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Discussion Starter · #1 ·
On my Maptun Stage 4 quest (9k with TD04) I am looking at 2 actuators:

1) Maptun uprated exchange unit - about £70 exchange. (Seems to have disappeared from the website though)

2) Forge Actuator - £100

For the extra £30 I was thinking the nice new chunky forge item would be better but wasnt sure what springing I would need. 9-15psi is the initial spec but is this the max boost you'll run or the base boost spec? - i.e. If it's max boost, I'll need at least the 14-18psi spring.
Also - given it's the TD04 I think I need the straight ended 120mm actuator rod?

Anyone done the same? / Recommendations welcome!

Cheers!
 

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Plenty of stuff on this previously, but basically you need your actuator spring to be about 1-2psi less than the base boost specified by your tuners in order to allow adequate preload.
 

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Maptun said they don't do an exchange basis anymore when I asked them a couple of months ago. Maptun UK will supply it shipped for just under £125 and Maptun Sweden e-mailed me back to say they would sell me the uprated springs but not an exchange.
 

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Discussion Starter · #4 ·
Thanks gents - That helps my decision if Maptun no longer do exchange - I'll probably go for the just go for the Forge item as it's a little cheaper looks sturdy, serviceable and has a range of springing.
I'll mail maptun to see what the recommended base boost/spring rate is for stage 4, and get one ordered up.
 

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Hi mate

I recently bought a Forge actuator but have now put the stock one back on. It was'nt anything to do with the Forge unit, only I could'nt get it set up properly. I made up my own bracket and I think what may have been the problem is that the brackets too thick


Anyway the Forge actuator is well made (and sooo shiney ) I do intend to get it back onto the car, just need to get some time to spend on it to set it up right.

How are you finding stage 4? Have you done the complete stage 4 upgrade or just the ecu?

Zahid
 

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Discussion Starter · #6 ·
Reading the spec for the forge, I thought all I needed to do was get the Forge with the straight control arm of the correct length - didn't think I'd need to make a bracket also

As for stage 4, I have all the hardware but running standard ECU until Mapun come back from their hols.. can't wait! Standard is dull.
 

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the bracket bit put me off also but was quite easy. Alternatively you can use the bracket on the oem actuator. However getting it off looks a bit of a mission but probably the same as making up a bracket
I'll probably end up doing this.

Let us know what spring rating MapTun recommend


Zahid
 

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Discussion Starter · #8 ·
Well based on a bit of checking out and from what bubbles says:

Generally 0.5Bar should be the base boost on TD04 - maybe up to 0.6Bar for highly tuned stuff but I dont see any real advice on ever setting it higher.

Based on having the minimum wastegate springing being just below the base boost, then we'd need to use the green 5-10psi (0.35-0.69) spring. The next one up is the yellow 8-15psi (0.62-1.03Bar) and on this theory at least would be too strong as the lowest base boost you could ever have would be 0.62

Now if I need the green spring, I am left confused as to what has actually been uprated?
I assume at high boost, the spring is irrelevant and it's the actuators ability to stay closed and not leak that's the key here? Answers on a postcard...
 

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Discussion Starter · #10 ·
Thanks Bubbles - that filled a few holes but I still dont have a clear view of how it really works:

This is what I THINK happens:

Firstly I believe that during base boost, all the pressure from the turbo INLET is passed to the Wastegate.
So - if the wastegate is set to 0.5Bar, then at 0.5Bar INLET pressure, the spring on the actuator will compress, pushing the wastegate open and preventing any more pressure building.

Above Base Boost:
To get higher boost, the boost solenoid limits the amount of pressure sent to the Wastegate Actuator. This means that the actuator will not open until the solenoid decides to send 0.5bar pressure or more to the actuator(this might not be until 1.5bar real inlet pressure is reached though). If the spring it set to 0.5Bar, then to my mind it wall always open at 0.5Bar on the inlet to the actuator.

What I dont understand is if the spring must be preloaded to 0.5Bar for base boost, what is the uprated spring actually doing?
In my example above, the wastegate actuator will never see any more than base boost (even if high inlet pressure is run).

Also - is the wastegate forced closed by the exhaust gas, and the actuator pushes it open? Or is it forced open by the exhaust gas and the actuator is trying to hold it shut?
I think it is the first scenario as you get 100% boost with the W hose disconnected from the Wastegate.

PS - A simple diagram would explain this to me but I cant seem to find one... and I know I have some twisted logic in there
 

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If it helps, I have the 5-10psi spring and it seems to work really well. No overboost or any other nasties, but I am getting plenty of oomph, which I was not before as my old one had gone weak.

Not sure what boost I would get now, but I think before, it was something like 18-19psi peak.
 

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Discussion Starter · #12 ·
I think I have realised my fundamental flaw in this topic:

The exhaust gas pressure is related but generally has nothing to do with the boost pressure..

i.e. If I'm running 1.5Bar boost, the exhaust may be nowhere near it.

So - back to the spring conversation:

To get the recommended/preset 0.6Bar boost with the forge actuator, I must use the 5-10psi (0.35-0.69) spring but could maybe just get away with the yellow (0.62-1.03Bar) fully loosened.

This sets the base boost pressure and gives better than standard resistance to the wastegate being forced open at higher exhaust pressures as Bubbles states in his thread.

I think trying to relate the Max boost (say 1.5bar) to the springing in the actuator is wrong. All the actuator sees is either a 0.6bar pressure from the Solenoid to open it, and exhaust gas pressure which it needs to resist(which I assume is nothing like the inlet pressure levels).

All this just to choose a spring
 

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i'm running the 9-15 psi spring with very little preload (1 turn)

this works better for me as I needed the 5-10 psi spring done up so tight to get base boost, that I then got boost creep above 4500rpm as the wastegate had so little movement left.

Also, I think that the pre turbo exhaust pressure is 2-3 times that of the inlet pressure. this is the pressure the spring is resisting.

Andrew
 
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