is this feasible or am i wasting time and money trying to improve an already excellent package...headers, 200 cell cats, ECU tune...

 

I am satisfied with my X51, but the 200 cell cats seem to free up a pretty fair amount of power. Not sure if you will need to repro the ECU for that change, but that is something I personally would be hesitant to do.

My other suggestion would be to concentrate your dollars on the suspension side of things and leave the motor alone.

 

you've got a point there, i am tending towards the same, thinking pss9 or 10, i have pasm so i think that limits my options...thanks for the reply,

 

You will notice some improvement with sound and butt dyno with 200 cell cats. The x-51 headers are about as good as you can get for the 997. The pss10's are awesome with the pasm. One other mod you might consider is a ecu tune.

 

The X-51 headers may not be the best for the 997 series. If you can get them for < $1000, then yes they are great values. With them going for $1200 now, there are other headers that can give you better mid range and top end pull for a few hundred dollars more.

Talk to Rhonda @ FVD. I believe she has Dyno numbers for X-51, Fabspeed, and M&M (FVD) headers.

In my experience, I had the X-51 headers prior to changing them to M&M headers. I can honestly say the the mid range pull is more pronounced now and the top end does not feel as choked. I actually got squirly in 2nd gear WOT pull, which I have never experienced with the X-51. Granted, I have a VF-Engineering SC, so the squirliness may not occur with your package, as it did in my case.

 

so what is it that changes efficiency of headers exactly, equal length, diameter, shape/bends all play a part i guess, and most of my driving is daily stuff, i go to the ring maybe twice, 3 times a year, but don't really push it, so my interest is more in the lower end of the ranges. looking at these headers they have a really clean even length look, and i wonder at the spagetti looking twisties and where is the advantage of those...

 

Here is what I have done to my X51 997

1) BMC Filters
2) 200 cell Cats
3) Softronic Tune
4) RSS Crankshaft Pulley

 

and what is the RSS crankshaft pulley and what does it do? i haven't heard of this...do the BMC filters change the sound at all? and what about throwing codes with the 200's, any problems...i have heard both for them

 

RSS pulley underdrives your accessories to free up more engine power.

https://www.6speedonline.com/forums/...067&styleid=28

BMC panel filters increased the sound slightly. My 200 cell cats did trig the CEL but Softronic tune eliminated it.

 

You are correct in all aspects of header design. What differentiates the X-51 vs Fabspeed vs FVD are all that you mentioned. Fabspeed and FVD designs also incorporates the F1 style collectors. I think this makes a difference in the efficiency of the headers. According to Rhonda, the FVD long tube headers that I have are designed for max TQ, similar to Fabspeed, but somewhat more improved, per Dyno.

In my experience, the pull is noticeable from 3000 to 5000. I feel this is mid range power that I can use during my spirited driving.

 

Interesting. I need to look more into this.