|
48 IDA help 3k rpm cut
i have a 48ida on a 12a street port and its stumbling out at 3000rpm on a regular basis its only good past half throttle let me know if you guys know anything
Thanks |
List your current settings.
The stumble is caused by incorrect emulsion tube and idle jet combinations. Read this thread: https://www.rx7club.com/1st-generation-specific-1979-1985-18/weber-emulsion-tubes-805950/ |
fuel jet 170
air jet 150 f11 emulsion tubes 250 needle valve Exactley what racing beat says and thanks for the thread but i was running the f7's and it had the same stumble my idle jets are 60/120 on the top 70 f10 ew i feel like my idles could be the problem but the cut is unbelible when slowly increasing on the throttle |
Forget what Racing Beat says, or anyone else for that matter. They can only give you a guestimate for what might work on your car. With a carburetor things like barometric pressure, altitude, air quality, temprature, port size, and compression all come into effict when tuning. For example I tuned my car at 65*F ambiant the other night and at idle it's almost exactly 13.8:1 AFR's, but in the heat of the day today it was 93*F It was idleing at 11.5-12:1 AFR's because of the thinning of the air with the heat.
First thing is get rid of the 120 idle jet holder and use a 100 jet holder. That should help a little. The problem is that a 48 IDA really is kind of small for a rotary and they like to be rich in the midrange. The ida gets really lean on transition from the idle circut to the main curcut which happenes right at 2500-3500 RPM. What you're experiancing is a lean surge. There isn't enough fuel put out at 3000 RPM by the idle circut to keep the engine running, and the e-tube is too restrictive making the main circut not come on until 3050 rpm, so the engine stumbles falls to 2950 then drives fine until it gets just past the limits of the idle circut and the main isn't on yet so it falls again and so on. From my tests and tuning throughout the years even with the 3rd progression hole the f-11 e-tube is way too lean on the transition and the lean stumble will never go away. Try f-3 or f-8 etubes and a 100 idle jet holder and it should go away. With the 120a/c I had to run 65idles and I would get about 14 MPG. When I switched to 100 a/c i could run 60 idles and I can get ablmost 17mpg if I stay out of it. Keep in mind I made 190 rwhp on this engine and it's my daily driver. |
Also, You need to check and make sure your float is set correctly. If it's off by 1mm it can screw things up BAD. The general rule is for every 1mm of adjustment you change when the main circut comes on for 1000RPM
|
Originally Posted by Hyper4mance2k
(Post 9385797)
Also, You need to check and make sure your float is set correctly. If it's off by 1mm it can screw things up BAD. The general rule is for every 1mm of adjustment you change when the main circut comes on for 1000RPM
|
I don't respond to technical PM's. Post it here for others to learn from.
|
Originally Posted by fb-elli
hey okay so im going to try some f8 e tube and 100 jet holder do you find that the adjuster screws on the carbs do anything inbetween low and high i cant telll a difference at all its always burning rich and stubling from 2000 basicaly to just over 3000rpm any other tips on the 48 other then the float bowl level?
thanks in advance for the help F8's are really rich. More suited to a bridgeported 13b that gets street driven. Like I said before get f2's or f3's. You can get them at http://www.webercarbsdirect.com/ for $7 each... The idle screws only effect idle. If you have them turned out more than 1.5 turns your idle circut is too lean. |
Originally Posted by Hyper4mance2k
(Post 9388042)
This was his PM
F8's are really rich. More suited to a bridgeported 13b that gets street driven. Like I said before get f2's or f3's. You can get them at http://www.webercarbsdirect.com/ for $7 each... The idle screws only effect idle. If you have them turned out more than 1.5 turns your idle circut is too lean. the idle screws will make the car run lean if turned out past 1.5 from bottuming out? ive noticed my car bucking at low throttle at a cruise its before 3000 rpm have you ever encounters a problem like this before beacuse of the f11 e tubes? thanks once again |
Turning out the idle mixture screws makes the idle richer. Turning them in leans it out. What Hyper is saying is that you shouldn't have to turn them out more than 1.5 turns to get it to idle well. If you do, it means your idle circuit is too lean for your engine.
The bucking is probably a lean surge, also indicating that your idle circuit is too lean. |
It also indicates that his main circut is coming on too late. F-11's suck... I have answered all your questions. Reread the thread man! The whole thing not just the parts you like and you'll get your car running well. read the Link %7C posted as well. The WHOLE THREAD!
|
I'll try some f2s and post how it works out
|
that depends on the size. larger idle jet are less than 1 full turn.
Originally Posted by PercentSevenC
(Post 9388272)
Turning out the idle mixture screws makes the idle richer. Turning them in leans it out. What Hyper is saying is that you shouldn't have to turn them out more than 1.5 turns to get it to idle well. If you do, it means your idle circuit is too lean for your engine.
The bucking is probably a lean surge, also indicating that your idle circuit is too lean. |
Put a bigger main jet and should fix the problem, it stumbles because there is a lean spot...good luck
|
Originally Posted by rotorholic
(Post 9393628)
Put a bigger main jet and should fix the problem, it stumbles because there is a lean spot...good luck
you're making it too easy for them. Give them a hard time so they wont forget :lol::lol::lol::lol: |
Originally Posted by Hyper4mance2k
(Post 9388042)
This was his PM
F8's are really rich. More suited to a bridgeported 13b that gets street driven. Like I said before get f2's or f3's. You can get them at http://www.webercarbsdirect.com/ for $7 each... The idle screws only effect idle. If you have them turned out more than 1.5 turns your idle circut is too lean. |
Originally Posted by ultimatejay
(Post 9393636)
The lower the F# the richer the tube. F2 Emulsion tubes are used for alcohol, so the F8 emulsion tube would not be richer.
did you read my prior post??? I said, give them a hard time. I feel evil tonight :lol::lol::lol::lol: |
Originally Posted by wackyracer
(Post 9393640)
did you read my prior post??? I said, give them a hard time. I feel evil tonight :lol::lol::lol::lol:
|
Originally Posted by wackyracer
(Post 9393633)
sir,
you're making it too easy for them. Give them a hard time so they wont forget :lol::lol::lol::lol: |
WARNING RANT IN PROGRESS!!
Originally Posted by ultimatejay
(Post 9393636)
The lower the F# the richer the tube. F2 Emulsion tubes are used for alcohol, so the F8 emulsion tube would not be richer.
These are the exact specifications on which the e-tubes are made.
Originally Posted by rotorholic
(Post 9393628)
Put a bigger main jet and should fix the problem, it stumbles because there is a lean spot...good luck
Remember as air flows across the aux venturi the vacuum in the main circut fuel well grows exponentially. That's why there is an air bleed and a e-tube. They act as nothing more than a brake for the fuel flow. without them the fuel drawn into the engine would also increase exponentially as rpm's rose. The air bleed, or air jet meters, how much air is allowed into the main circut and drawn into the carburetor leaning out the fuel mixture. The emulsion tube emusifies the air and fuel together. Where the holes are drilled into the tube decide on what RPM the amount of emulsification accure. The lower the holes are in the e-tube the higher in the RPM band the mixture is effected. As i said before his problem is that the idle circut is running at it's maximum capasity and the engine is demanding more fuel at say 2500 rpm. if the main circut doesn't start adding fuel until 3000 rpm like the f-11 do then he will have a lean stumbe from 2500-3000 rpm. so if you just add a bigger main jet you're not solving your problem all you're doing is adding more fuel at 3000 RPm and not solving the issue of the lack of fuel that the engine is demanding at 2500 rpm. There are two ways around this either extend the idle circuts ability to supply fuel by running a smaller air bleed or bigger idle jet. the smaller air bleed is a great idea as it will only efect the top end of the idle circut. so he puts in the 100 idle jet holder and now his car can run to 2700 rpm before the idle circut tops out. there's still a lean spot from 2700-3000 rpm. So you could add a larger idle jet, but that's only going to richen up the bottom of the idle circut from idle to 2000 rpm or so. so much so that it'll idle like shit and smell terrible and waste a shit ton of gas. And, as I said before if he just plugs in a larger main jet he's only making 3000 rpm to 5500 rpm richer, not at all solving the lean area from 2500-3000 rpm, so he needs to change his e-tube to get the main circut started sooner. |
Originally Posted by Hyper4mance2k
(Post 9395352)
WARNING RANT IN PROGRESS!!
that's not exactly true. Go read my e-tube thread. The placement and the size of the holes in the tube decide how rich/lean the tube is. There is almost no rhyme or reason to webers e-tube numbering system. The f-3 etube is drilled exactly the same as the f-11. the only difference is it is thinner and therefore has a larger fuel well inside the main circut chamber allowing less of a pressure drop across the aux venturi before the main circut starts. in other words the car will run almost the same AFR's as an f-11but the main circut will start lower in the rpm band. look at weber's charts listed here: https://www.rx7club.com/showpost.php...4&postcount=24 These are the exact specifications on which the e-tubes are made. Not at all true. If you put a larger main jet in you will fatten up the bottom end opf the main circut, but it doesn't change anything about where the main circut starts, and you will still have the same stumble, and you'll get shitier gas mileage. I have done thousnads of experiaments and testing on this. In direct compairison the f-7 tubes I will cruise at 10.8: afrs where as with the f-3's my wideband says I'm at a healthy 13.5:1. In fact the f7 & f8 tubes are much richer than the f2 or f3 based on the arrangement and size of the holes in the tube. Remember the 48 IDA was designed to work with 36mm Chokes. Once you go any bigger than that you are out flowing the design of the IDA. Realistically 2 48IDA's with 36mm chokes would out flow a 58IDA once properly tuned, and drive as well as the stock nikki. That's why we have to go way out of the tuning norm for using just one on a rotary. Remember as air flows across the aux venturi the vacuum in the main circut fuel well grows exponentially. That's why there is an air bleed and a e-tube. They act as nothing more than a brake for the fuel flow. without them the fuel drawn into the engine would also increase exponentially as rpm's rose. The air bleed, or air jet meters, how much air is allowed into the main circut and drawn into the carburetor leaning out the fuel mixture. The emulsion tube emusifies the air and fuel together. Where the holes are drilled into the tube decide on what RPM the amount of emulsification accure. The lower the holes are in the e-tube the higher in the RPM band the mixture is effected. As i said before his problem is that the idle circut is running at it's maximum capasity and the engine is demanding more fuel at say 2500 rpm. if the main circut doesn't start adding fuel until 3000 rpm like the f-11 do then he will have a lean stumbe from 2500-3000 rpm. so if you just add a bigger main jet you're not solving your problem all you're doing is adding more fuel at 3000 RPm and not solving the issue of the lack of fuel that the engine is demanding at 2500 rpm. There are two ways around this either extend the idle circuts ability to supply fuel by running a smaller air bleed or bigger idle jet. the smaller air bleed is a great idea as it will only efect the top end of the idle circut. so he puts in the 100 idle jet holder and now his car can run to 2700 rpm before the idle circut tops out. there's still a lean spot from 2700-3000 rpm. So you could add a larger idle jet, but that's only going to richen up the bottom of the idle circut from idle to 2000 rpm or so. so much so that it'll idle like shit and smell terrible and waste a shit ton of gas. And, as I said before if he just plugs in a larger main jet he's only making 3000 rpm to 5500 rpm richer, not at all solving the lean area from 2500-3000 rpm, so he needs to change his e-tube to get the main circut started sooner. |
oh god, just give us a summary. too much reading is not good for our health and you make life too complicated :lol::lol::lol::lol:
and yes, I agree with Jose, we want to see your time slip. :lol::lol::lol::lol:
Originally Posted by Hyper4mance2k
(Post 9395352)
WARNING RANT IN PROGRESS!!
that's not exactly true. Go read my e-tube thread. The placement and the size of the holes in the tube decide how rich/lean the tube is. There is almost no rhyme or reason to webers e-tube numbering system. The f-3 etube is drilled exactly the same as the f-11. the only difference is it is thinner and therefore has a larger fuel well inside the main circut chamber allowing less of a pressure drop across the aux venturi before the main circut starts. in other words the car will run almost the same AFR's as an f-11but the main circut will start lower in the rpm band. look at weber's charts listed here: https://www.rx7club.com/showpost.php...4&postcount=24 These are the exact specifications on which the e-tubes are made. Not at all true. If you put a larger main jet in you will fatten up the bottom end opf the main circut, but it doesn't change anything about where the main circut starts, and you will still have the same stumble, and you'll get shitier gas mileage. I have done thousnads of experiaments and testing on this. In direct compairison the f-7 tubes I will cruise at 10.8: afrs where as with the f-3's my wideband says I'm at a healthy 13.5:1. In fact the f7 & f8 tubes are much richer than the f2 or f3 based on the arrangement and size of the holes in the tube. Remember the 48 IDA was designed to work with 36mm Chokes. Once you go any bigger than that you are out flowing the design of the IDA. Realistically 2 48IDA's with 36mm chokes would out flow a 58IDA once properly tuned, and drive as well as the stock nikki. That's why we have to go way out of the tuning norm for using just one on a rotary. Remember as air flows across the aux venturi the vacuum in the main circut fuel well grows exponentially. That's why there is an air bleed and a e-tube. They act as nothing more than a brake for the fuel flow. without them the fuel drawn into the engine would also increase exponentially as rpm's rose. The air bleed, or air jet meters, how much air is allowed into the main circut and drawn into the carburetor leaning out the fuel mixture. The emulsion tube emusifies the air and fuel together. Where the holes are drilled into the tube decide on what RPM the amount of emulsification accure. The lower the holes are in the e-tube the higher in the RPM band the mixture is effected. As i said before his problem is that the idle circut is running at it's maximum capasity and the engine is demanding more fuel at say 2500 rpm. if the main circut doesn't start adding fuel until 3000 rpm like the f-11 do then he will have a lean stumbe from 2500-3000 rpm. so if you just add a bigger main jet you're not solving your problem all you're doing is adding more fuel at 3000 RPm and not solving the issue of the lack of fuel that the engine is demanding at 2500 rpm. There are two ways around this either extend the idle circuts ability to supply fuel by running a smaller air bleed or bigger idle jet. the smaller air bleed is a great idea as it will only efect the top end of the idle circut. so he puts in the 100 idle jet holder and now his car can run to 2700 rpm before the idle circut tops out. there's still a lean spot from 2700-3000 rpm. So you could add a larger idle jet, but that's only going to richen up the bottom of the idle circut from idle to 2000 rpm or so. so much so that it'll idle like shit and smell terrible and waste a shit ton of gas. And, as I said before if he just plugs in a larger main jet he's only making 3000 rpm to 5500 rpm richer, not at all solving the lean area from 2500-3000 rpm, so he needs to change his e-tube to get the main circut started sooner. |
No time slip as the last time I went to the track I snapped my out put shaft in half and I'm tired of swapping trannies. Gsl-SE 13b with a very small street port.
here is the 1st dyno sheets. I had to back up my 189whp cause a bunch of internet race car drivers didn't believe my numbers. so %7c came out and taped the runs. I backed up 189.6 with 190.5 I'm an autoXer not a drag racer. Why pay $40 for 3 14 second runs when you can pay $25 for 5 50-70 second runs with turns. Plus last time we got about an hour of fun runs. fawk drag racing... http://www.youtube.com/watch?v=U0vbPTuvCzs https://www.rx7club.com/attachment.p...1&d=1236027914 |
snapped my out put shaft in half with 144 Torque?
Originally Posted by Hyper4mance2k
(Post 9396196)
No time slip as the last time I went to the track I snapped my out put shaft in half and I'm tired of swapping trannies. Gsl-SE 13b with a very small street port.
here is the 1st dyno sheets. I had to back up my 189whp cause a bunch of internet race car drivers didn't believe my numbers. so %7c came out and taped the runs. I backed up 189.6 with 190.5 I'm an autoXer not a drag racer. Why pay $40 for 3 14 second runs when you can pay $25 for 5 50-70 second runs with turns. Plus last time we got about an hour of fun runs. fawk drag racing... http://www.youtube.com/watch?v=U0vbPTuvCzs https://www.rx7club.com/attachment.p...1&d=1236027914 |
I ran a 14.2 when I was making 140whp. i haven't completed a run at the drag strip since... last time I went the output shaft broke on the first run. that was about a year ago and the time I went drag racing before that was 2001 maybe. I'm not some kid preending I know what I'm talking about. I come from a family of rotards, I'm fucking Puerto Rican for gods sake. what else do we do, and I'm 27 y/o and I've been building these cars with my family my whole life. Get the fuck over yourself. FYI half those "how to tune a weber" books give the shitty advise you have been giving. p.s. fuck off for questioning my integrity. there are at least 20 people on this forum who have had my output shaft in thier hand I keep it in the glove box.
|
| All times are GMT -5. The time now is 03:17 PM. |
© 2024 MH Sub I, LLC dba Internet Brands