oil catch tank

[H3nrY]

Hi all

Is an oil catch tank needed in a z-car ? I´ve browed the web but have not found a conclusive answer.

Hendrik

 

[Rob Gaskin]

I've got a simple one linked to the cam cover and crankcase breather. It tends to be more condensation that accumulates rather than any oil but I'd rather have it than fancy little filters.

 

[Mr.F]

A catch tank would be required for open breathers by many race car regulations.
The standard Z system is a closed PCV system so no need for any additional catch cans as emissions from rocker box and crankcase are directed back into the engine.

 

[johnymd]

The standard Z system is a closed PCV system so no need for any additional catch cans as emissions from rocker box and crankcase are directed back into the engine.

I wonder how many still have this system in place. Mine had an open pipe on the crankcase and a little filter on the rocker cover, obviously not the correct way of doing things.

 

[STEVE BURNS]

did not John foreman make a few of them

 

[Mr.F]

open pipe on the crankcase and a little filter on the rocker cover

It is common practice on road-going carburetted Zs to use the little filters - ideally one on the crankcase breather as well, and I supply them on a regular basis. The PCV valve on the manifold gets blocked off and the cars seem to run just fine.

Do the same thing on a 280ZX and the engine starts to run rough at idle.

PCV systems are about emissions - older cars simply didn't have anything and vented the dirty gases to atmosphere.

For race cars, the potential for oil emerging from an open tube onto the track is prevented by insisting on a catch can for all emerging vapours.

Commonly on high performance V8s (and at least one L-series on this forum), rocker covers can be connected to an exhaust collector valve which provides a scourging action as the exhaust gases roar past, drawing upper crankcase vapours out with it. The projected reduction in pressure in the upper part of the engine is supposed to give a small bhp increase.
This system has been further developed on top end drag cars which now use a virtually frictionless, engine driven pump to draw gases out of the rocker, resulting in significant horsepower gains! I have seen talk of implementing this on high horsepower turbo cars where ring blow-by may be significantly increased...

 

[Ian Patmore]

(and at least one L-series on this forum),

That will be me then

Have seen the crankcase breather connected to the intake manifold (esp. on turbo L series's)

 

[SKiddell]

Commonly on high performance V8s (and at least one L-series on this forum), rocker covers can be connected to an exhaust collector valve which provides a scourging action as the exhaust gases roar past, drawing upper crankcase vapours out with it. The projected reduction in pressure in the upper part of the engine is supposed to give a small bhp increase.

But at the possible loss of some cylinder scavenging (if done wrong) as your losing some of the exhausts ability to draw residual waste gas (and the fresh incoming charge) out of/into the cylinder.

 

[rallymanDP]

My, oh my, Steve, you have aged a lot recently - your hair is so white these days !

( Better get a more flattering Passport photo done soon....)

 

[SKiddell]

Sorry can't help it Duncan
Emmet Brown (Christopher Lloyd) is one of my all time favorite characters and the back to the future films are just ace

88 miles an hour Marty

 

[rallymanDP]

He looks just like I feel, at times.....

Now I think about it, more & more often, too....

 

[Ian Patmore]

But at the possible loss of some cylinder scavenging (if done wrong) as your losing some of the exhausts ability to draw residual waste gas (and the fresh incoming charge) out of/into the cylinder)

Generally for all
..but if done right...and gains you hp, there can't be any detrimental effect on your gas flow. There are some factors that are more important to gas flow than this (which some people don't follow).
Just sticking a filter over the crankcase breather does...? Does not help with potential piston ring blow by (loosing hp and burning oil) or removal of condensation and oil vapour thats for sure. As the piston come down, it has "resistance" to the air below it, and some air may want to come by the piston rings- causing a gap. By removing the "resistance" by creating a vacuum, piston ring better seal. I have even found a filter on the crankcase breather fitted by an "expert" that basicly blocked the pipe off on someone elses engine.... On racing regulations, the crankcase breather can't be open, have you seen the oil/water/crud that collects in a catch can. Just 'cos it works, does not it mean it is always the best solution.

Have seen oil dripping out of the filter on the crankcase breather before, and engine bays covered in a film of oil.. The OEM system had the crankcase breather connected (to inlet- working on same principle) and all modern cars have some sort of system PCV, system. Can't be a bad thing to have something akin back on the engine system for performance and cleaniness.

 

[zbloke]

Ian,

Have you had your car dyno'd with and without the breather connected to the exhaust collector, and if you have did you see any horsepower gains or losses?

 

[SKiddell]

Generally for all
There are some factors that are more important to gas flow than this

Sorry Ian, I don't follow
Gas flow is very important and as such so is scavenging, its a fundimental part of how a performance engine works, thats not just the world accoring to Skiddy, thats a fact.
Lose scavenging and you have a polluted chamber prior to filling, polluted part burnt mix and fresh mix = loss in power.

As the piston come down, it has "resistance" to the air below it

One could counter "no it doesnt as its balanced out by the others going up, which are in turn are hindered by the compression cycle, which in turn are balanced out by the combustion cycle"....so on and so forth

By removing the "resistance" by creating a vacuum, piston ring better seal

you could argue that you could make ring seal worse by dragging combustion gases past them with your "Vacuum"

You could also argue that a crank case vacuum will induce a drag on an upward bound piston.

On a well built engine with a clean mesh (at the back of the crank vent), well machined and honed bores, quality rings and a good builder you will see few emisssions from the vent anyway, with regards to race regs, the reason its sometimes fed to a catch tank is that under certain conditions (such as an engine blow out) you can get a smog of oil pouring out and race officials dont want that all over their nice clean track, or indeed catching fire......be interesting to see that go through your exhaust system

On your photos it looks like your system is connected to the number six exhaust primary
Its worth mentioning that the L series isnt a closed crankcase system, the crank case and rocker cover are" connected" by the front cover and the rear oil way so any pressure differential applied to the sump will apply to the rocker cover cavity and where's your rocker cover vent connected to ???

Please don't take this as negative
I really want to understand this and on a big power V8, with and external vaccuum source there is some logic but more to do with reducing the turbulane than anything else much like a crank scraper does but were talking many hundred HP race engines here that have a very different layout so you can't automatically apply the same logic.