DaveInDenver
Middle Income Semi-Redneck
Jim C is basically the universally acknowledged F/2F carb expert.rwb0481 said:
Jim Chenoweth
fj40jim@aol.com
TLC Performance
Lancaster, OH
(740) 862-2604
TLCA# 1914
FJ60 tuned for mpgs.
- Thread starter Sloan
- Start date
Jim Chenoweth
fj40jim@aol.com
TLC Performance
Lancaster, OH
(740) 862-2604
TLCA# 1914
Grim Reaper
Expedition Leader
I don't get the loss of power.
When I tune a carb I always set the base mix and idle with a vacuum gage and tach. The premise is the higher the vacuum the more efficient the burn. Then a 1/8 turn lean on the idle jet. It should NOT hurt MPG.
From there its a matter of jetting it to the elevation. Little lower in the float bowl will lean it out some but again unless its REAL low on the float bowl to the point of ping it should not hurt performance.
Lastly is a properly working EGR system. EGR is used in conjunction with a lean fuel mix to prevent ping at steady cruise. When maintaining speed you do not need to the full potential of the engines power.
What happens it the fuel mix will go lean at at steady cruise to save fuel. When that happens cylinder temp rises as the mixture exceeds the ideal 14.7:1 air to fuel mixture. That improves economy BUT it can melt the cat, valves, piston and of course will start pinging to let you know these things are happening.
The EGR meters in some exhaust to remove Oxygen from the combustion chamber and gets the fuel mixture back to the ideal 14.7:1 and lower the combustion temp while actually using less fuel since the motor does not needs full power to maintain speed. As soon as the vacuum drops from acceleration or hitting a hill causing the RMP to drop the metering rods raise adding fuel and the EGR closes adding Oxygen.
Knowing this I can't understand the loss of power. The more efficient it runs the better the power. Did he retard the timing? That causes more time for the fuel to burn if its running rich. Under cruise conditions it would improve economy but hurt acceleration. Seems to me though to be a band-aid fix when making it a little more lean would fix the problem and allow the timing to be set so as not to loose acceleration performance.
When I tune a carb I always set the base mix and idle with a vacuum gage and tach. The premise is the higher the vacuum the more efficient the burn. Then a 1/8 turn lean on the idle jet. It should NOT hurt MPG.
From there its a matter of jetting it to the elevation. Little lower in the float bowl will lean it out some but again unless its REAL low on the float bowl to the point of ping it should not hurt performance.
Lastly is a properly working EGR system. EGR is used in conjunction with a lean fuel mix to prevent ping at steady cruise. When maintaining speed you do not need to the full potential of the engines power.
What happens it the fuel mix will go lean at at steady cruise to save fuel. When that happens cylinder temp rises as the mixture exceeds the ideal 14.7:1 air to fuel mixture. That improves economy BUT it can melt the cat, valves, piston and of course will start pinging to let you know these things are happening.
The EGR meters in some exhaust to remove Oxygen from the combustion chamber and gets the fuel mixture back to the ideal 14.7:1 and lower the combustion temp while actually using less fuel since the motor does not needs full power to maintain speed. As soon as the vacuum drops from acceleration or hitting a hill causing the RMP to drop the metering rods raise adding fuel and the EGR closes adding Oxygen.
Knowing this I can't understand the loss of power. The more efficient it runs the better the power. Did he retard the timing? That causes more time for the fuel to burn if its running rich. Under cruise conditions it would improve economy but hurt acceleration. Seems to me though to be a band-aid fix when making it a little more lean would fix the problem and allow the timing to be set so as not to loose acceleration performance.
Sloan
Explorer
I have some carb issues that we are going to address tomorrow. I also think that when we tuned it last week that it is too retarded now which causes the power to drop off when the rpms hit 2,000. I just took a DUI distributor off and reinstalled the stock one so I was expecting a shakedown period.
Grim Reaper
Expedition Leader
DUI is a good product as long as the advance is set up correctly. That might be part of the problem.Sloan said:
Are you sure your speedo/odometer is not off? Larger tires make it run slow.
Sloan
Explorer
Grim Reaper said:
I got popped by the smog inspector for non spec. equipment.
If my bud can't sort it out it might be time to go see a professional mechanic. 
The speedo is definitely off with the stock gearing and the 33s but I am only losing 1 mile for every 20 actual driven. I arrived at this figure because when I drove my Tacoma to work and parked in my spot it was exactly 20 miles, with the 60 it is exactly 19. I'm picking up a 4.11 third tomorrow so once the tuning gets sorted out I'l check out what sort of difference the gearing makes.
Sloan
Explorer
The diaphragm for the secondary was very crispy and hence the secondary was kicking in little or not at all. She pulls really well now but she still has a big power drop off at 55 mph. I think it might be time to go see teh boys at TLC for a proper tune up. I wish I had gotten a chance to run the DUI with the secondaries actually working.
Grim Reaper
Expedition Leader
Well it is a big barn door going down the road. 55 may be the point where it just runs out of motor with the current gearing. When it was built the Max Speed limit was 55.......
That's 5% error on the speedo and chances are it wasn't accurate to begin with. 5% is going to be about 3-4mph at 60mph so its going a little faster then you think. Got a GPS? next long ride see whats its really doing.
Heavy rims and tires doesn't help. Lift doesn't help.
Gearing would help with the upper end if you get it back to its stock RPM to speed.
Pulling anything off that may create wind drag like roof racks would help also.
That's 5% error on the speedo and chances are it wasn't accurate to begin with. 5% is going to be about 3-4mph at 60mph so its going a little faster then you think. Got a GPS? next long ride see whats its really doing.
Heavy rims and tires doesn't help. Lift doesn't help.
Gearing would help with the upper end if you get it back to its stock RPM to speed.
Pulling anything off that may create wind drag like roof racks would help also.
Sloan
Explorer
Big Barn Door!?!?!?!? I have to admit with the new power steering and the carb working better that thing it drives nice. I have to admit that on a flat she can get up to 75 which no FJ60 has any business in that neighborhood. I have been thinking that with her as a daily driver that maybe the bullbar, winch and rear Kaymar bumper should come off. I remember reading somewhere that every 100 pounds added reduces the mpgs by 2%.
I have to admit with the new power steering and the carb working better that thing it drives nice. I have to admit that on a flat she can get up to 75 which no FJ60 has any business in that neighborhood. I have been thinking that with her as a daily driver that maybe the bullbar, winch and rear Kaymar bumper should come off. I remember reading somewhere that every 100 pounds added reduces the mpgs by 2%.
Last edited:
kellymoe
Expedition Leader
Sloan said:
That is good to remember. My truck is filled with crap right now. Since the crewcab has a shell I tend to just throw stuff in there and forget about it. I probably have a few hundred pounds of camping gear in there right now that I need to put away. Thanks for the reminder.
BTW. did you decide on the move?
hks3sgte
César Gómez
kcowyo said:So do the 60's have a low fuel warning light?
I was running low on gas last night and wondering if the 60 would warn me before running out of gas. But I chickened out on finding out the hard way that it doesn't and filled up for $3.35 a gallon.
No, it doesn't have a warning light. As a matter of fact, the 60 doesn't have many lights at all. No pesky "check engine" light, or "low fuel" light. You know, how cars SHOULD be!
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