Renesis Engine/Rotor Balance
 

An old time forum member who isn’t around much sent me these screen shots from FB recently since I’m not on social media; a synopsis from renowned 13B and Renesis race engine builder Daryl Drummond with his view/experience on Renesis engine balance. There’s a general misconception out there that Mazda supposedly did a better balancing on the Renesis engine, but in reality it’s just not true.

Not just about balance, but a very revealing note about the side exhaust port reality that many people, even established rotary engine specialists, still fail to recognize to this day and how it makes the Renesis unique compared to the previous rotary engines. Because you can’t just do some mods blindly on a Renesis thinking whats good on the earlier engines is good on a Renesis, when in fact it may not be if not through fully.

Just as with the comments about rotors cracking. Good info here to glean from someone who had intimate knowledge and a detailed understanding on the uniqueness/oddities of the Renesis. Anyway, just posting it up:


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That was awesome. Thank you for posting.

Any recommendations for vendors to perform this service? I’m starting to gather parts for a local builder with good reputation that doesn’t offer this option. I have time (I hope) and was planning to supply balanced assembly. I expect to be shipping from somewhere in North America. Edit - I’m assuming from other posts Drummond is retired ( and probably too capable for my wallet to cover ).

Search noob.


JK.
Maybe try calling one of the rebuilders like Kevin at RR, or Rob at Pineapple to see if they can do it or recommend someone.

I don’t even know myself now; up until recently maybe Pettit, but Cam is also getting on in years too and I’ve been hearing of some issues there that can most likely be attributed to work being performed by “others”.

For anyone who read what was here previously, my apology. Sometimes I just don’t understand other people, but I suppose the same is true of me.













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BC - I’ll reach out to Rotary Resurrection.

Team - grandpa of 5 soon with a growing crowd who wonder about me…. I heard the same thing about farming out work with quality issues. Some threads here with early vendor recommendations now complain about QC.

Interesting complimentary discussion concerning rotor balancing relative to the target application.

https://www.nopistons.com/rotary-eng...portant-68803/

I just finished a first read of the link (thanks).

When the topic of rotor mass comes up and small variances vs total mass in particular, doesn’t this point to a bigger issue with the lighter rotors in the 8? Mazda’s intent was better balanced from the factory but, it sounds like reality was not agreeing. Wouldn’t an REW “weather” an imbalance better than the Renesis if the amount off was identical?

REW engines being turbo often don’t exceed 7500-8000 rpm in general. Those who rev higher are more likely to get it balanced, but then you have somebody like Rob Dahm claim it doesn’t matter. He might be a youboob hero, but pro builders know better.

There might only be so much they can do with the parts you provide; the builder in the article above had a relationship with Mazda Motorsports and would order more than a pair, pick the best two with the closest match to start with, and then would sent the rest back.

Also need to be mindful how much you take off and where per the note in the article above about carrying exhaust gasses from the side exhaust port back to the intake cycle. The Renesis SAE paper details this out regarding how Mazda addressed it on the Renesis rotor design and how it’s different than the prior peripheral exhaust port engines as a result. Then go watch the Kyle Mohan hybrid video how he completely either ignored or possibly wasn’t aware of it when he just treated the Renesis rotors the same as 13B rotors. Well we’ll see.
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Given that the listed comments in this thread focus on the how... what I found most interesting was the focus on the when and why?

The take away IMV seems to be... there is significant advantage in applications with sustained operation at or above 8500 rpm. That m/b typical in an NA race application, but not a turbo application where b/c there is so much torque available at lower rpms they tend to live at a lower rpm range.

So, I would likely only consider this expense should I ever desire to prep an NA race engine.

a lot of people blew up turbo engines over the years. You can argue out the reasons why from here to sundown, but in reality it’s already under high stress and it’s not wise imo to be adding a other stress to the situation. It may not matter immediately, but long term it takes it’s toll. It doesn’t even cost that much really. So why be a penny wise and a pound foolish? An NA engine may rev higher, but with much less power loading stress. Going to disagree with that assessment, but what’s new? :suspect:
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Lol, you make a valid point..., but as you say...w/turbo applications blowing for numerous reasons..., still hard to justify in my mind that "this" s/b where I put my $$ vs cooling, solid monitoring & control, proper fuel injection, E35, quality tuning, etc.

I agree with Team that it really is a small cost in terms of an engine rebuild if you're on a healthy budget.

But I am often very budget conscious so for someone rebuilding a renesis, it could be considered expensive for a car with such a low resale value.

IMO I still think balancing is worth it. Just use case of the car should be a consideration when deciding this if you're on a budget.

With all due respect and admiration for our platform...I'm a pragmatist and there are some facts which we do well to accept:

- in some cases persons wheels and tires, or coilovers exceed the value of our cars
- certainly our turbo kits exceed the value of our cars.
- our platform is a labor of love /affinity at this point
- there are more "rollers" every day
- there is nothing that c/b done to prohibit our engine's self consumption..., merely delay it.

Real talk: we've two options:
1. The odyssey comes to an end......(consider the traffic trend on this forum)
2. We keep feeding it cash.

My economic decisions regarding spend on my car, which I still really enjoy :icon_tup:, are guided by these facts, thankfully not budget. If it's necessary, prudent for my application and objectives, I'll do it; otherwise not. "Extra" money is an oxymoron...and what isn't spent "here" is available for allocation elsewhere, e.g. family, travel, and other types of fun.

But to each their own.

^+1
I've said for a long time worth is subjective.

I'd rather spend +$6k on my 18 year old RX8 than +$60k on a new pickup truck or SUV that the market dictates is 'worth' it.

I'll keep spending money on it until I decide it's no longer worth it.

without calling anyone in particular out; I see some people spend plenty of money, just on the wrong things imo …
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