After putting it off for far too long, I have finally ported my wastegate. I've been hitting fuel cut if I use full throttle in anything other than 1st gear, and don't want to fit a FCD while I still have a completely stock fuel system. Instead I wanted to keep boost down to ~8psi until I can get my hands on a FD fuel pump. Because of current and planned mods, simply porting to the edges of the stock flap was never going to be enough to keep boost down where I want it.

I recently had a chance to get the turbo off for a few days, so it received some serious wastegate mods. I wanted it ported well past the edges of the stock 20mm diameter flap, so a bigger flap was going to be needed. I decided to have a large washer welded to the bottom of the stock flap. I found a 34mm diameter washer at work that would be suitable. The port was also going to end up past the edge of the raised section that the stock flap sits on, plus the bigger flap was going to hit the inside edges of the housing. I fixed both of these problems by giving the housing to a precision engineering company who used a milling machine to enlarge the area the flap sits in and also provide a smooth, flat surface for the flap to seal tightly to. They then used a 28mm cutter to open up the wastegate port. This is about the same size as the ported wastegate on a BNR Stage III turbo, and is more than three times bigger than the stock 15mm port. This machining cost NZ$75 (~US$50) and I had the housing back on the same day. The washer was then TIG-welded to the flap by a workmate. To further improve flow I used an air-powered die grinder to extensively back-cut the port. This gives the port entrance a shape similar to a bellmouth, making it easier for gases to enter the port.

Here's my modded housing compared to a stock one. You can see how much bigger the port is and how much material around the wastegate needed to be removed to clear swing of the bigger flap.









I also have a custom divided downpipe consisting of a 2.5" main pipe and a 1.75" wastegate pipe. The purpose of this is to further reduce wastegate flow restriction and also to reduce turbulence at the turbine exit. Here's a pic of the downpipe complete with a brand new oxygen sensor I fitted while the downpipe was off. It looks a bit rough on the outside, but it's much smoother on the inside where it counts. It has an internal divider to keep the turbine and wastegate flows completely separate until the pipes merge. Another advantage of this design is that it allows the wastegate flap to open further, although I doubt this does much.



Boost is now a solid 5psi at WOT in 4th gear. It actually now feels a bit faster at full-throttle than it did when feathering the throttle at 8psi to avoid fuel cut, so I'm pretty pleased. I have a 3" stainless steel mandrel bend in the garage waiting to be turned into a TID, which should see boost rise another 1-2psi. The wastegate porting is so effective I might remake the downpipe with a 3" main pipe to match up to my existing 3" cat-back, since the 2.5" pipe was only used to limit creep.

 

Very nice, and very cool

I especially like your divided dp

 

Nice work on porting that turbo--looks professional to me.

Scott

 

Maybe because it is professional

 

Jeez I thought there'd be more interest in a successful solution to the S4's biggest problem. Maybe I should've put "supercharger" in the title...

 

supercharger turbo na 6port port wastegate

There, that should about gaurantee it shows up in 99.99999% of searches on this forum.

 

Correction:

stickers clear tails altezzas altezas tii hood S5 conversion V8


Now it will.


Nice work Jason looks pretty good in size.

 

You are now the "flowmiester"

 

Schweet!

I'm sure you will love how it pulls better on the top end once you do that TID mod as well.

I hope you can do many flow mods now w/ out having to worry about the creep.

 

On another note, damn it's weird seeing how little space there is with the steering on that side!

 

Yeah, I did the same thing to my Cosmo and couldn't believe the difference such a simple mod made. Easily the best hp/$ mod for FC Turbos.

That's the plan.

 

Looks very nice. The washer looks to be a better idea than ealier attempts using a valve. With a wastegate that large, do you think a TID would actually increase boost?

Regarding your DP, do you think you get an appreciable improvement?

 

almost as good as mine :P



40MM...and the son of a bitch still crept! Albeit only 1psi in 4th gear!

 

Good point. I'm going to say yes, simply because when I did the TID on the Cosmo, I got 1psi more boost despite the stock 12AT wastegate port being nearly only slightly smaller than my modded one. A also got a very noticable boost in performance. We'll soon see I guess...

It's hard to tell, but I know it's a lot better than the stock arrangement. I couldn't really do back-to-back testing, but the basic design is a long-proven one. I was having a custom DP made anyway, so I just took advantage of the opportunity to do something that not only improves wastegate flow but also to reduces backpressure at the turbine. Every little bit helps.

Damn Ryan, that's a huge port. I'm jealous...

 

The thread I had my pics attached to got deleted, so here they are again.

 

Here's mine.

 

how many people have broken the two smaller bolts that hold the WG cover clean off? i did, drove me nuts.

 

Does that flapper still alow some movement for better sealing?

 

Yep, the washer was welded directly to the stock flap, so it still has the same freedom of movement as before.

 

so does this make hp........ if i have a good fuel syst. would this make or kill boost ?????

 

I would do a general internet search on how turbos work for starters.

James

 

neither
if anything
kill (lower) boost because you cant creep?

 

Assuming your turbo car has been modified with exhaust and intake your boost will rise above stock levels. Mainly because of the lack of restriction.

It will rise so high that the stock fuel system will not be able to provide enough fuel to cool down the combustion and the car will run lean and then detonate. Not good.

So, what can you do to control the boost? Well, maybe you could get a boost controller. Well, the problem with that is the controller can only raise boost. Let me explain.

The wastegate is a simple device. It just is a hole that lets exhaust BYPASS the turbine wheel. The turbine wheel drives the compressor and that makes boost. So, if the turbine slows down because exhaust isn't going thru it you have less boost.

In a stock car the wastegate hole is small. So, by making this hole larger more exhaust can bypass. What operates the wastegate? A wastegate actuator (diaphram). You have a hose that goes from the compressor to the actuator. At a certain PSI of boost the actuator will open the wastegate fully bypassing exhaust.

So, here you are with your modded intake and exhaust and uncontrollable boost. Lets say it is spiking past 16 psi. Not good. So, you put your boost controller on and lower it all the way for low boost. But guess what happens? NOTHING , your boost is still spiking 16psi! Why? Because the wastegate is FULL open and it is still not bypassing enough exhaust for a lower boost.

So, you take your turbo off and do what NZ did. You make it bigger and put a bigger flapper on it. NOW you put your boost controller on and set it to the lowest setting and guess what? Now you are building maybe 6psi MAX. Now , from this point you can take the controller and raise the boost to where you want it! You have controllability.

And that is what this mod is about; controlability. That's it. Why do you want that? Maybe you can't run past a certain boost because you have the TMIC, or maybe your fuel system isn't enough for that boost, maybe you cant afford premium gas. What ever the reason.

How does the boost controller work? Simple it sits in the middle of the hose that comes from the compressor to the wastegate actuator. It acts as a bleed valve. Lets say 10psi of boost comes from the compressor. Then the boost controller senses that and bleeds off that boost so the wastegate actuator doesn't open all the way. Then lets say the compressor is building 15psi. Now the boost controler is overwhelmed and sends that full signal (boost pressure) to the wastegate. The wastegate opens fully and is hopefully holding your set boost.

James

 

Ive been looking to make this mod myself. Got rid of all the emission stuff, did a TB mod (removed the one secondary butterfly valve) and got 2.5" exhaust all the way. This makes the boost spike up to 16psi!! And i got all the stock IC stuff (tmic etc).
16psi cant be good... How big should i make the wg? I got a dremel so the work it self should go fine.
I also wounder what kind of boost i should run on. Again i got stock Tmic, 550cc primary 720cc secondary, walbro, Microtech LT8, 2.5" dobble exhaust, open airfilter(low resistance).
The engine core itself is stock with 75 000km on it.

BTW whats the TID mod?

Thanks
Sindre

 

Err, you have a Microtech LT8, yet..stock TMIC?

First of all, the stock turbo should never see higher then 12 psi. Higher, you are blowing hot air, and greatly reducing the life you're turbo. The TMIC is also horribly inefficient past 11-12..so..

And a dremel will not cut this job. First of all, it would take hours of jamming it against the sidewalls of the port. Second, with open-air mods, the stock flapper on the wastegate is NOT big enough to stop boost creep. You need to have a new washer welded on, one big enough to happily cover a 35-45mm port. TIG weld at an exhaust shop, woot!

While their, they probably have an air die grinder. Have them trim the port to 40mm, weld on the new flapper, and call it a day...




The TID mod = You take off the stock, cracked plastic TID, which has like two or three (can't remember) 90* turns.. and you put on a 3" straight pipe! BUT, the stock turbo has a 2.5" inlet. So, you reduce the 3" to 2.5" just before getting to the turbo.