Stock M35 Boost

[m35stagea]

I see different boost readings thrown about deoending on model.

My question is how does the vq gauge over boost? Does the ecu pick up boost pressure from the manifold and control the solenoid to decrease boost? Because I want to put my ebc on. Im guessing bleeding the stock solenoid wont work?

[andy65b]

There seems to be 2 different boost levels. RS & RX seem to be about 12psi and ARX & Axis seem to be 13psi. This may be a perceived difference or even as a result of different gauges used but they are all pretty similar on the VQ25DET.

The boost pressure is measured from a line about 15cm short of the throttle body. The line is mounted straight to a boost measuring device that is connected to the ECU.

The ECU controls that the boots via a solenoid mounted on the passenger side of the intake plenum.

It is certainly possible to increase the boost on the car by either a manual blled valve or an EBC.

The questions to consider are: are you running stock turbo? (13psi on a ceramic turbine and ball bearing core is quite reasonable boost, too much more with out changes will shorten the life of the turbo)

Have you modified the turbo's oil line feed at the banjo bolt? (increase the hole to 2.5mm)

Have you removed the stock dump pipe? (very restrictive and massive cat and little benifit putting in more boost with the stock dump)

Have you increased the flow of the exhaust?

The stock intercooler will handle the flow but will not cool multiple hard accelerations on a hot day.

Hope that helps.

[m35stagea]

Thanks for the reply.

Hdi cooler fitted.

Kakimoto cat back on order

Getting scottys dump and front.

I was mainly looking for more stable boost. On my rb with hks 2530 (bb) and apexi avcr boost was very stable e

With little if any drop off at 18psi over the rev range.

M35 seems to lose too much in higher rpm.

Re: oil feed I eas always told bb turbos needed oil restrictiors in place or is the vq feed excessivley small?

[Brick]

Talk to Scotty about the boost actuator mod. I should fix the top end drop off for you

[scotty nm35]

Our engine has an overboost function, but it kicks in at around 22psi. There is no way the stock 7psi actuator would ever allow that, no matter how much bleeding. A boost controller would bump it up as a midrange spike, but as the manifold builds pressure it will simply blow the puck open.

I modify the stock actuators to allow much more clamping force on the puck, it should hold 15-17psi (depending on exhaust mods) with the factory bleed circuit removed. You can then bleed or control boost from there quite easily. I would suggest having at least a boost gauge to keep an eye on the boost as it is another level of protection gone. A hose popping off can ruin your day, it's happened to me.

The stock turbo will take it for a fair while if it's in good condition. I ran mine for 4 months at 19psi and 226kw on ethanol. Just making sure the block banjo restrictor is clean is a good idea, or drill it slightly. I would save the 2.5-3mm drill bit for when the inevitable bush core highflow goes in. I have seen 10 bar oil pressure which is quite high, so I changed my mind on opening the restrictor too much. (Garrett recommend a 1mm restrictor for anything above 6 bar.)