so i have boost creep. the stock wastegate on my 89 turbo is not up to the job. I would be expensive and time consuming to buy an exhaust manifold with ext wastegate flange, waste gate, custom downpipe, turbo relocation, fluid lines etc.probably at least $777.

My main concern is not blowing up my engine. I am running low boost. id like to see what kind of power i make at just .8 bar. the car feels strong and if i provoke the throttle it sails way past that level. Is there any reason why a relief valve or pop off valve set to open at .8 bar and costing $130 from greddy not be completely adequate for my intentions? I have not seen this done often. I guess most people have more money and foresight and that the proper exhaust and wastegate would be ideal but why? i assume there must be some advantages because thats what everyone seems to use.
Is there any particular danger in going with the relief valve to limit boost creep/spike?
Thanks

 

I've never looked into relief or popoff valves on the intake side but if you don't have any money you can add restrictions to your intake and exhaust setup. Long piping, size changes, bends, smaller diameter piping, etc.

Or you can remove the turbo and port the wastegate. If you are getting boost spike though (way over preset level) you may want to check the reference line for your wastegate and the wastegate itself.

 

yeah i thought about choking it up, i have a supertrapp and it runs like **** when i put the caps on. i like how fast it is until i want it stop building boost. the lines are good. thanks

 

as far as porting the wastegate, i could be wrong but with the 89+ turbos there doesn't seem to be a lot of material i can remove. and that probably wouldn't help with the cracks

 

S5 wastegates can be opened up quite a bit. I took mine from the stock 18/25mm to 23/26mm. That's a 25% gain in area, and with it I have no boost creep, even with a fully open 2.5"+ exhaust.

It's free as long as you have a die grinder and carbide burr, and it doesn't take that long to unbolt the turbo / port / reassemble.

 

I had a big street port and an s5 wastegate ported to the edge of the flapper and it still creeped like hell. in cold weather it hit 18psi sometimes. This was with a straight through 2.5" exhaust. I eventually gave up and went with an external wastegate setup and aftermarket manifold etc.

 

you must remove more material than just the holes under the flapper...

i had ported mine last year, and only made the holes bigger.
only in 5th, it creeped up to 0.9bar instead of 0.5. this with full RB 3" exhaust.
i have now opened up the turbine housing once again and ported the **** out of it. there is A LOT of material that can be removed, especially on the smaller inner port. dont go beyond the edges of the flapper, but take the grinder much deeper and also work your way in from the manifold flange.

haven't tested this yet, but i bet that should do the trick for ya

 

and if its still not big enough you can use a washer to make the flapper bigger. just weld it on. there is a write up on here somewhere on procedure but its a pretty simple task

 

that writeup is for a S4 turbocharger...

 

the pop off valve would be a bad idea because the turbo is still spinning at rediculous speeds (it's still producing 15+ psi) and it'll blow your turbo pretty quick. Also the air will also be ridiculously hot because it was compressed so much by an inefficient compressor housing at those boost pressures... so yeah, porting the waste gate is definitely the way to go.

I had mine ported while it was at BNR being built into a stage 2 hybrid. I was easily boosting past 20 psi before (by accident) (3" RB exhaust and a 3" intake with no AFM), now the max I've been able to hit is 11 psi, which I'm totally fine with, once I get it tuned a little better and get my staging issues worked out I'll be aiming for 15 psi anyway.

you can definitely port the S5 wastegate to handle most setups.

 

true but its the same idea. application will benefit the same way and to be honest, i dont think it even requires a write up. wastegates are easy to grasp and the op knows that the restrictive wg is the reason for boost creep.

 

I think arghx has a write-up on porting the S5 wastegate, it was done by his machinist. The finished product was probably a 60mm+ combined wastegate diameter with a lot of back-cutting.

 

With the stock management a pop off valve will not work. It is releasing air after it has already gone through the MAF. This would cause you to run stupid rich.

 

yeah, and makes you shoot 6 foot flames!

 

I'm going to be welding the stock wastegate closed on a S5 turbo and running a cheap external WG on the stock S5 manifold on my 6 port turbo project.

 

well off comes the turbo then. looks like the die grinder will be getting a workout. thanks for all the advice esp. regarding why the relief valve wouldn't work, though with my ap power fc i don't think the ems would be an issue since no afm.

 

Yes if you are running a power FC than you can use a pop off valve since the PFC uses a speed/density VE table.