Thread: TD5 waste gate actuator operation

Encouraged by all the useful contributions these last few days I did some investigations myself this morning. I wound out (lengthened) the waste gate rod until i observed the WG begin to open and then I progressively shortened the rod to close the WG - I was looking for the closed / open threshold point. It's easy to determine that threshold point because you can feel when the WG is closed because the knurled adjusting nut gets quite difficult to turn because when the WG closes the WGA rod begins to pull against the WGA spring. When I was happy that the WG was closed and the WGA spring 'just' engaged i measured the rod length between the WGA and the adjuster link assembly and it was 54mm. I decided to shorten the rod to 52mm to ensure positive closure of the WG and leave it at that being satisfied that it's just about at the minimum WG adjustment. I nipped up the lock nut and counted the exposed threads on the WG rod for an easy working reference and there's 15 or 16 depending on if you count those on the upper or lower side of the rod. The exposed length of the rod to the lock nut is 47mm.

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Originally Posted by sierrafery

I've set the WGA's rod longer than stock on mine cos i observed that this way i've got rid of those tugs which can be felt when the throttle is kicked down or suddenly released... as mine is manual this symptom is more noticeable than on autos

Do you see what you are doing here?

The WGM reduces pressure at the actuator.
By lengthening the arm you are lowering the actuator pressure at which the waste gate opens.

In other words you are fixing what sounds like a boost spiking problem by reducing the effect of the WGM.

Originally Posted by OffTrack

Do you see what you are doing here?

The WGM reduces pressure at the actuator.
By lengthening the arm you are lowering the actuator pressure at which the waste gate opens.

In other words you are fixing what sounds like a boost spiking problem by reducing the effect of the WGM.

So thinking out load,

If I install the pressure bias valve (ball and spring type with no bleed hole) before the WGM to open at ??? pressure and then set/increase the WG rod to similar to onebob (i'll do the same procedure to ensure at rest the WG is closed etc) I should see lower pressure to operate the WG actuator so is should open only at the preset pressure and even if the modulator is trying to open more it will not because of the set limit??

Or am I getting it wrong?? is this what offtrack is saying re over shooting of boost will happen??

Maybe just leave the WG rod would up and wait till we can remap the ECU and WG control??

Cheers Lemo

Originally Posted by OffTrack

Do you see what you are doing here?

The WGM reduces pressure at the actuator.
By lengthening the arm you are lowering the actuator pressure at which the waste gate opens.

In other words you are fixing what sounds like a boost spiking problem by reducing the effect of the WGM.

I'm not going into a debate with you on this cos i respect too much your research... i'm just saying that the way i set things regardless of electronic maps(which at this moment and possibly in the future too) are exceeding my knowledge made the vehicle behave better... that's all i can say based on live drive tests without a boost gauge fitted ONLY based on sensor inputs and personal feelings.... i have an ideea about what's going on but it might seem too rudimentary for you or even wrong and i dont want to go into any polemic


as i said in a very old post here i'm focused more on what's happening around the sensors and ECUs as real life behaviour of the engine even though it can be illogic or contradict the theory... unfortunately i have serious familly issues to resolve now and i dont have the time nor the mood(or the cerebral health) to make tests with pics or videos to sustain my statements.

Originally Posted by sierrafery

I'm not going into a debate with you on this cos i respect too much your research... i'm just saying that the way i set things regardless of electronic maps(which at this moment and possibly in the future too) are exceeding my knowledge made the vehicle behave better... that's all i can say based on live drive tests without a boost gauge fitted ONLY based on sensor inputs and personal feelings.... i have an ideea about what's going on but it might seem too rudimentary for you or even wrong and i dont want to go into any polemic

as i said in a very old post here i'm focused more on what's happening around the sensors and ECUs as real life behaviour of the engine even though it can be illogic or contradict the theory... unfortunately i have serious familly issues to resolve now and i dont have the time nor the mood(or the cerebral health) to make tests with pics or videos to sustain my statements.

What I'm saying is you are most likely going to be better off not using the WGM. Bypass then adjust the MBC to desired boost pressure instead.

You don't appear to have tested that configuration in your experiments. From what you have written you tested the MBC at 225Kpa and came to the conclusion it was worse than WGM + MBC. Please correct me if that is wrong - I can only go off what you post here.

The most that requires from you is 10 minutes to change the setup and a test drive. It doesn't require argument or videos.

Thanks to all who contributed to this thread and educated me on boost and waste gate operation. The end result was a solution to my over boost issue and my new "relaxed" waste gate setting is now keeping the boost within sensible limits. This is a great forum, thanks to all

Originally Posted by Lemo

So thinking out load,

If I install the pressure bias valve (ball and spring type with no bleed hole) before the WGM to open at ??? pressure and then set/increase the WG rod to similar to onebob (i'll do the same procedure to ensure at rest the WG is closed etc) I should see lower pressure to operate the WG actuator so is should open only at the preset pressure and even if the modulator is trying to open more it will not because of the set limit??

Or am I getting it wrong?? is this what offtrack is saying re over shooting of boost will happen??

Maybe just leave the WG rod would up and wait till we can remap the ECU and WG control??

Cheers Lemo

What I'd suggest:
If you have the arm wound up already and are happy - leave it and don't worry too much.
If you want to replace with an MBC, use the MBC alone and bypass the WGM.

I'll PM you about the third option

Originally Posted by OffTrack

...
You don't appear to have tested that configuration in your experiments. From what you have written you tested the MBC at 225Kpa and came to the conclusion it was worse than WGM + MBC. Please correct me if that is wrong - I can only go off what you post here.

The most that requires from you is 10 minutes to change the setup and a test drive. It doesn't require argument or videos.

You are right, i've set the MBC as to work well up to 240 MAP together with the WGM then bypassed the WGM for test without touching the MBC and got 225 so i presumed that the difference between 225 and 240 is the gain of the modulator and i was pleased this way considering that i have some electronic wastegate control too.

anyway, i can do the test as to adjust the MBC to get 240 without WGM no problem but i feel a kind of remorse to get rid of the WGM cos it was bran' new at that time and seemed a waste of money to me to not use it after i paid for it .... maybe if it fails i'll not buy another and adjust the MBC and rod to the best setup i can

it would be a shame also not to use a WGM after all the research you made to prove how it works