Boosting Problems After Installing Dump Pipe

[Birds]

Lastnight I installed a cheapo 3" split dump pipe and front pipe (after a great deal of trouble getting the old rusted through bolted off the old dump). Anyway, on the drive home, besides my turbo sounding louder when spooling (attributed this to the new stainless steel piping), I noticed it is now boosting to .6/.7 bar as opposed to the .5 it was at before. I thought this is probably just a side effect of freeing up space in the dump/front pipe as it's not unheard of to gain a pound or so worth of pressure after doing this modification. Thing is, it would boost fine to this in 1st and 2nd gear, but then in 3rd gear the turbo would start to spool but it would not create any boost...just lagged its way from 60km/h to 80km/h. It's almost as if the ECU was kicking in with a boost cut?

Now here's the prime suspect, and I want to ask this before I go pulling the dump pipe off cause it's an absolute shit to get off. As it is a split dump pipe there is a removable divider between the wastegate pipe and the dump pipe, which I noticed wasn't sitting completely straight after being tightened by me, almost overlapping a bit on one of the pipes...but not enough that I thought it would bother anything. See the picture below of this divider.

Is it possible this divider is jamming the wastegate shut, creating enough boost for the ECU to kick in and say that's enough? My car had no problems at all before installing this pipe...I can only attribute it to this?

Any ideas?

Cheers.

[zebra]

try un-hooking the wastegate actuator and moving the flap by hand, you will soon see if its getting jammed.

[whistle]

If i were you i would disconnect the wastegate actuator and see if you can move the little flap open and closed. If it wont move freely the gate is getting jammed.

[Birds]

Cheers guys, good idea...saves me pulling the dump off if that's not the problem (though in some way it has to be cause there's nothing else I've done to the engine).

[Birds]

Well the wastegate was getting jammed by the divider...

I removed the dump and installed it without the divider in place. Wastegate flap was now moving freely by hand so I reconnected the actuator. ECU didn't seem to be cutting in as bad as it was before but the thing is still overboosting and I feel some hesitation if it gets to .6 or .7 bar. I'm going to pull off the actuator this arvo when the engine is cool and see if the flap has gotten jammed up again. If it has I'm putting the stock dump back on, cause it's a pain in the ass having to use half throttle for the sake of making sure the thing only reaches .5 bar. Is this something that bypassing the ECU boost cut might fix? What pressure is the factory cut set at?

Why did I let slide on my number one automotive rule? You get what you pay for!

[R31Nismoid]

Without the divider you might find that the gasses are not mingling - this is not a good thing as its going to create some crazy turbulence on the exit.

[Birds]

Thing is, the standard dump pipe doesn't have this divider (although it doesn't have a split pipe either). And the same problem seems to be occuring with or without the divider, just to a lesser extent without it. Engine should be cold now...I'll go check the wastegate flap for interference.

[femno]

LOL you deserve everything you get for buying a EBAY item for your car.

Standard is better than 99% of the rubbish on the market, but you didnt need us to tell you that did you?

[Birds]

I deserve everything I get? I usually avoid sarcasm like the plague but that's a terrific contribution to a help wanted thread. I've bought plenty of items off eBay for my cars without issue. I avoid critically engineered items - it's not like I've gone and bought a copy turbo expecting total reliability. The assumption is that exhaust piping is a pretty safe bet, with the worst that can happen being wastegate issues or a shitty sound. Besides, the front pipe is/sounds fantastic and together with the dump pipe it cost half that of a Jap powerhouse branded front pipe...so I will have no regrets even if I resort back to the standard dump.

[chiksluvit]

I had the same dump pipe on my old R33 and it didnt have any problems

you could probably try grinding the divider down a bit and see if it will clear the wastegate

sounded like it wasn't completely jammed, like its probably just slightly in the way where the wastegate was touching it when its warmed up and expanded

[Birds]

I removed the divider though, and still have a couple of issues. Think I'm just gonna switch to the stock dump and see how that matches up with the front pipe. Not worth the hassle of wondering if there's something wrong with my car

I think you have a good point about it being warmed up and causing it, as I've noticed it doesn't give me any trouble when the car is cold. And I pulled off the actuator arm when cold...flap was opening very freely, no jams.

[Pal]

Had the same dump on my car for years, had a bit of cleaning up to do on it and re welded all the welds just to make sure no cracks would form. worked well on a standard turbo, got rid of it when i put a high flow on.

[**RB2530**]

Not likely too be an issue but you should also consider thermal expansion of the different components in that area.

Ie you would have to be unlucky, but it may be that when all is cold there is clearance and the flapper clears the divider but when engine is running and the flapper opens up it gets heated by the exhaust gas flowing past it and it expands to the point that it catches on the divider as it trys to close...Once again not likely to be that close but you never know...stranger things have happened

For this type of issue "die grinder is your best friend"...

[Coxie]

bought one of these dump pipes awhile ago and it blocked my wastegate from opening at all, boost would just climb up & up. Problem was resolved by grinding down the side of that divider and also cleaning up the wastegate pipe entry. Just poor quality control when theyre manufactured

[Birds]

Thanks guys, I'm gonna give that a shot. I'll just put the stock dump back on for now and while the aftermarket is off, give it a birthday with the old die grinder

It is indeed poor quality, I expected nothing more for so cheap...but like I said...you get what you pay for lol.

RB2530, I won't rule out your theory because the difference between the flap being able to open and shut was the difference in the position of the dump pipe on its mounting bolts. I quite literally held it in place and put the bolts on so it wouldn't move out of position to allow for free movement of the flap. So it's more than possible thermal expansion is responsible!

[TALBO]

Speak to Andrew at AM Performance, he'll build you a nice 3" stainless split dump/front pipe. He also makes 200 cell hi flow cats

I took this advice from the SA section of SAU and couldn't be happier with his products.

Andrew - 0401865373

[paulr33]

ive got a BATMBL split dump on my GTST, never had any issues

[TALBO]

ive got a BATMBL split dump on my GTST, never had any issues

I'm pretty sure that was also made by Andrew at AM Performance

[Birds]

Cheers! Do you know how much he charges for a 3 inch split? Doesn't have to be split I just want the extra room from a 3".

I tried putting the stock dump back on but then the rest of my exhaust system wouldn't bolt up straight. I'd need a flexijoint to do it. So I cracked the shits with it and took to the aftermarket dump with a die grinder...made plenty of clearance for the flap to swing past the bottom of the wastegate pipe freely, as this is what was making it sticky. So the flap is now moving freely.

But after reconnecting everything and driving again it still gives me trouble. I've now concluded that sticky wastegate flap isn't the problem, wastegate flap clearance is. It's not that the wastegate flap is getting stuck on something, it's just not opening to its full 90 degree potential. Basically, at mid-high rpm (and with full throttle) there is so much exhaust gas flow, that for the wastegate flap to relieve boost it needs to be able to open a full 90 degrees and no less. It's only getting about 70 degrees with the aftermarket dump. So it's the side of the wasegate pipe that needs to be ground down, not the bottom. Only problem with that is...there won't be much more metal left before I start breaching the welds on the pipe. Gonna keep grinding...just a shame my stock dump won't go back on because of the new system, so if I go too far I won't really be able to drive the car.

Sometimes I just want to leave these things to the pros lol.

[TALBO]

From memory the 3" stainless split dump front pipe (1 piece from turbo to cat) was around $360. Great quality and I have no boost spiking issues