Wim,Yes, E fuels need richer JETS as pure ethanol/ alcohol optimum a/f ratio is on order of 9:1 compared to gasoline with optimum of 14.7:1. The lower E mix (E15 compared to say E85, the closer the optimum a/f mix will be to requirement of 14.7:1 for gasoline. This means that when using an E85 fuel that engine will be running way lean with jets & needles designed for use with gasoline, Resulting in bad emissions from incomplete combustion, loss of potential power(flat spots in Rpm range, etc. Plus to a lesser extent if using E 15. Engines will fire off & run over a wide range of a/f mixtures. Just not in most desirable range for power/economy & minimum emissions. At altitude there is less o2 in air resulting in lean burn a/f mix, therefore richer (bigger jet) is required to regain lost power from lean a/f mix.As far as needle size is concerned, shape of needle basically adjusts adds fuel to more closely optimize a/f ratio to accommodate additional power demands of engine as RPM increases & of more air is being pumped thru carb. at atmospheric pressure. Perhaps an overly rich Needle would tend to accommodate low % E- 15 fuels & driving at altitudes of < than 5k ft. Testing with o2 sensor required to confirm.Very elegant. With modern fuel injected daily drivers the hocus pocus is adjusted via onboard computer with input from o2 Sensors in exhaust system.
-Bill HyattSent from my iPhone
On Jul 17, 2019, at 8:08 AM, CLIVE SHERRIFF
csherriff99@gmail.com [mg-tabc] mg-tabc-noreply@yahoogroups.com> wrote:
Wim,
My reading of today's fuels, and the experiences of many, is that the standard ES needle gives too weak a mixture on the XPAG engine. So probably an ES is good at altitude where a weaker mix is an advantage.
I wonder also, if people having problems might be using a wrong heat range spark plug ?
CliveOxford, UK
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On Wed, 17 Jul 2019 at 12:18, 'Wim Jetten'
jetten@bluewin.ch [mg-tabc] mg-tabc-noreply@yahoogroups.com> wrote:
[u][/u]
[u][/u] [u][/u]The thread on vapour lock developed into a discussion on the need for richer needles when using modern fuels (e.g. with 10% ethanol). The choice of richer needles is large. But which one to use? [u][/u][u][/u][u][/u] [u][/u]I have a TC with a standard engine and standard H2 carburettors. So far I have been happy with the standard ES needle. I never had the impression that there was a problem with this needle, but maybe there is a better choice.. You simply don t know what you don t know. I use my car mostly between sea level and 1500 m altitude. But very occasionally I take the car to higher altitude, max. 2500 m altitude. So far I have been happy with the standard ES needle. I never had the impression that there was a problem with this needle, but maybe there is a better choice. You simply don t know what you don t know.[u][/u][u][/u][u][/u] [u][/u]I am therefore not asking for a suggestion of possible richer needles, but am interested in actual experience with specific needles.[u][/u][u][/u][u][/u] [u][/u]Wim Jetten[u][/u][u][/u][u][/u] [u][/u]TC 2399[u][/u][u][/u]
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