Luis de Prat

Could you please elaborate? Thanks!

blown 944

sure here is the copy from Pelican.

One of the best MODS I have done
I was not going to do this b/c I was looking for a Tial w/g but I went ahead.

I made a dual port stock wastegate. I did it by tapping the bottom side of the diapham housing and installing a 1/8" pipe thread fitting with a 5/16" nipple.

I also used self tapping screws to seal the 4 holes.

I also used a 3/16" tall piece of copper tubing to seal between the diaphram housing and the valve housing.

I wasn't going to do it b/c with the turbo I'm using (T4 .58 ar p trim wheel (big) ) I figured the crossover pressure would be minimal. It was to an extent.

what I had before was that my MBC was set to 22 and would taper to 20 at redline.

I did the mod and went for a run with the MBC bleeding the same amount and it shot right to about 27. Needles to say that was a quick one. I am not looking for that kind of pressure yet .

I reset my MBC and now it is set to run up to 24 and holds 22 rock steady. It builds quicker too.

It wasn't as necessarry with my setup but anyone that is using a stock W/G even if it has some shims in it will definately benefit from doing this. Especially if you are using a K26 turbo or any small hotside turbo.

Just thought I'd share

Luis de Prat

Thanks. So, you're running a bigger turbo, MBC, larger injectors, etc.?

blown 944

Yes, yes ,no and probably no

I did a bit of explaining my setup in this thread: Just got done at the dyno.

Sorry, I'm not great at the copy and paste link stuff.

It is a bit unorthodox though so be prepared

toddk911

Did you notice a lot of difference in spool up with the running in dual port? ; with the big turbo and high boost.

blown 944

Yes when running bigger boost for sure. However if you take my crude way of adding fuel into consideration it would be hard to say exactly at what rpms.

What it did do though, was allow for more boost initially, then taper. IE now I run about 25 psi daily that tapers to about 23. I just drove it yesterday and went ahead and cranked the MBC a little more and it went to about 27 and was holding a good 25 to about 5800 then I let off.

What would have happened(using the shim and exhaust beedby) was that it would have (this is experience at 22 psi) built slower then started to fall off. It would go up pretty high, but it would fall very quickly. I imagine that if I were trying to run the boost I am now it would possibly get up there, but I am not sure I iwould most likely need to use a larger spring. I will say this, I have a much better control of the wastegate using this setup

If I were to run below 20 psi I don't think there would be a difference b/c I think the spring holds that pressure OK.

gt37vgt

good stuff guys I kind of set mine up for duel port but when bench testing found just heaps of shimming works fine the other thing i did to give me the warm fussyes was ported the inside of the housing a little back cut on the vavle and lapped the valve seat in with allen hey on power drill and lapping compound un believable people talk about flow then put a smaller 35mm tial thing on

blown 944

I suppose I could have mentioned the lapping .

Honestly though, how much and how have you been able to bench test it that way?

The reason I ask is b/c I have actually ran it with 3/8" tall nuts as shims (about the max) and still experienced rolloff.

Out of all three
1) max shimms
2) shimmed with spring and sealed
3) dual port sealed

the dual port is the only one that has allowed me to maintain over 22 psi at redline, all others bled off.

toddk911

My GURU (stock modified) was able to hold any boost I wanted to redline. The mods to your wg sound even byond that so I would have to say any roll off you are getting might not be the wastegate? Turbo, leaks at only high boosts, etc.

Also, do you think your mods to the stock for dp mode are better for spool up than just running a Tial in dp mode?

blown 944

I am wondering whether your compressor is just much bettter than mine( I am assuming it is) and you may not be seeing any rolloff, but the WG may be opening some. What turbo is that super 75, a to4e 50 trim? If you have a turbo that has good efficiency up there(this is what I am assuming) , the rolloff may not be as noticable because you have extra air that is still usable and even if the WG opens you are still going to hold boost to redline . I am working with a turbo that is pretty maxxed out in the upper rpms (changing this weekend) so it is very noticable if there is rolloff or not.

Edit: I did some research on your wheel ansd I am almost positive that is what is happenning with you setup. I would bet that if you changed it to a DP that you would have to immediately turn your MBC.


I guess the only way to really tell is to do a test using pressure in the wastegate runner. I tested the DP mod using 2 differnt pressures and it worked flawlessly.


I have done back to backs with all three types and like I said the DP is the only one that held.


I guess I should also mention that the rolloff was at above 6000rpm. Having watched a few cars with similiar turbos on I have noticed that the dropoff is pretty significant above that . It just drops once they hit 6000 rpm

No I don't think there would be any difference in either the Tial or factory modded DP. The price and quality of the items would be the only differnce IMO.

nize

supposedly, john milledge has been doing this for years.

i have also heard that even with this mod, the stock wastegate gets pushed open by the differential in the crossover pipe pressure because the valve has so much surface area, which is why people move to the tial wastegates.

toddk911

Cool. That is the info I was looking for. I guess I will have to try mine in dp mode. I would have from the start but a lot of people on here mentioned not much difference when going from single to dp mode. But maybe that was due to stock turbos, etc.

Do you have to pull the wg to get hoses re routed for dp mode or can one get their hands in there without breaking to many knuckles????

blown 944

Nize, you make a good point there. I wonder though, if that is _more_ due to most people using a t3 sized turbine vs a T4? That would be my assumption. Having experimented with a range of t4 turbine housings i can say the pressure differntial is very much changed going even from a .82 to a .96 (both huge) . While both are very large there is a differnce b/c I was able to get full boost withthe .82 at about 5800 whereas withthe .96 I wasn't able to even get over 22 psi no matter what. Both compared to what I have now .58 were almost useless on the street. My point is that these are ALL T4 and if compared to a t3 the pressure ratio would be even more dramatic.

Todd yes you will have to pull it for a couple of reasons.

1) you need to get a seal between the diapham housing and the valve housing (copper washers or tubing works)
2) you will need to drill the hole to tap the bottom of the diaphram housing and you would want to blow out any shavings .

Just remember when disassembling, to remove the fitting at the top and use an allen both on the valve and the diaphram (under the fitting at top).

Just use some pb blaster when starting. Makes life a lot easier.

special tool

One thing to remember about him is that he does not use terribly undersized turbine/housing combinations (advises T4, I believe), so the backpressure is not 3:1 or so like k26/6 and some aftermarket turbochargers made for the 951.