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EP3 Ep3 down on power, what to do next?

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My ep3 is down on power between 15 and 20 bhp between 7 and 8k rpm, and around 5 to 10bhp down around 4 to 5k rpm. The car is being helpful and showing no codes The car is not misfiring, stuttering or feeling sluggish. It's had a new timing chain, tensioners and guides, a remap so all fueling etc should good. It doesn't use much oil, perhaps half a litre per 1k, and no regular smoke. The valve clearances I did last summer and I understand they don't need adjustment after a new chain? Checked the spark plugs which were a little white, I haven't checked coil packs or injectors. Recently changed the vtec solenoid gasket. Recent oil change too.

My thoughts are the cat could be plugged or there is some other restriction? The fact it shows no codes makes me think all sensors are fine, TPS for example.

Not sure where to go next and in which order. Is there any test I can do to check exhaust flow?
 
No, the chain was stretched though about 3/4 of a tooth. Power didn't change much. Strange thing is the car seemed a lot more punchy yesterday morning on the way to work but seemed normal again on the way home.
 
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Thought everybody came to the conclusion that it was the Cat?
By the sounds of it you have checked and changed everything but that!

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I'd wonder about the injectors, and I guess it's semi-easy to visually inspect the spray pattern at the very least.
 
I'm still on the side of it's either the cat or that's the power the car wants to make, 10% difference in cars isn't that surprising. Especially taking into account age and different rollers.

If you like the way the car feels now post remap just enjoy it. To me it sounds like it's fine.
 
Trouble is although it's thirteen years old now most of the ep3s once modded make similar power for the mods added. For catback and induction kit it should be in the 215 to 220 bracket, most seem to manage that. I'll plug my obd2 in later, is there a reading that will pinpoint emission problems to highlight if it is the cat?
 
Trouble is although it's thirteen years old now most of the ep3s once modded make similar power for the mods added. For catback and induction kit it should be in the 215 to 220 bracket, most seem to manage that. I'll plug my obd2 in later, is there a reading that will pinpoint emission problems to highlight if it is the cat?
Yeah but is that with the same guy, you can do all sorts of magic to get whatever number you want to appear on a dyno. I would be looking to make sure you're happy with how it drives, does it feel stronger all the way through the rev range? Is it knocking / going to explode. If you can get an answer that pleases you for both of these then it's money well spent.

You have already said you don't want to be messing around with decats etc so you're never going to make huge amounts.

I just think all this extra time and effort you're ploughing in could be used elsewhere. You won't feel the extra 10 horses even if you get them.
 
I agree with what you're saying and it does drive nicely, but I'm concerned there may be an underlying issue. I'll see what the fuel trims read later.
 
Coil packs checked and fine.
Injectors screwdriver test done and fine.
Obd2 scanned, no codes.
Fuel trim around 1 to 4% on tick over.
IAT 42°C :p I replaced the sensor and it dropped to 32°C.
All o2 sensor and catalysts checks came back "passed".

Hmmm.
 
Did the tuner notice the IAT reading to be out while mapping? It's hard to know what's causing it, lack of power with no fault codes would generally be inlet or exhaust in my experience.

Is there anyway you can unclamp the manifold to cat joint and try and get a bit of a gap between them, this would show if the cat is blocked, but I'd expect that to cause a more severe lack of power to be honest than just a bit of a flat spot at the top end of revs.

Again, the tuner would have noticed any lack of fuel by the duty cycle of injectors. Have you seen any other stock cat dyno charts to compare at all? The cat just be limiting power, but I'm not sure at what point and how obvious it would be.

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He did say that the IATs were high, I'm starting to think if the sensor is reading +10°C higher than actual temperature then less fuel would be introduced than should be, hence leaner conditions, reduced power and signs like white spark plug residue (mine are like that).
 
On my first fn2 I was in a similar predicament with the car not making the power it should.

It had all the bolt on's (rrc, hks rsk, tegiwa exhaust manifold, toda catback) plus the tdi north stage 1 cams. Made 230bhp where others where making over 250.

People said numbers don't matter, pub talk blah blah blah but to me they did. They mattered not because of the pub talk (I don't go to the pub) but because it was a clear indication that something wasn't quite right with the car.

Never quite got to the bottom of it but we thought it was down to the compression. Had the car compression tested and it read around 175 on all four cylinders. Don't quote me on it but I think a k20 should be around 220, hopefully someone can confirm.

Maybe worth getting your compression checked.
 
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On my first fn2 I was in a similar predicament with the car not making the power it should.

It had all the bolt on's (rrc, hks rsk, tegiwa exhaust manifold, toda catback) plus the tdi north stage 1 cams. Made 230bhp where others where making over 250.

People said numbers don't matter, pub talk blah blah blah but to me they did. They mattered not because of the pub talk (I don't go to the pub) but because it was a clear indication that something wasn't quite right with the car.

Never quite got to the bottom of it but we thought it was down to the compression. Had the car compression tested and it read around 175 on all four cylinders. Don't quote me on it but I think a k20 should be around 220, hopefully someone can confirm.

Maybe worth getting your compression checked.

I was about to write a paragraph of the above on your civinfo thread but mebz has it spot on.
Check compression first to gain an idea.

If the curve is flattening out up top it sounds like a high rpm restriction so I'd be checking fuel pressure / injector duty along with air filter cleanliness & the high possibilty it's the cat. After that it's highly likely just down to engine health overall.
Classic signs of the cat would be lower losses in mid-range with larger ones up top as you're showing. This was prevalent when I went to a decat then sports cat then back to decat.

A +10c IAT wouldn't be much loss in bhp; my summer-winter dyno reads were within 1-2bhp.
 
If compression is low do you know the causes and how to cure it?
Injector duty was only around 74%.
With the IAT it's not so much about the small power loss due to being warmer it's down to the sensor fault which would cause an imbalance to the afr. The ecu thinks it has less air so adds less fuel where in fact it has more air.
 
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Like many of us have said previously it will be the cat. Change it and it will be all sorted. I did post on here a decent OEM ep3 cat for sale on eBay last week but I believe this has been sold now.
 
When I did a compression test on mine I achieved 175 across all 4 cylinders, but I forgot to WOT :picardfp: If I had wedged the TB valve open I anticipate the readings would have been higher.
 
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