Sam James cowl/plenum question

Bevan · #1 03-06-2008, 10:50 PM

Has anyone installed a SJ plenum and used the standard Vans cowl and would like to share a few details...

A) Did you use the round inlet rings and if so, perhaps you could describe the best method to graft them to the Vans cowl?

B) If you did not use the inlet rings, but kept the inlets stock, how does it perform for cooling especially in extended climbs. Did you reduce the size of the rectangular inlets?

C) Do you feel there is a reduction in drag with your particular setup?

D) If you used the SJ cowl and plenum, could you comment on the use of the required prop extension, cooling and overall performance?

Feel free to elaborate and post as many of the specific particulars of your configuration as you can think of.

Thanks

Bevan
RV7A wiring

glenmthompson · #2 03-06-2008, 11:23 PM

Installed SJ plenum (tons of work) in a stock "6" cowl. I rounded the stock inlets and installed custom round ringed inlets. Looked kind of flat to me. Not one knot gained in speed, but temps dropped 20 deg on average. Also hard to install top cowl.. Plane was damaged, and "Heliojoe" now owns the project..I am sure he would send pics and his opinion on how it looks.. Glen

Plane krazy · #3 03-07-2008, 06:05 AM

I installed the james plenum using the stock vans cowl about 40 hours work but fits great with no issues

What have i gained

1 looks great
2 temps are much lower had higher then i would have like temps on #4 cyl before

3 gained about 75 rpms

4 gained about 5 knots strait and level

5 gained nothing in climb

ken in maine

db8 · #4 03-23-2009, 07:40 PM

Does anybody have any pictures (prefer RV-8 but any will work) of the standard RV cowl converted to Sam James' rings? I am looking at doing this but need more info and pictures. Comments are welcome too. Thank you. Dave

hydroguy2 · #5 03-23-2009, 08:00 PM

Here's a pic of an RV-7 built by "Yakdriver". He grafted Sam James rings into the factory Vans Cowl.

Capflyer · #6 03-24-2009, 04:53 AM

I retrofitted the plenum and modified my cowling. Temps dropped about 10 deg and there was no increase in speed. I would not do it again. Was expensive, a lot of fiberglass work, and gained virtually nothing. The plenum needed a lot of modification to retrofit into existing baffles.

My reason for doing it originally was to get lower CHT's but the 10 measly degrees didn't cut it. Got better cooling by RTVing the lower baffles to the cylinders. Was also hoping to see some increase in speed but have not noticed any increase probably because it was a clean set-up prior.

If you do decide to do it, be prepared for lots and lots of fiberglass work. Get the cowling inserts they sell to graft into the front of the Vans cowling and be prepared to cut off almost the entire front of the Vans cowl to install them. If you are retrofitting the plenum to existing baffles then also be prepared to highly modify the plenum to the point where you will say it was easier just to make your own.

Now, to specifically answer your questions:
A) Did you use the round inlet rings and if so, perhaps you could describe the best method to graft them to the Vans cowl?
Yes. The inlet rings have a keyed notch which holds them in place in the cowling. SJ will send you directions for how to do this and there is lots of info on the SJ yahoo list along with pictures.

B) If you did not use the inlet rings, but kept the inlets stock, how does it perform for cooling especially in extended climbs. Did you reduce the size of the rectangular inlets?
Used the round inlets but saw no difference in performance from my stock set-up and only an avg 10 deg drop in CHT's

C) Do you feel there is a reduction in drag with your particular setup?
No

D) If you used the SJ cowl and plenum, could you comment on the use of the required prop extension, cooling and overall performance?
Not needed for the Vans cowling mod

Join the SJ yahoo group. I posted my install pics there as have others along with details on installs and retrofits.

pierre smith · #7 03-24-2009, 05:54 AM

...and kept up with its progress from day 1. Needless to say, the whole process was cussed repeatedly and very difficult and time consuming. Probably doubled the cowl/baffle installation time. The three of us agreed that it won't happen again. It was the complete SJ setup...cowls and plenum...and it needed major surgery to fit.

Regards,

miyu1975 · #8 03-24-2009, 09:33 AM

this is good info as I have been wondering if it was possible to convert the sj plenum inlets from round to rectanglar ie the standard Vans cowl...sounds possible buy maybe not worth the time and effort???

osxuser · #9 03-24-2009, 10:18 AM

It's not that hard to convert Van's baffle kit into a plentum. I'd go that route over trying to convert a SJ plentum into the square inlet. Done it on a Glasair before...

f1rocket · #10 03-24-2009, 11:00 AM

I have built two plenums for my Rockets and it is fairly simple to do. If you just want the plenum, build it from scratch out of aluminum.

I have a friend who won a Gold Lindy at Oshkosh with his RV-8 and he installed the SJ rings and plenum. He said he would not do it again. You can achieve the same cooling improvement by opening up the inside top of the inlet opening and smoothing the airflow out. That's probably where most of the SJ cooling improvement is coming from.

You should get some speed gain from the SJ install as it is supposed have less cooling drag than the standard openings, but there are so many variables that it is not easy to detect.