Installing Pyro and Boost gauges in a GU

[Leighw85]

Adjusted my Needle Valve so i get about 10psi @ 2000rpm with the foot down a little bit
Do i leave my Dawes @ 15psi? because if its set to 15psi i cant get to the 18psi @ 4000rpm can i. Which is suggested on your write up.

[Chaz]

Yes, it should still go to 18 at full throttle unless your transmission can't provide the engine load. Leave the Dawes set at 15psi as recommended with part throttle and some load.

What happens is that the Dawes valve will let some boost pressure into the vacuum side to control and maintain a 15psi limit up to a point. Then at higher rpm (usually above 3500rpm) the exhaust gas velocity will continue to increase the turbine speed even though the Dawes valve will hold the turbo actuator arm down and boost will rise above the set limit. You should see it increase to around 16psi at 3600rpm and go up to 18psi at 4000rpm, but this will only happen at full throttle. If yours doesn’t get up to 18psi, I wouldn’t worry about it because it’s only due to the fact that your car is an auto and the engine isn’t seeing enough load. A manual transmission car or an auto with manual converter lock will do it every time.

We set it up this way because during dyno testing, we didn’t make any more power above 16psi and the ZD30 makes its maximum power at 3600rpm. Running 18psi at 4000rpm is a very safe and conservative limit for an engine with a 17:1 compression ratio, so this all works out well for engine longevity and performance. The fact that Nissan set up the system to run much higher boost, is purely for improved emissions.

[Leighw85]

Ok so what do you mean by load?
When im taking of from lights or so on, I get higher boost that when cruising. Sometimes it rises about the 10psi @ 2000rpm.
but when cruising @ 2000rpm for example ill get about 6-7psi at times.

Ok leaving my Dawes set at 15psi then, i have not seen it exceed that except for a small spike up to about 17psi for a second or so.

[Chaz]

Ok so what do you mean by load?
When im taking of from lights or so on, I get higher boost that when cruising. Sometimes it rises about the 10psi @ 2000rpm.
but when cruising @ 2000rpm for example ill get about 6-7psi at times.

Ok leaving my Dawes set at 15psi then, i have not seen it exceed that except for a small spike up to about 17psi for a second or so.

Load is when the engine is working, like when you take off. When you cruise, there isn’t much load, hence lower boost and lower EGT’s. When the engine is under load, eg taking off, accelerating up hill or just a heavy throttle, you should have your 15psi. If you back off the throttle, your boost should drop down to almost nothing.

Your EGT’s will only rise to high levels if the load is high enough, so that’s where you want to make good boost to keep the EGT’s down. When you cruise and boost is down, there isn’t much load so EGT’s and fuel consumption drops.

[Leighw85]

So everything i have said is ok and not abnormal?

[Chaz]

So everything i have said is ok and not abnormal?

Yep, it sounds like you have done it right.
I would just drive it for a while and see how it goes. If you have any problems, you may need to do some fine tuning, but otherwise keep an eye on your EGT’s and enjoy. You shouldn't need to watch the boost closely unless your EGT's start to run abnormally high.

[Leighw85]

your a legend mate.
All your help has been awesome
cheers

[Arwon]

Sent from my iPhone. Please excuse the spelling.

[Chaz]

your a legend mate.
All your help has been awesome
cheers

My pleasure.

Hopefully this will help others contemplating these mods or to understand how and why it’s done also.

Cheers,