Any Weber 45 DCOE tuners out there???
 

Last week I installed a used 45 DCOE and RB Dual exhaust on my 85 GSL (stock 12A). I used a Weber pump, which claims factory set to 6 psi. I installed a holley reg and guage to lower the psi to 2.5 psi (or so).. I followed lean best idle procedures from scratch and she fired right up. It revs smooth and idles ok, but a little hesitation. I checked the pressure gauge and the damn Holley regulator was barely reading 1. I tried to increase the pressure- no change. I mean I really adjusted that damn screw, let her sit running for a while, no change....I road tested her and found acceleration was pretty good but cruising steady in any gear, at any speed I experience Fumblin, bumblin, stumbling..(Fuel Starvation???)..
I switched the regulator to a Malpassi Fuel/Filter King (which the guy I bought it from was running), used an old 60 psi gauge, and she was dead on at 2.5-3psi. I took the car out again, same damn thing..stumble and hesitation..I'm confused as hell. I checked the jets etc.. and I'm using the following:

F-11 E tube
F9-60 idle jet
175 Air correction jet
180 main jet
85 pump jet

Oh and another thing I noticed- the intake manifold is hot..really hot. I remember 10 years ago when I had a Mikuni carb set up that sucker was ICE cold... weird... Sorry about the book, but I'm confuzed???:confused:

well ... if nothing else, i would suspect a pressure problem first simply because i'm not sure about gauge accuracy.

it might be worth your while to look into getting an EGT or AFM gauge to assist in the tuning in order to take some of the guesswork out of it. the other thing would be to hunt down an accurate pressure gauge. i know there were a few threads here that had links to some industrial-grade gauges, so run a search and see if you can find one.

good luck.

Well i've got 2 guages at my disposal, the Holley and this older 60psi one (which is on loan from a mechanic friend). He swears it reads balls to the wall accurate.
I was thinking about getting a bung welded for an o2 sensor and AFM but have read in some threads that their accuracy is questionable as well. I figured because this is a stock port 12A and just a simple 45 DCOE, that ear and butt tuning should get get me pretty damn close. I would definately add the AFM if I ported and added an IDA or something like that.
I'm going to take another look at my pump and lines and see if there is any binding going on..Maybe take a reading from the outlet side of the pump to see if it shows 6psi (factory settings) to check gauge accuracy.

Any one run the 45 DCOE with these jet settings? Any recommendations?

an air/fuel meter will *really* help you tune the carb rather quickly. worked wonders with my dellorto and 12a streetport/lake cities manifold.

sure, a wideband O2 sensor is much more sensative, and more costly. But the $25 O2 sensor at local parts store works good enough ladies and gentlemen.

Re: Any Weber 45 DCOE tuners out there???
 

Well, I cant check for you as I said in my PM since my car was stolen, but if I recal correctly, I was running:

F-11 E Tube
F9-65 Idle Jet
160 Air Correcto
170 Main Jet*
45 Pump Jet**

* I know I had a 170 main and wanted to try a 160 or 165. I know that 180 made my car run worse than the 170, but the next size down I had was a 145, and that was WAY too small.

**Im not sure on this, I just think thats what it was...

I do however know for a fact that my intake manifold got ice cold as you described. Ive actually had frost form on it before. As for my fuel pressure, 3 PSI seemed to work well for me. I tried 3.5 PSI, but it would overflow out of the float vent hole too often. I never really messed with the fuel PSI level, mostly because I knew the jetting still needed fine tuning. Anyway, I hope that helps. I wish I could offer more, but my car is MIA :(.

~T.J.

Yeah TJ- I hope you get her back.

I got a weber 45 on a stock port and I'm going to try tuning it as soon as I get the oil leak fixed. Which will be tomorrow. I'll write down my jet sizes and what not.
My manifold is really cold also, even when the engine is hot. That tells me that it's running rich, but I'm no tuning expert. Seems to me it should be warm, but not ice cold. I dunno, tho

Paul Yaw has got the art of fuel regulation tuning down to a science! If you want a *real* balls-to-the-wall accurate guage, and a write-up of why and how other guages are innaccurate, check these pages below.

First off, he's got a great writeup on why you need a good fuel regulation system, and what you need to do to get one:
http://personal.riverusers.com/~yawpower/fueldel.html

I like his title "Fuel Delivery - Get it Right or You're Screwed!".. it's pretty definitive

and the page where he has his prices listed, (again with some more info)
http://personal.riverusers.com/~yawpower/access.html

If you peruse his site you'll find that this guy really does know what he's talking about. He also modifies nikki carbs for different race classes and "all out performance" ones too, not that you need one now, but it's nice to know that he's got a flowbench and everything. That way you *know* he's got fuel delivery in his considerations.

Jon

The 60F9 is really small for your set up, go to a 65F9 and see what happens. I bet your air bleed screws are out 3 or more turns, are they??

Ryan

PS. your will have to re-tune the air bleed screws. Good luck

I have a 48 dcoe that does the exact same thing. I have yet to figure it out either. I have messed with all the jets and the fuel pressure. I am stumped.

Air bleeds are about 1 1/2 - 1 3/4 turns out.. I will try the 65F9 to see what happens. I also need to get under the car and check out the fuel pressure on the outlet side of the pump. My weber pump is a cylinder type like the stock one, albeit longer. I used the stock mounting points but fear the hoses may be binding.. This could be screwing me a bit too. Hopefully its reading 6psi which would be dialed down by the regulator. I could definately use a good gauge as well. I'm trying to contact YAW to get a hold of his gauge..

Good luck getting ahold of him, lol.

~T.J.

T.J.- How well did / does your Holley pressure reg and gauge work (I mean- did it hold a steady prressure, reading during idle and higher throttle?

It seemed to work ok...It would read the pressure faily well, and it would change according to the regulator being changed, but I have no idea how accurate it was.

~T.J.

Hmmm. My first set up with the Holley reg and gauge showed little to no change during idle/acceleration, reading at like .5 - 1.0 psi..It only spiked up if I pinched the return fuel line...
My original thought is that a fuel line somewhere near the pump is pinched or binding, but that would cause my pressure to increase, right?? The volume would drop, but pressure would go opposite.. Man, I've gotta crawl under there soon..(Been busy at work). I'm also gonna order some spare jets and stuff to tinker..You folks recommend RotaryShack?

I'll go and check my jets when I'm next in the garage.

2 questions though, what chokes do you have? People put 40's in for top end, but that can cause problems low end.

Secondly at what RPM do the stumbles occur? I have a pretty good idea of what your problem is.

I have not measured the chokes yet.. The stumble/hesitation occurs when I cruise in any gear pretty much above 3,000rpm. I have not touched float level or any of the jets that came with the carb (which someone had installed on a stock 12A). The jet sizes are listed in my thread starter. Any suggestions are appreciated!!

We need choke size, as jetting recommendations are pointless without them.

When cruising on part throttle you are generally still on the idle circuit (mind you my idea of cruise is anything under 100mph, but thats british motorways for you :-)

I suspect that you are seeing the classic progression problem that occurs with Webers. If I have a few mins tonight I'll run through the basic checklist you need to follow to see if this is the case.

Bill

Couple of quick notes. Please excuse if you know all of this but I am assuming that you grew up with holleys not webers.

Most important is the butterfly position at idle. This should be so that the slightest movement uncovers the first progression drilling, This is easily eyeballed by taking the progression cover off. IF this is wrong adjust it first. If you have newer DCOEs then you have idle air screws on each body to balance the flow.

Once that is right you have to look at the progression. A stumble at idle says that either your idle circuit is cutting out too early or your main jets are coming in too late. With a friend looking down the progression holes (engine off) open the throttle until the last hole is uncovered. If this is less throttle than you cruise at, then you need to richen up the idle circuit. If it is less then you need to play with the main jets.

I reckon the F9 is too large and you should go down a size on the idle bleed, but could be wrong.

If it turns out to be main circuit related, then there are a number of things you can play with.

1. Smaller chokes.
2. Higher float level
3. F3 emulsions. These are identical to F11 but narrower, so require less vacuum to start pulling the fuel through. Convinced they are better for rotaries, but emulsions are expensive.
4. Bigger main jet.

As you can see it is easier if you can do it via the idle circuit. Webers are a hassle to get right, but when dialled in are great.

Actually never had a Holley carb. The only other performance carb I had was a Mikuni on a 13B SP Rx-7 10 years ago..;)
This is good info Bill- I appreciate it! F3 emulsion huh? My DCOE has F11's..

Everyone says use F11, but noone knows why. I have the drawings of all the jets so can work out which one does what to a degree (still some black magic)

I would still focus on the idles first though.

Well, I just ran a few tests to see if (one) of the problems is fuel delivery. I installed the Holley pressure gauge on the outlet side of the fuel pump ( 3" from the outlet pipe). Started her up and I'm getting a whopping 3 psi (according to the Holley guage) out of the pump. It's a weber pump that states factory setting at 6psi..

Secondly I took the guage, installed on the inlet side of the carb ( 3" from the inlet pipe on the carb), started it up, the gauge reads slightly less than 1.5 psi. There was no regulator in line...Just straight from the fuel line.

It seems the pump is definately inadequate or defective. Either way, I should be getting more than that from the pump??

There was another odd thing I noticed. I have seen a few of the Weber installs (like T.J's) and noticed none of them has a return fuel line. When I pinched off the return fuel line at the carb, the psi reading went up to just below 3 psi, almost matching the outlet pressure from the pump..Should I swap out the dual pipe feed for a single one? Thanks folks!
:confused:

I've never used a return with webers. That could be messing up the regulator, but again I always use mechanical interruptor pumps for that authentic clacking sound.

1.5PSI is still in the ball park for a weber. If you can sustain high power then your flow is OK. If the stumbles get worse after hard acceleration then it is pointing to the float bowl not filling up quickly/high enough, which could be pressure related.

I'm going to try and cap off the return line tonite and see how she runs. Thanks again for your help, Bill!

I'm out of touch for a week now, but PM me next weekend if you have any problems

I called Fast Freddies (who distributes Webers to a lot of shops). They advised to block the return fuel line and switch to the inlet line only. They said thats why the fuel pressure was cut in half(??) I'm having a hard time believing that psi would be cut in half 3" away from the outlet of the pump, but I'm gonna try a temporary fix tonite and check the pressure again..
Also - I ordered some extra jets to play around with..
I'll let you all know what happens. Thanks again

Well for posterity's sake- I capped the return line and re-installed the holley reg and gauge.-voila constant pressure (i set it to 2.5 psi). The manifold was cold as ice and definately running richer (nose test)...However- my cruise at about 3,000 was still hesitating, albeit not as bad. Me- thinks I'll be fiddeling somemore this weekend!

Looks like you're on the right track, but that's a weak fuel pump. buy a holley blue 110gph, PLEANTY of fuel volume and pressure. it's what I used on the 12a streetport and bridgeport. I use a fuel return line. it'll send unused fuel from the hot enginebay back to the fuel tank to cool.

OR the hard metal fuel line under the car (or rubber line)can be full of crud or even corroded. My REPU had that problem, the clear fuel filter in front of carb barely had 1/8" of fuel in her. fuel just trickled in. Ran Castrol Super Clean thru the fuel pump all the way thru the fuel filter. Sat for 15 minutes. Flushed with gas. Repeat. Lots of yuk came out. Ran POR-15 Metal Ready deruster in there for an hour. Flush with gas. Repeat. Now filter fills up 1" with fuel

i set my fuel pressure @ 2.25psi as measured from the holley fuel pressure regulator that came with the holley blue 110gph pump. An autometer fuel pressure gauge plumed into the regulator and the gauge itself is in my dash. (race car gauge panel).

Good night, good luck.

Thought i'd update the post for others interested in 45DCOE's..

I've been playing around with some additional jetting to try and alleviate the annoying stumble that occurs at cruising speeds..(usually hits at 3K in any gear as long as throttle is held steady)..I've made sure the fuel delivery is constant, no binds, flowing at 2.5psi fairly steady. I've gone up to a 190 and 200 main jet, dropped the air corrector to a 165 and tried f9-65 idle jet..None of the above combinations eliminated the stumble. My main venturis are 38mm and auxilliary venturis 3.5mm, by the way..

So I called Fast Freddies to see if the have any other recommendations..We went over all the jetting, E-tubes, venturis, blah, blah..Then he asks "Have you adjusted the airbleeds?"..I says- "What air-bleeds"..He says, "How old is your 45 DCOE?"...I says "I dunno- I bought it from a guy who had it on his stockport 12A Rex"..He says "What kinda float do you have? "...
I says "Brass"..He says "Uh-Ohhhh, you've got an older 45 DCOE ".. I says "What the hell is that supposed to mean?"

Apparently (according to Fast Freddies)- the earlier style 45 DCOE's were very prone to this stumbling, especially on Rex's... He said that's why they refused to sell them for Rx-7's until recently when they adjusted the circuits and provided airbleeds, which alleviates this issue...

Well bite me... Am I screwed? I mean, I'm no carb expert by any means but there should be a way to correct this..I'm going to assume there is insufficient flow at partial throttle, which should be eleviated by providing additional mixture?? What would be the effect of trying different E-tube combo's...

(Sorry about the book- but this may be helpful to others wanting a 45 DCOE.)

[QUOTE]Originally posted by Tom
[B]I called Fast Freddies (who distributes Webers to a lot of shops). They advised to block the return fuel line and switch to the inlet line only. They said thats why the fuel pressure was cut in half(??) QUOTE]


actually, you can keep the return line, just install any webber main jet where the soft and hard line meets to slow down the flow back to the tank. be sure to crim the hard line to ensure that the jet stays in place.

'Recently' is relative. The DCOE with airbleeds have been around for quite some time now.

The stumble is caused by the fact the the butterfly is in the wrong place at idle. It should be set so that the butterfly is 'just' about to uncover the first of the progression holes at idle. Now just because you don't have an adjustable air bypass doesn't mean you can't do it, its just a bit more effort.

I am guessing that, if you take the progression covers off and have a look you will find that the butterfly is too far forward. In order to get it in the right place you need to introduce and additional bleed. This is simply done by drilling a small hole in the butterfly. Start with about 0.1". If you go too big then you can solder it up.

Now this is a bit of a pain to do as you need to keep whipping off the carb, but is a well documented technique.

When you get close the other thing that helps is to tweak the ignition advance. This is where mappable ignition is really good with carbs and provides great drivability benefits. Problem is that there isn't an affordable 3-D ignition unit for rotaries around.

Bill

Good info in these posts. I have a 48 DCO on my street ported 13B and had the same problem (when I had it on the road). I plan to get it back together sometime, and when I do I need to get rid of this stumble on my car.

Thanks Bill..I'll prob start early tomorrow a.m. with your instructions...If additional drill holes are required in the throttle plates, will the location of the new holes be apparent after inspection or do they need to be in a specific location (like close to the butterfly spindle dead center on the throttle plates or closer to the outside of the throttle plates?)

And as far as timing, I'll try 2-3 deg advance when I get close..(I have to replace the bulb in my light..The last time I used it was 10 years ago on my last RX-7!!).

On a side note- Ever put an aux venturi in the wrong way?? I did...thought my car was having a heart attack!
Duh... :doh:

Oh and by the way Bill, I owe you a pint for your help! :beerchug:

Holes can be pretty much anywhere. Just be careful not to bend the spindle or get swarf in the engine.

If I have to perform this mod it will definately be on a bench...Swarf would certainly maim a rotary for sure!

Is 145 Main Jets are too Small for a 45mm weber DCOE? Has anyone tried these jets on their 13b setups

F-11 E tube
F9-60 idle jet
175 Air correction jet
180 main jet
85 pump jet
" I think the pump jet needs increasing, possibly 250. 85 sounds just too small.

Don't ask me.. My love/hate affair with progressive side-drafts is officially over- I just received my Sterling/Carl Nikki carbie in the mail the other day.. It goes on this weekend! :)