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Old 04-30-2019, 02:55 AM
Jhoppe Jhoppe is offline
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Default TCT vs. Mikuni vm22

Hey everybody! I picked up a predator 212 for a off road cart I have and I want to upgrade the carb. I was looking at the Tillotson TCT mechanical fuel injection and the mikuni vm22 and I'm not sure which would be best for my application. The engine has a stage 1 kit and I am going to remove the governor. Possibly a stage 2 kit in the future so she will spin 7500 RPMs. Has anyone used the TCT? Maybe even used both?
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Old 04-30-2019, 08:21 AM
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With the Mikuni theres a bunch of info on tuning them... there is a bunch of parts..... basically have already a good reputation...
The TCT carb, as far as I can tell...isnt really re jetable... its new... not much info on tuning and using it in an performance setting....
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Old 04-30-2019, 11:06 AM
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TCT carbs better than a stock carburetor on a stock engine. Now that your engine is not stock, the Mikuni will blow the TCT out of the water no matter what. TCT carburetor really doesn’t stand out as very much better than a stock carb.
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Old 04-30-2019, 12:04 PM
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I know that cars and cameras used it in there stage 2 baja warrior bike and didn't have any problems, but they didn't sing its praises either. They still put mikunis on everything. So I am skeptical. I like the idea of fuel injection though.
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Old 04-30-2019, 03:03 PM
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Well, a mechanical fuel injection like the Tillie TCT is different from say and EFI system. If you put the TCT on and expect the performance of an EFI, you are probably mistaken.
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Old 04-30-2019, 03:19 PM
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Quote:
Originally Posted by JTSpeedDemon View Post
Well, a mechanical fuel injection like the Tillie TCT is different from say and EFI system. If you put the TCT on and expect the performance of an EFI, you are probably mistaken.
TCT IS NOT MFI. ITS A CARBURETOR NO MATTER WHAT THE ADVERTISING SAYS. MFI needs a fuel pump, pressure powered injectors and a air metering system. The TCT has an easily adjustible AFR...so an adjustible jet more or less.

Also note EFI has adjustible tuning curves so it can do all sorts of crazy things you could never reasonably expect a carb to ever be able to do.
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Old 05-04-2019, 04:14 AM
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I know that the TCT isn't the be all end all. It's just better than what I have! I have also read it is not a true mechanical fuel injection. I'm not too worried about that. I am just looking for something better than stock and I dont have a whole lotta cash. The mikuni knock off and the TCT are both around $40-50. Worst case scenario the carb I buy goes on the tecumseh I have that needs a carb upgrade and I pick up the other next month for the predator. I would just rather only need to buy one.
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Old 05-04-2019, 09:12 AM
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Then get the one you know can do the best...Mikuni.
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Old 05-05-2019, 08:27 AM
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That may be true, but the TCT has some interesting plus sides. I like the extra adjustability and the videos on it are positive
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Old 05-05-2019, 09:55 AM
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get whatever you want, but know that the TCT is marginally better than stock carb. Stock carbs flow in the low 40 cfm range, and a 22mm mikuni will flow at 88 cfm. The TCT is tuneable, but the mikuni outperforms the TCT in every way possible, you can tune idle mixture, part throttle mixture, and wide open throttle mixture on a mikuni. ANY slide carburetor (mikuni, keihin, makuni, PZ, knock-offs etc) Will provide better throttle response, better tune-ability, more flow, and more horsepower.

A TCT was basically designed to let your lawnmower or generator run at the right fuel mixture at 2200 rpm and 3600 rpm. Outside of this very small window, you will suffocate your engine at high rpms, and end up buying a mikuni anyway to avoid the bottleneck in flow. Beyond taking off the stock exhaust and intake, the carburetor is the worst flowing part out of the whole engine. The stock head flows in the 60 something CFM range, and with some porting, you can get the head to flow about 65-90 cfm with stock or slightly oversize valves.
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Old 05-05-2019, 10:50 AM
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Quote:
Originally Posted by Tpdingo View Post
TCT IS NOT MFI. ITS A CARBURETOR NO MATTER WHAT THE ADVERTISING SAYS. MFI needs a fuel pump, pressure powered injectors and a air metering system. The TCT has an easily adjustible AFR...
Nono.. it's some sort of dumbed down MFI alright..
the vacuum pulse from the engine actuates a plunger which pressurizes a metered amount of fuel being injected
into the venturi..
air metering is actually sublemented by the amount of vacuum in the throttlebody of the carb..
(more vacuum means the plunger has a wider throw and loads more fuel)

that's why the carb is only suitable for a very narrow set of combustion volume (160-220cc)
otherwise the metering would be off.. it can be dialed in according to combustion volume within a suitable range [for above cc engines].

it's not as exact as a proper EFI, and maybe not even as exact as a first gen MFI... but it's certainly not 'just your ordinary carb' either.

The idea is actually quite clever and it's not marginally but ALOT better than just a rejetted stock carb.
Not as tunable as a mikuni slide carb .. by far not.

But here's the point:
Say you have two perfectly identical engines, both setup for the same peak horsepower and torque
one of which running the TCT and the other say a rejetted stock or a slide mikuni.
Since the TCT can adjust a significant portion of the fuel as it's needed it does save fuel.
And if you need just 10% les fuel on board to finish a race you might have just the advantage you need
Also since the vacuum increases most when you try to increase rpm,
it injects most at acceleration.. which makes throttleresponse much better compared to any other venturi style.. it's even hard to match that with a slide carb I'd say.

Anyways, truth is.. if you care enough to put some hours of testing and setting into a mikuni
(adjust for daily weather changes and such) it certainly can push the same engine to a higher performance than a TCT would be able to,
even IF you invest a similar time to reset the TCT on a daily basis.

And here's where smartcarbs come in...
a terribly expensive crossbread of a TCT-style fuel injection carb and a mikuni slide carb...
tuneable as the mikuni would be with all the benefits a slide carb has over a venturi style.
PLUS the vakuum metered additional drop of fuel injected whenever needed.

if you're willing to spend the money and are torn between a mikuni and a TCT being unable to decide... THAT is what you want

A TCT needs to be dialed in as any carb would need to be, maybe more;
just not as much as a Mikuni style slider
I wouldn't call the benefit marginally personally;
Since same power with less fuel to me is still a noteworthy benefit,
and less fuel and slightly more power to me is great;
but that's a matter of perspective.

For non racing hobbyists
that just wants a bit more throttle response and a snappier ride,
maybe a tad more power and torque
the TCT is the ideal carb (once properly set up).

If you want Top Speed dyno performance only
or are actually competing in a race
and don't care about wasting fuel..
there's nothing but a mikuni IMHO

'sid
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Old 05-05-2019, 06:25 PM
Jhoppe Jhoppe is offline
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The incredibly informed sid being helpful as always! Thank you! I think I'm gonna give the TCT a shot. I saw that it could run propane with the proper setup. Not in my plans, but maybe a propane kart could be cool! As for the flow it ran a stage 2 Baja warrior for cars and cameras just fine.... til they opened up the head. I'm not going to port the head. I MIGHT go in and just clean up the factory casting marks at the most.
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Old 05-13-2019, 08:23 PM
Jhoppe Jhoppe is offline
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Has anyone heard whether they actually made a carb for the 420? I was thinking that would work with a highly modded 212 engine should I get that far.
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