Forum: HoseHeads Sprint Car General Forum (go)
Moderators: dirtonly  /  dmantx  /  hosehead

OK, someone help a newcomer with some tech questions about the extra injectors on the exhaust side of cylinder head: Do these spray pure fuel (no air?) If so, doesn't that mess up the air/fuel ratio in the combustion chamber? If so, do they compensate by running the "regular" injectors extra lean.... or what?

Are the "side" injectors electronically timed or constant flow?

And finally, why do they have them.... couldn't they just make the main injectors bigger or run bigger jets?

Thanks

those are called "down knozzels" the fuel is directed to the the Intake port, just above intake valve , the " regular " maybe know as "up unozzels" are common on ASCS type 360's or limited sprint engines , the combination of the two has hit a top engine builders prefferance , the "takeoff " with the up knozzels has aided some teams to my understanding , Air Fuel calibration is done with computors located in most traiers ect , obtaining the desired ADR with the crewchief /tuner and changeing jets (pills) and bypass pressures will be constantly changed with a competitive team , a few differant variations of tuning are avalible the EGT (exhaust gas temprature)is commonly the tell truth sighn of correct or "optimal" tuning, alot of this would be more in depth on a engine dyno, specific RPM to EGT temps would be present and the bypasses & jets (pills) are tuned to spec RPM "top end" ect, this just constructs, a baseline, for "safe operation" of the engine, too much fuel is not good for the bottom end (bearings) of a methanol engine , not enuff fuel can destroy the top end (pistons vaves ect) by presenting the combustion chamber with too much temprature , BUT!! BUTT!!, HP guain is present with the edge of disaster ..(too,, " lean is mean" ) locking a engine down on correct jetting is a bit more difficult with the added knozzels, thats why the "top" teams are using them and understanding the air from night to night, hour to hour one side of America to the other hope this helps undestand a few questions to the common "walk by " type fan . no stupid question , its all just good stuff , who doesnt like HP!!

sorry, left a few things out ,the up knozzel helps in atomization of fuel, thus "takeoff" is helpfull, some drivers will tell you they dont see a differance?? , again , cam, timing, ADR, ect , will all play roll in this, the injection is all mechanical (for the most part) Schatz teamed up with his engine builder (Shaver)this past season on a EFI type engine , as a trial type engine , THE majority, 99% of what you are looking at is mechanical injection , a constant flow, injection ("and we liked it" !! god bless the grumpy old man on SNL..Ironically bigger jets make a knozzel run leaner at the same pressure , thus jetting is inversly puportional to the fuel mixture commonly , size of knozzels ,fuel pump,bypasses ,cam timing, ign timing, CID of engine, ect.. all has to be taken into consideration to manage the fuel correctly, it all makes a differance on running 5th or 15th.. most teams will have a manageable figure on thier engine being used depending on what race they are running for , how much $$ is on the line, fueling curves will be tsted to the limit... Nationals seen , what? three of the top teams damage engines in the 50th "A" main, the 9 ,11, and the 15(late) all expired , possibly due to running the most out of thier mills.. makes it exciting..IMO

Thanks Dirtdevil. That helps some; I guess I'd have to watch a guy tune it to completely get it.

This stuff is highly technical, fo sho!

the tuning your looking for will be done typically throughout the night, mainly just before the car rolls out of the pit area or (trailer area) before qualifying,heat , and main event , some jet selections are also done by a rotory dial ( I believe SK ) has this ? , many of the methanol lines you see come into a cartrige type (canister area) alot of the pill changes and pressure changes will be made at those locations, again , routinely throughout the night , youd probly have to be a bug on the crews shoulders to catch what is going on .. Find a team that is open to diehard fans they will help you understand it on thier car, most cars are typically similar just locations,brands ,styles, amount of bypasses , and dimensions of fuel components will differ..