ESE's works engine tuner

[Yow Ling]

I am looking forward to hearing what you think can be done.

I was in at work this afternoon thanks for the cylinders and I see the F81 has been collected. I hope you saw the EFI stuff on the bench, I would be interested in what you think of it.

I am getting some bigger injectors, 650cc/min and a bigger 45L/hr pump. The plan is to use a 650cc injector paired with a 460 and 25L pump paired with a 45 that is switched on by the Ignitec at WOT above 10K rpm or there about.

I am keen to follow your advice and inject into the transfers while the transfer ports are open. And that means there is only 1/3 of the time (120 deg duration) to complete the fuel injection cycle.

So I need much bigger pumps and injectors compared to injecting into the inlet as the inlet is open for 2/3 of the time (230 deg duration) or the crankcase for possibly up to 100% of the time (360 deg duration) where a 25L pump and a smaller injector would do.

How are you going to oil the big end?

[TZ350]

Page 750 links list

Rather than use the site search which usually fails, use Google so to search this site use an ordinary search phrase and after it add

site:www.kiwibiker.co.nz

for example

Frits priceless site:www.kiwibiker.co.nz
or
Frits pisa site:www.kiwibiker.co.nz

the same will work for other sites with the appropriate site address

Mick

Pipes

Attachment 268048

A handy little tool put together by Bucket for checking the BMEP of different Engines.

You change the values in the yellow squares and the answers appear in the green ones. Its a great tool for compairing different bikes and what development potential they may have left and who's telling porkies.

P217

Case com is a very complex subject but a few rules of thumb apply.
The higher the bmep of an engine then the higher the delivery ratio, thus a larger case can store the higher volume of ingested air at a higher pressure and this is then available to the transfer ducts.
But the quality of the duct and port geometry also affects the case com required.
The smaller the case vol (higher ratio) the greater the pressure rise in the case as the piston drops - this suits compromised transfer ducts with little or no inner wall shape, as it helps force the flow around thru the ducts quicker.
Good duct/port geometry allows the use of a bigger case as they don’t need a large pressure ratio across the port to initiate good flow.
Lastly is the effect of the pipe geometry, the diffuser sucks like hell on the Ex port around BDC, pulling flow thru the transfers, and it is important to match the pipe diameter ( and thus the diffuser included angles) to the transfer port/duct geometry.

Suck too hard on crap transfers and they loose directional control - giving greater short-circuiting out the Exhaust port.

Thus you have a Catch22 in that you need a small case to speed up the flow, but this limits the available stored mixture, and you want to suck on the transfers as much as possible, but no so much as to loose the control of the flow direction - or to speed up the loop velocity excessively thus reducing the trapping efficiency..

One myth that needs busting here is that the bulk of the flow thru the transfers is initiated by the piston dropping. This happens in lawn mowers, not racing engines.

Pipe diffuser suction when the piston is around BDC forces the bulk of the flow volume, NOT the pressure in the case forcing flow up the ducts.
When the transfers open there is more pressure in the cylinder than in the case.
Thus we get flow reversal at the initial transfer opening point.
This also means that the transfer port that opens first - flows last, as it has the greatest flow reversal affect, down the duct.

In general, high bmep engines that by default will have good port/duct geometry, will like a case com down near 1.3:1, lower performance engines with crap transfer/duct geometry will perform best with the ratio higher, up near 1.4:1.
Thus as you develop an engine, increasing its efficiency with better porting, then this will allow the use of a bigger case, and bigger pipe diameter/vol, to work with that - the two go hand in hand.

Page 470 its worth a look at the original post.

The big thing to come out of the last ten pages seems to be that insufficient blow down time area can lead to over heating by having excessive hot exhaust gas entering the transfer ports and over heating the engine.

On the original post Husa has now placed a spread sheet with rod dimensions.

There are other link/post collections on most other decade pages ......

Basic 2 stroke Tuning

by Eric Gorr

---

Changing the power band of your dirt bike engine is simple when you know the basics. A myriad of different aftermarket accessories is available for you to custom tune your bike to better suit your needs. The most common mistake is to choose the wrong combination of engine components, making the engine run worse than stock. Use this as a guide to inform yourself on how changes in engine components can alter the powerband of bike's engine. Use the guide at the end of the chapter to map out your strategy for changing engine components to create the perfect power band.

TWO-STROKE PRINCIPLES
Although a two-stroke engine has less moving parts than a four-stroke engine, a two-stroke is a complex engine because it relies on gas dynamics. There are different phases taking place in the crankcase and in the cylinder bore at the same time. That is how a two-stroke engine completes a power cycle in only 360 degrees of crankshaft rotation compared to a four-stroke engine which requires 720 degrees of crankshaft rotation to complete one power cycle. These four drawings give an explanation of how a two-stroke engine works.
1) Starting with the piston at top dead center (TDC 0 degrees) ignition has occurred and the gasses in the combustion chamber are expanding and pushing down the piston. This pressurizes the crankcase causing the reed valve to close. At about 90 degrees after TDC the exhaust port opens ending the power stroke. A pressure wave of hot expanding gasses flows down the exhaust pipe. The blow-down phase has started and will end when the transfer ports open. The pressure in the cylinder must blow-down to below the pressure in the crankcase in order for the unburned mixture gasses to flow out the transfer ports during the scavenging phase.
2) Now the transfer ports are uncovered at about 120 degrees after TDC. The scavenging phase has begun. Meaning that the unburned mixture gasses are flowing out of the transfers and merging together to form a loop. The gasses travel up the back side of the cylinder and loops around in the cylinder head to scavenge out the burnt mixture gasses from the previous power stroke. It is critical that the burnt gasses are scavenged from the combustion chamber, in order to make room for as much unburned gasses as possible. That is the key to making more power in a two-stroke engine. The more unburned gasses you can squeeze into the combustion chamber, the more the engine will produce. Now the loop of unburned mixture gasses have traveled into the exhaust pipe's header section. The gasses aren't lost because a compression pressure wave has reflected from the end of the exhaust pipe, to pack the unburned gasses back into the cylinder before the piston closes off the port. This is the unique super-charging effect of two-stroke engines. The main advantage of two-stroke engines is that they can combust more volume of fuel/air mixture than the swept volume of the engine. Example: A 125cc four-stroke engine combusts about 110cc of F/A gasses but a 125cc two-stroke engine combusts about 180cc of F/A gasses.
3) Now the crankshaft has rotated past bottom dead center (BDC 180 degrees) and the piston is on the upstroke. The compression wave reflected from the exhaust pipe is packing the unburned gasses back in through the exhaust port as the piston closes off the port the start the compression phase. In the crankcase the pressure is below atmospheric producing a vacuum and a fresh charge of unburned mixture gasses is flowing through the reed valve into the crankcase.
4) The unburned mixture gasses are compresses and just before the piston reaches TDC, the ignition system discharges a spark causing the gasses to ignite and start the process all over again.

CYLINDER PORTING
The cylinder ports are designed to produce a certain power characteristic over a fairly narrow rpm band. Porting or tuning is a metal machining process performed to the cylinder ports (exhaust & transfers) that alters the timing, area size, and angles of the ports in order to adjust the power band to better suit the rider's demands. For example, a veteran trail rider riding an RM250 in the Rocky mountain region of the USA will need to adjust the power band for more low end power because of the steep hill climbs and the lower air density of higher altitudes. The only way to determine what changes will be needed to the engine is by measuring and calculating the stock engine's specifications. The most critical measurement is termed port-time-area. This term is a calculation of a port's size area and timing in relation to the displacement of the engine and the rpm. Experienced tuners know what the port-time-area values of the exhaust and transfer ports should be for an engine used for a particular purpose. In general, if a tuner wants to adjust the engine's power band for more low to mid range he would do the following things. Turn down the cylinder base on a lathe to increase the effective stroke (distance from TDC to exhaust port opening). This also retards the exhaust port timing and shortens the duration and increases the compression ratio. Next the transfer ports should be narrowed and re-angled with epoxy to reduce the port-time-area for an rpm peak of 7,000 rpm. The rear transfer ports need to be re-angled so they oppose each other rather than pointing forward to the exhaust port. This changes the loop scavenging flow pattern of the transfer ports to improve scavenging efficiency at low to mid rpm (2,000 to 5,000 rpm). An expert rider racing mx in England would want to adjust the power band of an RM250 for more mid to top end power. The cylinder would need to be tuned radically different than for trail riding.
Here is an example. The exhaust port would have to be raised and widened to change the port-time-area peak for a higher rpm (9,000 rpm). For either of these cylinder modifications to be effective, other engine components would also need to be changed to get the desired tuning effect.

CYLINDER HEAD
Cylinder heads can be reshaped to change the power band. Generally speaking, a cylinder head with a small diameter and deep combustion chamber, and a wide squish band (60% of the bore area). Combined with a compression ratio of 9 to 1 is ideally suited for low to mid range power. A cylinder head with a wide shallow chamber and a narrow squish band (35-45% of bore area) and a compression ratio of 8 to 1, is ideally suited for high rpm power.
There are many reasons why a particular head design works for certain types of racing. For example; a head with a wide squish band and a high compression ratio will generate high turbulence in the combustion chamber. This turbulence is termed Maximum Squish Velocity, MSV is rated in meters per second (m/s). A cylinder head designed for supercross should have an MSV rating of 28m/s. Computer design software is used to calculate the MSV for head designs. In the model tuning tips chapters of this book, all the head specs quoted have MSV ratings designed for the intended power band changes.

CRANKSHAFT
There are two popular mods hop-up companies are doing to crankshafts; stroking and turbo-vaning. Stroking means to increase the distance from the crank center to the big end pin center. There are two techniques for stroking crankshafts; weld old hole and re-drill a new big end pin hole, or by installing an off-set big end pin. The method of weld and re-drilling is labor intensive. The off-set pin system is cheap, non-permanent, and can be changed quickly. In general, increasing the stroke of a crankshaft boosts the mid range power but decreases the engine's rpm peak.
The term "Turbo-Crank" refers to a modification to the crankshaft of a two-stroke engine, whereby scoops are fastened to the crank in order to improve the volumetric efficiency of the engine. Every decade some hop-up shop revives this old idea and gives it a trendy name with product promises that it can't live up to. These crank modifications cause oil to be directed away from the connecting rod and often times the vanes will detach from the crank at high rpm, causing catastrophic engine damage. My advice, don't waste the $750!

CARBURETOR
In general a small diameter carburetor will have high velocity and a good flow characteristic for a low to mid rpm power band. A large diameter carburetor works better for high rpm power bands. For 125 cc engines a 34mm carburetor works well for supercross and enduro and a 36 or 338 mm carburetor works best for fast mx tracks. For 250 cc engines a 36 mm carburetor works best for low to mid power bands and a 39.5 mm carburetor works best for top end power bands. Recently there has been a trend in the use of air-foils and rifle-boring for carbs. These innovations are designed to improve air flow at low throttle openings. Some companies sell carb inserts, to change the diameter of a carb. Typically a set of inserts is sold with a service of over boring the carb. For example; a carb for a 250cc bike (38mm) will be bored to 39.5mm and two inserts will be supplied. The carb can then be restricted to a diameter of 36 or 38mm.

REED VALVE
Think of a reed valve like a carburetor, bigger valves with large flow-areas work best for high rpm power bands. In general, reed valves with six or more petals are used for high rpm engines. Reed valves with four petals are used for dirt bikes that need strong low end and mid range power. There are three other factors to consider when choosing a reed valve. The angle of the reed valve, the type of reed material, and the petal thickness. The two common reed valve angles are 30 and 45 degrees. A 30-degree valve is designed for low to mid rpm and a 45 degree valve is designed for high rpm. There are two types of reed petal materials commonly used, carbon fiber and fiberglass. Carbon fiber reeds are lightweight but relatively stiff (spring tension) and designed to resist fluttering at high rpm. Fiberglass reeds have relatively low spring tension so they instantly respond to pressure that changes in the crankcase, however the low spring tension makes them flutter at high rpm thereby limiting the amount of power. Fiberglass reed petals are good for low to mid power bands and carbon fiber reeds are better for high rpm engines.
Boyesen Dual Stage reeds have a large thick base reed with a smaller thinner reed mounted on top. This setup widens the rpm range where the reed valve flows best. The thin reeds respond to low rpm and low frequency pressure pulses. The thick reeds respond to higher-pressure pulses and resist fluttering at high rpm. A Boyesen RAD valve is different than a traditional reed valve. Bikes with single rear shocks have off-set carbs. The RAD valve is designed to redistribute the gas flow to the crankcases evenly. A RAD valve will give an overall improvement to the power band. Polini of Italy makes a reed valve called the Supervalve. It features several mini sets of reeds positioned vertically instead of horizontally like conventional reed valves. These valves are excellent for enduro riding because of improved throttle response. In tests on an inertia chassis dyno show the Supervalve to be superior when power shifting. However these valves don't generate greater peak power than conventional reed valves. Supervalves are imported to America and sold by Moto Italia in Maine.

EXHAUST PIPE
The exhaust pipe of a two-stroke engine attempts to harness the energy of the pressure waves from combustion. The diameter and length of the five main sections of a pipe, are critical to producing the desired power band. The five sections of the pipe are the head pipe, diffuser cone, dwell, baffle cone, and the stinger. In general, after market exhaust pipes shift the power band up the rpm scale. Most pipes are designed for original cylinders not tuned cylinders. Companies like MOTOWERKS custom computer design and fabricate pipes based on the cylinder specifications and the type of power band targeted.

SILENCER
Silencers come in all sorts of shapes and sizes. A long silencer with a small diameter enhance the low to mid power because it increases the bleed-down pressure in the pipe. A silencer with a short length and a large core diameter provides the best bleed-down pressure for a high rpm engine. Too much pressure in the pipe at high rpm will radically increase the temperature of the piston crown and could cause the piston to seize in the cylinder.

FLYWHEEL WEIGHTS
The flywheel is weighted to improve the engine's tractability at low to mid rpms. There are two different types of flywheel weights, weld-on and thread-on. A-Loop performs the weld-on flywheel weight service. Steahly makes thread-on flywheel weights. This product threads onto the fine left-hand threads that are on the center hub of most Japanese magneto rotors. normally the threads are used for the flywheel remover tool. Thread-on flywheel weights can only be used if the threads on the flywheel are in perfect condition. The advantage to weld-on weights is they can't possibly come off.
External rotor flywheels have a larger diameter than internal rotor flywheels so they have greater flywheel inertia. Internal rotor flywheels give quicker throttle response.

AFFECTS OF THE IGNITION TIMING
Here is how changes in the static ignition timing affects the power band of a Japanese dirt bike. Advancing the timing will make the power band hit harder in the mid range but fall flat on top end. Advancing the timing gives the flame front in the combustion chamber, adequate time to travel across the chamber to form a great pressure rise. The rapid pressure rise contributes to a power band's "Hit". In some cases the pressure rise can be so great that it causes an audible pinging noise from the engine. As the engine rpm increases, the pressure in the cylinder becomes so great that pumping losses occur to the piston. That is why engines with too much spark advance or too high of a compression ratio, run flat at high rpm.
Retarding the timing will make the power band smoother in the mid-range and give more top end over rev. When the spark fires closer to TDC, the pressure rise in the cylinder isn't as great. The emphasis is on gaining more degrees of retard at high rpm. This causes a shift of the heat from the cylinder to the pipe. This can prevent the piston from melting at high rpm, but the biggest benefit is how the heat affects the tuning in the pipe. When the temperature rises, the velocity of the waves in the pipe increases. At high rpm this can cause a closer synchronization between the returning compression wave and the piston speed. This effectively extends the rpm peak of the pipe.

HOW TO ADJUST THE TIMING
Rotating the stator plate relative to the crankcases changes the timing. Most manufacturers stamp the stator plate with three marks, near the plate's mounting holes. The center mark is the standard timing. If you loosen the plate mounting bolts and rotate the stator plate clockwise to the flywheel's rotation, that will advance the ignition timing. If you rotate the stator plate counterclockwise to the flywheel's rotation, that will retard the ignition timing. Never rotate the stator plate more than .028in/.7mm past the original standard timing mark. Kawasaki and Yamaha stator plates are marked. Honda stators have a sheet metal plate riveted to one of the mount holes. This plate insures that the stator can only be installed in one position. If you want to adjust the ignition timing on a Honda CR, you'll have to file the sheet metal plate, with a 1/4in rat-tail file.

AFTERMARKET IGNITIONS
The latest innovation in ignition systems is an internal rotor with bolt-on discs that function as flywheel weights. PVL of Germany makes these ignitions for modern Japanese dirt bikes. Another advantage to the PVL ignition is that they make a variety of disc weights so you can tune the flywheel inertia to suit racetrack conditions.
MSD is an aftermarket ignition component manufacturer. They are making ignition systems for CR and RM 125 and 250. MSD's ignition system features the ability to control the number of degrees of advance and retard. These aftermarket ignition systems sell for less than the OEM equivalent.

TIPS FOR BIG BORING CYLINDERS
In the mid nineties, European electro-plating companies started service centers in America. This made it possible to over bore cylinders and electro-plate them to precise tolerances. This process is used by tuners to push an engine's displacement to the limit of the racing class rules, or make the engine legal for a different class.
When you change the displacement of the cylinder, there are so many factors to consider. Factors like; port-time-area, compression ratio, exhaust valves, carb jetting, silencer, and ignition timing. Here is an explanation of what you need to do when planning to over bore a cylinder.
Port-Time-Area - This is the size and opening timing of the exhaust and intake ports, versus the size of the cylinder and the rpm. When increasing the displacement of the cylinder, the cylinder has to be bored to a larger diameter. The ports enter the cylinder at angles of approximately 15 degrees. When the cylinder is bore is made larger, the transfer ports drop in height and retard the timing and duration of those ports. The exhaust port gets narrower. If you just over bored and plated a cylinder, it would have much more low end power than stock. Normally tuners have to adjust the ports to suit the demands of the larger engine displacement. Those exact dimension changes can be determined with TSR's Time-Area computer program.
Cylinder Head - The head's dimensions must be changed to suit the larger piston. The bore must be enlarged to the finished bore size. Then the squish band deck height must be set to the proper installed squish clearance. The larger bore size will increase the squish turbulence so the head's squish band may have to be narrowed. The volume of the head must be increased to suit the change in cylinder displacement. Otherwise the engine will run flat at high rpm or ping in the mid range from detonation.
Exhaust Valves - When the bore size is increased, the exhaust valve to piston clearance must be checked and adjusted. This pertains to the types of exhaust valves that operate within close proximity of the piston. If the exhaust valves aren't modified, the piston could strike the valves and cause serious engine damage.
Carb - The piston diameter and carb bore diameter are closely related. The larger the ratio between the piston size and the carb size, the higher the intake velocity. That makes the jetting richer. Figure on leaning the jetting after an engine is over bored.
Ignition Timing - The timing can be retarded to improve the over rev. Normally over bored engines tend to run flat on top end.
Pipe and Silencer - Because only the bore size is changed, you won't need a longer pipe only one with a larger center section. FMF's line of Fatty pipes work great on engines with larger displacement. Some riders use silencers that are shorter with larger outlets to adjust the back-pressure in the pipe for the larger engine displacement.

[TZ350]

How are you going to oil the big end?

That has been on my mind. Flettner says enough oil finds its way around to lubricate everything. But I will nead to ask him more about that.

I can see how oil can dribble down the transfer port walls to lubricate the main brgs. But the big end??? its not intuitively obvious....

If Flettners engine has an oil slinger on a main brg that feeds oil to the big end then I will need to think of something like that my self, there is room for one, may be a good idea any way.

[husaberg]

My guess is reversion and gravity. The heavier components should drop off under pressure.
At the end of the day it will be suck and see.
If it doesn't work there is always a set up to direct a small injector at the big end or maybe the set up used on compressed air tools?
Fletners set up does seem to be very oily though even on Alcohol.

[Bert]

My guess is reversion and gravity. The heavier components should drop off under pressure.
At the end of the day it will be suck and see.
If it doesn't work there is always a set up to direct a small injector at the big end or maybe the set up used on compressed air tools?
Fletners set up does seem to be very oily though even on Alcohol.

It is something that I've been thinking about as well...
I was looking at putting the oil pump back on and hoping that the right parts would get enough oil.

Will the fuel injection system actually handle pre-mixed fuel? (I should have asked that originally)...

650cc injectors; right time for a re-think....

[Yow Ling]

Suzuki gt 750 used to supply oil directly to the mains and big end, this was done with a 2t oil pump and a galley in the crank 4t style , i think this was their posiforce system, they may have used it on tiddlers too , hard to remember as Im only 50

[husaberg]

Suzuki gt 750 used to supply oil directly to the mains and big end, this was done with a 2t oil pump and a galley in the crank 4t style , i think this was their posiforce system, they may have used it on tiddlers too , hard to remember as Im only 50

Yamaha also had some fiendishly complex auto lube systems on the 60's multi GP bikes.



Honda's approach on the MB was ingenious in its simplicity.

Yes looking at the engine diagram for the V4 it does look like it had pressure feed big ends but it reved to over 17000......


I think the wolf/stinger may have pressure feed the big ends as well?
But i are not yet 40 so not sure.

[TerraRoot]

how are these big pumps getting powered? gonna need a fair amount of amps..

[Ocean1]

Suzuki gt 750 used to supply oil directly to the mains and big end, this was done with a 2t oil pump and a galley in the crank 4t style , i think this was their posiforce system, they may have used it on tiddlers too , hard to remember as Im only 50

They also used it on TS185s, and I suspect TS125s. Would be an easy solution.

[TZ350]

They also used it on TS185s, and I suspect TS125s. Would be an easy solution.

Posi Force lubrication is the fall back position.

When I raced a Suzuki TR250R it had pre mix and a Posi Force pump wired 30% open.



Geoff Perrys TR500R had the same setup.

To start with I intend copying Flettners layout of injectors in the rear transfer port.

how are these big pumps getting powered? gonna need a fair amount of amps..

Big battery supplemented with a small generator, a semi total loss system. And the big pump wont run all the time, it will switch on as demand requires.

[Flettner]

I guess I've been lucky, I put my injectors here to hide them. As it happened this was the right compromise. These two 720 cc injectors flow enough fuel on E90 to be fully fueling at about 180 degrees timing. I fire these injectors at 60 degrees after TDC so there is a time when transfers are not open but fuel is waiting at the transfer catchment ready to go. Because this is the back transfer it seems enough oil is feed down to the bigend. It's done fifty hours now with no bigend or main bearing problems.

[husaberg]

TZ bet me to the pic


As Neil said i think it may be a solution to a problem that hasn't occurred as of yet.

Actually would the GP125 be set up like this as standard?

[Moooools]

You got it .

There is also a second lesson:
Working on your engine may improve your lap times a couple of tenths. Working on your tires and suspension may be ten times more effective.

I am quite curious as to whether top level teams go to the expense of getting their tyres tested and acquiring proper tyre data.

It would be a damn useful thing to have, but most data is held onto very tightly by those who commission it. Probably due to the price tag of the testing.

[TZ350]

As Neil said i think it may be a solution to a problem that hasn't occurred as of yet.

Yes ....

Actually would the GP125 be set up like this as standard?

No ....

[Grumph]

Around 50 years ago when EFI wasn't even a dot on the horizon, Irving suggested constant flow injection via the big end. Hilborn injection was pretty much state of the art then with Lucas and Bosch just getting progress on mechanical injecion.
It's still a viable scheme - just vary the pump output to suit.