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Carburetors and Carb Tuning.. All info about old school carb set ups..

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Old 01-02-2011, 01:10 AM   #1
TheBlack7
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Default Weber, Dellorto, Mikuni

First off I am a carb retard and just ordered a Mikuni 44PHH for my 83 rx7.
I was wondering what the differences in these carbs are as far as powerband, gas mileage, durability, ease of tuning, etc.






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Old 01-02-2011, 09:27 AM   #2
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We'll assume your talking about comparing a Weber DCOE and Dellorto 48 DHLA.

Power band.

The Mikuni will have less top end due to its size than the Dell or DCOE.
Otherwise it should repond about the same thru the rest of the power band.
If you use a wraparound intake (RB or Lake Cities) the torque curve will
be low enough to make the carb very streetable. If you use the short
side intake from Atkins it will move the torque up about 1000 rpms.

Gas Mileage.

Really? You care You can expect around 17/22 for a stockport with a
good tune on the carb.

Durability.

As long as you use good fule filters and a correctly size air filter (allowing
at least 1.5 inches above the top of the air horns) these carbs will all last
a long time. Longer than the engine or car I'm sure.

Ease of tuning.

The Dell is the easiest and have the most adjustments. You can change the
jets while the car is runnning The Weber and the Mikuni are almost as
easy but require you to shutdown to manipulate the jets.

With all the carbs the big thing to address is setting up the fuel delivery to
be at the correct pressure and flow. They all operate at fairly low pressures
but require a good 40 gph pump. The Dell likes pressures at 2.5 psi, the
Webers like 3.5 to 4 and I think the Mikuni are the same. This means you will
probably need to get a good fuel regulator (return type recommended).
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Old 01-02-2011, 01:17 PM   #3
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thanks for that!
My mikuni is gonna run on a wrap around manifold but are there any measures that can be taken to effectively increase the top end? (tuning, jetting). It still needs to be streetable but for me above 5000 rpm is where I'd like the power to be focused.
also how do you like the carter pump if you don't mind me asking?
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Old 01-02-2011, 01:36 PM   #4
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You can change main jets in a Weber while it's running. I've done it, though it's really more of a novelty than anything useful. The biggest difference between Weber and Dell is that it's much easier to find Weber jets.

The problem with the Mikuni is that it's just a small carb. It's never going to have the top-end of a larger Weber or Dell.
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Old 01-02-2011, 02:06 PM   #5
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Quote:
Originally Posted by PercentSevenC View Post
You can change main jets in a Weber while it's running. I've done it, though it's really more of a novelty than anything useful. The biggest difference between Weber and Dell is that it's much easier to find Weber jets.

The problem with the Mikuni is that it's just a small carb. It's never going to have the top-end of a larger Weber or Dell.
so even a stockport 12a won't be entirely satisfied by a 44 mikuni at top end?
I don't get it, isn't it still more than enough fuel flow to meet the cars needs?
(assuming jetting is correct, etc.)
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Old 01-02-2011, 02:59 PM   #6
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It's not fuel flow. It's air flow. A smaller carb will not deliver as much air as a large one given an equal pressure drop. For a stockport 12A that's street-driven, the Mikuni may be all you need to give you a nice, usable powerband. But a larger, freer-flowing carb will give you more peak power if that's what you're after.
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Old 01-02-2011, 08:38 PM   #7
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thanks!
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Old 01-03-2011, 06:05 PM   #8
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The Carter pump works fine but its noisy. I need to remount with more rubber
to isolate it better.

The Mikuni 44 will not give you the top end your after, you need to go up a
size to a 48. Weber or Dell will both work fine. Either way its the choke size
thats key to your engines performance. If your choke is sized wrong, idle
preformance will be crappy to non-existent.

Yeah, the changing the jet thing while running is a kind of parlor trick. Its fun
to do in front of a 4 barrel guy.
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Old 01-04-2011, 08:52 AM   #9
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I have a question or two as well.

Talking Webers; is a 48 DCOE preferred over a 48 IDA?

What are the benefits/shortfalls of each?

Assuming a stock port 12a of course.
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Old 01-04-2011, 11:11 AM   #10
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The IDA will move the torque curve up a bit and will make most hp and torque
higher up the range. May have some drivability issues due to this but with a
stock port and the right chokes it would work ok.

The DCOE will normally use a wrap around intake that places the carb velocity
stacks pointing towards the oil fill tube. This longer intake will move the torque
down in the range and drivability will be easier to obtain. Also DCOE can be
outfitted with a cold start assist (like a choke), so its a more street friendly
carb.

The IDA will give you the maximum power but just may not be where you want
it and the DCOE will make it an easier tune for a DD the car. Not to say an IDA
can't be a DD carb but it will take a bit more fussing about to get it right and
to live with.
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Old 01-04-2011, 12:50 PM   #11
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If I could do it over again I'd get an IDA. The DCOE with the wraparound manifold is kind of a pain to deal with.
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Old 01-05-2011, 10:18 PM   #12
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Quote:
Originally Posted by t_g_farrell View Post
The IDA will move the torque curve up a bit and will make most hp and torque
higher up the range. May have some drivability issues due to this but with a
stock port and the right chokes it would work ok.

The DCOE will normally use a wrap around intake that places the carb velocity
stacks pointing towards the oil fill tube. This longer intake will move the torque
down in the range and drivability will be easier to obtain. Also DCOE can be
outfitted with a cold start assist (like a choke), so its a more street friendly
carb.

The IDA will give you the maximum power but just may not be where you want
it and the DCOE will make it an easier tune for a DD the car. Not to say an IDA
can't be a DD carb but it will take a bit more fussing about to get it right and
to live with.
chokes? I thought these carbs had none? at least my mikuni doesn't.
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Old 01-05-2011, 10:19 PM   #13
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again thanks for the help guys. without the internet i would be hopeless hahaha
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Old 01-05-2011, 11:39 PM   #14
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I used to have a Mikuni on a street ported 12A. My best friend had a 48 IDA on a street ported 13B. Not much difference in drivability for daily, which we both did. If I was doing it over again, I'd do the Weber 48 IDA for the top end power.

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Old 01-06-2011, 01:48 AM   #15
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Quote:
Originally Posted by TheBlack7 View Post
chokes? I thought these carbs had none? at least my mikuni doesn't.
The word "chokes" is often used to describe the main venturis.
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