Carburetors and Design

[Chris Aho]

Just your thoughts...

Would one get massacred in design if they were to employ the use of a carb? If you can back it up with being simple, etc. and having a good reason for not going with FI?

I know they are crude and inefficient when compared to FI, but they also have their advantages.

[Chris Aho]

Just your thoughts...

Would one get massacred in design if they were to employ the use of a carb? If you can back it up with being simple, etc. and having a good reason for not going with FI?

I know they are crude and inefficient when compared to FI, but they also have their advantages.

[Brett Neale]

As with all design judging questions, most of it depends on how you justify your decision. There's plenty of good reasons to choose a carb over an EFI setup:

- Cost
- Less reliance on complex/expensive ECMs
- Potentially more reliable (god knows I hate non-factory SYNC sensor headaches... argh!)
- Simple
- Probably easy to tune
- Throttle setup and idle bypasses already designed, easily adjusted

Of course the downsides are that your fuel usage may increase, and the fact that your restrictor would suck fuel AND air which decreases the power limit from the 20mm hole. But hey, if you save $2k on fuel system and ECM then spend that on shocks and tyres, get the car out on track earlier due to less electrical/fuel gremlins and tune the thing to hell, then I'm sure judges will be very supportive of your decision.

[Diablo_niterider]

i like the sound of that
plus u save a lot of weigth on fuel rail + injectors + injector seats on ur airbox + its mountings etc etc...


- Cost
- Less reliance on complex/expensive ECMs
- Potentially more reliable (god knows I hate non-factory SYNC sensor headaches... argh!)
- Simple
- Probably easy to tune
- Throttle setup and idle bypasses already designed, easily adjusted(as our friend mentioned above)

+ weigth V/S diff in lap times

seriously would love to see someone try it out
run with efi once and then with the Carb



Hiren Patel
Tech Head - Powertrain
www.orion-racing.com (http://www.orion-racing.com)
K.J.Somaiya coll .of Engg. ,Bombay
+91-9820399224

[exFSAE]

I recall a senior judge talking to us last year, giving us some feedback after our design event. While he was a fan of simple, reliable powertrain setups.. his impression was the powertrain judges wanted to see lots of technical development. Fancy electronics and control systems, forced induction, etc.

Don't be designing your car around the design event though. Design it around driving. If you're going to gain something by running a carb setup, then do it. Maybe if you're a new-ish team or super strapped for cash and development or tuning time.

But even then.. you can run something like the F4i with the stock ECU and maybe a Power Commander strapped on it. Its simple, it works, and it gives you SOME tuning option plus the hardware is there (engine, injectors, etc) for future engine management if you want it.

[Superfast Matt McCoy]

I don't remember seeing an abundance of fancy engine electronics, control systems, or turbochargers in design finals. It always comes down to: does it make the car better and can you prove it? I think you would have a really really hard time convincing the design judges that a carburetor is the better option. Maybe it's just me and my belief that carburetors are the fuel systems of Satan. Of the benefits listed above, I would give you Cost, but I absolutely don't think it is worth the trade-off.

Carbs are such old technology. Can you imagine if there was a major racing series that still used carburetors? They might as well just use pushrod engines and a solid rear axle. That would just be loony...

[vreihen]

Superfast Matt McCoy said:
<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Can you imagine if there was a major racing series that still used carburetors? They might as well just use pushrod engines and a solid rear axle. That would just be loony... </div></BLOCKQUOTE>

No, that would be called NASCAR!!!!! http://fsae.com/groupee_common/emoticons/icon_biggrin.gif

[James Waltman]

Cal Poly SLO at FSAE West in 2006:
http://dot.etec.wwu.edu/fsae/HostedPics/2006_FSAE_West/Thursday_v1/images/DSC01692.jpg

It fit pretty well with the theme of the back half of that car.

[exFSAE]

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">I don't remember seeing an abundance of fancy engine electronics, control systems, or turbochargers in design finals. It always comes down to: does it make the car better and can you prove it? </div></BLOCKQUOTE>

I'm just tellin ya what the judge said. I would imagine the cars in design finals had well tuned and setup engine packages.

In any event, like I said, don't focus on the design event. Focus on building a car that's fast, reliable, drivable, and can be built quickly enough to test.

If that means going carb'd to get a car done quick and on budget? Awesome. Do it. To hell with what the judges say, you got a car that holds together you will finish top 40 or 30.

EFI gives you more tuning options, more to learn, and if you do standalone or home built it gives you car control options down the road.

I just think its easier these days to do EFI. There's heaps of F4i and RR motors around. Not sure how long ago they discontinued the F4. Stock ECU, Power Commander, and you'll be set.

Bottom line. If you design a car with trick stuff, just to be trick (titanium flexures, active suspension, carbon everything, monocoques, etc).. it won't do you any good. It's really not that complicated to do some legit engineering and make a fast, reliable car. And if you understand how and why.. you'll not only perform well on the track but will be able to do well in judging. That's my feeling at least.

[Go Hawks]

Not quite the entire back half of that car James. Notice the carbon wheels and brakes http://fsae.com/groupee_common/emoticons/icon_smile.gif We ended up in the design semifinals with the carb too.

[D Collins Jr]

I don't know where you've been looking for motors, but good luck finding an f4i. If you're lucky enough to find one, it's probably broken, or will soon be broken, or has, i don't know, been filled with sand. The RR has packaging and powerband issues, and the f4 w/carbs was discontinued in 2001, I believe. Good luck finding one of those either. Run EFI.

[exFSAE]

F4i's are still really easy to find...

[Biggy72]

Throughout the year I've been picking up f4i parts on ebay. The block we're using I won for $25, I got a spare head for $20, cams for $9.... and if I wanted to get an entire block they're really easy to come by.

If you're concerned about cost learn how to put together a megasquirt unit, if you want it to be more simple get a performance electronics. Either way it's not that complicated and it is way more adjustable than a carb is.

[DPrice]

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content"> Not quite the entire back half of that car James. Notice the carbon wheels and brakes Smile We ended up in the design semifinals with the carb too. </div></BLOCKQUOTE>

I like all the parts back there slowly rusting away.



At least that car didn't have wrinkles in it.

http://fsae.com/groupee_common/emoticons/icon_biggrin.gif
-David

[Kyle Roggenkamp]

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Superfast Matt McCoy:
I don't remember seeing an abundance of fancy engine electronics, control systems, or turbochargers in design finals. It always comes down to: does it make the car better and can you prove it? I think you would have a really really hard time convincing the design judges that a carburetor is the better option. Maybe it's just me and my belief that carburetors are the fuel systems of Satan. Of the benefits listed above, I would give you Cost, but I absolutely don't think it is worth the trade-off.

Carbs are such old technology. Can you imagine if there was a major racing series that still used carburetors? They might as well just use pushrod engines and a solid rear axle. That would just be loony... </div></BLOCKQUOTE>

Just because it's old technology, doesn't mean it's not worth running. Take the wheel, for example...

[Superfast Matt McCoy]

<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by Kyle Roggenkamp:
Just because it's old technology, doesn't mean it's not worth running. Take the wheel, for example... </div></BLOCKQUOTE>

Wow I... I think you completely missed the point.

[fade]

yes the wheel has seen little improvement since its inception. http://fsae.com/groupee_common/emoticons/icon_smile.gif
http://www.unicyclist.org/pics/bc.jpg

[Drew Price]

Regardless of re-inventing the wheel:

Yes, Cal Poly made Semi's with the carb setup with that car. It also made something like 18hp on the dyno (David, back me up, I couldn't remember the number exactly, but it was low). I have been told that the fuel injection for that engine, a Yamaha 450 single, was not ready in time for comp, so the carb got thrown back on.

That car also weighed 308 pounds (140 kilos), and took first or second in Auto-X event, and did very well in Accel, because the other systems of the car were particularly well developed, designed, and fabricated.

The car had a carbon front tub with 4130 rear subframe, and 2024-T6 aluminum rear axle, carbon wheels, and carbon-carbon dog drive brakes made from Tilton clutch discs. So yes, it made semi's irregardless that it had a carb, but it was clearly for reasons which we can all agree on. The guys clearly knew their car. That's the takeaway.

Chris, you might not get crucified for running a carb, but you had better do a good job explaining why it's there. Cal Poly did a good job covering up that their EFI was just not ready, and justified it.

Having the intake air having to share the restrictor with the fuel flow volume is a pretty serious issue too, the thing is already restricted, so we have to try to give it as much of a chance as we can.

BTW Cal Poly has been tuning their WR-450 running on EFI for this year. Watch out at West.

Best,
Drew

[Go Hawks]

I'm just gonna clarify some things. We (Cal Poly) didnt do well at all in accel, got about 10th in auto-x but did do well in the skidpad.

[DPrice]

And it was 23 HP, and 319 pounds

[Drew Price]

Thanks both, I am gonna shut up.

My Powerpoint from your guy's presentation at the NHRA gig says 3rd skidpad, 4th design, 11th endurance, 16th Auto-X, 12th overall with that car.

Should have checked my facts first.

Best,
Drew

[zfettig]

Hi,

I was on the WPI FSAE team when I went there waayy back, and am currently on the UMass - Lowell team.

We ran a carburatored engine at FSAE VIR this past week. It was the single biggest factor against us in the design competition. It saved us cost and complexity, which was good since it is UMass, so no money, and we only had 10 weeks to fab the car.

We went out in the Enduro, but the carbs worked great. We had a slight ergonomic issue, causing the car to stall, and the carbs flooded on restart. We were still runnable, but the car got flagged off the track.

Funnily enough, when I was at WPI, I had wanted to pull the Haltech off the '96 car (the oldest and heaviest still there) and throw on carbs so we'd always have an easily tuned car ready for auto-x. The Haltech on the '96 was different than the other three cars there at the time, and was glitchy. That idea got shot down. I'm still not sure why though.


<BLOCKQUOTE class="ip-ubbcode-quote"><div class="ip-ubbcode-quote-title">quote:</div><div class="ip-ubbcode-quote-content">Originally posted by caho:
Just your thoughts...

Would one get massacred in design if they were to employ the use of a carb? If you can back it up with being simple, etc. and having a good reason for not going with FI?

I know they are crude and inefficient when compared to FI, but they also have their advantages. </div></BLOCKQUOTE>

[Wesley]

Just think of the awesome venturi action you'd get if you put your metering ports IN the restrictor.