4 replies to this topic

[mniguy_nz]

Hi there,

 

So I bought a needle for my HIF44 that was recommended to me but it has some significant flats spots in it.

 

What I'm wanting to do is weld in a flange for a wideband oxy sensor and make or buy a float level indicator then profile the needle to get the correct A/F Ratio.

 

My question is does this have to be done on a rolling road or could it be done stationary and then effectively repositioned using the mixture adjustment on the bottom of the carb to reposition the jet relative to the needle to get the correct A/F ratios on the road.

 

The only dyno's in the South Island of NZ wouldn't know what a CV carb is if you threw one at them so that option is out

[Dan]

  It needs to be tuned under load, and this often means re-profiling the needle.  Just moving the jet will simply move the entire fuelling range up or down a bit.  It may cure the couple of flat spots you have found but make everything else rich at the same time.

[Earwax]

Hi mniguy

 

I would put the AFR sensor on anyway , it is a good tuning tool.

 

My suggestion - use it to get the current state of play /feel picture of the current needle.  I just read the gauge as i go along but you can use computer chart.  You will get a feel within .5  (eg it (AFR)is closer to 14.5 than 14  Then adjust needle to get mid 12AFRs at wide open throttle.  come back and see what that looks like feels like at idle and just off idle..  You will get a sense of too rich, to slow to richen etc.  At this point check this against your timing .. i have found a lot of flat spots are at the transition just off idle  ( on mpne i tune for 30 -32degrees at what, which is about 22-23degrees at 2000rpm and 10 at idle 1000rpm  - i use RON98 fuel) You may need to adjust the timing slightly.

 

If still no good then sit down with your new found knowledge and a needle profile site like minty lamb and select a needle with a better profile

[lrostoke]

http://www.terryhunt.../picsb/pics.htm

 

 

worth a read

[mniguy_nz]

Awesome thanks for all the replies guys I'll get on to sorting the AFR and all the rest