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Old 06-09-2015, 11:29 PM   #1 (permalink)
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EGR for scooter engine that doesn't have it?

Hi, all.

So I'm exploring all avenues to increase fuel efficiency as much as possible. It's a project-bike.

Thus far, I've replaced the wheel and rear gear set bearings with micro-polished and tungsten disulfide-coated hybrid ceramic bearings, put in 15% taller rear gears, modified the clutch to give a lower engagement speed and slightly wider range, installed all LED lights, am running a Pulstar HE1HT9 spark plug, and put 8.5 grams of 0.6 micron tungsten disulfide (WS2) in with the engine oil (Royal Purple 10W-40 Synthetic with Synerlec). After the new rear gears are worn-in, I'll put WS2 (1.75 grams) in the gear oil (Royal Purple 75W-140 Synthetic with Synerlec), as well.

In the near future, I'll be getting rid of the OEM coolant pump and replacing it with a custom-built microcontroller driving two electric mag-drive pumps (two for redundancy and emergency cooling capability in case of coolant, cylinder head or exhaust temperature overheat), putting a custom-built corona discharge ignition in; replacing the engine bearings with hybrid ceramic bearings; and getting rid of the OEM generator stator and ground-shunt voltage regulator, replacing it with an alternator and proper voltage regulator driven off a second flywheel with embedded magnets that sits inside the engine's flywheel where the OEM stator usually sits. The magnetic interaction between the two flywheels will turn the alternator. I'll also be having a custom rear rim fabricated which will hold a Stieber ALF2D2 sprag clutch so the bike can coast without engine braking or gear train drag slowing it down.

Further out, I'll be getting roller lifters fabricated to replace the flat tappet lifters, getting ceramic heat shield on the face of a new piston, on intake and exhaust valve exposed surfaces, and on the head and intake and exhaust ports; getting a new cam cut that can take advantage of the roller lifters (faster lift and seat, slightly longer open duration, no overlap); a custom expansionary exhaust that reflects a negative pressure pulse back toward the cylinder just before the exhaust valve closes (at highway speed RPMs), otherwise known as negative supercharging, to replace the loss of scavenging due to there no longer being valve overlap; and an aerodynamic body; getting a new cylinder WPC and WS2 treated; running a Total Seal gapless top ring and lower friction oil control ring; and building an exhaust heat recovery unit that heats fuel and water for injection so the fuel and water don't have to absorb as much heat in-cylinder; implementing a constant-temperature air intake system (since this bike's fuel efficiency is extremely sensitive to outside air temperature... it runs best when it's about 85 F outside); installing a high-temperature piezoelectric transducer in the intake to ensure complete vaporization prior to the intake charge hitting the cylinder; and putting in a custom programmable ECU to control it all.

Of course, to fit it all in, and to make mounting the new aerodynamic body easier, I'll be building a ChromeMoly trellis frame with forkless front end for it, which will also save substantial weight over the old heavy steel frame (the bike weighs 338.8 pounds curb weight, I'm hoping to trim about 65 to 70 pounds off that, which will give me the same power:weight ratio of a Toyota Prius). It'll be a feet-forward design, for lower frontal area.

And really far out there in the future, I want to look into a desmodromic valve actuation setup for this bike to do away with the power drain of having to compress those valve springs. And I'm looking for a toroidal infinitely variable transmission (IVT) to replace the CVT, operated via a twist-grip on the left handlebar, which will let me tailor the performance of the bike (performance or fuel efficiency) with a twist of the wrist. It'll also allow me to stop on steep hills without rolling backward, since the IVT has a "geared neutral" that prevents movement as long as the engine's running.

Along the way, I'll be experimenting with different fuel concoctions... my first idea is to replicate Sir Harry Ricardo's Racing Discol 1 (RD1) fuel from 1921. That fuel consisted of 80% ethanol, 10% acetone and 10% water. It supposedly became popular with racers because it gave about 20% better fuel efficiency and power over gasoline of that era. My idea is to convert the 10% ethanol in E10 gasoline to RD1 by adding ~47 ml of water and ~47 ml of acetone per gallon of E10 gasoline thereby making the water miscible in the gasoline. I'll also be experimenting with isopropyl alcohol, methanol, naphthalene, hydrogen peroxide, and xylene in various proportions.

But on to the topic at hand... this bike has the PAIR (Pulsed Air Injection Reaction) system (it injects fresh air into the exhaust to burn off any hydrocarbons that don't burn in-cylinder), but it doesn't have EGR.

Would EGR help with fuel efficiency? If so, I can purchase an EGR valve that fits on another scooter (a 125 cc engine, my engine is 174.5 cc), but what would be the best way to control it?

Also, I want the be able to filter the EGR so my intake doesn't get all gunked up. Are there filters available for this purpose?

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Old 06-10-2015, 10:15 PM   #2 (permalink)
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What I know about EGR valves is they reduce emissions as does the PAIR system. You do no mention what compression ratio you plan to run. On the hydrogen fuel cars EGR was used to reduce pre ignition. Since you are blending fuel this is less of an issue.

You have done a great deal of research already. Consider using a higher efficiency engine such as a Sterling or diesel generator unit. A unibody shell could be lighter still. If your power to weight ratio is 1 hp :36 lb. and your Cd is under 0.30 the power needed can be minimized. Check your state DMV requirements too.
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Old 06-10-2015, 10:38 PM   #3 (permalink)
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Sorry, I forgot to include details of the engine:

- 174.5 cc fuel-injected liquid-cooled single cylinder.

- 62 mm bore x 57.8 mm stroke

- 0.37 mm deck height

- Squish area: 15.58 cc

- 11.2:1 compression ratio (OEM)
Although it'll be a bit higher due to the ceramic heat shield coating on the piston face and cylinder head, so let's say 11.3:1.

- 227.2 psi compression pressure

- gasoline engine

- maximum RPM: 9200 (OEM)
I'll be extending that to 12,000 with the new ECU and a beefed up crankshaft and connecting rod.

- Valve timing (OEM):
Intake Open 12 (BTDC) Close 35 (ABDC)
Exhaust Open 28 (BBDC) Close 8 (ATDC)
The new cam grind will do away with valve overlap. It'll roughly follow the same valve timing as what's found on the Negative Pressure Supercharging - Impulse Engine Technologies Pty Ltd - Australia site.

The documentation for this bike states a power output of 11.4 KW (~15.3 HP), but I think mine is a bit higher, given that it's always exceeded the factory-stated top speed, and would hit the rev limiter far too easily, which was the reason I geared up. I attribute the hard break-in (ala MotoMan) and the LiquiMoly Ceratec as two factors contributing to lower blow-by and thus better compression and power.

Last edited by Cycle; 06-10-2015 at 11:27 PM..
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Old 06-11-2015, 04:14 AM   #4 (permalink)
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It looks like most of what you are planning will give negligible results at best.

2016: 128.75L for 1875.00km => 6.87L/100km (34.3MPG US)
2017: 209.14L for 4244.00km => 4.93L/100km (47.7MPG US)
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Old 06-11-2015, 05:59 AM   #5 (permalink)
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Check out Craig Vetter interview with some of the fuel economy competitors of his 80s fuel economy contest. One of the used softer valve springs, I would think lower red line would be in order also.

Last edited by gil; 06-11-2015 at 06:04 AM..
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Old 06-11-2015, 06:23 AM   #6 (permalink)
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Not all of it is aimed at fuel efficiency as a first effect, but all of it is necessary in order to fully outfit the bike for testing.

Reducing blowby from ~3% to ~1% via WPC treatment of the cylinder and gapless top ring won't give a large fuel efficiency effect, but it'll certainly help engine longevity given that I'll be experimenting with water injection. The WS2 treatment of the cylinder will reduce friction and help in the event alternative fuels remove the cylinder oil film.

Getting rid of the OEM stator and ground-shunt voltage regulator won't help much either in terms of fuel efficiency (it'll only save about 100 watts being shunted to ground, or about 0.877% of total engine output), but the new alternator will increase generating capacity of the bike, and the second flywheel being magnetically driven from the first will act as a means of damping engine vibration, giving better NVH.

The roller lifters replacing flat tappets won't help fuel efficiency much... except that they allow a faster valve lift and seat with a slightly longer open duration, which helps engine breathing.

The rear sprag clutch will certainly have a moderately beneficial effect on fuel economy, considering that I'll be able to throttle down and coast, whereas now engine braking means no coasting.

The no-overlap cam grind and expansionary exhaust are to allow me to run on fuels that would cause backfire if there were valve overlap (and to make up for the loss of power that the non-overlapping cam grind brings about due to lack of blow-through scavenging). It'll also help to prevent backfire when I'm heating the fuel prior to injection and doing ozone injection experiments, since the fuel will be close to ignition prior to it reaching the cylinder.

The constant temperature intake most certainly will have a beneficial effect on fuel economy... during cold days, my MPG drops to 55, on warm days it rises to 75. The constant temperature intake will allow me to adjust the intake air temperature to that which is most efficient. Eventually, it'll be load-based so if more power is needed than the engine can deliver given the intake air temperature, the intake air temperature will be adjusted lower.

By the same token, more closely controlling the coolant temperature via PWM-controlled electric pumps will not only do away with the power drain of the OEM pump (which can take upwards of 1/4 HP (~1.64% of total engine power) at WOT, whereas the new mag-drive pumps both running at full tilt, with the microcontroller thrown in, only consumes ~22 watts), but will also allow the coolant temperature at the cylinder head to be precisely controlled for maximum efficiency. The micro-controller is programmed to increase coolant temperature at low engine load for more efficient operation, and decrease temperature under heavy engine load to reduce knock. It'll monitor coolant, cylinder head and exhaust temperatures for overheat, and kick on both pumps and both fans in that event until the overheat condition is resolved. The dashboard display will give feedback on how the system is operating.

Swapping some of the fuel out for water... that's an unknown, but what is known is that water is a far superior expansion medium than air (water expands to steam at ~1:1600 ratio whereas air expands at ~1:37.75 ratio given the same in-cylinder temperature delta), which will contribute to cylinder pressure and thus engine power while lowering fueling requirements, and while also quenching combustion temperature peaks to knock out NOx production, lessening the amount of heat being wasted via the cooling system, and acting as an octane booster to damp lean knock.

0.0073656109805262 mole of air
60 F
174.5 cc
1 atmosphere

0.0073656109805262 mole of air
1292 F
15.58 cc
37.753100472841 atmosphere

You'll note that the saturation temperature for steam at that pressure is only about 480 F. So the steam from water injection will be highly superheated.


The new trellis frame won't in and of itself help with fuel efficiency, except it'll provide a feet-forward seating arrangement with a low frontal area and easy mounting of the aerodynamic body, while also saving weight and providing better access to the bike's mechanicals for work to be done. The forkless front end will also improve handling. The longer and lower stance of the bike will make it almost impossible to do an endo.

The aerodynamic body will most certainly provide much better fuel efficiency.

A toroidal infinitely variable transmission will not only save that ~8% energy wasted in the traditional CVT and rear gears, reducing it to ~2%, but will allow a closer match between engine speed and road speed to increase time spent at the engine's most efficient BSFC.

A new programmable ECU will not only control fuel injection, but water injection as well, allowing me to do away with the extra fuel injected as coolant under heavy engine load, and allowing me to burn lean lambda, which will have a very beneficial fuel efficiency effect.

The piezoelectric transducer in the intake is for experiments pertaining to full vaporization of the fuel prior to it hitting the cylinder. The effects on fuel economy are unknown... which is sort of the reason for experimentation, after all.

The ceramic heat shield coating on the piston crown, cylinder head, exposed parts of the valves and the intake and exhaust ports are for several reasons... protection of the metal during ozone experiments, lessening heat loss to metal engine parts, and protection of the piston and head while burning alternative fuels (some of which burn hotter than gasoline).

You said most of what I was planning would give negligible results at best... which changes, in your opinion, would give negligible results?

Last edited by Cycle; 06-11-2015 at 09:32 AM..
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Old 06-13-2015, 02:52 PM   #7 (permalink)
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Concentrate on raising the combustion ratio and reducing CdA of the aerodynamics.

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