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the idle jets are probably ok, although it is worth going through the process. generally its best to start with idle and work your way up. if you have a place with no traffic, put it back together without the main jet stack and go drive. you will only have power until about 25% throttle, so keep that in mind.
doing this the carb will be only running on the idle jet stack. the next test is to put the main stack back and put it in about 4th or 5th (an rpm lower than the stumble), and floor it. if you have everything right it'll go, if its wrong it will run on the accel pump and then either stop running or have a delay and eventually go.
these two tests tell you where the idle circuit works, and where the main circuit works, and once you know that its easy to make changes. the F11 e tube is out to lunch, but you could probably tune around it. the E tubes go by cylinder size, and the 13B wants an F7 or F8 (can't find the damn chart).
once its in the ball park you can try different air correctors, smaller = main coming on sooner. i've been meaning to 3rd print some blank ones, and you could just drill it out until the car ran right, measure it and order the one you need
oh i get my stuff from here https://www.piercemanifolds.com/default.asp they have a ton of stuff in stock, and they are local to me so i get next day service, which is cool.
OK here comes the report and its a good news. First this is what jets and e tubes I have in the car at the moment:
Main jet: .200
Air correction: .180
Idle jets: 65F9
e tubes: F11
I ordered a set of tubes and jets: .180 and .170 main, .170 and .160 air correction and F7 e tubes. I also checked the mixture screws and they were 1/2 turn out. I set them to 1 turn out because I know the car was running too rich.
Now driving test. After taking main jets out, the idle circuit goes to about 3500 rpm and would not go further in any gear. After I put back the main jets the car starting working better. I can get to 5000 rpm in 3rd and I could floor it in 4th and 5th and it would still accelerate. In other words the car drives more like it should with current jets and e tubes. In fact it probably never ran better. But I am sure it should run even better, so with the new jets and e tubes I will do another test and report back. Th AFG was varying between 10 and 16. I cannot explain why the car now drives so much better, pass 3000 rpm with no sweat. I will upload a driving video to youtube and post here. Thank you all but specially j9, you rock
Screwing out the idle mixture from 1/2turn to 1 turn would make the idle richer, not leaner.
It is important to know on which rpm ranges the AFR are showing 10 and when they are showing 16.
16 - slightly lean - on the idle circuit while cruising is OK, not on the main circuit on WOT.
10 is way too rich, regardless of where it happens.
Last edited by Mivroum; Jun 10, 2020 at 03:25 AM.
Reason: spelling mistakes
OK here comes the report and its a good news. First this is what jets and e tubes I have in the car at the moment:
Main jet: .200
Air correction: .180
Idle jets: 65F9
e tubes: F11
I ordered a set of tubes and jets: .180 and .170 main, .170 and .160 air correction and F7 e tubes. I also checked the mixture screws and they were 1/2 turn out. I set them to 1 turn out because I know the car was running too rich.
Now driving test. After taking main jets out, the idle circuit goes to about 3500 rpm and would not go further in any gear. After I put back the main jets the car starting working better. I can get to 5000 rpm in 3rd and I could floor it in 4th and 5th and it would still accelerate. In other words the car drives more like it should with current jets and e tubes. In fact it probably never ran better. But I am sure it should run even better, so with the new jets and e tubes I will do another test and report back. Th AFG was varying between 10 and 16. I cannot explain why the car now drives so much better, pass 3000 rpm with no sweat. I will upload a driving video to youtube and post here. Thank you all but specially j9, you rock
sweet! i went through this a few years ago and found a really good paper by a guy called Keith Francks, its a really good step by step way to tune the carb, we start with the float level, and then idle and wor our way up, and at the end you know what does what, and the car runs great, i'll post it.
for AFR's we can shoot for about 12-13:1 at idle, whatever its happiest with. 1500-3500 cruise, can be 13.5-15:1, and then wide open we're looking for about 12.5-13.2:1
sweet! i went through this a few years ago and found a really good paper by a guy called Keith Francks, its a really good step by step way to tune the carb, we start with the float level, and then idle and wor our way up, and at the end you know what does what, and the car runs great, i'll post it.
for AFR's we can shoot for about 12-13:1 at idle, whatever its happiest with. 1500-3500 cruise, can be 13.5-15:1, and then wide open we're looking for about 12.5-13.2:1
Here is the driving video. I apologize for the wobble:
The AFR at idle was 11-12. It fluctuates during idle as well as driving. While driving it goes between 12-16. Its within the bulk park. It keeps on changing during driving. I am awaiting for my new set of jets and e tubes and once I put them in I will send an update here. thanks
Replaced oil, filter, plugs (BR8EQ) cap and rotor. Drove the car, noticed no improvement, but I am ok I did this for piece of mind.
2nd I replaced e tubes and jets on 48 DCOE:
Before After
Main jet: .200 .180 Air correction: .180 .160 Idle jets: 65F9 same e tubes: F11 F7
3rd I reverted the mixture screws to 1/2 turn out from 1 turn out because I want the car to run leaner not richer.
Have not driven the car yet, coz the weather is crapy in CO right now, but I will drive it soon and post here.
Still to check:
1. TDC and distributor timing, adjust if needed. I do have timing strobe light, but I haven't used it yet. I know there are instructions, but if anyone has a HOW TO do this on a RX7 please post here. Also I need to mark the Gilmer pulley when rotors are in TDC. Not sure how to do this. If anyone has a procedure pls post here. Thanks
2. Measure RPM for AFR measurements, the best I can. This is not easy coz it fluctuates quite a bit during normal driving but I ll try.
I have few other new bits and pieces for the carburetor, but I am not replacing anything else until I see some improvement with new e tubes and jets.
1. TDC and distributor timing, adjust if needed. I do have timing strobe light, but I haven't used it yet. I know there are instructions, but if anyone has a HOW TO do this on a RX7 please post here. Also I need to mark the Gilmer pulley when rotors are in TDC. Not sure how to do this. If anyone has a procedure pls post here. Thanks
I don't know if this person is on here but RAD potential on YouTube just posted a video on how to find TDC.
Hi thanks for posting the video. I watched it and its no brainer. One thing I am not sure about, he said find ANY apex seal through T2 plug hole on the rear rotor to begin with and mark the pulley. How can that be as there are three APEX seals on the rotor and they are 120 deg apart. How could it not matter which seal you start with? Could someone explain this please.
- AFR at idle is between 10.5-12.0
- AFR at cruising speed 65-70 mph is 10 and is solid.
- 1st 2nd 3rd 4th its about 10-10.5
Driving:
Re-jetting definitely helped with stumble. Now I can get in 1st 2nd 3rd pass 4000 RPM. Before it wouldnt go pass 3000 RPM. But it doesn't accelerate quite as much as I would like in 2nd, once its pass 3000 RPM, between say 3000 and 4000 RPM. It starts to accelerate again in 3rd 4th and 5th. I wonder how timing is set, thats the next thing I will try. Mark TDC on Gilmer pulley and check the distributor position, play with it a bit try retard it then advance it a bit and see the difference. I feel I am very close even though right now the car drives nicely just not quite at 100%.
Hi thanks for posting the video. I watched it and its no brainer. One thing I am not sure about, he said find ANY apex seal through T2 plug hole on the rear rotor to begin with and mark the pulley. How can that be as there are three APEX seals on the rotor and they are 120 deg apart. How could it not matter which seal you start with? Could someone explain this please.
with 1 rotation of the e-shaft, the rotor turns 1/3 of a rotation. for each apex seal that u align with the plug hole, the shaft is in the same position within that 360 degrees of rotation.
- AFR at idle is between 10.5-12.0
- AFR at cruising speed 65-70 mph is 10 and is solid.
- 1st 2nd 3rd 4th its about 10-10.5
Still way too rich.
Buy a good set of jets, and go test them on the road (starting with getting idle afrs right).
Now that you saw it is quite easy to change jets in a Weber, just play with it.
Still way too rich.
Buy a good set of jets, and go test them on the road (starting with getting idle afrs right).
Now that you saw it is quite easy to change jets in a Weber, just play with it.
How do I correct the AFR? Mixture screw? Timing? What else? Whats are correct AFRs?
How do I correct the AFR? Mixture screw? Timing? What else?
the idle mixture is the idle mixture screw, everything else is done with the jets.
think of it like this, everything from the tip of the exhaust to the engine to the air filter dictates the air flow, and your job as a tuner is just to give the thing the right amount of fuel, and a spark
the idle mixture is the idle mixture screw, everything else is done with the jets.
think of it like this, everything from the tip of the exhaust to the engine to the air filter dictates the air flow, and your job as a tuner is just to give the thing the right amount of fuel, and a spark
I understand the theory, I need instructions or links to instructions for AFR correction. Too lean do this, too rich do this and correct AFR readings. Could you guys with good tuned in webers post your AFR readings here.
I understand the theory, I need instructions or links to instructions for AFR correction. Too lean do this, too rich do this and correct AFR readings. Could you guys with good tuned in webers post your AFR readings here.
ah ok,
at idle, just turn the screws until it idles the best, and then maybe 1/8 turn leaner. this should be about 12.2-12.5:1 AFR. ideally this is with the idle mixtrue screws out somewhere around 1/2 turn. if the idle mixture screws are more than a turn out its telling you you need the next size bigger jet (someday), and if they are in most of the way its telling you the idle jet is a bit rich.
from 1250rpm to about 3500rpm cruising, AFR can be 13.5-14.5 or even a bit leaner.
at high load/Wide Open throttle you're looking for 12.5-13.2:1 give or take. the factory is about 12.2 and it gets a little leaner (12.8) and then goes rich and by redline its in the 11's.
at idle, just turn the screws until it idles the best, and then maybe 1/8 turn leaner. this should be about 12.2-12.5:1 AFR. ideally this is with the idle mixtrue screws out somewhere around 1/2 turn. if the idle mixture screws are more than a turn out its telling you you need the next size bigger jet (someday), and if they are in most of the way its telling you the idle jet is a bit rich.
from 1250rpm to about 3500rpm cruising, AFR can be 13.5-14.5 or even a bit leaner.
at high load/Wide Open throttle you're looking for 12.5-13.2:1 give or take. the factory is about 12.2 and it gets a little leaner (12.8) and then goes rich and by redline its in the 11's.
hope that helps!
Thats a good info, thank you. Also I saw your post #28 with AFR numbers. Now I know what AFR should be. The mixture is currently 1 turn out, I will put it to 1/2 turn out to make it leaner. More driving tests tonight and I ll do new AFR readings and post.
Still way too rich.
Buy a good set of jets, and go test them on the road (starting with getting idle afrs right).
Now that you saw it is quite easy to change jets in a Weber, just play with it.
I do have a good set of jets and e tubes. I went one size smaller on main and air jets _and_ I went from F11 to F7 e tube. I may need to go back to bigger jets with F7. That could be what it needs. I ll know when I re-measure AFR.
with 1 rotation of the e-shaft, the rotor turns 1/3 of a rotation. for each apex seal that u align with the plug hole, the shaft is in the same position within that 360 degrees of rotation.
That makes sense. I ll go ahead and check TDC and mark my Gilmer pulley and play with +/- distributer position. thank you
I get allot of carb parts from Eurocarb in the UK. takes a couple weeks for the parts to arrive , but always good quality and correct. There are two blank plugs just above the throttle plate, remove them. This is where they go,
then hook vac lines to dist advance for L and T. This is my Dell but should be similar to your Weber
Idle looks ok, but the rest still seems too rich. Would putting bigger main and air jets, say .200 and .180 back in, with F7 e tubes make it richer or leaner? I am guessing richer (more fuel for the same air). Also I do have one size smaller jets: main .170 and air .150. Should I try that combination?
Also I am finding the car would not rev much above 4000 RPM. Should it? Otherwise it drives well and it sounds like a race car
Idle looks ok, but the rest still seems too rich. Would putting bigger main and air jets, say .200 and .180 back in, with F7 e tubes make it richer or leaner? I am guessing richer (more fuel for the same air). Also I do have one size smaller jets: main .170 and air .150. Should I try that combination?
Also I am finding the car would not rev much above 4000 RPM. Should it? Otherwise it drives well and it sounds like a race car
try the 170 jet and see what it does, it should lean out the WOT, make one change at a time.
try the 170 jet and see what it does, it should lean out the WOT, make one change at a time.
OK, but the doc says that MAIN and AIR jets need to be changed together. So if I put .170 for main, I also need to put .150 for air. There has to be .020 difference between them according to the doc.
