sandia8

First: I too would like to know if BOOSTED7 ever got any info, seems like he a good contact??? Been a while!

[I]Originally Posted by BOOSTD 7
I will call my contact at Mazda first thing tomorrow morning and pose some of these questions. I know the side seal is totally new on the RENESIS, and from seeing them in person they're set back farther and thicker than old ones.[/I]
Second: After reviewing multiple posted pictures in this thread, I see mainly
normal/original casting marks and machine tool cuts/marks. While a miss-tooling cut COULD cause a larger port opening and loss of compression, I see NO marks that can be attributed to the seals hitting the port areas as I feel some have suggested. Perhaps poor pictures, or my mis-understanding.

Third, there still seems to be a major issue of potential sideseal gaps larger then .002 to .006. If true, has quality control gone to hell, or are these engines being manufactured in Korea or China.

86rx7

The knick is hard to see in the pictures but it is there, i felt it with my own hands, it was about 2-3 mm deep and long. The weird part of the port in question is that weird semi circle in the top left corner of the port,.. it serves no purpose (purhaps mazda knows something we dont and it does??) and creates a potential hazard for the side seals.

I think the problem with the side seals is that they are not making ones long enough to fit even the shortest grooves. On the renn Mazda decided to use precut side seals of differnt lengths to fit the differnt letter stamped groooves,.. the problem mazdatrix had was the largest of the side seals was nearly out of spec in the smallest groove. The precut seals are a great idea and saveus from having to hand clearence them but mazda should make them longer to get closer to in spec.

This isnt an issue to sell your car over, it will not cause failure, it will just loose a few HP,... boingers loose HP as they age,... the renny is still an awesome motor.

Mr. Port & Polish

The renesis is an awesome engine.. I was surprised to see such large ports. My aggresive streeport template was smaller(in intake opening) then the stock renesis port. Never the case before. I could go on and on about how great the engine is.. But members already know that. International engine of the year back to back.

sandia8

That weird semi circle 'looks' exactly like a mis que of a verticle milling machine bit. you see the same type of marks from a hand wood router. Perhalps it happened during a bit replacement or bad computer (x,y) data entered into the routing pattern. I can just see an operator entering in a 2.54 mm 'x' coordinates
versus 2.45 mm thus causing a mis cut
Now if it is on all the engines, one should wonder if it wouls be like a software bug, since I AGREE it's a potential hazard for the side seals!

I'm hoping the renesis will last as long as my 12A did on my 1980 -7
That was a major resosn to buy the 2004 rx-8

wakeech

it probably will last as long as that 12A, as people've said, the efficiency of the motor during the compression phase has just been comprimised a little bit, as opposed to a pin pulled out of a grenade as some people seem to think of it.

rotarygod

If it was a widespread issue, we'd be hearing about a lot of blown engines. If you've got several thousand miles on your engine and it still runs, it's probably going to keep running. If the impact was severe enough, you'd all be seeing broken side seals. We haven't seen that yet. Even the engine at Racing Beat died from a broken apex seal. The side seal was fine. It just left that score mark.

zoom44

oh yeah i have already had discussions about that.

zoom44

sorry you cant see the side seal nick i tried to clean up that one pic and highlight it so everyone could see. its quite obvious in person and is very clear on my pc.

as for the semi circle machining- you can go back to pics as early as from the press pack and any in between then and now and see that. i would go either with a glitch or a programmers error. either way it is obviously bad for side seal support and serves no purpose since the casting underneath is not cut the same way. it is some kind of error that someone in quality control decided they could live with or didnt notice(?) at first and maybe fixed on later engine runs.

shams42

This is all very interesting.

Do you think this explains the "missing horsepower" issue?

The issue isn't that the engine loses power over its lifespan. As someone just said, all engines slowly lose compression. The issue is the rapidity and severity of the compression loss. In my opinion, no motor should have a measurable compression loss before 25,000 miles. It's still practically new at that point! And if the compression numbers I've seen on other threads are accurate (123 spec, ~100 measured), well, that's a 20% compression loss! Now, the accelerated wear might stabilize at this point, but still... that's quite a loss in compression. Is there a linear relationship between compression and engine output?

And let's face it, the Renesis doesn't have a lot of spare horsepower to lose!

I eagerly await more information and especially some information from Mazda. They've got a lot of potential bad press brewing here and it would serve them well to step in a talk about it.

rotarygod

No. Tuning explains that.

shams42

RG, I hope you are right about the tuning issue. It just worries me because I haven't seen any aftermarket products that restore a significant amount of power from tuning. Hopefully as the 8's ECU becomes better understood, we'll see this happen. My fingers are crossed.

rx8daniel

is there any validity to having the dealer do a compression reading early in one's life ( I have 17K+) so that around 45-49K I can go back and have them do another for comparison in order to gauge any degradation in the engine B4 the warranty expires? Just curious. Any thoughts?

zoom44

it might buy you peace of mind and give you a base line to compare against later in the life of the engine BUT i wouldnt suggest to everyone panicing and running out and demanding one right now. getting one in conjunction with your next service would suffice.

RotorGeek

I plan on haveing my dealer perform a compression test next time I do a oil change. Does anybody know how much it cost for this.

Richard Paul

iTrader: (5)

Did anyone else notice that Chuck Huang from rotary extreem way back on 3/11/04 on the boost solution thread talked about this.
I had never read that thread till just now.
So how did he know all this back then?
And why didn't anyone get excited about it then??

Some people out there know more then they are telling.
Just my $0.02

zoom44

for reference richard is talking about this post and the discussion following it. here's a quote you can read the rest for your selves:

there were other reports/rumours at that time that various companies had broken side/apex seals while trying to boost. which could be expected during testing. but none except for Chuck offered confirmation also no one offered any explanation as to the reason except for "stress". had they mentioned bad side seal clearances or side seals hitting the port then we could have had this discussion much sooner. Chuck doesnt even say that they at Rotary EXtreme even attempted Forced induction and blew a seal- he just states that he heard others had had trouble and they decided against trying. On the other hand Racing Beat has tested a Supecharger without breaking a side seal but they did break an Apex seal.

rotarygod

You aren't going to see much in the way of aftermarket gains. Don't believe any claims of 10 hp for intakes or 20 hp for exhausts. It isn't going to happen. All of the aftermarket ecu's right now are piggyback units. These are more complex to tune as the factory ecu is still doing what it wants to and the piggyback unit is trying to alter it. What makes it more complicated still is that the RX-8 ecu has several different maps depending on circumstance. You can set up a piggyback unit to do one thing to one map but if the ecu decided it wants to use a different map in a differet scenario, now your fighting it all over again. Ric Shaw's ecu currently has the most control. Hopefully as time goes on, they'll find a way to make it a true standalone unit. The PFC purple box for the 3rd gen RX-7 originally started life as a piggyback unit. After a few years code was updated and it was able to function as a totally independent stand alone unit. People had tuning issues until then. Give it time.

Japan8

Here is some seal info from an old post of mine...

Apex Seal
13B-REW
2mm thick/ 3 piece
material/ cast iron

Renesis
2mm thick/2 piece
material/ cast iron

Side Seal
0.7mm thick
perpendicular cross section
material/sintered iron

1.2mm thick
trapezoid cross section
material/sintered iron

Corner Seal
Rubber plug

Cast iron plug
DLC (Diamond-like Carbon) coating

Blow-by Cut-off Seal
N/A

material/ductile cast iron

rxeightr

Here's another way to look at this compession loss, and this is in a good way.

Since the RENESIS had a higher compression ratio advertised then previous rotaries (10:1 if memory serves me correctly), then the resulting lower compression ratio will only serve to help potential detonation issues when we put on forced induction.

shelleys_man_06

How much compression loss are we talking about with the clearance issue? You make it sound like dropping it to 8.5:1. I wouldn't want to have a motor knowing something like that is going on internally. For FI, sealing is just as important as natural aspiration.

Ajax

Agreed. I doubt we'd see that much of a drop, but a non sealing FI engine is just a waste of gas.

Richard Paul

iTrader: (5)

You guys are getting confused again.
Static or mechanical compression ratio does not change. It is a function of the swept and unswept volumes. Cannot change over time or conditions.
It was built with 10 to 1, it will die with 10 to 1.

Now the dynamic compression is a combination of several factors and can change with conditions, rather does change with conditions.

The cranking compression pressure is a dynamic number. However it does not tell you the running pressure. When running the factors of flow, time, pressure, friction and ambiant conditions come into play. Among others that is. Yes here is where the leakage fits in. But a small leakage has time to be factored with.

Say per cycle x leaks out at 1000 rpm. That little space has time to be effective at 9000 it has none. Also the timing has everything to do with the compression both cranking and running. An enging with short timing will have more cranking compression but at higher rpm will have less pressure because it will not fill the chamber as well.

Example: your engine has stock porting and 130 psi cranking compression. A race engine may have 90 psi. Do you think your engine is going to make more power??
It probably will. Up to maybe 3000 rpm. Or some other point depending on the power curve built into the race engine.

Peak pressure is going to be at peak torque or vs/vs. This is your most efficent running point the best filling is occuring here. Therefore the highest pressure and the point of most damage in the case of detonation. After this point the factors of time and friction lessen the fill mass. The horsepower can still go up because that includes work done in time.

So what is important here is that while we do not want all that seal clearance it will not kill the hp by that much. The problem is when the seal breaks and the leakage becomes gross. Plus getting damaging bits into your engine. So don;t go off expecting your power to be slipping away as you sleep. Don't go selling your car just yet.

Yes, it is nice to check your compression now ans then but I bet you will find the Renn will lose pressure the same rate as anything else. The most telling tale would be if one chamber loses more then the other. Then you can argue with the dealer. Then you have an abnormal wear A/B test.

Hope I helped.
Richard

reddragonmd

I dont take any credit in anyone who claims to have valuable info, yet decides to give it to the public in "spurts" when and if he sees fit. Either lay it all out and stop trying to be secretive, or...

Just my 2 cents. My car has 9K miles and is running great. All updates done. I get about 18mpg now.

shelleys_man_06

Richard, that reminded me of a thread I bantered back-and-forth with someone not too long ago.

http://www.rx7club.com/showthread.php?t=330345

86rx7

Richard just made an awesome post. This is exactly why low compression effects starting and low rpm operation more than high.