Tuning the webers…. advice/experience requested..

I'll have to go see the Jalpa V8 video you're talking about but the V12 is the horrible one and I have an idea for that one I might try out I just have to think it through for the potential unintended consequences. A stuck throttle is not optimum.

If you not happy with the non consistent idle and slow speed operation of your Maserati I think the real issue is carburetors vs FI. If the balance is "reasonable" and tracks that way up through the full throttle range IMHO it's probably not the cause of your complaints. Back in the early 1980's when I first started driving these sort of cars people didn't complain about this because most were still weaned on carbs and FI wasn't terribly good as yet. People stove to get the carb versions of several models because they made more HP. It's all very different now. We have one engineer in the Vintage Lamborghini Group who has converted his Espada to FI, digital ignition and has nitrous to boot. He gets much better mileage and power plus he can run on regular when he wants by selecting a different map.

Carbs are fun but combined with a traditional distributor ignition system they are very limited.

 

Hi Bob,

https://www.youtube.com/watch?v=BSc1WOQNfRo

https://www.youtube.com/watch?v=d8E3i-cgIAs

https://www.youtube.com/watch?v=7MV3WvJVAY8

I'm much happier with the way it runs now, it's a lot smoother and pulls better. Mileage still sucks, but I think I need to go back to the beginning for all the carb settings and start from scratch instead of just tweaking from my preexisting settings.

Mileage is still around 20l/100km, while CharlieA (Jarle) is getting 12l/100km, almost double! So I am going to keep tweaking it and see if I can at least get closer to 15l/100km. That would be acceptable.

Jarle mentioned a Haltech aftermarket EFI system, but it requires a custom made or adapted manifold. I've read other places that a Pertronix distributor will also offer both better performance and mileage. My wish was to get her running nicely as stock first before I start fiddling with all sorts of aftermarket upgrades. Ideally with all the smog stuff removed.

I just wanted to know how precise one needs to be to get a decent setup running reliably. Carbs are nice, and the sound the V8 makes with the Webers is all part of the allure of the car!

 

You have the Bosch ignition box and there are no points in your distributor right?

That's how my ahem, 77 Bora came so I can't imagine you have points?

Pertronix is of no help as you already have a magnetic impulse system triggering the ignition.

Find out how Jarle has bypassed the emissions system on his.

Conversion to FI is a big and expensive deal and something to be tackled by a non engineer. Jarle has been working on that for his 224 Biturbo for a few years.

But getting rid of that whole ignition retard via vacuum operated by the microswitch will help. Then also getting your distributor's advance curve remapped to non emissions spec will also improve things.

You should have someone check your cam timing too. Get help for that.

Once you've eliminated the emissions system stuff you probably will have to re-jet your carbs. Get some help or if Jarle has already done all this find out from him.

Carbs used to scare him LOL . I Guess he got over that.

BTW, I looked at that video and it looks like a scaled down version of the V12 linkage, lots of levers and far more complex than the simple linkage on the Maserati V8s. Count your blessings again.

What would make the linkage easier is if the connection point to that single rod was adjustable for/aft with a single nut with some built in resistance to rotation that didn't require another locking nut to secure it. That way you wouldn't get the jump in calibration when you tighten the two nuts to secure the position.

The Lamborghini suffers the same issue on all of it's links from the carbs to the main horizontal linkage rods and there are two of them connected by a single vertical rotating arm (#15) which pulls/pushes on each of them simultaneously. Each of those horizontal linkage rods has it's own very strong spring wrapped around it to ensure throttle return for each side.

The problem is that and adjustment on one side between the horizontal link to the vertical arm causes movement on the other side thus and adjustment on one side affects both!

http://www.eurospares.co.uk/userImages/110/Large/110_003_2.gif

Springs 7 & 14 end up fighting each other in this diagram when adjusting rods #2 to obtain R & L bank balance.

Then rods # 11 have to be adjusted for all 12 cylinders to balance the carnbs individually. If you substitute the originals with ones which have a RH & LH thread on each end then you can lengthen and shorten the rod WO having to remove the end connector from the rest of the linkage.

But the reality for me anyway is that when tuning this setup with the locking nuts unsecured the vibration from the engine makes those rods rotate quite easily all by themselves so the engine goes wildly out of calibration almost immediately. They also get quite hot and as already mentioned when the locking nut is applied everything jumps a bit in adjustment.

It's just lovely. But I have some ideas to fix some of this.

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Here you go - daydream material. These are 3004 DCNF pattern throttle bodies from Borla Induction. There are quite a few injection/ignition computers available now that are cheaper than Haltech. Given the angle of the collectors, I wonder if this is intended for a Bora installation?
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Ole Roberto ,

Correct. And thankfully!

I was wondering the same, after looking over their website and product listing.

Firstly, if I'm not mistaken I think he bought a Euro version, so there was no emissions stuff.

I think we basically just pull the air pump, plug the hose connections, and pull all the stuff off of the front of the air box, along with the solenoids and charcoal canisters. The manifold vacuum loop goes into the cabin (consumption gauge), I'll plug any left over branches there, and the brake booster is run off of the vacuum pump on the rear of the cam cover by cylinder 4.

I really don't want to go there.

Did that last week, but haven't done anything else except verify that the advance is according to the manual, it's close enough.

That will have to wait until next time, after I pay the bill for the last month of workshop activity!

I've asked, but I think he's focused on other cars at the moment. The jetting values are given in the service manual for both versions, and I've noted all of my settings and values, so I'll take things from there. I was also planning on finding a shop with a dyno that can tune and tweak it and have experience with carbs.

I love carbs. But I wouldn't want to fiddle around with ECU mapping and injection stuff. Much prefer the old school stuff...

 

The Haltech system Jarle has is overkill for this but he's still have to build a map and though there are cheaper systems out there that can learn and generate maps there's still a lot to do to go to FI. I don't get the sense that this is a very viable idea for him.

Whose photo is that?

 

Borla Induction, formerly TWM. I don't know where they got the photo - is it your engine Elliot?

 

I was wondering the same thing.

 

The fuel injection engine shown is the one that a friend of mine has just completed and it is for his Bora. Beautiful, isn't it but he has major resources at his disposal that most of us don't have. I found out that he and I were going down the same road and I gave him the lead on the Borla throttle bodies. My engine is a few weeks away from going on the dyno and I should be able to give preliminary results when it happens. I need to get new headers made for my car for the dyno to maximize the benefits from the conversion.

My take on conversion to fuel injection is that with available throttle bodies that are a direct replacements to the Weber carburetors and the availability of a number of aftermarket fuel injections systems the real problem is the expense which is much more than getting your Webers properly setup. On the other hand, once installed the fuel injection system will preform so well for so long under so many conditions that it would probably make the use of any Maserati more friendly than with the factory carburetor system. However, I am biased so everyone needs to look at their own needs and make their own decisions.

 

Let's talk float level - the QP3 service manual specifies 48 (EU) to 50 (US) mm float level.

Reading tips on other forii & in Pat Braden's "Weber Carburetors" and John Passini's "Weber Carburettors, tuning tips and tricks", correct float level is described as essential for the proper operation of the main circuit and of the emulsion tubes. Too high a fuel level in the float chamber can cause a general rich condition with poor mileage, while too low results in leaner overall running and lack of power.

I'll have to dig out my notes to check, but believe I set mine to 50mm. I wanted to know what the more experienced people find as far as the float level's influence on drivability, power and mileage. Sources seem to recommend changing 1mm at a time to find the optimal setting, and of course everything else (idle mixture, syncing, etc) has to be set anew with each change. Will one actually see any difference in how the engine runs between the factory specs of 48-50mm?

Any experiences or comments on the effects of float level on the rest of the system?

 

The float level determines when the main jets begin to feed fuel, the higher the level, the sooner the mains begin to feed fuel. The US spec is lower in order to delay the mains coming in to keep the mixture leaner to meet the EPA requirements of the day. That was the only way they knew to do it before fuel injection. As a general rule, the float level should be 3-4 mm below the transfer port in the jet well. This measurement can be used for all Weber carburetors. For practical purposes, you can use the Euro settings and usually, you will find any 'flat spots" between idle and the mains coming in, will be minimized.

 

Hey Art,

Are you running alcohol free gas?

I bought a colortune for my Espada but unlike the Maserati V8 which has that wonderfully easy sparkplug access it proved very difficult to use.
So I used a digital tach and tuned each cylinder to the lean point of no misfire and then enriched each cylinder equally trying to chase a stumble off idle and lean out flat spot at higher rpms on the road.

I chased that for a very long time and I could never get it to work properly until a tech informed me that it wasn't possible to tune the car properly with the stock jets. Idle and accelerator pump jets had to be increased. Once I did that the issues disappeared though I now think it's a bit overly rich in certain rpm ranges. There's a great forum for discussing all of these Weber issues if you really want to dig deeply into optimizing the tune of your carbs. https://groups.yahoo.com/neo/groups/sidedraft_central/conversations/messages

But I don't know if the alcohol in the fuel creates a similar issue for the Maserati V8s. For the old Lamborghini you can't get there from here with the stock jetting. It's not a USA emissions issue either. My Espada is all European spec.

 

My experience with Colortune is that, in spite of what the instructions say, you want the idle mixture to be just as the color turns from blue to yellow, but full yellow. If you set them at a "blue" color, you will be lean in actual usage.

 

Hi Art,

Happy to learn you have got your engine to run smoothly! It takes time but it is rewarding.
Now do not start turning the screws immedeatly when you start the engine again in a few days, the atmospheric air pressure difference may affect you adjustments!

DWR46: I have the same experience, color tune to the rich side, see pt 16.

Keep smilling

Ciao,

Bart

 

Good work Art!

I've got mine purring smoothly too, but something still must be wrong. Milage is still horrendous. This last tank (will fill tomorrow just to make sure), about 25l/100km, or 9.5mpg.

It would be good to hear what mileage you get after a few longish drives. Maserati's were never easy on fuel to begin with, but with prices here creeping above $10/gallon I'd like to do what little I can to improve the mileage as much as possible. Especially with several others (Jarle/CharlesA in particular) reporting 12l/100km (19.5mpg). Even if I could get somewhere close to 15mpg that would be a big improvement!

Monday after work I plan on doing it all from scratch one last time:
1. set float level to 48mm on all carbs,
2. back off the idle speed set screw so the butterfly's are completely closed, make sure the return springs are still snappy and the carb throttle action precise,
3. adjust the throttle cable so that when the pedal is released the butterfly's return to completely closed position and open to 90 degrees when the pedal is floored,
4. drop the linkage and let all carb butterfly's close completely,
5. open a turn and a half from seated on the idle speed screws,
6. connect the linkage loosely,
7. run the engine on idle and adjust each carb to flow the same amount of air using the linkage and air bypass screws where necessary,
8. use the Colortune together with the RPM meter I just bought and a borrowed exhaust gas analyzer to find the correct lambda and highest rpm reading for each cylinder
9. go back and re-check the airflow and tweak it so it's identical across all barrels
10. go for a drive.

If I still get inexplicably poor milage after that, I'll probably take it to a dyno shop and have a professional look at it. There's only so much I can do. Although by now I've gotten pretty good at tuning the mixture and airflow .

Oh, one other thing I'm planning on doing - unscrewing each idle adjust mixture screw and removing those PITA caps to make it easier to get in and adjust them. It's almost impossible on 3 of the 8 cylinders due to the caps and other things in the engine bay that all get in the way. Maybe it won't look 100% original, but it will be 100% easier to work on!

I'm pretty sure something significant has changed after I had the car in the shop, as the consumption gauge shows less vacuum now than before (i.e. more in the red, almost never in the green unless coasting downhill). Before I could keep it in the green/orange range if I was easy on the gas pedal. Since the timing is now confirmed to 7 degrees BTDC, all the retarded vacuum retard stuff is removed/plugged, and the advance weights work as specified, the plug wires and plugs are new, the carbs have been torn down, cleaned and rebuilt, the only thing left is carb tuning - airflow & fuel-air mixture.

If anyone (Bob?) has any additional thoughts, tips or suggestions, I'm all ears!

 

Hi Q3,

I suggest you leave the linkage on and start by checking the carbs with a vacuum meter 1) at idling speed and 2) at a fixed rpm on the throttle and see which one and how far the individual inlets are off. It could be that the basic setting does not ask for the whole linkage de-coupling?!? For the rest I refer to my notes on the previous page.

Why did you take off the ignition retarding stuff, it will be more difficult to get rid off the popping on the overrun. My Khamsin was a lot easier to adjust than my Ghibli Ss that does not have the retarding stuff.

Concerning the consumption: When driving on the country lanes and flowing in town traffic 25L/100km sounds quite normal. If you like to tease the Porsche owners at the traffic lights 40L/100km is more the money drain to look at... When cruising on the motorways at 140kmh I get max. 14.7L/100km (in the Ghibli) which I think is quite reasonable for an atmospheric 5.0L V8! Maybe at100kmh one can get it even lower but I never travel that slow, the V* rumble makes me feel asleep!
BTW: The Khamsin is a bit more thirsty because of its shorter US diff!

Success,

Bart

 

Hi Bart,

thanks so much for your suggestions.

By vacuum meter, you mean an airflow meter through the carb throats (manometer/airflow), or actually pull a vacuum line and measure vacuum? I can check that tomorrow.

The ignition retarding stuff we've traced back. First, it only works at idle. As soon as you touch the accelerator, it's out of the circuit. It's only there to "cheat" emissions in a crude manner before better methods were developed. I don't experience any popping on overrun, not anymore.

15l/100km in a QP3 would be great! The best I've seen was 16l/100km, but it was before I had the car in the shop on the continent and also before I rebuilt the carbs. So I know it can be better, I just have to figure out how to get it there!

I don't mind 40l/100km when I'm out embarrassing an occasional American muscle car around town (it's amazing how quickly the QP3 can move when prodded!), but not for casual highway driving. The speed limits here unfortunately don't allow more than 90km/h if you can believe that, but somehow there always seems to be a stretch of road that begs for more.

The diff appears to be the same on US and EU cars, a Salisbury 4HU with the same gearing, although the manual version has different gearing.

 

Hi fellahs.
As part and parcel of this type of discussion, I have spent a bit of time on both DCOE and IDC weber tuning. All of the points made by contributors is sound, especially ignition timing, but an item missing is float bowl levels.
More correctly, a float bowl level correction adjustment, for the different weight of fuel now, versus 1964-1980 days.
I live in New Zealand where our unleaded hi RON (98) fuel is quite a bit lighter (specific gravity) than the old leaded fuel. This means that more fuel is needed to 'float' the floats, with a consequent rise in the fuel level within the carbs. This promotes flooding on the progression jets, causing a rich stumble from 1500 - 2200rpm and commonly blackening of plugs in round town driving.
Long and short, I lowered the float levels 1.5mm (0.060") and got such profoundly better driveability it blew me away. I've tested this now on my Alfa Romeo Giulia spider also now and got the same improvement.
US gas may have a differing specific gravity than ours, and I cheated a bit using feedback from race tuners I know who found that a +/- 0.5mm (+/- 0.020) range made the difference between a rich bogging, and a lean out stumble.
Doing a weight check using a very specific volume of avgas and the same volume of your preferred fuel, whether 100% unleaded or 10% ethanol will give you a percentage specific gravity that you can use as a basis for a float bowl correction to save you unnecessary fluffing around with 4 carbs.
Good luck and great driving.
TonyO

 

Some really good info in this thread, I'm looking forward to getting back to working on the car soon.

So Tony, you "lowered the float levels 1.5mm (0.060") and got such profoundly better driveability it blew me away!" Just to be 100% clear, which way is "lowered"?

I.e. did you go from 50mm - 51.5mm, or to 48.5mm? Some people use "lower" to refer to the level of the float, others to the level of the gasoline in the float bowl, which is why I ask.

Mine are set to 50mm as per US spec, and DWR46 posted earlier that 48mm is "best" for both Euro and US spec cars (Euro spec calls for 48mm float level) by allowing the main jets to contribute earlier. Lower float level setting = higher fuel level in the bowl (too high and it will flood).

Art, I would be more than satisfied with 16.9MPG, and reports from other QP3 owners tells me this is perfectly normal for the car, which is why I'm still at it trying to get those kind of figures.

Bart and DRW46 - thanks for the tips, I will keep the Colortune settings towards the rich side next time around. That matches the measurements I made last time, where I aimed at bunson blue and ended up with a lambda around 1.20 or so, indicating lean running. I backed out all the idle mixture screws by 1/8th of a turn and that really improved running. Small adjustments can make big differences!

Since I have to pull the airbox and trumpets anyway to do the float level settings, plus I want to pull the anti-tamper caps on the mixture screws, I figured it was just as well to reset all carbs to a known starting point and do it all from scratch. Otherwise I agree with you Bart, I could just tweak from where it is now, since it is running very well. I can certainly check the airflow as you suggest and make note of it before I start pulling things apart.

 

You don't need the that silly emissions based vacuum retard on to make the car run well but yes it will tend to smooth out the idle quite nicely but at a price!

If you enjoy snappy performance this will slow down the ignition advance from an idle starting point. If you have a dizzy with this "feature" on it check to make sure it doesn't also have the USA emissions advance curve. I'd get that adjusted as well if you want the most out of your car.