Excellent video on making reliable power in a Mazda Rotary engine

Homebuilt Aircraft & Kit Plane Forum

Help Support Homebuilt Aircraft & Kit Plane Forum:

paraplane

Well-Known Member
Joined
Jul 22, 2014
Messages
68
Location
California
While I don't own a Rotary engine car or aircraft I'm interested in these engines. I've read most articles by Paul Lamar and while his ideas are very interesting I feel that a lot of his work is out of the reach or desire for many people to entertain. After watching "Rob Dahm"s YouTube channel for quite awhile it was cool to see him make this video where he is concise and outlines what to do with a Mazda engine to provide power and probably more importantly (especially for aircraft) reliability.
I read a comment that was somewhat recent where the poster was basically asking the question(s) that this video answers.
 

rv7charlie

Well-Known Member
Joined
Nov 17, 2014
Messages
2,963
Location
Pocahontas MS
Just saw this thread; haven't had time to watch the vid yet. But I'll bet I can come pretty close to 'fixed' without the vid.

Start with a good running engine. Replace the thermal pellet in the end of the E-shaft with 'calibrated orifice' plug available from racing shops. Stop. Do not pass go; do not remove any case bolts.

Focus on water & oil cooling.
 

paraplane

Well-Known Member
Joined
Jul 22, 2014
Messages
68
Location
California
You're familiar with Mazda Rotary rv7charlie I know from seeing many post's that you've made in the Mazda Conversion section on HBA. I didn't post link to the video for people with you're knowledge but for people new to considering Mazda Rotary. That's great you're confident in you're abilities and confidence is an excellent trait for an aircraft pilot. You may still want to consider watching the video as this guy has made an excellent living and funded an Extreme RX-7 build and numerous other 13B and 20B builds plus the shop and tools with his YouTube channel and passion for those cars and engines from the time he was a teenager. Just saying.
 

TFF

Well-Known Member
Joined
Apr 28, 2010
Messages
17,019
Location
Memphis, TN
He is definitely not talking about airplanes. Most rotary airplanes are meant to be traveling planes. A lot of convenience needs to be built in. Running premix in E85 is not very practical for an airplane. Not opposed to adding oil to the gas, but only as extra help, not only solution. Case bolts and dowel mods, maybe if you are leaking coolant, same with oil. My biggest come away for the regular engine is don’t run synthetic oil in the crankcase for the apex seals.
 

rv7charlie

Well-Known Member
Joined
Nov 17, 2014
Messages
2,963
Location
Pocahontas MS
I fully intended to watch it; just hadn't had time to watch it when I wrote the post. Just watched it this morning, and all the mods he mentions are common knowledge for rotary 'tuners'. But as expected, they're all focused on making insane levels of power from the engine. Running any 'conversion' (auto) engine in an a/c at higher than its original stock HP is rarely, if ever, a good idea. So all those mods that prevent the engine from doing the 'banana' thing just aren't needed in an engine that survives at 'stock' HP levels, and trying to do the mods when you're not experienced in working on the engine greatly increases the risk of doing more harm than good. The only *internal* mod that I've seen the a/c guys do that might be justified is typically done on the older 13B engines. That's to remove the tension bolts one at a time & coat them with a spiral of silicone & replace/torque them. There have been a few cases of a tension bolt breaking, attributed to the bolt being excited at its resonant frequency & failing due to fatigue. I don't recall it being an issue with the Renesis, but I could be wrong. All the other mods he discusses fix issues that basically don't exist until you're pushing the engine way beyond what you'd ever do in a 'daily driver' aircraft.

AFAIK, everyone flying the engine uses either 2stroke premix (as he described in the vid), or uses Richard Sohn's adapter for the oil injection metering pump and runs an external 2stroke oil tank. But that's not a mod to the engine core.

Bottom line, for me, is that if you're not dwalker (I most certainly am not), leave the core alone except for the thermal pellet mod and focus on cooling. Then try to get the intake (& exhaust, if you're running a 13B) right to get stock power levels back after removing the originals.
 

paraplane

Well-Known Member
Joined
Jul 22, 2014
Messages
68
Location
California
As E85 isn't practical for aircraft use leaded fuel isn't practical for human health. That aside why not build an engine that is able to withstand higher hp figures and don't run those higher horsepowers? I don't know that I'll ever build a Rotary or fly an aircraft with one but if I do at least a little learning from Rob Dahm and Paul Lamar would likely be applied to my build and why not use blueprinting from Mazda as a reference to build a mostly new engine maybe with air cooling. There are air-cooled Wankel engines.
 

TFF

Well-Known Member
Joined
Apr 28, 2010
Messages
17,019
Location
Memphis, TN
Except for clearancing the rotors, everything else was about preventing detonation and keeping apex seals lubricated. Dowel mods might be nice, but it seems more like a way to repair a bad motor at the hp ratings a stock engine runs at. The big takeaway is don’t think a junkyard motor is your ticket to a cheap motor. Engine management is probably the biggest mod.
 

wsimpso1

Super Moderator
Staff member
Joined
Oct 18, 2003
Messages
9,019
Location
Saline Michigan
As E85 isn't practical for aircraft use leaded fuel isn't practical for human health. That aside why not build an engine that is able to withstand higher hp figures and don't run those higher horsepowers? I don't know that I'll ever build a Rotary or fly an aircraft with one but if I do at least a little learning from Rob Dahm and Paul Lamar would likely be applied to my build and why not use blueprinting from Mazda as a reference to build a mostly new engine maybe with air cooling. There are air-cooled Wankel engines.
Leaded fuel is what is at all airports. Swift fuel takes some planning for trips, but it is unleaded 94 octane.

Why not build an engine able to withstand higher HP? You can and it most likely does not hurt anything at power and rpm levels we use in airplanes. I suspect that it also does not hurt anything to NOT do it at our power and rpm levels. Here is why: The bolts and the like are sized for normally aspirated or mildly boosted power of the RX7 and RX8. Quite a few folks running 150-200 hp with essentially stock innards and decently long lived engines. The stock bolts are supposedly plenty strong enough and plenty stiff enough to keep the stack of housings clamped and not shifting relative to each other at these combustion chamber pressures. Go from 200 hp to 500 hp and more, you have to raise the boost and combustion chamber peak pressures to 250% of stock, which means the engine is also trying 250% harder than stock to separate the housings and twist the housings relative to each other. This is fastener theory basics - the fasteners must keep housings clamped sufficient to prevent opening the joints and relative movement between housings. So, you make the bolts thicker and/or tightly pin the parts against relative rotation.

So, if the power is low, and the joints neither shift nor open in use, adding more bolt/pin stiffness adds no advantage to the engine.

As to building your own new Wankel with aircooling, knock yourself out and keep us informed as to how it works out. I suspect that it will result in substantially higher temperatures and thus thermal distortion in the housings on the power and exhaust parts of the housings, which could seriously increase problems with housings, gaskets, and seals. Liquid cooling is great for managing temperatures in the hot areas of all engines, keeping the seals and gaskets alive, keeping the oil from getting cooked, etc.

Billski
 
Last edited:

rv7charlie

Well-Known Member
Joined
Nov 17, 2014
Messages
2,963
Location
Pocahontas MS
Very true, but it's also true that one of the quietest RVs (a -7A) I've ever heard is based not far from you, just north of Austin. It's powered by a Renesis (side exhaust ports) and the entire exhaust is inside the cowl; unlike most rotary powered a/c. It obviously sounds different from a piston engine, but the prop noise is actually as loud or louder than the exhaust. He has flown missions with a friend in a 180 HP Lyc powered RV, and they fly at the same speeds with the same fuel burn. (I suspect that the friend doesn't run lean of peak, but not a lot of Lyc drivers do.)
 

paraplane

Well-Known Member
Joined
Jul 22, 2014
Messages
68
Location
California
wsimpso

"Here is why: The bolts and the like are sized for normally aspirated or mildly boosted power of the RV7 and RV8."

"This is fastener theory basics"

On a forum called Homebuilt Airplanes.com referring to a Mazda RX-7 and RX-8 engine as an RV7 and RV8...

I realize that you're a very "active" member on this forum but that's a pretty bad "typo" if that's what it was.

If you could please proofread you're comment before posting at least if you're replying to a thread that I posted originally that would be great. To have someone make a comment to me about "Fastener theory basics" and after having Referred to two Mazda ICE engines as what could be confused with two iterations of Van's RV series of aircraft kits it's kinda disrespectful of my post.
 

wsimpso1

Super Moderator
Staff member
Joined
Oct 18, 2003
Messages
9,019
Location
Saline Michigan
wsimpso

"Here is why: The bolts and the like are sized for normally aspirated or mildly boosted power of the RV7 and RV8."

"This is fastener theory basics"

On a forum called Homebuilt Airplanes.com referring to a Mazda RX-7 and RX-8 engine as an RV7 and RV8...

I realize that you're a very "active" member on this forum but that's a pretty bad "typo" if that's what it was.

If you could please proofread you're comment before posting…
Touché. Lets not get too serious about all this, we would also have to point out things like use of the correct form of you’re and your in posts. LOL. I shall edit me post.
 
Last edited:

TFF

Well-Known Member
Joined
Apr 28, 2010
Messages
17,019
Location
Memphis, TN
Even with errors, Billski’s post was about the subject and almost all of yours are about him. You can be the bigger person and keep on with the subject. We want to know why you think your ideas are right, not if it makes you feel bad when questioned about it.
 

Daleandee

Well-Known Member
Joined
Sep 11, 2015
Messages
1,834
Location
SC
Even with errors, Billski’s post was about the subject and almost all of yours are about him. You can be the bigger person and keep on with the subject. We want to know why you think your ideas are right, not if it makes you feel bad when questioned about it.
We know that some "people are abusive, egotistical, lying, theiving, manipulative, self-entitled, self-centered, lazy examples of human beings" so go easy on him. After all ... not many on this list are even qualified to bring Billski his morning coffee! ;)
 

EzyBuildWing

Well-Known Member
Joined
Sep 23, 2009
Messages
577
Location
Sydney NSW Australia
Team Aviation F/X and Russ and Eric McFarland bring you the World Recordfor time to climb to 10.000' in 1'40" from brakes release.
The aircraft is a modified Harmon Rocket powered by a massive Wankel rotary engine boosted to 650hp.
The McFarlands are expert promoters of the Wankel rotary engines

 

Cardmarc

Well-Known Member
Joined
Jun 16, 2021
Messages
80
Let’s all just get back to the superlative design and potential of the Mazda rotary engine design. Mistral almost made it commercial.
 
Top