Engine Tuning tips from you motor experts
02-09-2009, 07:43 AM
#1
Engine Tuning tips from you motor experts
Hi, I am having some trouble with my engine (RB C6BB7T) and plan on starting over from scratch to retune it. It still has good compression, etc, but the tune has just slowly gotten way off. In doing this, I came accross a couple fundamental questions regarding motor setup that I was not sure the answer.
1) Idle adjustment, normally is a 0.6-0.8mm idle gap, but, is this with the restrictor in or out? So, I have a yellow 7.5mm restrictor in my motor, should I set the idle gap so that I can see it even with the restrictor in, or remove the restictor and set it. If I remove the restrictor, set the idle gap, and re-insert the restrictor then I most probably will not see the gap at all with the restrictor in, correct?
2) Setting Full throttle EPA on the throttle servo. Again, question is related to the restrictor. Without the restrictor, full throttle is when the carb barrel pulls to the edge of the opening in the carb, which is normally about 1.0 - 1.5mm from the carb barrel being pulled all the way out. When inserting the restrictor, is full throttle now when the carb barrel gets to the edge of the restrictor?
With these 2 things, means that if I go to a smaller restrictor, I should change the idle gap and full throttle epa before retuning the motor.
Curious, as to get a proper tune on a motor for both power and fuel mileage, these must be set correctly first. I checked with a couple local guys and they were not sure. I know this may be tuning secret from the experts, but just looking for a little help.
1) Idle adjustment, normally is a 0.6-0.8mm idle gap, but, is this with the restrictor in or out? So, I have a yellow 7.5mm restrictor in my motor, should I set the idle gap so that I can see it even with the restrictor in, or remove the restictor and set it. If I remove the restrictor, set the idle gap, and re-insert the restrictor then I most probably will not see the gap at all with the restrictor in, correct?
2) Setting Full throttle EPA on the throttle servo. Again, question is related to the restrictor. Without the restrictor, full throttle is when the carb barrel pulls to the edge of the opening in the carb, which is normally about 1.0 - 1.5mm from the carb barrel being pulled all the way out. When inserting the restrictor, is full throttle now when the carb barrel gets to the edge of the restrictor?
With these 2 things, means that if I go to a smaller restrictor, I should change the idle gap and full throttle epa before retuning the motor.
Curious, as to get a proper tune on a motor for both power and fuel mileage, these must be set correctly first. I checked with a couple local guys and they were not sure. I know this may be tuning secret from the experts, but just looking for a little help.
02-09-2009, 09:46 AM
#2
Tech Master
1) In my nova the idle gap is set without the restricter in.
2) Full throttle epa should be set so that when you grab the linkage you cant pull it any further than what the servo can when at full throttle. Make sure that when you set this your servo isn't pulling on the the motor (trying to pull beyond full throttle) as this will blow your servo.
Change idle accordingly if your idle changes when changing restricter don't touch your epa.
2) Full throttle epa should be set so that when you grab the linkage you cant pull it any further than what the servo can when at full throttle. Make sure that when you set this your servo isn't pulling on the the motor (trying to pull beyond full throttle) as this will blow your servo.
Change idle accordingly if your idle changes when changing restricter don't touch your epa.
02-09-2009, 10:05 AM
#3
Full throttle should be set so that the slide goes just past the carb insert. By doing this you have a extra room for chassis/engine flex putting less strain on the servo. Having it at full throw gains nothing. If you change the restrictor you should change the EPA.
Idle is a pain to explain on the internet. Get it so that the idle is at a low enough rev but not so low it sounds like it's really bogging and is going to cut. LSN i set so that once i give the throttle a few blasts (usually 3 after one another) and let it settle for 10-15secs i can pull it full open so it doesn't lean bog. If it lean bogs i richen it a 8th. After that i listen to the idle and go tune on track. Has worked for me very well. HSN i set before i go on track to have a decent smoke (always on the rich side) then tune it on track.
Idle is a pain to explain on the internet. Get it so that the idle is at a low enough rev but not so low it sounds like it's really bogging and is going to cut. LSN i set so that once i give the throttle a few blasts (usually 3 after one another) and let it settle for 10-15secs i can pull it full open so it doesn't lean bog. If it lean bogs i richen it a 8th. After that i listen to the idle and go tune on track. Has worked for me very well. HSN i set before i go on track to have a decent smoke (always on the rich side) then tune it on track.
02-09-2009, 10:26 AM
#4
That is what I was guessing, that the idle gap is set with the restrictor removed and that full throttle EPA was set to the edge of the restrictor with the restrictor in.
02-09-2009, 03:25 PM
#5
Actually, you set your throttle EPA to full stroke of the carb movement, then back the EPA off so when the servo opens full throttle, the carb linkage can be pulled further by .5mm-.8mm (gives some room for chassis flex so your not tugging on the carb fully)
As for base idle gap, its generally set with the restrictor out. The restrictor will not make the idle gap smaller just because you don't see it under the restrictor. RB states .8mm gap for a .21 (can be .5mm-1.0mm in most cases)
Overall the gap is your base setting, actual engine tuning will set the gap, mainly the LSN mixture, so keep this in mind. For a new engine running during break-in, the gap will be on the large side. As the engine is tuned more after break-in, the LSN will be leaned to gain power and most likely the base air gap will have to be closed to keep the idle from going too high.
As for base idle gap, its generally set with the restrictor out. The restrictor will not make the idle gap smaller just because you don't see it under the restrictor. RB states .8mm gap for a .21 (can be .5mm-1.0mm in most cases)
Overall the gap is your base setting, actual engine tuning will set the gap, mainly the LSN mixture, so keep this in mind. For a new engine running during break-in, the gap will be on the large side. As the engine is tuned more after break-in, the LSN will be leaned to gain power and most likely the base air gap will have to be closed to keep the idle from going too high.
02-09-2009, 03:48 PM
#6
All adjustments need to be made with the restrictor you plan to use. Going to a smaller restrictor is going to make your idle gap smaller. It won't hurt to leave the EPA though as more throw past the opening does not effect anything. And it goes without saying that restricting the air intake will change your tune as well.
02-09-2009, 03:53 PM
#7
Actually I should say that it IS smart to set your EPA so that it ONLY throws as far as needed. But any more wont hurt you unless it is to the point that you strain the carb.
02-09-2009, 04:12 PM
#9
Could be your idle gap is too large. It could make you richen it up by mistake to try and bring the idle down.
02-09-2009, 05:03 PM
#10
all engines do not tune the same 
when breaking in an engine , do not tune too lean on the lsn . once it is past break in (2 gallons or so) then set your hsn to be the control valve for the engines fuel intake , you want it to hit the powerband but not over rev
too rich on the lsn and too lean on top will drastically reduce the life span of the engine . most run on when coming off throttle is usually too rich on lsn and too big of a gap to compensate on the slide barrel (idle). if it runs on and makes a tingy sound that is too lean!!! 
fix it
proper race tune : lsn as lean as possible(without lean bog) , idle as low as possible , use hsn to set top end before final adj. on lsn . 6 foot trail of smoke at least , nice crisp snap off of the bottom end (clutch depending) . remember to clutch your engine appropriately.
hope this helps ,
monty
when breaking in an engine , do not tune too lean on the lsn . once it is past break in (2 gallons or so) then set your hsn to be the control valve for the engines fuel intake , you want it to hit the powerband but not over rev
too rich on the lsn and too lean on top will drastically reduce the life span of the engine . most run on when coming off throttle is usually too rich on lsn and too big of a gap to compensate on the slide barrel (idle). if it runs on and makes a tingy sound that is too lean!!! fix it proper race tune : lsn as lean as possible(without lean bog) , idle as low as possible , use hsn to set top end before final adj. on lsn . 6 foot trail of smoke at least , nice crisp snap off of the bottom end (clutch depending) . remember to clutch your engine appropriately
. hope this helps ,
monty
02-10-2009, 11:04 PM
#12
One more thing...there are a few carbs around that the slider(LSN) won't exit completely from the barrel that sprays the fuel if you just set the EPA to the opening of the venturi...SO set EPA and idle gap with no venturi in and make sure as "ezveedub" said to leave 0.5-1mm free play on the throttle linkage when you are full throttle, for any chassis flex or engine moving.
02-11-2009, 03:32 PM
#13
One more thing...there are a few carbs around that the slider(LSN) won't exit completely from the barrel that sprays the fuel if you just set the EPA to the opening of the venturi...SO set EPA and idle gap with no venturi in and make sure as "ezveedub" said to leave 0.5-1mm free play on the throttle linkage when you are full throttle, for any chassis flex or engine moving.
02-15-2009, 07:30 PM
#14
all engines do not tune the same
when breaking in an engine , do not tune too lean on the lsn . once it is past break in (2 gallons or so) then set your hsn to be the control valve for the engines fuel intake , you want it to hit the powerband but not over rev too rich on the lsn and too lean on top will drastically reduce the life span of the engine . most run on when coming off throttle is usually too rich on lsn and too big of a gap to compensate on the slide barrel (idle). if it runs on and makes a tingy sound that is too lean!!! fix it
proper race tune : lsn as lean as possible(without lean bog) , idle as low as possible , use hsn to set top end before final adj. on lsn . 6 foot trail of smoke at least , nice crisp snap off of the bottom end (clutch depending) . remember to clutch your engine appropriately.
hope this helps ,
monty
when breaking in an engine , do not tune too lean on the lsn . once it is past break in (2 gallons or so) then set your hsn to be the control valve for the engines fuel intake , you want it to hit the powerband but not over rev
too rich on the lsn and too lean on top will drastically reduce the life span of the engine . most run on when coming off throttle is usually too rich on lsn and too big of a gap to compensate on the slide barrel (idle). if it runs on and makes a tingy sound that is too lean!!! fix it proper race tune : lsn as lean as possible(without lean bog) , idle as low as possible , use hsn to set top end before final adj. on lsn . 6 foot trail of smoke at least , nice crisp snap off of the bottom end (clutch depending) . remember to clutch your engine appropriately
. hope this helps ,
monty
Currently Active Users Viewing This Thread: 1 (0 members and 1 guests)
