Dropping boost at high RPM? Help

[VitViper]

That's pretty typical behavior with those turbos, they have a really crappy IWG canister design. I've done dozens upon dozens of cars with those turbos and it's always the same story. When we put an EWG housing on it and run an external gate... no problem, and then the turbo is decent.

[Toyarzee]

Originally Posted by NahumCC

Actually, if you look since about the mid 2000's you'll see the integral BOV as part of the compressor housing has been around on the common factory turbo's from Garrett and Mitsubishi in larger numbers.


The benefit of having moved the BPV into the compressor housing goes to the point above when I mentioned the vacuum signal to pull open the BPV should always be after the throttle body in the intake plenum. Having the BPV in the compressor housing puts it closest to the source where any compressor stall would do the most damage and provide the most beneficial path of least resistance.

I guess I understand this concept. And I suppose this is less important than the wastegate.

Originally Posted by VitViper

That's pretty typical behavior with those turbos, they have a really crappy IWG canister design. I've done dozens upon dozens of cars with those turbos and it's always the same story. When we put an EWG housing on it and run an external gate... no problem, and then the turbo is decent.

I am one of those candidates, on both a 2rz and 2jz platform. I've bought a brand new expensive ass Turbonetics with an internal gate and after multiple times having to come off the dyno (at 2 different shops even) from from spike or drop in boost levels that were unmanageable. Then I picked up a used journal bearing Garrett, and a Tial 44, moved the Tial Q closer to the tb with a better ebc, and suddenly, everything worked like a charm. Not saying that's what's going on here exactly, there's far too many other things to go wrong and I'm guessing it's not the bpv.

[xkalelx]

Originally Posted by Kenneth

The yellow boost line looks good. A bit of overshoot on spool, followed by flat boost and then it tapers off most likely due to exhaust pressure being high, making it harder to keep the wastegate closed.
This is what I would expect to see on a car with small turbo(s) and a MBC.

If you can make it do that all the time, nothing is wrong and you need some boost control.

Blue looks to be wastegate pressure only and the other 2 could be due to EBC not being setup well.


If you want to diagnose problems, first do a boost pressure test to make sure the intake is holding pressure. IMO, its critical in a turbo system to ensure everything holds pressure, if there are any leaks you can waste countless hours trying to look for a problem which doesn't exist.

Next, bypass the EBC and connect the compressor outlet pressure directly to the wastegate.
It looks to be easily accessable from your picture so should be easy to do.
You should watch the wastegate actuator arm and ensure it is moving as expected during the dyno pull to verify that its working properly.

If this fixes your problem, your EBC could be connected incorrectly or faulty (or just programmed badly)

If not, you need to look at the pressure bypass valve to make sure it is correctly connected (as suggested above) to the engine side of the throttle body. This needs pressure to keep it closed, without this pressure feed the boost pressure will push it open, leaking the boost.
This means if it is either not connected, or connected badly with a hose which sometimes blocks/kinks you will not get good boost control.

Those are the most likely reasons for poor boost regulation.

If that doesn't get you where you want to go, you will need to provide more information. Namely data logs which will show AFR, timing, knock correction etc.

Yeah, I think that's what my tuner is currently struggling with is getting consistent boost at a given RPM. From the updates I have gotten, they haven't even started boost control with the EBCS until they pin the erratic boost behavior with just wastegate pressure alone. I sent them a brand new Turbosmart actuator and it didn't help. That's good advise though, thank you. Ill ask my tuner about bypassing the EBCS all together Monday and just hooking the boost reference directly to the WG. I know Monday morning he is going to tackle the recirculation valve and verify it is working correctly.

Originally Posted by VitViper

That's pretty typical behavior with those turbos, they have a really crappy IWG canister design. I've done dozens upon dozens of cars with those turbos and it's always the same story. When we put an EWG housing on it and run an external gate... no problem, and then the turbo is decent.

Hate to hear that! Ah! well... We can rule out the canister anyway as it has a aftermarket one now. I suppose its always an option to close the internal gate and weld on a Tial 38mm EWG if there are no other solutions.

Originally Posted by Toyarzee

I am one of those candidates, on both a 2rz and 2jz platform. I've bought a brand new expensive ass Turbonetics with an internal gate and after multiple times having to come off the dyno (at 2 different shops even) from from spike or drop in boost levels that were unmanageable. Then I picked up a used journal bearing Garrett, and a Tial 44, moved the Tial Q closer to the tb with a better ebc, and suddenly, everything worked like a charm. Not saying that's what's going on here exactly, there's far too many other things to go wrong and I'm guessing it's not the bpv.

Hope I dont have to go to those measures to get it run right, I am already pushing close to $10k on this build.

Thanks again for everyone's input and advise. Its greatly appreciated.

Sam

[Sportsguy83]

Your idle issues are because of that sharp angle right at the MAF sensor....

To really rule out the EBCS, you need to completely disconnect it from the system, and run a direct line of boost into the actuator. Th EBCS even if unpluggled will interfere with the boost signal unless completely bypassed from the system. Also, IWG systems are famous for boost tapering down at higher RPMs.

[xkalelx]

Originally Posted by Sportsguy83

Your idle issues are because of that sharp angle right at the MAF sensor....

To really rule out the EBCS, you need to completely disconnect it from the system, and run a direct line of boost into the actuator. Th EBCS even if unpluggled will interfere with the boost signal unless completely bypassed from the system. Also, IWG systems are famous for boost tapering down at higher RPMs.

Hard to tell from from the photo I posted, but my MAF is located behind the driver side headlight. Air filter is in the front bumper next to the washer bottle. The intake is fairly straight.

Damn. Well, Im glad you posted because I really dont have the experience to have known that.

From the updates the shop has given me, they worked out the idle issue. But the inconsistent boost engagement is what is slowing him down. Im hoping that boost control added after the fact will alleviate most of that boost droop at high RPM. Crossing my finders that the inconsistent boost in the dyno sheet I posted is direct result of a bad ECBS or recirc valve. Thanks for the input @Sportsguy83. I should have more data and information Monday. Hopefully a resolution and a well tuned car Because I'm still in a rental car.

Sam



@NahumCC Heres a shot of typical fitups.

[Sportsguy83]

Originally Posted by xkalelx

Hard to tell from from the photo I posted, but my MAF is located behind the driver side headlight. Air filter is in the front bumper next to the washer bottle. The intake is fairly straight.

I'm sorry, I thought it was below the pipe, right at that sharp angle before the throttle.


Good luck man, I hope it gets resolved rather easily.

[VitViper]

Your solution is right here:

https://www.treadstoneperformance.co...rbine+Housings

[xkalelx]

So, tried to collect the car today but it isnt done yet. Still not tuned on E85. Still has weird boost building issues. They pulled the recirculation valve and everything looked fine. They hooked the wastegate actuator up directly to the compressor cover outlet but it didnt modify the behavior. They are getting more boost off the wastgate now though so thats good. It is hitting the 10psi (wastegate spring pressure, no boost control) and tapering down to 8psi near redline. It is putting down 300whp on 93 so I cant complain.

I suspect I have a vacuum line issue. My recirculation valve is seeing vac/boost from a tee fitting on the the brake booster. Which also has a tee fitting off of that branch for the AEM Failsafe. Which all of those lines are from previous projects. I bet a vacuum block and new reinforced silicone hose would make the recirc valve more consistent. Thats an obvious one to look at, right?

Ill pick the car up kinda "as-is" for the time being. Ill have to schedule another day or two next month after I tinker around on it.

[VitViper]

That's just normal with those IWG housings -- they are junk. I have dozens upon dozens of datalogs from dozens of customers with these turbos, looking like this boost curve.



We've put an EWG housing on the same turbo, no problem. lol

[King Tut]

This is the reason I ultimately shyed away from a Full-Race kit on my S2000. Too much fear of having no way to properly control boost with the twin scroll IWG.

[ATL BRZ]

This makes me sad.

[xkalelx]

Originally Posted by ATL BRZ

This makes me sad.

You and me both. Being new to the world of FI. I thought the IWG EFR was the way to go since its an all-in-one packaage and thought I would actually save a bit of coin with less parts involved. wompwomp.

In all honesty, this isnt a race car, or a dyno queen. A few PSI off the top of the rev range isnt going to make much of a difference to me. I was able to walk a new M4 last month and thats all I need to be happy haha.

[cdrazic93]

Originally Posted by King Tut

This is the reason I ultimately shyed away from a Full-Race kit on my S2000. Too much fear of having no way to properly control boost with the twin scroll IWG.

Havent Checked that kit in a while, dont they offer an EWG option too?

Edit; just checked theyre all EWG lol

[cdrazic93]

Originally Posted by xkalelx

I was able to walk a new M4 last month and thats all I need to be happy haha.

If this doesnt show up in "come race me bro" then ill be sad.