Restrictor Placement in inline four with carbs

[SkidRow]

Hello to everyone,
We are using an inline four (Yamaha 250cc) and will be using the standard carbs for this year.My question in if the restrictor must be placed between the carbs and the engine,as such would make for a pretty akward intake design.Does any one have any photos of a carburated in line four prepared for the competition even if it is an 600.Thanks.

[Jersey Tom]

I dont think I've ever seen a carburated fsae car. You'd have to go back to pictures from like '92.

[SkidRow]

I have read in the forums that UVIC has used a carburated engine in 2002 and I know firsthand that there was a carburated CBR600 in Formula Student 2002.Anyways,shall anyone have any photos/suggestions,please get in contact.Thanks

[PatClarke]

Hi,
Carburetted cars turn up regularly in FSAE and FStudent. There were several in the UK earlier this month. The only solution I have seen on inline 4 engines is to use a single carb feeding through the restrictor into the inlet manifold.
I can't imagine any other way to do it.
Regards
Pat

[Kirk Feldkamp]

Look for pictures of the Cal Poly San Luis Obispo car at FSAE West 2006. They were running a 450 single with the stock carb (they said they ran out of time/couldn't get the FI working in time).

-Kirk

[drivetrainUW-Platt]

UMR ran a carb F2 a while back, maybe in 2002, it was the one they sold on ebay

[Alexandre D.]

CVM ran with a carb on a 450 single from honda at Detroit.
Considering the price/complexity of a decent injection system, carb seems a good idea for a starting team. A complete carb system cost less than 1 of our injectors.

I'm not a carb guy... I guess that a small single carb just before de restrictor could do a decent job.

[RacingManiac]

Tokyo Denki if I remember correctly has a carb on their first car as well(2003 I think)....it was a 450 or 500 single...

[Nitesh]

carburetted cars do turn up at the comp reqularly but not with the inline four carbs as you intend to do. Either one of the carbs from the whole setup or another carb which suits your requirements. you could look for carbs from some single cylinder bikes.

[Jeff The Pyro]

As others said, running four carbs with the restrictor would be nearly impossible (it would require all 4 barrels to converge on one restrictor, and then split off again to the 4 intake ports. If I were to go about carburating a fsae 4 cyl, i would get a set of carbs from a bigger 4 cyl bike on ebay, (600 or 750), and then only use one of the four carbs. I personally would advise against carburation however... all the fuel has to flow through the restrictor, which just means there's less room for air to flow through it. Also there are other benefits of FI in terms of fuel economy and performance (getting a 4 min penalty in the endurance is an unpleasant way of realizing that fuel economy is actually important in this comp)

good luck

[murpia]

There used to be a 'rookie rule' at Formula Student which allowed first year teams to run the stock bike carbs. Unfortunately the IMechE has removed those older rules pages from their website so I can't quote it precisely.

I _think_ the arrangement was that you had a 20mm restrictor as normal, then a plenum feeding the bike carbs. Maybe someone has a copy of the old rules?

I don't really know much about moto carbs, but I suppose if you removed the butterflies or slides from the moto carbs, and fed the air through the 20mm restrictor and a single throttle body as typical FI setup, then the carbs would fuel properly at WOT at least. Don't know for sure if they would fuel correctly at reduced manifold pressure if the throttling is done upstream of the carb itself.

Regards, Ian

[KU_Racing]

murpia hits on the main problem... according to the rules, you can dump fuel in anywhere, but all throttle control must be through a single throttle body upstream of the restrictor. good luck plumbing that.....

[Homemade WRX]

Originally posted by KU_Racing:
murpia hits on the main problem... according to the rules, you can dump fuel in anywhere, but all throttle control must be through a single throttle body upstream of the restrictor. good luck plumbing that.....
plumbing it won't be so bad...it will suck (no pum intended) that they will be pulling fuel through their restictor too...less air in the system = less power

[SR-Mike]

After numerous crank sensor related FI problems at Formula Student 2005 we finally resorted to a similar set up to what ian has suggested as a last attempt at getting the car running for the endurance.

We removed the butterflies from the stock carb set up and managed to fit this unit between the engine and our original FI manifold overnight. While also rewiring the car to use the stock ECU for spark timing using our FI throttle pot. There was a few issues related to sealing up some of the breather holes found all over the carb unit but they were easily plugged.

Amazingly it worked, but not very well. It was however enough to get us running for the endurance where unfortunately some loose bodywork eventually resulted in a DNF. From the smell of the exhaust I'm fairly sure we would have run out of fuel anyway.

So i wouldnt recommend it.

Mike

University of Strathclyde Motorsport, 02-06

[TG]

Originally posted by Jersey Tom:
I dont think I've ever seen a carburated fsae car. You'd have to go back to pictures from like '92.

The engines were unrestricted in '92... a lot of the teams back then used the stock intake manifold, too.