I have an 89 motor but an s4 turbo (long story). The turbo is rebuilt and works great. The car has the full 3inch RB exhaust, intake, walbro, chipped ecu (need to update for cheap..., ideas?). The motor has 11k and its an Atkins. With the wastegate set at 5.5 psi, the car creaps to 13psi. No detonation and it still runs pretty rich at this level (using "ball park" afr meter) but I would much rather have it spool immediately to 10psi and stay there. I am getting tired of never shifting past 4.5K to avoid going over 10. How large should I make the wastegate hole? Or should I buy a used (!?) S5 turbo and manifold? I have to pay to have the new flap welded anyways.

Any advice is greatly appreciated, within reason.

 

FC3spro.com has a writeup on this

 

port the wastegate to ~1mm smaller radius than the flapper door is then flare the port out larger as it goes into the exhaust runner, this should bring the boost level back closer to stock levels then you can set the boost level you want with a boost controller.

 

So the stock flap can handle it?

 

By the way, is 10psi a good target?

 

your upper limit is about 14 psi.

 

its not to bad to port these. it took me a day wiht a dremel. there much better ways though. i welded a washer onto the flapper and if you do the same its cheap.

 

How big of a hole and how effective was it?

 

There's an article in the archives that covers it in detail. Generally you port the orifice much larger then the flapper the weld on a new one. Mine is about 35MM, and I welded a large washer onto the stock flapper.

 

If you don't have a welder (or don't have access to one) don't worry. Like Karack said, you can get away with simply porting out the existing WG to about the same diameter of the door that covers it. For a stock turbo (even maxed out) this will do a fine job in controlling the boost.

Interesting side-note for the original poster: When the WG was stock, I could barely get the tip of my pinky-finger in the hole. When it was ported out, I could rotate my thumb in it.

If you've never removed the turbo or done the WG porting, this will likely be a 'day' project. No big deal for a VERY important safety "mod".

 

Why are people changing flaps on stock turbos for super large wastegates? Is it to shoot tennis ***** out the engine? I would like to just keep the flap but I am worried because of sooo much creap (8psi worth). What are you running with the stock flap?

This is the fourth time I've had the turbo off. Busted shaft, busted oil seal, etc.. I didn't port it last time because I am a dumb ***. I don't mind anyways, gets me out of the house in the winter and I miss the car when trashing my B16 civic.

 

on fc3spro.com lke stated above has a complete write up on it i just ported my s5 turbo's WG and that was my biggest project so far i thought it was easy just time consuming i ported it until the flapper door just covers the hole i havent had any boost creep at all and you shouldn't go above 13-14 PSI 15 is the max i would go because all it is doing is creating hot air

 

Plenty of people have posted about only porting to the edge of the stock flap and still having uncontrollable boost.

Not sure what your point is there but whatever... If you want to be able to run a full 3" exhaust, TID mod, pod filter, engine porting, etc then you need a bigger port than the stock flap will allow.

 

ok..... the metal for the flapper door needs to be specific, welding a washer on without knowing it's material is not advisable because the washer will deteriorate under the harsh conditions. porting the wastegate properly it can hold just about what you can toss at it with even the stock flapper door.

this is coming from experience not guesses.

 

My cheap mild steel washer seems to be doing fine after more than a year...

Coming from your experince with what? Full exhaust (3", no cat), full intake and a healthy turbo? It's been proven that with these mods a port under the stock flap is insufficent. If this worked for you then there must've been restriction in the intake and/or exhaust or a turbo problem.

 

Because the stock wastegate is pathetically small, even if you port it to the maximum size the stock flapper allows you to. The S4 is VERY prone to boost creep, and with a wide open exhaust and intake you NEED to radically increase the size fo the wastegate.

Going on more then a year now. No problems. Not my car, but a friends that we did in the same way.

 

I noticed you mentioned s4 specifically there. Is the s5 wastegate ported (keeping stock flapper), more efficient than the s4? I'm just curious, because I'm about to get my wastegate ported. I'd much rather not have to have anything welded if it's not necessary. I will have RB street ported motor, true CAI, and full 3" RB exhaust. Can a ported s5 wastegate with stock flapper keep it to 10-11 psi?

 

Yes, S5 wastegate is much better. Generally, only minor porting to the size of the flapper is enough. You shouldn't have too many problems keeping it to 10-11 PSI, but you have have to bypass that twitchy stock boost solenoid. I'd still suggest increasing flapper size though since you can always turn boost up, but never down.

 

12psi is the most I'll run on this setup and most likely I'm just going to stick with 10psi...btw...this is an s4 car/motor, with s5 turbo

 

I'd like to try to keep the flap but I would much rather do this job once. Even if I will probably take the turbo off again in another 3K anyways. Just one summer of not feathering the throttle would be fantastic.

 

even if u dont have the full 3in and jsut the downpipe it wouldnt hurt to port the wastegate right? how does that effect the twinscroll system? and what exactly makes that sound is it the wastegate flapper? this weekend im doing TB mod, porting polishing, and porting wastegate and welding the new flapper(washer) i have a stock FC stock TID BUT a RB downpipe and no cat stock exhuast...so i mean will there be any adverse effects...my car hits fuelcut with this setup spikes to 6 and hits fuelcut so i never give it that much gas...thanks!

 

You can't really over-port the wastegate unless you remove so much material that you actually weaken the turbo.

 

I just thought I'd throw in my two cents. I agree w/ NZ, I have a s4 with 3" intake and exhaust and still get about 3 psi of creep in fourth gear, even though my WG is ported to 34mm! If you are going to keep your S4 turbo you should seriously consider getting a bigger flapper welded on. I did the porting on mine with a die grinder and then I had a steel washer welded on for $25. I'd say that the three hours of labor and $25 is not very much to pay to keep your engine from popping from boost creep. Wouldn't you agree?

 

What do you have max. boost 'set' to?

I guess it differs from person to person/car to car. I never got any creep on my stock turbo and ported (to the door-edge) WG.

 

It would never hurt to pull the turbo and port the WG. Unless you suck and ruin something. Porting the WG won't effect the twin-scroll system either.

What "sound" are you referring to?

Even with the WG porting, with your setup it's still important to get an FCD just in case. They can be had for $50 easily.