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YOUR RESEARCHX51 oil pan and 997S X51 headers installed
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Install previously
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Performed · outcome unconfirmed · Original poster
I believe I all ready must of had less back pressure since I've had the fabspeed mufflers installed previously.
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Suggestion
I was talking to my tuner and he told me that if I upgrade headers, which is what I am thinking about doing, he will adjust the ECU mapping again to be even more aggressive with the timing given the new increased airflow.
Leading evidence: 'Install previously' (no explicit attributable resolution; this is a reported action or suggestion). Across 1 matching discussions, The most frequently discussed action is 'Adjust ecu mapping' (1 discussions). For that action, 0 discussions report a resolution and 0 report an unsuccessful attempt. No action has an explicit, attributable resolution report under the current rules. These are forum reports and suggestions, not a confirmed diagnosis.
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Suggestion
I was talking to my tuner and he told me that if I upgrade headers, which is what I am thinking about doing, he will adjust the ECU mapping again to be even more aggressive with the timing given the new increased airflow.
Explicit resolution reports before identified causes, performed actions and suggestions. Within each level, matching component labels precede direct query mentions and inherited thread context; successful versus unsuccessful discussion counts, owner confirmations and independent discussion support determine order. This is not a probability of success.
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Suggestion
The X51 headers must be working as my service tech always had a smile on his face when he returns from a test drive.
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Adjust ecu mapping
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Suggestion
I was talking to my tuner and he told me that if I upgrade headers, which is what I am thinking about doing, he will adjust the ECU mapping again to be even more aggressive with the timing given the new increased airflow.
Counts describe captured discussions, not unique people or a diagnosis. Author identities are not reliably stored. Exact duplicate evidence is counted once across matching discussions; one discussion counts at most once per action/state. Multiple repairs reported together remain a combination. Suggestions and failed attempts do not establish a fix. Matches cover whole discussions and can include related faults, model variants and incomplete threads.
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Generation: 20261026T220748Z · outcome-qualification-6. Deterministic extraction; no AI model inference. How we use sources
Link to X51 pan
The headers fit great, no issues. Visibly a lot larger then the skinny things that came off.
The car does feel slightly more torque then usual. Sound seems a bit more deeper.
Before installing the headers I had
evo air intake
fabspeed max flow exhaust
and GIAC chip
It's funny that you say that it feels like you gained some torque, and yet the diameter of the X51 headers is larger than what you took off. An increase in header diameter results in LOWER torque.
Did you take the time to clean up the X51 headers? The insides are pretty sloppy from the way they welded them up. I took the time to clean them up a lot before I put them on my 997S. Here's a before and after shot,--and the tools it takes to clean up the insides of these headers.
I just got my ECU flashed last night. The throttle response is much crisper and more engaging. I drove it like I stole it for 30 min to have the ECU adjust to the new fuel mapping. I did not pay retail on it and don't think its worth that much. However, it is a good mod at 50% of retail. I was talking to my tuner and he told me that if I upgrade headers, which is what I am thinking about doing, he will adjust the ECU mapping again to be even more aggressive with the timing given the new increased airflow.
You may want to see if you can go back to GIAC to have your mapping readjusted.
I believe I all ready must of had less back pressure since I've had the fabspeed mufflers installed previously.
I noticed the car feels like it has more go in 2nd or 3rd at 4k rpm which I thought was torque. Could be my imagination though.
I guess I'll really know once I get to the track and get a chance to see if my speed down the back straight has increased or decreased.
chsu74 - I'll ask my shop about that. Thanks for the info.
Very little gets taken off in this process, but it significantly cleans up the air flow path. Interestingly, the original headers were much cleaner inside than the X51 headers were.
Here's a side by side shot,--but recall, those were taken off a 3.8 M97 engine.
The stock headers are truly abysmal, I don't get why they did it like that--unless it was an easy way to get a bigger power gap out of the higher end models.
Anyway, freer flow will net you higher hp, but it will be at higher rpm. Low down in the rpm range you'll lose some torque, but really not enough to be noticeably detrimental just swapping out the headers. Besides, great excuse to spend more time above 5000rpm.
I wish I knew the specifics of why all that is.
It's all about exhaust velocity and scavenging. Mike Kojima, who is very well-known in Honda/Acura and Nissan communities as well as NASA racing, explains this in his
book
. Google doesn't allow copy'n'paste of text (for obvious reasons), but I found another
source
where he pretty much states the same thing.
And if you doubt his credibility, Mike Kojima has been around for many many years, particularly in the 300ZX TT, Sentra SE-R, and Honda/Acura communities. He's an engineer at Nissan to boot.
The point is to not blindly increase exhaust pipe diameter, but selecting the correct diameter that lowers backpressure w/o sacrificing exhaust velocity. So depending on how bad the stock exhaust is, it is possible to have your cake and eat it too, that is go w/ a larger diameter exhaust pipe to lower backpressure, but still maintain exhaust velocity.
///Michael
Precisely my thoughts as well! And the reason for the changeover to the M97 X51 headers.
I believe the M97 3.6 headers are quite nice (essentially M96 engine part). I have no idea what they were thinking when they welded together the M97 3.8 headers!
The X51 headers must be working as my service tech always had a smile on his face when he returns from a test drive.
At least the stock 996 headers are a design that is similar to the X-51 headers. The stock 997 headers look like something you would find on a 6 cylinder Honda!
WTF is with that stock 997 thing.... that looks like a plumber designed it, not a high performance exhaust flow engineer ??
is there some "new math" in determining the length of pipe needed... the middle seems a "bit short" of the 2 ends????
I think the stock headers on 3.6l 996 have an outside diameter of 42mm while the X51 headers on the 3.6l 996 have an OD of 48mm - I know they have a different part number - don't know about the 997.
I was told that the reason X51 headers are inexpensive because they are cheaper to produce. Typically, you would want the pipes to be the same length out of the engine into the cat for optiminal performance. That is why Fabspeeds are $1600 new compared to the X51s.
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