SU Carburator
 

Hallo everybody!
I wonder if anybody have try to run a rotary engine
with twin 1 3/4 SU carburators? Iknow that Hurley had a kit with this carburators and they should work well.
but I wonder how many hp they can give sombody know? and the setup for them needle and spring?

mvh svenne

I know where there are a set of hurley carbs for sale. No manifold (as its on my car :-)).

I can possibly get the jetting info off someone running a set, but Hurley never let on the actual mods they did.

HP wise should get you close to 200 with a ported motor. Hurley claimed 190 for a mild port.

It would be verry fine if you can look how I should jet them.Iwork on a intake for them I should have them on a streetported 13B in my rx-4. the carburators are twin SU 1 3/4 hif and now they are jetted for an old volvo140 sport

svenne

I will try. Please nag me with a PM if I do not get back to you.

Bill

thank you verry much Bill

svenne

how do you think is the best way to conect them to the engine?

1. one carburator to each rotor? or


2 both carburators to a plenum chamber then into the engine?


svenne

1 carb per rotor. I'll try and post a picture of the hurley manifold as I use it with EFI

I have a twin HIF6 SU setup that Eamon Hurley made for me about 15 years ago. Most of his kits were sold for 12A's and mine was a custom setup he made for my 13B. I used it on stock and street-ported engines in a couple first-generation cars with no accessories or emissions and racing beat header and exhaust. The jet/needle sizes I have somewhere but if you get in touch with Hurley they could probably recommend which to use. The old dyno sheets unfortunately have gotten lost over the years but it was over 200 if I recall. The setup worked well and I had no complaints about it. There was the extra step to balance the carbs when adjusting them. I can take a picture if you want.

Hello! I have tried to get some information from hurley rotary about jetting my Su carburators but they don`t answer my mail. so if you can found something about how I should jet them I`ll be verry thankful

svenne

Talked to Pip at WGT who has a set of the carbs on the shelf. He is double checking, but it would appear that the needles are off a Rover SD1 2600 I6.

Bill

The model is definitely HIF6 which is 1.75 inches. My Haynes SU carburettor manual is from 1986 and does not list a Rover 2600. In the manual there is written "BAK" in pencil which might be the needle size. I cannot remember writing it there but it was a long time ago. During the time I was using the carbs, I never had reason to open them. Sorry for the incomplete information but it was a long time ago and it is not in a car at this time.

Here are some pics of the engine and intake out of a car from the top, bottom and side.
http://members.aol.com/glcurley/rx7/image023b.jpg
http://members.aol.com/glcurley/rx7/image018b.jpg
http://members.aol.com/glcurley/rx7/image014b.jpg

confirmed BAK is the correct needle

Thank you I appreciate knowing that even though I didn't ask the question. Eventually I will clean mine up and put it back in a car again so it's good to know.

What about the piston spring? I don't have any notes on that. Yellow maybe?

dunno about spring. Can easily find out come the time.

Bill

Right again. It is yellow. You don't need me at all :-)

Thank you verry much for all information!!!!
I should buy needles to a rover and and a yellow
painted piston springs. the jet in the bottom where the needle goes in. are that same on all Su or are there different size?

Thank`s again!!

The jets CAN be different sizes, but you may as well just keep what you get given (as long as they're all the same size).

But with your setup cosmicbang, you see those two brass pipes above where that yellow fuel-pipe goes?
Well, you REALLY want to put a small pipe on there leading AWAY from the exhaust pipes. This is where the excess fuel spills out of them, and you wouldn't really want to have petrol all over that lovely hot pipe would you?

But those carbs have been modified, since where the OMP lines are going into, that hole doesn't exhist on the standard carb. But if you're doing this yourself, either run pre-mix, or fit the OMP lines to the vac-line (located just in front of the butterfly, on the top).


I myself don't like the Hurley setup, as you dont have seperate ports anymore, as both primaries and secondaries run from the same inlet - the standard has secondary butterflys that open when a certain amount of vacuum is apparent in the inlet.

On my setup (I admit, not yet built though) I have a single HIF44 for the primaries, and a HIF38 for each of the secondaries - actuated from the diapragm from the standard Nikki carb.



I also tried to get Hurley to tell me which needle was required - but just the same as you, no response. Thank-god for this forum!! :D

When it was in a car I had the fuel return lines hooked up, but thanks for noticing that. What do you mean by "primaries" and "secondaries"?

The ports in the intermediate plate are the primaries, and the ports in the end housings are the secondarys.

When the vac-signal is strong enough, it will open the secondary ventuuri's on the Nikki carb, allowing higher flow.



When only the primaries are working, you get a higher velocity on the intake:

# Higher intake velocity = higher torque.

But when you open the secondaries at the same time, the port velocity is lowered (because the air has to go to more places at once) but top-end Bhp is increased due to the larger port area now available.

My setup get the best of both-worlds, because you get a relatively high port velocity on the primaries at low RPM. At higher RPM, the secondary carbs will work, allowing higher Bhp than the primares alone would give

Thanks I was not familiar with the nikki carb except for removing it. The car had so much more torque and power than a stock 12A that I did not feel any lack of torque at low rpm.

Well, it would probably only be a benifit if you had a large porting job on your engine - but I'm still doing it anyway.

Why? Because I can :)

I was just thinking about the setup you described and wondered if that be a PITA to balance and adjust?

Yup, that it would be!!! But I'm going to set up the primary carb (blank off the secondarys) get that all sorted, then copy the EXACT amount of turns, etc, for the other 2.

That will give me a basic starting point, and then all i have to do after that is listen to each of the exhaust pipes, and see which ones sounds clearer than the other, and adjust them untill they run the same.

It's not the best method by far, but it'll do the job

Errm,

Interesting discussion, but seems to miss the fact that SUs, being a constant depression design, don't suffer from the problems that drive you to a twin choke design such as the Nikkis.