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Weber jets??All who live for their triples please read this


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FYI, chokes don't affect the idle circuit. They're for the mains.

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  • 4 weeks later...

Summer kicking in here in Phoenix and I am about done with the Triples for summer.

 

Need to tweak the float levels back down just a bit due to sloshing and idle changes turns (spilling into mains).

Then open the last progression hole a bit and try to extend the progression just a teence more into the mains.

 

Its just too darn hot for them here in summer even with all my heat shields.

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  • 1 month later...

Hi,

 

new to the game, and would like som opinions on some things before ordering.

 

Bought a set of 40mm dcoe 151 for my 240z L24. Engine is stock, minor port work on top (e88), I have added 6-1 + 2,5" free flowing exhaust, pertronix and MSD box, Carter fuelpump.

 

Put the webers on, and the car started. I`ve had no hard time with the webers, and had a local guy to set them up. They are synced, and he has tuned the low speed part. Friend of mine have a dyno, and wideband. Desided to take a look after the tune, because I dont feel like the engine is deliver the power.

 

The low speed range/cruse was about fine between 12-15 on the normal driving/cruseing. But when i flat out it hits 10,6 a/f all the way. Would like to come up to 13..?

 

My setup is;

 

28mm venturi (chokes)

130main

f11

170air

45pump

50f9idle

 

I have been in contact with a weber parts dealer, and he would like me to change to:

 

30mm venturi (chokes)

120main

45f9idle

 

or, if I would like to use 32mm venturies, and stay with 130main, 50f9 idle.

 

Wich seems bether after reading this thread, but what would be the best setup? (are at the same time ordering books, I know I have some learning to do!)

 

See that many are going with 32mm venturies (chokes), what do you think? The way my engine runs now, it dosent "kick in" at all.

 

Many thank`s!

 

-Jimmy

post-11135-064498500 1339162417_thumb.jpg

Edited by Jimmy
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If you look thru the post, you'll see that I was running 32mm chokes with L28 / N42 + flat tops with mild cam (MSA stage II). The outcome was good even if I was outbreathing a little my carbs.

Changing the chokes will cost you some significant amount of money. I would first check if you like the behavior of your current setup (does it rev freely to high rm?). I would try to change main jets to see if it helps. If you're at 10.6 at WOT, definitely drop to 120 instead. Make sure also that your timing are ok, they can foul you. At 10.6, the tip of your exhaust should be very black.

 

On a side note, by increasing the choke size, you'll reduce the vacuum. It will require the carbs to pour more fuel at idle, idle jet would have to be increase, not decreased. It depends of course about how your current setup is.

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Supposedly DCOE40-151 progression is much different than -18, and isn't suitable for L2x I'm my experience. Same with Dcoe45-152. But there is a later model (152g?) That might be better.

 

 

I have the 40-151s as well for my LD28 race motor (36mm venturis). Falls on its face if I don't roll the pedal on properly, wideband picks it up for me, too. I'd love to see a dyno comparison of my car before/after a proper progression circuit correction.

 

Guess I'll have to settle for the carb to ITB comparison, but that won't be fair. Especially since I'm under-carbureted as it is.

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The drivability difference with my repositioned progression ports is striking. Around town it is just smooth and seemless transition no matter the throttle modulation speed or range.

 

Only lingering fault is a bit lean at cruise right where the last progression trails off and before the mains kick in.

My floats are as high as they can go (too high actually) and yet still the reach from the last progression to the mains is just a bit far.

Only reason you would know is the W/B and occassional sneeze in cruise.

Solution is to enlarge the last Prog port which I haven't done.

 

 

Sitting on Craigslist searching for GSxR750 ITBs / Megasquirt for a summer project.

Or the Extrudabody setup which is pretty reasonable actually and mounts to my intake manifold.

 

The idea of making and building the GSxR setup by my own hand and willpower intrigues me and it may be a bit less money.

 

Summer in AZ. Z is put away for a while unfortunately.

 

Tj

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  • 4 weeks later...

Thank`s guys!

 

The car does not rev freely, but dont know if its the 10,6 a/f, or to small venturi. Anyway, I ordered the 32mm venturies because I wanted to do some testing. Have been playing with the timeing, but with the 32mm it goes way to lean. Reving gently (using idle jet) I have 14-15 afr, once main ciricut comes in, it goes 17+ afr, and starts cutting because it`s too lean.

 

Can I now go up to 55f9 idle, and 140 main, would that do much? Or go down to 30mm venturies?

 

Thank`s!

 

-Jimmy

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I think it is odd to not be able to rev freely or have an AFR of 17:1 with such jets. I don't think it is related to jets or venturi.

 

I think you either have to make correction on timing (timing very off could make false AFR reading) or to check fuel level in bowls or to check if needles jets are not damaged or air leaks or loose parts, etc.

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Ok, thank`s. I may have been giving the wrong picture on "not reving freely". It revs, and runs good, no stumbe etc., but it does not kick-in like other people say it should do with webers. I have played alot with the timing, and it does not do any big effects on the af. I`m running stock distributor now, without vacuum. Is replacing this with a full mechanical one the thing to do?

 

Right now I`m running 38deg. on full advance, but its like 20 on idle.

Edited by Jimmy
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Do you have your own wideband installed in the car?

 

That is really the only way to do it. Can be confusing, the difference between Lean and Rich sometimes.

It was often exactly the opposite of what I thought.

 

 

140main is a super-soaker jet.

Even 135s on my 7000rpm motor with 35 venturis was too fat.

 

 

Once you have the wideband in the car everything becomes easier.

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Have you recurved your stock dizzy to get 20° at Idle & 38° total without vacuum?

I see Durrag answer and I support his toughts, how do you read AFR? (if it is done with a narrow band, it is useless to talk about anything but +/- 14.7:1)

 

You've talked about kick-in, that could be linked with idle jet eventually if it happens at low rpm. If it is at high rpm (>3500rpm) it would be related to other jets and I don't think you would suffer really bad performance with your setup.

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I`m driving with a Inovate LM2 on the car when I`m testing/tuning. The numbers I`m refering to is from the LM2. I`m getting the same afr-results, switching between the 28mm and the 32mm venturies every time. So my 130main jet is doing 10,8:1 with 28mm venturi, and then when I insert the 32mm venturies, everything goes way too lean. Hmm..

 

I do not know if there has been done anything to the distributor. What is normal? Should I buy a new one? It is not advancing much without vacuum.

 

Thank`s guys!

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Changing venturis are creating less vacuum at the lowest section. Hence, you need bigger jets to keep the same AFR ratio, so getting a leaner engine with 32mm choke is normal versus 28mm.

32mm vs. 28mm is a big step. 10.8:1 is very rich, you should 2 points higher to be ok.

 

What it could also mean is your engine would not be able to pull enough air to make the 32mm venturi working properly. Somehow I doubt it and you would suffer such behavior only at low rpm. Since I've never tested such combo (only modified engine - I've never touched a stock L-engine :rolleyes: ), I cannot prove what I'm writing.

 

If you're using an LM2 unit, you should record some data and post them here. We would be able to spot other problem maybe...

 

Regarding the dizzy, service manual is saying 17° at idle with no emission control (round tops?) to be around 36° total, so your unit is probably ok.

Anyhow, I still believe you might have something wrong elsewhere (meaning not at the carbs) but since your description of the problem is vague, it is hard tell anything more ;)

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  • 1 month later...

Been reading a LOT of Megasquirt forums lately.

I have read a lot of posts about problems with off-idle throttle response (tip-in).

 

It would pain me to bail on DCOEs, just to spend the rest of my life chasing MS issues.

 

Still researching, but seems it is tricky to dial in the initial throttle tip-in.

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Been reading a LOT of Megasquirt forums lately.

I have read a lot of posts about problems with off-idle throttle response (tip-in).

 

It would pain me to bail on DCOEs, just to spend the rest of my life chasing MS issues.

 

Still researching, but seems it is tricky to dial in the initial throttle tip-in.

 

Do you mean it's easier to tune DCOE's ? and you get three X 2= 6 problems !

No headache with MS if you start with good basics, you can tune in alphaN or Speed density , or a mix, but tip in issues only occur with wrong AE or x tau tune .

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