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Holley 2280 setup for boost

 
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player1up
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Joined: 11 Dec 2007
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Location: Orlando, FL

Post subject: Holley 2280 setup for boost (Wed Feb 23, 2011 7:53 pm) Reply with quote

As the title says, I'm looking for advise on how to setup a Holley 2280 for boost. It has a mechanical power enrichement circuit.
Current jet size is 28 ( that is the number on the side of the jet ) and is almost too small for the car currently.
Is there anything that has to be done? I've read all of the articles on 4bbl carbs but I'm not making any correlations...



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player1up
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Post subject: (Thu Feb 24, 2011 12:10 pm) Reply with quote

I suppose I should be a little more specific.
I'm wondering how the enrichment circuit needs to be changed if at all to get it to handle boost.

From what I read here, I see that as the vacuum goes away ( under full throttle or boost) the spring on the vacuum enrichment side pushes the circuit open.
Roughly the same thing happens on the mechanical side but it's similar to the accelerator pump shot ( as the throttle opens, the mech enrichment circuit opens via metal arm ) .

Now the question, how to increase the flow of the enrichment circuits?

The mechanism is the same between the vac and mech sides ( a little tapered pin that gets pushed down, opening the holes in the brass slide body ) .

So, should I enlarge the holes in the brass slide body? or should I decrease the diameter of the slides? or both?



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Doc
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Post subject: (Thu Feb 24, 2011 12:47 pm) Reply with quote

Have you already run this carb under boost? Problems?
I am guessing that this is a 'blow-thru" set-up, correct?
How much boost, PSI?
DD


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player1up
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Post subject: (Thu Feb 24, 2011 2:24 pm) Reply with quote

Sorry I left out some info.
Yes it's a blow-thru setup. J-pipe mounted turbo between the fender and the A/C compressor on a stock 73 motor.
I did the initial install this past weekend and it starts fine, idles fine, even drives fine as long as I stay out of the boost.
I couldn't get it figured out so I swapped everything back out and would like to try again, soon but I need to get it sorted before I try again.
I assumed that the jets for a v8 would be enough more fuel with the referenced mechanical pump to handle it ( and it almost is ) but not quite...

Wastegate spring is set for 6#. I'm not looking for huge HP as this is a daily driver, but wanted some umpf and the ability to put it back to stock if things don't work out.

If I fan the throttle ( to keep the accel pump shot going ) I can keep the AFR at about 11-12 but if I just throttle into it, it just bottoms out lean...no pinging but just wants to stall.
The reference pump does put out 1:1 increase with boost but apparently the carb can't keep up. I don't want to go huge on the main jets because I'd really not like to run the 8MPG that my buddy does in his TT G35 and from what I've read I shouldn't have to.

I've read just about every page on the turbo forums came up with a modest plan ( and stuck to it ) and have been slowly putting the pieces together over the last couple of years and thought I had everything planned out fairly well but apparently I'm not qualified to operate this piece of machinery Laughing Rolling Eyes

Don't worry, I'm not giving up just yet but maybe holding off...



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Doc
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Post subject: (Thu Feb 24, 2011 2:50 pm) Reply with quote

Bottomline... that carb is too small to support full boost, even at 6 psi.
I take that back, you can richen-up that carb enough to run at full boost but at that point, it will be over-rich when off the boost, to the point of bad MPG & driveability.

Here is an idea, leave the carb alone and look at getting a Hobbs switch (pressure switch) and a fuel solenoid... then set that up to deliver extra fuel during boost.
DD


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Charrlie_S
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Post subject: (Thu Feb 24, 2011 5:54 pm) Reply with quote

Don't know about the 2280, but when I did my first turbo setup, I used a BBD. The inlet needle and seat were not large enough, and would not flow enough fuel to keep the float bowl full when using boost.



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player1up
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Post subject: (Fri Feb 25, 2011 8:50 am) Reply with quote

Charlie, Doh!, that didn't even cross my mind. I'm kinda embarrassed. Embarassed

Doc, Ok apparently I have some more research to do. Sounds like I'll have to run an additional pump and some sort of injector then, correct?

Maybe I'll just look into getting an adapter for an Autolite 2300 carb and run that. Seems as though people are having better luck with that one. At least there is more info out there on how to mod those. Back to the drawing board...



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Doc
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Post subject: (Fri Feb 25, 2011 9:42 am) Reply with quote

Charrlie_S wrote:
Don't know about the 2280, but when I did my first turbo setup, I used a BBD. The inlet needle and seat were not large enough, and would not flow enough fuel to keep the float bowl full when using boost.


You were running a draw thru system at the time, or was this a different set-up?

Either way, when running a small carb with a turbo you either blow more air thru the carb then it can effectively add fuel to or you suck on it hard enough where it can't flow enough to keep-up.

As for using a separate nozzle system for enrichment, it's pretty simple to use N2O parts and tap into your current "boost referenced" fuel supply to feed it. Look-up alcohol injection for some ideas and a system lay-out.
DD


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Charrlie_S
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Post subject: (Fri Feb 25, 2011 10:32 am) Reply with quote

Doc wrote:
Charrlie_S wrote:
Don't know about the 2280, but when I did my first turbo setup, I used a BBD. The inlet needle and seat were not large enough, and would not flow enough fuel to keep the float bowl full when using boost.


You were running a draw thru system at the time, or was this a different set-up?

DD


I have only run a draw thru turbo system, with several different carb setups. The only one I could get to work fairly well was the Holley 4412, 500 cfm 2bbl, with a externally referenced power valve. My biggest problem was ign timing. Back then there was no such thing as electronic boost retard. (or O2 sensors, either)



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LUCKY13
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Post subject: (Fri Feb 25, 2011 11:52 pm) Reply with quote

I would not be afriad to jet it a little, and I dont know much about these carbs but you should be able to enrichen the enrichment curcuit on it without hurting the off idle drivablity.

Looking at the diagram you linked to I am wandering if you have the float bowl referenced to boost pressure? Just looking at the carb ( and assuming your trying to run blow through) I expect you have made a hat for the carb. SO does the bowl vent get the same pressure as the hat?


Ok I seen the second diagram you linked to it looks like it has vacume power curcuit ? DOes it have two power curcuits, or does it work from vacume and machanical ?


I did notice it does have Power curcuit channel restrictors ( Built in orfices probably) . These can be enlarged and it will only give extra fuel when throttled.

Another thing is the carb may not have bigger jets with it being for a V8. It could infact be smaller jets ( bigger engine has more vacume to pull on carb so it gets more fuel even though smaller jets). NOt sure on that but dont count on it being jetted right for the engine just because of that.


I think you can get this carb to work. BUt I would need to know more about it to really go any farther. BUt first, you need to work the carb out on the engine without any turbo system on it. This will give a better starting point. Then the fuel bowl will have to recieve the same boost the carb gets. Then the power enrichment curcuit will have to be calibrated. And ofcourse the needle valve will still have to flow enough which could be a problem, but i think it can be fixed ( there are other carbs that use this type of needle seat, a bigger one may be able to be used).


It would be much easier to use a Holley two barrel ( 500/350). I would use the 350, but with the center hung floats like the 500 has. BUt if you only want mild boost your carb may still work, just need to work through the setup. If your carb has a vacume and a machanical power curcuit this could be a good thing. I didnt really understand that part of it. You where saying it was machanical but the one diagram was showing vacume. Maybe its vacume that is over rid by machanical, or maybe it has both I dont know. Some type of two stage system would be ideal for a blow through carb. Maybe I can find some more info on it with some searches. I will see.


Either way I would nto give up on it, it might work just fine when figured out.

OK, looking a little closer it looks like some of these carbs where machanical, and some vacume power curcuits. IN that case after getting boost to the fuel bowl the PVCR ( power valve channel restrictors) can be enlarged to give extra fuel. Also need to pay attention to the power valve itself and see if it has enough flow to feed bigger restrictors.


It loooks like it is ajustable to ( with a rod to change the point in throttle possition it opens it, or how far it opens it).

It gets real tricky with blow-thu setups because there may be time you need enrichment without boost, and then of course when you have boost. There will be some compromising to be done in that area. WIth only small boost PSI it might even take off once you add boost to the fuel bowl if that has not been done yet. Then small ajustments to the PVCR's can dial it in on the A/F. Then ofcourse the air bleeds can help it even farther but without a Wide Band A/F meter or a Dyno its kinda hard to do.

Incase you didnt realize the rising rate fuel pressure regulator is needed because of the boost pressure in the bowl, which it needs to help push more fuel out. Then the higher fuel pressure is need to over come this to get the fuel in the bowl. Its all a ballancing act.
Jess


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player1up
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Post subject: (Mon Feb 28, 2011 12:27 pm) Reply with quote

The Holley 2280 has two power circuits, one vacuum and one mechanical.
The fuel bowl gets it’s reference from the main inlet ( there is a channel just in front of the main horn for air to flow to the top of the float bowl ) so I capped the vent tube. As of now I've got 2 sets of jets to try (one set says 175 on the side and the other set says 283 )
I picked up a rebuild kit that has the power valves ( so I have a total of 6 to choose from or modify ). Before reading your post the plan was to setup the carb “stock” and run it without the turbo to see how it behaved, then modify the power circuits to handle the boost. I just got a little too excited with the setup after the install and got ahead of myself.
The mechanical power valve has a set screw for adjustments. It’s just a REALLY long process of pulling the top of the carb on the car and changing things…
I get what you’re saying about the balancing act. The vacuum power valve opens at -10” so it will be open from -10 to +6 lbs of boost, the problem is when to open the mech valve, how far and how far I need to port it to handle the boost…

One of the other things is the power valve restrictors, they are only accessible if I remove the lead plugs in the bottom of the carb and I haven’t done that yet…I’ll see what progress I can make first, but from what I figure, the restrictors are a one time shot, once I open them up…no going back…I’ll see what I can do about posting some pics of the carb



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