bill Shurvinton

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

Tom

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

Tom

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!

DriveFast7

iTrader: (1)

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.

Tom

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.)

Siraniko

iTrader: (13)

[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.

bill Shurvinton

'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

RX-Midget

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.

Tom

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...

Tom

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

bill Shurvinton

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

Tom

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

therotaryracer

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.

Tom

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!