Hayabusa Engines in Car Classes

[JackD]

Look up Bruce Crower's 6 cycle diesel that uses the exhaust heat with water to extract the additional power that water to steam can provide in an otherwise idle cylinder.
Consider the expansion rate of water to steam and see if otherwise waisted heat might be useful.
It is proposed to be a High School project for next school year using one of My RX7s.
Several truck engine builders are interested in his patent.

[Jonny Hotnuts]

RF:

On the downward stroke of the intake of the live cylinder the pressure will be (-) until it reaches bottom and become (0).  This is when the "dead" cylinder valve would open at full compression (+) and passes its F/A into the live cylinder that has a (0) pressure making positive pressure in the cylinder before compression.

The idea is that the live cylinder has already taken in its own fuel air charge BEFORE the dead cylinder pushes its volume into the live cylinder.

All has to do with valve timing.

Still say it would work.

[RichFox]

Maybe you could run the dead side as a two stroke, so that you would get two cylinders full into a holding chamber attached to the intake of the live cylinder. It still takes time to pump the air, even under pressure.

[Dean Los Angeles]

Chain life is not only about the HP you pour into it, but how you manage the pulses. A high speed shot of any drive chain will show every firing pulse slamming its way through the system. Running an open system is just asking for all the lubrication to become salt frosting. D'oh!
Running a closed oil system . . . Woo Hoo! (Yeah, I saw the Simpson's Movie.)

Running a short chain to a jack shaft means the links are in constant flex. As Jack keeps throwing out ideas, maybe you should catch one. Chains are cheap and easy, records are hard.

Same thing with how you couple two engines. How the firing pulses are transmitted into power, or vibration will make, or break the project.

[hotrod]

The math is pretty unforgiving on this one if you double the torque at the crank at a given rpm you must also double the hp at that rpm (at the crank)

Hp =rpm x torque
           5,252

Where you get into interesting side effects is both the coupling system and the other accessory systems.
If engine A generates x hp running by it self, and engine B makes y hp running by itself, if the coupling system is a loss free system like crank of A connected directly to crank of B you should have (A+B) power out. That assumes that there are no other secondary effects going on when you run the two engines simultanously.

For example the power pulses from engine A will try to wind up the crank of engine B so its timing events may have some interesting harmonics or changes in actual timing as power goes up (piston timing under power will not be the same as running by itself). If the two engines draw air from the same intake system, does it really flow 2x the air when both engines are drawing at full song or is it really choking down the engines slightly so that their true power when running together is less than when running solo.

Are the other running conditions also effected by the different heat load of both engines running, their intake temps, exhaust temps oil temps and water temps if water cooled, may all be different when running together than if they were run alone.

You could also get burned by what type of dyno you are running on. If it is an inertial dyno that depends on acceleration of a mass to compute hp, the added inertia of the coupling system when the engines are running together might easily lower your "indicated power" number, where if you put the same setup on a steady state dyno and held it at peak hp rpm long enough for inertia effects to go to zero you would get a higher number.

Not enough data to know, what the case is, but like the JCB streamliner showed sometimes you get some interesting side effects when you run multiple engines in tandem. In their case both turbos would not quite spool up at exactly the same rate, and as the earliest spooling turbo came on boost it would un-load the other engine so its turbo would drop out of boost. As I understand it they had to ride the brakes slightly as the engines came on boost so they would all be under load during that transition to boost period.

Larry

[JackD]

In the case of the twin engine/twin turbo, as the load increased with higher gears and speeds the lagging engine will catch up and go to work.
Dragging the brakes to increase the load only removed available power from the drive train and is a waste of time and energy.
If you want to hurry up the response time for the turbo (spool up), give it a shot of nitrous as the exhaust enters the snail and it will take off like a rocket.
That procedure can be automated for the method challenged.
We could invent something and call it "Snooze Control" and even sell them.

[Dean Los Angeles]

Check out this NHRA video with their super slow motion camera. 1000 fps.
Watch the timing chain on the bike and the rear tire.
http://youtube.com/watch?v=lZ424uUP5t4

[Jonny Hotnuts]

Cool vid DLA

JCB streamliner showed sometimes you get some interesting side effects when you run multiple engines in tandem. In their case both turbos would not quite spool up at exactly the same rate, and as the earliest spooling turbo came on boost it would un-load the other engine so its turbo would drop out of boost. As I understand it they had to ride the brakes slightly as the engines came on boost so they would all be under load during that transition to boost period.

Why not add a balance pipe between the high pressure tubes, both motors will have equal boost.....seems like an easy fix.

[John Burk]

Jonny
In the 1930's when the Germans were designing the VW one of the engine combinations they considered was like your idea except it was a flat four . It was a 2 cycle , the pistons on one side pushed the air into the left cylinders . The carburetor must have been in the transfer tube . Interesting design .
John

[Dean Los Angeles]

Until you actually try to run two engines you would never believe how hard it is to get them "in sync". When they run together it pulls like no tomorrow. When one engine is off a tiny, microscopic bit from the other, it feels like a lead pig.

Twin engine air planes, boats, RC planes and boats, karts, all suffer from sync problems. And LSR too.

[JimL]

A note about the two engines verses one discussion.  During early development of OBDII engines, it became apparent that crankshaft rigidity was going to be a BIG concern for All Speed, All Load Misfire Detection.  You see, a crankshaft doesn't actually revolve at fixed speed while at steady RPM.  It actually accelerates and decelerates enough that we can calculate misfire by looking at Delta (change) of rotation at 36 points per revolution. 

As the piston comes up on compression, the crank slows down (and speeds up during a power stroke)....and this happens for each cylinder in the cycle.  Where it gets tricky is when the main bearings become worn, or the harmonic balancer starts to break up.  Misfire detection becomes inaccurate.  A flexible crank (or block) exacerbates the problem.

You'll also see misfire detected when wheel or road vibration is sufficient to alter crankshaft acceleration during power strokes (a harmonic feedback in the driveline, that matches firing frequency).  That means the the power made by combustion (pressure, which should peak at 11-17 degrees after top dead center) was counteracted by external forces.

This may be the "AHA!" of twin engine arrangements.  Feedback lash within the system is entirely capable of interfering with the peak pressure event.  Remember....if your peak cylinder pressure occurs after about 17 degrees ATDC, the piston is running away from the gas expansion pressure and power falls off DRAMATICALLY.  Note that peak piston acceleration occurs when the pin is about 90 degrees tangent to the crank center/rod angle, which is higher in the cylinder than we tend to believe.

Here's another consideration for twin engine synchronization....if the back lash reaction pressure occurs slightly before top dead center, and the spark event has occurred, the reduction of crankshaft rotation speed will allow cylinder pressure to climb (from BTDC combustion) while the piston is still on the compression stroke.  That results in huge pressure BACK against the piston.  The combustion event duration is dependant on timing and fuel vaporization/pressure.  You can't push backwards against a rising piston without paying the price in lost power (I remember Bultacos that would run backwards with an unlucky kickstart).  I had a Buell that could get hot, sneeze in traffic, and spin the rear tire backwards while I was going forward about 20MPH.....that was irritating!

I suspect the best solution is get as lean as possible (for quickest burn), use low 90% distillation temperature fuel, and get the timing as retarded as possible while seeking that 11-17 degree ATDC peak pressure.  That should minimize the "synching" effect problems of twin engines.  Too much focus on the downstroke of power can easily steer us away from the "pushback" of excessive spark advance and rich mixtures.

Fascinating problem, these twin engine machines!  I'd love to build one just to try to learn more about it.

Regards, JimL   .....see you at Speedweek (with my single engine bike).

[JackD]

All that science and a wrong conclusion.
Try again.

[Sumner]

All that science and a wrong conclusion.
Try again.

Hey Jack, Jim has only made two posts on here and takes the time to really go into a lot of detail with that post, some of which I understood and some that I didn't understand.

If you are going to question his comments maybe he deserves a little more than a "wink" from you.  What is it that you disagree with???

c ya,

Sum

[JackD]

All the guys that did it in just motorcycles for example in Drag racing and LSR will be very disappointed to hear it won't work.
I don't want to have to tell them.
Timing, pulses, flex, and delivery methods are all well known factors but the people that made it work, did it anyway.

OBTW: My "Try it again" gives the opportunity to start over fresh.

[hotrod]

All the guys that did it in just motorcycles for example in Drag racing and LSR will be very disappointed to hear it won't work.

Jack;

In my reading of JimL's post, I don't see any statement that even suggests "it won't work", I think he was just shedding some light on the issues involved for those to whom Timing, pulses, flex, and delivery methods are not  well known factors.

His comments do include some interesting observations. In the turbocharged import world where folks are working with OBDII ECU's rather than after market engine managment solutions "phantom miss, and phantom knock" is an issue even on a short crank.

Many of these kids are running light weight crank pulleys in place of the OEM crankshaft pulley/dampner, and since the engine does not fail in the first 100 miles after they install it, they cannot accept that sometimes it simply does not get along well with the OEM engine control logic. There are a handful of the folks with high power Subaru engines  that get a mysterious drop in power and unexplainable miss at about 5500 rpm that goes away when they pull the light weight pulley off. Unfortunately 98% of them either have no issues or are not good enough tuners to realize they have a problem.

From your earlier comments about the lagging engine catching up, do you suggest that they just "drive through" the problem or perhaps change ignition timing, or crank throw indexing slightly on the more heavily loaded crank (assuming an in-line setup) so that under full load both engines have the same effective timing? The other option would be to put shock couplings in each engines drive to de-couple it from the power pulses of the other.

Larry