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Tips on Oil Restrictors

Posted: Sun Jun 30, 2019 8:52 pm
by BattleGarage_RS
Hey Guys,

I have a moderately high performance engine we are working on that seems to not have any of the 16V oiling issues handled.

For a mostly street driven car with an occasional track day on a Hankook RS4 or similar tire, would just installing an oil restrictor to the head be enough?

Is anyone selling these restrictors? What's an ideal size? Are these typically pressed in?

Thank you in advance!

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Re: Tips on Oil Restrictors

Posted: Mon Jul 01, 2019 2:14 pm
by oldeskewltoy
https://ae86world.bigcartel.com/product ... essure-kit - typically either pressed, or even "hammered" into place.

In my opinion... the oil pressure up kit, and having a large enough oil supply should be enough in most situations. Additionally, oil packing in the head is often remedied by adding an intake side oil drain at the back of the head.

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Re: Tips on Oil Restrictors

Posted: Mon Jul 01, 2019 3:08 pm
by sirdeuce
3/8" NPT on that? -8 flare?

Re: Tips on Oil Restrictors

Posted: Mon Jul 01, 2019 8:17 pm
by UNLIMITED 86
In my opinion... the oil pressure up kit is a bandaid fix and could possibly contribute to the problem...

If excess oil is being supplied to the head to the point it begins to pool, resizing the orifice to limit that flow is the ideal fix. You will still have adequate oil supply and reduce the volume of oil needed to drain.

In general, you want to avoid this orifice from having a greater restriction than what's down stream.

If you decide to press it in, I would take it to a machine shop and ask them what size plug you need for an interference fit.

Honda guys used to do something similar for LS-vtec builds. They would tap the hole, then thread in an NPT plug into it. I dont see why you couldn't do the same with the 4ag (orifice drilled into the plug).

Whatever you do, DO NOT "hammer" it in! The potential to cause damage is too high (especially if you're a 400lb gorilla!).

Re: Tips on Oil Restrictors

Posted: Mon Jul 01, 2019 11:35 pm
by jinx
very same topic discussed with nissan CA18 and RB 6yl motors, especially for track & drifting
Long story short - Inadequate crankcase breathing hindered oil drainback. Correct the hose routing, problem solved
No additional/elaborate drain back or oil restrictor mods were required

Re: Tips on Oil Restrictors

Posted: Tue Jul 02, 2019 7:34 pm
by UNLIMITED 86
jinx wrote: Inadequate crankcase breathing hindered oil drainback.


This makes sense.

Re: Tips on Oil Restrictors

Posted: Wed Jul 03, 2019 8:36 pm
by sirdeuce
UNLIMITED 86 wrote:
jinx wrote: Inadequate crankcase breathing hindered oil drainback.


This makes sense.


Not really the case here. the late 4AGE, small port head, has a secondary oil return to make up for the inadequate oil return of the earlier models. It is a good size return, 5/8" I.D. planted in the head where OST had shown the AN fitting. The block has a tube pressed into the side and they are connected with a rubber hose. The engineers at Toyota/Yamaha recognized an issue and that was their remedy. Not saying increasing the crankcase venting would not help. could be the drain tube was sized to be a wet vent, 5/8" is quite large.

Re: Tips on Oil Restrictors

Posted: Wed Jul 03, 2019 8:37 pm
by sirdeuce
UNLIMITED 86 wrote:
jinx wrote: Inadequate crankcase breathing hindered oil drainback.


This makes sense.


Not really the case here. the late 4AGE, small port head, has a secondary oil return to make up for the inadequate oil return of the earlier models. It is a good size return, 5/8" I.D. planted in the head where OST had shown the AN fitting. The block has a tube pressed into the side and they are connected with a rubber hose. The engineers at Toyota/Yamaha recognized an issue and that was their remedy. Not saying increasing the crankcase venting would not help. could be the drain tube was sized to be a wet vent, 5/8" is quite large.

Re: Tips on Oil Restrictors

Posted: Wed Jul 03, 2019 8:37 pm
by sirdeuce
Why did that post twice???

Re: Tips on Oil Restrictors

Posted: Thu Jul 04, 2019 1:15 pm
by UNLIMITED 86
sirdeuce wrote:Not really the case here. the late 4AGE, small port head, has a secondary oil return to make up for the inadequate oil return of the earlier models. It is a good size return, 5/8" I.D. planted in the head where OST had shown the AN fitting. The block has a tube pressed into the side and they are connected with a rubber hose. The engineers at Toyota/Yamaha recognized an issue and that was their remedy. Not saying increasing the crankcase venting would not help. could be the drain tube was sized to be a wet vent, 5/8" is quite large.


I am fully aware of the external oil drain on the late model engines; however, fitting in the block is threaded, not pressed.

Also, I believe the external oil drain was also a bandaid fix. Oil pooling in early model 4ag's combined with hard left turns could actually cause oil to be drawn into the intake manifold (thru the valve cover breather port) and kill the engine. IIRC this is the issue the engineers were trying to solve.

Ive been thinking about this since reading Jinx's comment and am not sold that high crankcase pressure is the only issue. I remember reading that MotoIQ series and want to say the guy building it also built FA engines (which ran a dry sump oil system). Dry sump systems are capable of achieving a negative crankcase pressure. If they added the restrictor in addition to this, that suggests oil flow to the head is excessive.

Re: Tips on Oil Restrictors

Posted: Thu Jul 04, 2019 1:44 pm
by sirdeuce
I've had similar issues with a 20R in the past, oil pooling in the valve cover that is, and it produced a nasty oil cloud when it happened. For that problem I found refreshing the rocker assembly helped a lot, also increased the oil pressure since it wasn't bleeding off into the cam valley.
I'll be looking for a restrictor pill for my 7AGE when I assemble it. Never was a consideration. Thanks for opening this thread!

Re: Tips on Oil Restrictors

Posted: Thu Jul 04, 2019 5:07 pm
by jinx
Dry sump systems are capable of achieving a negative crankcase pressure. If they added the restrictor in addition to this, that suggests oil flow to the head is excessive.

factory oil pump & 8000rpm redline can't be compared to an elaborate dry sump & 9500+? rpm
Totally different operating parameters. Wouldn't be surprised if the restrictor was 'overwelmed' in the latter

Re: Tips on Oil Restrictors

Posted: Thu Jul 04, 2019 11:15 pm
by UNLIMITED 86
jinx wrote:factory oil pump & 8000rpm redline can't be compared to an elaborate dry sump & 9500+? rpm
Totally different operating parameters. Wouldn't be surprised if the restrictor was 'overwelmed' in the latter


Apples and oranges really.

For a factory oil pump, high RPM is probably the worst case scenario for us as it's possible for the manifold pressure to be higher than the crankcase pressure (if it were vented).

Drysump systems over scavenge the crankcase (with multiple pumps) to take advantage of decrease pressure. Swirl pots help separate the air/oil mixture so the outlet pump does not feed aerated oil.

Re: Tips on Oil Restrictors

Posted: Fri Jul 05, 2019 2:47 pm
by sirdeuce
UNLIMITED 86 wrote:
jinx wrote:factory oil pump & 8000rpm redline can't be compared to an elaborate dry sump & 9500+? rpm
Totally different operating parameters. Wouldn't be surprised if the restrictor was 'overwelmed' in the latter


Apples and oranges really.

For a factory oil pump, high RPM is probably the worst case scenario for us as it's possible for the manifold pressure to be higher than the crankcase pressure (if it were vented).

Drysump systems over scavenge the crankcase (with multiple pumps) to take advantage of decrease pressure. Swirl pots help separate the air/oil mixture so the outlet pump does not feed aerated oil.


Actually, the 4age crankcase is vented, something I learned recently, there is no PVC it's just vented outside of the manifold. Run some wire through the 'PVC' port and you'll find it just ports the crankcase to a spot just ahead of the throttle body. So manifold pressure won't have an affect on carnkcase pressure.

Re: Tips on Oil Restrictors

Posted: Sat Jul 06, 2019 11:09 pm
by jondee86
Some moderately relevant stuff in this thread... http://forum.diyefi.org/viewtopic.php?f=15&t=2702
and worth a read :)

Cheers... jondee86

Re: Tips on Oil Restrictors

Posted: Tue Jul 09, 2019 8:53 am
by UNLIMITED 86
sirdeuce wrote:
Actually, the 4age crankcase is vented, something I learned recently, there is no PVC it's just vented outside of the manifold. Run some wire through the 'PVC' port and you'll find it just ports the crankcase to a spot just ahead of the throttle body. So manifold pressure won't have an affect on carnkcase pressure.


My previous post was not completely accurate due to my lack of proofreading after changing my wording.

The 4AGE has a positive crankcase ventilation system; however, it lacks a PCV valve which are only designed to vent the crankcase at lower RPM (when manifold pressure is low). Manifold pressure increases with RPM and can be higher than crankcase pressure at higher RPMs- the purpose of the PCV valve is to prevents this.

The breather port on the valve cover is connected to the intake manifold, which draws in the blow-by gas from to crankcase, and mixes it with fresh air to be burned in the next combustion cycle.

Re: Tips on Oil Restrictors

Posted: Tue Jul 09, 2019 11:49 am
by sirdeuce
Sorry to burst your bubble, but that's not the way it works on a 4AGE. I actually thought it was that way too, until someone (jondee) posted otherwise. If the crankcase were a positive vent, manifold vacuum, without an operational valve the engine would not idle. Every time the throttle would close vacuum would have to build up in the crankcase as well as the manifold before the engine could idle. That would either cause a lean condition, unregulated air, or high rpm operation with a closed throttle. The hose from the valve cover to the manifold is just to route the crankcase gasses to the intake tract so it can be burned. Emissions controls y'know. I actually did a post like yours once and got smacked in the back of the head with a little reality check that a 4AGE is simply vented and not positively vented.
Revisit the part of my post you quoted and try again. I'm not flaming, just trying to pry your eyes open(ok that was a little flame there).


if you don't believe it, try running your engine without that little hose.

Re: Tips on Oil Restrictors

Posted: Tue Jul 09, 2019 5:01 pm
by jondee86
Getting a bit off topic so I added an edit to this post...
viewtopic.php?f=9&t=12011

Cheers... jondee86

Re: Tips on Oil Restrictors

Posted: Tue Jul 09, 2019 7:26 pm
by sirdeuce
jondee86 wrote:Getting a bit off topic so I added an edit to this post...
viewtopic.php?f=9&t=12011

Cheers... jondee86


Nice one! Clarity incarnate.