Oddball Weber IDA questions
 

Has anyone flowbenched a weber IDA to see what CFM it has?

And, with the RB IDA manifold, does anyone know the thread and pitch of the brake booster fitting, and the two fittings in the primary port runners?

Does the 2nd gen oil injectors thread into the RB IDA primary port runners?

deos it matter how much they flow there freakin awsome!!!

The brake booster fitting should be a 3/8" NPT, if the other 2 are for OMP lines, then they're probably 1/8" NPT.

I've never seen anyone use the FI oil injectors on a carb intake, interesting idea. If you go that route, keep in mind that the vacuum hose is not a vacuum line, it supplies filtered fresh air. Tap into the bottom of the filter box, inside the fitered air area for supply. I don't really see any advantage in using them. 1/8" NPT brass barbs have always worked well.

hi trochoid,

1/8" npt on the brake booster is very close, but does not quite thread in. i think it's still metric, and i've seen stock 12a carb brake booster hardware on there for that.

for the omp ports, i'm just looking for something that threads right in not involving retapping. it's a real oddball thread and their website says it's metric so a trip to the junkyard will find out if the FI oil injectors are a fit. if not then i'll just have to brass barb it.

On the other older IDA manifold, the stock RX-7 brake booster's banjo bolt should work fine. The newer one must be tapped and just use a barb fitting.

The brake booster is a mertic thread 12mm fine thread. I used a fitting from earls that i orginally purchased for my 48 dell sidedraft. the omp fittings are 1/8 npt and the card is a 12mm corase also got from earls. THIS IS ON MY INTAKE WHICH IS A OLDER ONE

thanks to the junkyard i now know a stock 1st gen banjo bolt threads into the new RB IDA manifold.

could not find any easily accessable 2nd gen oil injectors, didn't want to spend time taking intake manifold off the only 1 i found.

so for the omp fittings i'm gonna tap out to 1/8" NPT and use the traditional brass barb fitting.

For the OMP, use the stock nikki's brass inlet fittings. Then apply heat to the stock plastic lines and bend it to fit OR if its too short, use fuel lines. Believe it or not, fuel line will handle oil with no issues.

http://img.photobucket.com/albums/v3...Picture577.jpg
http://img.photobucket.com/albums/v3...r/DSC06364.jpg
http://img.photobucket.com/albums/v3...r/DSC06362.jpg

thanks mel, ordered 500*F clear tubing and 1/8" NPT brass barb fittings. gonna get it going soon.

https://www.rx7club.com/attachment.p...1&d=1197047125

https://www.rx7club.com/attachment.p...2&d=1197047125


Ordered all this from McMasterCarr.com

5346K61 BRASS HOSE FITTING, BARB X MALE PIPE FOR 1/8" HOSE ID, 1/8" PIPE

5773K14 EXTREME-PURITY CLEAR PFA TUBING, 3/16" ID, 1/4" OD, 1/32" WALL THICKNESS, CLEAR

6541K34 DOUBLE PINCH ZINC-PLTD STL HOSE & TUBE CLAMP, 13/64" TO 9/32" CLAMP DIAMETER RANGE

Cost $25 shipped

Note that although the barb says it's for a 1/8 hose Inside Diameter, a 1/8 ID hose will not fit. The Outside Diameter of that barb is 3/16. Thus the 3/16" hose I ordered slides on like it belongs there.

The two black allen head plugs in the Racing Beat Weber IDA manifold are metric pipe thread, and must be tapped to standard 1/8" NPT. Only takes a few minutes and the tap was five bucks. Tap it slowly, with lots of cutting oil or old man 3-in-1 Oil by WD40. I tapped 5.5 threads in there.

Put MotoSeal on the threads of the hose barb. MotoSeal is a gasoline impervious silicone sealant. Bought MotoSeal at the local Kragens. Then thread the barb in, let the manifold sit with the barbs facing up, threads facing down, overnight. That way excess MotoSeal will pool up where the manifold meets the barb, and make even more of a seal.

Cut the lines to length. Slide two of the clamps on there. Fill up the OMP lines with oil. I used an old man little black oilcan filled with castrol gtx 25/50 but would have used 2 stroke if I had any in the garage. Then put the lines on OMP. Crimp down the clamps with standard wire crimpers. Fill to the rim with oil, put other end of line on hose barb nipple and crimp that puppy.

Good to go.

nice rotary truck really nice

whats a kragens?

Thats how I first did my IDA's and it smoke a lot just like when you retain the oil feed injection on the rotor housings. Its best to premix it in the fuel bowl.

Turned out it was impossible to seal it entirely as the omp tube was hooked up to a source of constant vacuum. It was sucking air from around the brass fitting barbs. Poured water on the brass fitting and can see it get into the tube.

So now I'm considering buying two of these little 90* elbow fittings and screw them on top of the air cannister. Directly above the auxuliary venturi. Let the oil drip down into the carb. If the fitting is on the outside of the top of the air cannister then it can't fall in. Loctite in place.

Brass Double-Barbed Vacuum Tube Fitting 90 Deg Elbow for .17" Tube X 1/8" NPTF Male Pipe
https://www.rx7club.com/attachment.p...6&d=1219812880

do it on the fuel bowl or carburator cover. its been done many times so there is no need to re-create the wheel.

Agreed....mine are in the top cover, opposite the inlet....and looking at the old RE-Amemiya grey 1st gen, his lead right into the float chamber, above the fuel level.

Although.....for my other weber, I put the OMP in the manifold, and I get no smoke...

of course you wont see smoke at idle and you're not behind the car @ WOT :pfanndina :lol: :lol:

Thanks Guys good info here, i will drill and tap the extended fuel bowl on my 51 i think, seems the best plan

Mark

with the OMP plumbed into the mainfold, turned out it was smoking. I was just used to it and thought it was my motor getting tired. After plugging those 2 OMP holes in manifold Wednesday, it smokes a lot less everywhere.

Is it the threads in the intake that aren't sealing or the hose on the barb? If it's the threads, there are many different types of thread sealer that can fix that. If it's the hose on the barb, try heating the hose and see if it will shrink down and seal. If that doesn't work, there's a way to use fine wire twisted around the hose and barb to seal it. Something similar to the wire clamp that the stock mop lines use.

Threads are sealed great with moto-seal. Gasoline reistant.

It was the barb not sealing and I'm all done with that not going back. I used a nice crimp on connector and more Moto-Seal on it leaky leak. But thanks anyways trochoid.

brad, the weber carbs dont have a specified cfm rating because the venturies are interchangeable.. the bigger the venturies are the more cfm the carb will flow.

on the omp fittings i install the barbed brass fittings with silicone hose and never have a problem :)

my 51IDA turned up today and it already has a single fitting for the OMP lines so i just need to get a brass t to put them into 1 fitting

Mark

Hey DriveFast, what manifold are you using? I've always seen the IDAs turned around with the float bowl to thhe outside and fuel feed from the inside. That's how my 51 is set up. I've also got the OMP feeding the float bowl, tapped just below the air cleaner in the vertical face below the jet cover screen where RB adds their OMP barbs.

Standard Racing Beat manifold Crit. My OMP fittings on the air cannister cover work great, and it keeps rust out of the carb throats all the way down to the throttle plates.

Drivefast, what vent's are you running? I've got an IDA laying around the shop and I have 36,40,42mm vent's to go with it. I can crank up the flowbench and give you some numbers.

Yeah Brad, you're right on with the manifold. I could have sworn mine's a RB manifold, but it's definitely not. I've just started running lean lately using the stock return restrictor for the Hitachi (no real regulator). What regulator and pressure are you running?

I own 38mm and 40mm venturi's. Been using the 38mm's more often, the low end throttle response is much better.

I use a holley regulator with a return line, and 2.75psi measured after the regulator and fuel filter, using a respeed gauge.

it would be really cool to see some numbers with all the venturi's!

I've read some really impressive numbers. The carb was designed to origionally work with 36mm venturis and supposedly flows 450cfm with them in it. The larger you go the more it flows. I run 43mm venturies in my car. Now i read 450cfm on a few VW sites. I'm sure if you were to call someplace like Gene Berg or JayCee they would already have the answers for you.

Got a question, where are you all getting your air filter elements and the top and bottom for the weber? Are you getting the Racing Beat ones or something else? I see them cheaper other places but wasn't sure they'd fit.

I got the bottom filter plate from a local VW shop for five bucks.

Cut and adapted a 1st gen stocker air cannister to fit said lower plate. And use a K&N stocker size air filter drop shipped from K&N in Riverside, CA (cheapest price).

*Everything* Weber IDA related is cheaper at VW shops than at Racing Beat.

OK, as I was leaving the shop I remembered this thread and I clamped my IDA to my flowbench using the fixture I made for testing exhaust ports.

The carb has 42mm vents in it for the first quick test. I have to dig up the other vents over the holiday and I'm going to double check these numbers and make sure I don't have any leaks or other issues with the bench(Superflow 110/120).

With the 42's I get a corrected CFM on one barrel with velocity stack of 311cfm@28". So that would end up at 622cfm@28" depression. So, the 48IDA w42mm vents should be capable of feeding 372hp on gasoline.

This was a quick and dirty test, when I get the other vents I'll sit down and do a whole run cover all the variables like velocity stacks etc.

Other info so you guys can compare apples to apples. Carb test depressions don't really have a standard but in general 20" is used in automotive applications. To get the numbers at 20" from numbers at 28" you multiply by .845

That would give our 48IDA a cfm number of 526@20".

I would say that number would be better for a HP estimate at 314. I never really use that formula so it goes to show you that unless you know the test pressure the cfm number doesn't mean much.

I actually had to test at 7" depression on the carb and its easy to double what you get for 28" values.

Wow impressive, please keep sharing with us all that info :)

awesom thanks for the test results! So wtf is the point of going to a 51 IDA and %% gene berg if the 48 IDA can flow enough to make more HP than most PP's are making.

Just premix, you big bunch of pussies.:lol::lol::lol:

I've found a few different formulas to figure out theoretical maximum HP from CFM numbers through the carb alone. They all end up being optimistic but it gives you an idea of what is possible. The rest of the intake tract really comes into play to cut the final number.

Carbs are rated at different levels of vacuum. Four barrels are rated at 1.5"Hg,(20.33" H2O) and two barrels are rated at 3"Hg(40.67" H20). The biggest reason for the difference in rating pressures was because the most flow benches couldn't pull a 3" depression through a 4 barrel when they first came on the scene.

Given that a race engine is usally carbed to pull less than 1" of H20 at full throttle, top rpm, is that 800cfm carb really flowing 800cfm? Nope. What you end up trying to balance is fuel atomization(need that vacuum to pull fuel) and choking the engine too much. Over carb and you'll make good top end power with shitty midrange and no bottom end. Under carb and it will be very responsive down low and midrange but it will run out of breath on the top side.

And that is why I hate carbs! If I have the choice I give them the floatation test. I take them to the nearest large body of water and throw them as far as I can. If it floats, its a good carb.

OK, OK.... Webers are kind of fun...