Overboosting!

[3LGODZILA]

ok so i recently installed a basic highflow turbo from hypergear and a split dump/front pipe from JJR. i made sure i die grinded out the wastegate section on the dump so it can open fully. also im not running any boost controller its straight off the actuator

dramas.........

so the cars running fine except the boost is creeping. boost builds up to 9-10psi as normal and stays there for about a second then creeps fairly quickly to about 17-18psi then i back off (may creep further but i dont wna try) and the weird thing is its not hitting R&R or boost cut im running standard ecu atm.

so ive blown compressed air into the actuator and the wastegate arm only moves half of what its supposed to (around 45degrees) which made me think its the split dump. so i took off the little circlip and took the actuator arm off the wastegate flap and moved the flap with my fingers and it moves the full way (around 90degrees)

what other tests can i do? does the actuator sound like its stuffed? can it be modified?

i am getting a nistune as soon as this prob is fixed

[kwickr33]

Check to make sure its getting direct boost source.

If they've modified your stock wastegate actuator braket then all you need to do is losen up 2x screws that is holding it and play with the fitting angle

I got mine setting on 12psi without controller, and the max my stock actuator could hold was 16psi.

[3LGODZILA]

stao from hypergear rang me today after reading this thread so +1 on hypergears service.

im gonna try drive with the actuator arm disconnected to see if the exhaust is a restriction and then i might try play with the actuator. when the engine cools down ofcorse

[3LGODZILA]

with the arm disconnected it boosted to 14psi. im guessing it is the exhaust then, not fouling but restricting flow

if i plan on running say 15psi would this be a problem or would the engine build higher boost in say a higher gear under load? i did the test in second gear and pretty much took it to redline

[hypergear]

Had a read at your previouse post. We believe boost creep is caused by your dump pipe:

[gotRICE?]

^ This

[GTScotT]

that sounds like a reasonable theory by stao.

on a stock turbo its probably not as much of an issue and ive seen people struggle to run under 1 bar with that type of exhaust before anyhow, so hiflow and your boost issues seems reasonable.

get a bell mouth dump

[Adriano]

Has it got a larger wasteagte flap, ported?

[hypergear]

We didn't install a larger flap its not needed. But we did port it out to about 26mms from 24mms. This is to all high flowed units, It have worked well, I have not had any one had boost control issues with it yet.

Go big isn’t always better, Bad point with larger disc and massive wastegate port:

You need to know the force exerted onto the actuator is: Pressure x Area.

If we use a 32mm disc and port that out to 30mm. Then we will have a massive boost drop towards red line. Most of use have seen this happening with internally gated GT30 units and high flowed units. Boost clam to 18psi in 4000RPM then drops back to 15psi by 7000RPM.

With this small .58 size housing running 30mm port we will definitely have issues holding boost up top. And don't think "big can" actuator helps, I've tried it, it does not work.

In our ATR43 G3 and G4 units which requires a massive 30mm internal waste gates to avoid boost spike and still be able to run flat 20~24psi, we’ve come up with this unconventional method:

to deliberately create a controlled boost spike, so we won’t have boost drop and power lose up top.

[Kinks]

Had a read at your previouse post. We believe boost creep is caused by your dump pipe

Yup. I've heard many reports of boost creep on split dumps. Mostly JJR ones, as it happens, but I'm sure there are others. It is utterly pointless trying to bandaid the situation with bigger wastegate flaps when your gate isn't opening past half way!!

A split dump has to be engineered VERY well to work properly, and while it's a nice idea the risk of your wastegate fouling on the dump does not appeal to me one bit.

I went for a JJR bellmouth dump and was well impressed by the build quality, neat TIG'd welds etc which is amazing for a chinese exhaust. The $400 metal cat was so messy it must have been stick welded to the flanges, at least the inside was clean. 180rwkw on stock boost.

Plus, think of it this way.. a split dump may get you slightly more performance at WOT, if the hype is to be believed. However a bellmouth dump gives you a big open pipe (there is WAY more pipe area for gases than a split dump!) and you get that whole area, LESS RESTRICTION, all the time. So your part throttle fuel economy should be better. It's just better all round, I'm going to stick my neck out and say split dumps are a dumb idea unless you've got a lot of money to spend doing it properly.

[240zrb]

I bought an JJR split pipe a couple of years ago, and had to modify it to fit my 240z / rb25det kombo. When I cut the pipe just after the bottom bend, I discovered the where the smaller pipe merges with the bigger, there were just a square hole. And that opening was a fair bit smaller than the small pipe. Used a Dremel, and fixed it. But could this be the source for all problems people are getting with boostcreep with the JJR split pipe?