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Sun Jul 26, 2009 9:02 am

I have a couple of 2110cc engines I have been trying to tune with my new LM2. The only difference being mine is a mag case in a 61 bug, hers is a aluminum case in a 73 Super.

I was told: "13:1 is a great target to make max hp.

engine specs

CRANK/ROD SET, 82mm, VW JOURNAL,
5.5 H-BEAM RACE RODS.
90.5 B Cima Pistons,
CB 2288 cam
CB 28mm Lifters
CB 1.4 Rockers
CB 1628 chromoly push rods
Heads by K-Roc : 40 X 35.5
9.4:1 compression
12lb flywheel
kennedy stage 1
msd 6AL/distributor/coil/ 8.5mm wires
1.5/8" sidewinder

dual 45 dellorto DRLA
venturi - 38mm with the CB update kit.
accelerator pump jet - 55
idle gas jet - 60
air correction - 180
emulsion tube - 9164-2
main gas jet - 160

I have adjusted for lean best idle +1/4 turn on the mixture screw.
the distributor is set 8 degrees at idle and 30 degrees all in.
Elevation is 3000ft

original jetting @ WOT

new jetting @ WOT
62idle 162main 180 air

Which way do I go to level it out more?
I have tried a few different combinations, and I have a few different jets (50,55,57,60,62idles, 150,155,157,160,162main, 150,160,175,180,200 airs) to run, But this is the closest I have gotten mine to 13:1.

Sun Jul 26, 2009 12:02 pm

Can someone explain the spiking when the carbs switch circuits? 2500rpm 3500rpm

is this a normal thing?

and do you just try to tune the carbs so you are staying in a safe AFR zone while at WOT.

How do I get to the 15-16 AFR at cruise? and still maintain around the 13:1 at WOT?

I have collected and read all the threads from multiple sites but am still learning how to interpret the results we are getting.

This is my wifes 2110cc running a 60idle 155main and 180 air

It ran leaner at cruise but spiked up over 14 AFR at the 2500rpm and 4500rpm mark.

Sun Jul 26, 2009 12:31 pm

It's hard to tell you what's going on.. these graphs show us RPM and AFR versus time. They don't tell us what you are doing when you logged this. Are you driving with progressive throttle? Are you staying in a high gear? Do you have linkage and pedal errata causing the pumps to add fuel? Different things are going to happen under different conditions.

The dip at transition seems like an aggressive start on the main jets at tip in. How are your floats set?

You get lean cruise by using small idle jets. You are in the idle circuit at cruise.

If you want to isolate behavior and get the cruise leaned, remove the two main jet stacks from each carb, and take it for a drive. It's going to nose over at a certain point. That's when your idle circuit is done. Watch your numbers while you drive. Use the brake and 2nd or 3rd gear to simulate light load at low speeds, and get the idle jets down to 15-16 range during much of their operation.. then put the jet stacks back in and proceed.

Also, higher strung engines are harder to cruise lean with. They don't dig it as much.. so you will have to settle for as lean as the engine still "likes". Don't look for snappy power in the idle circuit. That's what the main circuit and your foot are for. :) Lean mixtures give a softer response, which is GOOD for smoother driving.

If your distributor is mechanical advance only, don't expect to be able to see 16 AFR reliably either. No vac advance means less efficient running at low throttle low cruise speeds. Do the best you can and move on.

I respect anyone that is willing to do the work to get it tuned. Good for you.

Sun Jul 26, 2009 1:05 pm

Quote: It's hard to tell you what's going on.. these graphs show us RPM and AFR versus time. They don't tell us what you are doing when you logged this.

I have been logging at wide open throttle for those.
The first was up the hill in third gear, the next with the new jetting is 2nd gear, but the 3rd to 4th gear pass on the flat highway looks the same just longer.
The wifes pass is 3rd gear up the hill at WOT.

Floats are set at 6mm

I have yet to try the jet stack removal for the idles. I will work on that. I have leaned it out with 55 idles and the cruise was up around 16 but I was concerned about it going lean when I hit WOT. I switched to the 62 and the cruise is 13:1 AFR.

I'm running the MSD and the wife has the Mallory distributor.

Thanks
Mark

Sun Jul 26, 2009 1:11 pm

Since you're at 3000 feet, a 55 idle is not unreasonable.

The idle jet is only largely affecting AFRs at lower throttle positions, you are not doing any cruise testing at WOT. When your throttles are wide open, there is no vacuum to speak of, and the idle circuit is not engaged unless there is a depression at the progression ports or the mixture port. The main circuit can be in place before 2500 RPM under these conditions.

The other factor is engine efficiency. Think about your cam and when it is designed to come on.

Sat Aug 01, 2009 1:44 pm

Finally got some work done, between crappy weather and a non responsive idle circuit on #3 plus a plug wire that liked to pop off :roll: and zap the hell out of me.

I dropped from the 62 to the 60 idle, and adjusted for lean best idle plus 1/2 turn richer, it idles at 1000rpm .

but now it is really flat/unresponsive off idle and it pops popcorn as soon as you go off the gas( it shows about 17 AFR when driving)
Too lean? richen it up? swap it for the 62?
I'm not sure if there is a idle jet clogged or what? (All the mixture screws worked while adjusting idle, and it wasn't doing the spitting out of the idle jet that tells you its clogged)
It wasn't doing that when we were running these idles before, but I don't think I had the mixture adjusted as lean.

This was a trip in third gear from 5sec-20sec was WOT, 25-40 sec was cruise in 4th gear , 55-1:25sec was 3rd gear cruise.

Sat Aug 01, 2009 2:13 pm

this was rolling into the throttle from 2000-3500rpm with the e-brake to slow me down and the same from and the same from 3000-4500rpm, from 35 seconds on was cruising in 4rd gear. I'm guessing the lean spikes are when I take my foot off the gas and get the pops in the exhaust.

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Sat Aug 01, 2009 2:33 pm

My guess is that you have a set of factory 60 jets, and some aftermarket 62s. Is this correct? If so, factory idle jets are a little smaller than the stamped value, in measurement. The 62's are probably really 62 in measurement. This means that effectively, you are almost a whole jet size up, because the size of a factory 60 is really about 57 in measurement.

Do the math.. AFR is pounds mass of air. Going from 57-62 is about a 15% reduction in CSA. With that, your reduction in pounds mass of fuel is probably close to the same. So if we assumed that you averaged 14 AFR before, which is probably close, at cruise, you would take 14/0.85 or so, and get about 16.5. Not out of the range.

So what can you do? Well you can get some true 60s in this case. This will put you in the lower 15's for AFR.

If you are not sure, you can measure your jets to make sure they are what they are supposed to be. You may find that your jets are out of whack. There have been a couple times I have ordered aftermarket jets from a popular place and got jets that did NOT measure right, in fact, too big.

For the popping out of the exhaust, that means you are going way lean at high vacuum, and with that and the weak off idle behavior, you can turn your mixtures open another turn and see if that helps. Yeah, a whole turn. Remember that Dell mixtures have a fine taper and a fine thread. They aren't going to flood out like an IDF would.

Sat Aug 01, 2009 3:17 pm

Thanks Mark
I'll give that a go

I have the jet drills and gauges, and noticed the other day that the gauge pins are not exactly what they say. And yes I have bought jets that when slid on the jet drills have been no where near the same.

What I have started doing is, all my idle jets have been measured on the same jet drill and I document the distance from the base of the jet to the bottom of the drill
--<[--------] =37mm and the gauge size 60 if it's a snug fit in a gauge. Then I made them sets of 4 of equal measurements.

idle jets worked out like this
63 = 30mm drilled
61 = 35.5mm drilled
60 = 37mm factory
55 = 44mm factory

mains
162 =54mm drilled
160 = 58mm factory
157 = 64mm drilled
155 = 67mm factory
155 = 64mm factory

Some were mistery jets that others had given me that had been drilled before, some came with the spare parts for the carbs when I bought them.

This way at least I know they are all the same and I know if i'm going up or down on the actual size.
I have also bought some miniature drill bits to use the shanks to check some of the in-between sizes. of course they need to be measured for accurate sizing too.

1.51mm = #53 drill
1.58mm = 1/16" drill
1.61mm = #52 drill

.5715mm = #74
.6096mm = #73
.6350mm = #72
.6604mm = #71

Ya I know it's a little over the top :roll:

Mon Aug 03, 2009 3:20 pm

I'm still not clear if you figured out what your actual jet sizes were, but you see and understand the need to measure them and make sure they are all the same. Drills are not a good way to size jets. Reamers are. Air jets you can get away with it a little more. Fuel jets, I would ream them. Idle jets are very critical. When you set their size, your reamers must be sharp and clean, and you must be precise... small errors on those tiny holes mean big differences in their behavior.

Your engine may not tolerate 16-17 AFR.. you may have to go down around high 14's to mid 15's for stability, but do what you can. The gains at 16 are minor compared to 15.. just getting into that range makes big differences for economy. Your engine is not geared for economy, so get as close as you can.

Did you try to adjust the mixtures out to see if you can get the decel popping down? I still get a little up there, but it's not popcorn, just some random small huffs. I probably have a little bit of an exhaust leak too. Your exhaust setup has a lot to say about it too.

Mon Aug 03, 2009 3:48 pm

The ones i have in there are the 60's

I did adjust it 1 full turn, but the wife took it out after that.
So it is better, but my LM2 O2 sensor is acting up and I'd like to drive it myself to see how it's running now.

Both our sidewinders seem to like to huff a little unless we're running rich.

Quote: Drills are not a good way to size jets. Reamers are

I just use the shank of the drill to measure the odd jet sizes, the reamers do the sizing.

I'll report back when I get things going with the sensor.

Thanks
Mark