APT SmartCarb

[gasgasman]

Pics of the carb on the YZ-taken off the Power APT Facebook page.

[Jakobi]

Originally Posted by Corey

Phil, its all about the signal to the metering rod: The thing to remember is a caburetor is a passive device and can only respond as well as the engine it?s attached to; in terms of airflow and overall efficiencies. The shape of theSmatCarb?s venturi does an outstanding job of communicating mass airflow to the metering rod, insomuch that the caburetor becomes fairly indifferent to the metering rod (more specifically the size of the aperature at the needle nozzle interface), and only shows problems if it is way too lean. I think Glenn stated earlier in this forum that what he thought it sounded like ?is that you can go a lot richer and still have efficient atomization? and he is correct, you can run the carburetor very rich and still have decent performance. An interesting side note is conversely if the metering rod is too lean it simply won?t run hard enough past idle settings to hurt the engine, eliminating burned pistons. You don?t have any intermediate circuits to cheat it long enough to run through to the point of overheating the piston.

We do have different sizes and series of metering rods. Most changes are usually related to displacement of the engine only and have little to do with engine modifications. We typically use only one metering rod, from full mods to totally stock and have excellent results.

The ideal way to change the ?preferred characteristics? with a SmartCarb is venturi size. For riders who like a milder hit with a lot of top end we recommend a 40mm for 250-300cc?s, for those who like a lot of torque and a little less top end a 36mm is recommended and for those who like both we offer a taper bore 40/38mm and 38/36mm.

Corey

2011 GasGas EC300

Good info re carb selection modifying power delivery/curves however not an overly user friendly approach at $xx a pop. The tapered models look like they'd be on the moneys. I like the sound of the 40/38mm model.

Originally Posted by Corey

Nambo, best case for die cast sales will be early spring 2013 and will be announced, with pricing, on APT's website: http://powerapt.com

Thanks for the interest,

Corey

It'd be great if you could let us know on the forum when in production too. For a couple hundred dollars my curiousity would get the best of me.

Originally Posted by GMP

Corey,

I suspected as much, my new bike came with an older 38mm and notched slide and gave me fits jetting it. I'm not so against the 38mm on a 250, I have an '07 bike that just runs perfect with one. My '12 runs a hair softer off the bottom but revs to the moon, I suspect that is some porting variation as all else is the same. What has been the Smartcarb size of choice from GG testing? Is the taper bore a vertical taper, like some other "keyhole" bores?

Glenn,

A bit off topic here but on reading yours again, its very possible the S3 cylinder they have shipped on your bike is ported more towards top end, as was the S3 cylinder I purchased vs the stock cylinder Dmcca had worked with before mine.

Originally Posted by Quoting dmcca

So i got the cylidner on Friday arvo... just had a chance to map it out this morning and compare it to the last stock '11 EC250 i worked on...

Some obvious things about the S3 cylidner...
- it is the exact same basic cylidner as a stock unit, obviously cast from the same batch as the standard cylidners, it just has S3's logo on the side.
- its had some extra work done to the ports over the stock unit and the finish on the ports is MUCH better than the last stock one i had (which was terrible)
- the aux EX ports have been widened
- Main Ex port has been widened and raised to match the timing of the aux EX ports (stock is staggered with Main Ex lower)
- Main and Aux transfers have been widened
- Boost port has not been touched

All pretty standard stuff aimed at more top end power, most likely at the expense of bottom (as to be expected)...

[Corey]

Originally Posted by Jakobi

Corey,

I'm also curious. How does the carb respond to changes in temperature? humidity? etc. I assume these would also have an effect on atmospheric pressure so would be adjusted for by the carbs metering automatically.

Correct, the metering rod senses air density. So whatever affects air density; temps, humidity, dirt (just kidding) is relative and is compensated for.

Corey

[Corey]

Originally Posted by tuxedo dave

If i buy one will you take part trade with all the excess brass i have lying around?
On a more serious note the oval bore options really aren't needed if your not a topend screamer and more of a low to mid lugger.I'm also assuming you can save some money on silencer repacking with the more efficient burn.

The oblong shape of the venturi is not designed so much to accentuate top end performance, whilst also trying to maintain bottom end hit, as it is designed to funnel all of the air possible entering the throat into the trough at the base of the metering rod/nozzle interface.

The taperbore 40/38 and 38/36mm are best tailored for modified engines on specific courses.

[Corey]

Originally Posted by tuxedo dave

I would assume when you mean modded not just a head mod?

Any mod or a combination of mods. If those mods enhance the engines VE then the SmartCarb simply responds to the increases. Or decreases as the case may be

Corey

[tuxedo dave]

One more question for you Corey.If i was to start a ride at sea level and end up at 10000ft by the end of the day would all it take is the odd turn of the knob to adjust the metering rod height to keep it in the sweet spot?

[Corey]

Originally Posted by tuxedo dave

One more question for you Corey.If i was to start a ride at sea level and end up at 10000ft by the end of the day would all it take is the odd turn of the knob to adjust the metering rod height to keep it in the sweet spot?

Yes.

Regards,

Corey

[gasgasman]

Originally Posted by Diggs345

Gasgas man , out of interest what size smartcarb did you get for your bike , and knowing what you know now would you have chose another size ?

Chris

I have the 38mm straight bore.
The riding I do, I seldom go to WFO for long periods. For that reason, the 38 is ideal on my 250.

The power right now is smooth and gets to the ground without a bunch of wheel spin. Although, you can blip the clutch and spool up the engine if you need wheel spin to change the bike's direction.

The bike vibrates less for sure.
I am faster on the bike with the SmartCarb and don't tire as quickly.

[Corey]

Originally Posted by jimjim

Sounds like FI for the two-stroke,I know whats on my Christmas list!

Thanks Jim!

[nambo-trev]

i just spent 700 on new trelleborgs but im going to buy this carb as soon as some more funds free up! i dont think i can wait for the diecast version im way to curious how my 300 will run(and hell billet stuff is cool)