[Monkee]

So this is something i've been wondering for a while while it seems like the TPS governs the amount of retard or advance depending on load and RPM. For many CDI bikes i know they use some kind of air suction to determine how much timing to put into it.

I've heard some people just forfeiting the TPS altogether and not getting any sort of pinging or knock. Does anyone have a more in depth explanation or perhaps experience?

I'd like to learn more about the role the TPS plays in the ignition since the older bullets didnt have a TPS but were still TCI ingition i believe?

[SteveThackery]

What does TCI stand for?

The TPS is used, along with the MAP sensor, to determine the load on the engine. The ECU then determines the optimum amount of fuel to inject and the optimum ignition timing.  The engine oil temperature sensor is also taken into account.

I've never done it, but I would strongly suspect that disconnecting the TPS will illuminate the MIL and put the bike into "get you home" mode.

By that, I mean that the ECU can estimate the engine load without the help of the TPS. However, the load estimation will be less accurate, so the bike should still run but the mixture and ignition timing will be less "perfect" than when all sensors are working.

Most of this is driven by emission regulations. The information provided by the various sensors allows the ECU to operate the engine in a way that minimises emissions.

This article gives a great overview, explaining the differences between alpha-n speed-density algorithms:

https://www.holley.com/blog/post/fuel_injection_fundamentals_understanding_the_three_different_fueling_strategies/#:~:text=The%20Alpha-N%20style%20of%20engine%20tuning%20looks%20at,a%20boosted%20motor%20of%20any%20type%2C”%20says%20Flynn.

[tooseevee]

What does TCI stand for?

           Transistor Controlled Ignition or Transistor Coil Ignition. My AVL has TCI (the green one). I think later ones were CDI?

[Monkee]

           Transistor Controlled Ignition or Transistor Coil Ignition. My AVL has TCI (the green one). I think later ones were CDI?

As far I can see there were none that were CDI? I may be wrong. but does your AVL have a TPS?

[Adrian II]

Are we talking about an Indian market 500 UCE Bullet fitted with a carburettor from the factory, here?

These were on sale alongside EFI models in India until a few years ago, but in this case the CV carbs used DO have TPS. There's no ECU in the fuel-injected sense, but the TPS is linked to the TCI ignition module on these bikes. Someone in India was marketing the TPS carbs as a kit to retro-fit to EFI models.

If the TCI is designed to work in tandem with a TPS, leave it alone, or fit the TCI off an earlier model, e.g the 500 AVL Machismo or Electra-X.

Royal Enfield (India) had three CDI ignition models in the range, the 2002 350 Electra, the A350 kick start Machismo and the 350 kick start Thunderbird, AFAIK the auto-advance was built into the CDI controller electronically, there's certainly no vacuum ignition control on these.

The AVL models came with CV carbs from the factory (apart from the Dell'Orto PHBHs fitted to early A350 Machismos) but no TPS, and definitely not on the after-market carburettors many of us are using.

A.

[tooseevee]

As far I can see there were none that were CDI? I may be wrong. but does your AVL have a TPS?

     I should have been clearer. I didn't mean later AVLs, I meant later Royal Enfields.

[SteveThackery]

As far I can see there were none that were CDI? I may be wrong. but does your AVL have a TPS?

Just a point - we're in the UCE forum here. I don't want us to get into a state of confusion. 

[Monkee]

Are we talking about an Indian market 500 UCE Bullet fitted with a carburettor from the factory, here?

These were on sale alongside EFI models in India until a few years ago, but in this case the CV carbs used DO have TPS. There's no ECU in the fuel-injected sense, but the TPS is linked to the TCI ignition module on these bikes. Someone in India was marketing the TPS carbs as a kit to retro-fit to EFI models.

If the TCI is designed to work in tandem with a TPS, leave it alone, or fit the TCI off an earlier model, e.g the 500 AVL Machismo or Electra-X.

Royal Enfield (India) had three CDI ignition models in the range, the 2002 350 Electra, the A350 kick start Machismo and the 350 kick start Thunderbird, AFAIK the auto-advance was built into the CDI controller electronically, there's certainly no vacuum ignition control on these.

The AVL models came with CV carbs from the factory (apart from the Dell'Orto PHBHs fitted to early A350 Machismos) but no TPS, and definitely not on the after-market carburettors many of us are using.

A.

Ah yes this is what i've seen as well. I was wondering if it was possible to fit a non TPS equipped carb like an Amal or Mikuni with the brown multicurve TCI and if that would have any negative effects, or if alternatives there were TCI ignition modules that didn't require a TPS but were also fitted on the UCEs

[Crabsapper]

My 2020 UCE C5 has been fitted with a Mikuni, as well as the wiring loom, stator and rotor from carbed bikes.
I've used both the green and brown TCI boxes, both work fine.
The green TCI has no TPS input, but the brown does. With the brown TCI fitted obviously the TPS is left disconnected, and the bike runs fine.....I can't tell the difference between that and the green. Both pull hard up to and past an indicated 80mph with no discernible difference in performance.
I was told the brown TCI defaults to a more retarded curve with the TPS disconnected, but I'm reluctant to accept that.
Current using the green as starting seems easier.

[Monkee]

My 2020 UCE C5 has been fitted with a Mikuni, as well as the wiring loom, stator and rotor from carbed bikes.
I've used both the green and brown TCI boxes, both work fine.
The green TCI has no TPS input, but the brown does. With the brown TCI fitted obviously the TPS is left disconnected, and the bike runs fine.....I can't tell the difference between that and the green. Both pull hard up to and past an indicated 80mph with no discernible difference in performance.
I was told the brown TCI defaults to a more retarded curve with the TPS disconnected, but I'm reluctant to accept that.
Current using the green as starting seems easier.

Oh Hey crabsapper! i ordered the parts im just waiting for them. Im thinking of trying out an OKO flatslide or a keihin round slide instead of the VM just because its easier to find repair kits and jetts for them in my area. For the throttle cables i orderd a venhill custom cable kit and will just build my own.

I wonder if theres anyone on the forum who has a definitive answer for the TCI's and TPS. I've read somewhere that on the carbed models the TPS acts like an on/off switch rather than a progressive linear taper kind of thing. i dont know how much truth is in that statement but i'd be a fun discussion to have.

[Monkee]

Also has anyone ever tried running CDI's on their UCE bikes? Reason why im asking is because i once talked to a mechanic who rigged up a dual CDI ignition for I believe was a virago or some other japanese V twin cruiser without a hiccup.

If i understand correctly the main difference between a CDI and TCI are the ingition coils needed? I think CDI calls for a higher resistance ignition coil?

[Adrian II]

The green TCI was a Mk2 version for the AVL originally, brown most likely for the UCE as the TPS on a carb is a later addition as explained above.

What would be the advantage on a UCE Bullet (assume carburettor fitted) from changing from TCI to CDI? There might be some Suzuki-type alternator stator "out there somewhere" with the CDI charging coil which would just happen to fit the Bullet mountings, but it sounds like a lot of hassle. The old AVL CDI igntions were battery-independent, is that what you'd be trying to achieve?

A.

[SteveThackery]

What would be the advantage on a UCE Bullet (assume carburettor fitted) from changing from TCI to CDI?

Probably none. Capacitor discharge ignition is better at lighting up a fouled plug due to its exceptionally fast rise time, hence their popularity on two-strokes. Inductive discharge ignition (which you call TCI) is better at igniting weak mixtures due to its relatively long duration, flaming spark.

Having used both on various cars and bikes over some 50 years, I can say that there is no discernible difference to me.

[Monkee]

Probably none. Capacitor discharge ignition is better at lighting up a fouled plug due to its exceptionally fast rise time, hence their popularity on two-strokes. Inductive discharge ignition (which you call TCI) is better at igniting weak mixtures due to its relatively long duration, flaming spark.

Having used both on various cars and bikes over some 50 years, I can say that there is no discernible difference to me.

To me the only real benefit is the availability of CDIs compared to TCIs in general. thinking way too ahead of myself but i just like knowing if and when i can no longer find OE parts i could rig something up from another bike's ignition.

[Monkee]

The green TCI was a Mk2 version for the AVL originally, brown most likely for the UCE as the TPS on a carb is a later addition as explained above.

What would be the advantage on a UCE Bullet (assume carburettor fitted) from changing from TCI to CDI? There might be some Suzuki-type alternator stator "out there somewhere" with the CDI charging coil which would just happen to fit the Bullet mountings, but it sounds like a lot of hassle. The old AVL CDI igntions were battery-independent, is that what you'd be trying to achieve?

A.

I was thinking if it was possible to forego the battery and be able to kickstart even when the battery was dead flat. But seems like i'd either have to have a custom stator made or find one that fits. But more pressing of my two questions is How much a difference would it be if i were to fit an AVL TCI into a UCE engine to be able to use non TPS equipped carbs