Webers run cleaner than EFI?

[cygnusx1]

I just finished building this 240Z with triples on it.  It's the first carb'd Z I have owned.  My 76 was factory FI and then coverted to 83 EFI turbo and now megasquirted.  What I find amazing is that upon firing up this 240Z with webers, which has my original 280Z motor in it, there is NO smoke, almost NO exhaust smell, and I can drive around without my eyes burning.  Windows up or down.   ALL of the other L versions I have run with EFI have made my eyes water.  Is is possible that Webers are better at cleanly burning fuel in an L than EFI?

 

Disclaimer, this is purely NOSE tested at this point.  Other than my turbo MSII Z with a WBO2, I don't have a reference for "clean".  

 

 

 

 

Thoughts?

Edited April 10, 2010 by cygnusx1

[yetterben]

My weber's before turbo mind you. Idled at 14.2 steady. Clean indeed.

[Brad-ManQ45]

Sounds like somebody didn't tune the MS properly w/a wideband O2 sensor.

 

There is simply no way that Weber's day in/day out all year long (where there are seasons) can run as cleanly as FI.

 

I can imagine w/all the knowledge accumulated about them w/Z cars that you could get a real close to ideal tune from the get-go though.

[cygnusx1]

       Even with the factory ECCS this L28 smelled.  Now it's the SAME motor, untouched, running Webers, headers, 2.5" exhaust with no cat, and it smells pretty darn clean.  BTW the MSII motor has datalogs to prove that it is running in the 12.8-15 AFR range from full vacuum to 18psi of boost.  It still smells twice as bad as the Weber motor...and I mean both, standing behind the exhaust pipe AND while driving.   I suppose better atomization comes from the way a carb works...or maybe Nissan used crappy injectors, and my Ford Lightning 440cc squirters don't spray nicely either on the MSII.    

Edited April 11, 2010 by cygnusx1

[Daeron]

My guess is, you didn't tune the EFI to be clean you tuned it for power and/or economy.

 

What did you do regarding jets, etc? I am not a carb guru, so specifics is not what I am asking (although others probably would, it'd be greek to me) I am asking, did you go with this recommendation, what that guy had in it, or what you put in...?

 

Chances are, there is untapped power in the Weber setup you are running now, and it is running leaner and cleaner as a result than it could be. You are smelling a space for growth, as it were.

 

You were almost certainly dumping extra fuel into the turbo motor to provide some relief to the combustion chamber, right?

 

However, no explanation can defeat the overall point: analog can function just as good as digital.

[hoov100]

a carb'd motor can run just as clean as an EFI motor, with the correct tune, but the EFI systems can do it a bit more reliably and not just when it's warmed up.everything in that aspect, depends on your tune.

Edited April 11, 2010 by hoov100

[Tony D]

Ahhh, the butt dyno of the nose...

 

Stick a gas analyzer up the tailpipe and do a 5 gas on both the setups tuned comparably and tell us what you find...

 

Then do it again 30 seconds after startup at 30F

 

Then do it again 30 seconds after startup at 130F

 

Then do it again 30 seconds after startup at -30F

 

After that, start to draw conclusions, and then we can move on to 'under load' testing.

 

BTW, is it possible your 2.5" exhaust moves the tailpipe to a proper area for exhaust? If 'not smoking' is a criteria (that is below 10.5:1 AFR, btw, on non-catalyzed L-Engines...) you may want to re-evaluate that butt-dyno-nose of yours!

Edited April 12, 2010 by Tony D

[cygnusx1]

 Oh yeah I know it's just a passing observation, not fact.  But the fact is that my eyes don't burn, either at idle in the garage, or when driving.   This SAME motor made my eyes tear when it was running on the stock EFI (running 100% correctly) and I have owned it since 69K miles in 1989...it's now certainly 2010 and it has at least double the miles on it.  Location of the tip is irrelevant in THIS case.

 

 

 

 

I don't argue that EFI can handle the ocean of conditions better than the carbs.  I understand both systems.

Edited April 12, 2010 by cygnusx1

[Tony D]

"Location of the tip is irrelevant in THIS case."

 

Please explain, the way you wrote it, it appears you have a different exhaust system on it now than before, therefore making where it discharges pertinent...

 

Unless the 2.5" non-cat setup was on the car with the ECCS as well.

 

A five-gas will tell the tale. Fumes into the car are more than just mixture or fuel delivery...

[cygnusx1]

"Location of the tip is irrelevant in THIS case."

 

Please explain, the way you wrote it, it appears you have a different exhaust system on it now than before, therefore making where it discharges pertinent...

 

Unless the 2.5" non-cat setup was on the car with the ECCS as well.

 

A five-gas will tell the tale. Fumes into the car are more than just mixture or fuel delivery...

 

Totally agree, what I smell or don't smell does not tell the exhaust content story.  I have no idea what component of the exhaust smells or burns my eyes. But I am using it as a before/after comparison of either A)Exhaust quantity in the cabin or B)Exhaust quality in the cabin.  However, I can work in my garage (not cabin smell, ambient outside) with the doors open of course, much, much longer with the engine running, since equipped with the Webers, as compared to when it was on stock EFI.  As another reference point, my L28ET 280Z with MSII that is well tuned (says me, and people that have driven it) also smells A LOT more than the Weber equipped L28. I know it's not fair to include that car in the comparo, different animal, wear and tear...etc.

 

Facts and figures:

 

ORIGINAL SETUP:

I had MSA 2.5" exhaust on the L28 in the non-cali 76 280Z with stock injection and stock exhaust manifold.  Tip in stock location, flush with back of 240Z style bumper. 

 

NOW:

In the 240Z, I have that same engine, with Webers now, with an MSA 2.5" exhaust/w headers.  The tip is in the same stock location and also flush with the bumper.

 

Both systems, have and had, a muffler at the tail.  Both cars are stock bodied, in great shape.  I would venture to say that the 280Z has slightly better body seals, as I replaced them, and went over all of the problematic leak areas that are commonly known.

 

 

 

 

 

[olie05]

This sounds more like a turbo vs. NA battle than a carb vs. Efi.

 

If you used the wideband on both cars you have verified that fuel delivery is not a problem, but you still have the variable of the turbo plumbing attached to one of the motors.

 

My theory is that the turbo configuration is causing your idle combustion temperatures to operate in a different range, which emits more noticeable emissions than the NA car.

 

Another theory is that exhaust density and speed is different coming out of the tailpipe, and even if your emissions are the same (in terms of ppm or whatever they use to measure) the slower moving (denser) turbo exhaust will be more noticeable than the fast flowing NA exhaust.

 

I know exactly what you are talking about, and I have only experienced this in turbo Z's (and other turbo cars). I've never had the eye watering sensation in my (NA) car.

[bjhines]

About the exhaust tip...... I had a slip on tip on one of my Zs. It was a "universal" fit with little clamps. The problem was, It overlapped the actual tail pipe enough that it allowed exhaust to get around it and under the rear deck of the car. Simply removing the tip made the difference between suffocation and life.

[cygnusx1]

Yes, a properly sealed and located exhaust system goes a long way to minimizing the smell in the cabin but there are plenty of threads on plenty of websites about smell in the cabin of a Z.  This is about, the smell of the exhaust with factory EFI versus a set of triples.  At idle, in the garage, and also revving at idle, while driving, and engine braking, the Webers smell less.  Yes, I suppose by jetting them "dirtier" I can make them smell too.  BUT, at idle with the idle mix/air bypass screws set for a smooth idle on both the EFI and the Webers, the Webers smell less.  I wish I had a WBO2 on both to quantify but I can only say, "obtaining the smoothest idle by adjusting idle mix @ spec. idle speeds".

 

 

 

 

I have a hunch....that the Webers are feeding the motor a better atomization than the injectors for a more efficient burn...at least at idle.

Edited April 13, 2010 by cygnusx1

[woldson]

I have a hunch....that the Webers are feeding the motor a better atomization than the injectors for a more efficient burn...at least at idle.

 

 

Only if your injector/s are not working correctly.

 

This could be part of your problem, you may have had a injector/s not atomizing properly. Added to the fact that, at idle, the turbo may be cooling and slowing exhaust, producing a denser mixture of the same a/f. (as the carb, just more consentrated)

 

Being less excited and slower, moves out the door slower.

 

Even if carbs and injection can produce the same resolution in atomization, I doubt carbs can be better.

[cygnusx1]

I have a hunch....that the Webers are feeding the motor a better atomization than the injectors for a more efficient burn...at least at idle.

 

 

Only if your injector/s are not working correctly.

 

This could be part of your problem, you may have had a injector/s not atomizing properly. Added to the fact that, at idle, the turbo may be cooling and slowing exhaust, producing a denser mixture of the same a/f. (as the carb, just more consentrated)

 

Being less excited and slower, moves out the door slower.

 

Even if carbs and injection can produce the same resolution in atomization, I doubt carbs can be better.

 

 

 

I agree, in theory the fuel is experiencing a much greater delta pressure passing through an injector, which SHOULD lead to finer atomization, than a venturi fed at atmosphere into a vacuum.  I am going to see if I can find published studies of fuel atomization in carburetors versus injectors.  I am sure the subject is hugely documented somewhere.

 

 

 

[19762802+2]

You could always take both your EFI Z and Weber Z to an Emissions testing place and compare the results.

[cygnusx1]

 

You could always take both your EFI Z and Weber Z to an Emissions testing place and compare the results.

Guys...the L28 was on factory FI and now it's Webers.  It's the SAME motor that smelled before and doesn't now.  I can't compare them to eachother. I can use my L28ET to compare to the L28 with Webers but that's on MSII and a low compression turbo motor; different ball game.  

 

It's not a big deal, I just found it interesting that the engine smells cleaner after converting to Webers.  It most likely is due to the jetting resulting in a less smelly mixture...whatever that means. 

Edited April 14, 2010 by cygnusx1

[19762802+2]

 

Guys...the L28 was on factory FI and now it's Webers.  It's the SAME motor that smelled before and doesn't now.  I can't compare them to eachother. I can use my L28ET to compare to the L28 with Webers but that's on MSII and a low compression turbo motor; different ball game.

 

My apologies, I missed that.

[cygnusx1]

 My fault. Random thoughts clutter my head when I type, and confusion runs down my ribbon cables, to my fingertips, and out to the internet.  

Edited April 15, 2010 by cygnusx1

[ZR8ED]

I've been thinking about this in the back of my head while watching this thread. I see where you're coming from Dave, and I don't think it has much to do about the motor itself. You ran a 30 yr old stock restrictive FI system on this motor previously, and setting aside minor differences in that fact that it is in a different car, with slight differences in exhaust systems etc, Unless the compression drastically changed, or some other type of damage has happened suddenly or over time/mileage. (though it sounds like this motor is purring like a kitten anyways so that rules a few things out) The major change to the system is FI to Webers.

 

As these motors are simplistically an air pump, I absolutely believe that your "air pump" is MORE efficient with the webers than the stock FI. The stock FI intake system is far more restrictive compared to the webers on a short runner manifold. You are definately able to supply more fuel AND AIR into the motor for better combustion. With a good tune, this better combustion with more air/fuel means more HP, and this results in more flow out the exhaust due to the motor running more efficently.

 

As for the smell? It is likely that the CO2 and NO2 ratios are different, and it is noticeable to the nose.

 

or, I haven't learn **** in the last 25yrs of playing with cars, and I'm right out to lunch on this one. I'm at least 51% sure it is not the latter! hehehe

 

Have fun enjoying the car!

Scott