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.

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 :lol: 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 :D 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).

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?

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.)

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.

thanks!

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.

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.

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.

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.

chokes? I thought these carbs had none? at least my mikuni doesn't. :dunno:

again thanks for the help guys. without the internet i would be hopeless hahaha

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.

Jack

The word "chokes" is often used to describe the main venturis.

I have the mikuni 44PHH side draft carb on my S5 streetport and it is easy to change the jets out but the size is a little small but it still rips pretty good but with this cold winter air I am having a hard time adjusting the air because it leans out too much in the upper power band but it makes great mid range. Its hard because I hate dealing with wolf creek racing for jets, the guys is an ass hole. You would think you would be nicer to someone who is giving you money for relatively little work.

I cant afford a weber 50 DC SP unfortunately but thats what I need

I also run about 4.5psi of fuel pressure for the mikuni, it seems to like it.

they do make a mikuni 50PHH but you can only buy them in pairs :(

what fpr are you running for 4.5 psi?

http://www.summitracing.com/parts/AEI-13301/

its the aeromotive 13301

I run a stock T2 fuel pump.

my FPR is about 10" away from the carb.

This is a thread that I've been looking for. I bought a Mikuni (44) with 12a manifold. The folks that I spoke with said it was good to 200bhp. I plan on mating it to a 4pt Renisis. I'm getting good at building adapting manifolds and Carbs. I'll post picks in the 1st gen section. (it's going in a '79 SA)

Now I am looking for carb kits for an old school 13B 4 port.

I think jfaplanet has a Dellorto on his Repu, but not sure. It rips with that carb, so I was considering those.

However, a couple of locals have the RB kit and their cars run pretty damn good as well. Although, the Dell's look a shitload cooler ;)

you should be able to get proper afr's with your existing carb. to richen up the top end try an emulsion tube designed to add more fuel at a higher rpm. or in the mean time try a smaller air corrector jet

I dont have the independent type jet block (e-tube) so I think I'm stuck with what I got but I did manage to get a smaller air jet. so whenever the roads are plowed I can take the rx7 out (with studded snow tires :) )

finally got the new setup up and running. mikuni 44 w/ carter pump and holley 1-4 psi fpr and the car is unbelievable. shreds tires up through third gear! I love my mikuni! one question though, around 2k rpm it falls flat on its face HARD. above and below 2k it runs great though. u guys think its a fuel pressure thing?? or should i purchase some new jets?

Check to make sure your AP is making a good squirt. It should be part of what helps you get thru that progression from idl into WOT.

This is only my second post so apologies if it's a bit premature:

I've been running mikunis/solexes for years on my toyotas. I love 'em. What t_g_farrell pointed out is where I would check too: your accelerator pump sizes.

The size indicators can be a bit misleading. Just to give you an idea a 40 pump jet will squirt a larger amount at a shorter period of time over a 35. Make sense? So, it sounds like the progression from pilot to mains could be a lean bog due to either too short of a large squirt or to little of a long squirt.

I'd try going up a larger size though it'll be a shorter squeeze. It might be enough to straighten out that dip.

It could be balanced with a .5 step up on idles coupled with a step up on the pump jet.

adjust your float level

well i'v read all your posts and side draft carbs don't work well on N/A rotarys .44mm is to small for starters, 48mm and up .Down draft webers are some of the best carbs for drive ability and simplicity .Don't waste your time with side drafts the max performance will always fall short .I know you already own the side draft , they suck ......start with dyno runs ,holly will produce an average of 7 more hp over the down draft weber , but the weber is the better carb for corner carving (no starvation due to fuel slosh in the float bowl).Please sell your side drafts you will not get what you want in terms of performance.

Your quite right on absolute performance but the side drafts with a wrap around
manifold gives you better torque down low for the street and makes it much more
drivable. Its all in what your looking for. You can't just say one is better than
the other, it depends on the uses and the drivers intentions.

I also agree that the 44 is a bit small for anything but a stock port 12A and even
then you will have some tuning to get it to a reasonable level. It will work but maybe
not as well as a 48.

sure ,if you want torque a wrap around will sort of work , but in my experience tuning will never be right.I would rather use the stock carb and save my $.The wrap around is not that affective , if you want more torque just put spacer plates between your carb and intake ,the longer the runner the lower the torque curve.

With a Nikki? I'd like to see that, post it up along with dyno sheets that show
how well it works that way.

nickki is a stock carb another stock carb is a zenith ,if you want dyno print outs go try it for yourself .Keep playing with those side drafts ,and waste your time.If you don't believe me call Racing Beats,the tech line will tell you they dont work right for a rotary motor .And raising a stock or aftermarket carbs height will change any engines torque curve lower( piston or rotor ),thats simple intake runner theory.