Renesis side seal discussion
 

Many forum members will catch on to who I am. Just be happy I'm back to show support for this awesome engine and car that mazda has put together for our enjoyment and pleasure. Maybe this time around a little more respect will be shown or I will definetly disappear..


That being said, I'll continue. When Mazda made the intake ports 30% larger a problem is happening as for as durability. The sideseals and cornerseals are being hammered by the closing edge of the intake ports. When this happens the sideseal becomes shorter(In length wise) and the engine starts to loose power and vacuum. Basically a larger gap between the sideseal and corner seals.

When a naturally aspirated engine is being put together your trying to extract the most amount sealing compression out the engine. When a larger gap between seals starts to happen the engine starts to loose power. Normally a rotary engine starts to wear sideseals to a gap of .016 of an inch(originally the engine is assembled to .002-.006 of an inch) after 75,000 to 140,000 miles.

My renesis engine only had 14,000 miles and I had a durability problem. When I took the engine apart I notice a serious sideseal and corner seal wear. Causing my engine to loose power and vacuum. My engines sideseal to corner seal wear was shocking. I measured .018 to .020 thousands of an inch on a fairly new engine. I had dynoed 188 rwhp and on my last dyno run(when I first purchased the Rx8 and had 2000 miles on the engine) 14,000miles later I barely could make 170rwhp. I noticed the car felt slower and I decided to tear my engine apart. The lost in power was a pure fact of sideseal to corner seal gap.

A rotary engine wizard and I talked about the sideseal to corner seal problems due to a larger intake port and closing edge of the ports.(I will not mention his name because he directly works in R&D for the rotary engine with Mazda) He stated that mazda is having durability problems with the sideseal and corner gap.

The good news, Many Rx8 owners will not care about engine warranty. In that case I have always ported rotary engines in extreme ways. Most of the time I had to pay close attention to sideseal and corner seal damage due to a large streetport. I have found ways to create reliable huge ports and protect sideseal to corner seals. This early experimenting with large streetports applies to the renesis engine. Very close attention needs to be payed to the closing edge of the ports to protect the sideseals and corner seals. I have ported and polished my renesis engine and made my ports even larger. A follow up to this thread will be made.

I don't want to scare Rx8 owners. Yes there is a durability problem. (Not your fault) for who ever is not interested in porting and polishing their engine and making respectable horsepower gains and getting durability, could always take the car back for engine warranty when they start to feel lost of power due to premature sideseal wear.

and yes gentlemen these are the facts!!!!

Awesome, welcome back, friend. ;)

Hmm. I knew it was a a seal issue. Is there any way to fix this durability problem?

Thank you, I hoped you would do this.

Is the seal wear only based on total mileage on the engine or is it dependant upon how hard you run your engine?

Also I have heard that mazda is still putting its rotary engines through breakin procedure before they are put in the car. That would be one reason why it says there is really no breakin period needed in the owners manual. Do you think the simple break-in procedure could have caused a different seal position, and therefore when the car was being sold its horsepower had actually dropped from 247 to less than 238? Could there be some extra wear during the break-in procedure that would cause a seal gap in the car before it was sold, or do you just think it was completely emissions related?

Welcome back! It is always a shame to lose such knowledgable and experienced people... glad that we didn't here. After reading http://www.rotaryengineillustrated.c...-ports101.html , which helped me to visualize the situation better (I'm a very visual person), I can definitely see what you're talking about. For those concerned about durability... not good news...

Sweet, I've always wanted a car that gradually loses power over its life time !

Woh, big news.

So, what is Mazda going to do about this, when people start having engines lose compression and/or fail at, say, 25000 miles?

i would think the best way to see this would be to take a compression reading early on and then around 6,000 to 10,000 .its not that hard

Other than warranty, what are the downsides of the proposed porting? Maybe Mazda can quietly change the porting on the stock engine a bit to accomodate this? Or maybe there are emissions/mileage concerns as well?

jds

engine shaking .

This would also be a explaination as to why the side seals were blowing so often for those that where trying to add somesort of FI to the engine.
Correct?

So you're saying that by porting the engine (or at least polishing it), it's possible to actually get more power and make the side seals last longer?
If that's the case, and mazda knows about it, shouldn't they be doing a mass recall on the car and replacing every single engine?

If this is really true the RX8 is as good as dead. It's hard to believe that this didn't show up during development. This engine wasn't designed and implemented overnight.

Not questioning the findings, but I gotta wonder if there's something else going on here....

Hard to believe that Mazda wouldn't have done long term durability testing of the Renesis prior to releasing it on the market, just like every other car manufacturer does with it's engines. Hard to believe that Mazda would sell a car with an engine that that will self destruct at relatively low mileage.

I agree, engine teardown and wear measurement is mandatory during development. This should have showed up early on.

For some great shots of the Renesis being torn apart see http://mrec.rotary.net.nz/secretagent1.htm

Question for mr.port, in regaurds to this picture:
http://mrec.rotary.net.nz/spies/2rx8.jpg

When you torn your motor apart did you find this much rust around the water jacket thing? In particular where that coolant entrance (nipple) is? I thought these surfaces would be galvanized or zinc plated or something.......

What is this compression check, and how do you do it? Is there any way to have the dealer check for anything?

Troy J.

Your saying our engine will lose power at around 20k miles. You are also suggesting porting and polishing our motors to help make our motors more durable.

******MOD EDIT****** (he has made it clear he is not in prior situations *public warning, do not bash. *)

If this is true, Mazda has made the biggest mistake i have ever seen

I was thinking the same thing.

You guys are overreacting; this is common to all rotaries.... however in the renesis it seems to be accelerated 10fold dude to the 30% larger intake ports.

Without tearing apart more motors we can't be sure if it is this bad in all the motors.

After all im positive Mr. Port Polish didn't follow break-in as well as he probably drives the car much harder then most of us. ;)

I hope this is not so, would not Mazda find some kind of lawsuit on their hands when engines start to fail just after 48,000 miles....or are they just going to say.."well you should of purchased the extended warranty!"

I think this might be far fetched. I honestly believe if they find a problem there will be some kind of recall or perhaps another $500 debit card :)

Wayne

His combination of harder driving or it could hopefully be just a single engine problem. Just because one engine blows doesn't mean all of them will, but all I can do is hope. I would like to point out that his engine dynoed higher (188whp, most are low 170s) than most the other dynos that we've seen. We can hope that generally all the RX8 engines have those gaps, and his is just showing up now. His dyno now is similar to what other people have gotten.

Anyways if this shows up in all engines I will drive my car until the engine stops working or is very low on power. Then I will get a completely new engine, and have it ported and polished while it is still new.

I have built 18 of these motors for racing in Grand-Am Cup. I have not seen any issues with the side or corner seals. We have run motors for 50+ hours in racing conditions with an average of 4% loss of power. This is about the same as a raced piston motor. I don't really have any mechanical issues with the motors, and we run them in 3 hour races with an average rpm of around 7400.

4% loss over 50 hours or 4% loss every 50 hours?

It probably loses the 3-4% in around 25-30 hours of racing and then stays the same until 50 hours. That is about as long as we run them before a rebuild. I do not have a complete data base on this because the motor is so new. The current engine I have in our car has a 1.6% loss in 16 hours of racing. This is a pretty good number for any racing engine