Blowtus

I have a stock, 1988 t2. I'm not really interested in upping the boost at this stage, but I'm very keen to see if I can get it boosting quicker and harder. Has anyone done much experimentation with wastegate control on these things? I'm led to believe that my wastegate will be opening somewhat as soon as any pressure is on it. Has anyone rigged up any sort of extra plumbing / pressure sensing etc such that the wastegate only opens when boost reaches the max amount? Basically the aim of all this would be to reduce lag and make the turbo hit peak boost lower in the rev range.

Charlie

RETed

Do you still have the stock exhaust?
Do you have emission testing?
If not, get a full exhaust, and then we'll check to see if you have a problem with boost...


-Ted

kep0ne

theres lots of ways to decrease lag. 3" catback (or turboback if you have no emissions)...boost controller. you'll probably have to port the wg too to eliminate creep.

Scott 89t2

the wastegate will not open till it gets the stock 5.5 psi..

Blowtus

stock exhaust is gone, but cats are still in place. Random emission testing here in aus... though not very frequent. I don't really have a *problem* as such, I just wonder if I can make it better with a few dollars on some wastegate plumbing. As it is my torque is peaking very low and staying very flat... lag down low is annoying, but it's reasonably non existant up top.

And isn't creep when the boost rises past the peak boost you want? I'm only peaking at 6.5lbs, so that's not an issue. I just don't want the wastegate to open until that point, or at least open less.

Charlie

Blowtus

scott, are you *sure* of that? My understanding of the situation with older turbo's is that the wastegates are always starting to open as boost rises, opening enough at the peak boost to stop the boost there. A linear, as opposed to on / off motion. Ie, if you block the wastegate line, you should be able to watch boost rise quite a bit quicker.

If I'm misunderstanding something, I'd love someone to explain.

Charlie

NZConvertible

Dead right, that's called wastegate creep (completely different to boost creep). All wastegates to this, whether internal or external.
Electronic boost controllers eliminate wastegate creep by bleeding all pressure out of the wastegate line until just before the set max boost. Then the solenoid closes and pressure is instanly applied to the wastegate actuator. It then works normally to control boost at the set point. The result is much faster spooling of the turbo. So an EBC can make your car considerably torquier and faster without actually raising peak boost at all.
There are cheaper ways to eliminate wastegate creep though. Adding a manual boost controller with an adjustable valve in the cabin has exactly the same effect (although not as much), because it takes longer to fill up all the extra hose with enough air to create the pressure required to open the wastegate. The result is faster spooling even if peak boost is the same.
An even more effective method is to tee a small volume into the wastegate line. Again the extra volume that needs to be filled slightly delays the wastegate's opening. With the correct size volume, overshoot is zero. However a little bit of overshoot is okay (because at lower revs there's still plenty of capacity in the fuel system) and will further increase performance.

NZConvertible

I found an old post of mine about teeing a small volume into the wastegate line. This graph shows boost vs. rpm after doing this mod to a 3.0L turbo six-cylinder. A 250cc volume was used. This gave a huge on-road performance increase, the earlier arrival of boost significantly improving low-mid range torque. Note max boost doesn't change, so no extra demands are put on the fuel system. This is about the best $20/half-hour you can spend on your turbo car.

Blowtus

cheers nz, just what I'm after. You've done that mod I imagine? Any thoughts on the extra volume that should be plumbed in??

Charlie

NZConvertible

I haven't used a tee'd volume, but I made a pnuematic boost controller for my 12AT Cosmo with a valve in the cabin, and it did boost up a bit quicker, even before I raised the boost.
I plan to try the volume idea on my FC, but it's on the long to-do list.
The car in that example was a VL Turbo, and the volume was made from a short section of exhaust tubing with capped ends and hose nipple brazed on. I've also seen an old aerosol spray can used, with a threaded nipple screwed into the top in place of the valve.