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Hi can anyone tell me if i should be running a completely standard carb to fuel a stage 1 hybrid that should be below 150bhp at -13psi
At the moment i have some grp a contraption that runs real rough and has afr's of 16+ on idle even with the screw wound right out. After weeks of trying to set it up i have now decided to bin it and get hold of a standard carb and change jets if necessary.
Any help with what size jets i should start with would be appreciated:D
You'll probably be fine with a totally standard carb for that boost pressure - I am. Just keep an eye on the AFR. :)
id still be checking first personally, i was fueling for 14psi , with a standard carb other than a 1.2 2nd stage and it was still running slightly lean at wot.
Saying the above im pretty new to it all, but heres my thread if you want a looksies.
http://www.rtoc.org/boards/showthread.php?t=17611
Thanks...Has anyone ever tried to put a group a carb back to standard? Is it possible to change the venturi and jets back or should i just buy a standard carb, also i noticed my afr's jump around when on idle somewhere between about 14.8 and 16.5 (lowest i can get it) is this normal?or could this be to do with the group a carb?
Thanks for help...Im learning :D
Sounds like a possible air leak to me. I had this on one of my old carbs, I smeared a little (& I mean a little) instant gasket between the carb gakets & inlet. don't put any on the bottom of the carb itself or that side of the gasket.
Grp A (or tuners attempts at a grp A) are :crap: anyway but usually just rich all the way through the revs, well right up till you need it if you're running over 21 psi & then they run lean :wasntme:
Sounds like a possible air leak to me. I had this on one of my old carbs, I smeared a little (& I mean a little) instant gasket between the carb gakets & inlet. don't put any on the bottom of the carb itself or that side of the gasket.
Grp A (or tuners attempts at a grp A) are :crap: anyway but usually just rich all the way through the revs, well right up till you need it if you're running over 21 psi & then they run lean :wasntme:
Thanks ill go try that now :D
spray wd40 or carb cleaner wile holding it at 2.5kish and spray it around carb or vac pipes if you here a engine tone change thats where your air leak is
spray wd40 or carb cleaner wile holding it at 2.5kish and spray it around carb or vac pipes if you here a engine tone change thats where your air leak is
Jeeez sounds dangerous :eek: thanks ill try that aswell:)
Do you run a dump valve ? Usually the 1st place to start, then vac hoses & then carb base. Could also get the carb top off to check if there is fuel dribbling from the acc pump jet, but hat usually richens it up.
should idle sit very stable with regards to the afr's , only wondering as mine was quite all over the place, also my r5 has always had quite a strnge idle, with the occasional miss every so often.
out of interest ive jst thought, im sure i remmber my idle screw seal was a but perished, i surpose that could be the cause.
:D Sweet
Must have had a leak at carb base it has sorted out my lumpy idle and allowed me to set my afr at idle its now only skipping from 13.9 to bout 14.3 is that close enough?
I also sprayed wd40 all around inlet and carb after seems no more leaks:)
Thanks for your help all it was doing me head in
This just leaves the jetting question the car is not yet on the road so i cant really check afr's at boost etc yet. Will the group A carb be massively overfuelling my 13psi boost as i have a spare carb with a 125 a/c and a 117.5 main? which i could drill to 120 and stick in would this help or should i leave well alone?
One thing i did notice now that it idles for the first time in months is that after idling for a bit if i dab the throttle it tries to cut out? It appears the brass tube is squirting a nice jet and if i rev a few times its ok untill idle again? Fix one problem to find another:D
If you have an AFR gauge I'd have a play with the standard carb, TBH you may find for 13 psi the standard set up will work, 120 main & 125 air corrector. If not try dropping a 1.1 mm air corrector in.
Other prob is either related to the jets in the carb or the accelerator pump needs setting up.
**EDIT** just looked & you run a cam so you may find you will need to drop a smaller a/c in or enlarge the main or 2nd stage if you feel ok with that, there should be something in the article section..
Forgot to say the standard carb is a scrapper just took jets from it to see size
Should i then do the same with the group a carb stick the 120 main and 125 a/c try it on the road and if ness try smaller a/c?
I am warming to the carb a bit now that it idles and as it has recently had a recent rebuild not gonna bin it just yet :)
It could well be the accelerator pump as i was messing with the spring and bolt bit when it wasnt running properly.I have read the 5mm drill thread a few times but i cant work it out :oWill have another go at it lol
Well with a larger venturi you need different jetting for it to work, you may be ok with a smaller main though... trail & error I'm afraid so find a bit of pipe to bridge the carb water hoses & go have a play ;)
Thanks for your help m8 got tickover now so ive somewhere to work from :)
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