S4 wastegate porting
 

Hi all finally getting around to porting my wastegate and was woundering if a grade 8 washer will be strong enough?

I'd say it should be fine.

Even better would be to go to a junkyard or small garage and see if they have any old broken exhaust valves. Grind that down and weld it on to the flapper. That's if you can find one.

So no matter how you port it you'll need a new flapper?

I'll be porting my wastegate once my engines out.

Rotary >Pistons

For small-mild ports you won't need a new flapper, but you must verify that there is enough overlap to seal. Most guys porting for higher boost inherently need a new flapper door due to the larger port required for their application.

I'm going to eventually Max out the stock turbo at 12 psi, I'm guessing that means I need to port it as much as I can.

Rotary >Pistons

Yes. The bigger... the better. When the turbo is already out and you have the opportunity to port the shit out of it, why not?

Here's some motivation:

(These images have been used for reference purposes from Aaron Cake's Homepage and BNR Supercars)

http://aaroncake.net/RX-7/s4wastegate3.jpg
http://aaroncake.net/RX-7/s4wastegate4.jpg
http://aaroncake.net/RX-7/s4wastegate5.jpg
http://gonzaloherrero.com/bnr/images...egateport1.JPG

If you only port out to the size of the stock flapper, then you don't have to expand it.

But that only permits you to port maybe the size of your index finger.

IF you want to actually do an all-out port job to the max size allowed by the turbine housing, you'll have to weld on a larger flapper cover. Then you can make the WG about the size of your thumb, which should flow about twice as much as the first version.

Here's some pics of the last WG I ported, series 4.

Stock:

http://www.rotaryresurrection.com/bu...n/DSCF8313.jpg
http://www.rotaryresurrection.com/bu...n/DSCF8314.jpg
http://www.rotaryresurrection.com/bu...n/DSCF8315.jpg


After porting:

http://www.rotaryresurrection.com/bu...n/DSCF8316.jpg
http://www.rotaryresurrection.com/bu...n/DSCF8317.jpg
http://www.rotaryresurrection.com/bu...n/DSCF8318.jpg
http://www.rotaryresurrection.com/bu...n/DSCF8319.jpg

As you can see I've gone from about 14mm in stock form to about 24mm which is pretty much the limit of the turbine housing casting itself. It's hard to tell but I've made an angled "backcut" to angle the wastegate hole in the direction of incoming exhaust air, so it only has to make maybe an 80 degree turn instead of a full 90 degree turn. That's why the port looks...uneven. I also cut a little relief into the turbine back plate and back of the flapper door to allow a little more opening angle for the gate...with the back plate installed in stock form the flapper can only open maybe 1/4 of an inch.

You can see above that there's a LOT of extra room left that the stock flapper covers, and you can just port the WG hole out to the size of the flapper (minus about 1mm all the way around) which will be an improvement over the way it's made stock.

I think I am about halfway .

Your port is looking decent so far, but don't waste your time with a washer. I've done it, other guys have done it, only to have them melt away. It may last longer if it's grade 8, but I wouldn't chance it for all the trouble it is to replace it again. Go to a local machine shop and ask if they'd give or sell you one or two old exhaust valves. They frequently have bent valves come in that can't be reused so you're likely to get them cheap or free. They're often stainless, but can be welded on with standard rod and they hold up to the abuse MUCH better.

Thanks for the info.

In the meantime, you could source a series five turbo, port the two wastegate passages and reap the benefits of the divided manifold.

...and have 250-300 extra bucks in a same-sized stock turbo that will make only slightly more power than the one you have now.

I'm broke and can't afford a new setup. It already boosts hard just creeped really bad.

well S5 has a better wastegate, and its a divided manifold, so it spools faster and controls boost quicker.

you are right that power is going to be the same though

I found one in the for sale section for $140 shipped

Rotary >Pistons