Carbeurated v. injected

Happy holidays Jeff, and thanks!

With stock settings, there are several classic ways to set mixture described in Birdman's excellent Weber tuning thread a bit below.

When re-jetting or setting up de novo as in the 3.2, using a A/F dyno or a portable A/F meter (e.g. LM-1) are the gold standard.

When recently asking about Color-tunes, was told that they lose their well known accuracy if newer 'oxygenated' fuels are used. Now trying currently to make up a tap to fit my portable LM-1 Air/Fuel meter to the stock individual gas ports on the headers to possibly give barrel by barrel Weber tuning. We'll see.

Ho Ho Ho!
best,
rt

 

Damn Don,
Those carbs look absolutely beautiful.

Oh yea, carbs do rock.

 

CARBS, CARBS, CARBS.

Love the sound you get at the top and the bottom of the engine.

Don't think FI can do that. No giant sucking sound with FI.

'course, I've only driven an FI FCar, never owned one, so, I may be speaking through my hat, as it were.

DM

 

I like the carbs
Image Unavailable, Please Login

 

mm, so do i. screw atkins.

 

I can compare a little bit between the two because I have a 1977 308 GTB with carbs and my wife just took delivery (Xmas gift from the coolest guy in the world, me) of a Mondial QV with injection. Although the QV isn't even registered yet, we have taken it on a few illegal spins, and the first thing I have noticed is how easily it starts and runs when cold. It is very "modern" in that respect. I started it this morning to move it into the other garage bay. It was 15 degrees out. The car started instantly just as easily as my Toyota. The 308 in cold weather needs a bit of "procedure" to start. Yes, it starts in the cold, but you have to flog the gas pedal a few times and it usually catches. If you don't know how to start it, cold weather can be tricky. Once running, you have to love the sound of the carbs, but carbs are not without their idiosyncrasies. Lets be honest, they sometimes starve for fuel on hard corners and then hesitate accelerating out of the corner. They need some tweaking more often than FI, to keep them running right. It's not hard, but if you can't do it yourself, it's $500 to have them tweaked by someone who knows how to do it. For a lot of people, FI is a lot easier to live with, and it certainly makes a car much more "modern" in feel and behavior. (This may be good or bad depending on the person in question).

When something goes wrong with FI, it can be hard to diagnose, whereas carbs are pretty simple to troubleshoot and repair.

I feel that both systems have their strengths and weaknesses and you have to decide what is more important to you. For a Mondial to be driven by my wife, FI is better. For a 308 to be driven by me? Carbs are cool.

Birdman

 

Image Unavailable, Please Login

 

Carbs or EFI ?

Windows or Macintosh ?

Analog or Digital ?

I just like the fact that I don't have to tinker with it, to enjoy it. Like a master bartender mixing the perfect drinks, the EFI unit figures it all out to make sure the fuel/air ratio is just right. As mentioned many times here, allot of it has to do with cold weather driving. While on a drive transitioning to high altitudes may require a stop with screwdriver in hand.

True, when things go wrong, they really go wrong!

 

nice analogy!

ouzo & coke in a pre-mix can is always nice, but mixed at the bar is usually better... but occasionally disasterous.

 

Maybe the truer statement would read: Real men work on their own cars and TUNE their own carbs? Just kidding, sure don't want to offend anyone. But FI was really needed for cornering in F1, but if you look back you see Ferrari using carbs in F1 up into the late 60's, even though there were systems that could have worked. Why? Because those Weber carbs are rock solid reliable. Myself, I wanted the closest Ferrari I could get to the mindset of a "real" Ferrari, and set my mind on finding a 77 308 GTB. Why? Because I didnt feel I could afford a glass car, but I wanted not only simplicity, but performance, and that elegant and simple style of the 308. Yup, those carbs will fall flat on thier face in a hard long corner, just about the time the sump is dry of oil. Somebody was thinking on that one!

 

Me also thinks full race cams would be a sweet Christmas present for the Mondial, the webers will thank you also. Merry Christmas to you also SNJ.

 

Oh, that's not true. If you're comparing a multi-carb engine to a single throttle body EFI, then probably. If you compare to a multi-throttlebody set-up the difference is about 5%-10%. The reason is that you can up size the throttle bodies until they have not effect on flow. If you try that with a carb, the engine just won't evn run in the lower rpm, it just coughs and stumbles.

 

I love the smell of webers in the morning. Imagine while driving a Miura, then telling your passenger, "excuse me while I adjust my webers."
Image Unavailable, Please Login
Image Unavailable, Please Login

 

Heh, lookie there. 12 individual mixture tuning screws.

 

Birdman,
What kind of performance comparisons can you give us between the 85 mondial and the 77 GTB? Which do you think has more H.P.?

 

oh well sure, use underhanded tactics like "facts" and "real-world experience" then, using those you can prove anything that's even remotely true.

i think my point is, it requires a very efficient motor before the carbs become the bottleneck in performance, and we're talking old motors here. chasing that last 5-10% of performance through EFI and multi-throttlebodies doesn't sound particularly like bang-for-buck on an otherwise stock engine.

of course i have but a smidgen of the experience of many here, so i guess i'm mostly regurgitating theories and thoughts i've had.

the philosophy i'm going by on my current engine build (only a 4banger) is that the engine will first be setup to run as good as possible (lightened, balanced, blueprinted, hi-po ignition, lumpy cams, etc.), if i'm not getting good enough flow/efficiency, further head modifications are in order. if everything is running great there, and after properly tuning the carbs i'm still not getting acceptable performance, then i'll consider EFI.

after that if i'm still unsatisfied, i'll be bugging you for supercharging advice.