"mike gray" <omgray@worldnet.att.net> wrote in message news:n_3ee.178770$cg1.90878@bgtnsc04-news.ops.worldnet.att.net...> What is the proper fuel flow rate for a 1st gen, measured at the carb?
Assuming a standard 12A?
Can't lay my hand on the manual at the moment but you should be seeing around 4.5psi head pressure and the flow rate will be significant. Probably something around 30+ GPH range.
Quick way to tell if it's enough......WOT throttle from standing start, to redline, through all gears. If it starts to stutter at high RPM in third gear it's not flowing enough. Of course, trying to find a deserted bit of road to do this on is a challenge (drag strip is best).
I've run a 40GPH pump on a stock carb (after someone stole the Weber) and as long as the return line is still in place it will be more than sufficient.....
The Raven wrote:> "mike gray" <omgray@worldnet.att.net> wrote in message > news:n_3ee.178770$cg1.90878@bgtnsc04-news.ops.worldnet.att.net...>
What is the proper fuel flow rate for a 1st gen, measured at the carb?>
Assuming a standard 12A?>
Can't lay my hand on the manual at the moment but you should be seeing > around 4.5psi head pressure and the flow rate will be significant. Probably > something around 30+ GPH range.>
Quick way to tell if it's enough......WOT throttle from standing start, to > redline, through all gears. If it starts to stutter at high RPM in third > gear it's not flowing enough. Of course, trying to find a deserted bit of > road to do this on is a challenge (drag strip is best).>
I've run a 40GPH pump on a stock carb (after someone stole the Weber) and as > long as the return line is still in place it will be more than > sufficient.....
Thanks.
It's an IT-7 car that I've been crewing/coaching. I raced production class boingers and don't know much about stock rotaries. We've gone through a lot of carb problems, think we might have them licked. We're flowing about 32 gph, which seems a bit low to me. The pressure is steady, but ya need volume, too.
The car only gets out a couple times a year, and I think the residual fuel is fouling the jets. We'll find out in June at Sebring. Don't know how to stop the starving in high speed turns and still stay legal, but everyone in the class has the same problem.
"mike gray" <omgray@worldnet.att.net> wrote in message news:f8pee.182083$cg1.2670@bgtnsc04-news.ops.worldnet.att.net...> The Raven wrote:>> "mike gray" <omgray@worldnet.att.net> wrote in message >> news:n_3ee.178770$cg1.90878@bgtnsc04-news.ops.worldnet.att.net...>>
What is the proper fuel flow rate for a 1st gen, measured at the carb?>>
Assuming a standard 12A?>>
Can't lay my hand on the manual at the moment but you should be seeing >> around 4.5psi head pressure and the flow rate will be significant. >> Probably something around 30+ GPH range.>>
Quick way to tell if it's enough......WOT throttle from standing start, >> to redline, through all gears. If it starts to stutter at high RPM in >> third gear it's not flowing enough. Of course, trying to find a deserted >> bit of road to do this on is a challenge (drag strip is best).>>
I've run a 40GPH pump on a stock carb (after someone stole the Weber) and >> as long as the return line is still in place it will be more than >> sufficient.....>
Thanks.>
It's an IT-7 car that I've been crewing/coaching. I raced production class > boingers and don't know much about stock rotaries.
Sorry, but I'm not familiar with the class seeing as I'm probably in a different country to you.
We've gone through a lot of carb problems, think we might have them > licked. We're flowing about 32 gph, which seems a bit low to me. The > pressure is steady, but ya need volume, too.
40GPH will feed a 48IDA Weber with 42mm chokes on a ported 13B at an extended 135MPH.
If pumps are open, there is a nice one from Carter. Mines at least a decade old so things have probably improved further since then.
The car only gets out a couple times a year, and I think the residual fuel > is fouling the jets.
It can, as will any junk that build up around that little nylon checkvalve under the accelerator pump (depending on model of carb)
We'll find out in June at Sebring. Don't know how to stop the starving in > high speed turns and still stay legal, but everyone in the class has the > same problem.
Sounds like a float bowl issue. Is the float cutting off the flow or is the fuel moving away from the jets?
Hmmm, extreme engineering. could you boost the fuel pressure in high speed turns to either blow past the needle and/or overfill the bowls? Hard to starve if the bowls are full....
Sorry, but I'm not familiar with the class seeing as I'm probably in a > different country to you.>
We've gone through a lot of carb problems, think we might have them >>licked. We're flowing about 32 gph, which seems a bit low to me. The >>pressure is steady, but ya need volume, too.>
40GPH will feed a 48IDA Weber with 42mm chokes on a ported 13B at an > extended 135MPH.>
If pumps are open, there is a nice one from Carter. Mines at least a decade > old so things have probably improved further since then.>
The car only gets out a couple times a year, and I think the residual fuel >>is fouling the jets.>
It can, as will any junk that build up around that little nylon checkvalve > under the accelerator pump (depending on model of carb)>
We'll find out in June at Sebring. Don't know how to stop the starving in >>high speed turns and still stay legal, but everyone in the class has the >>same problem.>
Sounds like a float bowl issue. Is the float cutting off the flow or is the > fuel moving away from the jets?>
Hmmm, extreme engineering. could you boost the fuel pressure in high speed > turns to either blow past the needle and/or overfill the bowls? Hard to > starve if the bowls are full....>
What sort of carb mods are permitted?
IT-7 is a popular budget class in SCCA regional racing. Basically, it's street legal stock: roll cage of course, springs and shocks at stock locations, shaved street legal tires, no porting, stock carb but we are using Grose jets. Pumps are free as long as in the original location, and pressure regulators and gauges are allowed but not in the cockpit.
It's a good class for racers on a tight budget and "rules creep" has not been a problem.
Everyone has carb problems and brake rotor problems. A spare carb or two and a crate of rotors, pre-cured on the oven's cleaning cycle, is mandatory equipment.
My guy only does three or four races a year and does not do the pre-race prep that I am used to. Nevertheless, we do run mid-pack and he's happy and having fun even if I'm not.
Anyway, I think I have him convinced that he has to meticulously clean the fuel system and carb before every race, and I'm trying to talk him into doing a test day so we can play with the float bowl. It's impossible to tinker on a race weekend, there just aren't enough track sessions and they're all too short.
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