kindly I have the EMPI 38 EGAS Carburetor Kit part number 47-0645 for type 4 engine 2 liter engine
also i have installed Fuel Pressure regulator part number 9102 and put it on 2 as recommended since i am using a mechanical fuel pump
the problem is that i have a lot of hesitation from 1000 to 2000 rpm
please advice me if any setup must do in order to fix this problem
thank you
Also My friend did buy the type 1 kit same carburetor jetted for 1600 engine and having the same problem
anyone have some tips regarding this issue?
EMPI 38 EGAS Carburetor Kit
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Marc
- Moderator
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Re: EMPI 38 EGAS Carburetor Kit
As this is the Type I forum, let's address your friend's setup first. Did he install the heat riser tubes which come in the kit? They're less efficient than those on a stock intake manifold, and aftermarket exhaust systems are notorious for furnishing less preheat flow than a stock muffler, but every little bit helps.
Single 2-bbl setups, as a rule, will have a hesitation on acceleration at lower RPM. It's not so much due to the type of carb or distributor, as the basic physics of what's going on in the manifold. The manifold runners are typically larger than needed, even for high-RPM and/or a larger engine. A smallish engine just won't have the flow velocity at low speeds to maintain manifold vacuum as the throttle is opened. When vacuum drops off, fuel condenses on the walls of the manifold and the mixture arriving at the cylinders is temporarily too lean to burn. When the condensed fuel eventually dribbles down to the cylinders, it's too late to help and in the form of droplets which are too big to burn completely.
The accelerator pump exists to compensate for this effect by squirting in some "extra" fuel as the throttle is opened, making the mixture rich enough to burn. It only acts briefly, long enough to keep the engine from stumbling - as it gains speed and the flow through the manifold goes up the condition goes away naturally.
Increasing the volume and/or duration of the accelerator pump "shot" will usually help; so will running richer idle jets since they control the mixture in the transition range between the idle circuit and when the main system takes over (that can be up to ~2500 RPM). Both tactics reduce your fuel economy and tend to wash down the cylinderwalls, shortening their life, and contaminate the oil with gasoline.
A lean mixture is more likely to ignite and have time to burn if the spark advance is increased. Too much of that can cause preignition which is hard on the piston rings and pistons - even if you can't hear any "pinging" it can still be happening, damaging the engine, so never "road-time" or "time by ear" since you'll assuredly end up with too much advance. A distributor which can increase the spark advance momentarily as the throttle plate opens will usually help - but for it to work properly the carburetor must have a "ported" vacuum tap which provides the correct signal, you can NOT use manifold vacuum for this as that would cause excessive advance at idle.
Some non-stock distributors have a ported vacuum tap that's compatible with a stock vacuum+centrifugal-advance distributor; I don't know if EMPI's clone of the Weber DGAS has that feature or not and will need to research it.
Now, about your Type IV engine. All of the above considerations apply, but you have ZERO manifold heat and intake runners which are several times larger than they should be. With stock fuel injection there's nothing inside them but air so the condensation issue never arises, but with a carb it becomes a big problem. IMO you'll NEVER totally be rid of a hesitation without reducing the runner size and providing some heat to the intake, but you may be able to make it tolerable by fiddling with the jetting/accelerator pump and possibly the type of distributor. The plenum chamber needed to make two barrels feed 4 cylinders reduces the vacuum seen by the carb compared to an independent-runner style which at least isolates each barrel so that it only "sees" 2 cylinders (your friend's setup should have an IR manifold, but the 38mm carb is on the large side for 1600cc so the vacuum signal is still rather weak - with a plenum-style manifold his would probably be worse than yours).
You'd both be better off with a dual-carb setup, even dual 1-bbls, since by putting the carbs closer to the heads the manifold size and temperature become less critical. Leave the single 2-bbls to the offroad racers, they work OK for them since they're usually driving at high enough RPM to be past the "flat spot".
Single 2-bbl setups, as a rule, will have a hesitation on acceleration at lower RPM. It's not so much due to the type of carb or distributor, as the basic physics of what's going on in the manifold. The manifold runners are typically larger than needed, even for high-RPM and/or a larger engine. A smallish engine just won't have the flow velocity at low speeds to maintain manifold vacuum as the throttle is opened. When vacuum drops off, fuel condenses on the walls of the manifold and the mixture arriving at the cylinders is temporarily too lean to burn. When the condensed fuel eventually dribbles down to the cylinders, it's too late to help and in the form of droplets which are too big to burn completely.
The accelerator pump exists to compensate for this effect by squirting in some "extra" fuel as the throttle is opened, making the mixture rich enough to burn. It only acts briefly, long enough to keep the engine from stumbling - as it gains speed and the flow through the manifold goes up the condition goes away naturally.
Increasing the volume and/or duration of the accelerator pump "shot" will usually help; so will running richer idle jets since they control the mixture in the transition range between the idle circuit and when the main system takes over (that can be up to ~2500 RPM). Both tactics reduce your fuel economy and tend to wash down the cylinderwalls, shortening their life, and contaminate the oil with gasoline.
A lean mixture is more likely to ignite and have time to burn if the spark advance is increased. Too much of that can cause preignition which is hard on the piston rings and pistons - even if you can't hear any "pinging" it can still be happening, damaging the engine, so never "road-time" or "time by ear" since you'll assuredly end up with too much advance. A distributor which can increase the spark advance momentarily as the throttle plate opens will usually help - but for it to work properly the carburetor must have a "ported" vacuum tap which provides the correct signal, you can NOT use manifold vacuum for this as that would cause excessive advance at idle.
Some non-stock distributors have a ported vacuum tap that's compatible with a stock vacuum+centrifugal-advance distributor; I don't know if EMPI's clone of the Weber DGAS has that feature or not and will need to research it.
Now, about your Type IV engine. All of the above considerations apply, but you have ZERO manifold heat and intake runners which are several times larger than they should be. With stock fuel injection there's nothing inside them but air so the condensation issue never arises, but with a carb it becomes a big problem. IMO you'll NEVER totally be rid of a hesitation without reducing the runner size and providing some heat to the intake, but you may be able to make it tolerable by fiddling with the jetting/accelerator pump and possibly the type of distributor. The plenum chamber needed to make two barrels feed 4 cylinders reduces the vacuum seen by the carb compared to an independent-runner style which at least isolates each barrel so that it only "sees" 2 cylinders (your friend's setup should have an IR manifold, but the 38mm carb is on the large side for 1600cc so the vacuum signal is still rather weak - with a plenum-style manifold his would probably be worse than yours).
You'd both be better off with a dual-carb setup, even dual 1-bbls, since by putting the carbs closer to the heads the manifold size and temperature become less critical. Leave the single 2-bbls to the offroad racers, they work OK for them since they're usually driving at high enough RPM to be past the "flat spot".
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Shadyabinader
- Posts: 11
- Joined: Tue Aug 15, 2017 12:35 pm
Re: EMPI 38 EGAS Carburetor Kit
Than you Marc for your reply.
i guess i will try a distributor with single vacuum since the carb has an outlet for distributor vacuum
i am using this carb on a baja for off-road and street driving
thanks alot
i guess i will try a distributor with single vacuum since the carb has an outlet for distributor vacuum
i am using this carb on a baja for off-road and street driving
thanks alot
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Shadyabinader
- Posts: 11
- Joined: Tue Aug 15, 2017 12:35 pm
Re: EMPI 38 EGAS Carburetor Kit
I was thinking of installing a single carburetor solex 34 pict 3 without a ventury tube on a 2 liter type 4 engine
has anyone did this thing ?
what is the modification of the jets ?
does it work fine ?
has anyone did this thing ?
what is the modification of the jets ?
does it work fine ?