Why no more power???
 

Like the title says, my car has recently developed a power problem. I drive a 1999 miata with an MP62 supercharger (please don't hate, I bought the car like thathttps://www.miataturbo.net/attachmen...ine=1344310736).

Here is my problem: A week ago I went shopping and when I came back and started the car, a new rattle started. It sounded like rocks in the exhaust. Then, after the engine was hot, I tried a WOT pull and i noticed it lacked power considerably and I could hear what sounded like a boost leak... when I arrived at my house, the rattle had disappear but the engine still lacked a lot of power.

Since then I've checked all vacuums for leaks, I took off the s/c and it was in perfect condition as was the bypass valve, checked the timing, the engine compression, took off the intake manifold to make sure there really was no vacuum leak and checked the piggyback, still for leaks. I have just taken my exhaust off to see if my catalytic converter was broken but I can only see the intake side of it and it is not clogged and the exhaust doesn't rattle when I gently hit it with a rubber mallet.

Tomorrow i'll try to run it straight pipe after the down pipe to make sure that the catalytic converter is not clogged.

Does anyone have a clue what i could be? Cause I don't....
Any help would be very very appreciated!

nhot great if true but rattle of rocks sound could be serious detonation problem.....

What AFR does it run at at full throttle?

2 questions, whats the boost gauge say and what does the AFR gauge say during boost?

If you cant answer those 2 questions, then FIX those 2 issues and then worry about your wot power.

What was the compression and did you do a leak down test?

Compression on hot engine was 1-200 2-200 3-200 4-201
Don't have a boost gauge...
Don't have AFR gauge...
Didn't do a leak test...

But I do have OBD2 and on such detonation levels I am pretty shure a CEL would have appered. I also heard the rattle at idle and now that it has disappeared the engine has the same power issues.

Wait, how is this tuned...

Buy a wideband O2 sensor and gauge before you drive the car again. There is absolutely no excuse for you not to have one. I am guessing you are going lean and detonating.

Guys,

I have a car. It has problems. I don't want to do anything to monitor its vitals, I just know that recently it started making a noise.

Please help me.

Thanks

or when the SC goes...

Well the stock computer has no idea what the hell boost is nor does it know what to do with the timing at all. Don't be so shure that it would toss a cell especially since you're running tons of bandaids to confuse the sensors in the first place. While i was tunning my turbo with the xede before i finally got the balls to go standalone i heard it ping because of lean more than once and it never popped a cell. Speaking of lean it has no clue how much fuel to add...worst yet the narrow band will not show what afr you're running. Hell you could be at 13.5 afr at 8 or 10 psi, 22 some degrees of spark and the stock computer dont give a ---- and since you have no gauges you have no clue either. :facepalm:

Guise!

Car!!!

HALP!!!!

Does the car have a cat converter on it?
nvm it does
Take it off and test if you have a straight pipe or with it off

The DET sensor will pick up on the knock and ping. It will tell the computer to change your timming around. Becareful, this will cause you to be late everywhere you go.

https://www.miataturbo.net/attachmen...ine=1344388795

welcome to miataturbo bro! it's like totally sweet. Don't worry bro we drive fag cars it's supposed to not have any power bro.

I bet the cat is clogged, most of the time if the cat is clogged it will turn cherry red ofter a good drive. Take it around the block (around a big block) and take a look under the car.

Another way to test is put your hand at the tail pipe and check for exhaust flow.

/\ Listen to this guy. He's a professional. If you can't feel it with your hand, stick your balls in there

Now only if you can do that while going 30-50 mph at wot.

It helps if you have floppy balls.

Sorry mine aren't too floppy so i've never tried that but can you use them as parachute during drag racing?

On my M3 I had a ceramic cat break up and it sound like rocks in the exhaust. I just banged on it with a rubber mallet and could duplicate the sound. After I removed it, a piece had blocked the pipe down stream.

Mine aren't that floppy either so I tried the no exhaust ride instead. Results are that it was so loud that it felt it had a lot more power then it actually did so I'm not sure if the exhaust was clogged or not. I will continue to investigate until I decide to buy the wideband and boost gauge (and maybe MS2) but in the meantime here is a little video of the car when it was working great:


Thanks for your help!

Wait wait you're RACING this car with no wideband or boost gauge? :facepalm:

This will surely end well.

Expecting the "there is a lot of smoke out the exhaust and it sounds like a subaru" post in a week or two.

Alright guys, the car has 180 000km and has perfect compression. It has a Powercard - yes I know it is far from the best management - to control the injection. The ignition is still OEM and if detonation is detected there is a knock sensor that will retard ignition timing. For the boost gauge, well this is no turbo, there is no wastegate. The only way to change boost would be to change the pulleys and I am pretty sure that it won't happent even if i don't have a boost gauge. The wideband would be nice but with the narrowband I am supposed to be at 14.7 on the whole powerband and that's it. I know it is far from the perfect setup but it at around 7psi this is not an agressive one.

Holy christ thats why its slow. You DO NOT want to be at 14.7 when in boost. Jesus ------- tits in a scrotum, richen that baby up and buy a god damned wideband for tuning.

The problem is your blown motor. replace it an you'll recover your lost power for a while.

Did you remove and inspect the catalytic converter for broken ceramic blocks or not? If you don't see any that look broken then the pieces are all in your muffler now or stuck at the elbow in the exhaust pipe. That's why the rattle stopped.

You are not supposed to be at 14.7AFR on the whole powerband. At max boost you are supposed to be at 11.5-12.0AFR. You need to buy a wideband 02 sensor and gauge now. Then you need to see what exactly you are running for AFR's. If you run 14.7AFR in boost you will cause your motor to explode.

.

Weak coils are probably the single most common issue with 99-00 miatas. A weak coil will then kill your catalytic converter which cloggs and robs even more power.

I have removed the "middle pipe" witch has the catalytic converter and resonator on it. Both are welded together so I can only see the side of the cat where the gases enters and it seems perfect. It has been raining a lot these days so I can't work on the car very much but the muffler makes a ratteling noise when I hit it with the rubber mallet. I will investigate more when the sun finnaly comes out.

I will probably buy the wideband soon if all else fails.

Thanks for the help!

NO!!!! You need to order the wideband TODAY. It is not safe to drive a car with forced induction without being able to monitor the AFR's correctly. If you can not afford a wideband currently then stop driving the car until you can. Because if you can not afford a wideband you most certainly will not be able to afford a new engine when your current motor blows.

When they check you out at the register for the wideband don't forget to get a side of motor.

Most people do a facepalm just on the internet... I'm doing a face palm in real life while reading this.

Found the problem. Catalytic converter was broken. It's empty now and everything is back to normal!

Thanks!

In for the blown motor thread.