, could be either one. I lost a 4" piece of intake plenum gasket that did the same thing. But we have had some folks with boost fooler issues lately also

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Give you a clue.

 

Normally I can hit 47 PSI. I pulled the wastegate hose off and left it open, then pulled 1 bolt out of the manifold. It whistles very loud but I was still hitting 43 PSI of boost. So a boost leak will not hold back boost pressure unless it super huge leak. So, with two big holes in the air system a bolt missing and wastegate hose hanging only lost 5 PSI. (HX35/40 hybrid turbo 60/60/12).

 

Tuning has way more to do with boost. Improper timing will cause weak boost typically over advanced. Too little fuel in the CANBus fueling table will make it weak too. Running the wrong level. Like switch from wiretap level to Level 3 I can drop to a max of 35 PSI of boost. 

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@Rather Be Wheeling can you post the specs/mods your truck has? What injectors, what turbo, auto or manual, year, etc. Also if you can, it's helpful to put this information in your signature so you don't have to keep typing it.

Here's what I'm seeing in your datalog.

 

You rarely went over 40-50% throttle, but I did find a section where you went to 100% throttle, but only for 4 seconds.

 

I see you got to 26psi, full fuel command and no back down.

 

Your EGT probe isn't hooked up so we can't see what's going on there to rule out a crazy excessive boost leak, which would be evident by really high temps.

 

Fuel pressure sensor isn't hooked up, so we can't tell if the VP is being starved of fuel.

 

If you are on level 3, you could try throwing in some wiretap (level 4 and above) and see how it likes it.

 

Your RPM jumps to 3k pretty quick when you stabbed the throttle, so I'm assuming you have an automatic trans and the converter unlocked, and didn't have a chance to lock up before you let off the throttle. These trucks need some load to get the boost up. You will be able to see a difference in WOT boost unlocked vs locked. Is your converter lockup slipping?

 

Need more info for an accurate assessment.

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Sorry about that I thought my signature was on here when I registered. I guess it didn't save.

 

It's an 01 with an hx40 with a billet wheel, rv275s, afe intake and elbow, quad V2, fass 165 with a Vulcan draw straw, thoroughbred pump, straight piped, triple disc converter, billet and Kevlar everything, shift kit, etc

 

All the parts except the turbo have under 4k on them. The transmission has like 250 miles on it itself

 

Yeah the quadzilla was on the truck when I bought it. I have mechanical gauges for the egts and fuel pressure so I never figured to plug those in to the quad

 

I know for a fact I'm reading 15 on my fuel and it's barely dropping at WOT

 

And my EGTs on those pills hit around 1200 if I'm not mistaken. I'll go drive it again today and document both the EGTs and Fuel Pressure

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Sorry for the late reply. I forgot to hook up the egt on the quad but I did do another pull almost the exact same and my pyro gauge on my pillar read 1200 with my foot to the floor

 

I'm running a medium tune all the way up on 5 (no head studs so I don't wanna push my luck running a hot tune) but I think even with the medium tune and the 275s I should at least be seeing 30 psi? I could be wrong tho. I'll re check for a boost leak this weekend

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I would not be to concerned about max boost but watch how the truck makes it.

Does it easily make 10 -psi to 20 will it go near 30 with some spirited pedal imput.

 

Is she light on here feet or moving like  big girl packn a fistful of cookies with crumbs all over.

 

I wouldn't be afraid to turn timng off and give it a spin 

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Quadzilla you can do a bunch with. Turn the level all the way up. Then do a few test runs. 

 

@Rather Be Wheeling you should take a peek at the tuning guides. I've got one and Nick has one. You are safe to running 40 PSI without studs. I've done that for years. With my old Edge Comp I could tap the 37 to 39 PSI. (10 years! running 5x5) Above 40 PSI I start to get worried between the stock turbo is running out side it design map and the head bolt will now start to see stress above 40 or 45 PSI possibly.

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