apexFD

Ok, so i need to port my wastegate. I was planning a huge elaborate CNC machine and new flapper door porting job... But this might just be a waste of time.

Here are my related mods.

-Full 3" turbo back
-HKS 3" intake
-Deleted emmissions
-HKS SSQV BOV

How big do i really need to port the wastegate in order not to get any boost creep with my above mods. I dont want to waste my time and money on something that is totally useless. Also if you could post detailed answers with a few measurments or pictures that would be absolutly exellent.

Cheers, Ben

arghx

iTrader: (3)

go to town on that wastegate. I've got a smaller wastegate port and it still hits 12+ psi when cold out, at least in 3rd gear...

Wankel7

Yeah, but if you go to big and the hole is bigger than the flapper it will kill off the line power.

James

arghx

iTrader: (3)

well do it right of course... put in a new flapper

Dom_C

just do more of a good flowing port job on it. Keep the stock flapper, and back cut the **** out of the backside of the hole. Also cut back the secotion of cast taht is right next the the flapper and exhaust turbine. I can't describe it too well without a pic but it is just a small wall part that can be ground back quit a bit to make more of a direct path for the exhaust going to the wastegate.

Aaron Cake

iTrader: (1)

http://www.aaroncake.net/rx-7/s4wastegate.htm

apexFD

I have a series 5, i would just like to see pictures and a bit of info on some s5 port jobs that dont boost creep with the same mods i have.

13b4me

35mm should keep you about a solid 9psi with your mods.

apexFD

35mm diameter...?? is that on both holes?

13b4me

Actually I overlooked the fact that you're S5. Never actually ported a S5 wastegate so I wouldn't know. lol

NZConvertible

There's no need to mess with the S5 flapper door nor use some elaborate CNC porting method. The S5 wastegate is a lot bigger than the S4's and there's not as much scope for improvement. Byt you can still easily enlarge both holes with a die grinder, particularly the short passage which can also be shaped internally for better flow. Becasue the flapper gets in the way ou really need a long-shank cutter to do it properly, as show here:

http://fc3spro.com/TECH/HOWTO/KWG/kwg.html

BTW< is every post where you ask for help the first thing you need to tell us is what year your car is, otherwise you get the wrong info provided like you did here, which just wastes everyone's time.

Nismo Convert86

iTrader: (7)

Also, remove material on the backing plate of the turbo till the WG door no longer hits it, did this on my car, and it helped limit boost creep almost as much as the ported WG alone; just buy allowing it to open more.

NZConvertible

That's a myth. The flap barely moves any further (~1mm) when you modify the backplate because the spring in the wastegate actuator already fully compressed.

Nismo Convert86

iTrader: (7)

I'm not sure about that, then I took the turbo off, there was a clear mark in the carbon on the backing plate because I didn't remove enough material. I would take the backing plate off and show you, but it's -6 outside, and snowing. I can see why you are saying this however, it's not like it can compress anymore, I'll have too look into this more, wheres my spare turbo...

Nismo Convert86

iTrader: (7)

Here are the pics, the first one you can clearly see the door wanting to go further, and leaving a dent in the plate. In the second one you will see as I pull on the actuator rod the WG door goes past the flat surfaces by about .250", meaning the spring has more travel then what it would seem, and taking some material from the backing plate should work.

NZConvertible

Put a pressure source on the wastegate actuator to open the flap, and you'll see it barely moves above the level where the backplate sits. Like I said, it's ~1mm higher, not enough to make any worthwhile improvement to flow. I've done this on my own S5 turbo.

Nismo Convert86

iTrader: (7)

I think I know what you are saying (I'm applying more force with my hand on the actuator rod than the air pressure can), and on my own I have seen the marks on the modded one. I still believe it works, that alone on the non-ported housing I have wouldn't creep anywhere near the non-modded maybe to 11psi, and non-port WG/non-modded plate (13-14psi). 11psi is still fairly safe on the stock fuel system.

I will see how the modded plate, and the ported WG work this summer. I'm in no way saying do this instead of porting, but while you have the turbo apart why not do it? It takes 10 minutes. Just an other safe-guard/redundancy.

NZConvertible

Unless you can explain how opening the plate such a tiny amount further could make that much difference, I'd say there must've been be other factors involved. I don't believe it could make any worthwhile difference.

If you want to mod the backplate, do something like this instead...

sub9lulu

iTrader: (7)

bigger the better

ShadowX

Just get an HK$ 60mm external...never worry about it again. >

Nismo Convert86

iTrader: (7)

I honestly think it's opening more that the "~1mm" that you said (I don't see any proof from you that this is in fact true either), if you grab the actuator rod it moves more than you think, if it didn't move more than that, why am I seeing these marks on both of the backing plates? Honestly I don't care because the stock turbo isn't something I'm going to stick with, and external is like 1000 times better.

apexFD

Ya, thats a good point about the rear plate, might as well do it if its out... Even if it doesnt do anything at least you made your car lighter by 1-2 grams .

So with a porting job like the one on this site.. i should see NO boost creep??

http://fc3spro.com/TECH/HOWTO/KWG/kwg.html

The whole porting procedure is very strait forward, just want to get it right the first time.

NZConvertible

My S5 turbo is away having a bigger compressor wheel fitted, so I can't take a photo of it, but I checked this for myself specifically because lots of people said the backplate prevented the flap from opening as far as it could. But when I applied compressed air to the actuator with the turbo fully assembled except for the backplate, the tip of the flap (which normally does just hit the backplate) barely protruded any higher that the plane of the backplate. Obviously the further open the flap is, the less effect it has on flow, so with the flap that far open, opening it a tiny amount further is going to make virtually no difference.

Nothing's ever garanteed as there are other variables that effect boost. But porting the wastegate will alsways result in less boost, and it's much better to port the wastegste and use a boost controller to raise boost afterwards if needed than to use flow restrictions to get boost down to a safe level.

Nismo Convert86

iTrader: (7)

Well we just proved that gouging the backing plate DOES make a difference, my car would not boost past 7psi, BDC was there tuning my car, and he agreed that this a worth while "mod", there were also about 7 other witnesses.

freemanrx7

https://www.rx7club.com/2nd-generation-specific-1986-1992-17/twin-scroll-removal-746913/page2/


The stock flapper door is fine.

You can also round the flat corner edges to make the air flow smoother. You can also do this to the manifold. (not shown in pic)