Topic: H8PVMNT Wrestles a Weber

[:)bestgen4runner]

Picked up some reading material.  I love the classics...

I have found the mikuni carb books to be the most detailed on carb circuits and tuning help.
Have You ever considered side draft carbs?
Back about 20 years ago that was a popular setup on the 20r and 22r.

[H8PVMNT [OP]]

I have considered side drafts, but the buy in has been a factor .  A buddy has a set I may barter for to use on another engine project but flat out crazy is not really my goal for this truck.

I have a whole build in mind for another engine I want to do that side drafts would be right at home on.  You guys will love it if it actually happens .

[H8PVMNT [OP]]

So here's a trip...  We finally got into our real "summer" weather, over 70 every day, lows over 50 in the early morning.  The Weber now wants one step richer ide jet.  Totally idles like garbage on the 50 it was at the lean end of perfect on before, too lean according to the mixture screw now.  Now it loves the 55.

Would be a pain but it only takes about 25 seconds to change an idle jet since they are on the outside of the carb.

[H8PVMNT [OP]]

Ordered vac gauge today ...

[H8PVMNT [OP]]

In an experiment I stopped using 5th gear for the last tank of gas. This was based on some reading in the Weber book on what happens at what amount of vac.  I got 16.5 mpg, 2 miles per gallon better than the tank before when I used 5th on the highway.  Closer and closer to my dream of 17 mpg!

Can't wait to get the gauges in so I can see more of what's going on...

[emsvitil]

Change you change the equivalent of the power valve spring on a weber?

[H8PVMNT [OP]]

Change you change the equivalent of the power valve spring on a weber?

I don't think you can change springs readily but you can change or resize about every bit that meters fuel at every stage, so I'm sure something could be done.  The emulsion tubes seem to be where guys get massive changes in economy.  I'm still studying those they are like weird alien technology.

They sell one power valve as an assembly and don't have any springs listed.  http://www.carburetion.com/Products/ProductDetails.aspx?Part=57804.097  I'm sure you could play with random springs.

[emsvitil]

If you can't change the spring, is the spring compression/tension adjustable?

(don't have a clue of what the insides of a weber look like.......)

[Gillesdetrail]

45 idle jets
125 mains
160 air correctors
18mm float height 2mm needle travel
2.5 psi
weber 38


I installed 130 mains then 125 and it's still below 9.0:1 afr at WOT at low rpm, then around 3250 rpms it starts to go leaner until it gets to 12.5:1 at around 4k. But I now have a lean stumble from 5-15% throttle input. I had to help a friend move appartment today so I took the truck and drove 200km of highway at 18.5-19:1 afr  And I could feel the lean missfires. So I have the whole day to tune this out tomorrow, any ideas or suggestions? Floats? idle jets or main jets? I may have to do some work in the intake manifold to fix this low rpm rich condition if carb tuning doesn't do it. Something doesn't seem right.


I have ordered some new f6 tubes since the ones I drilled didn't help to lean out the bottom end at full throttle, and it may be part of the reason I get lean missfires at low throttle input. H8PVMNT, does the book say anything about emulsion tube tuning to lean or richen the mixture?

I was thinking of making a divider in the intake manifold entry to have one barrel feed two cylinders to improve low end torque and mixture, I don't know how yet without clocking the weber 90 degrees. I don't know if that is possible.

[H8PVMNT [OP]]

Man I don't know.  I would certainly richen the mains. You can't stay that lean or you will smoke something.  If you have a section of air correctors you could put some smaller ones on to richen a bit at highway rpms.

Have you tried one step richer idle jets?  I am finding they do a lot at cruising speed.

On the pig rich:  At WOT at lower rpm you have very little vac for a second when you floor it, so you aren't pulling much from the mains at all, but your accelerator pump if dumping a shot of fuel in there to compensate.  So it should get really rich for a second... But in your case does it snap out of it as rpms increase or is it just really rich all the time?

I have the progressive version so I don't know, but it seems like the 38 synchronous would dump a whole lot all at once when you stomp on it. When you ease into the throttle will it stay leaner?

I guess I don't have a solution, I'm still trying to understand myself.  I think you are on the right track with the emulsion tubes.  I think you should mess with richer (smaller) air correctors too.

When I get my AF gauge hooked up I will let you know what mine looks like.

[Gnarly4X]

Hey Gillesdetrail,

The last spec sheet on the 38 that I have is...

45 idle jets  - Stock setting:  45
125 mains  - Stock setting;  1.85
160 air correctors  - Stock setting: 1.85
18mm float height 2mm needle travel – Stock setting: .40,  Stock: 2
2.5 psi – Recommended?  3 to 4 psi?
Emulsion tube?  Stock setting:  F50
weber 38

What have you experienced or tested to change the stock specs?

What are your engine specs?
Intake manifold?
Exhaust system?
Cam profile?
Your fuel filter is fresh?
Is the fuel pump stock?
Is the fuel pressure regulated?
Have you tried increasing the fuel pressure?
What is your elevation?
What octane fuel are you running?
What air filter do you have on the carb?
Have you tried testing without the air filter installed?

Just curious? 


It sounds like its running out of fuel?  float level?  fuel pressure?  possible vacuum leak?

18 AFR is getting close to dangerously lean.

Gnarls

[Gillesdetrail]

Man I don't know.  I would certainly richen the mains. You can't stay that lean or you will smoke something.  If you have a section of air correctors you could put some smaller ones on to richen a bit at highway rpms.

Have you tried one step richer idle jets?  I am finding they do a lot at cruising speed.

On the pig rich:  At WOT at lower rpm you have very little vac for a second when you floor it, so you aren't pulling much from the mains at all, but your accelerator pump if dumping a shot of fuel in there to compensate.  So it should get really rich for a second... But in your case does it snap out of it as rpms increase or is it just really rich all the time?

I have the progressive version so I don't know, but it seems like the 38 synchronous would dump a whole lot all at once when you stomp on it. When you ease into the throttle will it stay leaner?

I guess I don't have a solution, I'm still trying to understand myself.  I think you are on the right track with the emulsion tubes.  I think you should mess with richer (smaller) air correctors too.

When I get my AF gauge hooked up I will let you know what mine looks like.

I will try richer idle jets and report back.

Wether I snap the throttle or ease into it barely makes a difference. At full throttle It will stay below 9.0 afr under around 3k even in 4th gear, and will stay rich for as long as I hold the pedal to the floor, then it will gradually go leaner to 12.5 afr by around 4k.

So far all the tests I have done with air correctors only seem to make a difference after 4k rpm so I have not played with them for bottom end or cruising speed as I don't think it will make a difference but I may be wrong. The more I think about it, the more it seems like a mixture conditioning problem in the intake manifold, unless another circuit than the mains affect AFR below 3k at full throttle which I could try to tune out.

[Gillesdetrail]

Hey Gillesdetrail,

The last spec sheet on the 38 that I have is...

45 idle jets  - Stock setting:  45
125 mains  - Stock setting;  1.85
160 air correctors  - Stock setting: 1.85
18mm float height 2mm needle travel – Stock setting: .40,  Stock: 2
2.5 psi – Recommended?  3 to 4 psi?
Emulsion tube?  Stock setting:  F50
weber 38

What have you experienced or tested to change the stock specs?

What are your engine specs?
Intake manifold?
Exhaust system?
Cam profile?
Your fuel filter is fresh?
Is the fuel pump stock?
Is the fuel pressure regulated?
Have you tried increasing the fuel pressure?
What is your elevation?
What octane fuel are you running?
What air filter do you have on the carb?
Have you tried testing without the air filter installed?

Just curious? 


It sounds like its running out of fuel?  float level?  fuel pressure?  possible vacuum leak?

18 AFR is getting close to dangerously lean.

Gnarls

The stock specs when I got the carb (setup for 22r):

idle 45
main 145
air correctors 170
f50 tubes
18mm float 2mm needle travel
recomended MAX psi: 2.5-3psi

Engine specs is 22r stock block 20r head
ported stock intake manifold with 2'' carb spacer/adapter
stock cam 0 deg advanced
ported 20r head, oversized 20r valves
DT 4-2-1 header
2" exhaust straight.
fresh fuel filter
universal electrical fuel pump
holley FPR set at 2.5psi (tried from 2-4 psi, no difference noted anywhere)
elevation around 175 feet
91 oct. 0% ethanol shell v-power
stock weber 4" air filter, haven't tried running it without the air filter. It is clean and free flowing.

Timing is set at 12 btdc right now. Anymore than that and it pings under load. I have a suzuki sidekick primary spring in the distributor and the bigger of the 2 types of weights offered in the 81-83 distributors.

18+:1 afr IS dangerously lean, and it happens only at 5-15% throttle input so slight acceleration or cruising speed. If I press down a little bit more it immediately goes to 13-14 afr and runs clean as if it was on another circuit. That will be fixed with going back to 140 mains I believe, but won't help with the WOT low rpm richness.

I'll try to get a video today after some more tuning.

[Gnarly4X]

Hey Gillesdetrail,

Thank you for the detail specs!! ... Nice engine! 

Obviously you have spent some time tuning it. 

Just thinking out loud....  if the AFR goes way lean from 5 to 15% throttle input and cruising RPM.. about 3,200 RPM??  Would the idle circuit be active or partially active?  At what RPM does the AFR go back to normal.. something above 15% throttle input? 

What would the vacuum be if you could read the vacuum during your 5 to 15% throttle? 

IF the vacuum is high, would that lean out the mixture?  If a vacuum reading is low at idle it may show a vacuum leak somewhere. 

Gnarls.

[Gillesdetrail]

So I spent some time tuning today, I tried 50 and 55 idle jets, it just ran worse so I switched back to the 45s. Ended up with this:

45 idle
140 mains
190 airs

The lean hesitation is gone and cruising speed is between 15-16:1 afr. Still needs some fine tuning though, for example if I hold the brakes with my left foot and press 5-10% on the throttle, it goes to high 17 afr and stays there. It may need 145 mains after all. I'll run it this way for a while to get the feel of it. I may add a 2" divider in the spacer below the carb and play with the cam gear a bit. I don't have a vacuum gauge.

Here is a video with the 140 mains and 170 air correctors (before I put the 190). 3rd gear full throttle from 2500 to 4800rpms. It is hard to see but it stays below 9.0:1 afr for about 5 seconds then slowly leans out to 12.7:1
https://youtu.be/g4lbGN28x3M

[emsvitil]

Could the 9.0:1 be due to much accelerator pump ??

[Gnarly4X]

So I spent some time tuning today....The lean hesitation is gone and cruising speed is between 15-16:1 afr.

I think 15 to 16 AFR is right where you want it for best gas mileage in cruise mode.

Gnarls.

[Gnarly4X]

Could the 9.0:1 be due to much accelerator pump ??

Yes.. stabbing the throttle should pump fuel into the venturi via the accelerator pump.  I don't think it would be abnormal to see a blip on the AFR meter while it dips to rich for a few seconds. 

But... I''m not a carb expert. 

Perhaps Gillesdetrail is over analyzing the AFR readings... something I would do. 

Gnarls.

[Gillesdetrail]

It is true I may be over analyzing, the general concensus is don't tune acording to what the a/f meter tells you, tune according to what the engine likes. For example, it idles best with an a/f reading of around 12.5 on idle, which seems way to rich, but that where the engine likes it. However it doesn't just dip down into the 9.0s and goes back up, it stays there for as long as I am below 3000rpms and I have my foot down. In fourth gear, It can stay below 9.0:1 for as long as I have my foot down until the rpms go above 4k. In the video I posted above, I eased onto the throttle and it stayed below 9.0 for about 5 seconds until I reach 4k. When I go up a steep hill in fourth at around 90 kph (50mph - 2750 rpms), I have a bit more power at 80% throttle where the afr will be in the high 10s-low 11s than at full throttle where in goes into the 9.0s, which is the minimum for my gauge, so it could actually be 7.0-8.0. I don't know if I'll ever be able to tune this out, I just don't want to wash the cylinders of oil and cause excessive wear.

[emsvitil]

That sounds like reversion or fuel standoff........

https://www.youtube.com/watch?v=zs8mnaouP8U

[Gnarly4X]

Hey Gillesdetrail,

It is true I may be over analyzing, the general concensus is don't tune acording to what the a/f meter tells you, tune according to what the engine likes.

Well… I won’t hold being overly analytical against you.

For performance I’ve always “tuned-by-ear” and my butt-dyno for my most used RPM range….. the MPG ended up where it did.

For example, it idles best with an a/f reading of around 12.5 on idle, which seems way to rich, but that where the engine likes it.

I don’t think 12.5 at idle is rich.

WOT or near WOT AFR and tuning is somewhat more complicated to calculate and there’s lots of research on the fuel management issues.

… I eased onto the throttle and it stayed below 9.0 for about 5 seconds until I reach 4k…

Here’s an excellent article… it gets very technical, but has basic insight into the issues for the tuner.

https://www.cartechbooks.com/techtips/wideopenthrottletuning/

The common take-away with AFR tuning is do not try to tune WOT using a narrowband (lambda) style O2 sensor, which is the most common type.  O2 sensors can “lie” about the mixture.

  I don't know if I'll ever be able to tune this out

 

If you can “tune-by-ear”, and get the throttle response where you want it, you may find that at AFR gauge readings will be confusing.

I just don't want to wash the cylinders of oil and cause excessive wear.

Although I appreciate your analytical thinking, for a healthy engine, the wear factor on oil lubricated components that your engine sees is many times greater at a cold start and idling than any amount of rich mixture at WOT.  I would be way more concerned with running at a lean mixture.

That’s just my opinion – it may be worthless.

Gnarls.

[Gnarly4X]

That sounds like reversion or fuel standoff........

https://www.youtube.com/watch?v=zs8mnaouP8U

That may be in play with his engine, but I doubt it.  Fuel stand-off is usually seen in race engines with aggressive cams and lots of overlap.

Gnarls.

[Gillesdetrail]

Good article about efi fuel and timing mapping.

If I lower the main jets, it will lean out part throttle so much that it is undrivable, but the bottom end wot is still rich. That's why I'm also starting to think it is more of a mixture conditioning issue. Maybe not enough booster signal because of the small cam. Reversion seems to be more of an issue with cams that have a lot of overlap.

[Gnarly4X]

...  I'm also starting to think it is more of a mixture conditioning issue. Maybe not enough booster signal because of the small cam. Reversion seems to be more of an issue with cams that have a lot of overlap.

Hey G,

How much WOT driving do you do?

As you know, when you get into booster signal and emulsion tubes/air bleeds, I think you’re getting into some very precise AF tuning, and perhaps more difficult to calculate results of changes.  I’m not sure your AF meter will be accurate enough, but your butt dyno may or may not sense any changes.

You might try something… with your stock 22 cam, you could tighten the valve lash from .008 and 012 to a tight .007 and .011.  That will make you cam look a little bigger.

Do you have an adjustable cam gear installed?  You could also play with cam timing.

Have you pulled the spark plugs and checked color reading?

Gnarls.

[Mudder]

Maybe I missed is, but have you checked the power valve?

[Gillesdetrail]

Maybe I missed is, but have you checked the power valve?

Nope! I had no idea of it's function, but after reading about it, I may cancel it and tune accordingly and it may help!

Gnarly: I do have an adjustable cam gear, advancing it any amount helps with bottom end and midrange but kills top end and the truck is slower overall. Checked the plugs for detonation, colour is allright. I already run the lash on the tight side, I don't think it will really make a difference. 

[Gnarly4X]

Nope! I had no idea of it's function, but after reading about it, I may cancel it and tune accordingly and it may help!

You gotta love forum "enlightenment".... sharing thoughts and experiences can be very revealing.

Gnarly: I do have an adjustable cam gear, advancing it any amount helps with bottom end and midrange but kills top end and the truck is slower overall. Checked the plugs for detonation, colour is allright. I already run the lash on the tight side, I don't think it will really make a difference. 

Hey G,

OK... I figured you are on top of the tweaks.  As you know, small changes in tuning a carb'd engine can be noticeable.  Your experience with cam timing seems similar to H8PVMNT.  Last I read, he's at 1 degree retarded.  I find it interesting that there is often talk about advancing the cam timing, however it seems that change (advanced cam timing) does not produce the desired gain in a 22 with a stock cam. 

Valve Lash:  I ran my 22R with a tighter valve lash on the stock cam and although that lash adjustment wasn't significant, the tighter adjustment did seem to let the engine pull a little better at upper RPMS.  PLUS... .it quieted the valve train!

Again... I'm just pondering your AFR issue.

Gnarls.

[H8PVMNT [OP]]

When I ran and adjustable gear on a 22re it liked advance, but my carb engine is best at 1 degree retard.  Something about the EFI likes the advance I guess.

[emsvitil]

Supposedly the 22RE cam has longer exhaust duration  and shorter intake duration than the 22R cam......

That could be the difference in advancing/retarding the cam.

[Gnarly4X]

Supposedly ......??

Perhaps true, but I cannot find any supporting data or cam specs.

And, I have mic'd the stock camshaft that came out of my 22RE?

Gnarls.