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Triple OER Carburetor Troubleshooting - Help


adam.

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Running the car with jet stack out gives ya an excellent "view" of how often you're on the idles/progression holes.

One misconception is that people think the main jets come on at some certain rpm..Not So. The main jets come on at a certain butterfly position. You can be at 5,000 rpm and very partial throttle and be running nothing but idle jets. Hell, I got my car up to 60mph with the main jet stack sitting in the garage. 

 

Now, I wouldn't adjust the float levels for the idle jets. Yes, I assume it would have some impact but you need to focus the float level for the main jet. As you mentioned in an earlier post. 

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OK, noted Steve, regarding adjustment of floats for idle jet.

 

And you can definitely run the car without the mains installed.

 

There has been a delay in ordering and receiving of the new jets so no new information to be mentioned. It should hopefully be here by early next week.

 

I have access to a dyno at work again which will help dial everything in.

 

And I think my OER emulsion tube and jets should do for the moment! Will get too expensive otherwise

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Running the car with jet stack out gives ya an excellent "view" of how often you're on the idles/progression holes.

One misconception is that people think the main jets come on at some certain rpm..Not So. The main jets come on at a certain butterfly position. You can be at 5,000 rpm and very partial throttle and be running nothing but idle jets. Hell, I got my car up to 60mph with the main jet stack sitting in the garage.

 

Now, I wouldn't adjust the float levels for the idle jets. Yes, I assume it would have some impact but you need to focus the float level for the main jet. As you mentioned in an earlier post.

 

This is why you run the top gear test at progressively more throttle angle.

 

On Mikunis it's well known highway cruise is done on idle jets.

 

Mikuni specifically states at WOT you are tipping into the main transition at 3,000 RPMs as I recall (if their other parameters regarding sizing the carbs are followed.)

 

That pretty much is what I've used to explain to people why fiddling with a main jet for mixture adjustment below that point is basically fruitless. There isn't enough draw to top the mountain as it were...to get fuel flowing down into the boosters before that point.

Edited by Tony D
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  • 2 weeks later...

Update:

I checked the timing and I don't know how you guys do it but it seems like the motor is reving too fast to tell what exactly the timing is at 3krpms.

I have received #55 and #57.5 idle jets, the #55s are still too lean to even accelerate, while the #57.5s have a cruise AFR of 12.5 and acceleration is in the 13s - 14/15 which cause stuttering (around 2.3-3krpms). Idle is about 13.

Any ideas what could cause this lean spot causing the stutter? I cannot get my head around it. I have tried checking timing and best I can do is 15 degrees at idle.

It seems like I can't get cruise any leaner without causing hesitation on acceleration.

 

I'm guessing it's that dreaded transition to the mains..

Edited by adam.
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I checked the timing and I don't know how you guys do it but it seems like the motor is reving too fast to tell what exactly the timing is at 3krpms.

 

 

If you are saying the timing mark is bouncing all over the place and you can't get a reading? That means two things. The dizzy is not holding a consistent timing or the timing light is not working correctly. The 2nd not being likely. Make sure the plug is gapped correctly, swap the ignition wire out with another from 2 through 6 and try again. And I just realized you have a 240..Are you still running points?

Edited by steve260z
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Revving to fast? You just need to be above the proper rpm to make sure you have all your mechanical advance in.

Transition can be a bitch to figure out. I fought it for a long time . I got it down to just a mild hiccup every once in a while.

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"Shift, ctrl Arrow Up Up Up"

 

People who say 'carbs are easy' have never really done anything but bolt on something that runs 'pigbog rich' and were satisfied by it.

I know what I would do with a Megasquirt...go add fuel ONLY in the MAP Blocks where the stumble was happening.

OR 

Move the timing up.... 

 

It is done sequentially, you don't even slow down just run through the area....lift....make the adjustment and go back up through it again to see what it did...next load cell/transition point...

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I will need to double check using a different timing light as the one I'm using is a bit dodgy actually.

 

And I'm running a 280zx electronic distributor.

 

I don't think increasing the pump will do much as the lean is a few seconds after the throttle is pushed.

 

I will need to have a play around with the float levels I think.

 

And it may be hard to tune now but that satisfaction of having done it will be worth it. I could have easily paid someone to set these up but money can't buy experience.

Edited by adam.
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I don't think increasing the pump will do much as the lean is a few seconds after the throttle is pushed.

 

 

The OER pump adjustment screw dials the amount of time the pump last. Dialing it up will make the stream of fuel pumped into the intake last longer so it might help in your case. Unless you are pressing the throttle and the taking your foot off and then it goes lean. If you are pressing it and keeping it down and it goes lean the increase in duration will keep up with the amount of time the throttle stays depressed.

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I wouldn't be happy with 12.5 cruise. That's even a bit rich for WOT.

My engine would show lean under moderate acceleration but fine WOT.

I messed with the bleed pipes until I negated the stumble-

Then my engine went all to hell

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Is that so? Interesting because I did not know that..

 

It is leaning out while my foot has been down for a few moments.

 

I will have to experiment with it also.

Yea. The adjustment screw is on the top center at the motor side of the carb. They are delicate so be careful but it is unique to OER I believe and a pretty cool thing. The float adjustment is nice too.

http://www.racetep.com/tepoer.html

There is a picture of it here.

Better pic here

http://lupinusflower.ocnk.net/product/9

Edited by zguitar71
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Yea. The adjustment screw is on the top center at the motor side of the carb. They are delicate so be careful but it is unique to OER I believe and a pretty cool thing. The float adjustment is nice too.

http://www.racetep.com/tepoer.html

There is a picture of it here.

Better pic here

http://lupinusflower.ocnk.net/product/9

 

thats a great feature ! once my AFR gauge is in i will mess with the e tubes. got some jb weld to get that bog sorted...

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Yeah, I am aware of the float adjustment as well as the accelerator pump adjustment screws but if I must be completely honest, I thought the pump adjustment was more to do with its 'load' or amount of fuel it releases, not duration of its fuel release.

 

I will have to have an experiment with that though to confirm. Been too busy with work to really have a play.

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So the solution to my lean hesitation with the #55 pilots installed was to simply adjust the pilot screws/idle adjustment screws out another half turn or so.. Putting them around 2.25 turns out from full lean (ideal is 2 turns +/- half a turn).

 

With the #55s installed, 29mm fuel float level and 2.25 turns of the pilot screws, the car cruises with an AFR of 13.5, idles rich around 12.5-13, but light acceleration is now smooth being around 13:1 AFR and creeping up to about 14:1 in second gear.

 

Although idle is a tad rich, drive ability has improved which I guess is more important in this situation. OER pilot jets do not allow you to change air hole sizes like Webers to assist idle mixtures and cruise mixtures independently so this will have to do.

 

WOT is currently around 12.5-13 which I think is spot on but goes a tad rich in the upper rev limit which is telling me I need larger air correctors which I currently don't have, but that's easy in comparison to slow speed accelerations and cruise stuff.

 

That is all. thought I'd give you all an update! 

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