mgbsr20det

Hi all , I recently had my car dynoed it’s a MGB with a S13 SR20det.



Stock motor

740 nizmos

GT2871r

FMIC

Nistune

Etc.



I didn’t have a catch can so the tuner didn’t want to up the boost as at over 11psi it was getting some blow by and venting out the rocker cover t piece hole straight towards the turbo. So he left it on 11psi and advised me to get a catch can setup then come back for more boost .



I’m in the process of getting all the parts to install a catch can now.



My question is: is this blow by standard and ok or is my motor a bit tired

It looked to be just puff of blackish smoke there was no oil residue and I have driven it hard on the street and there is no sign or oil coming out and obviously can’t see it on the street to know if it is still happening except for the fact that their is no mess in the engine bay or under bonnet.



Thanks steve

mgbsr20det

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jedi03

that is awesome! these motors have pretty decent blowby, using the s14 modified to fit s13 valve cover helps a lot...by chance you have a build sheet/how you installed it? my uncle has one of these stock that he gave up looking for an engine for it..may be next on the to do list lol!

TheRealSy90

Yeah the hole on the exhaust side of the valvecover shouldn't be just open to the atmosphere.

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jedi03

i personally retained the OE catch can to the T then routed the other side to a Cusco style catch can with routes to the intake...I was getting to much internal pressure without the extra vacuum source so kept blowing front main...thought had cracked the crank dampener or the crank for a while lol, was nice to find was "easy" fix!

Kingtal0n

0. compression test, use a decimal place, use two different compression testers (one is always bad)

1. Connect the factory PCV system and use a high quality PAPER AIR FILTER
Replace the PCV valve


2. boost leak test, pressurize from compressor cover all the way to intake manifold
it should hold 20psi for a 'while' (20-30 seconds easy)
fix all boost leaks

If it still blows oil
3. remove valve cover and inspect the baffle for sludge/carbon buildup, fully clean it out using solvent
4. leak down test to ensure rings/valve are good enough

It won't blow oil anymore if this is all done properly, unless boost/power exceeds some threshold (say 26psi and 500rwhp)
even engines with 120psi compression across the board won't blow oil using the proper factory PCV and paper air filter element

The key is pulling suction on the crankcase during WOT and this is only achievable if you are using the proper air filter element (usually a PAPER) and PCV crankcase tube applied to the valve cover baffle.

TheRealSy90

On your illustration, the turbo is blowing air into the crank case lol.

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S14rebuild

No its not.... either suction on the air filter side and other side has a pcv valve...soooo

mgbsr20det

Thanks for your Input it’s very appreciated. My tuner recommended a vented catch can set up

remove PCV valve and go to Catch can

Rocker t piece to catch can

Crank case to catch can


What’s your thoughts on this setup please

We are planning on upping the boost to 18 psi so he doesn’t want to re-circulate back into the intake





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S14rebuild

I run all valve cover ports to a large vented catch can. No pcv valve...i get ALOT of blow by. My catch can vent even smokes... i was concerned so i checked compression 150 across the board, so i dont worry. I have no issuse running catch can like how u stated

mgbsr20det

Did you also remove your PCV valve and go straight to catch can. I’ve done a lot of searching and many people are saying it should be under vacuum to extract the gases that is why they run it to the intake. My thoughts on it been on the vacuum is would it then affect the maf flow sensor readings as the Motor technically is getting more air than what the maf is reading.


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TheRealSy90

Hey I was just going off the drawing where the blue arrows coming from the the turbo intake into the crank case are pointing INTO the crank case and not out. Splitting hairs.

You don't want nor need a vented catch can.
SR20's want a vacuum source to the crank case. It will make more power and run much smoother.

That boost pressure really doesn't matter since you would have a catch can in between the turbo intake to valve cover hose.

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Kingtal0n

Don't ever use a catch can unless the engine is already blown and you just need to drive it for a little bit until you can afford to replace the engine

Also never vent the crankcase using a breather. Never use a breather anywhere- the only 'breather' should be the actual air filter on the turbo inlet tube as shown in my posted picture. Crankcase needs to be fully sealed and pressure tested for pcv to work properly.

The picture I posted is showing the intake manifold applying suction to the crankcase, and the crankcase receiving its fresh air supply from the engine's air filter- exactly as it comes from the factory OEM. Sorry if its a bit confusing, I neglected to draw the throttle body and pressure ranges, perhaps I will make a new picture some day.
nevertheless, This is an OEM configuration I have shown

The OEM pcv will work until around 500rwhp maybe 600~ at which point it will still work but needs a slight upgrade depending on how loose the piston/wall clearance is, what type of ring is used, what sort of oil pump, how much actual boost is needed to hit that number, etc... and honestly at 2L with that kind of power I'd recommend a dry sump and vacuum pump anyways.

Wookie384

I'm curious on your logic of why a catch can should never be used as the PCV system on most cars are designed to meet emissions regulations, and performance was not included in that design. It's such an issue that most "modern" cars have excessive blow by when driven aggressively.

mgbsr20det

I ended up doing it this way, as per my tuners advice. I’m happy with the result. now I can get it back onto the Dyno for more boost




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S14rebuild

Do u get any vapor coming from the breather on the catch can, when running/idling?


How about at idle, when oil cap is removed do u get and blowby, pressure out the valve cover?

mgbsr20det

No not at all , just a little puff on the dyno that time. It spitting oil or anything like that it was more of a steam puff


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TheRealSy90

So again you're not drawing any vacuum to the crank case... You're leaving power on the table as well as a smoother running engine.

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S14rebuild

Ive been running a catch can setup as the op has for YEARS. never knew it was wrong. Never had an issuse. Now im advised to change it up, i will do so and see how all goes

mgbsr20det

Hi guys , I have a question .
With the pics above of my catch can setup as a reference . Can i remove the filter and cap it off like I did for one of the filters already and then run a third hose to my turbo intake pipe So then both hoses from rocker cover go to catch can and then single hose to intake , will this create enough vacuum through the rocker cover ? Just trying to delete the PCV as I’ll be adding more boost very soon and hear many issues about boost leaking through the PCV .

Another reason why I now want to plumb it back into the intake is my car is a MGB roadster (convertible) , I have blocked up as many firewall holes as I can but still get stinky engine smell and would like to eliminate the smells as much as possible . If this means putting PCV back in I would do it as long as it doesn’t cause boost leak issues .

Thanks


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S14rebuild

It Needs a steady vacuum...

mgbsr20det

Ok so I had a dig around in my spares and found some hose and fittings to connect the PCV to the intake plenum, I had to reduce the hose size from the PCV hose size to 6mm hose to use one of the spare plenum vacuum lines (I’ll get a bigger barb fitting and run the correct size all the way once I get a chance to pickup the parts) . I went for a drive just now and I will say it does help reduce the smells so now I’m definitely thinking about changing the other side by blanking off the filter and running a 10an hose to the turbo intake to get the best of both worlds off boost and on boost.



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jedi03

that looks like a good idea to me...doing another line to drain the oil from the catch can would make it nearly maintenance free [email protected] Subaru's aftermarket uses an AOS which operates like this! And am also advised many other companies (porshe, audi etc) use it from factory