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James cowling help??

B

Bill Whidden

Member
I am ordering the Sam James cowl and plenum for the rv6. I want to put the Air flow Performance FI system on also. I was actually on a 3 way call with Don from AFP and Will from James Cowl and am still not sure if we were all on the same page. So I thought I would ask, .. Has anyone else used this combination and if so how did it work. I also have the cross over exhaust. Which AFP system was used ??and which cowl was ordered?? are the two real questions.

Bill
RV-6 someday.
 
I know you're looking for actual experience, Bill, but I'm in the process of deciding and ordering so here's what I found out and did:

My engine: Mattituck IO-360 w/Airflow Performance Injection and two P-mags.

I talked at length with Will James this morning and the short story is that if you want to truly get the benefit of the James cowl, you want to go with the extended cowl and not the standard length cowl.

The reason, according to Will James, is that the benefits of the James cowl come from the improved aerodynamics of the extended cowl over the standard length James cowl, the "new and improved" induction system made for and supplied with the extended cowl, and of course, the airtight plenum with round inlets that maximize air flow and cooling with less drag.

The better aerodynamics, he says, comes from the extended cowl. Plus, the improved induction system only comes with the extended cowl and not the standard cowl. You could use just the SJ plenum with the standard Van's cowl, but you won't get the benefit of the SJ plenum due to the less than optimum square openings in the Van's cowl.

The other side of that coin is that if you use the extended length SJ cowl, you will have to use a 4" prop extension if you use a fixed pitch prop (like me), or a 2-1/4" prop extension if you go with the Hartzell CS prop. I don't personally think either case is a problem while others may disagree.

I can't definitively say about the exhaust, but I don't think it makes any difference which cowl you use.

The only little "gotcha" you want to know about is that the Airflow Performance FI uses a purge valve. I contacted Don Rivera at AFP this morning concerning using the AFP system with a Sam James Plenum and here's his response cut n' pasted from his email:

"Yes. If you use a Sammy James pressure cowl, please make sure you order the fuel injection kit with a "horizontal mount purge valve assy". This comes as an assembly with the flow divider and purge valve attached with appropriate brackets. The rotation of the purge valve is also reverse from the standard set up."

Hope that helps.
 
Go to Yahoo group

Bill you are in luck. Go to the Yahoo group: http://groups.yahoo.com/group/JamesAircraft/


You can join to post. Be sure to check out file and photo links. There was a great write up with pictures and discription of a FI fwd facing set up. I think it was in a post in the last 2 weeks. There was a link to a builder web site.

I would join and post. George
 
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Highflight said:
The other side of that coin is that if you use the extended length SJ cowl, you will have to use a 4" prop extension if you use a fixed pitch prop (like me), or a 2-1/4" prop extension if you go with the Hartzell CS prop.
Click to expand...
I recall talking this over with another builder, but can't remember the #'s... this reduces the g-limits of the aircraft somewhat doesn't it? If so, anyone know what the new limits are for the CS?
 
Many moons ago I read a thread on the RV-list where the only prop that was compatable with the SJ cowl was a Mooney (?) prop that has a recommended G limit under 4...

By now, the cowl may have evolved to accept other props, or one of the new prop offerings might fit. Can't say.

I'd ask the cowl vendor to be sure.

KB
 
Yes Yes and Yes

Kyle Boatright said:
By now, the cowl may have evolved to accept other props, or one of the new prop offerings might fit. Can't say.

I'd ask the cowl vendor to be sure.

KB
Click to expand...
Yes I don't think it is wise to add an extension on a constant speed prop. The "extended" hub props are more expensive, more rare and the g-limit is about 3.8 g's. All acro should be done at 3 g's any way, but all true.

Yes there are no extended hub props for 200hp IO-360 users, so this produces a little problem, and thus why folks are tempted to add extensions to constant speed props.

Yes SJ is in the process of making "short" cowls so the standard HC-C2YK or HC-C2YR can be used. He has not finished this and who knows when.

Again my solution is using Vans stock cowl and modifying it.

G
 
right set up?

Any reason this set up won't work.

0-360 being converted to API's FI. The project I bought has a rebuilt pressure carb. What to do now with bendix pressure carb?


Buying SJ cowl and plenum. Don't really have a good reason except they claim 7-10 mph increase over the vans one I have now.

Changing out slick mags for 1 e-mag and 1 p-mag.

Getting 4" prop ext. from Saber Manufacturing so my fixed pitched sensenich will fit the new longer cowl.

Have a single egt guage. Should I change to 4-way egt being I now have fuel injection?

Anyone want to come vacation in Sunny Warm Florida for a couple of weeks to get out of the frigid north and help me put all of this stuff together??? Have spare room and car. :D

Bill Whidden
 
Bill Whidden said:
Any reason this set up won't work.

0-360 being converted to API's FI. The project I bought has a rebuilt pressure carb. What to do now with bendix pressure carb?


Buying SJ cowl and plenum. Don't really have a good reason except they claim 7-10 mph increase over the vans one I have now.

Changing out slick mags for 1 e-mag and 1 p-mag.

Getting 4" prop ext. from Saber Manufacturing so my fixed pitched sensenich will fit the new longer cowl.

<SNIP>
:D

Bill Whidden
Click to expand...
Just curious ...

Will the AFP FI setup fit in the "standard" Van's cowl that is normally used with a carburetor?

James
 
Don't do it unless you want to add months to your project!

I've got a WW151 with James extended cowl, plenum and wheel pants. They look great, but the cowl and the plenum required cutting, reglassing and additions to get a decent fit. I will not do it again, but I think Sam is a great guy.
 
Go for it

Bill Whidden said:
Any reason this set up won't work.

0-360 being converted to API's FI. The project I bought has a rebuilt pressure carb. What to do now with bendix pressure carb? SELL IT


Buying SJ cowl and plenum. Don't really have a good reason except they claim 7-10 mph increase over the vans one I have now. ITS TRUE

Changing out slick mags for 1 e-mag and 1 p-mag. GOOD IDEA

Getting 4" prop ext. from Saber Manufacturing so my fixed pitched sensenich will fit the new longer cowl. EXCELLENT IDEA, EXTENSION ON FIXED IS OK

Have a single egt guage. Should I change to 4-way egt being I now have fuel injection? NICE IDEA, NOT A MUST, CONSIDER A 4-CHANNEL GAUGE JUST FOR FLIGHT TEST (FIND THE HOT JUG) AND RETAIN THE SINGLE CHANNEL

Anyone want to come vacation in Sunny Warm Florida for a couple of weeks to get out of the frigid north and help me put all of this stuff together??? Have spare room and car. :D

Bill Whidden
Click to expand...
DO IT, It is like free speed and adding 15 HP that don't burn gas. All those who poopoo the idea don't get it or are jealous. :D

Bill the speed increase is built on sound engineering, physics and aerodynamics. NASA sponsored research thru Mississippi State proved this. LoPresti used this data to produce his aftermarket cowl mods for factory planes. Document performance and the fastest RV's have a SJ/Lopresti/NASA style cowl. Now even new factory planes have cowls that use these principles, but in my opinion Piper and Cessna are missing the boat and not executing the design quite to the extent it could be (but than they are building for the masses).

Yes a 4 channel EGT/CHT would be nice, but not an absolute must. The SJ cowl does not raise temps. In fact it takes the air it needs and does not waste it. The in let area may be 50% smaller but it is used more efficiently and thus you have less cooling drag. You want an explanation, check out the James Aircraft Yahoo group. Look at the first post on the list, which was only started about 6 months ago.

If you have a Sensenich, GET the 4" extension, no problem. The longer cowl is the way to go if you can.

As far as forward induction WHY WHY WHY? Yes it is cool and the promise of "RAM" air is calling, but there is a big problem. There is little room in any cowl to produce an effective "DEFFUSER", taking high velocity air and slowing it down to produce pressure and have a plenum volume big enough to feed the engine. The Van's style AIR BOX (FAB) for vertical induction is very very efficient. With vertical induction you have more room to make a diffuser, plenum and still have room for an air-filter. WHY DO YOU THINK VAN;S FWD INDUCTION AIR USES A "SNORKLE" THAT GOES UP TO THE ENGIEN INLET? The reason is just going forward and making a little constant cross section tube =with no filter is going to add "RAM" forget it. Also you will have lots of air spilling out and amount the "ram tube" creating DRAG.

People don't no know how to measure true RAM rise in the manifold and fool themselves into thinking they are getting something for nothing. Here is the break down.

>Factory Cessna/Piper induction, about 1" HG loss in manifold Pressure
>Van's old RAM air (unfiltered ) scoop, ab out 0"-.25" HG loss manifold pressure
>Van's FAB air box with filter about 0" HG (no loss/gain but low drag and filtered)
>Forward facing horizontal unfiltered induction, 0"-0.25" HG gain (most of the gain is the fact it's unfiltered).​

Bottom line is 0.25" HG at 200 mph is a realistic expectation, which is worth may be 2 HP, 1 mph. However there will be more external drag. The vertical induction gives more room and places the scoop in clean air.

The latter solution is a Horizontal induction is unfiltered. To filter it is a bit of a pain with the limited space. Sam James has a fancy air-box that is filtered but it's RAM gain will be no better than Vans Vertical induction air box. Not having chin scoop is nice from looks but not real practical. Also sucking air in the cowl front just below the spinner, near the hub of the prop, is a terrible place aerodynamically. The prop is beating the air to death there. (The prop blades near the hub are blunt.)

I would get the SJ cowl with vertical induction if you have a choice. If you already have Horizontal induction than the SJ filtered air-box (tube) is the way to go.

George
 
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