DerHase's 2019 GTI Rabbit Edition: HPDE shenanigans

[mrmatto]

Incredible work! Your engineering doc on the PCV system and theory is very interesting, as is your theory on the catch cans.

 

[mrmatto]

Another piece of info that may or may not incorporate into this discussion: I've noticed when I have a fresh oil change and the oil level is toward the upper end of the acceptable range (according to the dipstick), I'm more likely to have smoking and I'm more likely to get oil in the CC at autocross, and sometimes a lot of it. However, after the oil level has dropped slightly to the lower half of the acceptable range, I rarely get more than a few drops in the CC and don't have any smoking. So it would seem the oil level may somewhat contribute to the PCV getting overwhelmed and oil going past the bypass valve

 

[DerHase]

Another piece of info that may or may not incorporate into this discussion: I've noticed when I have a fresh oil change and the oil level is toward the upper end of the acceptable range (according to the dipstick), I'm more likely to have smoking and I'm more likely to get oil in the CC at autocross, and sometimes a lot of it. However, after the oil level has dropped slightly to the lower half of the acceptable range, I rarely get more than a few drops in the CC and don't have any smoking. So it would seem the oil level may somewhat contribute to the PCV getting overwhelmed and oil going past the bypass valve

Yeah, I think the oil sloshing in the pan essentially "covers" the opening in the bottom end where the coarse oil separator is, but with a constant volume of oil, it pushes a lot more higher up to the fine AOS to the point it gets overwhelmed.


To expand a bit more on why these MK8 differences are a huge step in the right direction:

Photo above is the MK7 valve, but for the purpose of this point it'll work for both MK7 and 8.

Under boost, the above path is taken and the MK7 PCV is pulling approx 2.0in-HG of vacuum at best.
When you let off the throttle, all the internal check valve change direction and the intake (blue path) is now drawing 2.5-3.0in-Hg (and potentially spikes a tiny bit more, but won't capture that measuring via the oil cap as the volume of the rest of the crankcase will "damp" any oscillations of the needle).

That increases the pressure differential on throttle lift-off, making it MORE likely for the bypass valve to open... at the same time you're transitioning to braking (and likely a turn on track/autocross course).

The MK8 PCV by comparison pulls approx 2.0in-Hg (or just a tiny bit less, maybe 1.7-1.9?) under boost, but the vacuum level actually drops to ~1.5in-Hg... which would decrease the pressure differential at the bypass valve and make it MORE likely to stay closed and force everything into the AOS rather than immediately spilling over to the other chambers of the PCV.

edit: And I actually just added the above point to the Google doc as well.

 

[MonkeyMD]

Not sure what to make of this, but ran a counter clockwise course that essentially only only had 1 right turn. Had just had an oil change so the oil was to the top of the dipstick. No smoke whatsoever. But on the clockwise course (different course), I can replicate smoking lap after lap.

And unrelated, but I definitely need an oil cooler. Got up to 284.

 

[mrmatto]

Not sure what to make of this, but ran a counter clockwise course that essentially only only had 1 right turn. Had just had an oil change so the oil was to the top of the dipstick. No smoke whatsoever. But on the clockwise course (different course), I can replicate smoking lap after lap.

And unrelated, but I definitely need an oil cooler. Got up to 284.

That all adds up honestly. Most of my smoking & power loss events have been fast straight + hard brake + right turn + back on full throttle. Only once did I have smoking with a left turn at autocross and it was a full 180*-plus turnaround after a hard brake from ~70mph.

RIP your oil tho

 

[DerHase]

Not sure what to make of this, but ran a counter clockwise course that essentially only only had 1 right turn. Had just had an oil change so the oil was to the top of the dipstick. No smoke whatsoever. But on the clockwise course (different course), I can replicate smoking lap after lap.

And unrelated, but I definitely need an oil cooler. Got up to 284.

Make sure to see how NOT to install an oil cooler (and make the car run worse) here:
https://www.golfmk7.com/forums/inde...a-golf-r-55f-over-ambient-with-apr-ic.426885/

That all adds up honestly. Most of my smoking & power loss events have been fast straight + hard brake + right turn + back on full throttle. Only once did I have smoking with a left turn at autocross and it was a full 180*-plus turnaround after a hard brake from ~70mph.

RIP your oil tho

Yeah, all of my really bad KR events have been following a RH turn. I am fully certain that the times it HAPPENED to be after a left turn... were strictly because all the oil that made it past the bypass valve just hadn't been burned up yet and it continued at that point. Turn 9 and 10 are not far apart at VIR.

Here's KR vs lat and long gs from all my sessions at VIR last time out:

Worst values seen:

Weighted averages:

Now it IS important to note: When KR gets logged, it jumps up to whatever the ECU deems necessary, then slowly replenishes back toward zero (unless knock events are still occurring, in which case it pulls even more timing). This only means that knock is being logged even after the wheel has turned straight again. BUT the trend where the PEAK numbers are occurring is absolutely indicative of where the KR starts to happen. These don't really illustrate that it's under braking, but that's because we're just sucking a pool of oil in under braking, but it's not really being burned at a fast rate until we're back on the throttle.

 

[tigeo]

That all adds up honestly. Most of my smoking & power loss events have been fast straight + hard brake + right turn + back on full throttle. Only once did I have smoking with a left turn at autocross and it was a full 180*-plus turnaround after a hard brake from ~70mph.

RIP your oil tho

That's when I had it at VIR....front straight ~130+mph...hard brake....turn 1 (right hander)....on the hammer....smoke.

 

[yakboyslim]

Unpopular opinion, but it also touches on why catch cans on these cars are all bullshit.



Edit: I also purchased another MK8 PCV valve to play around with off-car for further bullshittery, plus to have a spare just in case. Plus a buddy in the Simos Tools group is going to be kind enough to lend me an APR CC/plate kit to install on my car and get some numbers/data on it crankcase-pressure wise.

The theory on why CCs like BMS are a problem, and just how the smoke screen happens in general is very interesting. All of it matches the behavior of my car stock PCV, and stock with BMS CC.

I have the APR plate and can now. If you didn't want to swap to the APR etc, you could send me that oil fitting and gauge, I'd be happy to take some videos with it etc. Although, won't be apples to apples due to turbo difference.

 

[DerHase]

The theory on why CCs like BMS are a problem, and just how the smoke screen happens in general is very interesting. All of it matches the behavior of my car stock PCV, and stock with BMS CC.

I have the APR plate and can now. If you didn't want to swap to the APR etc, you could send me that oil fitting and gauge, I'd be happy to take some videos with it etc. Although, won't be apples to apples due to turbo difference.

Yeah man, more data the better. I'm going to be getting with @StorableComa real soon so that I can log a 5v signal from an extra MAP sensor and just data log everything direct in Simos Tools.

It's not a big deal to install the APR CC, and doing it on the same car is probably better from a control variable standpoint, but I can bring everything with me to Fastivus in September and you're welcome to borrow it and just mail it back when done.

 

[Mosquito]

The intake vacuum drain ports don't flow equally, much like the exhaust manifold ports.
Once oil has made it past the PCV seal, it initially drains mostly through the cavity of cylinder 4 before moving on to others. Much like fuel vapor from the charcoal canister favors cylinder 2 before moving on to 3.
On a high brake zone, you have a high peak of vacuum, draining fluid to a preferred chamber while turning right, giving the oil a nice further push to the left by X amount of Gs.

Short of flow balancing the ports, you lower vacuum draw and/or baffle chamber the vacuum port within the PCV prior to the check valve.

 

[MonkeyMD]

Worthy video

Great video. And apparently car owners brother was in the MK7 somewhat keeping up.

Don't know the outside temperature, but his oil temp never got above 230. You think he's got the right vent setup or it's just cool there, not the 105 it is here in Tejas

 

[DerHase]

Great video. And apparently car owners brother was in the MK7 somewhat keeping up.

Don't know the outside temperature, but his oil temp never got above 230. You think he's got the right vent setup or it's just cool there, not the 105 it is here in Tejas

The oil was over 270F - It's 133C towards the end of the lap.

 

[MonkeyMD]

The oil was over 270F - It's 133C towards the end of the lap.

Oh man. I thought I only saw 111.

Well nevermind then.

 

[DerHase]

Video of testing the MK8 PCV with the extra Tiguan hose uncapped/vented:

You'll notice it seems to struggle a bit more with staying out of positive crankcase pressure at part throttle accel/low boost situations than either of the other 2 configurations (MK7 and MK8 with extra hose capped).

Capping the hose is absolutely the way to go if run like this.

The original theory behind leaving it vented was to slow down the "rush" of air from going towards blue path vacuum port as you go from WOT to brakes... BUT since we found that the PCV actually pulls a weaker vacuum from the blue path as opposed to the TIP, I don't think this is actually necessary or desired - as the side effect as seen in the video is that it delays how quickly the TIP can start pulling a vacuum to counter blow-by. I don't think there's a *big* difference in overall vacuum once the turbo is spooled, but I'm sure it's there (however tiny it may be). The amount of vacuum pulled at idle is unaffected (or small enough it’s nearly immeasurable) either way because the vacuum source is the blue path, and it's just sucking through the giant TIP hose from the big tube that's at atmospheric pressure, another small "hole" isn't going to change the amount of vacuum in a real meaningful way IMO. @Mosquito can probably talk to these situations and differences from one setup to another more.


I did just place an order for some wiring/pins to add another MAP sensor which will be used to datalog crankcase pressure in real time on Simos Tools, rather than relying on my mechanical gauge and overlaying video. Putting squiggly lines together will be much better for a definitive analysis. While I probably won't run my home brew cap on track, I can also buy a sensor that goes to the new MK8 PCVs and log the pressure directly inside the valve as well with what I have planned. A GM 3 bar map sensor will likely be used to adapt to the cap location for non-MK8 valve testing (plus establishing how much of a difference there is from oil cap to inside PCV valve).


And video of my fastest auto-x run from Saturday. No knock!

 

[DerHase]

This should ruffle some feathers of catch-can sellers... but hopefully this helps some people out.

Also for further PCV talk (at least generally speaking, not specific to MY car alone), I decided to start a dedicated thread in the GTI engine sub-forum:
https://www.golfmk7.com/forums/inde...v-and-why-catch-cans-are-bullshit-imo.429130/