Thread: 4BD1 Provent Install

Originally Posted by Dougal

Your t28? What's it from?

SR20DET / S14 Silvia (I feel like I should be talking text-speak and wearing my jeans lower when I say that )

Originally Posted by Bush65

The 4BD1-T doesn't have the breather on the tappet chamber cover. Only the one from the rocker cover.

But the rocker cover is different - I don't know if the oil separator inside the rocker cover is the same. And the 4BD1-T has a cyclonic separator, which drains oil back to the engine and vents to atmosphere (not legal now).

I agree with what rar110 posted, except for the description of the turbo oil drain on a 4BD1-T - I have probably misunderstood what he meant. The drain tube bolts to the side of the crankcase casting.

Thanks John. You mean they don't have the side-cover vent? Interesting...

As I have posted elsewhere - an oil-mist cyclone is about 50% efficient (mass-based). The provent should be 90-99%. You could vent the existing cyclone into the intake like on a Tdi, but then you would have the same oily intercooler and sooty turbo problems they have...

Originally Posted by isuzurover

SR20DET / S14 Silvia (I feel like I should be talking text-speak and wearing my jeans lower when I say that )

Yeah I bought my current T25 from a ricer-boy too.

Originally Posted by isuzurover

Thanks John. You mean they don't have the side-cover vent? Interesting...

As I have posted elsewhere - an oil-mist cyclone is about 50% efficient (mass-based). The provent should be 90-99%. You could vent the existing cyclone into the intake like on a Tdi, but then you would have the same oily intercooler and sooty turbo problems they have...

My original 4BD1T mist seperator was crap, the intake pipe blew onto a plate, the plate extended most of the way down to the drain. The blowby exit tube extended up to almost the top of the can.
I made a new one which is a cyclone (kind of 2 stage) and it's much better, but I still get enough oil mist to make sure my intake pipes never rust.

I'll stump up for a provent one-day. My rangie is playing garage ornament at the moment.

Hi John. I was trying to describe what was in that photo you sent me. I should just post it, bit tricky to describe. The plate is not really oval.

Thanks guys.

My 4BD1 block has a couple of posts where the 2 bolts go, but it looks like the area needs to be milled flat and a couple of threads tapped.

Originally Posted by rar110

Hi John. I was trying to describe what was in that photo you sent me. I should just post it, bit tricky to describe. The plate is not really oval...

I think I understand what you meant now.

The plate you referred to is the mounting flange on the drain pipe - it is part of the drain pipe.

Originally Posted by isuzurover

Thanks guys.

My 4BD1 block has a couple of posts where the 2 bolts go, but it looks like the area needs to be milled flat and a couple of threads tapped.

Yes, but I wouldn't go to that trouble. Just go into the cover plate over the oil pump drive.

Originally Posted by isuzurover

.... You mean they don't have the side-cover vent? ...

That's correct - only the one from the rocker cover.

Originally Posted by isuzurover

.... As I have posted elsewhere - an oil-mist cyclone is about 50% efficient (mass-based). The provent should be 90-99%. You could vent the existing cyclone into the intake like on a Tdi, but then you would have the same oily intercooler and sooty turbo problems they have...

I fully understand. I only intended to point out breather system differences between the 4BD1 and 4BD1-T and thought it relevant to include the oil separator.

I will replace the Isuzu separator on my 4BD1-T with a Provent. Before I was aware of Provents, I was intending to fit a 2nd separator after the Isuzu separator, so that I could connect the vent to the turbo inlet (for engineering compliance).

Must be some minor variations between motors. Mine has the plate held in place by two bolts, just without the drain tube.