Serious S4 wastegate porting…
 

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.

https://www.rx7club.com/attachment.p...chmentid=71970

https://www.rx7club.com/attachment.p...chmentid=71971

https://www.rx7club.com/attachment.p...chmentid=71972

https://www.rx7club.com/attachment.p...chmentid=71973

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.

https://www.rx7club.com/attachment.p...chmentid=71974

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 :D

I especially like your divided dp

Now that's a port! (In as heavy a NZ accent I can muster)
 

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

Scott

Maybe because it is professional :p:

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. :p:


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

https://img22.photobucket.com/albums...4-07-05/02.jpg

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... :bigthumb: