MincVinyl

I recently did the Rx8 performance Aluminum engine mounts and everything seems right in the world. No shaking, vibrations, or anything of the sort.

First mods I'd do on any new Rx8....This is without saying normal necessary parts like battery/starter/tires/etc

• Midpipe (I believe BHR makes a Midpipe with a Cat option or the decat option-creates engine code, look into S2 tuning options to turn off this DTC code, mazda made S2 computer more difficult last time I looked into it)
• LS coil kit upgrade (I have the bennet built kit, which works with the OEM coil dwell tune perfectly fine)
• Sohn oil adapter (my only gripe is that they give you a really small washer fluid tank. I made my own washer tank, It might be worth it to keep the OEM washer tank and find your own way to mount the oil tank)
• Compression Tester

CaymanRotary

Hopefully. Bet it isn't serious.

sshe11

Yup - thinking of BHR mid-pipe with RB exhaust and BHR ignition kit. Will read up on the Sohn oil adapter.

MincVinyl

The only thing that annoys me with the RB catback is that on all their exhausts they pinch down to a 2.5in flange to match the OEM size. I did contact them and they said normally they would be able to do a 3in flange for me, but because of covid they are swamped with orders and dont want to mess with the jig.

mikeljourdann

I have the BHR midpipe (with stock exhaust back) and rarely get a CEL. I think I've cleared it once in the 2 months or so since I had it installed, FYI.

sshe11

Got the comprssion test results:

Forward: 7.9, 7.5, 8.1
Back: 7.4, 7.4, 7.6

Based on my reading, these numbers look fine. Any thoughts?

CaymanRotary

As long as those are adjusted to 250 rpm on a warmed engine yes, those are healthy numbers.

sshe11

Yes, it was at operating temperature. Front rpm was 275 and rear was 276.

CaymanRotary

So numbers would be adjusted down because you want the RPM to be 250 for the measurement. That means your 250 rpm corrected numbers are:

7.2, 6.9, 7.4
6.8, 6.8, 7.0

Still meets Mazda minimum spec but start saving for a new engine or rebuild.

fuzzymanp

I’m no guru on the engine mods or any of that but I would recommend or what I like to do first is handling mods. I usually do suspension first and wheels that are lighter! Just my personal opinion!

sshe11

Okay. How much more life do you think is left? I plan to do BHR Ignition, BHR Midpipe, RB Catback mods.

CaymanRotary

Hard to say but it could last quite a bit longer if well maintained. You will see reduction in power. As long as you are willing to do those upgrades it would be worth it to do a swap or rebuild down the road. Its impossible to predict exactly when an engine will fail, but I've run minimum spec engines for well over 10-15k miles without issue.

sshe11

Thanks - my only concern is that engine blowing up in the next 15-20k .. I am mentally prepared to do a rebuild after 2-3 years because I will drive less than 7,000 miles/year in summer only.

What is the Mazda minimum spec? and How much power loss do you think it currently suffering from?

Loki

iTrader: (1)

That's not how this works. You could start having actual symptoms tomorrow or in 10 years. Mazda minspec is 6.9, but that doesn't mean it's time for a rebuild. At some point you will find it hard to restart the car when warm, that'll be a sign it's time.

It's good that you're mentally and financially preparing for a replacement engine (not a rebuild of yours), but enjoy the car until you actually have problems. As for power loss, hard to say. 20hp? 30? 0? It depends where the compression is lost. You can try to premix oil to help sealing and longevity from this point on.

sshe11

Got it - I did do a hot start and it started quickly. I know a local rotary specialist that does rebuilds but not sure how much and where I can find new engines. Any cost estimates?

CaymanRotary

Minimum spec is 6.9 bar with a no more than 1.25 bar difference between rotor chambers. This is where Mazda has determined minimum compression is. That does not mean it can't be used or be reliable. Anything over 6 bar is still a usable engine in my experience. With your numbers your power reduction is about 15-20% lower than a fully healthy engine. With 7k miles a year you could still get a couple more years out of this engine but ultimately, no way to know when exactly it will fail.

Here is a chart that shows how minimum spec is determined by Mazda. I would go ahead and do your upgrades but know your engine is borderline on its way to failure and that you should start to put some money away for a future engine replacement or rebuild.

CaymanRotary

For something good from a quality rebuilder or a Mazda reman can range $4000-$6000 including labor. If you can source a known good second hand engine $2000-$4000 including labor.

MincVinyl

Well the engine won't blow up or have some crazy drama. One day it may just shut off at idle, or stall really easily, and then just not want to hot start. Few more miles down the line and then it really wont hot start. Once you start losing compression, there is a minimum RPM that the engine must meet in order to sustain combustion. As you run compression dry, that rpm threshold will only increase day by day. Eventually like I found out when testing one of my junk engines It is fully possible to run an engine so dry that it stalls when it gets halfway up to temperature.

Now I'd like to say you SHOULD rebuild at first signs of issues. This is because I believe you will start to cause excessive wear on other components trying to run the engine dry. If you want to price things out just to see, look up 2 new housings 2 new rotors and a full resealing kit.....only reason to go away from mazda OEM seals is if you plan on boosting. At that point you would look into having the rebuild shop machine the rotors to fit the taller rx7 apex seals. Porting wise, there is no point to touch the intakes, at most you might just clean up the edges on the port to ensure the side seals can glide easily. As for exhaust porting, there are some gains to be made in cleaning up and street porting. However it is very easy to destroy the iron by cutting into the coolant jacket.

sshe11

Yup - this helps. I also read that "new" engines are around 7.5-8? but this chart goes to 9.2 - I guess rotaries loose compression with mileage even with proper maintenance?

CaymanRotary

They lose compression no matter what you do. Its just the nature of the beast here. That being said, proper care and maintenance can allow a well built engine to last a long time. Have a new engine in one of my cars and its 8.5-9.2 bar all around. It was shipped from Japan with a new engine installed. Compression is still the same 2 years later.

Loki

iTrader: (1)

Bit of a tangent but this statement made me think of how much an apex seal travels compared to a piston ring. If you take a comparable engine, F20C, 84mm stroke gives you 45km of travel against the cylinder bore at 4500rpm in 1 hour.

For a 13b, the apex seal travel against the housing surface is 71km under same conditions.

So a 100k mile rotary is closing in on the wear of a 160k piston engine of comparable performance by length of seal travel alone.

​​​​​

CaymanRotary

If it were only the seals that we had to worry about. Bearings also come into play and can fail before the seals do. Good observation though. Never really thought about the seals in our engines that way.

sshe11

Update: Picking up the car next week. Dealer had to put new tires and brakes (pads + rotors) for the car to pass Safety in Ontario. I offered to pay the difference for Mazda OEM parts and Conti ExtremeContact Sport tires. They were probably going with cheaper options to pass safety.

My question: Given its age, do I need to replace the MAF sensor on it? If so, do I just use the Mazda OEM? or other brands?

CaymanRotary

Unless its giving you a code or running rough I wouldn't. Get some MAF cleaner and give it a try. Its easy to remove, just the one plug and 2 screws.

sshe11

Finally picked up the car this week. I proceeded to change the cabin filter and in doing so broke the damper mechanism! D'oh! Any way to replace it or fix it? Is it a big issue?

After a ton of reading, I have landed on the following maintenance/mods. Feel free to provide some suggestions!

1. Amsoil Saber Pro premix (200 ML for every fill)
2. Castrol GTX 5W-30 (conventional)
3. BHR Ignition Kit
4. BHR Mid-pipe
5. RB Cat back
6. Wix air filter
7. New OEM Brakes (pads + rotors) - Done
8. New Continental ExtremeContact DWS06 (225/45/19) - Done
9. Brake fluid flush with Motul DOT 5.1 Brake (1.5 quarts) - should be okay since it is 5.1 and not silicone based
10. Coolant flush with Mazda FL-22 (3 x 4L jugs) and Redline Water wetter
11. Transmission flush with Redline MT-90
12. Differential fluid flush with Redline 75W-90
13. OBD Fusion mobile app
14. RB Oil cooler and AC condensor screen
15. SS brake and clutch lines (maybe)