Dawes and needle valve clarification please.

[Ben81C]

All other advice from here i have taken with catch can already fitted, boost and EGT gauges (autometer) ordered today and as an extra i am having a turbo timer fitted in 2 weeks. EGR block after i decide on my method of boost control. What to do what to do??????

[Rusty86]

I'm no expert and usually go on the advice of those in the know like Chaz and a few others. The links on Chaz's site probably explain things the best and easiest to understand.

I'll leave it to others to explain why the Dawes and Needle set up is the best way to go. It's definitely achieved great results for people that install it
Cheers,
Rusty

[mudski]

I'm no expert on this as I'm still learning but I thought the dawes was to control the spool up rate of the turbo ( making it spin up faster or slower) and the needle valve is there to control the boost.
From what i have read and understand this is how the setup works. If it doesn't work the way it should I'm sure there would be hundreds of users from here, and other 4by forums scratching thier heads. If I have time I'll pop into JPC in Thomastown and ask Mark their. If anyone knows this bloke will. He does this shit for a living.
OT, I was talking to the chaps at 4x4 Solutions yesty and he said if you want to 4by to wheelstand go see JPC. If you want your 4by to go a bit better and have better fuel economy, go see Ray at Turbo Engineering....

[Rusty86]

Other way around, Needle controls turbo spool up rate and with Dawes you set max boost pressure

[mudski]

Yer thats what i meant...

[Chaz]

I have spoken to a few trusted mates some of whom are mechanics including the diesel specialist i use (who said they used to fit Dawes and needle valve but not any more) and some are just car nuts, they all say the same thing, and that is that they cannot work out how the Dawes valve could stop over boosting, they all say over boost is caused almost exclusively by the waste gate failing or as was explained to me today by the bloke i ordered my boost and EGT gauges from that u can think of overboost as a shop with a front and a rear door, say you can only have 6 people in at once (say 6psi) with standard boost control, as the 7th person (or 7psi) enters the shop, at this point the door at back (ie wastegate opens) and the first person (or psi) exits the rear and only 6 remain inside. However there can be a delay from when the signal to open the rear door (wastegate) and when this actually happens (ie open wastegate) and this is where the problem begins as 7,8,9 and so on can be forcing there way through the front door as the rear door is trying to open, they cant get out before more come in and presto over boost.
Every single person i have asked has said no you need to install an electronic boost controller as they actually take proper control of the waste gate by monitoring and controlling boost and take into account the pressure building via exhaust? What is the go?
Also i showed the people i asked the install diagram from this site and they all scratched their head in confusion as to how the Dawes valve really does much at all with regard to over boost? I am now confused as every one here says there great but i cant find any body else who will fit one or even knows what their purpose is, i am seriously thinking of going for the electronic boost control over the Dawes valve.

Ben81C,

It sounds like none of your mechanic mates or diesel specialist are familiar with the VNT controlled turbochargers used in almost all late model diesel cars. Variable nozzle turbochargers don’t use or have a wastegate and unlike a conventional wastegated turbocharger, they’re controlled by vacuum rather than pressure. Controlling boost with a wastegate is easy and in that case I would agree that an electronic controller is the better option, but in our case, and the ZD30 Patrols VNT unit, this doesn’t apply.

The main reason we fit a Dawes TDi controller is to enable bypassing the ECU control solenoid after blocking the EGR. The Dawes valve does control boost well and many people use them with good results. It’s just something fairly new that not too many diesel mechanics may be familiar with unless they frequent the Patrol or VW forums. Initially the TDi valves were produced for TDi VW Golf and Jeda cars in the USA, but they are also ideal for the ZD30 Patrol with its VNT turbocharger.

[boots]

Hi Chaz . your second sentence ,bottom paragraph should read like this mate . The dawes valve does control boost EXCEPTIONALLY well and many people use them with FANTASTIC and AWESOME results . JMO . Thankyou for sharing your knowledge once again .

[Chaz]

Hi Chaz . your second sentence ,bottom paragraph should read like this mate . The dawes valve does control boost EXCEPTIONALLY well and many people use them with FANTASTIC and AWESOME results . JMO . Thankyou for sharing your knowledge once again .

Thanks mate, just being modest.
I've also come across a few that don't recomend them because they're not familiar with the Dawes valve. Initially we were looking at fitting a convenional wastgate turbo off a Navara to overcome the issues, but that would mean an exhaust dump change as well, so the cheaper option was the TDi Dawes valve which gives much the same results while retaining the original turbo and exhaust.
Cheers,

[mudski]

Sweet, Got my Provent from Ebay, needle valve from Dependable, dawes is ordered from 3bar, blue LED dash globes from Ebay and the boost/egt gauge from Mc.Nally's. Just gotta wait for the last two to get here now. O.h and the EGR plate is ordered too

[Ben81C]

Ben81C,

It sounds like none of your mechanic mates or diesel specialist are familiar with the VNT controlled turbochargers used in almost all late model diesel cars. Variable nozzle turbochargers don’t use or have a wastegate and unlike a conventional wastegated turbocharger, they’re controlled by vacuum rather than pressure. Controlling boost with a wastegate is easy and in that case I would agree that an electronic controller is the better option, but in our case, and the ZD30 Patrols VNT unit, this doesn’t apply.

The main reason we fit a Dawes TDi controller is to enable bypassing the ECU control solenoid after blocking the EGR. The Dawes valve does control boost well and many people use them with good results. It’s just something fairly new that not too many diesel mechanics may be familiar with unless they frequent the Patrol or VW forums. Initially the TDi valves were produced for TDi VW Golf and Jeda cars in the USA, but they are also ideal for the ZD30 Patrol with its VNT turbocharger.

Ah that is the missing info from the set up and explain diagram everybody has missed and why every one has been scratching their heads, this has cleared the air well and truly. Its easy to make decisions when you have the whole story and have a clear idea of how things work. Great explanation and thank you for filling in the blanks Chaz. I will get one ordered ASAP. Thank you all.