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What's The Hp Gain With 3 Webers Over 2 Sus For L24


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#1 aircobra

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Posted 02 January 2018 - 09:22 PM

there are a couple of threads on the benefits of these for a standard L24 with the standard exhaust

any facts on what you woul gain if made NO other mods?



#2 gav240z

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Posted 02 January 2018 - 09:35 PM

How long is a piece of string? Try reading this thread for a methodical look at modifications and HP gains achievable.

http://www.viczcar.c...re-the-results/

 

All I know is that when I removed my SU's and installed Triple 44's it has transformed my L28.



#3 TobyMyers

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Posted 12 January 2018 - 07:56 PM

In my experience Bolting on Webers/mikunis to a standard engine makes a massive difference. You Get a noticeable power and torque increase and it sounds great, But i would highly recommend fitting a decent exhaust and cam at the same time if you want to get the most out of them.  


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#4 TOO60Z

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Posted 14 January 2018 - 03:57 PM

Dyno figures or it didn’t happen. At the end of the day it’s only fuel delivery and any transformation you are feeling is accelerator pump related to drivability over SU/ Hitachi. It’s not like you have supercharged this stock engine or anything.

#5 Lurch ™

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Posted 14 January 2018 - 06:33 PM

Dyno figures or it didn’t happen. At the end of the day it’s only fuel delivery and any transformation you are feeling is accelerator pump related to drivability over SU/ Hitachi. It’s not like you have supercharged this stock engine or anything.

 

True. 

But when set up & tuned correctly - you have 6 ports of the same size feeding an engine instead of 2, it's going to make more HP & torque.

You can't beat physics.


Edited by Lurch ™, 14 January 2018 - 06:33 PM.


#6 CraigZ

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Posted 14 January 2018 - 07:33 PM

At a Datsun day a couple of years ago, I was talking with 2 other people running 40mm triples on stock L24 with extractors and we all had 95 kW at the wheels give or take 0.5kw.so close in comparison..
I have no idea what a completely stand L24 would put out on the dyno.. But some one else might be able to ad this info, I'd be interested to know

#7 TOO60Z

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Posted 14 January 2018 - 07:41 PM

Yes the individual runner and accelerator pumps are the major benefit but the OP question was about a stock 2.4 and the gains would be minimal not massive as suggested. The Weber’s would have yes voter chokes in them to run and give a decent fuel curve but anyhoo. The question was as Gav suggests a piece of string with no mention of carb size. Have seen twin 45s jammed on 1275 sprite engines and the physics are abysmal . Seen 48s on 105 Alfa’s, ok at WOT and nothing but reversion all the way up. They are physically too big.
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#8 PZG302

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Posted 14 January 2018 - 09:11 PM

Or like my old 40mm twin webers that came off a 3k 1200 corolla motor, that was set up perfect for that, but we had to go down many sizes in jets to put them onto a warm 2.something litre L18 and have it work properly.

 

It all comes down to set up of the carbies and the motor itself. The Valiant 265's ran 45mm webers, but you would often see 48's put onto much smaller capacity motors and running as well.

 

If all being equal in terms of condition and no other changes made, as said above, you would probably get a small increase in power and torque, but more importantly much better fuel delivery to each combustion chamber and therefore better driveability.


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#9 cracker

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Posted 14 January 2018 - 10:13 PM

At a Datsun day a couple of years ago, I was talking with 2 other people running 40mm triples on stock L24 with extractors and we all had 95 kW at the wheels give or take 0.5kw.so close in comparison..
I have no idea what a completely stand L24 would put out on the dyno.. But some one else might be able to ad this info, I'd be interested to know

 

My old zed that was mostly stock achieved 85 or 87 kw atw (can't recall which) when it got dynoed.



#10 Cozza

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Posted 14 January 2018 - 10:53 PM

I would suggest it comes down to each system being jetted correctly throughout the rev range as well as having optimal air flow.
As triple dcoe’s provide 6 throttle plates shortly behind the inlet valve, good flow and quick response is recognised. They also use multiple fuel and air jet adjustments which provide accurate fuel metering throughout the rev range and throttle position.
As opposed to twin Hitachis having 2 throttle plates, each having to disperse air and fuel via a 1 into 3 manifold which limits flow and response and, only 2 tapered needles to meter the fuel. It can sometimes be a challenge to find the perfect needle and spring arrangement to suit your engine conditions.

I would suggest the triple dcoe’s would be a “better” system to provide all cylinders with the accurate air/fuel ratio throughout the rev range and would likely make more power. Probably why so many people swap to dcoe’s of some type.

In saying all that, all the S30 Sc race cars running twin hitachis are far quicker than my triple Weber’d car 😒

Just my 2c.
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#11 TOO60Z

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Posted 14 January 2018 - 10:59 PM

I would suggest it comes down to each system being jetted correctly throughout the rev range as well as having optimal air flow.
As triple dcoe’s provide 6 throttle plates shortly behind the inlet valve, good flow and quick response is recognised. They also use multiple fuel and air jet adjustments which provide accurate fuel metering throughout the rev range and throttle position.
As opposed to twin Hitachis having 2 throttle plates, each having to disperse air and fuel via a 1 into 3 manifold which limits flow and response and, only 2 tapered needles to meter the fuel. It can sometimes be a challenge to find the perfect needle and spring arrangement to suit your engine conditions.
I would suggest the triple dcoe’s would be a “better” system to provide all cylinders with the accurate air/fuel ratio throughout the rev range and would likely make more power. Probably why so many people swap to dcoe’s of some type.
In saying all that, all the S30 Sc race cars running twin hitachis are far quicker than my triple Weber’d car 😒
Just my 2c.



#12 Roady

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Posted 14 January 2018 - 11:20 PM

L28 (standard, tired with twin hitachi) - had 66kw (at wheels)
72 degree cam - became 78kw
Triple webers (45) - became 89kw

All done on same Dyno same time of year

As per everyone's brief before, different depending upon jetting, chokes and what kind of driving you are tuning for.
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#13 TOO60Z

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Posted 14 January 2018 - 11:20 PM

Exactly, mick and you are still filling the same size cylinder regardless of which set up you have and target the same AFR so it’s only a minimal increase. As you know more gains can be made when proper heat shielding and cold air are introduced as well. All the little things help but you have to be prepared to whittle away at it.

#14 TOO60Z

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Posted 14 January 2018 - 11:39 PM

Going away from the original question as it was L24 stock with no mods. Now we have L28 with cams. How’s this. OP the hp gains would be minimal but you will get increased induction noise and drool on the front guard from your mates when you pop the bonnet. That’s it! Unless you throw your stock diff away too and put a 4.1 ratio in to make it drive better around the streets. Then you may as well strip it out and make it as light as possible cause weight kills performance.

#15 Roady

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Posted 15 January 2018 - 07:40 AM

It outlines what power I gained from changing things, including induction. If we are straying off topic your right, let's lighten the car and change diffs!
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#16 TOO60Z

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Posted 15 January 2018 - 11:37 AM

And paint it red.

#17 gav240z

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Posted 15 January 2018 - 11:39 AM

LOL still debating the length of that string...

 

My L28 (standard bottom end) has an early E88 head (72 240z) with N42 size valves, some port work (no idea how well it was done, no CFM figures etc..) and mild cam (specs unknown), it has electronic ignition, lighter flywheel and flat top pistons (so we're guessing around 9 or 10:1 comp ratio).

 

It was previously running twin SUs (unknown needle sizes) and would feel flat after 4000 rpm. It's possible it was not fueling enough for the L28 and part of the problem.

 

Switching to Triple 44's (haven't even checked jetting) but guy I got them from on eBay over 10 years ago told me they were set up for his L28 (stock), as mentioned has transformed the car, the way it drives, it's progression (thanks to accelerator pump) and top end power (spins to 7000 rpm without question), it feels significantly quicker than before and sounds 100x better.

 

I would NOT switch back to the SUs, the car drives night and day different to before. The previous owner had Triple Dellorto's on the car before he sold it (not sure on size), but I am guessing my engine was never intended to run on twin SUs (by whomever built it), and putting the 44's back on has uncorked it. We still haven't tuned the Triples yet, and the ignition curve could be improved but it just drives so much better now than before. (Other changes also made include close ratio gearbox and exhaust system change). But by far the biggest factor to the way the car behaves now is the installation of Triples and I would never willingly go back to SU's. I know they can be made to perform, but they are a far simpler design (which is a good thing), but Mikuni/Solex are more sophisticated but the pump jet (accelerate pump) set up is brilliant in terms of progression etc.. and the tune-ability is far better with Triples.

 

There is a reason they were a Sports Option catalog (option), they are just better... but you can only really judge that when driving a car with SUs and then comparing with Triples.

 

We can debate HP all day, but each engine set up is different (as I tried to convey above with my own set up) and therefore gains in power will vary depending on what you're doing..Like I originally said you can't provide a figure easily as each car will be different. Thing is when doing engine mods at some point the SU's are going to be a restriction and limitation. In cars I've driven above 5,500 rpm it starts to get flat and they run out of breath.

 

At some point we will get mine on a dyno to tune and I'll be able to give HP figures. There is a tiny flat spot at 4,000 or so rpm which I think is because we haven't done fine tuning of jetting in the Mikuni's etc..


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#18 hmd

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Posted 15 January 2018 - 12:28 PM

there are a couple of threads on the benefits of these for a standard L24 with the standard exhaust

any facts on what you woul gain if made NO other mods?

 

Of course there would be gain but how much gain over tuning the SU properly is the question.

 

If you have a Les Collins engine no doubt you should go with a triple, a standard everything L24 I would say the twin SU is more than adequate.

 

All the group S L24 and L26 runs twin SU. 



#19 TOO60Z

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Posted 15 January 2018 - 02:16 PM

Can anyone confirm the red paint thing as i am intrigued but somewhat in the dark as my car has 44 mikuni's but is blue in colour?
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#20 gav240z

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Posted 15 January 2018 - 02:41 PM

SU's...

 

VS Weber 40's (too small)..

 

Pulled from Youtube Description.

 

For the same engine with SU carbs...which is a 1983 F54 L28 w/P90 turbo head, 10:1 compression, 15lb flywheel.

 
The engines sound similar but the Webers have much more torque than the SUs, pull very hard in 1st and 2nd and easily to 7,000 in 3rd. I have a Centerforce 2 clutch now which make changing gears a tick slower compared to my earlier video however. The car is definitely faster through each gear with solid power to redline.





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