I am so unbelievably happy with my car... oh my god. It's amazing. If you do not have a turbocharged RX-8 you don't know what you are missing. Now that the car is running well, I'm finally getting to see the payoff for all of the hard work and money. Driving to snag fast food with my wife tonight was crazy, turbocharged cars all over the place, BOVs venting to atmo, an NSX roaming the streets... I don't know if there is some event going on tonight, but it was like a freaking Fast and the Furious opening night.

 

now you can stop worring about your car and start worrying about your licence LOL

 

Yeah, there is some truth to this... I do have to say that 300 whp is a surprising amount with a car as light as the 8. I'm planning to put the car on a diet next, and shed some weight and turn the boost up a bit, but not until I'm comfortable with the power it has. It's pretty damn fast as is now. If the car had released with a turbocharger option I think we would be seeing RX-8s all over the import community. It makes the car absolutely perfect.

 

Well the car was driving great yesterday, but today I was having some issues, it seemed to be too rich again in certain areas. I went to do a 1st-3rd WOT pull to get logs for Jeff and got a weird stutter and loud bang. I saw AFRs were lean so I backed off immediately.

The car continued to drive alright after that, no noticable loss in power or anything, but I pulled into a gas station after that to fill the car up and had a tough time starting it, taking several cranks to come up.

I pulled the logs off the AP as soon as I got home and looking through them I found one really nasty section:

Seconds (sec),Coolant Temp (° F),Equiv. Ratio (AFR),RPM (RPM),Intake Temp. (° F),Engine Load (%),Long Term FT1 (%),Mass Airflow (g/s),Short Term FT1 (%),Rel. Thrott. Pos. (%),Vehicle Speed (mph),Ign. Tim. Lead. Coil (°),Ign. Tim. Trail. Coil (°)

5.80,183.20,15.14,6440,91.40,117.21,-0.16,198.29,-0.16,29.25,30.45,27.00,12.50

5.96,183.20,14.85,6724,91.40,112.90,-0.16,203.44,-0.16,29.25,31.07,28.00,13.00

6.13,183.20,15.88,6853,91.40,117.21,-0.16,235.16,-0.16,30.03,32.31,28.50,13.50

6.30,183.20,15.88,7186,91.40,114.86,-0.16,234.68,-0.16,26.91,34.18,28.50,13.50

I've already sent my logs from yesterday and this log to Jeff to take a look at, but at that load and in lower gear with methanol I'm hoping this didn't cause any damage. Is there anything I can really check?

 

loud bang?!
uhhh, that's no bueno.

 

Doesn't sound good. Any change in exhaust note? Or idle? Or vacuum at idle? That's a good indicator.

The good news is your grams/sec were pretty low so you weren't making that much power...

And if it has a hard time starting and or holding idle then that's the kiss of death.

You can always get a compression test to be sure but it may be premature at this point. Did you hear any marbles in a can?

 

No marbles in a can, the next time I started it it came right up. No problems with idle at all... it did seem the idle vacuum was lower though, but I wasn't 100% sure where it was at before.

 

Just went and started it up fine, exhaust note sounds the same as before, no issues with idle, very smooth 6-7 g/s and 14.7 AFRs in idle. Vacuum is -12 or so at idle, I -thought- it was a tad lower than that before, but as I said, not sure. No real signs of blown engine, but scared the living **** out of me.

 

starting well is a good sign but the vacuum not so much if it has dropped from where it was before . Better check compression just top be sure ....

 

Have you done a pressure check to make sure you're holding boost? If you have a leak somewhere it could be adding to these inconsistent days you're having.

BTW I think I passed Brandy yesterday on 175, couldn't see if it was her driving though.

 

/\ good point . Blown coupler ?

 

I don't see one, but its possible. The car is still pulling strong in 3rd-6th... and AFRs in those gears even in WOT are fine. I don't know... really upset because I don't know.

 

The other possibility is a large backfire . Did the bang sound like it was underneath or up front ?

 

The bang was definitely a backfire, it was not from the engine, I'm sorry I should have clarified that. It was not the throaty rich fuel backfire though, it was a very loud aggressive single bang!! backfire.

 

Could have been a serious misfire...

Idle vacuum of 12 is kinda weak....I pull 20-22" at idle. That would worry me.

Are you still hitting 9psi (or whatever your max boost is?). That would let you know if you have a blown coupler/boost leak.

 

With my rough tune I get alot of backfires...but never under throttle. Always happens in off throttle situations. If I"m cruising at nuetral throttle and let off I get a good "pop". If I'm hard on the throttle(and into my richer part of the map) and let off I get a pretty good "BANG!"

 

Do you run a VTA Blow-off valve? Because that will do it, un-metered air.

My BOV is currently VTA so I get good pops, bangs, fireballs, etc.

 

Newp, its recirced. I'm just running pretty rich and my exhaust is very unrestrictive

 

The bang was when I let off, not in WOT. It was a single bang, and VERY loud. I have only ever seen 22'' vacuum when I go off throttle (and it still does that) but not at standing idle. That has always been higher, like 15''ish.

 

OK so the bang was just a large backfire so nothing to worry about (once you changed your undies ).

The low vac at idle is an issue . You could check all the vac lines on the UIM .

 

The vac has never been lower than 15'' at idle even before the turbocharger so I'm not sure about that. I can definitely check the couplers and see if there is anything funky. Yeah, my undies REALLY need changing after that.

To clarify, on throttle off, its 22'' or more, and boost seems to be steady up to 8.5 psi etc...

 

Oh how I do not mind the back fire from my car WOT.

 

Good way to check for leaks in the intake (assuming you don't have a compressor).

*Take off the coupler just after the maf .
*Put your vacuum cleaner on blow and stuff the nozzle with rags wrapped around it to seal it up into the tube .
*get spray bottle with water and detergent in it and spray all your joints .

you may be surspised at all the little leaks you will discover doing this .

Pay particular attention to your UIM . If your vac is weak at idle a leak there would explain that .

 

Aaron- I've got a compressor if you want to test. We would only need about $5 worth of stuff from Home Depot.

 

15" is OK, but not amazing or anything. I pull 20-22" of vac at idle....off throttle is 28". But I'm convinced I have a freak motor.

If it's starting right up without failure and the exhaust sounds good, then I vote you're safe. It may have just been some slight detonation.

If you hard the Bang with your foot in the floor then this would be a different story. Hearing a backfire while letting off is completely normal.