... Thanks! It's been a lot of work these past few years, lots of preventative maintenance to take care of in these middle years here as she rolls over 175k miles now!
I have now had this vehicle for almost 90k miles, just incredible to me at least! I'm just getting in to the super fun mods now that I've got it all paid off and its starting to get rust badly everywhere. So some rust fixes will be needed, especially to the frame rails. Need a solid frame first before doing anything else, otherwise it's just a waste.
Bull bar is coming, for sure. But I'd honestly rather have the headers and new suspension first along with better gearing before getting that big ole' hunk of metal up front. We'll see.
Yep. This has been a rebuild year for my big Sport. Poor timing considering I'm still trying to get the ECM problem with the 3.5L swap worked out.
I noticed I'm finally starting to get a little rust in the rear passenger side quarter and the bottom of the passenger side door. Sigh. Nothing I have to jump on right now, but ... next year.
Yes. You do NOT want to bust a frame rail!
I've broken both rails behind the motor mounts and the repair sucks.
I'm still running across problems that caused. Sigh.
I'm not too keen on headers on what are essentially stock NA vehicles. You can't increase flow enough without doing major engine mods to overload the stock exhaust configuration. There just isn't enough wrong with our exhaust systems to justify that kind of expense and the headaches that come with headers.
Remember what you drive. Sports are NOT 2500 lb rice rockets. You need all the torque you can get in a heavy vehicle - ESPECIALLY one used off road. Your Sport is only going to get heavier - not lighter as you add off road equipment like a bull bar and winch. You need to work on increasing torque NOT HP. That said, if you did a set of headers to increase torque, you'd end up with exactly what you have now 'cause that's the design idea behind what the manufacturer built.
Just increasing flow doesn't equate to increased torque or/and HP but that's what most people think. Simply, too big an exhaust decreases scavenging until you get to the point where the flow through the engine matches the exhaust. The larger the flow volume capability, the more the engine has to flow to get there. Obviously, you can not flow much more through an NA engine than the physical displacement of the engine. And, there's no such thing as an exhaust that works for the entire RPM range. Typically, you choose a cam for the power band - low, high, mid, whatever - and then you tune the exhaust to work best in the power band. If the best power output is at 2", it's 2". Putting a 3" exhaust on WILL NOT make the engine produce more HP/torque.
A good example is the difference in performance between the stock 2", the 2.25" and 2.5" CAT-back. The 2.5" kills low end torque, but increases somewhat high end HP. The 2.25" increases low end torque, but doesn't do anything noticeable for the high end HP either +/-. If flow is what mattered, the 2.25" would help the entire power band a little, and the 2.25" would be better yet. But, that's not how it works.
Exhaust scavenging is a vacuum process. The motion of exhaust gases flowing away from the valve creates a vacuum at the valve. When the valves open the exhaust is drawn out and the fresh charge is drawn in. The more vacuum, the more exhaust gas that's drawn out and the more fuel/air is drawn into the cylinder - thereby increasing the power output. The larger the volume of the intake runners, head passages, headers, and exhaust pipe, the more gas (fuel/air and exhaust) has to flow through the entire system to create that vacuum.
At low engine speeds, there is little gas flow. As the engine speed increases, so does the flow and thereby the scavenging. So, what's happening is the 2.25" exhaust is increasing exhaust scavenging - getting rid of more exhaust and drawing in more fuel/air - in the cylinders at low speed. As the engine speed increases the 'normal' flow increases and the low end effect benefit tapers off. Therefore, no perceived increase in the mid/upper RPM range.
The 2.5" exhaust is actually decreasing the vacuum at the low end so exhaust scavenging decreases and therefore power output, but apparently there is some slight restriction in the stock exhaust (CAT-back) that comes into play at the 3500+ RPM range - therefore, the small increase in HP with the 2.5" exhaust.
The headers - i.e. downpipes and exhaust manifolds - are a critical part of this system. Even more so than the CAT-back segment, increasing/decreasing the size of the individual header tubes and collector, the length of the tubes and collector(s) can have a drastic effect on power output. Smaller, longer tubes has the effect of moving the power band down the RPM range and increasing the size and lengthening the tube moves the power band up. Usually - you have to do the math to get all of this right 'cause its not just cut and dried "stick this in for x increase at y RPM".
I spent years tuning for canyon bashing here in CO in the mountains (both bikes and cars) - which isn't much different than tuning for off road. Torque is your first priority. Torque is what gets your vehicle moving and like I said above, the heavier the vehicle the more important lots of torque is. Headers and custom building headers is a science. If you don't know the math involved - don't touch what you have, and don't trust anyone that says they can just "weld you up a set" 'cause they're idiots. And NEVER EVER try to use a set of headers designed around turbo/supercharged vehicles - those are totally different animals.
Unless you want to turn your NA vehicle into a boat anchor.
However, if you're dead set on this make sure they're ceramic coated inside and out for heat or invest in a lot of header wrap or you're going to bake everything in the engine bay. Heat build up is one thing I never had to deal with on road racers at least.
And if you go the header wrap, be prepared to replace your headers every couple years.
And, lastly
, the wrong header size will completely obliterate your gas mileage. Something to think of.
Edward