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Author Topic: RB20DET super slow off boost - timing? wastegate?  (Read 1713 times)


  • RB20DET
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RB20DET super slow off boost - timing? wastegate?
« on: January 18, 2015, 07:54:00 PM »
Now that my 20det is up and running i've noticed it's slow off boost. Like not just "haha it's an rb20 that's why" sorta slow, but like, struggles to move sort of slow. It seems to happen when the engine is cold. After a good run on the motorway it doesn't seem to be there/as bad (probably just normal rb20 speed)

Thing is, it's totally fine when it gets onto boost. It'll be sluggish as all hell until the turbo spools and then it just pulls like it should.

The engine is running off a 25de loom and radiator which share all the same plugs so i'm not sure if that'd be the problem.

Mechanic said the timing might be retarded but i checked it when it was at operating temperature and i adjusted it to ~15 degrees, and it still does it.

Could the wastegate be stuck open? Or maybe not closing fully?

Any other switches/electronics that could be causing this?


  • RB26DETT
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Re: RB20DET super slow off boost - timing? wastegate?
« Reply #1 on: January 24, 2015, 03:06:56 PM »
That's normal during warmup, as the stock ECU pulls ignition timing to drop torque / hp to protect engine from bearing damage (also to match engine running richer). If you rev over I think was roungly 3000rpm (normally you wouldn't rev above roughly 3000rpm while engine is warming up) or is above certain coolant temp the stock ECU switches out of this warmup mode.

It gets worse / more noticeable if have breathing mods. It can be tuned out, but normally you have to put up with it or warm engine up before driving to avoid that mode. Ask you local Nistune dealer / tuner.

The CAS is set to the transmission, ECU you are running (manual with 15 degrees BTDC or auto with 20 degrees BTDC).

From my experience, if the internal wastegate actuator causes that sort of problem, you would hear a rattling sound from the back of turbo (internal wastegate spring is stuffed).