Direct Injection

Are any of the Big4 (or BMW, Ducati, etc.) doing putting it on motorcycles? Ive been researching GDI (gasoline direct injection) vs Port FI for a project that im working on for one of my classes, and the only bike i know of with GDI is the Motus MST with the Katech KMV-4 engine (1600cc's of bad*ssery btw). i was kind of wondering with the large budgets of racing efforts and the performance increases of GDI, are GP/WSBK teams using it? i understand it means retooling and that much higher quality materials are required but if the trend is moving that way for racing in cars, why not bikes?

personally I thik a 5-valve, crossplane, GDI R1 would be sweet.

whadda yall think?

I've been wondering the same thing about motorcycles adopting direct injection. Better fueling, more power, better gas mileage. Seems like a no brainer! I wonder if there is a packaging issue or weight.

The problem with GDI is that there are RPM limits, which is why the Motus has a redline of only 8500 RPM..
Both BMW, and Kawi are working on this, (probably more too) but so far it has been a no go..
The cost of the very high pressure injectors, and the size they need to be to get that fuel squeezed in there has been a problem too.

I think the biggest factor preventing this from being adapted into mainstream use in both cars and especially bikes is the amount of fuel pressure required. Most port fuel injected vehicles run on a fuel pressure of about 40psi. The fuel pump only has to provide that pressure and a sufficient volume of gasoline to keep the injectors and ECU happy. With direct injection, the PSI required is sometimes as high as 1000psi and the pumps are obviously more expensive and power hungry plus the fuel lines and other ancillary equipment and parts to handle this high of a pressure equals more money. Diesel engines use direct injection as an inherent part of their design and have been doing it for decades, but ask anyone who has ever had to replace a fuel pump or fuel filters on a diesel pickup how much that cost them ($$$$$). I bet we will see it in the future but since you're asking why we haven't seen it already that's my assumption.

In 1955 M-Benz used a Bosh machanical direct fuel injection on the Gullwing.

I'm just amaze how good the cars are built today. Bare with me here. They ate made to be thrown away every 8-10 years but still. I remember not so ling ago changing oil, plugs, cap, rotors on my Civic every 3k miles or so. I just bough a 2012 Ford Fiesta. All I need to do is change oil every 10K. Spark Plugs are due at 100K and timing belt at 150K.

So technically I can drive that thing until it need plugs then trade it in.

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famous556 said:

With direct injection, the PSI required is sometimes as high as 1000psi and the pumps are obviously more expensive and power hungry plus the fuel lines and other ancillary equipment and parts to handle this high of a pressure equals more money. Diesel engines use direct injection as an inherent part of their design and have been doing it for decades, but ask anyone who has ever had to replace a fuel pump or fuel filters on a diesel pickup how much that cost them ($$$$$)

Click to expand...

Yes, the injectors on my 05 Cummins TD are about $500 ea..(X6!) they are also about 8" long..that and the diesel doenst rev like a bike would need to.
The fuel pump is like $2000 just on its own..(man I hope I never have to replace it..)

..and, Direct Injection has a downside. There have been increases in carbon build up on intake valves because there is no fuel being sprayed on them, washing off the gunk from the Exhaust Gas Re-circulation. The most obvious benefit in GDI is the ability to run higher compression rations...not a problem on the fizzer.

I think the best advancement to bring to the 2-wheelers would be real closed-loop fueling. MAF telling the ECU how long to open the injectors, then the O2 sensor feeding back the results for fuel trim.

My 2 cents worth.

/\That is what my BMW already has. So it is being done. (O2 sensor, ect..)
That and a knock sensor, so you can really use the advantages of the high test fuel..

Thinking most of the new engines have direct fuel injection. The Ford Eco-Boost motors have it. For bikes they seem to be able to get the HP figures up there, biggest advantage of DI would be increased efficiency (gas mileage). The Motus is a very interesting bike. A bike that can be loaded with bags and gear and ridden for days and then take to bags off and go thru the canyons with the sport bikes. However the price is out of my range.

famous556 said:

I think the biggest factor preventing this from being adapted into mainstream use in both cars and especially bikes is the amount of fuel pressure required. Most port fuel injected vehicles run on a fuel pressure of about 40psi. The fuel pump only has to provide that pressure and a sufficient volume of gasoline to keep the injectors and ECU happy. With direct injection, the PSI required is sometimes as high as 1000psi and the pumps are obviously more expensive and power hungry plus the fuel lines and other ancillary equipment and parts to handle this high of a pressure equals more money. Diesel engines use direct injection as an inherent part of their design and have been doing it for decades, but ask anyone who has ever had to replace a fuel pump or fuel filters on a diesel pickup how much that cost them ($$$$$). I bet we will see it in the future but since you're asking why we haven't seen it already that's my assumption.

Click to expand...

actually its more like 1500-3000 psi.


and there are advances being made in head design to swirl the air to mix the gas with the air since the mixing time is shorter, and turbos add to the swirling effect making GDI even more efficient. and if there is an rpm limit, then it would be great for something like a VTR, SV1000, SuperTenere, Ducati, any cruiser, BoxMWs, etc. it would make since that Kawi with their parallel twin and Beemer's Boxer design would benefit the most. but most 1000cc supersports dont rev as high as the 600s and usually redline at 10.5-11.5K rpm. but with the increase of low end power and midrange you could build a lower RPM engine and make the gearing a little longer. since the GDI system does however react faster than the PFI setup, why would there be an RPM cap? it seems like it would be even better at higher RPMs. also the thing with the valves doesnt seem to hold up either as the Motus has 100K mile valve intervals (thats 4x as long as the Yami's impressive 26K)

trepetti said:

..and, Direct Injection has a downside. There have been increases in carbon build up on intake valves because there is no fuel being sprayed on them, washing off the gunk from the Exhaust Gas Re-circulation. The most obvious benefit in GDI is the ability to run higher compression rations...not a problem on the fizzer.

I think the best advancement to bring to the 2-wheelers would be real closed-loop fueling. MAF telling the ECU how long to open the injectors, then the O2 sensor feeding back the results for fuel trim.

My 2 cents worth.

Click to expand...

I just found out few days ago that the FZ8 has a MAP sensor now... it's a beginning. LOL

Most direct-injection engines rely on the camshaft to power the high-pressure fuel pump. I'm guessing that the HPFP would have trouble operating at the high rpms of a bike.

...but MAP is not MAF. The pressure sensor provides information so the flow can be better estimated, but the MAF sensor measures the actual flow, the results of density, temperature, throttle opening etc. Just a better way to measure.

SweaterDude said:

why would there be an RPM cap?

Click to expand...

I think this explains it pretty well..


Direct Fuel Injection

CowtownBiomed said:

The problem with GDI is that there are RPM limits, which is why the Motus has a redline of only 8500 RPM..
Both BMW, and Kawi are working on this, (probably more too) but so far it has been a no go..
The cost of the very high pressure injectors, and the size they need to be to get that fuel squeezed in there has been a problem too.

Click to expand...

The Motus is also a Pushrod V-4 not a DOHC I4 screamer. And it's a 2 Valve. having twice the injectors on a 4 valve and have them fire on an offset or every other cycle until the higher RPMs when they fire together. In combination with a VVT device, it could be the real deal. and since most liter bikes only fire up to about 11-12K RPM (yes the R1 is 14K) then with DI you could bring the RPM's down a little and have the extra power.

also since air mixing can be a problem, and that turbocharging swirls the air to help this, why not rifle the intake instead?

Something to think off. I'm an auto tech by trade an what we're finding on the direct injection engines is intake valve contamination. Port injection spays fuel on the backside of the valve which cleans it of oil contamination that inevitably builds up. If have ever taken an intake manifold off you know what I'm taking about. Manufactures are starting to redesign engines with a port injector add to spay a small amount of fuel to clean the intake valve. Two steps forward and one back.

If I am not mistaken, there has been a ton of research done on the airflow inside the intake tract and "rifleing" was investigated, and passed on.
Though to be honest, I do not understand the whole thing.
My understanding is that, this is why we always see smooth area's in the intake area (and exaust too of course).
I also agree we ARE compairng a V4 pushrod, to a I4 becase one has DI, the others don't, and our curiosity has been peaked as to why..(if I am not mistaken)

From the posted article above,

"With direct injection, fuel can only be injected into the cylinder on the intake and compression strokes, rather than at any time during the cycle - half as long as with port injection. And, for best emissions, it's best to wait until after the exhaust valve closes during the intake stroke to open the injector, further limiting the time available. This is the stumbling block for direct injection currently. Motorcycles have such high-revving engines that the injectors can't deliver enough fuel in the reduced time available for each cycle. And the approaches used in traditional port fuel injection to increase delivery are difficult to implement: A bigger or additional injector would use up even more space in an already crowded cylinder head; increasing fuel pressure even further is also not an option, as it is already extremely high."

So it looks like all we need to do is resolve the timing, pressure, volume and change our approach to the intake issues, some time and money..