what are the symptoms of a main jet that is too small (lean). I know that a small idle jet can cause popping through the exhaust and or carbs. No idle, herd starting ect. but what about the main. Also how do I read the plugs for adjusting the main jet? Do I drive it floored at 3-4k then shutdown and read, or just read after normal driving.
My jetting is good right now but I think I can go leaner. I would like to increase my MPG. I'm getting 17-20 in a 1.8 914 with 40 IDFs.
55 idles 135 mains. I do not have a head temp guage (that would make things to easy) so what other clues are there. The guage is on the list, after I get some kind of paint on the car.
Weber jetting and overall settings (Any suggestions Jake)
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914fan
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Weber jetting and overall settings (Any suggestions Jake)
Last edited by 914fan on Fri Mar 04, 2005 10:05 am, edited 1 time in total.
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914fan
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I baby it. I usually cruise the freeways at 2700 - 3100 rpm. (60 to 70 ish) It does that with my foot barely touching the pedal. I wish I could just not push it. I had first run it with 50 and 115. drove it that way for over a month. I got 27MPG but had issues with the idle being to small. I was also having MAJOR issues with intake leaks. I had a leak every week. I finaly got pissed and just used rtv. No leaks yet. I switched to the 55 135 durring the leaking time and saw a BIG drop in milage. I put in the 50s again to try and get some milage back but was having intermittent lean idle issues. I am happy with the 55 it idles and drives great. I may expierement with the 115 again to see the difference in driving. You may very well be correct and I should leve the 135s in. I'll try it on a couple short trips, see what she does.
Does anybody know what I should look / listen for in a lean main jet.
Also what about reading the plugs. How to I read them for the main jets?
As a side note the biggest difference I see in milage is more a reflection of the fuel I use than anything else. Chevron runs 3mpg on average better than anything else. (87) using 89 and 92 does not realy make a difference in milage but does shooth out the idle a bit. with the 50s in the car would usually not idle unles I was running chevron 87 or better. I tried 92 octane on other brands and did not see improvement over 87 chevron. just my expierence.
Does anybody know what I should look / listen for in a lean main jet.
Also what about reading the plugs. How to I read them for the main jets?
As a side note the biggest difference I see in milage is more a reflection of the fuel I use than anything else. Chevron runs 3mpg on average better than anything else. (87) using 89 and 92 does not realy make a difference in milage but does shooth out the idle a bit. with the 50s in the car would usually not idle unles I was running chevron 87 or better. I tried 92 octane on other brands and did not see improvement over 87 chevron. just my expierence.
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Piledriver
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914Fan:
Sumtingwong.
I have an internally stock 914 1700, 44IDFs, 135 mains, 180 AC, 65 idles, F11 tubes, and get CONSISTENTLY >40MPG, admittedly babying it, but with occasional WOT episodes for onramps etc.(Dallas Traffic)
At light throttle, you are 100% on the IDLE circuit in a 914...
Barely touching the throttle to go 70MPH...
The needle adjustment is extremely critical...
Mine are just "cracked" perhaps 1/16>1/8 turn, which is the "wrong" way to set it up, but it has worked best for me.
I tried smaller idle jets to get the needle adjustment into the 1/4>2 turn range, but the car would run like ass.
I'm running 195/65-15 Michelin Pilots.
I am running a late bus distributor with the slop taken out of the springs, and the stops tweaked slightly... 12-15 BDTC initial, and 28 final... With working Vacuum advance, ported to all 4 throttle plates.
I got similar mileage without the vac advance wit 32 final mechanical, but the motor wanted less at WOT. Your motor will likely prefer 32.
My compression ratio is ~8.7:1, no gaskets on jugs or heads.
Sumtingwong.
I have an internally stock 914 1700, 44IDFs, 135 mains, 180 AC, 65 idles, F11 tubes, and get CONSISTENTLY >40MPG, admittedly babying it, but with occasional WOT episodes for onramps etc.(Dallas Traffic)
At light throttle, you are 100% on the IDLE circuit in a 914...
Barely touching the throttle to go 70MPH...
The needle adjustment is extremely critical...
Mine are just "cracked" perhaps 1/16>1/8 turn, which is the "wrong" way to set it up, but it has worked best for me.
I tried smaller idle jets to get the needle adjustment into the 1/4>2 turn range, but the car would run like ass.
I'm running 195/65-15 Michelin Pilots.
I am running a late bus distributor with the slop taken out of the springs, and the stops tweaked slightly... 12-15 BDTC initial, and 28 final... With working Vacuum advance, ported to all 4 throttle plates.
I got similar mileage without the vac advance wit 32 final mechanical, but the motor wanted less at WOT. Your motor will likely prefer 32.
My compression ratio is ~8.7:1, no gaskets on jugs or heads.
Addendum to Newtons first law:
zero vehicles on jackstands, square gets a fresh 090 and 1911, cabby gets a blower.
EZ3.6 Vanagon after that.(mounted, needs everything finished) then Creamsicle.
zero vehicles on jackstands, square gets a fresh 090 and 1911, cabby gets a blower.
EZ3.6 Vanagon after that.(mounted, needs everything finished) then Creamsicle.
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914fan
- Posts: 190
- Joined: Thu Aug 21, 2003 8:53 pm
I believe I am running a l-jet dist. I have 8 initial and 28 total advance.
Iidle is set to between 700 and 800 (digital advance gun with tach)
I do not have the vacume hooked up. I will have to try that.
My idle screws are turned 1.5 to 1.75 turns out.
I did not build the motor so I do not know the compression.
It is also running a web 73 (so I was told) hydro.
The motor was origanaly built with the fi. It died and I got carbs.
Here is a revised spec
40 IDFs
55 idle
135 mail
200 ac
F11 E tubes
and 32 or 28 chokes (I forget exactly but whatever is stock)
On a side note. I have not removed the chokes (start up enrichment on the side of the carb) I have found that when the car is warmed up and running if I open the chokes it will idle up a little and then die. I do not have a lot of expierence with carbs so I do not know if that is normal. I have not tried using the chokes durring startup.
On start up the motor will spin for a while before catching. (without pressing the pedal) If I pump the pedal the car takes longer to start, and will sometimes pop out the carbs. (to rich?)
Either way it takes a while (15 - 30 seconds) before I can get the rpms to go up. It will stall if I give it gas quickly but will SLOWLY climb if I apply a little throttle. After it has hit 3000 it will run fine and is happy. Kind of like you cant talk in the morning until you have cleared your throte. (Eh hem)
I want to say the throtle plates are turned in about 2 turns.
the syncrometer reads 6 on all carbs and idles at 700 - 800.
If I get the total ccs of the head by bringing it to TDC and filling the camber with oil through the spark plug hole. could I combine that with the bore and stroke to get the comp ratio? or is that not reliable?
Iidle is set to between 700 and 800 (digital advance gun with tach)
I do not have the vacume hooked up. I will have to try that.
My idle screws are turned 1.5 to 1.75 turns out.
I did not build the motor so I do not know the compression.
It is also running a web 73 (so I was told) hydro.
The motor was origanaly built with the fi. It died and I got carbs.
Here is a revised spec
40 IDFs
55 idle
135 mail
200 ac
F11 E tubes
and 32 or 28 chokes (I forget exactly but whatever is stock)
On a side note. I have not removed the chokes (start up enrichment on the side of the carb) I have found that when the car is warmed up and running if I open the chokes it will idle up a little and then die. I do not have a lot of expierence with carbs so I do not know if that is normal. I have not tried using the chokes durring startup.
On start up the motor will spin for a while before catching. (without pressing the pedal) If I pump the pedal the car takes longer to start, and will sometimes pop out the carbs. (to rich?)
Either way it takes a while (15 - 30 seconds) before I can get the rpms to go up. It will stall if I give it gas quickly but will SLOWLY climb if I apply a little throttle. After it has hit 3000 it will run fine and is happy. Kind of like you cant talk in the morning until you have cleared your throte. (Eh hem)
I want to say the throtle plates are turned in about 2 turns.
the syncrometer reads 6 on all carbs and idles at 700 - 800.
If I get the total ccs of the head by bringing it to TDC and filling the camber with oil through the spark plug hole. could I combine that with the bore and stroke to get the comp ratio? or is that not reliable?
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Piledriver
- Moderator
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- Joined: Sat Feb 16, 2002 12:01 am
I assume you have a 'Snail" flowmeter...
Anything Else IS Junk.
(Unless you have a hot wire setup by some bizarre chance)
I'd personally start by bumping your timing to 12/32, and hook up the vacuum advance.
Then I'd consider go UP one idle fuel jetsize, and regardless, really, REALLY make a fine point of getting the needle settings absolutely dead nuts on.
And run a fuel pressure regulator. I don't CARE what kind of pump you have. 2.5 PSI is a REAL good start with Webers.
It's nice that it happens to idle at stock RPMS, but as it is quite NOT a stock setup, the "optimal" value may vary. Bump it up a bit (along with the other changes) and see what works best---- It's (RPMS at idle) just a point of reference, but in reality, you MUST make a new one for YOUR setup.
And as to the CR, the plug isn't at the "top" of the chamber, so YMMV. I wouldn't personally trust it, or really care as long as a compression test reads close and it runs good/cool.
I disagree to a certain extent with the late great John Muir, but on one thing I DO concur--- Chokes Are Evil.
Anything Else IS Junk.
(Unless you have a hot wire setup by some bizarre chance)
I'd personally start by bumping your timing to 12/32, and hook up the vacuum advance.
Then I'd consider go UP one idle fuel jetsize, and regardless, really, REALLY make a fine point of getting the needle settings absolutely dead nuts on.
And run a fuel pressure regulator. I don't CARE what kind of pump you have. 2.5 PSI is a REAL good start with Webers.
It's nice that it happens to idle at stock RPMS, but as it is quite NOT a stock setup, the "optimal" value may vary. Bump it up a bit (along with the other changes) and see what works best---- It's (RPMS at idle) just a point of reference, but in reality, you MUST make a new one for YOUR setup.
And as to the CR, the plug isn't at the "top" of the chamber, so YMMV. I wouldn't personally trust it, or really care as long as a compression test reads close and it runs good/cool.
I disagree to a certain extent with the late great John Muir, but on one thing I DO concur--- Chokes Are Evil.
Addendum to Newtons first law:
zero vehicles on jackstands, square gets a fresh 090 and 1911, cabby gets a blower.
EZ3.6 Vanagon after that.(mounted, needs everything finished) then Creamsicle.
zero vehicles on jackstands, square gets a fresh 090 and 1911, cabby gets a blower.
EZ3.6 Vanagon after that.(mounted, needs everything finished) then Creamsicle.
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JohnConnolly
- Posts: 3336
- Joined: Thu Apr 13, 2000 12:01 am
your plugs are fouled because the jetting is way too rich. Try a 50 idle and 120 main. Change your plugs. Also, many people aren't aware that FI plugs are different then NA plugs, run NGK 5s (Bosch 8s) with carbs, FI had NGK 6 (Bosch 7). This is another common cause of plug fouling, and one that no carb kit supplier I know of (other then us) actually tells the customer.
John
Aircooled.Net Inc.
John
Aircooled.Net Inc.
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914fan
- Posts: 190
- Joined: Thu Aug 21, 2003 8:53 pm
Thanks for the replies.
I hooked up a temp for the start up chokes and the car started up on the first revolution. I am very strongly considering running a cable to the cab to operate the chokes on a permanent basis. I also hooked up the vac advance and it made a huge difference. I have driven another day on this tank and I hooked the advance well after 1/2 tank. The idle is smooth where it is and it took a while to get it there. I will play with it to see if it gets more smooth. I will also switch to the bosch 8 ( what is the exact plug number?) my next change. I tried running the 50 idles but the car pops and fires out the carb. With the 55 is has only done it 3 times as compared to at least 10 times a trip. I am actually thinking about 60s.
More questions...
what shoud the idle speed screws be turned in to? Max? Min?
Same for the idle jet screws?
Lastly when I removed the screws to the vac ports one of them had fuel in it. What would cause this? What should I look out for? Should I just blow out that port?
Thank you for the help.
I hooked up a temp for the start up chokes and the car started up on the first revolution. I am very strongly considering running a cable to the cab to operate the chokes on a permanent basis. I also hooked up the vac advance and it made a huge difference. I have driven another day on this tank and I hooked the advance well after 1/2 tank. The idle is smooth where it is and it took a while to get it there. I will play with it to see if it gets more smooth. I will also switch to the bosch 8 ( what is the exact plug number?) my next change. I tried running the 50 idles but the car pops and fires out the carb. With the 55 is has only done it 3 times as compared to at least 10 times a trip. I am actually thinking about 60s.
More questions...
what shoud the idle speed screws be turned in to? Max? Min?
Same for the idle jet screws?
Lastly when I removed the screws to the vac ports one of them had fuel in it. What would cause this? What should I look out for? Should I just blow out that port?
Thank you for the help.
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JohnConnolly
- Posts: 3336
- Joined: Thu Apr 13, 2000 12:01 am
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Piledriver
- Moderator
- Posts: 22879
- Joined: Sat Feb 16, 2002 12:01 am
Johns right about the plugs, I like Autolite AP63s, they seem "correct" in all my vehicles. (wasser, 2 T4s, one with big valves and bumpstick) and seem to last forever. They are projected core nose platinum plugs.
The screws hould be turned in to the RIGHT place, as decided by your MOTOR.
Redline Weber has some great tech articles that describe exactly how to do this.
If you're popping at ALL,your jets either too lean, screws in too far (1/8>2 turn is "acceptable") or you have a vacuum leak...
Bump your timing to 12/32. Do that second after changing the plugs.
Then look for vacuum leaks.
The screws hould be turned in to the RIGHT place, as decided by your MOTOR.
Redline Weber has some great tech articles that describe exactly how to do this.
If you're popping at ALL,your jets either too lean, screws in too far (1/8>2 turn is "acceptable") or you have a vacuum leak...
Bump your timing to 12/32. Do that second after changing the plugs.
Then look for vacuum leaks.
Addendum to Newtons first law:
zero vehicles on jackstands, square gets a fresh 090 and 1911, cabby gets a blower.
EZ3.6 Vanagon after that.(mounted, needs everything finished) then Creamsicle.
zero vehicles on jackstands, square gets a fresh 090 and 1911, cabby gets a blower.
EZ3.6 Vanagon after that.(mounted, needs everything finished) then Creamsicle.
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914fan
- Posts: 190
- Joined: Thu Aug 21, 2003 8:53 pm
I was asking about the screw positions just out of curosity. I figured that the closer to closed the buterflies are the more the carb is working correctly. What I meen is that the progression ports and all the fance engienering do dads that weber has figured out are working to thier full potential. I could be wrong. I have been before.
No mater what I will learn some more every time.
Lastly, what is the difference between the two plugs? Are the 8s hotter? Deeper?
No mater what I will learn some more every time.
Lastly, what is the difference between the two plugs? Are the 8s hotter? Deeper?
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JohnConnolly
- Posts: 3336
- Joined: Thu Apr 13, 2000 12:01 am
just a side note on plugs.
Denso, NGK, and Bosch, all use rolled threads, which are much easier on the threads in the head.
All the others (Champion, Autolite, Motorcraft, etc) use cut threads. These are much much more harsh on the threads in the heads. More often then not if I see used heads with these plugs in them, the heads are cracked or the plug threads stripped.
I'll bet you could take a poll and find my observations are on the mark.
The NA plugs are hotter then the FI plugs, and are better at preventing fouling.
John
Aircooled.Net Inc.
Denso, NGK, and Bosch, all use rolled threads, which are much easier on the threads in the head.
All the others (Champion, Autolite, Motorcraft, etc) use cut threads. These are much much more harsh on the threads in the heads. More often then not if I see used heads with these plugs in them, the heads are cracked or the plug threads stripped.
I'll bet you could take a poll and find my observations are on the mark.
The NA plugs are hotter then the FI plugs, and are better at preventing fouling.
John
Aircooled.Net Inc.
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Piledriver
- Moderator
- Posts: 22879
- Joined: Sat Feb 16, 2002 12:01 am
I think we are talking of different screws--- I was referring to the FUEL needles, on the sides of the carbs.
Addendum to Newtons first law:
zero vehicles on jackstands, square gets a fresh 090 and 1911, cabby gets a blower.
EZ3.6 Vanagon after that.(mounted, needs everything finished) then Creamsicle.
zero vehicles on jackstands, square gets a fresh 090 and 1911, cabby gets a blower.
EZ3.6 Vanagon after that.(mounted, needs everything finished) then Creamsicle.
-
914fan
- Posts: 190
- Joined: Thu Aug 21, 2003 8:53 pm
Thanks for the plug sugestion. Will the hotter plug cause a hotter head?
Yes I am using a "snail" syncrometer.
Screws clarafication:
The idle speed screws (side of carb)...
I would assume that the idle speed screws should be in as little as possible. This would cause the butterflies to be mostly closed thierby causing progression ports in the carb body to be fully used and make the carb more efiecient. At least I would assume. Having said that I am at about 1 1/2 - 2 turns in. I dont remember off the top of my head. With different jets I can get the car to idle and sync the carbd with the idle speed screws all the way in (butterflies more open) I know that is not correct. I guess my question is what range of turns in on the idle speed screws is most effiecient for the carb?
Idle Jet Volume Screws (base of carb)...
Same question here. With 55 jets in I am about 1 - 1 1/4 turns out. With 50 jets I was 2 turns out. Im guessing that with 60s I would be 3/4 turn out. The turns out are with carbs syncronised and turning them in and out to get the best idle on each cylinder. (per the CB book and everybody else I have spoken with) My question here again is that is the most effieient setting. This is basically valve and at some point it will be the more efficent. So where is the sweet spot.
In one of my erlier post I said I had been having problems with popping out the carb. That had been a chain reaction. I had to lean of a idle jet (50) and the popping out the carb was blowing out the gasket between the carb and head. That caused an even more lean condition and more popping. I was looking into a better gasket due to the small area for sealing at 1 and 11 O'clock between the two intake ports. That is the area where the factory shroud on a type 4 rubs away at the intake port. I still have occasional popping. But now it is at startup when I'm pumping the throtle to get it started / running. I have expierimented with the enrichment chokes and had great success. I am trying to figure out some cable system to use them. I do know that some people do not like them. I do not know why. Can some one give any reasons so I can make an informed decision?
Thank you all for your help so far.
Yes I am using a "snail" syncrometer.
Screws clarafication:
The idle speed screws (side of carb)...
I would assume that the idle speed screws should be in as little as possible. This would cause the butterflies to be mostly closed thierby causing progression ports in the carb body to be fully used and make the carb more efiecient. At least I would assume. Having said that I am at about 1 1/2 - 2 turns in. I dont remember off the top of my head. With different jets I can get the car to idle and sync the carbd with the idle speed screws all the way in (butterflies more open) I know that is not correct. I guess my question is what range of turns in on the idle speed screws is most effiecient for the carb?
Idle Jet Volume Screws (base of carb)...
Same question here. With 55 jets in I am about 1 - 1 1/4 turns out. With 50 jets I was 2 turns out. Im guessing that with 60s I would be 3/4 turn out. The turns out are with carbs syncronised and turning them in and out to get the best idle on each cylinder. (per the CB book and everybody else I have spoken with) My question here again is that is the most effieient setting. This is basically valve and at some point it will be the more efficent. So where is the sweet spot.
In one of my erlier post I said I had been having problems with popping out the carb. That had been a chain reaction. I had to lean of a idle jet (50) and the popping out the carb was blowing out the gasket between the carb and head. That caused an even more lean condition and more popping. I was looking into a better gasket due to the small area for sealing at 1 and 11 O'clock between the two intake ports. That is the area where the factory shroud on a type 4 rubs away at the intake port. I still have occasional popping. But now it is at startup when I'm pumping the throtle to get it started / running. I have expierimented with the enrichment chokes and had great success. I am trying to figure out some cable system to use them. I do know that some people do not like them. I do not know why. Can some one give any reasons so I can make an informed decision?
Thank you all for your help so far.