Fuel economy and hesitant acceleration for 1600 dp

[DJP]

Hi All - I've got a South American re-built 1600 twin port engine in a 1971 late Beetle.

It's got a Solex H30/31 PICT carburetor and a distributor which has electronic ignition and a vacuum advance.

I've got two issues. The first is that when the engine is on its way to warming up but not totally warm there is a hesitancy in acceleration, especially going from first to second or in third on a hill. It gets there eventually but thinks about it first...

The second is that I think the fuel economy might be under par but I'm not clear what to expect from this engine/carb/distributor combo.

I'm getting 20 mpg on the urban cycle.

I'm not a skilled mechanic but I know one!

Any guidance gratefully received

[andk5591]

Does your carb supply enough vacuum for your SVDA? Probably not. Test it to be sure. Vac can unhooked - check max mechanical advance (rev to where it doesnt go any higher - should be aourn 30 degrees +/- 2degrees. Then hook up the can. Should go into the low to mid 40 degree range. If is doesnt, you have a mismatch and a different carb or distributor is on order.

Sine you are most likely improperly tuned, it will hurt you fuel economy, but how you drive also has a big impact. But 20 city is not ridiculously low. I would expect more 24ish.

Warm up depends on how well the choke is set. You can try adjusting it a little either direction and see if it improves. Mark current position and rotate the choke element maybe 1/8 or 1/4" and see what happens.
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[DJP]

[quote="andk5591"]Does your carb supply enough vacuum for your SVDA? Probably not. Test it to be sure. Vac can unhooked - check max mechanical advance (rev to where it doesnt go any higher - should be aourn 30 degrees +/- 2degrees. Then hook up the can. Should go into the low to mid 40 degree range. If is doesnt, you have a mismatch and a different carb or distributor is on order.

Sine you are most likely improperly tuned, it will hurt you fuel economy, but how you drive also has a big impact. But 20 city is not ridiculously low. I would expect more 24ish.

Warm up depends on how well the choke is set. You can try adjusting it a little either direction and see if it improves. Mark current position and rotate the choke element maybe 1/8 or 1/4" and see what happens.[/quote

Thanks for your reply! However it's a bit technical for me to fully understand. Perhaps you or someone else on the post could describe what you mean in lay terms?

I'm sure my mechanic would get it but I'd like to too!!

[baldessariclan]

In simple layman's terms, you most likely have a sub-par or undesirable carburetor + distributor combination for that engine.

If you want these cars to run well/optimally, then you've got to use good quality fuel supply and ignition components that work well together. Since these are relatively low horsepower engines, they are fairly "sensitive" to small inconsistencies & inefficiencies -- i.e. "lack of attention to detail" items that might not be so noticeable in a big V-8 engine, you'll definitely feel / suffer from in small VW engines.

All that said, if you want your car to run smoothly & with reasonable fuel economy, recommend that you (and/or your mechanic) spend some time to research and get familiar with appropriate carburetor and distributor matchup options for your engine. We're here to help -- feel free to ask further questions any time...
_________________
1971 Standard Beetle — fairly stock / driver

baldessariclan -- often in error, never in doubt...

[mjtracy]

I'm wondering if you would consider using a pict-34 carburetor? I believe it may be better matched to a dual-port 1600 than the 30 you currently have.

[DJP]

[DJP]

[DJP]

[quote="DJP"]

[Tom K.]

That distributor looks like a 009 which does *not* have a vacuum advance. The 30/31 carb and 09 distributor were both replacement parts added to many VWs over the years. The 30/31 can work well with a 009 distributor although some will say that the original combo works better.

But before throwing new expensive parts at your problem, you should first exhaust all fixes that you or your mechanical friend can carry out on your own.

That the problem occurs only during warm-up suggests that your choke is opening before your engine is hot. Is the problem worse on cold mornings in January than warm afternoons in July? This is a common problem.

How to solve? Your choke has no idea how hot your engine is. It essentially works on a timer. It will open over a fixed interval of time regardless of the temperature of your engine or the temperature in the air. If your engine is slow to warm up, then you will have these problems.

Why might your engine be slow to warm up? You might be missing a thermostat under the passenger side of the engine or two important flaps under your fan shroud. The thermostat will keep the flaps closed until the engine is warm. If these flaps are missing, it takes a very long time for engine to heat up, and of course your choke knows nothing about it.
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'70 Beetle Convertible
'71 Super Beetle Semi-Automatic: https://www.thesamba.com/vw/forum/viewtopic.php?t=714131&highlight=
'65 Ghia: https://www.thesamba.com/vw/forum/viewtopic.php?t=762478&highlight=

[DJP]

[Tom K.]

The thermostat can be viewed from the rear by looking under the engine - look for examples of pictures on line. It will either be there or will not be there.

In terms of the two important flaps - it's hard to explain over a post how to know if you have them or not. You need to reach down in front of the engine (behind the fan shroud if you are looking at the engine from the rear) and feel around for a bracket that slides left and right about one inch. If you unscrew your thermostat, then this bracket will slide back and forth easily. Try to listen for additional movement (tin on tin) when sliding this bracket. This movement would be the flaps opening and closing. But to a new person, knowing what this sounds like might be difficult. But if the entire bracket is missing, then obviously your flaps (or a least the driver side flap) are not working.

There might be another way to check for the presence of flaps - others will weigh in.
_________________
'91 Vanagon Westfalia
'70 Beetle Convertible
'71 Super Beetle Semi-Automatic: https://www.thesamba.com/vw/forum/viewtopic.php?t=714131&highlight=
'65 Ghia: https://www.thesamba.com/vw/forum/viewtopic.php?t=762478&highlight=

[Tom K.]

Regarding that brass part - are you referring to the cylindrical brass thing on the *right* (from the perspective of the camera)? That would be your fuel pump.
_________________
'91 Vanagon Westfalia
'70 Beetle Convertible
'71 Super Beetle Semi-Automatic: https://www.thesamba.com/vw/forum/viewtopic.php?t=714131&highlight=
'65 Ghia: https://www.thesamba.com/vw/forum/viewtopic.php?t=762478&highlight=

[bluebus86]

before doing carb tuning of any sorts, some other things need be sorted out first. Recall carbs run off vacuum, as does the advance curve.

a...for correct vacuum, valves must be correctly adjusted.

b...for correct vacuum, cylinders must not be leaky, thus a compression test and or a leak down test is required, these tests should only be done with correctly adjusted valves.

c... Intake system must be leak free, this is tested with engine at idle, and squirting a flammable chemical such as aerosol canned carb cleaner at the intake joints at the head, carb base, vacuum hose joints and along length of the hoses, vacuum can on the dizzie, and intake boots on dual port manifolds. if idle speed changes with a corresponding squirt of carb cleaner, that joint is suspect for a leak.

d...other things to consider prior to carb tuning are fuel pump pressure, volume as these can effect float bowl level, and finally the float bowl level itself.

e.. Timing and dwell should also be set prior to carb tuning

Good Luck, Bug On!
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[baldessariclan]

[DJP]

[ashman40]

Ok, rather than guessing... please find the part# off the body of your distributor and post here so we can confirm the model of your distributor.

My guess is you have a mechanical-only "009" which will have the Bosch part# = 0231 178 009
Here is an example of the Bosch part# you are looking for on the distributor:

OE VW distributors will have both a Bosch part# AND a different VW part#.

Once you have the distributor part# (some will have a VW part# AND a Bosch part#) look up the distributor details here:
http://www.type2.com/~keen/ignition.html


If you are looking for the best performance/economy with your H30/31 carb you probably want to match it with one of the following:

SVA distributor - VW part# ending in 205K/205L/205M/205T ('67-'70 model year cars)

SVDA distributor - VW 043-905-205, Bosch 0231 170 034
(most aftermarket SVDA distributors are patterned after this distributor)

If you have a mechanical-only (no vacuum canister) "009" distributor it can work with the H30/31 but you will not get the best performance/economy.

The SVA distributor has a large diameter vacuum canister as pictured below and will be connected to the left side vacuum port (venturi vacuum) on your H30/31 carb ("A" in the bottom pic).

The SVDA distributor has a smaller diameter vacuum canister as pictured below and will be connected to the angled rear-facing bottom right vacuum port (ported vacuum) on your H30/31 carb ("D" in the below pic).

_________________
AshMan40
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'67 Beetle #1 {project car that never made it to the road }
'75 Beetle 1200LS (RHD Japan model) {junked due to frame rot}
'67 Beetle #2 {2019 project car - Wish me luck!}

[ashman40]

[viiking]

[bluebus86]

[DJP]