Triple SU intake

Mr.G

Mr.G

Club Member
240Z%203-carb%20setup.jpg


I admire the amount of effort, skill and money this guy went through to try out his triple SU intake idea on an L Series engine.

More info here: DATSUN 240Z 260Z 280Z CUSTOM TRI-CARB INTAKE+COM.RIGHTS | eBay


I was interested in this statement:
"Be aware that this setup does not provide as much vacuum as the stock intake setup, so the brakes will not have as much boost from vacuum as a stock intake would provide."

You can see he has plumbed in a copper line to all three parts of his intake and connected them all up to the brake booster. Why would this not give enough vacuum? On a traditional triple intake, I believe, and please correct me if wrong, that only one of the runners nearest to the firewall is the one used for brake vacuum.

I wonder how much it would cost today to make your own intake manifold.
 
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Hmmm its possibly because you have 2 cylinders fed by 2 runners from one large mouth both on different cycles .

I do know that a guy in Aus tried it and had bad problems with reversion due to inlet pulses and the whole phasing of the 4 cycles with three carb mouths.

Nice try though
 
SKiddell said:
Hmmm its possibly because you have 2 cylinders fed by 2 runners from one large mouth both on different cycles .

I do know that a guy in Aus tried it and had bad problems with reversion due to inlet pulses and the whole phasing of the 4 cycles with three carb mouths.

Nice try though
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Interesting, so how does it work on a triple throttle body set up, would you just take boost reference from one runner on the triple intake manifold, nearest one to fire wall for ease of routing to the brake booster? Or would the reference come off the throttle body in some way?

EDIT: I am thinking of DCOE Throttle bodies.
 
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The triple SU set up has been done successfully by one or two people in the US, even though there are things against it. No real gains, but it has been done.
 
Mr.G said:
Interesting, so how does it work on a triple throttle body set up, would you just take boost reference from one runner on the triple intake manifold, nearest one to fire wall for ease of routing to the brake booster? Or would the reference come off the throttle body in some way?

EDIT: I am thinking of DCOE Throttle bodies.
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Yep, runner nearest the firewall


There is another scenario with TBs, in that you tend to run bigger cams with TB's and as such you lose some vac anyway... I don run a servo for 2 reasons, my vac at low revs is minor and I like the direct feel it gives.
 
Ian Patmore said:
The triple SU set up has been done successfully by one or two people in the US, even though there are things against it. No real gains, but it has been done.
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Respectfully
As mentioned, I admire the effort but I cant help but wonder why on earth would you want to do it....fair enough if its for just because you can but if you ever think its going to be better than say triple 4X's or TB's then you have just not thought it through.

I just can't help but think that some guy one day thought, "I bet Nissan or whoever never thought of this, I know, lets try........3 SU's :thumbs:

Well of course they thought about it....for about a second, then saved themself a load of pain and didnt do it, becuase soemthing else worked better er Duhhhh
 
SKiddell said:
There is another scenario with TBs, in that you tend to run bigger cams with TB's and as such you lose some vac anyway.
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Steve,

I was chatting with Jonny-boy yesterday, he mentioned that Saab's have an electronic vacuum assist on their cars.

Thoughts ?
 
If you're worried about losing VAC on an ITB equipped NA car with wild cams, then why not try constructing a vacuum tank consolidating vacuum reference from all 6 intake manifold runners and have your brake booster reference off the tank too. It could be possibly that a tank would not suffer so much from unbalanced pulses, not talking from experience here, but that is what I'm going to be doing - I'm not running an NA so I could get away with it. Needs some trial.
 
To be honest, I now really like a non servo pedal feel yes its takes hulk like leg muscles but the feel and feedback is great.
 
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