The Engine that Honda uses for the Element is the K24A4. As many performance driven people know this is a stout short block that is essentially a stroker version of its K20 series engines. This series of engines are the replacement to the B series engines from the late 80's up in to the their phasing in the early 2000's. They are capable of being built to output over 1000 HP. They are avidly used for Honda's open wheel track cars. However, you visit any K-series motor forum to talk mild power gains and improving efficiency with out a high output goal and your likely to get laughed at.
But, that isn't exactly how it should be. Between Honda's Accord, Civic, Cr-V and Odyssey and Acura's RSX and TSX the Element stands like a literal "Captain Planet" as it comprised of parts from all of these vehicles whether Honda intended that or not.
Solving for K: The algebra of Honda engines
Some of the know facts for HO (high output) Honda K builds is using parts interchangeability. The most definitive motor for power is a hybrid build of K series parts to make a HO K series engine beast. This build type is typically comprised of a K20 cylinder head and pistons mated to a K24 short block. Most commonly a K24A2 Block and K20A2 Head (RSX-S). If this makes the ultimate in power for a street car how do we adjust this equation to make P (power) equal E (Economy).
To have economy we need to maximize efficiency with out raising the cost of fuel consumption. This means modest bumps in HP (Horse Power) and torque. When the K24A4 was introduced it came with a meager 160 HP. This motor has been the economical power house for the Accord, CR-V, and the Element. It has a modest compression ration and the E-type VTEC and VTC (Variable Timing control). Now Baring chassis weight comparisons the 2005 Accord holds 29/37 MPG (City/Highway miles per gallon), The 2005 CR-V has 23/29 MPG and the Element finishes with 22/26 MPG. All these vehicle run the same engine and essentially the same transmission. However in 2005 Honda added a K24A4 engine with 5 speed automatic vs the K24A4 with a 4 speed automatic in prior years and the CR-V and Element. In 2007, the K24A8 was introduced for the Honda Element adding 6 more HP, and about 2 MPG. This is where we can start to solve for E. As I am an owner of the earlier K24A4 4 speed Elements (2003 and 2006 EX) I can a minimum swap the cams from a A8 cylinder head onto my A4 and start with a little bump towards efficiency. TO take this one step further I could build my own franken motor.
At some point down the road I intend to build a K20A3/K24A4 hybrid motor. This would consist of my current K24 block, a K20A3 head (small bump in compression ~9.9:1), K24A8 Cams for better efficiency. These will be mated with an RBB intake and exhaust manifolds (04-05 TSX) and throttle body. This should yield a a 200 to 210 HP motor with a proper tune leaning towards economy as Honda has done for the IVTEC-E. Coupling this with a 2005 Honda Accord 5 speed then there shouldn't be any issues sans the wiring harness for the transmission to use the factory ECU with a KPro tune to possibly achieve 8-10 more MPG. This would also result in lightening my current chassis by ~137lbs by removing the AWD system. If an Element were capable of making 29/33 MPG that would be an amazing cost savings on fuel alone.
Diet for the Mass(EX): it is great having a weight loss partner
The first place to help fuel economy is reducing weight. However let's be real... This is a utility vehicle it is heavy because of the size alone. The 2005 Honda Accord mentioned earlier with the 5 speed auto 3210 lbs on the EX trim with the K24A4 engine. A 2006 Honda Element FWD EX trim comes in 3391 lbs. This makes a difference of a 181 lbs. Depending on your use of the element reducing chassis weight may be difficult. However somethings may not be as important to have for instance the factory stereo in an element ranges from 4-5 lbs, the OEM room racks weigh a combined 9.67 lbs. Based on my stereo for my 06 (XM ready 7 speaker) I measured 4.9 lbs and 9.67 lbs for the racks. Sans 3lbs for the new stereo i have a weight savings of 11.57. I plan to take this further by using Honda Accord/Civic cloth seats in place of the weather proof vinyl seats that came factory. This may make for a weight savings of about 10lbs per seat.. it remains to be seen. Hopefully you get the gist of where I am going with this. At the time of buying my second Element a FWD was hard to come by, and I can no longer drive a vehicle with a clutch. So Automatic is where it is at. There is another page on this site that covers the factory weights of the chassis by model/trim and the weight of options/equipment that can be removed at your own discretion. Please be mindful also that the average weight distribution for these vehicles is about 56% front/ 44% back. When reducing weight the car will handle better if you pull weight from the front more so then the back. However, in terms of drag racing 0.1 of a second can be gained for every 100 lbs shed. This means we are improving the power to weight ratio (freeing up existing HP/using less force for the same work).