<VV> Turbo Motor Cycling
tony.underwood at cox.net
Sat Nov 2 09:32:11 EDT 2019
> On 10/30/2019 11:11 AM, Brian via VirtualVairs wrote:
>> While on the engine stand it ran flawlessly. Now that is installed
>> in the car and the Turbo with his carburetor is installed there is a
>> cycling problem. The engine fires instantly and with the choke
>> disconnected idles but the idle fluctuates from about 690 RPM to
>> about 920 RPM. The cycling is slow in other words it will run for a
>> couple of seconds may be as much as 30 seconds and then the idle will
>> jump either up or down.
>> As mentioned all the parts are stock to include the camshaft. Timing
>> is set at 24° as per the shop manual. Not being a Turbo guru I am
>> stumped. Is it possible that this cycling is caused by an improper
>> setting of the idle mixture or is there some other issue?
> I have seen turbo cars run rough with erratic idle caused by too much
> fuel pressure. Several times. You might wanna try a fuel pressure
> regulator and set it for 2.5-3 lbs and see what happens. It's odd
> that some Carter HVs are fine with the "stock" fuel pressures and some
> simply are not. One Spyder I worked on for a friend simply would NOT
> idle correctly with more than 3 lbs of fuel pressure, and that was
> with a freshly overhauled carb. A pressure regulator fixed it.
> Another Spyder an old girlfriend owned had a similar problem... I
> cheated on that one and cobbled the fuel pump spring to drop the
> pressure via "hit or miss", got lucky and hit it the first time. The
> Spyder coupe used to own (with '66 Turbo RL engine) ran fine with the
> factory mechanical pump unmodified and without a pressure regulator.
> Variances in fuel inlet valve designs?
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