# Hesitation on throttle "tip in" with 40mm DCOE's?



## dohc (Sep 28, 2001)

My car hesistates big time on throttle application from fully closed throttle. Once it "clears its throat" it takes of like a rocket, most of the time breaking the tires loose





















Its fun and all, but I'm baiting every cop in a 5km radius








Once on the roll it's fine, work perfect, only on first application of the throttle does it bog.
The gas in it is kinda old, but I'll be changing it, and I haven't really got it really warmed up yet as I've only been driving it around my block.


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## ABA Scirocco (May 30, 2001)

*Re: Hesitation on throttle "tip in" with 40mm DCOE's? (dohc)*

IM sent


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## CdnDub (Dec 3, 2002)

*Re: Hesitation on throttle "tip in" with 40mm DCOE's? (ABA Scirocco)*

Sounds like your going Lean at throttle tip in.
I have the same problem with my Bike ITB's and EFI right now, i just got my wideband wired in so now i can actually have some accurate figures to use for acceleration enrichment, 
Not sure what to suggest to correct the issue with carbs, but do you have a way to accurately measure your AF ratios? it sounds like exactly the same thing my gti does.


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## Andrew Stauffer (Oct 2, 2000)

*Re: Hesitation on throttle "tip in" with 40mm DCOE's? (CdnDub)*

Dave, I was thinking the same thing. I see momentary lean when on tip in, and it makes the car stutter and she isn't gonna go until the fuel arrives. While we're on very different set ups, ITBs/MegaSquirt vs DCOEs, I'd think the similarities are very numerous btw the two set ups.


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## The Quinner (Dec 10, 2001)

*Re: Hesitation on throttle "tip in" with 40mm DCOE's? (Andrew Stauffer)*

The same thing is pretty common on motorcycles that utilize CV carbs...they have butterfly valves to control the air as opposed to lifting a slide...so, they're very similar to the ITBs on your car, Andy...
When the butterfly valve is cracked open, there's a relatively big change in area...that allows air to start entering, but it's not moving fast enough to 'pull' the fuel from a jet or to significantly change the manifold pressures. The bigger the carb or throttle body, the bigger the 'crack' is when it's just opened...and, the more of an off-idle lean-stumble you'll generally have.
If you think about the stock throttle body, it has that little plate off to the side that opens first...then, the bigger plate progressively joins the mix...that, combined with one throttle body feeding four cylinders makes the stock system easy to tune and smooth off-idle.
Individual carbs or throttle bodies are generally done for high rpm flow...that's their strength. The cost will be off-idle and low speed flow.
I have one bike that compensates for the momentary lean condition with accelerator pumps...the opening of the throttle causes a little squirt of gas to come out of a jet. In other words, there's one specialized jet that works via a mechanical arm for that one little moment when the venturi jets and sensors are less effective.
Some of the old school bike mechanics say that if you can't tune it out, your carbs are too big...at least for street use.


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## dohc (Sep 28, 2001)

*Re: Hesitation on throttle "tip in" with 40mm DCOE's? (The Quinner)*


_Quote, originally posted by *The Quinner* »_I have one bike that compensates for the momentary lean condition with accelerator pumps...the opening of the throttle causes a little squirt of gas to come out of a jet. In other words, there's one specialized jet that works via a mechanical arm for that one little moment when the venturi jets and sensors are less effective.
Some of the old school bike mechanics say that if you can't tune it out, your carbs are too big...at least for street use.









Ya, I have that accelerator pump, one of linkages were broken, but I fixed it and they both work fine now. I think maybe I'm running too much fuel pressure, because the linkage pushes on a diaphram style pump, but the link is not solid, it is activated by a spring, I guess it was put there to compensate for fuel pressure.
When I'm pushing the throttle from the engine bay, the linkages don't seem to move that much, suggesting that there is too much pressure.
Thanks for the help guys, let me know if you've made any progress. Next time I'm going with EFI, I know why most have now, carbs are a pain in the AZZ!


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## antichristonwheels (Jun 14, 2001)

*Re: Hesitation on throttle "tip in" with 40mm DCOE's? (dohc)*

You are too lean. If your mixture screw is out more than 1.5 turns, then your idle jet is too lean. Try smaller idle air jets first. IF that doesn't fatten it enough then go up in idle jet with the original air jet. Just like programmable injection, these things gotta be tuned.


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## CdnDub (Dec 3, 2002)

*Re: Hesitation on throttle "tip in" with 40mm DCOE's? (art.clemens)*

EFI is only easier cause you can punch in some numbers to make changes. That and if you have the right tools/software it can suggest changes for you








but its still a pain in the ass to get setup.. I've walked away pissed off from my ITB/EFI project several times lately when things werent working at all.
Good luck getting it sorted out.


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## dohc (Sep 28, 2001)

*Re: Hesitation on throttle "tip in" with 40mm DCOE's? (CdnDub)*

Ya, I know both gotta be tuned, but with efi you type in some numbers go for a drive, if you don't like it you just change it back. Very little time and effort, painless and it only cost you the gas to that the test used.
With carbs, you have to remove them, take 'em apart, buy the jets, then do it again if it doesn't work. Way slower, pain the azz, and the cost of jets you have to eat, plus after a certain amount of removals, you need to replace the gaskets too.
Also efi is better in extreme climates and uses less fuel and is more consistent.
Next, and all following it afterwards will be efi, unless I can't find anyone to buy my bike carbs, then I have to use them for something...I find a motor for it. Also no more counter flow heads for me, what a pain in the arse, there is so little room to do anything (ie. remove carbs) with both the intake and exhaust are on the same side. Super, super tight, especially with these damn carbs, 1/8th of a turn at a time of the nuts is SLOW.


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## ABA Scirocco (May 30, 2001)

*Re: Hesitation on throttle "tip in" with 40mm DCOE's? (dohc)*

If you can't get them working right, go see my guy in Hamilton, he's got 30 years of experience setting up Webers and probably all the jets and emulsion tubes etc. you're likely to need.


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## 2L Bunny (Aug 15, 2000)

*Re: Hesitation on throttle "tip in" with 40mm DCOE's? (ABA Scirocco)*

When I ran my ITB setup (Andrews current) with SDS. I remember having to put HUGE accel enrichment values to get tip in smooth.


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## dohc (Sep 28, 2001)

*Re: Hesitation on throttle "tip in" with 40mm DCOE's? (2L Bunny)*

Ok now I'm having backfire problems. I can see a flash through the air filters. I'm not sure, but I think its running to little initial timing, because once the motor speeds up the backfire goes away. The backfire also causes hesistation, even worse then when it was lean, because now all the fuel is used up for an air filter light show.


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## antichristonwheels (Jun 14, 2001)

*Re: Hesitation on throttle "tip in" with 40mm DCOE's? (dohc)*

You make it sound like programmable EFI and be tuned on the way to work and win at the track that night. You must be better than all the professional tuners and their dynos. Since we are talking about Webers and the similar Dellortos, or Mikuni carbs, actually you can change a jet armed with only a screwdriver without removing the carb or taking it apart. It can be done in less than a minute. It's that easy. A set of Webers and a box of jets cost way less than what is spent on programmable EFI and fuel components. These things aren't for everyone, but they are not as you portray them. 


_Modified by art.clemens at 1:52 PM 12-20-2003_


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## dohc (Sep 28, 2001)

*Re: Hesitation on throttle "tip in" with 40mm DCOE's? (art.clemens)*


_Quote, originally posted by *art.clemens* »_You make it sound like programmable EFI and be tuned on the way to work and win at the track that night. You must be better than all the professional tuners and their dynos. Since we are talking about Webers and the similar Dellortos, or Mikuni carbs, actually you can change a jet armed with only a screwdriver without removing the carb or taking it apart. It can be done in less than a minute. It's that easy. A set of Webers and a box of jets cost way less than what is spent on programmable EFI and fuel components. These things aren't for everyone, but they are not as you portray them. 

_Modified by art.clemens at 1:52 PM 12-20-2003_

That wasn't what I was trying to convey at all. I was just trying to say that you don't get as dirty with fuel injection. I've tuned one motor with efi, it wasn't a cake walk at all. Infact without the wizard that came with this program, I would have spent probably at least a week just to get it running.
Also I didn't know that you could just remove the jets so easily. I haven't got a manual or anything on how to take apart these things. I'm waiting on a book. Anyway, I've balanced them and fixed all the linkages and leaks. That's about as far as I'm willing to go right now.
Lastly I'm an engineer and have come to like looking at tables and graphs rather then taking educated shots and trial and error.


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## ABA Scirocco (May 30, 2001)

*Re: Hesitation on throttle "tip in" with 40mm DCOE's? (dohc)*


_Quote, originally posted by *dohc* »_
Also I didn't know that you could just remove the jets so easily.

They main reason that Webers or Dells were so popular with racers is that they have such a wide range of adjustments and that once the intial set-up is done they are very easily adjusted at the track for the weather and track conditions of race day. They're a very slick set-up but getting your initial adjustment correct is kind of complicated, each carb has 4 pairs of jets, idle jets, pump jets, main jets and air correction jets as well as changeable emulsion tubes and venturies you need to get the combination right and the adjustments right. 
After the initial set-up, you seldom need to change pump jets or venturies. The idle jets, air correction jets, emulsion tubes and main jets can all be changed without disassembling the carb or even draining the float bowl in fact except for the idle jets, they can even be changed while the engine is idling, but for safety reasons that's not recommended.
Here's a link to give you a bit of an overview of what's involved http://hometown.aol.com/dvandrews/webers.htm but it still would be a good idea get good book on the Weber DCOE carbs and afterwards borrow a few different jets, tubes and venturies that way you could try them out and see what it you need to make your set-up work properly without spending a bundle on jets and other parts you may never use again.


_Modified by ABA Scirocco at 7:23 AM 12-21-2003_


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## dohc (Sep 28, 2001)

*Re: Hesitation on throttle "tip in" with 40mm DCOE's? (ABA Scirocco)*


_Quote, originally posted by *ABA Scirocco* »_
They main reason that Webers or Dells were so popular with racers is that they have such a wide range of adjustments and that once the intial set-up is done they are very easily adjusted at the track for the weather and track conditions of race day. They're a very slick set-up but getting your initial adjustment correct is kind of complicated, each carb has 4 pairs of jets, idle jets, pump jets, main jets and air correction jets as well as changeable emulsion tubes and venturies you need to get the combination right and the adjustments right. 
After the initial set-up, you seldom need to change pump jets or venturies. The idle jets, air correction jets, emulsion tubes and main jets can all be changed without disassembling the carb or even draining the float bowl in fact except for the idle jets, they can even be changed while the engine is idling, but for safety reasons that's not recommended.
Here's a link to give you a bit of an overview of what's involved http://hometown.aol.com/dvandrews/webers.htm but it still would be a good idea get good book on the Weber DCOE carbs and afterwards borrow a few different jets, tubes and venturies that way you could try them out and see what it you need to make your set-up work properly without spending a bundle on jets and other parts you may never use again.

_Modified by ABA Scirocco at 7:23 AM 12-21-2003_

Sweet! Thanx for the link. Only thing is I think that they have stopped making parts for Dell's long time ago. And from what I've read, the weber parts are just different enough that they won't work. I'm gonna give the damn things one last shot before I get ticked and sell the car.
A quick last question. Are DHLA's basically the same as DCOE's, only with a smaller bolt pattern?


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## ABA Scirocco (May 30, 2001)

*Re: Hesitation on throttle "tip in" with 40mm DCOE's? (dohc)*


_Quote, originally posted by *dohc* »_A quick last question. Are DHLA's basically the same as DCOE's, only with a smaller bolt pattern?

They are very similar, the DHLA is sort of a DCOE clone although the choke system on the DHLA is supposed to be an improvement on the DCOE. The Dell jets etc don't fit the Webers or vise versa but other than that, they are pretty much interchangeable in terms of manifold and linkages etc. same bolt pattern and same size. Not long ago, I came across a website selling both Dell and Weber jets and tubes, unfortunately I don't have the url any more.


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## 2L Bunny (Aug 15, 2000)

*Re: Hesitation on throttle "tip in" with 40mm DCOE's? (ABA Scirocco)*

FWIW the jets on DRLA's can be used in DHLA's. So if you can find a good aircooled shop that still used Dell downdrafts, the jets are interchangable. I haven't gotten jets from them, but http://www.dellorto.co.uk I ordered some venturi's from them, and for a very reasonable shipping they were delivered within a week.
hth,


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