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Discussion Starter #1
I have posted this on another board before, but I figured id post it here to see if you guys have any ideas.

My car is not making the power it should. A stock SE-R should put around 120 hp to the ground. The first dyno run I did I had an AEM CAI, and put down about 111 hp. The dyno run is here: http://community.webshots.com/photo...80439XOjVaMGpcI . Notice the line is very shaky. The next time I went I had the AEM CAI, a Hotshot header, and courtesy midpipe (2.5 inch mandrel bent exhaust). I dynoed at around 122-123 hp with that, still very low. In an attempt to fix this problem, I have replaced my dist cap, rotor, plugs (gapped correctly), wires, fuel filter, cleaned air filter, new O2 sensor. I have also reground my MAF, adjusted my TPS voltage. My compression checks out great. My cat is not clogged. My timing is at 15 degrees. Now, here is what I think it could be. The first thing im going to do is have my fuel injectors cleaned and flow tested. I havnt really heard of anyone's injectors getting clogged, but I completely cloged up a fuel filter after less then 5k miles, so thats first on my list. Next up will be some dyno tuning. I am still runing the stock muffler, so I will do a run with no muffler. After that ill do a run with no cat just to make sure thats ok. Then I might play around with my timing some, and also run with the AF ratio probe to see if that tells me anything. If my AF is off, i may replace the FPR (fuel pump has been replaced). Im also going to pull the valve cover and check to make sure my cams are not worn. Anyone have any insights or ideas? TIA

-Mike
 

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neutral handling is cool
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When I first got my car the plugs were shot, the timing was seriously retarded and the cat was a brick. My baby dyno'd at 99 hp and 106 lb-ft. My clutch was also shot, but that came later. Since you've already done the plugs, I would set the timing at 17 degrees and use at least 91 Octane. Take a look at your exhaust, most specifically the cat. The intake gave me 5-7 hp if I remember right, but the exhaust and Hi-flow cat gave me 9-12 hp. after I got the clutch done it pumped out 7 more hp. Now I'm up to 142 hp and 128 lb-ft...there is hope. You may also want to try a compression test. The cams should be ok, you would have different types of problems other than just a power loss. Also check to make sure that you are not running rich. What kind of gas mileage are you getting?
 

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Discussion Starter #3
Highway driving i got 35.5 mpg!!! And I did a compression check. When I dynoed I tried 17 degrees and was using 93 octane, didnt help. I have checked teh cat and it looked ok, but ill dyno without one just to make sure. Keep them suggestions coming!
 

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neutral handling is cool
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I asked about the headers because they would help with cylinder vacuum to fill and remove gases, but the valves have to be behaving themselves(ie opening correctly and opening enough) for the headers to work right. If they helped 12 hp and the intake helped as much as you say, it's prolly not in the valvetrain. I could be wrong, but there's my thoughts.
 

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Discussion Starter #7
Well I didnt say how much the intake helped, and I dont really know b/c I did not dyno it before I put it on. I did hook up a vacuum gauge to see if that would indicate anything funny but everything checked out with that too. Any other ideas?

-Mike
 

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neutral handling is cool
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I misread the original post and I thought the intake had given you a decent gain. Adding the Intake, header and exhaust to my car added 25-30 hp. If you only got like 15 hp from all of those mods, you may have a valvetrain problem(worn cam lobe, oiling, etc...). What kind of oil do you use and how old is the oil pump? Also, the problem could be in the drivetrain. How does your clutch feel? When I replaced my clutch and flywheel I got 7 hp. It was there before, but I wasn't putting it to the wheels because the clutch was so bad.
 

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Discussion Starter #9
I use mobil one 5w30, but the previous owner didnt. A worn cam lobe is one of the things I was considering. If I pull the VC will I be able to visually verify this, or does it have to be removed and measured? I think its on the original oil pump. My clutch doesnt really slip, but it doesnt really grab either, like when im redlining it and shifting really quick it takes a few seconds to completely grab. But im not exactly shifting on teh dyno. Did you get a lightetned flywheel? I would think that would accoutn for the power gain unless your clutch was slipping on the dyno.
 

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neutral handling is cool
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if the cam lobe is really worn you'll be able to tell, but I would get some gauge to measure because to be safe. Make sure you have a VC gasket to replace the one on there now. The lightened flyweel isn't supposed to add power, it just decreases the moment of inertia for the clutch to engage, it just makes throttle response quicker(and boy did it). You're probably losing a little through the clutch, even on the dyno. With i/h/e I am still using a stock replacement clutch(Sachs? if i remember right). If you want the FSM pages on cam checking I can scan them and send them to ya.
 

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one more thing...I've heard that switching to synthetic after using dino oil and having a dirty engine can plug the oil pump. The synthetic cleans and deposits dirt in the oil pump was the rumor. I am still watching my engine for that phenomena, but so far it hasn't been true. Also check the PCV to make sure it ain't clogged.
 

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Discussion Starter #12
Thanks for the other about the FSM, but Iv got one. The PCV valve has been replaced. Hopefully soon ill be able to get a new clutch. Any other thoughts.

-Mike
 

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Red line chaser
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Is the cat clogged or choking off some power? Just a suggestion.
 

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Discussion Starter #14
Like I said I did visually check it, but im still not sure about it. I barely passed emissions (by one point, hehe), and I can smell a sulfur smell if I get on it really hard. Thats why I plan on doing a dyno run with no cat. Get those ideas coming!!!!
-Mike
 

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Discussion Starter #16
Hmm, i guess ill add that to the list. Maybe I can rig up a voltmeter thingie to it and wire that inside the car so I can check my MAF voltage. Anyone know off hand which wire I need to use to do that?
 

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Other than a possible worn camshaft, I'm out of ideas.
 

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mpg9999 said:
The dyno run is here: http://community.webshots.com/photo...80439XOjVaMGpcI . Notice the line is very shaky.
-Mike
Mike,

the link you gave goes nowhere. Recheck and post a valid link.

Usually, shaky power output (depending on HOW it shakes :)) indicates a power cut due to the knock sensor indicating detonation. I noticed that you did not check the knock sensor. Do it. If it is OK then you probably ARE detonating and you need to track the cause.

Chris
 

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OK, this one works.

Now, your diagram DEFINITELY looks like your ECU is continously retarding the advance due to detonation. There may be other causes for such a curve but I have seen the exact same curve on a detonating car. Check your knock sensor as per FSM and replace it if necessary (or get one to check it with and keep it as a spare).

Again, this behaviour may have a lot of causes. The wildest I ever heard (in some forum or something) was a car with very dirty sparkplug cables that caused interference between two adjacent cables thus waking the knock sensor up. Another person (check Nissan Performance Online Magazine in Sentra.net for a procedure on cleaning the cylinder with carb cleaner) said there was a lot of carbon deposits on the top of the pistons and it detonated until he cleaned it up.

Best of luck, keep us informed on results.

Chris
 
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