Topic: H8PVMNT Wrestles a Weber

[H8PVMNT]

The concept of the power valve delete is intriguing.  There was a tiny blip about that being done in the weber book but no real details or reasoning.  I am just starting the section about modifications though, maybe it's in there.

[H8PVMNT [OP]]

I have the AF and vac gauges running now so I thought I should post it up here.  This is the out of the box jetting.  Idle and main are a tiny bit rich at 13:1 to 14:1 which makes sense at my elevation.  Secondary gets 11:1 to 12:1 when I hog on it, which might be OK I'm not sure.   I get a lovely 15.7:1 lean cruise just barely into the primary at 60 mph on flat ground.  If you have a bit of load it is in the 14s.  This is my magic 17 mpg spot.  I will see what it feels like when I lean the secondary out a bit.  I will change the jet first and then the air corrector and see what goes on with the gauge.

Now we can really geek out.  Stink it up Gnarls!   

[Gnarly4X]

H8PVMNT!!

I'm so glad you are now an AFRter Farter!! 

I'll put some stink on this later. 

Gnarls.

[Gnarly4X]

Hey H8PVMNT,

OK… I’m not sure where you are getting your lean/rich numbers?  Although those numbers represent an excellent tuning job without an AFR gauge. 

13 and 14 are not typically considered rich, aren't those numbers in the lean to Stoich range? 

11 to 12 for WOT is just about right. 

The 15.7 is a good lean cruise, but for your elevation a slightly lower number would be more expected.   
If you “have a bit of load” are you into the secondary? 

For your target MPG, your “magic spot” should be between 15 and 16, considering your elevation. 

Remember, your combustion chambers are most likely not biased…. number 1 may burn leaner and 3 may burn richer, so be careful when “leaning’ the jetting. 

Also, as you go toward the lean end, you are going to drop some torque, so wouldn't it make sense that the RPM where you want your 17 MPG should be very close to your peak torque RPM range? 

I would color a fresh set of plugs and see which cylinders are noticeably firing a slightly different mixture – if any. 

That is purely speculation and laced with Gnarly’s “stink & pomp”, and just my opinion, of course it may be worthless. 

My carb tuning skills probably would not make a pimple on your butt.....

...but I have to stink things up where I'm allowed. 

Gnarls. 

[H8PVMNT [OP]]

Hey H8PVMNT,

OK… I’m not sure where you are getting your lean/rich numbers?  Although those numbers represent an excellent tuning job without an AFR gauge. 

13 and 14 are not typically considered rich, aren't those numbers in the lean to Stoich range? 

I was just kind of going off the ideal 14.7 everybody strives for in all the tech articals.  I am guessing anything north of 13 and less than 15 is probably pretty good.  I have a feeling that hunting for 14.7 will not yield the best drivability though.  We will see.

[H8PVMNT [OP]]

On the "bit of load"  I am still cruising on the main jet at that time.  From what I read the lean cruise is probably still in the transition stages of the idle circuit at about 10-15% throttle.  When I hit the secondary it immediately drops to 12s, if I am really on it 11s.  This is when it feels like it can actually get out of it's own way  .

When I am accelerating up a hill in 3rd it leans to about mid 13s at higher RPMs, which is the effect of the air corrector jets working as RPMs increase.  It is fun to actually see the different circuits kicking in on the gauge.

[Gillesdetrail]

For max performance at WOT you are shooting for 12.5-13:1. For best idle mines likes 13.3-13.5:1, what about yours?

Don't try tuning for 14.7, unless that is where the engine responds best for the condition. I have good response and fuel economy cruising at 16.5-16.8 at 3000rpms 4th gear, timing at 11 deg. btdc.

I have removed the powervalve but I have not started tuning yet, I just upped the mains and did a test drive, big difference at low rpm wot, it is not as rich and I have much more torque! I'm pretty happy about that.

[Gnarly4X]

Hey H8PVMNT,

Tuning for best power and tuning for best MPG at the same time will be a real challenge.  Some “AFR-tune-masters” say that “max power” is about 10% richer (13.23) than Stoich 14.7 and a slight advance in ignition timing.  What is max power and where in the RPM range do you want it to be?

For me I would be monitoring the gauge reading at specific RPMs under several throttle positions.

My first focus would be at my most used power band range 2800 5th gear 67 MPH to 3300 5th gear 80 MPH.  This is where I drive on the freeways and where I want my peak torque numbers and a healthy AFR with good gas mileage.

On around town streets, the power and MPG is less important to me, I’ve got gears.

At WOT going through the gears is less important because I’m not drag racing.  For passing, pulling grades, and when hauling, then 3rd gear, 4th gear, and 5th gear become important for max power.  At WOT or close to it, I would assume I’m going to be between 4,000 and 5,000 RPMs, with only a quick bounce to 5,500+.  At WOT I would not be concerned about gas mileage since I'm only there for a few seconds.

That’s just my stinky opinion.

Gnarls.

[Gnarly4X]

For max performance at WOT you are shooting for 12.5-13:1. For best idle mines likes 13.3-13.5:1, what about yours?

Don't try tuning for 14.7, unless that is where the engine responds best for the condition. I have good response and fuel economy cruising at 16.5-16.8 at 3000rpms 4th gear, timing at 11 deg. btdc.

I have removed the powervalve but I have not started tuning yet, I just upped the mains and did a test drive, big difference at low rpm wot, it is not as rich and I have much more torque! I'm pretty happy about that.

Gillesdetrail,

Your numbers do seem to track what the "experts" say.   

Good job. 

Gnarls.

[H8PVMNT [OP]]

17.14 miles per gallon last tank!

[Gnarly4X]

1st time at 17, right? 

Did the gauge do that? 

Gnarls. 

[H8PVMNT [OP]]

I have broke 17 one other time, maybe twice.  The gauges help you drive for economy, yes.  You can really see what's going on.

[Gnarly4X]

I have broke 17 one other time, maybe twice.  The gauges help you drive for economy, yes.  You can really see what's going on.

Soooo.... what about the poop...??  Still have good poop??  Where in RPM range is the most poop! 

Gnarls.... looking for good poop! 

[H8PVMNT [OP]]

Well, it has good bottom end, good mid and good top end.  It has a nice 800 rpm idle and it crawls real well at idle.  The Aisan had a bit more idle torque but it also liked  slightly higher idle speed.  The lower rpms pull nice and it has the most torque from I would say 2,500 to about 5,000 rpm.  Steady pull all the way except when you roll into the secondary you get a nice little boost. The tweaked up Aisan hit harder on the secondary than this carb but the Weber had a lot more mid range torque.

I am pretty impressed with it even with this kind of economy it still goes good.  I feel like I could get a bit more economy out of it but I think it's in a pretty happy compromise spot right now.  You do have to drive it right to get 17 mpg, cruise in 4th gear no more than 65.  If you do 75 or 80 and use 5th you still get around 14.5-15.5 mpg though and that isn't bad for this truck.
.
I think I will dink with the main jets just a little bit.  I still think I am a little rich at the top of the primary and the start of the before the air correctors kick in.

So if I was drag racing I would choose the Aisan and if I was rally racing I would choose the Weber, if that makes sense.  The Aisan was more snorky, and had a little more "buck", probably because it goes from lean to rich and can't transition as well when you open up the intake and all that.  It had more flat out acceleration, and he Weber has more all around pull and is smoother, at least the way it is jetted now. 

If I was driving back and forth to work I would choose the Weber, which is what I am doing .

[Gnarly4X]

....  You do have to drive it right to get 17 mpg, cruise in 4th gear no more than 65.  If you do 75 or 80 and use 5th you still get around 14.5-15.5 mpg though and that isn't bad for this truck.

Great tech... thank you.  Very interesting. 

In my Corolla, when I drive 79 on the freeway back and forth to work, it gets an average 30.5.  If drive 75 down the freeway, it will get 32.0.  I haven't tried lower freeway speeds yet. 

What RPM are you at when you drive 65 in 4th?   What does the gauge read? 

What does the gauge read when you are in 5th gear at 75 MPH and what RPM? 

Gnarls.

[Plainview]

Been awhile so just wanted to check in and say thanks H8PVMNT for doing all this research.  I feel like I owe you some money since you're saving me a bunch of time trying to figure this all out on my own.  If we ever meet, beers on me!

[Gillesdetrail]

Yes thanks a lot, we all appreciate! What is your a/f ratio aprox. at best idle and full throttle 2000-4000 rpms? Drove mine 3 hours last friday, 45 idles, 145 jets and 160 airs with power valve removed. Drove better than ever, until I ripped the front leaf mounts from the frame on the trail on saturday I need to lower the air correctors 1-2 size still and I'll have it perfect a/f and timing wise, but it will be a while.

[300k]

you were pulling the 3rz HARD up those hills! and that slope you drove up was amazing for a carb. nice, NICE, REALLY NICE work there!

[H8PVMNT [OP]]

What RPM are you at when you drive 65 in 4th?   What does the gauge read? 

What does the gauge read when you are in 5th gear at 75 MPH and what RPM? 

Gnarls.

65 in 4th is about 3,500 rpm.  AF is high 15s to low 16s on flat ground.  Vac is around 7-10 Hg.  If I try to stay between 60 and 65 in 4th I get 17 mpg.

75 in 5th is maybe like 3,250.  AF is between 13 and 14.  Vac is around 1-5 Hg.  If I use 5th I can only get 14-15 mpg, even if I go slower.

[H8PVMNT [OP]]

Yes thanks a lot, we all appreciate! What is your a/f ratio aprox. at best idle and full throttle 2000-4000 rpms? Drove mine 3 hours last friday, 45 idles, 145 jets and 160 airs with power valve removed. Drove better than ever, until I ripped the front leaf mounts from the frame on the trail on saturday I need to lower the air correctors 1-2 size still and I'll have it perfect a/f and timing wise, but it will be a while.

Best idle AF hovers around mid to high 13s. I have had the idle around 14.5-14.7 but it seems to like 13s better and I get better off idle torque a little richer. Seems to vary a bit on temp though.  I would expect a winter tune is necessary when it gets colder.  I also notice the idle speed screw will move around a bit.  I am thinking of putting a drop of blue loc-tite on it but I don't really mind adjusting it every once in a while. If you have the idle speed screw open too much it gets richer.

WOT I am getting from 10.9 to 13.4, about .

When I get in the higher rpms the air correctors really seem to trim it out then it will go to 14.5-15 and I also get into more Vac which seems to be good.

[H8PVMNT [OP]]

Had an interesting thing this morning.  Yesterday my wife towed our 19 foot flatbed full of hay. It was a hot day, higher rpms and low Vac.  The 20R head I have on has questionable valve guides and my bottom end is nice and tight.  This is a recipe for blow by that seems to be getting more pronounced as the fresh valve seals get some miles on them and become less effective.  Long story short I get a little oil drip out of the PCV breather filter, not terrible but enough to wipe it off about once a week.  Every once in a while if the conditions are right it will puke a whole bunch at once and it's a real mess.  This seems to be hot, high rpm low vac conditions, like towing too much.


I went and took the filter off and put a hose back to the air filter box and with the towing and perfect conditions it puked enough oil to saturate the filter pretty good.  The AF was 2 points richer today from the restriction of the oily filter.  I soaked the filter in detergent and blew it out.  We will see if it helps until I can get a fresh filter.

I have acquired in trade a really nice 20R head with much tighter valve guides.  I need to check the rest of it out but I think I will swap it out one of these days to cure the root cause of the issue.

This has less to do with the carb but it's notable the effect restriction of an air filter has on A/F ratio.

[emsvitil]

Motorcycle trick.........

A dab of RTV will keep the idle screw in place after you've set the screw where you want it.

[Gillesdetrail]

Best idle AF hovers around mid to high 13s. I have had the idle around 14.5-14.7 but it seems to like 13s better and I get better off idle torque a little richer. Seems to vary a bit on temp though.  I would expect a winter tune is necessary when it gets colder.  I also notice the idle speed screw will move around a bit.  I am thinking of putting a drop of blue loc-tite on it but I don't really mind adjusting it every once in a while. If you have the idle speed screw open too much it gets richer.

WOT I am getting from 10.9 to 13.4, about .

When I get in the higher rpms the air correctors really seem to trim it out then it will go to 14.5-15 and I also get into more Vac which seems to be good.

Good, the 32/36 seems way better for off-idle power than a 38. I would be worried at 14.5-15:1 afr at full throttle higher rpms though. Not only is it not rich enough for best power, but detonation would be more likely I think. Lower the air correctors one or two sizes and compare, I'm sure you'll be glad. When I play with air correctors I notice the change exactly at 4k rpms on. I have read than for a 22r a good ball park is to have the air correctors 30 sizes up from the main jets, and that is where I ended up before removing the power valve. Try to be mid 12 to maximum 13.5 for WOT for best power and safety   

[Gnarly4X]

... This has less to do with the carb but it's notable the effect restriction of an air filter has on A/F ratio.

Are you talking about the air filter on the rocker cover, or the air filter on the carb?

Gnarls.

[Gnarly4X]

....  I am thinking of putting a drop of blue loc-tite on it ...

You're just kidding, right? 

Gnarls.

[Gnarly4X]

65 in 4th is about 3,500 rpm.  AF is high 15s to low 16s on flat ground.  Vac is around 7-10 Hg.  If I try to stay between 60 and 65 in 4th I get 17 mpg.

75 in 5th is maybe like 3,250.  AF is between 13 and 14.  Vac is around 1-5 Hg.  If I use 5th I can only get 14-15 mpg, even if I go slower.

QUICK MATH..

If you drove 50 miles at 65 MPH @ 17 MPG
Gas is $3.00 per gallon
Your fuel cost is $8.82
You would reach your destination in 46.2 minutes

If you drove 50 miles at 75 MPH @ 14 MPG
Gas is $3.00 per gallon
Your fuel cost is $10.71
You would reach your destination in 40.0 minutes

At 75 MPH you would arrive at your destination 6.2 minutes sooner…. but it would cost you $0.30 per minute.

It would cost you $1.89 more in fuel driving that distance at 75 MPH.

Gnarls.   .... stink & pomp

[H8PVMNT [OP]]

I would be worried at 14.5-15:1 afr at full throttle higher rpms though.

I should clarify, and I had to look during the drive to work today to verify... I am in the 12s at WOT at high rpms, I only get the -14-15s A/F when I am backing off the throttle to maybe 50% at say 4,200-4,500, like when you drop to third going up a hill and you no longer need WOT. If I floor it at that point I get right back to 12s and accelerate up the hill .

[H8PVMNT [OP]]

Are you talking about the air filter on the rocker cover, or the air filter on the carb?

Gnarls.

The air filter on the carb...

I took the little filter off the rocker cover and hooked the vent back to the air cleaner like you are supposed to, then it puked just enough oil, maybe a tablespoon, to saturate the air filter on the carb.  I put the valve cover breather filter back on and after cleaning and blowing out the air filter my A/F is back to normal.

I am playing with different style PCV baffles right now but I think ultimately I need new valve guides.  If I have to swap heads again I am sorely tempted to try the 282 cam in the 4runner .

[Gillesdetrail]

I should clarify, and I had to look during the drive to work today to verify... I am in the 12s at WOT at high rpms, I only get the -14-15s A/F when I am backing off the throttle to maybe 50% at say 4,200-4,500, like when you drop to third going up a hill and you no longer need WOT. If I floor it at that point I get right back to 12s and accelerate up the hill .

Great! Sounds about the same with me!

[emsvitil]

QUICK MATH..

If you drove 50 miles at 65 MPH @ 17 MPG
Gas is $3.00 per gallon
Your fuel cost is $8.82
You would reach your destination in 46.2 minutes

If you drove 50 miles at 75 MPH @ 14 MPG
Gas is $3.00 per gallon
Your fuel cost is $10.71
You would reach your destination in 40.0 minutes

At 75 MPH you would arrive at your destination 6.2 minutes sooner…. but it would cost you $0.30 per minute.

It would cost you $1.89 more in fuel driving that distance at 75 MPH.

Gnarls.   .... stink & pomp

And I can make more than $1.89 in 6.2 minutes..............
 


Speeding pays.......