legacycentral bbs

Okay, I reconnected my boost controller to the vaccum attachment on the turbo thinking it would solve my surging problem. Instead, I noticed that just before I hit boost, the throttle would give more resistance and then I'd hit boost. Letting off the throttle would make the car continue to boost and accelerate for a little bit . . . not good.

Could this be a throttle problem? Recirc valve problem?

I tried working the throttle again, but this time when I let off the gas, the car didn't surge and I heard the recirc valve letting off pressure.

Resistance? Do you mean the pedal was harder to press? The throttle shouldn't ever be easier or harder to press; you're just pressing against the spring on the throttle body.

With the boost control coming from the compressor outlet, you will naturally have less immediate "jump" than you would controlling the boost from the manifold, because the turbo isn't spinning up really fast until you open the throttle.

I don't understand how letting off the throttle could make the car continue to accelerate, unless maybe somehow you have enough boost pressure in the tubing between the turbo and the throttle that it presses the butterfly valve open. I thought traditionally blowoff valves were meant to prevent the turbo from suddenly stopping, but I guess boost pressure could theoretically hold a throttle valve open. I haven't looked at the inside of a Subaru throttle body.

Have you tested your blowoff valve? I'd say to start there...

Taking a look under the hood I noticed that by manually moving the throttle position that there was varying degrees of resistance (not electrical resistance, but a force). As I'd move through the full range of the throttle movement, it would go from normal, to just a bit harder to normal again. I really think the problems in the throttle.

Looks like I might have to go back to the yard this weekend, unless there's some way to remedy this without a new throttle body.

Well, you can certainly start by cleaning off the throttle cam and re-lubing it... Try maybe brake cleaner and a toothbrush and then some general purpose oil? Don't forget to check the cruise control cable too if that's relevant. You might want to clean the inside of it with air intake cleaner or carb cleaner or something too.

I'm not sure that the throttle feel is meant to be linear to begin with, though. But if your cam is actually harder to push at certain positions that might make it stick open a little and give you the bad behavior you're describing.

Don't clean the inside of the throttle body. If your throttle body has the black goo on it that was meant to help prevent carbon buildup it also serves as a sealant, and you can have idle issues afterwards.

Try turning the throttle cam with your hand. That way you can see if the tension is non-linear, by taking the cable pulling on the cam and giving you different leverage ratios.

I'll try turning the cam . . . I drove the car today and didn't get any of the issues with the throttle. It doesn't have the same feel . . . it's more linear now. *shrug*

As for the PTFB issue with running the boostcontroller off the manifold, I tried hooking up the bc of the turbo . . . no difference, only throttle response (spool up) was slower . . . I returned it to the way Adam had it set up.