Motorsports Village

If this is an open header exhaust, tell me where your sensor bung is welded in!!!

Also, don't place too much faith in idle AFRs!! I'd concentrate on getting the idle right WITHOUT the wideband first.

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Big Boyz Toyz!



Necessity is the plea for every infringement of human freedom. It is the argument of tyrants; it is the creed of slaves.

William Pitt, British Prime-Minister (1759-1806)

Ken, yes it's open header. With the idle AFR I wanted to make a change and see the results on the (Racepak)screen. I started @ .065 in the IAB and went down to .058 and saw the AFR come down. I was happy.
I then went back to .062 and stayed there. It idles great, doesn't change in nuetral or in gear.
The mixture screws are at 3/4 turn. Throttle response is good, I even went down in pump shooters.
I can't wait for some good weather so I can go and test.
I can move the o2 sensor to one of the middle pipes, but that will be later on after I get a base line.
I still have my mates dyno day coming up in a couple of weeks to try the carb on, I will keep you all informed. Cheers Colin.

If you at 3/4 of a turn I would consider going up to a .070 IAB and readjust screws.
It sounds like it could be a little rich at tip in.

Correct me if I am not thinking but I remember Tuner telling me that he really didn't care how much the mixture screws were turned out just as long as they were turned out some..
Why are we set on the 1 1/2 turn if it does not matter to tuner?
Also if the IAB is at .070 then the IJ should go down some to get the the IAB in the .055/.060 range.

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running E85
Best ET 8.07
Best MPH 170.71
Barry

You are correct, the position of the idle screw is not real important. If you look close at some of the idle screws out there the taper of the point can vary a bit, this will make a small change in the number of turns out. However the number of turns can be a guide to the amount of fuel available to the transition circuit, the idle jet and idle bleed are responsible for providing transition fuel and this is what is most important when tuning the jet and bleed. At 3/4 turn he may have a little too much transition fuel, it just takes some experimenting at low throttle openings (1500-2000 RPM) to see what it wants. If it needs that much the mixture screw number is irrelevant other than to restrict idle fuel to the needed amount.

Thanks Mark that's exactly what I was trying to say.

I think I will leave it where it is for the moment, It idled best their with no off idle hesatation.
I had a problem before getting the engine to come up on the transbrake because it was lean, so I don't want to go their again.
When I get to the track and put some fresh plugs in (they are black from the 3 circuit) I will try a bit bigger IAB and readjust. But it sound good where it is now.
Cheers Colin

Oh, and guys, thanks for all the help. I will keep you updated.
Cheers Colin.

Well my mate had his dyno day. It's a 500 ci BB Mopar and I think the power it made, he was happy.
As you can see it made the most power with my carb, not his Pro Systems, although the PS is a 1050 and mine is a 1150. The dyno operator was saying "Pro Systems are the best, every thing else is junk"
so he was a bit surprised with my "junk" carb. He also was not able to get the A/F to print out on the dyno sheet. Mine was closer than the PS. I did have to jet up to #96's
Have a look at the sheets and tell me what you think. It looks like mine made more power using less fuel.
What do you guys think about the BSFC numbers? I thought mine droped a little low. The Pro Syetems was a little high.
Cheers Colin.

Looks good to me and your junk 2 circuit is working better than the POS systems carb ..

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running E85
Best ET 8.07
Best MPH 170.71
Barry

X2

_________________
Big Boyz Toyz!



Necessity is the plea for every infringement of human freedom. It is the argument of tyrants; it is the creed of slaves.

William Pitt, British Prime-Minister (1759-1806)

Ok so I'm going to be the spoiler here and ask, how much tuning was done on that PS carb? What I mean is was this the BEST that your dyno operator could get out of it?

Not that I'm a PS fan BTW, just want to make sure we're comparing apples to apples is all!

_________________
Big Boyz Toyz!



Necessity is the plea for every infringement of human freedom. It is the argument of tyrants; it is the creed of slaves.

William Pitt, British Prime-Minister (1759-1806)

The important part is that the average HP and TQ were up. This is what gets you down the track.

Like Ken I want to know did you guys tune on the PS carby? I didn't look at the BSFC before I started posting so I'll be checking back.

You'll be happier with your carb I'm sure.

Okay, I see the BSFC is lower with your carb by a significant amount. So on the dyno at least, you're making more power on less fuel. If your dyno operator has saved your pulls, take a look at the graphs for A & B fuel flow to see how equal they are. This visual is sometimes better to see that a column of numbers.

This guy is a good mate of mine, I went with him on dyno day to help him. He even organised it to coincide with my RDO. I even built him some new headers for this engine.
I took my carby to compare before/after conversion.
When I had my engine on the dyno earlier in the year, I also had his carby to try against mine when it was a 3 circuit.
But I am happy that mine (home built) turned out better than a store brought.

With the PS, we only changed jets. It was specifically built by Pro Systems for this engine. My mate got up in the middle of the night and rang and spoke to the main guy, Patrick I think, and gave him all the spec of the motor, cam, comp, engine size, car type, fuel type, etc,etc.
Also I didn't want to open it up to many time on the dyno because I felt the bowl threads in the main body where not to good, they will strip at any time. They where like that from new. Something I will have to fix later.
From memory the A/F ratio was very similar on both carbys.
I will try and get the A/B fuel, I did see it when we where on the dyno.

I notice for the first time this morning, daylight was a bit earlier, so that means the good (racing) weather won't be far away. So I will have more info to add.
Cheers Colin.