ESE's works engine tuner

[Frits Overmars]

No doubt there are some super high expectations being put on the Suter. Anyone have details about the fuel injection it's running? Throttle body injection, crank case or direct?

Shower and throttle body.

[TZ350]

Interesting bell mouth injectors, I would love to know more as I did not have much success with bell mouth injectors myself. I guess because with the rotary valve there was always a rpm dependent reversion hole some place blowing the fuel out instead of sucking it in, maybe different for reed valve engines. Also interesting that the 500 has two injectors, one injector in the bell mouth and a second in the throttle body.




Both high and low speed injectors firing into the bell mouth.



Low speed injector firing into the bell mouth with the high speed injectors firing across the transfer ports and visa versa. Neither configuration worked that well for me.

[Frits Overmars]

Interesting bell mouth injectors, I would love to know more as I did not have much success with bell mouth injectors myself. I guess because with the rotary valve there was always a rpm dependent reversion hole some place blowing the fuel out instead of sucking it in, maybe different for reed valve engines.

It may be different for reed valve engines Rob, but not that different.
In all inlet systems the inlet flow accelerates as long as the pressure upstream of the inlet tract is higher than the downstream pressure.
When both pressures are equal the flow has reached its maximum velocity and because mixture keeps entering the crankcase, the case pressure rises above the upstream pressure and this rising pressure gently slows the flow down to a standstill (or suddenly instead of gently if the inlet port closes too soon, which can happen in both piston port and rotary induction systems).
In any case, the pressure at the crankcase side of the inlet tract will then be higher than the pressure at the bellmouth, and mixture will start flowing back towards the free world. The extend of this backflow may be so small that it is not noticeable at the bellmouth, but it is happening nevertheless. Reed valves do it just as much as other inlet control systems.

I call this phenomenon bounce-back and it should not be confused with the blow-back that occurs when an inlet port closes too late.
Bounce-back mixture never really made it into the crankcase; it returned at the closed door.
Blown-back mixture initially entered the crankcase but then reversed its flow direction because of the rising case pressure before the case was closed.
This rising case pressure resulting in flow reversal has rather little to do with the piston moving down after TDC. It can even happen before TDC if the Helmholtz frequency of the inlet system is too high for the engine revs (low revs, big carb diameter, short inlet tract, small case volume).

By the way, bounce-back may be hardly noticeable, but on the other hand it can be even more vicious than blow-back.
As an experiment I once put a 200 mm elongation tube between the carb and the rotary inlet cover of a 125 cc Rotax.
It lowered the Helmholtz frequency of the inlet system so much that inlet flow velocity was still near its maximum when the inlet disc closed. Bounce-back was so severe that within seconds the dyno room was completely fogged up with mixture. It frightened me to death; a spark would have been enough to blow the roof off.

[TZ350]

Thanks Frits, great explanation.

I also see from simulations with EngMod that the airflow behaviour within the inlet tract can change over the useful rpm range.

Sometimes being completely one way for some of the rpm range, then at another rpm reversing at some point in the inlet cycle and at another rpm point completely changing direction in the inlet tract several times.

All these different inlet tract air flow scenarios can happen while the engine is making good power. And with a 6ms engine revolution, an inlet window of say 2ms and an injection cycle of 3ms, injection timing that avoids air flow bounce back or excessive wall wetting is challenging.



Resonant behaviour in the inlet tract changes with both rpm and throttle position.



My recent EFI efforts have been focused on trying different positions for the small injector and to map the small inlet injectors injection cycle to work with the inlet resonance.

[breezy]

It may be different for reed valve engines Rob, but not that different.
In all inlet systems the inlet flow accelerates as long as the pressure upstream of the inlet tract is higher than the downstream pressure.
When both pressures are equal the flow has reached its maximum velocity and because mixture keeps entering the crankcase, the case pressure rises above the upstream pressure and this rising pressure gently slows the flow down to a standstill (or suddenly instead of gently if the inlet port closes too soon, which can happen in both piston port and rotary induction systems).
In any case, the pressure at the crankcase side of the inlet tract will then be higher than the pressure at the bellmouth, and mixture will start flowing back towards the free world. The extend of this backflow may be so small that it is not noticeable at the bellmouth, but it is happening nevertheless. Reed valves do it just as much as other inlet control systems.

I call this phenomenon bounce-back and it should not be confused with the blow-back that occurs when an inlet port closes too late.
Bounce-back mixture never really made it into the crankcase; it returned at the closed door.
Blown-back mixture initially entered the crankcase but then reversed its flow direction because of the rising case pressure before the case was closed.
This rising case pressure resulting in flow reversal has rather little to do with the piston moving down after TDC. It can even happen before TDC if the Helmholtz frequency of the inlet system is too high for the engine revs (low revs, big carb diameter, short inlet tract, small case volume).

By the way, bounce-back may be hardly noticeable, but on the other hand it can be even more vicious than blow-back.
As an experiment I once put a 200 mm elongation tube between the carb and the rotary inlet cover of a 125 cc Rotax.
It lowered the Helmholtz frequency of the inlet system so much that inlet flow velocity was still near its maximum when the inlet disc closed. Bounce-back was so severe that within seconds the dyno room was completely fogged up with mixture. It frightened me to death; a spark would have been enough to blow the roof off.

so would allowing the inlet elongation tube to vent into another low pressure area once the rotary valve had shut stop this from happening?

[TZ350]

When I first tried the plenum it gave a dramatic boost in torque in the rpm area below the original peak torque curve. Basically it plumped up the area of the torque curve that is negatively affected by the pipe resonance working against the engine's exhaust port timing.

I guess this was a resonant effect between the size of the plenum, it's inlet and the engine's crankcase volume and inlet timing working together to prevent the pipes out of step pressure wave, pushing the fresh mixture back down the transfers, well maybe???.

The positive effect on the torque curve by the plenum was so marked that I am keen to explore it further. I have an idea that a two chambered plenum could work, one for this torque boosting resonance and a butterfly that opens to another chamber when a different plenum volume is required. Or maybe a variable length inlet runner, or combination of both.



But first, to be able to use a plenum without the fuel dropout issues that you get with an outside the plenum carb, I have to perfect the EFI system. If I can't do that I will look at putting the carb inside the plenum itself and feed it with a pump around bypass fuel system like they use on Karts.

[Frits Overmars]

so would allowing the inlet elongation tube to vent into another low pressure area once the rotary valve had shut stop this from happening?

Yes, you could connect a boost bottle to the inlet tract, directly upstream of the inlet disc. But what good would it do? It would only swallow mixture that should have been entering the crankcase in the first place, but that didn't make it because the inlet closed too early.
The long column of mixture in the elongation tube has a lot of inertia which means that it is reluctant to start flowing towards the crankcase. And once it is on the move, it should be allowed to continue filling the crankcase as long as the flow direction is positive, which in turn means that a long inlet tract also requires a long inlet timing. You don't want that because at certain revs it will give a lot of blow-back. Keeping the inlet tract and the inlet timing short will result in a forgiving easy-to-jet engine.

Don't worry about harnessing the pulses in the inlet tract; it would require a tract length of about two/thirds the length of the complete exhaust system (two/thirds because of the lower speed of sound in cold mixture versus hot exhaust gases). In an inlet tract (and even more so in transfer ducts) the pulses are reflected to and fro so many times that they have lost most of their energy by the time they could finally do something good. Bottom line: keep the inlet tract short.

[breezy]

Yes, you could connect a boost bottle to the inlet tract, directly upstream of the inlet disc. But what good would it do? It would only swallow mixture that should have been entering the crankcase in the first place, but that didn't make it because the inlet closed too early.
The long column of mixture in the elongation tube has a lot of inertia which means that it is reluctant to start flowing towards the crankcase. And once it is on the move, it should be allowed to continue filling the crankcase as long as the flow direction is positive, which in turn means that a long inlet tract also requires a long inlet timing. You don't want that because at certain revs it will give a lot of blow-back. Keeping the inlet tract and the inlet timing short will result in a forgiving easy-to-jet engine.

Don't worry about harnessing the pulses in the inlet tract; it would require a tract length of about two/thirds the length of the complete exhaust system (two/thirds because of the lower speed of sound in cold mixture versus hot exhaust gases). In an inlet tract (and even more so in transfer ducts) the pulses are reflected to and fro so many times that they have lost most of their energy by the time they could finally do something good. Bottom line: keep the inlet tract short.

but once the door is shut on the crankcase couldnt another door be opend into an area of low pressure to keep the fuel flow continuous...? doesnt the cylinder pressure fall as the exhaust port opens?

[Frits Overmars]

but once the door is shut on the crankcase couldnt another door be opend into an area of low pressure to keep the fuel flow continuous...? doesnt the cylinder pressure fall as the exhaust port opens?

Sure, you could open a door to the outside world but that would be wasting fuel. Or can you imagine another area of low pressure at say 80° after Top Dead Center?
True, the cylinder pressure falls as soon as the exhaust port opens. But it will take another 40° or so crank degrees before the cylinder pressure has fallen below the normal bounce pressure that was generated at the closing inlet port, assuming that the inlet port timing matches the inlet flow.
This bounce pressure equals the crankcase pressure at the moment of inlet closure. But then the crankcase pressure is raised a bit further by the descending piston while the bounce pressure fades away.
Only if the inlet closes too early, the bounce pressure will be higher than the crankcase pressure. But why would you want to open a door to another area of low pressure (if we could find such an area) when it is so much simpler to keep the inlet door open until the flow velocity has slowed down to zero?

[TZ350]

... once the door is shut on the crankcase couldnt another door be opend ...

Some of the other doors I have tried.



Expansion chamber pressure bleeder. Red line = Open.



Increased crankcase volume. Red line = extra volume.



Variable inlet timing +/- 15 deg. Blue line = -15deg

[TZ350]

24 and 30mm carburettors in back to back test. Blue line = 30mm



Divider in an angled inlet manifold. Blue line = divider.



Tillotson HL360A 24mm pumper carb. Blue line = 28 rwhp.

[TZ350]

The 12rwhp Suzuki GP125 where it all began, Blue line, with a bit of tuning and all the bits and bobs = 31rwhp.



The pistons bridge oiling holes can be sealed with devcon, it lasts. Extra copper cooling fin that is also the squish band. Large 32mm inlet for the Suzuki GP and a drill press makes a handy porting tool.

[richban]

I have been playing around with the exhaust port on the 300 cylinders. I have added some side angle to the port. Not much as the casting is very thin there and could easy pop out into the water jacket. But some has got to be better than the none it has.

Attachment 321776

Turns out some, is 100% better than none when it comes to exhaust port side angle area. I made 2 changes to the bike. Bigger stinger and exhaust port change = 6 more hp peak way less heat and more power and toque everywhere. Can't wait to ride it. There is still more to come from some pipes that wob has kindly designed. A lot more! Also Engmod is bang on with the predictions.

[TZ350]

Good work Rich, looking forward to an on the track performance report.

[Flettner]

Interesting bell mouth injectors, I would love to know more as I did not have much success with bell mouth injectors myself. I guess because with the rotary valve there was always a rpm dependent reversion hole some place blowing the fuel out instead of sucking it in, maybe different for reed valve engines. Also interesting that the 500 has two injectors, one injector in the bell mouth and a second in the throttle body.




Both high and low speed injectors firing into the bell mouth.



Low speed injector firing into the bell mouth with the high speed injectors firing across the transfer ports and visa versa. Neither configuration worked that well for me.

An old piece of (poor) video, the F9 when first set up with EFI and the ball valve. RV slide is also installed and operating here.

Husa, help, I've installed the video wrong? I think. I guess I'm just showing the ball valve at work, if only free running.