Asking for help Interpreting AFR readings from new Weber 32/36

[matrophy]

I was struggling to dial in my new Weber on my stock Z24 with all Cal smog stuff removed but the carbon canister.

Partly to help solve this and partly because it's a cool gadget, I bought an AEM AFR gauge and I am using it on the Lambda setting

because we run E10 here. I got the Weber to idle real nice after increasing the idle jet size from 60 to 70.

 

Some of the Lambda readings are a little wacky and I could use some help interpreting them.

The acceleration from a stop is real sluggish and as the AFR readings below suggest probably because it's running lean

 

Lambda converted to AFR in parentheses

 

Idle - 0.960- 0.98 (14.4) - Not sure if I am supposed to tweak the idle mixture to get a 1.0 reading but where it idled best ended up being 0.96-0.98

 

Cruise = 1.0 - 1.02 (14.7 - 15.0) 55 mph on level highway

 

Acceleration 1.07 (15.7)- lshifting through the gears from a stop and the response is real sluggish - not dropping off like what happens when you stomp on it with this carb - just weak acceleration. My understanding is that should be a rich reading - like 0.80 - 0.90

 

Under load - 0.98 - 1.01 (14.4 - 14.8) 20 mph uphill in 2nd gear. I believe this should also be richer - like 0.80 or so

 

WOT - 1.05 - 1.07 (15.4 - 15.7) I believe this probably OK and the truck accelerates decently here

 

 

No vacuum leaks

Timing is at 3BTC

New plugs

175 Compression in all 4 cylinders

68000 miles on original engine

 

I think the idle, cruise and WOT are OK it's just the acceleration reading that I'd like to somehow fix to get a little more pep.

[datzenmike]

Are not wide open throttle and acceleration basically the same thing?

 

 

Idle, light throttle and cruise you want close to 14.7 for strictly mileage. Again it's a bell curve with not a lot of difference between 13.7 and 15.7 but it does drop of steeply on either side. When throttle is floored under load or acceleration, you want richer, even down to 12.5

 

Originally (and mistakenly) I increased the jet sizes in my R-1 carbs and got a 9.6 under acceleration. I think this is the lowest the A/F gauge will read so it could very well have been lower. I thought I could see a faint black smoke (super rich) like the choke was on. I worked my way down in jet sizes and up on the gauge to the mid 12s. Accelerates the same but no black smoke. Running too rich seem to run ok it just wastes gas out the tailpipe. Somewhat lean is ok if cruising, light throttle but never under load.

[Charlie69]

On the Z24 with the stock jetting running rich at idle is common but not on cruise or top end.  2400 CCs is about the top limit of this carb.  I have always been able to correct rich idle with the idle screw adjustment.  The only time I have re-jetted any Webers were for the L motors. All the Z20s, z22s and Z24s I have run the stock jetting that come in the new Redline carbs.

 

The redline kit #s I buy are:

K664 = Z24

K662 = Z20 & Z22

K660 = L20B

 

I do not run the L16/L18 engines any more.

[matrophy]

11 hours ago, datzenmike said:

Are not wide open throttle and acceleration basically the same thing?

 

 

Idle, light throttle and cruise you want close to 14.7 for strictly mileage. Again it's a bell curve with not a lot of difference between 13.7 and 15.7 but it does drop of steeply on either side. When throttle is floored under load or acceleration, you want richer, even down to 12.5

 

Originally (and mistakenly) I increased the jet sizes in my R-1 carbs and got a 9.6 under acceleration. I think this is the lowest the A/F gauge will read so it could very well have been lower. I thought I could see a faint black smoke (super rich) like the choke was on. I worked my way down in jet sizes and up on the gauge to the mid 12s. Accelerates the same but no black smoke. Running too rich seem to run ok it just wastes gas out the tailpipe. Somewhat lean is ok if cruising, light throttle but never under load.

I didn't mention that it runs lean on the gauge and sluggish when accelerating with 60, 65 and 70 primary idle jets.   I stuck with 70 because I got the best idle and the widest sweet spot than the other 2 - probably subjective but it felt better.  I'm assuming that the lean reading and the sluggishness are related but maybe 1.07 is not that far away from 1.0 if the curve is flat at the top for a while. In any case, like you said, it should be rich - not lean - so I'm not sure what to do. Charlie69 gave me some tips in another thread to look at the insides of the carb for damage. Given that the float that came with this carb was twisted all over the place it seems like a good idea to take a look.

 

I may have said it wrong but what I called WOT was when I was cruising at 55 mph and floored it. The throttle response was fine then but not when shifting through the gears

[datzenmike]

It may briefly go lean during a shift when you let off but should immediately go rich once the pedal is stepped on. It should never go lean. I have R-1 motorcycle carburetors, somewhat like SUs and they are much different than a regular carburetor. They go briefly rich as you let off then go into the lean range. On some let offs even 17s and 18s.

[Icehouse]

My NA SR hits 10's at full throttle at the lower RPM's then goes into the 11's.  Full throttle is never above 12 and it's a stock ECU NA motor.  

[matrophy]

I still feel like I'm running too lean and sluggish acceleration. I settled on a 55 idle jet and I'm happy with the idle. I attached a chart showing what lambda readings I'm getting accelerating through the gears which feels sluggish and cruising at 60 mph. Does this indicate that I should go with larger main jets and if so, what is a good recommendation for how many sizes up? Both main jets are 140's now.

60 mph chart.pdf

[Charlie69]

Are you running premium or low octane?  I always run premium.

[matrophy]

10 hours ago, Charlie69 said:

Are you running premium or low octane?  I always run premium.

Hadn't thought about that. I'm running the Chevron mid-grade whatever that octane is

[Charlie69]

Run several tanks of premium and see what your readings are and how the truck feels.

[datzenmike]

Octane is a resistance to self or auto ignition. You can compress it more or increase the timing advance to increase efficiency. There's no advantage to using it if you have a lower compression engine.

 

What timing do you have right now? Can you increase it without it pinging?

[Madkaw]

I bought the Redline kit and put the largest jet sizes and pump jets that were in the kit . This was after installing the lamba gauge and realizing how lean these Weber’s come out of the box . It’s a carburetor so there will always be a compromise . With the larger jets you can turn in your mixture screw less than one turn . I personally can’t wait to go EFI . 

The problem with tuning for power with a carb is that it’s harder to get a lean cruise . 
I’d get a Redline kit and continue tuning . Your numbers are decent , but WOT is not rich enough . 
Timing has a lot to do with it also , but with a dizzy curve you are playing with fire . Currently I’m running a Megasquirt controlled coil pack so I can get away with advancing the timing - which helps . Not sure what the limits will be . 
I bet I gain 20hp with EFI 

[matrophy]

50 minutes ago, Madkaw said:

I bought the Redline kit and put the largest jet sizes and pump jets that were in the kit . This was after installing the lamba gauge and realizing how lean these Weber’s come out of the box . It’s a carburetor so there will always be a compromise . With the larger jets you can turn in your mixture screw less than one turn . I personally can’t wait to go EFI . 

The problem with tuning for power with a carb is that it’s harder to get a lean cruise . 
I’d get a Redline kit and continue tuning . Your numbers are decent , but WOT is not rich enough . 
Timing has a lot to do with it also , but with a dizzy curve you are playing with fire . Currently I’m running a Megasquirt controlled coil pack so I can get away with advancing the timing - which helps . Not sure what the limits will be . 
I bet I gain 20hp with EFI 

Are you referring to idle jets or main jets? I had to go down to a 55 idle jet from 60 to get the best lean best idle. The idle seems to run pretty close to stoich now. 

[captain720]

Personally I think your WOT/acceleration is lean and that's why it's slow. I have the same gauge behind a 350 and I have WOT at about 12 and it's great. If WOT is 15 or leaner your loosing power in my opinion.

[matrophy]

6 minutes ago, captain720 said:

Personally I think your WOT/acceleration is lean and that's why it's slow. I have the same gauge behind a 350 and I have WOT at about 12 and it's great. If WOT is 15 or leaner your loosing power in my opinion.

I agree. I'm just trying to figure out what to do to the carb to fix it

[datzenmike]

If a 32/36, increase the jet in the secondary. It's used during WOT but won't affect low speed mixtures and certainly not idle.

 

Running richer cools the combustion chamber and spark plug during WOT. This allows you to run more timing than you could with a perfect mixture 14.7 : 1  but the gas is wasted as a cooling agent. There is only X amount of oxygen to be burned. Adding more gas just goes out the tail pipe. 

 

Back in the '70 there was water injection. This was a measured spray of water down the carburetor during WOT that would absorb heat by being turned into steam. It didn't waste gas but it had a cooling effect. You could use a lower octane gas in a higher compression engine to reduce pinging.

[Madkaw]

Tuning will be very limited with a fixed timing curve and a carb - period . 
It’s amazing how lean you can run with being able to advance timing to advantage of the slower burn rate with EFI .We are also limited the 40 year old combustion design .

I’m hoping a turbo will better suit the design 

Edited June 23, 2021 by Madkaw

[DIY 1985]

If your valve lash is excessive, your engine can't breathe.  If the top of the intake, or exhaust, valves are caked with burnt-on oil, same problem.

 

An A/F readout isn't a substitute for an old-school vacuum reading.

 

Plugs need to be tan on the insulators, not black, white, or shiny black.

 

I'm assuming this is a 32/36 progressive Weber?  The pump jet for this carb is offered in only one size, but you might be able to drill it out, if necessary.

 

Is this the stock 86 exhaust manifold?  My Nissan exhaust bung seems fine, but on my Land Cruiser, I put one behind the collector of the header, it is too sensitive to temperature, and I get inconsistent readings with different O2 sensors. 

 

How many turns on your idle speed screw, and idle mix screw?

 

 

Edited June 26, 2021 by DIY 1985

[Madkaw]

On 6/26/2021 at 8:25 AM, DIY 1985 said:

If your valve lash is excessive, your engine can't breathe.  If the top of the intake, or exhaust, valves are caked with burnt-on oil, same problem.

 

An A/F readout isn't a substitute for an old-school vacuum reading.

 

Plugs need to be tan on the insulators, not black, white, or shiny black.

 

I'm assuming this is a 32/36 progressive Weber?  The pump jet for this carb is offered in only one size, but you might be able to drill it out, if necessary.

 

Is this the stock 86 exhaust manifold?  My Nissan exhaust bung seems fine, but on my Land Cruiser, I put one behind the collector of the header, it is too sensitive to temperature, and I get inconsistent readings with different O2 sensors. 

 

How many turns on your idle speed screw, and idle mix screw?

 

 

The redline kit comes with at least 2 bigger size pump jets- at least my kit did  . There is quite a bit on tuning you can do with the kit . 

[matrophy]

On 6/26/2021 at 5:25 AM, DIY 1985 said:

If your valve lash is excessive, your engine can't breathe.  If the top of the intake, or exhaust, valves are caked with burnt-on oil, same problem.

 

An A/F readout isn't a substitute for an old-school vacuum reading.

 

Plugs need to be tan on the insulators, not black, white, or shiny black.

 

I'm assuming this is a 32/36 progressive Weber?  The pump jet for this carb is offered in only one size, but you might be able to drill it out, if necessary.

 

Is this the stock 86 exhaust manifold?  My Nissan exhaust bung seems fine, but on my Land Cruiser, I put one behind the collector of the header, it is too sensitive to temperature, and I get inconsistent readings with different O2 sensors. 

 

How many turns on your idle speed screw, and idle mix screw?

 

 

21" of vacuum

Roughly 1/2 to 3/4 turn in on speed screw and roughly 2 turns out of mixture screw,

compression = 175-170-175-175

Plugs are white now because it runs lean in concurrence with AFR readings

Stock exhaust manifold

[matrophy]

1 hour ago, Madkaw said:

The redline kit comes with at least 2 bigger size pump jets- at least my kit did  . There is quite a bit on tuning you can do with the kit . 

Seems like a good idea to try increasing the size of the main jet. I'm just not clear how far up to go and also whether both main jets should be changed at the same time in the same amounts

[DIY 1985]

My Redline kit suggests that no more than 1.5 turns out on the idle mix screw.  I understand that as keeping the first progression hole balanced with the idle mix feed.  Closing the idle mix will enrich the rpms above idle.  You might remove the idle mix needle, and purge that hole with compressed air just to make sure.

 

What is your float drop setting?

 

My DGV is running 55s on both idle jets, 165 on the primary air corrector with 160 on the secondary, a 140 primary main and 135 secondary main.  My idle speed screw is maxed out at 1.5 turns in.  I'm at altitude, 7,000'.

 

You might make sure that the stop screw on the secondary is closed by looking from the top with a flashlight?

 

It seems like there is air coming in from somewhere, if you really are at .5 turns in on the idle speed screw, and the stock jets for a Z24 kit are so lean that it is observable with street performance?

[matrophy]

7 minutes ago, DIY 1985 said:

My Redline kit suggests that no more than 1.5 turns out on the idle mix screw.  I understand that as keeping the first progression hole balanced with the idle mix feed.  Closing the idle mix will enrich the rpms above idle.  You might remove the idle mix needle, and purge that hole with compressed air just to make sure.

 

What is your float drop setting?

 

My DGV is running 55s on both idle jets (same), 165 on the primary air corrector with 160 on the secondary (170/160), a 140 primary main and 135 secondary main(140/140).  My idle speed screw is maxed out at 1.5 turns in.  I'm at altitude, 7,000' (400').

 

You might make sure that the stop screw on the secondary is closed by looking from the top with a flashlight?

 

It seems like there is air coming in from somewhere, if you really are at .5 turns in on the idle speed screw, and the stock jets for a Z24 kit are so lean that it is observable with street performance?

I know. It acts like there is a vacuum leak but I sure can't find one. If it wasn't forecast for 109 degrees here today, I was going to try a smoke test and brake cleaner test again to make double sure. I get 21 in/Hg steady on the vacuum gauge so I assume that means there isn't a large leak? The secondary is definitely closed all the way. Float is newer than the carb because out of the box, my float was bent to shit. It's adjusted to whatever the specs are and I have only driven the truck like 40 miles max so I have to assume that it is still OK. My Redline kit instructions say 2 turns out on the mixture screw is ideal and 2-1/2 turns is too much. I'm running similar jetting to yours (mine noted in BOLD above). AFR reading suggests that idle circuit is good but that the main jets might be too small - at least based on my limited understanding of the system.

[datzenmike]

21 is exceptionally good for idle.

[matrophy]

21 inches  would suggest no major leaks at least, right, or no?