52 replies to this topic

[mailman]

Just a brief update to this, I have been running in the engine on the BDL and it's been pretty good.

 

The new engine is a world apart from the old and I haven't even had it past about 4500rpm.

 

For those looking at a similar spec, I've found that the BDL is slightly lean at cruise and slightly rich at what so I'll be getting a BAL to try as soon as my local SU/Mini shop owner gets back from his holiday. I'm a little worried about the richness at Idle of the BAL but I believe that it's profile looks the closest to what I'm aiming for.

 

If the BAL isn't quite right I'll try BAZ. I can try profile a needle after that but experts who profile needles are light on the ground here, and it looks like I'll be able to get what I need from an SU profile anyway.

 

Will hope to get it Dyno'd in a few months.

[mailman]

I'm having a bit of an odd-ish (to me) fuelling issue.

 

I have changed to a BBB needle, which is now providing quite a nice ratio in the mid range and at cruise, and at what it is also pretty good... that is, until about 4500-5000rpm, at this point it starts to lean out quite a bit. The weird thing about it is that it leans out up there regardless of whether I'm using what or 3/4 throttle.

 

Can anyone provide any insight into the possible cause of this? And a possible solution? I am looking at either a BAZ or BAL needle, but they both then lean out that mid range again. I could possibly get another BBB needle and alter the final stages to provide more fuel. I'm just a little confused that it's a engine revs thing not a throttle position thing.

 

I've also changed to NGK BP6ES's, and they are definitely less sooty than my 7's, they are still a little black after. I get the feeling that my idle mixture needs leaned out a touch, but that's hard to get right in conjunction with the rest of the range.

[mailman]

Really annoying that it automatically "corrects" what (wide open throttle) to what.

 

I thought I was going mad!

[jaydee]

Yeah the swear filter is annoying when it comes to 'wide open throttle'

Have you been measuring the lean condition with an AFR gauge?

[mailman]

Yea, using a metre that sticks a sensor up the exhaust pipe and provides a digital AFR reading

[jaydee]

Try BBW instead

The needles youre using are rich at  high speed cruising but lean at the transition to full throttle and lean at full throttle

[mailman]

If I go for BBW, or take some material off of the appropriate stages of my BBB, will that mean I may be tooo rich at full throttle below about 4000rpm?

[mailman]

One other consideration is the air filter choice and use of a stub stack. I'm using a Minisport cone filter and also have a cheap stub stack on there at the moment. Could either of these cause the leaning out at high engine revs?

[DILLIGAF]

Yea, using a metre that sticks a sensor up the exhaust pipe and provides a digital AFR reading

 

Are you driving around using this ? Unless you are it's useless for anything besides idle mixture..........

 

The only way you can set a carb up properly is to put the engine under load.........

[mailman]

Yea, doing all of it under load.. Mostly on uphill grades too.

[jaydee]

One other consideration is the air filter choice and use of a stub stack. I'm using a Minisport cone filter and also have a cheap stub stack on there at the moment. Could either of these cause the leaning out at high engine revs?

 

Yes it is

You can even try filing down BBB accordingily if you feel that cruising-pick up is fine

 

[mailman]

yea, pick up is quite good. It may be slightly rich at below 2000rpm as the afr isn't measured accurately there.

if I were to try altering the profile of the BBB needle, which stages would you recommend changing? I am under the impression that 12-13 are actually Wide Open Throttle, not 15-16 as the stages might suggest?? Does that mean I should profile from 12 down, or only in the region of 12-13? Or as would appear the simplest, begin at 16, then work up, seeing if it changes?

[jaydee]

No you work from 3 then go down, always from top, otherwise you'll screw up all the other stations you've worked

As a reference, wide open throttle is station 9 up to 12, 6-7-8 are the transition from pick up to W_O_T

Stations from 13 just continue the taper, but wont take any metering

[mailman]

Ok, so I had a go at altering the BBB needle today. I didn't get it right and it ended up too rich in the mid range and at pick up without any huge improvement at high revs. I also tried a BBZ needle which seemed like it had a lot of potential but also provided too much fuel.

I had kind of been hoping that I could use BBZ and just raise the jet to bring the thicknesses in the upper stages between BDL and BBB. No real luck though.

One thing that was again suggested to me (among the idea of just going to EFI $$$) was that the HIF44 may be too big and that the 1000cc motor may not be able to suck enough air to get it to perform properly at those higher rev numbers. I find this a little bit hard to understand, has anyone had this experience, or success with using the HIF44 on a 1000? I am very tempted to order a HIF38 if it is likely to be a much better (and not reduce power) fit to my build. I just don't want to go melting things.

[jaydee]

I used the HIF44 with a ram pipe and sock filter, 276 cam, needle was a BDL modified to a richer pick up (matching the short ram pipe) and slightly richer top end.

Gave great motorway mpg, good acceleration and power, less bottom end issues than with an HS4, which was poorer overall.(The HIF38 works better than an HS4 though.)

Running twin HS2 at the moment, but apart from a better bottom end and throttle response, the HIF was faster overall. Need to do some extra work to improve them.