Sport Bikes banner
1 - 20 of 26 Posts

·
Duc Hunter
Joined
·
951 Posts
Discussion Starter · #1 · (Edited)
So I was pondering with my brother and friend a couple days ago and thought I'd ask the masses why nobody's tried to do DI on a motorcycle engine? Alternatively, why is it that bike engine tech lags so far behind car motor tech, particularly since 3 of the big 4 produce performance automotive engines.

My bro suggested that running the pump necessary to get 1200psi in the line for DI would be tough on such a small engine; our friend countered that probably wouldn't be too hard, and the reason for it was more cost not being worth it.

Most of the larger performance-oriented car manufacturers offer at least one DI engine, but maybe it's just not feasible for smaller production numbers that motorcycles are limited to.

Seems like it would break the stalemate on 600cc engine development. I was under the impression that DI allows for increased efficiency (and thereby power if you increase fuel/air) and reduces emissions (which would allow manufacturers to lessen all the heavy, strangling exhaust bullshit), but maybe that's incorrect...
 

·
Asphalt Magnet
Joined
·
1,079 Posts
I would imagine the electrical power might be an issue. The stators on the bikes can produce so much electricity and that is usually at higher RPMs.
 

·
Registered
Joined
·
18,682 Posts
Bike tech isn't behind. This may be confusing because emmissions controls have been less stringent for bikes but the technology in bike engines, particularly in combustion chamber design, intake and exhaust has always been well ahead of cars. This is why bikes make so much more power per packaging size.

How many cars have variable length intake runners or exhaust valves for example, or use exotic valve or piston materials? How many have coated pistions or two ring piston designs? How many have two injectors, one being of the shower type? Even four valve heads have remained relatively uncommon until recently.

You can't generalize from this one example or from the fact that bikes have, until recently, used open-loop FI. There are other reasons. In the specific example, I'm not sure there is much to be gained.
 

·
Red Dragons
Joined
·
2,887 Posts
I for one would not want a fuel injection system under the kinds of pressure that DI requires between my legs. The cars I work on that have DI have pressures that would pierce the skin and bone of your hand if it's not bled off before servicing anything in the system.
Not to mention, what if you binned it and something in the high pressure side of the fuel system cracked or ruptured? Instant fireball.
 

·
Badabing!
Joined
·
4,088 Posts
Also, there's no need. Bikes make plenty of power for their weight, and added complexity = added cost. People already balk at the cost of the new R1...Imagine if it came with direct injection and a $19k price tag.
 

·
Silent pipes take lives
Joined
·
12,981 Posts
Hell, bikes were a decade or more behind cars as far as the fuel injection versus carburetion thing went.

In some ways, motorcycles have been ahead of cars. In other ways, they've been behind. Either way, there are differences between bikes and cars which make different advances more or less valuable on a motorcycle than they would be on a car.

GM pioneered magnetorheological shocks in cars. I still haven't seen them on bikes. Why? Cost, complexity, and power requirements. Hell, ABS and traction control are just now making their way to bikes.

Because of weight and packaging issues, motorcycle engine development has had to lean toward advancements in RPM ability rather than using larger, heavier, or more complex solutions. Cars aren't lower-tech in this department, they just took different paths.
 

·
Mediocre Strafer
Joined
·
9,137 Posts
Where do you get the idea that bike engines trail car tech??

In output per liter, or output per weight, they're *way* up the list of NA engines, except for rotaries which have been primarily a low-volume issue.

Computer controlled intake tract length, drive-by-wire, cross-plane cranks, dry or semi-dry sumps, multiple-plug heads, per-cylinder ignition coils, plated cylinder bores, fiber-optic control bus...

Motorcycles have a different set of problems to solve, so the solutions aren't always the same, but sportbike engines are pretty bleeding-edge.

KeS
 

·
Silent pipes take lives
Joined
·
12,981 Posts
Where do you get the idea that bike engines trail car tech??

In output per liter, or output per weight, they're *way* up the list of NA engines, except for rotaries which have been primarily a low-volume issue.
That isn't a function of advancement, but rather of utilization. They weigh less because the item they're moving weighs less. They don't need to be beefy enough to move a 3,000-5,000 pound vehicle around for well over 100,000 miles. Because they're moving something around 1/9th that weight, they can afford to have lighter, weaker cases, cranks, and other components. Additionally, because of their ability to rev higher, they also tend to utilize shorter gearing, making it even easier to move the bike and lessening the encountered loads.

As before, motorcycle technology does lag behind automotive technology in some ways simply because they don't need to advance as quickly, or because the technology isn't logical or feasible in a motorcycle.

Something I didn't cover before is the negative effect of low prices and small volumes. Cars get good tech quicker in part because it's financially beneficial. Later these technologies can trickle down to motorcycles. We've already seen this with fuel injection, ABS, and traction control.
 

·
Theres no I in threesome
Joined
·
6,118 Posts
Motorcycle tech doesn't lag behind automotive tech, just look at how much engineering they can pack into a tiny space, and have it produce more power than a car engine. Most cars don't have individual throttle bodies and injectors, coil on plug ignition, 6 speed sequential gearboxes, and other cool stuff.
 

·
Registered
Joined
·
1,063 Posts
I guess there're some things that are ahead with bike tech, but taking so long to come off carbs is huge as well as lagging EFI developement. I think it's because bikes are just toys in the b***** picture and the tech naturally trickles down.

I don't know of any big4 bikes with oxygen sensors and knock sensors, but I'm sure there has to be some of the former out there by now.

Direct Injection make me think of diesels. I'd like to see more diesel bikes. There's no reason they couldn't perform either.

It's refreshing to read such mature responses to an interesting thread too BTW.
 

·
Premium Member
Joined
·
20,922 Posts
Much of the technology advances in automobiles has been driven by the need for lower emissions and better fuel economy, while maintaining or increasing power output.

Motorcycles have not had these burdens placed upon them until very recently, and only then for emissions.

Much of this technology increases costs and weight. Two things that are very sensitive to the sport bike market. As the technology progresses, both costs and weight diminish to some extent. But many of todays sportbikes are still heavier and far more expensive than those of five years ago.

Is there a need for DI on motorcycles in today's market? I don't know. Do we need it? Is it worth any possible trade off?

The first wide-spread electronic fuel injection systems suffered in performance comparison to the carburetors they replaced. The last carb'd R1 was probably the sweetest fueling bike ever. The first FI R1 was nowhere near as smooth. It has taken a long time for EFI to catch back up. And this was before major emissions standards and without any efficiency standards.

I still prefer FI over carbs for overall reliability and performance, but a set of well tuned and sync'd carbs can't be beat for throttle feel and modulation. Too bad they never stayed that way for long.
 

·
Duc Hunter
Joined
·
951 Posts
Discussion Starter · #13 · (Edited)
thanks guys -- all good, thoughtful responses.

i didn't mean to imply that i thought bikes were underpowered, lol. in fact, i'm more interested in quite the opposite (like the small-displacement ultra-spec japanese 400ss from the 90s).

and yeah, i guess i should've been more considerate of definitions of "low tech." the different reasons underlying alternative solutions for evolving are something i hadn't really given much thought to.

i think it's impressive how much technology goes into both car and motorcycle engines nowadays, and i'm looking forward to when both get goodies from the others, it's just the problem of implementing it for long enough that it gets considerably developed.

i'm just curiously aroused by the idea of eventually having an ultralight 400cc sportbike, capable of screaming to 20k rpm, with direct injection and infinitely variable cams/valve timing (not VTEC), making more power than the current 600 supersports, but lighter, and with more (and a flatter spread of) torque, better fuel economy, and lower emissions. mmmmmmmmm

a diesel sportbike would also be cool, though i'll be the first to admit i lack the familiarity/understanding to know what would be impressive/impossible about its implementation.
 

·
Registered
Joined
·
1,581 Posts
Much of the technology advances in automobiles has been driven by the need for lower emissions and better fuel economy, while maintaining or increasing power output.

Motorcycles have not had these burdens placed upon them until very recently, and only then for emissions.
Ding Ding Ding! This is the difference.

I don't necessarily think that the newer technologies increase weight, though. Stricter and stricter government restrictions and requirements, (airbags, bumpers, etc, etc) along with an ever increasing importance of safety, are what is driving the weight issue.
 

·
Duc Hunter
Joined
·
951 Posts
Discussion Starter · #16 ·
but wouldn't DI allow for fewer cats as it inherently improves emissions?
 

·
Registered
Joined
·
2,037 Posts
2.5+ horses per cubic inch from a naturally aspirated factory motor hardly sounds like lagging technology to me. Virtually every new 600CC bike on the market achieves this.

When I see factory N/A Accords pumping out 500 horsepower you may have an argument, till then...
 

·
Duc Hunter
Joined
·
951 Posts
Discussion Starter · #18 · (Edited)
there are other ways of measuring tech than specific output.

oh and by the way, high output per displacement becomes increasingly more difficult the larger an engine becomes, so while having a 500cc motor making 100hp may be relatively easy (200hp/L), having a 5.0L engine making 1000hp is considerably more difficult (despite the same 200hp/L specific output). just take a look at the 125 2-stroke GP bikes that are churning out nearly 500hp/L.
 

·
BIRDMAN
Joined
·
2,559 Posts
DI motorcycle engines exist if you count 2 stroke scooters. Aprilia has made some.
Also recall reading that DI is perhaps a way to bring the 2 stroke bike back because it allows 2strokes to run clean.
Marine outboard motor makers have had great success making clean 2stroke DI engines.
So DI may, if we are lucky, bring back the 2 stroke street bike.
 

·
Old school fool
1994 CB 1000
Joined
·
5,725 Posts
The whole "horsepower output equals technology" is interesting. Old time steam trains were much more powerful than the diesel electrics you see on the rails today. When steam tech was at its height, you almost never saw the locomotives daisy chained together to pull a big load - maybe on a really steep grade or something, but not like today where you see 4 locomotives pulling a train over flat ground.

Still, would anyone say they are more sophisticated than today's trains? No. Those trains were replaced because they were maintenance intensive, used a lot of fuel and hammered the rails so hard that the rails had to be replaced. Plainly put, its cheaper for the railroads to run 5 electrics in place of one giant steam locomotive.

The moral here is that older technology is not always weaker or worse. Bikes have been plenty strong for decades and without regulations on their emissions etc there hasn't been a real need to find new tech that pumps them up.
 
1 - 20 of 26 Posts
Top