If you're just enbiggen the waste gate outlet then that's probably right. I'm not experienced so I took my time and I also tried smoothing the transition towards the outlet. I probably had an hour or more in the whole process.


Also, I'm installing my built motor this week so I'm hoping to have it tuned with this turbo maxed out on 93 and E85 in the next few weeks. I'll be able to post results we finished

 

Well gasket restrictions wasn’t going to work for me, I have a true dual exhaust, 1 coming off each turbo, and only 1 had a gasket.
Thought about trying to restrict the exit of each exhaust tip, but couldn’t get anything in there due to bends. So instead of contemplating getting exhaust work done (at the detriment to performance/sound) ive been busy tonight to get the easier of the turbos off.
Wastegate port measure 19.5 approx MM.

My factory T28 measured 24mm.

I think there’s only room to maybe go to 22-23mm at a push. Penny washer a lot smaller on this than the T28.

Doesnt feel like a huge difference, but I guess better than nothing.

 

I opened mine up to 23ish mm. It's more significant than you think. Something like 280 sq mm to 415 sq mm opening. That should solve most your issues.

 

fingers crossed you’re right, a significant area difference as you say actually.
i port matched a turbo maybe a decade ago, so thankfully found the old carbide bits, hopefully should do the job.
good thing about dismantling a new-ish turbo, had no problem what so ever pulling the exhaust housing off, just popped right off. I’m not used to this simplicity, ha.

 

Well I prob spent a couple of hours on each with a hand drill and carbide bits, but came out ok.
I only went to 22mm in the end, felt more comfortable at that size so still had a good seal, so 19.5ish to 22mm, is about a 25-30% increase in flow.
I port/gasket matched just the wastegate end and created a minor channel and lip over, I don’t think I took more than 0.5-1mm out of that to be honest.
Hopefully this is enough.

 

can I ask did you keep to the supplied 0.5bar Garrett actuator? Porting is making me consider switching back to this (as opposed to my forge units) if it can genuinely control 7-10psi or so with no boost controller in the equation and minimal creep. Before hand it was not as per my first post.
worth a try I guess, I assume other GBC owners kept to this actuator?

 

I did keep the 0.5 bar actuator. The car would creep to 8-9psi in 4th gear. Never really noticed any creep in gears lower than that. I think you probably removed enough material to get a handle on the creep.

 

Thanks all for the replies.
All back together, unfortunately the Garrett actuators still led to alot of boost creep. I feared my porting did nothing, but as per my previous comments, the actuator arm doesn’t move very much with these garretts, so swapped back in the forge actuators instead, and seems we have much improved the situation!!!!

Arm moves twice as far on my forge ones when I bench tested them below 1bar, so seems flapper opening more AND the porting has sorted my situation!!

On actuator pressure only, 0.5bar creeping to about 0.7bar with no boost controller in 4th (previous would creep over 1bar). Boost controller enabled, 0.8bar creeping to about 0.90-0.95bar.
I still need to have a play about with the controller I think as its not a target boost one, (I have a HKS EVC-S), but boost now appears to be behaving and feels real nice even with a small amount of creep. Not sure it’s ever going to go away unless I repack exhaust or drive in much warmer weather, but overall super pleased I don’t need to keep an eye on boost gauge so much anymore! Porting seems to have improved things.

Thanks all for your input……

 

Just a little update with these turbos. I finally got my built motor setup tuned and had great results.

VVT, 9:1 cr, 1.9L, Skunk2 intake manifold, 93 octane and 15psi

 

good looking power curves - what were the different levels as far as boost?

Thx

 

The 310whp line was warm engine wastegate pressure (7 psi creeping to 10 at redline). The 290 was wastegate with a heat soaked engine.

 

310whp at 10psi at redline?

 

Yessir. That's what the tuner told me.

 

In 93F heat to boot!!

That's amazing because it took me 18psi on a 6758 to barely crack 300, definitely on a more conservative dyno, but still. Every time you double atmosphere (about 14psi ~ 1.0 bar for simple math sake) you should almost double power, doing some quick math 10psi is about 70% of 14psi which should put your NA power somewhere around 220whp. I managed about 210whp on 12psi back in the day on my old T25 setup.

my math is often not right, but physics be physics. Either way, glad to see you got the overboost managed -- I actually really like rising boost curves with engine RPM so that rise from 7 to 10psi would be desirable to me. Looks like a ton of fun, I bet the boost comes on really fast with that turbo

 

I think we’ve switched to talking about a 2.5 liter in a noble m12, hence the 300hp at such low boost levels.

 

Are you running a catalytic converter in your exhaust? I've ported my GBC the same as y'all have, but boost creep is uncontrollable with my cat-less Kraken 3" kit

 

I don't think that's exactly right because different sizes turbos flow different volumes of air per psi. The volume of air at 10psi from a t25 is much different than 10psi from a 76mm.

I'm still talking about my 1.9L BP lol

No cat in my setup. Full 3". What is the diameter of your WG orifice currently? I also smoothed the transition to the office inside of turbine housing.

Have you checked to make sure your WG actuator is functioning correctly?

 

I ported mine to about 21mm from 19.5mm. Most of the work I did was cleaning the transition and creating a nice route for the exhaust pressure to flow out the wastegate. Actuator is functioning well, kicks right to 150kpa and hold until about 4500 when creep comes on fast.

 

I think I opened mine up closer to 24mm and that seemed to help a ton

 

Yea mine clearly still needs some porting. Wastegate wired open still creeps to my boost limit of 190kpa by 5600RPM lol