Really doubt the PLM is any better than a real designed header, and even if it were its not THAT much better. Something else is up here. What kind of header are you using, are you sure it's the right design for your setup? Scavenging and speed of exhaust gasses are a lot more important than any brand name. You said your new Hytech is a big tube right, but your PLM was a standard tube? I would say that is more significant to the power issue than whoever made either header. Your particular setup probably cannot take advantage of your new header which means it's not the right part for your setup. There is such a thing as too much flow when it comes to intake and exhaust systems. (Think putting a Victor X on a stock GSR) When it comes to header designs for customers, we like to keep it simple unless the build is so extreme that an extreme header design is warranted.

 

extreme? Can you educate me a little? What do you consider extreme? how do you determine the length, size, megaphone etc? I'm trying to get a better understand behind building a header that will make peak horsepower.

 

Then how did it make 245whp on the same motor with same header in another car, mine having better parts?

 

You can't compare a motor as apples to apples. If that were the case we would all hop on here, find a build thread we like, copy it, and know what to expect...not the case.

Dyno 10 2015 civic Si's. All stock. All off the showroom floor. There will be a percentage of difference across the board although they all are "identical"

If we were talking a NASCAR or F1 motor here then there would be little validity to my statement, BUT we aren't These are mass produced motors and products. They all have variances.

 

My point is this exact engine made 245whp, has never been broken apart internally since. Not copying a build, but in fact the same exact physical engine.

 

Ahhhh now I'm following. Same dyno? Same exhaust? Same weather? Same Tuner?

 

Yes the chart I posted above from corr was the exact dyno it was dynoed on before when it made the 216whp. Now it made 197. Exact same 3 inch aluminum exhaust, weather was similar, but accounted for in the correction of the chart, and different tuner.

 

Out of curiosity, when you were getting your "custom" header built what was your goal? Did you give them your motor specs? I went for a useable power range, not caring about peak HP #'s.

 

Wilka, Im not familiar with either header, but which header has the longer primaries?

 

Both about the same.