Hi All,

I recently had my car's compression tested, and wanted to get some feedback from the community.

The car is a 2004 RX8 Grand Touring 6spd (early 2003 build date), I'm the 2nd owner (possibly third, not sure) with 76k miles now. Car was tuned a couple of months ago by Jeff (MazdaManiac) and put down 171rwhp

Engine / Power Mods:
AEM CAI
Greddy SP2 Exhaust (had)
Rotary Store 80mm Resonated Midpipe w/ Highflow cat
Boost Brothers SS Headers Wrapped
BHR Ignition
COBB AP (Tuned by Jeff)

The Compression Test Results are:

Rotor 1: @ 252 RPM
6.7
6.8
7.1

Rotor 2: @ 248 RPM
6.6
7.1
7.0

I thought it was interesting that the front rotor had lower numbers versus the rear. The car still runs pretty good considering the power is on the weak side (IMO), but starting to notice its having a harder time starting up (long crank times). Fortunately only flooded once. I'm pretty particular with the maintenance as well, and avg about 16-19mpg mixed driving.

What do you all think? Is it a sign of what's to come in the possible near future? I've been tossing around the idea of going FI (Greddy Turbo kit) since I have most all the supporting mods for it (minus upgraded injectors and fuel pump). But might not be a good idea to build upon this motor if it's weak.

Thanks in advance!

 

Bump... Anyone? Anyone? Bueller? Bueller?

 

Looking at the numbers normalized to 250rpm, they don't look bad for a car with 76K miles.
Couple rotor sides are at Mazda's minimum tolerance spec.

 

Well, 171 whp following the tuning IS weak, especially if you don't even have a cat. Also, 16-19 mpg in mixed driving is not good either... so FI on this engine might not be the best idea.
On the other hand, I'm not even close to being really knowledgeable about rotaries, so...

 

And what was your baseline dyno before the mods?
Can't tell anything without a baseline to judge from.
Weak dyno... welcome to the RX8 world...

Again... welcome to the RX8 world.

If you know whats best, why you asking?

No argument there...

 

You mean mine? It was 175 HP before the MM tuning. And I do have a cat. After the tuning, it was 190.

16-19 mpg in mixed driving is not very good either, but it is not unusual...

I'm not sure I follow you here... who said I know what's best? And what am I asking?

Thanks for the reinforcement

 

My apologies Tamas... I thought you were the OP replying to what I said.
Should have been paying more attention... was caught-up in a movie

 

the motor is done.

my weak *** mazda rebuild with 60k miles on it with the old starter does better than that..

to some extent if all things are working ie coils fuel pump. compression = mpg.

beers

 

It seems that you are about at the Mazda’s threshold to rebuild or change motor. This however does not mean that you lack of performance. The problems start at about 600kpa or 550kpa and you are not so far away.

It would be wiser to rebuild now your engine escaping a catastrophic failure that probably will make most of your motor’s parts unusable for a rebuild.

After the rebuild you can go FI.

 

Thanks for all the responses everyone.

Regrettably I've never had a baseline dyno done on the car. I've only driven my own car and a stock 08 Anniversary as comparison. Sadly the anniversary actually felt just as fast if not a little faster. The 171rwhp was done with a highflow cat on a 3" resonated midpipe, so I would guess catless would've yeilded slightly higher numbers.

If an N/A build similiar to other board members like Nemesis8, or CHR can put down 210ish rwhp I may just leave it at that. Tuned 170rwhp versus 210rwhp is a big difference, hopefully enough to keep the smiles on my face after hitting the apexes on the turns.

After all the feedback I've decided to start and save for a good rebuild. I was actually considering selling the RX8 to pick up another car but don't want to have to deal with car payments or lose out on all the work done to the car. I really wish the 09-10 models were compatible with the AP tuning... That would've been ideal in my decision making.

Thanks again everyone!

 

With all the mods will Mazda honor the engine core warranty? You're definitely within the 8 years 100,000 miles. Hope you're able to keep the 8. Also, isn't 6.9 kpa the minimum spec? If so both rotors are under spec on at least one rotor face.

 

Oh, I'm keeping the RX8... No worries there.

I was considering this route too, but from my understanding after talking to folks in the business, Mazda's process is pretty involved. The odds are stacked against me on this one. With the parts I have on the car it would work against me, so I'd have to convert the car back to stock to be able to stand a chance. Fortunately my car is still operating well, albeit weak so that would also work against me.

Planning for a customized rebuild so far seems to be the easier and more fruitful method so far. I can at least drive the car until I save enough money to get the engine replaced/rebuilt.