I got this pipe for my YS 45FR. My question is when I look down the pipe I can see 2 holes side by side. One hole is a stright shot out the pipe and the other has some sort of flapper valve? What is the purpose of this???

My pipe doesn't quite look like that.

Looking down from the inlet, there are two holes at the end of the expansion chamber but they are side-by-side and equal in diameter. After that follows the re-compression chamber. If you set the pipe so that the two holes are lying horizontally and then flip the pipe over to look down the end, there are two exhaust holes prependicular in axis to the expansion holes.

One smaller hole (presumably) provides the necessary back pressure constricting the re-compression chamber. The other one is larger and has a small duct which provides the actual exhaust path. In my pipe it is center offset from the actual pipe outlet rather than inline (straight shot). Dividing the exhaust in this fashion allows them to fine tune the back pressure necessary for the 45FR in particular.

Pipes kind of work like a turbine - the expansion and constriction of the flow sets up a pressure gradient and accelerates the flow increasing the efficiency and power of the engine.

What's that 45FR and 401 going in to? Mine are destined for an MK Arrow 40.

David.

Thanks for the reply. I'll throw my borescope down it and have a look to see whats flaping around. This engine and pipe are going into to my FK Arcomaster (Mk Arrow copy), Its ready for paint right now my AUW is 4.6 lbs. What prop would work best with this plane? I have another ys 45FR on a delta wing.

Well, what a coincidence.

It'd be great to see some pictures of that Arcomaster before you paint it! (and afterward too of course ). 4.6 lbs sounds great.

Props on the Arrow and YS45: I'd aim for an APC 11x5, 11x6.

David.

I need to stay in the 10" prop range for clearance. I turn a 9x9 @ 16.5 on the ground on my other 45FR thats mounted on a 3.75lbs delta. I think a 10x8 10x7. How is the arrow going? I tried to bid on a arrow once way out of my price range. I picked up the Arcomaster last year at a swap for $50.00 NIB I installed robart pneumatic gear in it. Will take some pics this weekend

Well I just looked downt the pipe with our borescope. That Duct is broken thats whats ratteling around i might try and fix it?. Well do they still make these pipes? Do you recomed a pipe from MACS?

The Arrow is not being built yet. Perhaps later this year - other projects to finish first.

10x7 would do well in that case. What type of exhaust do you have on the Delta?

Look forward to the pics.

Using a MACS 1240. Is the Hatori pipe any better than the ones from MACS?

If you would like a Hatori pipe give these guys a shout:
http://www.hatoriusa.com/

I prefer Hatori pipes and it's totally a personal preference kinda thing...Are they any better than Mac's pipes?? Not sure I can say they are...

I think Hatori pipes look kewler... [8D]

I do think there is a quality difference between the Hatori and Mac's headers though...I've had three or four Macs headers crack but no problems with Hatori...Two of the Mac's headers were brand spanking new...One cracked on the first run...Someone suggested I contact "Mr Mac" (or whoever) and that their customer support is really good...I didn't sent them back because I pitched them in the garbage as quick as they broke...Oh Well...Maybe they would have stood behind them...

That YS 45 is an Awesome engine!!

Chuck

MACS would send you a new one right away. I had a 1 year old tuned pipe that cracked. The sent me a new one right away. I'll price the hotori pipe, I think the macs will be a bit cheaper. I don't care about the looks its completely cowled in. I am using on my other YS 45 a MACS 1240 which some folks have told me has to much volume? What do you think?? Also I was going to run a 10x8 on the YS mounted on my Arcomaster (Arrow copy). I can't run a 11" prop due to clearance. My delta seems to like the 45 with a 9x9

Thank you Sir for your help
-Jason

Jason,

The nice thing about having Hatori and Macs available is that you can use the brand that is best suited to the engine. Although not exclusively, Hatori specifically makes (made, in the case of 2c) pipes for YS engines, so they should work well.

Also, if you are going to build a Japanese classic, then YS/Hatori is kinda cool to do. On the other hand, if you are going to build an American Classic, then Jett and Macs is the honorable thing. In the case of a European classic (e.g., the Arrow), one could go Rossi/Webra/ST engine & OPS/Webra pipe.

Of course, in the real world we're not such purists...

David.

I'm no expert on tuned pipe theory...I imagine there are different tuning practices for speed guys and pattern guys...If I were ordering a Macs pipe for the YS 45 I would choose either the 1040 or 1240...

Oh BTW I just thought of something...I've got a new Macs 1040 Quiet pipe I don't need...I bought it several years ago but recently got a Hatori 401 instead...Photo below..PM me if you could use this pipe...

Chuck

macs has a excedllent reputation for replacing any defect, and try weighing a hatori, then a mac, then also try running them back to back you will be suprised...of course the macs arent colored or anodised, one of the things i see so often is guys palcing their pressure taps in the actual header tube in the curve, then complaining that its breaks or strips...... never mind the instructions...[] doh!

Hatori uses thicker wall tubing on their headers so they're going to be heavier...That's fine with me...I'm the dude paying for it and I'll gladly sacrifice a couple of grams in weight for durability any day...

It's great to have an excellent reputation for replacing defective stuff!! But it's better to have a reputation for making stuff that doesn't need to be replaced...

I'm just not really into returning stuff under warranty...Like I say it's a personal thing...If something breaks I'd rather toss it and get a new one...I did actually call Mac's on the most recent header which lasted me a total of 30 seconds, I thought that was a little ridiculous...He was very kind on the phone and asked me to send it back and he would look at it and either repair or replace it as necessary...Very nice of him but I decided to toss it instead and buy a Hatori...

I am not trying to bash Mac's!! I'm glad they are around!! I've only had a problem with their headers (3 or 4 of them)...I like their pipes and will buy more I'm sure...I'll just try to use a different source for headers when I can...

These are only my opinions based on my own personal experience

I was curious so, for fun, I weighed some myself (note the weight difference compared to Chuck's photos. I guess not all scales or pipes are equal).

In order: Mac's 6.5 MP (14.25", 3.3 oz), Hatori 401 7.5 (14.50", 3.4 oz), Mac's 7.5 QP (16.25", 3.7 oz).

In fairness to Mac's, the 401 is sized more closely to a 40 size pipe (6.5 cc) rather than a 45-50 size pipe (7.5 cc) even though its intended purpose might be different. The Mac's 7.5 cc QP is a much longer (and probably quieter) pipe although both the 6.5 and 7.5 share the same header OD of 3/4".

It appears that Hatori makes comparatively shorter pipes than Mac's for the same application. I was surprised when I purchased a Hatori 10 cc LS pipe (650) and saw that it looked more like a 7.5 cc pipe! I actually thought there might have been a mixup.

David.

P.S. Lorin, I'll drop you a PM in the next coupla days.

Chuck,

are you sure that's a 7.5 cc QP and not a MP? I'm surprised it weighs less than the 401!

The 7.5 QP should be 16.25" long and ~3.7 oz (Mac's specs say 16.5", 3.4 oz). The 7.5 MP by Mac's specs is 15.25" long (1" less) and 3.6 oz.

David.

It's 16.25" long...I couldn't remember for sure what pipe it was but know I *would have* bought a quiet pipe (relying on my memory isn't very reliable though)...So I went to the Mac's website and noticed the difference in length between the MP and the QP...That's how I confirmed which pipe it was...I have three YS 45's and had only one Hatori pipe so I bought two Macs at the time...I've since got another Hatori 401...

Man my scale is wayyy off...Dang...I switched to OZ and the Mac's pipe weighs 4.0 oz and the Hatori weighs 4.2 oz...Something is really goofy...I think I better get a new scale!!! Oh Well..it's always something...

Both of my pipes are new so there's no residual oil or crud in them?? Weird...

Oh yea...

that scale does sound off. They're supposed to be pretty good. Warranty...? Or toss it and get a new one? Mind you, my scale is a $20 job but given specs and actual weights I trust it is in the ballpark.

Take a pack of steaks weighed at the store and throw them on. You'll know how off the scale is! But don't go away thinking you've got a meatier dinner in your hands...

David.