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Throttle bodiless Spark Ignition Gasoline Engine?

Throttle bodiless Spark Ignition Gasoline Engine?

Throttle bodiless Spark Ignition Gasoline Engine?

Is it possible to build a throttle bodiless Spark Ignition Gasoline Engine?  Could you use a injection pump setup similar to most common diesel engines?  Would this have to be used in conjuntion with a sliding cam VVT system in order not to create lean conditions in the cylinders?  What would the throttle response on such an engine be like?  If such an engine was made to work how would fuel economy, emissions, and performance stack up?

RE: Throttle bodiless Spark Ignition Gasoline Engine?

Control of airflow by cam duration and lift is useing the valve as a throttle


RE: Throttle bodiless Spark Ignition Gasoline Engine?

Theoretically, if you had some system for direct (and infinitely variable) valve actuation, you could control the speed and power output of an SI engine without a conventional throttle body. As Pat pointed out, you'd simply be using valve events as the throttle.

My guess is that the engine would perform similar to an engine running an IR (individual runner) setup. Good throttle response, nice low-mid power, but you'd start to suffer as the RPMs climbed. Basically, without a plenum, you can't take advantage of the air charge's mass to pack cylinders. VEs over 100% are very difficult to achieve with IR engines.

I think emissions might suffer as well. The valve event at idle and low speeds would be so brief, you would build quite a strong vacuum in the cylinders. Oil control, and subsequent oil combustion, would mean the engine would take a hit on the emissions.

If I had access to an IVVT (Infinitely Variable Valve Timing) system, and direct cylinder fuel injection... well the last thing I'd do is ditch the throttle body. In fact I'd toss in a variable intake geometry, variable compression ratio, a slick forced-induction setup, and tie it all in with the mother of all electronic control system... and then I'd get ready to accept my Engine of the Year award.

Good Luck,
Bryan Carter

RE: Throttle bodiless Spark Ignition Gasoline Engine?

     Mitsubishi builds this engine(sold every day)in conjunction with Hundaiy .I believe you refer to G.D.I. (gasoline direct injection). Super low Emissions technology No throttle needed. Eleven and a half to one compression.Dual compound injector (computer controlled)Fuel air ratio up to 60:1 ....Engine also sold in Europe by VOLVO(who else)    Corporate politics (TRUE "restraint of trade")Will keep this technology out of the U.S. market for several more years.                      Ezmee

RE: Throttle bodiless Spark Ignition Gasoline Engine?

"Corporate politics (TRUE "restraint of trade")Will keep this technology out of the U.S. market for several more years."

Yeah, let's have a conspiracy theory. I don't suppose that the incredibly low cost of fuel in the USA has any bearing on the willingness of Mitsubishi to import this expensive engine into the USA?

And having paid for it to be certified, I wonder how many more they would sell at a profit?


Greg Locock

RE: Throttle bodiless Spark Ignition Gasoline Engine?

Ezmee wrote:

"...Corporate politics (TRUE "restraint of trade")Will keep this technology out of the U.S. market for several more years."

Actually the reason we in the U.S. don't have GDI is due to our gasoline. North American blends of gasoline contain a more of sulfur than the European or Asian-Pacific market blends. Because of this, we cannot use the type of catalytic converters demanded by the use of GDI technology. The ultra-lean burn conditions create larger quantities of NOx when compared to a normal spark-ignited engine so special cats are required. GDI is pretty much a new take on the stratified charge design which was first seen here in the states on the late 70's Honda Civic CVCC.

Though the GDI does count as a "throttle-bodiless" engine, I did not consider this because Younglearner had mentioned VVT as possible work-around, so I addressed that issue. The GDI on the other hand uses injector duty cycle and rather LARGE amounts of recirculated exhaust gas to serve the throttling duties. GDI is definitely some cool technology, be interested to see where it goes.

Bryan Carter

RE: Throttle bodiless Spark Ignition Gasoline Engine?

Its all old school stuff. Been done many many years ago.
If you mean injection pumps as used on the "diesel engine's"
meaning the multiple pump system. But now most modern diesel engines use, an electronicly fired unit injector.
On the old "jerk pump system", fuel delivery was controlled by rotating the pump piston, which had a helix cut on them. Depending on which portion of the helix was inline with the spill port, determined the amount of fuel delivered.
I know Mercedes used it at one time.
The rack that controls the rotation of all the pumps with in the fuel pump body,(If memory serves.) and is linked to a throttle valve on the intake. If what you are trying to say is run with zero throttle on the intake. Not a good idea for an SI engine. For obvious reasons.

RE: Throttle bodiless Spark Ignition Gasoline Engine?

I think one thing is being omitted.  Gasoline has a relatively small combustibility limit compared to diesel.  The wide AF ratio of diesel lends itself to operating without a throttle.  Also, gasoline requires a spark to sufficiently ignite the fuel mixture.  Wet gasoline does not ignite easily, thus a means of vaporizing the fuel is needed.

In the past, a heated intake manifold did the dirty work, just boil the gasoline to a vapor.  Modern engines use higher pressure injectors to atomize the fuel into the intake manifold.  The presence of the throttle blade also serves as a means to vaporize the fuel: by lowering the relative intake pressure, the gasoline will tend to vaporize due to the pressure reduction.  If the throttle blade is removed, there is no relative delta P and the gasoline will puddle.  The DI engines have this problem, with the cool gasoline entering the combustion chamber and hitting the cylinder wall, quenching the combustion front.  As a good example, just look down the throttle bore of a throttle body injector with a strobe timing light and you can actually see the gasoline beads literally squirted out.  It hits the throttle blades as a liquid and rolls down.  This is little better than the old carburetors.

This now leads to the question, why is this engine not being admitted into the US?  Two problems, one has been addressed, the fuel quality.  Second, this engine is relatively dirty at low speeds and lugging; relative to the same CID engine with a throttle.  Although the CE/VE is vastly superior at high rpm levels, this is the problem research centers are fighting.

Re-positioned injectors, shaped piston domes, delayed or late cycle injection, and pulsed injectors seem to show some promise.

VVT is most likely the next phase in throttle-less engine and shows the most promise.


RE: Throttle bodiless Spark Ignition Gasoline Engine?

One other possible engine architecture that did use a form of throttle for load-control, worked by throttling the exhaust.
This was demonstrated at Ford back in the '70's by (I think) Dick Baines.
It was a very simple conversion: used a conventional carburetor without throttle plates for fuel-air mixing.

RE: Throttle bodiless Spark Ignition Gasoline Engine?

Sort of throttle by enforced EGR. But that sounds like a Jacob's brake to me?

Hmm, has anyone tried using infinitely variable EGR as a throttling mechanism?


Greg Locock

RE: Throttle bodiless Spark Ignition Gasoline Engine?

It makes the engine run under high pressure instead of vacuum when throttled. I imagine this increases losses due to pumping efficiencies.
Great for reduced brake wear by extra engine brakeing though.
Also, if carburetored, it would play havoc with the idle, intermediate and power valve circuits


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