I would guess that your k24's came with springs that are able to hold more boost. My stock X50 wastegate springs are holding 1.1-1.2 bar reliably after the ecu flash.

I upgraded the DV's, and clutch at about the same time, but haven't done wastegates yet. The stock clutch was the weakest link for me.

 

My wastegates were stock... I was hitting 1.2 bar... And I have K16/24s. I went the UMW spring route and modified my OEM wastegates and have snaped zero rods...
So that answers #1 and #2... The thing you need to be worried about is if the stock spring is being overcome at near 1.2 bar and how much is getting past your springs... It is well worth the return on your investment...
Mike

 

For what it's worth Dez, I upgraded my wastegate actuators to the EVOM ones and have had no problems whatsoever. Simple bolt-on replacement.

Technically, since the wastegate stays closed with more force, spool-up should be quicker and boost should stay stronger throughout the RPM band with no drop-off.

 

1) The stock spring begins to crack the WG open at between 7-8 Psi, I have checked 3 and they all did this. A K24 with stock spring will still make 1.0-1.2 bar. The mod spring needs to be set to aprox 12 Psi. You will still get 1.2 bar BUT you will not "bleed off" boost at lower Rpm, thus boost will come on quicker with a increase in torque, ie, you "raise the curve" The stock spring will open the WG sooner and "slower" The modded spring will open later and quicker.


2) anything you mod has a chance of breaking.......When you install it you must be super careful that the rod is not in a bind over it's entire stroke, this means you MUST take the little "joint" loose and mess with it while moving the wg through it's stroke. I have even bent the rods on some so as to not bind up, it takes quite a while to get it perfect.

 

That makes some sense, This is something I may try, but I've heard far too many fail stories (many many times on the same cars) on the EVOMS to try that.

Did you change rods as well? How much is the UMW set and is it pretty easy to change?

 

There is an alternative to upgrading the wastegates (actuators with stronger springs that activate at 12psi). The same objective can be reached by using a simple manual boost controller. Use a high quality unit like the Hallman that uses a ceramic ball-valve. For about $100, your wastegates will remain firmly closed until 12psi (or whatever level you set them). Another upside is that it is easier to install.

 

I didn't change the rods. I simply followed the instructions and reset everthing up as recommended by UMW. It cost me $275 for all the hardware.

Mike

 

This is exactly right.

I had mine done at speed gallery. They cut open the stock WG, upgraded the spring and clamped it shut.

The difference was very noticeable. Get it.

This is an altogether different argument. All I can tell you is that the car is much more responsive. You will have tons more torque coming out of corners and will have to be more judicious with the throttle. It will definitely catapult you.

Works prefect for 911s in my opinion. Slow in, fast out, while planting the rears for more traction coming out. Completely counter intuitive coming from any other car and so fun once you start feeling the concept in action. I'm sure you know the feeling better than me.

I have to disagree. A manual wastegate will not give the stock spring any more force. It will still flap open.

 

While you are correct that a manual wastagate (controller) will not give the stock WG spring any more force, you miss the point. Permit me to explain how it works (and I do not mean to sound obnoxious, I am just trying to help).
The manual boost controller (MBC) is placed in the vacuum (boost) line before it Ts off to go to the wastegate actuators. Normally the pressure in the WG lines varies according to manifold pressure, and as the boost pressure increases the wastegate springs resist it until 7-8psi (as stated above) and then start to open. With a MBC preset to 12psi it does not allow any boost pressure to the wastegates until 12psi so they remain closed below 12psi. At 12psi, the boost pressure overcomes the spring in the MBC and a ball controlled check valve opens and allows pressure to immediately flow throught the lines to the two wastegates. The stock wastegate springs then open the wasteagtes (at 12psi). Simple, effective, accurate and cheap.

 

The stock wastegate actuator spring will still have less force applied to the wastegate flapper, and although an MBC/EVC will delay this by altering the "signal" to the actuator, a stiffer wastegate actuator spring will still always keep the flapper shut harder and longer than the stock one, resulting in the increases described above by ari.

Think of it this way - you disconnect the vacuum line to the wastegate actuator altogether. No signal. The performance of a stock actuator versus an upgraded one will be drastic. The stock one will crack earlier (7psi) just due to built-up pressure on the other side of the flapper door forcing the weak spring open, and will also fully open under a certain pressure (this will not of course give unlimited boost). An upgraded actuator will open strictly under pressure at a higher threshold (12psi+), and fully open at a higher pressure as well.

Although the boost controllers work to an extent (eliminating the solenoid which does the same thing for the stock ECU), upgraded wastegates will always make the response curve sharper (by physically being able to stay closed longer) and possible maximum boost pressures greater. Stock wastegate actuators will always open earlier, and as such boost will "hit" more softly due to the leak through the wastegate opening.

 

Interesting. This is a tough decision because I do bog out of some turns and I imagine this would help get back into the powerband sooner, but some turns it would be harder to control at the limit with all that torque coming in early. I may just try it.


Sounds kind of peaky though, rather than smooth with the power output.

 

The issue is that the elevated exhaust pressure caused by more boost (fuel being burned) pushes against the wastegate flap and forces it open. As such, I don't think it's an issue of wastegate actuation. Most K24 flashes (includes most hybrids) actually direct the ECU to maintain 1.2 BAR, it's just not physically possible with a the wobbly stock WG springs.

I will admit I'm not 100% certain on the EBC/MBC topic since I don't have one on my TT, but I'm pretty confident on the issue. I have installed many versions including EBCs, MBCs and home made devices that used brass valves from home depot on various RX7s, Ecplipses, etc in the past.

No obnoxiousness taken or given. We're just debating.

 

This actually is pretty simple... The spring tension isn't enough to overcome the pressure... Swap the springs, and what Oak described is what we've all experienced... Set up the rod travel so there is no bind and you won't break them...Dez, I don't know who you've been seeing swap their rods, but I'd bet money they aren't setup properly... I set my own up and have had zero issues. If I can set them up, any mook can!

Mike

 

jimmer and ari- I see your point. Thanks for the clear explanation. So the question is, how much pressure is developed against the WG valve when the manifold pressure is at 1 bar? As the exhaust gasses travel through the turbine housing they come to an unequal Y/split, with the major pathway going to the turbine and the minor pathway to the WG valve. Does that minor WG pathway produce pressure equal to manifold pressure? I am not sure but I would be surprised if it did. If that was the case then there would be little reason to have a boost line controlling the WG. And it would make it impossible to raise boost with only ecu modifications. Is my logic correct? I think stronger WG springs are certainly a good idea but we are only talking a few psi difference here. It's not like the 40 psi Supras that can make a 45mm wastegate bleed.

 

Dez, I'll give you a great comparison... Last year, at VIR's Oaktree, where I'd usually bog in 3rd gear coming out, but didn't like the feel of the dual mass flywheel slowing my shifts, I'd end up leaving it in 3rd and not see more than 160MPH on the back straight... After doing the LWFW and the actuator springs (and the umw tune and 5bar fpr) the throttle cleaned up so much and was so much more linear that it was very easy for me to jump on 2nd gear and get around oaktree and back up and running much much quicker... To the tune of 172-175mph back straight speeds. From what I've been told by others who've done the wastegate spring mod, that spring is a big part of the picture, and that crisp throttle is something I simply can not live without anymore..

Mike