TRX250R.ORG
Workshop => Carburetor, Intake, and Exhaust => Topic started by: rablack21 on August 03, 2015, 10:30:21 AM
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Purpose of Trip:
I was having a difficult time getting my 38mm cast carb to run well on my 363 stroker motor. With the help of Corey at APT, we tried several different rods and other changes to address the issues, but to no avail. Something wasn't jiving. So, I drove to APT for a weekend trip to do some testing and dynoing to figure out what the problem was and get the engine running like it should.
Forewords:
I want to start off by saying I have great respect for Corey and APT. Their customer service and tech support has been fanstastic. He has worked very hard to help me out and help figure out the issue that several of us have been dealing with. Even though we are a tiny part of their customer base, they have still tried to do everything to make sure I (and others) are happy with the product. No other carb manufacturer has ever offered to help me in any way, much less not charge me for parts. APT has never charged me a dime for any of the extra parts that they sent me to try. Say what you want, but these guys are top notch in my book.
Time Invested:
I left out to head to Missouri from Tennessee on Thursday afternoon,took a vacation day on Friday, and arrived Friday morning. Corey and I spent from 9am to 11pm working, checking, wrenching, and dynoing Friday night. I spent a total of about 25 hours driving, spent a couple hundred dollars in fuel, and paid for 2 hotel rooms along the way. So please be respectful of any responses that you may have about this thread.
Testing:
test 1:
From riding and testing the carb at home, the issues we were battling was a gurgle at lower rpms like it was rich, but would then be lean and fall on it face in the upper rpms.
Before testing began, we disassembled the carb and inspected and cleaned it to eliminate an possible contamination issues. We started out testing my 38 cast carb with the L072 rod with the airbox and boot removed to eliminate any additional variables (since there was some question about the factory airboot possible causing a shrouding issue with the scoop that is made into the air side bell housing). This is unusual because the carb tends to follow the same linear pattern. Rich down low= rich throughout the whole power range, and vice versa. As soon as we began testing, the gurgling at lower rpms showed up. We took apart the carb again. We discovered that the nozzle (the part that the rod sits in that allows fuel through) orings were damaged and allowing fuel through the outside of the nozzle instead of through the middle where it was supposed to be. So we replaced the parts, assembled, and went back to testing. The gurgle was now gone. After a short amount of clicker adjustment, the engine was running strong and smooth. We then made some hard pulls in 4th gear from 25mph to 55mph and ran from low rpms to max rpm. The engine pulls all the way through very strong. It was finally running exactly like it was supposed to.
test 2:
We installed the stock airbox with stock airboot to test again to see if the airboot shrouding was an issue. We fired the engine up and made multiple runs. The engine was still responsive on the bottom up to midrange, but started falling on it face again in the mid to upper rpms. The step in the factory airboot does in fact cause an airflow issue with the scoop in the bell housing. The scoop is critical to design of the carb.
Main points from testing so far:
1. Nozzle was allowing raw fuel through at lower speeds causing gurgling. Orings damaged during installation or bore for nozzle not smooth enough due to carb casting. Bore smoothed and oring replaced. Gurgling no longer an issue.
2. Factory airboot shrouds scoop causing fueling issue at high rpms. Removed airboot and issue disappears.
3. Engine and carb perform as designed when no shrouding is present. Engine appears to really like the L072 rod at around 30 clicks.
test 3:
After we had the issues with the 38 cast carb resolved, we moved on to testing the 40mm billet for you guys that have the larger carb with the 363 engine. The tested the engine without the stock airbox and airboot since we confirmed from previous testing that the factory airboot causes airflow problems with the scoop.
The engine likes the Q05 rod the best at around 72 clicks. The engine ran really strong with the 40mm. No big surprise! lol.
Real World confirmation testing:
The next morning before loading up to leave, we took my R out to the open empty parking lot to confirm the same performance that we experienced on the dyno. We were still running without the airbox and airboot as the air conditions were still mostly clean. The engine ran flawlessly from top to bottom. The power delivery was strong and smooth, just like the dyno testing. The smart carb was now performing just as expected.
Conclusions:
With the 2 separate issues going on with the carb, I don't think we would have ever resolved them without making the drive out to APT. Too many variables. Due to the step in the factory airboot, it WILL CAUSE PROBLEMS WITH THIS CARB. This has to be addressed if you want full rpm range out of your carb. This is not a carb problem, this is a intake boot problem. This problem was hard to diagnose as well because almost no other intake boots have this step in the boot, except for the Honda 450R (not sure about which years). The permanent remedy for this issue will be to purchase: one for Troy Robl's need intake boot and airbox designs, LED's airbox eliminator setup, any other airbox eliminator setup, or fuel customs inc intake boot and airfillter combos.
I will be posted the dyno run videos as soon as they are ready. Note that they are NOT all inclusive. You can't see the numbers on the dyno. All you can gain from the videos is hearing the sound of the engine. If you have any questions, feel free to ask away and I will answer as best I can.
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This is Run 1, without airbox
[video=youtube;PPtPhpA4K0c]https://www.youtube.com/watch?v=PPtPhpA4K0c[/video]
Run 2, without airbox
[video=youtube;a4sjUNfg-bU]https://www.youtube.com/watch?v=a4sjUNfg-bU[/video]
Run 3 without airbox,
[video=youtube;L69QoZU1T7A]https://www.youtube.com/watch?v=L69QoZU1T7A[/video]
Run 1 w/ airbox and airboot, take notice of 2nd long rev up pull. Listen to the sound at higher rpm versus without the airbox
[video=youtube;6NIThrd60Ao]https://www.youtube.com/watch?v=6NIThrd60Ao[/video]
Run 2 w/ airbox:
https://www.youtube.com/watch?v=fuA8BUQk-JU
Run 1 w 40mm billet: Notice a very different sound to the engine, but still very strong
[video=youtube;xjEvs9IZExU]https://www.youtube.com/watch?v=xjEvs9IZExU[/video]
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Run 2 w/ 40mm billet:
[video=youtube;Lcq4PUEQues]https://www.youtube.com/watch?v=Lcq4PUEQues[/video]
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Awesome bud. I need to get one of troys new intake setups and get back after this.
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What is this step in the factory air boot? Do you have any pics?
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What is this step in the factory air boot? Do you have any pics?
(http://forums.trx250r.org/vbulletin_imports/100_6003_2017-04-18_5098.jpg)(http://forums.trx250r.org/vbulletin_imports/100_6004_2017-04-18_3857.jpg)(http://forums.trx250r.org/vbulletin_imports/100_6005_2017-04-18_8559.jpg)(http://forums.trx250r.org/vbulletin_imports/100_6006_2017-04-18_6843.jpg)
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Here are some pics of the R & D facility that Corey let me take.
(http://forums.trx250r.org/vbulletin_imports/100_6007_2017-04-18_9852.jpg)(http://forums.trx250r.org/vbulletin_imports/100_6008_2017-04-18_9536.jpg)(http://forums.trx250r.org/vbulletin_imports/100_6009_2017-04-18_1533.jpg)(http://forums.trx250r.org/vbulletin_imports/100_6010_2017-04-18_4443.jpg)(http://forums.trx250r.org/vbulletin_imports/100_6011_2017-04-18_9566.jpg)
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(http://forums.trx250r.org/vbulletin_imports/100_6012_2017-04-18_2384.jpg)(http://forums.trx250r.org/vbulletin_imports/100_6013_2017-04-18_2009.jpg)(http://forums.trx250r.org/vbulletin_imports/100_6014_2017-04-18_8687.jpg)(http://forums.trx250r.org/vbulletin_imports/100_6015_2017-04-18_7656.jpg)(http://forums.trx250r.org/vbulletin_imports/100_6016_2017-04-18_9755.jpg)
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(http://forums.trx250r.org/vbulletin_imports/100_6017_2017-04-18_7535.jpg)(http://forums.trx250r.org/vbulletin_imports/100_6018_2017-04-18_8662.jpg)(http://forums.trx250r.org/vbulletin_imports/100_6019_2017-04-18_9707.jpg)(http://forums.trx250r.org/vbulletin_imports/100_6020_2017-04-18_1136.jpg)
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Good stuff. I actually caught the intake tube shrouding that vent before I tried to run mine. I suspected that's why other guys were having trouble especially on the bigger bores that are drawing more air. Guess I should have spoke up. I ground a little off that lip and I don't think it's affected me but that's obviously not the best solution. Should definetly get with Troy about this. I was wanting one of his setups just for that reason. Should be a better option.
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Good right up Ryan, that all makes perfect sense. I've actually got the prototype boxed up and was going to send that to you today or tomorrow, (if the wife gets home in time...:)...) I can print some more of those for others to try and test. Then I can solidify on a design, I have FWC all tee'd up to make some carbon fiber versions and of course I'm still developing a cheaper plastic option as well. I still think you're going to want to run the larger 450R filter with that 363cc motor.
If you were in KC you're only about 2 hrs away from me. Next time, if you go to APT again I could bring some intakes to help with your testing.
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Good right up Ryan, that all makes perfect sense. I've actually got the prototype boxed up and was going to send that to you today or tomorrow, (if the wife gets home in time...:)...) I can print some more of those for others to try and test. Then I can solidify on a design, I have FWC all tee'd up to make some carbon fiber versions and of course I'm still developing a cheaper plastic option as well. I still think you're going to want to run the larger 450R filter with that 363cc motor.
If you were in KC you're only about 2 hrs away from me. Next time, if you go to APT again I could bring some intakes to help with your testing.
I agree, I want the larger filter for this motor. So hurry up with the airbox! lol.
Go to APT again? I hope not! Not that it wasn't fun, but that's a long frickin way! Not really sure how I made it there and back on so little sleep. Some parts of the trip were a little fuzzy.
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Well the airbox, I can get made in a matter of a couple weeks/days. Tony could probably cut and form them even quicker than my local guy. Once I establish the intake is right I'd design the box to fit the intake and install on the frame. I have a completed cad model of an 88 frame and a laeger CR500 linked frame. I'll start redrawing that up tonight/tomorrow.
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Well the airbox, I can get made in a matter of a couple weeks/days. Tony could probably cut and form them even quicker than my local guy. Once I establish the intake is right I'd design the box to fit the intake and install on the frame. I have a completed cad model of an 88 frame and a laeger CR500 linked frame. I'll start redrawing that up tonight/tomorrow.
Cool deal! I will send you some feedback and pictures of the fitment of the intake boot when I get it in my hands.
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Awesome report!!
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Great job Ryan, did your engine prefer the 40 over the 38?
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Well the airbox, I can get made in a matter of a couple weeks/days. Tony could probably cut and form them even quicker than my local guy. Once I establish the intake is right I'd design the box to fit the intake and install on the frame.
I'm in for any fix we can get with this intake boot problem with the smart carb. The puma and saber intakes are much longer than pro-x and sphinx. My boot is caving in on itself.
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Led intake with a 40mm billet smart carb. (http://images.tapatalk-cdn.com/15/08/03/31af9ff8f9fc1334ab9d683194f69f7b.jpg)(http://images.tapatalk-cdn.com/15/08/03/1c120f35ca3331685f940328dd1dab89.jpg)(http://images.tapatalk-cdn.com/15/08/03/d1a8a74ff266c07cf3dbded713d14e41.jpg)
Sent from my iPhone using Tapatalk
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Wow sceans that looks like it would work great. I assume no airbox though right.
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The prototype ABS intake is going out this morning to you Ryan. I've been experimenting with a brand new material over the night and this morning. Called Taulman Nylon Bridge. It is extremely strong and flexible. I could see this as a potential candidate for printing intakes to use indefinitely. Plus they are easy to die different colors and relatively cheap to make. As soon as I get one printed completely, still experimenting with machine settings I'll be able to send one out for testing. Stoked about this new material, I just need to become and expert on this material like I am with the ABS stuff.
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Update 8/4/15:
I installed an airbox eliminator kit last night and ran it. With the lessened airflow than the bare carb, this rod is now too rich on the top end. Bottom end is still strong, but the rod is giving more fuel at top end than air to match it. I took the kit off back to the bare carb and the engine ran strong all the way through again. So while this rod is fine with perfect airflow, it is actually a little too rich when running the air filter. I was currently running an L072 rod, but I got a Q05 and Q07 rod coming.
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Great job Ryan, did your engine prefer the 40 over the 38?
That really depended on what you want to use the engine for. The 40 had some extra wide open power, but the 38 accelerated faster. For mx, I personally think the 38 would have the advantage. For duning or drag racing, the 40 would have the advantage.
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The prototype ABS intake is going out this morning to you Ryan. I've been experimenting with a brand new material over the night and this morning. Called Taulman Nylon Bridge. It is extremely strong and flexible. I could see this as a potential candidate for printing intakes to use indefinitely. Plus they are easy to die different colors and relatively cheap to make. As soon as I get one printed completely, still experimenting with machine settings I'll be able to send one out for testing. Stoked about this new material, I just need to become and expert on this material like I am with the ABS stuff.
This sounds like an interesting break through, Troy. Interested to see what you come up with!
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Wow sceans that looks like it would work great. I assume no airbox though right.
Yeah Kyle no air box, no reason you couldn't cab up some sided and bottom for it though. I'll have a buddy come up tonight and see if we can't shoot some video of mine running with the Q07 rod in Ryan.
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A great sc info run ryan. Glad you were able to get with them and figure some things out.
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The prototype ABS intake is going out this morning to you Ryan. I've been experimenting with a brand new material over the night and this morning. Called Taulman Nylon Bridge. It is extremely strong and flexible. I could see this as a potential candidate for printing intakes to use indefinitely. Plus they are easy to die different colors and relatively cheap to make. As soon as I get one printed completely, still experimenting with machine settings I'll be able to send one out for testing. Stoked about this new material, I just need to become and expert on this material like I am with the ABS stuff.
Troy another thing I noticed with the cast smartcarbs is the mounting flange on the intake boot side of the carb is fairly short. If there's any way you could get your boot or rubber section that you use to lock into the groove on the carb flange that would be a big improvement.
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Yes I can do that. I would have UPP make the adapter boots that go from the carb/smart carb to the intake. Problem is it takes forever (months) to get parts from them, so I'm prototyping using the 6ply silicone hose. I've had great luck with that on the 450r's. I'm considering doing the polyurethane rubber molding manufacture in house as well. There's just not enough hours in the day to do everything I want to do.
I did some experiment prints (small pcs) last night with Nylon material and that stuff is fantastic. Its extremely strong almost indestructible. So I've got another intake for my yamaha printing right now. Problem is its a 35-40hr print for just one unit. I'm going to do some field and structural testing of the material and see how it holds up compared to the carbon fiber.
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i should have gotten involved with you guys a long time ago haha. im having all kinds of trouble with a stock boot to a umr aluminum air box that i made a lid for. to top that off its on an arens frame! im on the edge of cutting and re welding parts of the air box. if i hang it low enough for the boot to fit right the caliper hits it and shoves it up pinching my snorkel and kinking the intake boot. oh well i guess ill hang back with @spiritshine and wait for you to finish lol. i can handle re making the air box to work for me its just the boot i really need. the stock one is too stiff and really necks down too far for my 38.
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Yes I can do that. I would have UPP make the adapter boots that go from the carb/smart carb to the intake. Problem is it takes forever (months) to get parts from them, so I'm prototyping using the 6ply silicone hose. I've had great luck with that on the 450r's. I'm considering doing the polyurethane rubber molding manufacture in house as well. There's just not enough hours in the day to do everything I want to do.
I did some experiment prints (small pcs) last night with Nylon material and that stuff is fantastic. Its extremely strong almost indestructible. So I've got another intake for my yamaha printing right now. Problem is its a 35-40hr print for just one unit. I'm going to do some field and structural testing of the material and see how it holds up compared to the carbon fiber.
Sounds awesome Troy. I definetly appreciate you going through with all the prototyping and testing and listening to what we want. I find all of your posts interesting. Can't wait to see what else you come up with.
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this is very good stuff. scary what a couple ambitious engineers can do with their hobbies.
John
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Update 11/24/15:
Just thought I would share some interested info with you guys. So I finally got some information about the dyno runs from my trip. I (and Corey) got buys and just never got around to gathering the data. I don't have the dyno charts yet, but will get them when Corey gets some extra time. Here's the info I do have at the moment. I found it interesting so I thought I would pass it along.
Here are the peak hp numbers:
363 engine w/ 38mm Smart Carb - 57rwhp
363 engnie w/ 40mm Smart Carb - 61.5rhwp
These numbers were both with no airbox/filter and an old dented fmf fatty pipe (had to install an oxygen sensor, wasn't drilling my good TRX 5B pipe).
What surprised me was not the peak hp, but the difference in hp output between the 2 carbs. I didn't expect it to be a 4.5 hp difference. Before some of you experts jump in , yes I realize that the difference between the 2 carbs would yield different results depending on the setup of the engine. Anyway, I thought you guys might find this cool as well.
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These numbers were with an old dented fmf fatty pipe
(https://media.giphy.com/media/iXXvFFsWb6DUk/giphy.gif)
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Update 11/24/15:
Just thought I would share some interested info with you guys. So I finally got some information about the dyno runs from my trip. I (and Corey) got buys and just never got around to gathering the data. I don't have the dyno charts yet, but will get them when Corey gets some extra time. Here's the info I do have at the moment. I found it interesting so I thought I would pass it along.
Here are the peak hp numbers:
363 engine w/ 38mm Smart Carb - 57rwhp
363 engnie w/ 40mm Smart Carb - 61.5rhwp
These numbers were both with no airbox/filter and an old dented fmf fatty pipe (had to install an oxygen sensor, wasn't drilling my good TRX 5B pipe).
What surprised me was not the peak hp, but the difference in hp output between the 2 carbs. I didn't expect it to be a 4.5 hp difference. Before some of you experts jump in , yes I realize that the difference between the 2 carbs would yield different results depending on the setup of the engine. Anyway, I thought you guys might find this cool as well.
My experience has been that these big bore cylinders need larger carbs than what Mikuni or Keihin offers in a compact design. We bore the 38 mm and 39 mm carbs to 41 to 42 mm and that is still not enough. The VM 44 Mikuni just not fit into the space confines very well because of its height. But the engines can use the increased air flow that comes from carbs in the 44 to 46mm range.