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Checking wastegate

Steve

By Steve,
in Engines & Forced Induction

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Steve Grand Master

Steve

Posted
Posted

Hi all

Just wondering if anybody knows of a way to check wastegate function without removing the gate from the manifold.

I have a HKS 40mm standard (external) gate, and I suspect it may not be working too well.

Firstly varying my duty cycle (from 20% to 90%) on the boost controller makes virtually no difference to how quickly boost comes on and

Secondly, it seemst to make the first 5lbs of boost quickly, from there the speed at which boost is built varies, reaching 1 bar of boost can vary by as much as 3-400rpm.

All testing I have done was on the road, flat surface in second gear, ie, consistently the same conditions.

The boost controller is a power fc driven solenoid (AVCR type) and was holding boost well, and bringing boost on quickly when I had stock turbo, so I suspect the problem isnt there.

Any thoughts?

Cheers, and have a great new year:)

Steve

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Sydneykid Grand Master

Sydneykid

Posted
Posted

Hi Steve, if you are suggesting that the wastegate maybe leaking, then the first thing I always check is the standard spring tension ie; no boost controller. If it has a 12 psi spring in it then it should hold 12 psi. If it doesn't, then try changing the spring.

I always run a spring with a rate as close as possible to my minimum boost requirements. This saves the boost controller solenoid from working its butt off bypassing so much pressure.

I also test the wategate opening by checking the temperature of the wastegate outlet pipe. That tells you when it opens. I have a high temp probe on my multimeter and I just clamp it to the pipe with a stainless steel hose clamp.

A couple of runs will quickly tell you when it is opening (I cool it down quickly with bucket of water between runs).

I have seen guys use a length of hose mounted close to the wastegate and running into the cabin. Put it up to your ear and you can hear the wastegate open. Best done with a passenger I reckon.

Their latest trick is to point a video camera at the instruments and then they can replay everything in slow motion. You pick up all sorts of stuff that way, things that happen too fast when you are driving.

Hope that helps

Happy New Year

Steve Grand Master

Steve

Posted
  • Author
Posted

Well wastegate and solenoid seem to be working fine.

so this means the problem is somewhere else.

The turbo starts making boost at around 3000rpm, makes 0.3bar at 3200, 0.8 at 4200, and then 1.3bar at 4800.

Any ideas? It hesitates between 5lbs then around 4000rpm boost climbes pretty quickly.

Is this quite normal, as it used to climb quite linearly until it got to 0.8 bar (0.61 turbine housing vs the 0.87 now) and then just went nuts before, but there wasnt any flat spot as there is now?

Anyone seen this before?

BU5TER Grand Master

BU5TER

Posted
Posted

Sorry I'm no help Steve but I had a couple of wastegate questions aswell I hope thats ok

Is it true that what ever you wastegate boost is when the EBC is turned off say .7bar in my case the max it can boost to is 1.4bar ie double and to make this say hold 1 bar with no EBC its only a matter of changing the spring?

Steve Grand Master

Steve

Posted
  • Author
Posted

Buster, I can confirm changing the spring will change the min amount of boost, not too sure about max boost though, suppose it depends on what sort of EBC you are using?

Joel, it has had a road tune, spend 2 days getting the part and full throttle tuned, but I am pretty sure the AFRs are still too rich.

Pretty sure too that there is a vacuum leak somewhere. I blocked the PCV valve as this was leaking, also changed every clamp on the boost side (after the turbo) to the large bolt type clamps. I have checked all the vacuum lines and clamped/cable tied them all. Still cant help but suspect a vacuum leak, as idle is still hunting a little, plus when I blocked pcv, then redid all hose clamps idle quality improved (it was hunting heaps), but still far from what it should be.

Boost is strange, sometimes it comes on earlier than at others, I have had 1.3bar at 4300rpm, but usually it only makes around 0.8bar at 4200 - 4300rpm, then climbes rapidly after that.

Usually though the first 5lbs of boost comes in pretty quickly - perhaps it is just the tune, but I suspect something else is amiss, and is being exacerbated by the manifold design - as I am 100% sure everything else on the car is a good thing. (and I have checked the BOV by tightening it about 6 turns, but it wasnt leaking before the cams/plenum etc went on, so it shouldnt be leaking now.)

Sorry getting off track - It will be going into tilbrooks on monday for a tune - they are going to re-dial in the cams too, which probably wont acheive much (may have a HKS adj cam gear spare soon:))

I checked the cam specs on dyno 2003, and guess what? It looks like they are set up right from the factory. I tried advancing the inlet (as per NVCS) and this picked up the midrange heaps, which is reflected by disconnecting the NVCS when on the road. Interesting too that the power starts to drop after 4500rpm where nissan swicth off the NVCS, so it seems to apply to stock and aftermarket (or at least in the case of 256) cams.

Anyway, I have 6deg of retard on the exhaust cam, which I am not too sure will be helping things much. I tried this too with dyno 2003 and it killed power. On the road, it sort of dies above 6000rpm, so I am suspecting there is just too much seperation. Hopefully with exh cam re-centred and AFRs/timing redone, things will improve somewhat.

Then I will fit a smaller exhaust housing:) probably doing things a bit backwards, but I want to be absolutely certain I have milked everything out of the current setup before I change anything yet again.

BU5TER Grand Master

BU5TER

Posted
Posted

Sorry mate I'm hopeless in explaining what I mean sometimes I find with my wastegate I can run 25psi or what ever I set it at above 19psi with the EBC but no matter what it always bleeds slowly back to 19psi the tuner told me I had a to soft spring in the gate and If I put in a stronger spring it would then let the ebc work and hold 22psi does this sound right?

Sydneykid Grand Master

Sydneykid

Posted
Posted

Hi Buster, you asked "If I put in a stronger spring it would then let the ebc work and hold 22psi does this sound right?"

Yes, the closer you have the wastegate spring to the boost you run, the less "work" the solenoid has to do. There is simply a limit to how much boost the solenoid can bypass. You may well be asking it to bypass more tha nit physically can. Note that this is a function of both airflow and boost pressure.

Hope that clarifies

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