Positive Crankcase Ventilation (PCV)


I've noticed the rubber pipe from the rocker cover to the intake manifold before, and haven't thought much about it, but I was reading of some problems with EGR systems, and to be they look similar. EGR results in reduced performance in exchange for less emissions, but does PCV have the same effect on the daihatsu engine? The crankcase gases arn't going to be improving performance, but do you think they are having a noticeable effect? On all the lorries I work on the crankcase breather just ends at the sump and blows the gas into the air. Can you think of any reason why doing this to the daihatsu engine would cause any trouble? You would have to block the hole in the intake manifold obviously. I am thinking of doing it because I'm not to hot about exhaust gases and oil going straight into the intake, for the sake of the planet.
Apperently on the Turbo engine the breather goes between the intercooler and turbo.


PCV has many benefits and

PCV has many benefits and negatives which are complex to enter into on a site such as this.

You are correct in your theory of trading power and emissions, but this pressure also removes many of the fumes through filtration. They circulate the residues from oil and other contaminants around the engine, this absorbs heat and destroys a lot of the emissions internally.

This also gives a negative opposition pressure to moving pistons, it effectively damps them slightly as they move down the bore. This dampening effect, although small, reduces piston shock loads and wear.

Lorry engines are not true lorry engines, they are usually designed as a "one application" engine. Fundamentally it means the same engine might be marinised for marine applications, or used as a static application such as generators or air compressors.

Lorry engines are not designed for power, they are designed for torque; this means they do not suffer in the same manner as those high speed diesel engines. Their low revving design naturally reduces shock loadings on pistons as combustion is much slower and consistent. It is the high speed engines whose pistons suddenly change direction as they reach the bottom of the stroke and change direction to return up the bore.

Such modern "one application" designs mean the engines in lorries are now so much more robust as they have to withstand all these applications and remain reliable.

The Fourtrak engine isn't

The Fourtrak engine isn't really much higher reving than a typical lorry engine, does anyone drive there Daihatsu above 2,000rpm? The only time mine goes about 2,000rpm is on the motorway, and only above 3,000rpm at the MOT smoke test.
I might have to do this for the MOT regardless, because I am perilously close to failing the smoke test already!

Mine runs to the max rpm limit

Hi Stalin.

I quite often run my Fourtrack well over 2000 rpm, the turbo kicks in at/around 2200 RPM. Today did a constant motorway run at pedal to the metal MPH and and the only needle I watch is the temp ( and RR's were just passing at just under a ton). Folks get a bit put out when an old Fourtrak pulls out and passes them !!! Mot due tommorow, be interesting to see smoke test as last one was .8, limit 3.0. Not bad for an old truck !!!!

Edward (ews) '92 Fourtrak 2.8 TDX

Mine is the non-turbo, hence

Mine is the non-turbo, hence the low revs. Whats the highest speed you've managed to get out of your Fourtrak Ewes?

.8, wow. I got 1.35 out of 1.5 last MOT!

Smoke test resut

Hi Stalin.

Chunky passed the MOT and the smoke test, result using the Fast Pass criteria/level (1.10. test limit 1.50) a single max exceleration of engine, different from last year where a number of engine excelerations were used to obtain an average (.8 max limit 3.00)

Fast Pass
Following the meter prompts, depress the accelerator pedal quickly and continuously but not violently, to reach full fuel position in less than 1 second
Hold it there until a release prompt is given, then immediately release the pedal. Allow the engine, and any turbocharger fitted, to return to idle speed
At the end of the 1 st acceleration read the smoke level displayed on the meter. If it is at or below 1.50m-1 the vehicle has passed this part of the test and a pass result will be displayed on the meter.

If the mean smoke level is too high, carry out further accelerations up to a maximum of 6 in total

2. After 6 free accelerations, the mean of the last 3 smoke levels is:

a. for a non-turbocharged engine, more than 2.50m-1 (fail)

b. for turbocharged engines more than 3.00m-1 (fail)

Max constant speed run over a measured flat distance,using a sat nav/gps unit, 89.6mph, speedometer aprox 90mph. Needed addition of cabin heater on full blast to keep water temp under critical at end of run, when reducing speed.

Edward (ews) '92 Fourtrak 2.8 TDX

Daihatsu has a habit of

Daihatsu has a habit of installing the crankcase ventilation jet (U.S.) or restriction within the rubber hose. When these rubber hoses get replaced by mechanics who are not Daihatsu schooled, they are unlikely to be aware that these jets are hidden within these hoses. This could lead to higher oil consumption and power loss resulting from lowered manifold vacuum typical of a vacuum leak. The following images concern the Cuores and MOVEs which could also apply to other models: