Who as experience playing around with a dyno and headers? What are some of the proven limits of the stock setup once you start adding power?
Sorry if this should be in tuning, but I though it was a bit more hardware related.
Reason for asking:
I do not have easy access to a dyno, and I recently switched to a one piece header uppipe combo. Probably is a Megan Racing cheapo kind of deal. I have a fair amount of upgrades and run E85, self tuned, but this discussion does not need to be my setup specific. I'm thinking about going back to stock headers. (mods listed at bottom)
My seat of the pants feel and experience switching:
-Switched to the one piece (presumably - unsure of source) Megan Racing Headers.
-Immediate butt-dyno, without modifying tune, feels significant. But the data log numbers didn't drastically change.
-I expected top end to flow to be better, but I'm struggling to get the same boost as the stock headers above 5k rpm. This seems counter intuitive?
-The stock headers hold heat much better, being cast and heavy. I'm not sure if this is playing a significant role. The MR headers are kinda thin feeling, and many posts emphasize the role of heat preservation in the headers.
-There is a noticeable difference in sound. The OEM headers have that nice deep UEL sound, and the UEL MR headers sound closer to EL headers with a more subtle 'rumble'. Also I am experiencing a harmonic vibration at 2500 rpms which I think is a lack of piping flex between heads(all solid tube). Whatever- small point.
My relevant mods:
VF52 turbo (by JP from this forum) with the lighter weight compressor wheel. Very similar characteristics to a 16G wheel.
ID1000 Topfeed Injectors, DW65c pump, OEM STI FPR, and custom fuel lines.
Tune: Running 11.5 Afr on E85 up to 20 deg timing. 19lbs(3200rpm) to 15lbs at redline. MAF g/s top out around 290 (for whatever that is worth)
Catted COBB down with 3" Borla catback.
GS 3port EBCS
Fresh block and head rebuild. Forged 2618 pistons. Rebuild Log Link
So have I outgrown stock headers, should I throw them back on?
If no opinion on that, what are your other experiences?
As always, thanks for taking the time.