Large injectors for racing 2- stroke

[Joe Cheng]

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From: 	James Weiler[SMTP:james at brc.ubc.ca]
Sent: 	September 30, 1997 10:55 AM
To: 	Joe Cheng
Subject: 	Re: your mail



> Hi:
>=20
This an interesting question. For a typical high output 4-stroke the=20
injector is firing for longer than the intake stroke.  Eg. at 6000 RPM=20
the intake stroke is about 5 millisec.  But the injector fires for about =

12-14 msec. In a 2-stroke you have 1/2 the time for a complete cycle =
thus=20
you must deliver more fuel in less time so I would say yes double the=20
size of the injectors.  For 210 bHP you will need 76 lb fuel/hour so =
with=20
4 injectors that's 19 lb/hr.  These are stock injectors found in 5.0=20
Mustangs so you can get them from the wreckers cheap.  BUT then there is =

the doubling issue so you really need 8 of these (2 per cylinder) but =
you=20
only need 4 injector drivers.=20


Hi:

Thank you for your reply.

I only have 3 cylinders in my engine. The injector sizing chart (4 =
stroke) that I was using shows 210 hp need 1470 cc per minute. This =
works out to 88.2 litres per hour. Gasoline weights 0.67 gram per cc, =
this means 59 kg per hour (130 lbs per hour). Where did you get your =
numbers from. Are you sure they are correct because a 5.0 Mustang only =
puts out slightly over 200 hp with 8 cylinders. With your original =
assumption of 4 cylinders putting out the same amount of power, the =
Mustang injectors gotta be too small. If my numbers are correct and =
there are only 3 cylinders, then we are talking about 43 lbs per hour =
(490 cc per minute) for each injector before we double the number for a =
2- stroke engine. Currently, my engine with carburators is AVERAGING =
about 1 litre per minute. This includes driving from the pit to the grid =
area, running thru a 40 to 50 second course ( with full and part =
throttle) and then returning to the pit area. This might indicate that =
at full throttle, the engine could be burning 3 litres per minute (265 =
lbs per hour) !!!  Are there injectors out there that will flow 980 cc =
per minute (86 lbs per hour) ???=20

Joe



> 3)   Who is a good supplier for throttle bodies. I need single =
individual ones to replace motorcycle type carbs. Any advantage in =
having one common throttle opening shaft instead of three individual =
ones ?
You can make your own from the old carbs.  Just bore out the venturis =
and=20
voila!

hope some of this helps
later
jw