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My Speed Engineering headers showed up today and I'm trying to decide where to position the "X" of the X-pipe. As you can see, the X-pipe is built with the "X" pretty far back (where it would be if it had CATs). Since I'm not running CATs, I was inclined to cut the two 45 degree pipes (that connect from the header collector to the X-pipe) and in turn shift the "X" forward. This would get the crossover closer to the collector and (I would think) improve performance.
As designed:
Moved forward:
I'm guessing that this (and all other) LT header kits have the "X" pushed back because they are all built to handle CATs (even if they don't get them... on size fits all). Ideally, I would install the headers without the X-pipe (install straight pipe in its place) and use the crayon method to determine the ideal location of the crossover, but that would mean I'd have to go buy pipe for a single test use (which is rather wasteful).
You are correct that moving the X pipe forward will improve performance HOWEVER the gain is be so small and realised at such a high RPM that it will be unnoticable for most driving.
What the X pipe will do is create more of the "scavenging" effect, whereby the exhaust passing through the X slightly "pulls or sucks" the exhaust pulse from the other side of the engine. Additionally, it will change the exhaust note of your car slightly dependant on your mufflers.
If it were me, I'd just leave it as designed and put it on as your headers are your biggest bang for your buck. But really this is a "personal taste decision."
I'm planning to just pull the X as for forward as I can and still retain a clamp, I have to believe that will help on some level.
It looks like doing this, I can move the X a good 18" further forward. This should also allow me to install a pair of long, round chambered mufflers/resonators after the X if I choose to do so (adjust tone/volume).
In the early 90's. NASCAR saw the first use of the X-pipe when one of their members had a Talladega moment and went airborne upside down. Rusty Wallace had it first on his car and they were able to make a 650hp NASCAR engine make 7-10 more hp as a result In NASCAR that meant another 2 mph which is huge going down the straightaway, the next race almost everyone had one. Today it is part of the engine exhaust system. If it is not right after the headers it is only for the scavenging the exhaust.
In the early 90's. NASCAR saw the first use of the X-pipe when one of their members had a Talladega moment and went airborne upside down. Rusty Wallace had it first on his car and they were able to make a 650hp NASCAR engine make 7-10 more hp as a result In NASCAR that meant another 2 mph which is huge going down the straightaway, the next race almost everyone had one. Today it is part of the engine exhaust system. If it is not right after the headers it is only for the scavenging the exhaust.
So, you are saying try to get it as close to the collector as possible?
You can theorize all you want, but for your motor I would still do the paint method...it costs you what <$50 in some tubing from your local exhaust shop??
In reality, this is all a moot point if you don't dyno the car before AND after this change. Same dyno with similar conditions to keep variables to a minimum.
The paint/crayon method would be best, just have to motivate myself to go get the tubing.
Definitely not interested in doing a before/after dyno. I couldn't care less what the actual number is (I'm way past the age where having dyno numbers matters to me), I just figure if I'm installing something and I can make a relatively simple adjustment to improve it's results, why not.
Then you might as well just toss the x pipe anywhere you want and be done with it...
Without a datalogger/ dyno pull or track runs you have no way of proving it works any better.
Well... that's almost like saying don't install headers unless you get a dyno run before and after. I know there's going to be a power increase, don't care exactly how much.
He won't be able to prove it's better, but may as well put it in the most optimal place by consensus/proven methods.
Well... that's almost like saying don't install headers unless you get a dyno run before and after. I know there's going to be a power increase, don't care exactly how much.
He won't be able to prove it's better, but may as well put it in the most optimal place by consensus/proven methods.
Exactly.
There's an optimal location for the X-pipe. I doubt I'll be able to get it truly optimal as I don't want to completely hacking up the x-pipe (too much work for the gain), but if I can get it "closer" without a lot of effort, that's better than leaving it where it is.
Last edited by ChrisLSx; Oct 30, 2018 at 02:01 PM.
Well... that's almost like saying don't install headers unless you get a dyno run before and after. I know there's going to be a power increase, don't care exactly how much.
He won't be able to prove it's better, but may as well put it in the most optimal place by consensus/proven methods.
If you install headers without getting to the dyno or a datalogger for street tuning then I can't help you...either way you know the headers are a benefit from power increase via dyno and or through data logging fuel trims/MAP readings for street tuning etc.
What I said still stands...toss it on there and call it a day
Seems silly not to take the little extra effort to determine the placement rather than guessing (regarding the paint trick not the dyno).
Last edited by smitty2919; Oct 30, 2018 at 02:48 PM.
Seems silly not to take the little extra effort to determine the placement rather than guessing (regarding the paint trick not the dyno).
Agreed. Won't take me much effort to try the paint trick. I still doubt I'll be able to get it far enough forward to be "ideal" but something has to be better than nothing (perhaps I'll surprise myself and the paint will show it needs to be back further than we are expecting).
I'll use my wide band to tune it, it's just not worth the time/effort/money to dyno before/after as it can't be more than a few HP (I'd guess there's more variation based on time of day/weather/etc.), particularly since I'm not looking for dyno numbers. My car is just a fun daily driver so whatever it makes, that's what it makes.
If you install headers without getting to the dyno or a datalogger for street tuning then I can't help you...either way you know the headers are a benefit from power increase via dyno and or through data logging fuel trims/MAP readings for street tuning etc.
What I said still stands...toss it on there and call it a day
Seems silly not to take the little extra effort to determine the placement rather than guessing (regarding the paint trick not the dyno).
Don't recall anyone saying no tune after, just no tune before (to measure gain).
where to position "X"-Pipe
Then you might as well just toss the x pipe anywhere you want and be done with it...
