Printable View
I fitted the HM headers only to my TWII VRX and noticed an improvement in roll on acceleration, or mid range torque. More power, dunno, but an improvement for sure, but not night and day. A couple of the header bolts are a bit fiddly to access, but straightforward enough.
Agreed about the HM's, but any decent aftermarket muffler that is a straight through design 2.5" in - offset /out - centre will free up more power compared to the stock baffled muffler.Quote:
Originally Posted by munkeymanz
I have a stainless magnaflow straight through on my AWD for example, same design & virtually identical size to stock baffled muffler.
The other advantage of an after market system, including the HM headers, is a reduction in weight. A few might laugh this off but when you add it up you can save around 15kg with a complete exhaust system change. That might sound like a drop in the ocean, but every kg counts toward improving power to weight ratio, which leads not only to better acceleration but to improvements in economy.
KWAWD, is yours the KW GTVi AWD or the KL Ei AWD? If former, then you already have the straight through muffler as fitted to the Sports/VRX and other GTV/i Veradas. When you overtake, do you just kick down or use the tippy to shift down a couple of gears? If former then if you normally drive sedately then it wont respond very quickly as it learns your driving behaviour (better to use the tippy). I use the tippy all the time and do not have overtaking issues (even with wife, 2 kids, boot full of stuff) on the highway. Bear in mind, I also have the 380 cams and SKR tune as well as modified intake to feed in cold air from outside (similar to the NZ CAI snorkel) as well as a 200CPSI metal cat.
I've got the KL AWD. (Apologies about my handle here which is misleading). I don't think it comes with the EI designation, it's just the AWD?Quote:
Originally Posted by vlad
I just use the auto in, er, auto mode, mostly. But overtaking feels less effortless than my KH, as if its holding back somehow.
I gotta say, the KL kicks down at the right times and all and I'm not necessarily flooring it at top speed when I get this feeling of holding back. It feels like its revving harder sometimes than the KH would be in the same scenario. I think it's noisier than the KH which probably gives me that impression, I dk. The KH can be slow to overtake at high speed because it won't always kick down, but it never felt like it was being held back, always felt free flowing. The KL just feels like its not breathing easily or something, it's hard to explain. Basically the car is heavier than the KH and naturally noisier given the drive train, so I put this feeling of "holding back" down to that, a perception thing. It's got to work harder to deliver the same performance as the KH, so rev harder and sound noisier right?
You're probably right about using the tippy, i do drive fairly sedately sedately most of the time. I'll try it, but I think any simple mod that improves performance is worth a go.
Sounds like ur car is quite a bit different to mine with those mods tho.
your kh will labour less because its fwd.
Ok, if you would take a minute to explain it? Is it just a function of the extra weight and drivetrain components as I thought?Quote:
Originally Posted by HaydenVRX
Anyhow, that's why I was thinking of doing the HM headers.
Correct. KH FWD weighs less than a KL FWD which again weighs less than a KL AWD. The reason I said EI AWD is because the KL AWD is based on the Ei where as the KW is based on the GTVi.
The KL will also have the 5 speed auto where as the KH will have the 4 speed so the gear ratio's will be a bit different, I think that the 5 speeds are geared shorter than the 4 speeds.
Your AWD is giving your KH more than 150kg head start (~10% more kerb mass than the KH). Not only that, but it is driving a lot more energy sapping drivetrain (somewhere in the vicinity of 50-60% higher losses than for an FWD auto based on dyno results I've looked at). The only things in the AWD's favour in this comparison are a 10% lower final drive ratio, slightly better cams (if the KH has #4s) and the most aggressive downshift points of any auto 3rd gen, but these advantages aren't anywhere near enough to balance the equation.Quote:
Originally Posted by KWAWD
If you haven't already got the straight through muffler as others have suggested, it is by far the most bang for buck performance mod you will make. The AWDs do respond well to the HM headers due to the cost cutting design of the stock "collector" that joins the piping from each bank, but the reality is that the headers will cost at least twice as much as the muffler and deliver at best half the performance gain.
Unfortunately, as I've noted elsewhere, I believe that the AWD WOT upshifts are a bit too high (at about 5800rpm) for the stock engine/exhaust power/torque curves. I've not driven an FWD to know when the WOT upshifts happen in such cars but from the shift maps I would expect somewhere about 5400-5500rpm, which is closer to where I think the stock AWD upshifts should be.