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200 tdi boost pressure with larger intercooler


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1 hour ago, Snagger said:

Would you not get the same boost pressures, just with a slightly longer lag?

This is my understanding.

I run a Brunel Performance standard size high flow intercooler (so i think a slightly bigger volume to an OEM one but better cooling) and have it set at 1.4-1.5 bar max, but that means that I can comfortably stick at 1.0 - 1.1 bar with the overdrive engaged at 70-75mph on the motorway. I cant get 1.5 bar of boost when in 5th + OD so have used this to set my max boost to ensure i have that little bit of acceleration when needed on the motorway. Shift to 4th and it can go up to 1.4-1.5 bar at full throttle, but you manage that by not completely burying your foot!

Its been like this for about 8 years with no real issues. I did blow a head gasket about 1.5 years ago but it was likely the original one at about 250k miles I think. The engine is tip top.

I run a boost gauge and just control it via the wastegate

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Much obliged to you all for your responses !

I've fitted a wide Allisport intercooler and I'm looking to increase boost to provide more air to burn more fuel.

Currently it tops out at 14 psi which is a shade under 1 bar and pretty much standard.

Just curious to see what others are running regularly and reliably. 

Allisport state that you need to increase boost to take advantage of the larger intercooler but offer no guidance on how much.

Thanks to you all.

If you haven't posted yet please do, the more information I have, the better idea I have of where to start.

Cheers

Mo

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4 hours ago, Mo Murphy said:

Sorry Snagger, under what circumstances? 

I think Snagger means that if you set the boost pressure to 14PSI and then change the intercooler it will still make 14PSI, just a little slower due to the increased volume hence the increased lag to hit full boost. Increasing boost on a normal size intercooler increases charge intake temps, but fitting a larger intercooler and more cooling should allow you to increase the pressure you are running at.

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5 hours ago, Mo Murphy said:

Sorry Snagger, under what circumstances? 

The turbo produces a boost pressure, but the bigger void of the larger intercooler would take longer to cram more air into than the standard size, and similarly a boosted large intercooler is a bigger reservoir of high pressure air than the standard unit, so any change in boost pressure, up or down, would take a little longer to stabilise.  That is a boost lag rather than classic turbo lag, but would manifest in a similar way.  Shouldn’t be much of an issue for most of us, but it might be noticeable for those who drive fast and tune their engines.

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Is there not a mod you do where you plumb the wastegate into the intake manifold ? So you are measuring the boost at the intake manifold and not the turbo , I think I read it in the tech archive in white 90's tweaking the fuel pump post or one of the posts doing similar .

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You may get slightly more pressure at the turbo compressor outlet than the manifold, but it shouldn’t be much unless you have some flow restrictions, like the intercooler being clogged or too small.  Density should be higher in the manifold than the compressor outlet if the intercooler is doing its job, but pressure will attempt to be even from the compressor all the way to the valves.

I’m curious.  A colleague was going to bin his standard TD5 intercooler, in very good condition, so I saved it.  Is there any benefit in fitting that to my Tdi?  It’s a lot bigger, so should be freer flowing and drop the temperature more, at the cost of that little increased lag that wouldn’t bother me at all, but is it worth the trouble of new mountings and hoses?  I have the space for it, but if there is little benefit, i don’t want to waste time and money in making the engine bay less tidy.

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1 hour ago, Snagger said:

 Density should be higher in the manifold than the compressor outlet if the intercooler is doing its job, but pressure will attempt to be even from the compressor all the way to the valves.

No, because there is a flow in the intake system. It is not static. You are right, if you view it static.

The limit of the turbo itself may be at about 1.4 bar to 1.5 bar measured at the turbo.  It is simply not interesting, which pressure at the valves is resulting. With 1.4 bar at the turbo you are close to a maximum. Thats it.

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17 hours ago, ianmayco68 said:

Is there not a mod you do where you plumb the wastegate into the intake manifold ? So you are measuring the boost at the intake manifold and not the turbo , I think I read it in the tech archive in white 90's tweaking the fuel pump post or one of the posts doing similar .

I've always thought that this was a but pointless. The wategate is there to protect the turbo as much as anything isnt it? I dont know what the difference would be between the reading at the inlet manifold and the turbo, but surely you would still need to set the boost to whatever limit you choose at the turbo? So if there is a difference of 2psi between what is measured at inlet manifold and turbo (presumably less at the inlet manifold?), if you wanted to limit the boost to protect the turbo at 14psi,  you would just set the wastegate to open at 12psi if you are measuring at the inlet manifold? If you set it to 14psi, the turbo would see 16psi?

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3 hours ago, Snagger said:

I’m curious.  A colleague was going to bin his standard TD5 intercooler, in very good condition, so I saved it.  Is there any benefit in fitting that to my Tdi?  It’s a lot bigger, so should be freer flowing and drop the temperature more, at the cost of that little increased lag that wouldn’t bother me at all, but is it worth the trouble of new mountings and hoses?  I have the space for it, but if there is little benefit, i don’t want to waste time and money in making the engine bay less tidy.

The oversized tdi intercoolers are reverse flow so the air travels in one side across the top (I think) of the intercooler, then back across the bottom to the same side - this reduces the pipework needed as the turbo outlet and inlet manifold are on the same side of the engine. On the TD5 the turbo is one side and the inlet manifold the other so the intercooler is set up so the inlet is on one side ad the outlet is on the other. So.... if you fit the TD5 one to your tdi, you will need a big pipe to go from one side of the car to the other which might i suppose might increase air temps and negate the use of that intercooler.

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5 hours ago, reb78 said:

I've always thought that this was a but pointless. The wategate is there to protect the turbo as much as anything isnt it? I dont know what the difference would be between the reading at the inlet manifold and the turbo, but surely you would still need to set the boost to whatever limit you choose at the turbo? So if there is a difference of 2psi between what is measured at inlet manifold and turbo (presumably less at the inlet manifold?), if you wanted to limit the boost to protect the turbo at 14psi,  you would just set the wastegate to open at 12psi if you are measuring at the inlet manifold? If you set it to 14psi, the turbo would see 16psi?

Assuming you moved all the boost sensing to the manifold,  it just the waste gate actuator, you’ll be getting less fuel boost.  You’d need to recalibrate the pump accordingly.

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