Moss supercharger question

[DaveAhrendt]

I'm about to throw in the towel on my Shorrock supercharger install. I'm convinced that there is a
fundamental internal issue that I don't feel like dealing with at this time.

With my mostly non-functional Moss rear seal I've got to run a PCV system in any hope of keeping oil in the engine.
So, my question is whether there is a vacuum source port between the carb and blower on the Moss unit?
There is a picture in the install instructions that appears to show a capped port where a vacuum tap would be but
it's not referenced in the instructions. Given it comes with a warranty I don't want to make any changes to it.

Any Moss supercharger owners care to chime in?

Thanks,
Dave

[Ray White]

I'm about to throw in the towel on my Shorrock supercharger install. I'm convinced that there is a
fundamental internal issue that I don't feel like dealing with at this time.

With my mostly non-functional Moss rear seal I've got to run a PCV system in any hope of keeping oil in the engine.
So, my question is whether there is a vacuum source port between the carb and blower on the Moss unit?
There is a picture in the install instructions that appears to show a capped port where a vacuum tap would be but
it's not referenced in the instructions. Given it comes with a warranty I don't want to make any changes to it.

Any Moss supercharger owners care to chime in?

Thanks,
Dave

Hello Dave. I thought about fitting a PCV when rebuilding my engine with Eaton M45 supercharger but when researching the subject I found that there is a fundamental conflict in the inlet manifold between the vacuum caused by the PCV and the pressurised system of a blower. This can be overcome but it is quite complicated.

In the end I opted for crankcase ventilation powered by the exhaust. In an exhaust evacuation system, a scavenger unit in the front pipe draws the fumes out via a tube connected to the rocker cover (or valve cover if preferred) and any surplus oil is collected by a catch can. This also eliminates the need for the (environmentally damaging) draught tube.

https://www.superchargerforums.com/thre ... lown.2472/


P.S. I have yet to try out the system but others have reported success.

Ray.

[DaveAhrendt]

Hi Ray,

Thanks for the info. I have tried twice to use an exhaust extractor with no luck. The unit I tried is:
https://antisplataero.com/products/cran ... t-complete but I think they are all the same. I can't determine
whether it's the small diameter of the TC exhaust, the flex section or it's overall shape that causes it not to work. In both tests I ran
multiple miles with a MagneHelic pressure gauge plumbed into the dipstick hole. At idle I could see a modest
5-6 inches of water column negative pressure but at any acceleration or constant driving I would see a positive pressure.

I've had a conversation with Archie McCalister in TN about this. He has been very successful with his TF. In the course
of the thread on the MG Experience I never came across anyone using one on a TC. I really wish this had worked as it
is the easiest solution.

[Ray White]

Dave, that is worrying for me as I have also followed Archie McAllister's success story with his TF which, as it is also an XPAG engine, I would have thought a similar set up would be O.K. in a TC.

I can only imagine your blow by must be too much for the system to handle or your non return valve spring is too strong.

As you can see from the attached link to TT2 I have cobbled together my own version. I am now worried that it won't work as intended.

https://ttypes.org/crankcase-pressure-evacuation/

[DaveAhrendt]

Hi Ray,
I just read your write-up - nicely done! My arrangement was different in that I had the extractor plumbed to the oil catch can and from there to an adjustable PCV device installed in the road tube. Before trying the extractor I had the catch can running to a center tap on the intake manifold. Running to the intake via a PCV worked well other than fiddling to find a balance between working vacuum and a reasonable idle.

I see that you ran right from the extractor to the catch can and then to the valve cover without a PCV device. Maybe that's the answer. I also have the extractor mounted just behind the downpipes' bend to the rear just in front of the tab to bolt to the bell housing. I looks like you have it mounted to the rear of the flexible section. Of course, the TD/F don't have this flex section and maybe that disturbs the air flow.

I need to go back and re-read the original thread and see if Archie used a PCV.