Adding an Intercooler - Technical Question

[JTaylor2005]

Alright guys,

I am planning on fitting an intercooler on my HDi soon. One thing I am wondering about is how is best to pipe in the wastegate actuator. 

I won't be upping the boost just yet but my idea is as follows.


Leaving the pipe work as is would mean that the actuator relies on the pressure seen on the outlet of the turbo (Which is probably assumed not to drop much between there and the intake on the stock setup)

However when I add an intercooler and all the extra pipework, should I move the actuator pipe input to the intake manifold for example? That way it will take into account the pressure drop across the intercooler etc and keep the boost at the same value as before the intercooler was fit. Theoretically then I would be getting the same boost pressure as I am currently, but with a much cooler denser air.

Thanks guys,

Jack

[Uberderv]

Interesting idea, you could stab in at the intake and if it doesn't work as expected it will be easy enough to fit an MBC at a later date.

[Ruan]

It makes no difference as long as your feedback (i.e. what you're looking at when adjusting) is being fed from boost pressure in the inlet manifold. The measured boost at the inlet is what's important here, the adjustment of the boost controller is irrelevant - as long as the boost pressure seen at the inlet is the same. Just make sure to have the lines to the actuator and from boost pressure as short as physically possible, otherwise you get large boost overshoots as it takes time for the lines to fill with pressure and you can get quite big oscillations. That's precisely why the actuator as stock is fed from the compressor cover, simply to keep the line length as short as possible.

[JTaylor2005]

Okay mate sounds good. I am just working on the assumption that pressure drop from the turbo outlet to the intake manifold intake currently is very low. With an intercooler that difference would be bigger.

So if I left the pick up point as the outlet of the turbo then the intake would see less as it will drop over the pipe work run. If I move it from there turbo to the intake it will keep the intake pressure the same as now theoretically.

[Ruan]

Yes, that's correct, but if you're going stage 2... Then you're adjusting it, I'm not sure why you're worrying so much as you're adjusting it anyway?!

We're talking a few hundred millibar if that here, it's gonna make shit all difference.

[JTaylor2005]

Ahhh fair enough! I thought pressure drop over a cooler was quite high.

[Ruan]

Remember - your boost controller isn't set for "x psi", it's merely set for an amount of pressure required to move the actuator arm enough to divert enough exhaust gas to maintain the level of boost you want. Pressure drop across the intercooler in this situation is irrelevant.

Pressure drop is important when you're considering the compressor map vs the engine's VE%, which you're not.

You want to see x psi in the inlet manifold - your boost gauge will tell you this and you're adjusting the boost controller in response to this. You'll probably see a 2psi drop across the intercooler if it's really shit.