Weber/Dell Tuning
Posted: Fri Aug 12, 2005 2:30 pm
I can't post on LotusElan.net, probably because I never registered
for it, but I forget.
Three items on the rolling road tuner posting:
1. If your account is accurate, any shop that wastes your time like
that and still takes any of your money needs to be very publicly
exposed. People need to know to avoid it. This would hinge on
whether you were very clear your carbs were Dells and not Webers.
2. For your hour, you should have gotten a printout showing your AF
ratio throughout the rev range of the dyno test. In my experience,
this is 3000 to redline, and includes the progression from idle to
main. Your distribution along this progression is important
information for tuning, although it is almost surely the case you
need to attend to idle jets first.
3. On Webers, and I'm almost certain Dells as well, the jet number
is its diameter. For a fuel jet, larger is richer. For an air
corrector, larger is leaner. Given your current status, I don't see
any reason to borrow a 58 jet.
If you go to the Europa Yahoo site, you'll find in the archives some
excellent Weber advice which I'm pretty sure is the same for Dells.
I used it to straighten out my Europa's 45DCOE, which was fuel
starved at the top of the idle progression (steady-state highway
speed) by a too-small idle jet.
The other piece of input I have is that air correctors have a small
impact relative to fuel jets. You should be able to get your rich
condition straight with just the right fuel jets. The air correctors
are fine tuning in my understanding; your problem is very coarse.
The Haynes Weber book is a valuable tool, also covering Dells. Get
one. It also covers Strombergs and SUs.
I know nothing about tuning the Twincam, but I'm surprised at your
jet sizes. A 1565 Europa Renault runs on a single 45DCOE with 45F8
jets stock (I'm running 50F8) Your setup is permitting twice the
fuel through the idle jets on about the same displacement for maybe
20% more horsepower if your engine is near-stock. That just doesn't
seem right, and jives with a very rich mixture.
I've found that if you have a good feel for the engine's happiness at
various rev levels, and understand the progression circuit, you can
do very well with drive-and-fiddle by yourself. The extra carb will
complicate this a bit, and you MUST have a good method of
synchronization, which can be your ear if it's a good one.
If your tuner is trying to make you buy all the fiddling hardware
anyway, I'd wait to hit the rolling road again until after you think
you've got it about right. The real value of a professional tuner
should be that he has all the tuning bits and only charges for the
ones you wind up with, and can do the job faster than you because of
his experience. You can get there; just remember to chart your
changes along the way so you can get back to safe running if you
stray too far. The joy of the Weber design is how easy it is to make
major jetting changes in minutes. The minor headache is the wide
degree of configurability, which is baffling only if you don't do
things in an orderly manner.
Doug Nicholls, 54/1822
for it, but I forget.
Three items on the rolling road tuner posting:
1. If your account is accurate, any shop that wastes your time like
that and still takes any of your money needs to be very publicly
exposed. People need to know to avoid it. This would hinge on
whether you were very clear your carbs were Dells and not Webers.
2. For your hour, you should have gotten a printout showing your AF
ratio throughout the rev range of the dyno test. In my experience,
this is 3000 to redline, and includes the progression from idle to
main. Your distribution along this progression is important
information for tuning, although it is almost surely the case you
need to attend to idle jets first.
3. On Webers, and I'm almost certain Dells as well, the jet number
is its diameter. For a fuel jet, larger is richer. For an air
corrector, larger is leaner. Given your current status, I don't see
any reason to borrow a 58 jet.
If you go to the Europa Yahoo site, you'll find in the archives some
excellent Weber advice which I'm pretty sure is the same for Dells.
I used it to straighten out my Europa's 45DCOE, which was fuel
starved at the top of the idle progression (steady-state highway
speed) by a too-small idle jet.
The other piece of input I have is that air correctors have a small
impact relative to fuel jets. You should be able to get your rich
condition straight with just the right fuel jets. The air correctors
are fine tuning in my understanding; your problem is very coarse.
The Haynes Weber book is a valuable tool, also covering Dells. Get
one. It also covers Strombergs and SUs.
I know nothing about tuning the Twincam, but I'm surprised at your
jet sizes. A 1565 Europa Renault runs on a single 45DCOE with 45F8
jets stock (I'm running 50F8) Your setup is permitting twice the
fuel through the idle jets on about the same displacement for maybe
20% more horsepower if your engine is near-stock. That just doesn't
seem right, and jives with a very rich mixture.
I've found that if you have a good feel for the engine's happiness at
various rev levels, and understand the progression circuit, you can
do very well with drive-and-fiddle by yourself. The extra carb will
complicate this a bit, and you MUST have a good method of
synchronization, which can be your ear if it's a good one.
If your tuner is trying to make you buy all the fiddling hardware
anyway, I'd wait to hit the rolling road again until after you think
you've got it about right. The real value of a professional tuner
should be that he has all the tuning bits and only charges for the
ones you wind up with, and can do the job faster than you because of
his experience. You can get there; just remember to chart your
changes along the way so you can get back to safe running if you
stray too far. The joy of the Weber design is how easy it is to make
major jetting changes in minutes. The minor headache is the wide
degree of configurability, which is baffling only if you don't do
things in an orderly manner.
Doug Nicholls, 54/1822