dual webbers vs single

[alpine_64]

Thanks for the offer Jarrid, but i have the DGV ready, and it should be good enough for the purpose i will be using it for. It would be interesting to see how that system went on an alpine... but for the moment my alpine ownership will revolve around reliability and general up-keep.

 

[64beam]

Robin,

Dont know if that was an oz-oz jab, but some of us know how to tune webers, and as far as induction systems are for me, its either DCOEs or DCOE bolt on air doors for EFI. That is Ive chosen my manifold and its never coming off.

By no means was I having a dig/jab at Michael's setup. I always envied his Weber setup in his Alpine. I also love and use the twin side draught setup as you may already know, but I too are changing to a down draught setup just different reasons.

Kind regards, Robin.

 

[Armand4]

Okay, here's a slightly different thought: can we bolt one of Weber's bigger downdraft two-barrels to the Solex/DGV Alpine manifold for increased performance? I'm thinking of the IDF/IDA/DCNFs here, not the 38DGES. Aren't those infinitely tunable and generally awesome?

 

[RootesRacer]

With an adapter, the DCNF could be used, but both the IDA and IDF are too tall and would protrude the bonnet.

DCNF carbs came 36, 40, 42, 44 and 48. All but the 40 are hens teeth, and the only part to the DCNF that the DGES doesnt have (replaceable chokes), are absolutely unavailable anyhow.

Okay, here's a slightly different thought: can we bolt one of Weber's bigger downdraft two-barrels to the Solex/DGV Alpine manifold for increased performance? I'm thinking of the IDF/IDA/DCNFs here, not the 38DGES. Aren't those infinitely tunable and generally awesome?

 

[atallamcs]

Single side draft

I found this to be a good set up for my race car.
A single weber 45 DCOE on a Lynx manifold. Very responsive.

http://rides.webshots.com/photo/2577021820078015567eKaszy

Bill

 

[Limey]

Acording to the wise ones whos race services cost me a deal of a pile of bunce for their race proven utterances, a single pair cannot ever provide better performance over a double pair unless the inlet sytemn is so very ineficient and 'choked' so as to make a pair irrelevant. My tuner guy gets 160++ BHP (within the British club racing regs) from a 1725 Alpine engine with oomphs of torque and when questioned about single pair setups asked ''Would you prefer one leg or two Sir??!!' ( I quote) I'm interested to know as one pair is a deal cheaper than two but I can't see it. I bow to the sages of course. Speak and I will hear (and perhaps obey)

 

[Jim E]

I have heard those sorts and higher HP numbers for Rootes engines and I just have a really hard time with it. Maybe at the flywheel I could see it. In my book if you can lay down even 100 HP at the wheels you are doing something.

 

[Jay Laifman]

I have to add my $.02 here - because I always have to when it comes to Webers. I have twin DCOE 151s, Holbay head, Holbay cam, lightened flywheel, and custom exhaust headers, and I LOVE the way the engine runs. It will idle smoothly all day long, it's got tons of midrange, smooth power, and it flows so beautifully at high rpm that it's absolutely intoxicating. Maybe I was just lucky at getting it jetted right. I don't know. But, this car is the snarling sports car it should have been from day one. Had Rootes gone this route, I'm pretty sure the Tiger never would have come to be (not that the Tiger is worse, but that my Alpine is enough of a character change that they probably wouldn't have made the change to the Tiger).

For what it's worth, I did spend a lot of time trying out different jet combos in real world driving, not just dyno. I ended up liking the F11 emulsion tubes better than the more common F16. I admit that the F16 felt like it gave a stronger WOT, but all rpms were noticably smoother, and rich with the F11.


As to hp from the 1725 engine, I have the brochure from Holbay somewhere. They list a three or four stages. As I recall, the highest was 160 hp. Perhaps it was called "Marathon".

 

[atallamcs]

HP

What little I have as HP metrics.
My Harrington has a professionally built 1725 with all the factory tricks, head work, twin dcoe's, lightened, balanced etc. It dyno'd at 115hp.
My race car came with a 1725 and it has all types of non-rootes parts to make it a better performer--it dyno'd at 138hp. We have made a few additional changes on the intake and exhaust side--we anticipate a solid 150hp--reliable power.
A friend and long time alpine race guy had done everything and a bit on the wild side to his car and ranged in the 160-170hp range but it was race quality--meaning, every other race the engine would need something.
I would be surprised if someone gets 160hp in a reliable, everyday driving engine.
Bill Atalla

 

[Jim E]

Bill,
Are those numbers at the fly wheel or the rear tires?

 

[Eleven]

One choke per cylinder

always sounded wrong to me (although it apparently isn't). The starting and stopping of the air flow as the valves open and close does not seem efficient. It would seem to dictate fewer venturi and longer, common intakes to maintain as constant flow as possible. Oh, please don't post any more photos of your set ups, I am starting to get depressed with my cruddy old Strom's...!

 

[RootesRacer]

Brian Holm should ring in on this, but he has a 1725 turbo EFI engine that by my calculation should produce in the 250BHP range, with reliability probably better than most stock 1725s.

What little I have as HP metrics.
My Harrington has a professionally built 1725 with all the factory tricks, head work, twin dcoe's, lightened, balanced etc. It dyno'd at 115hp.
My race car came with a 1725 and it has all types of non-rootes parts to make it a better performer--it dyno'd at 138hp. We have made a few additional changes on the intake and exhaust side--we anticipate a solid 150hp--reliable power.
A friend and long time alpine race guy had done everything and a bit on the wild side to his car and ranged in the 160-170hp range but it was race quality--meaning, every other race the engine would need something.
I would be surprised if someone gets 160hp in a reliable, everyday driving engine.
Bill Atalla

 

[RootesRacer]

always sounded wrong to me (although it apparently isn't). The starting and stopping of the air flow as the valves open and close does not seem efficient. It would seem to dictate fewer venturi and longer, common intakes to maintain as constant flow as possible. Oh, please don't post any more photos of your set ups, I am starting to get depressed with my cruddy old Strom's...!

yeah but keeping the flow continuous (with restriction and downstream volume) is a rather restrictive way to carburate, plus the starting and stopping of the flow is not actually so, it in fact is resonant which can be exploited to fill the cylinders beyond 100% capacity (called volumetric efficency or VE). The highest power (in BHP per liter) naturally aspirated engines ALWAYS use individual runners per cyl, and have the smallest runner volume that will flow the desired rate to the head. This keeps the port velocity high, without being restrictive. Common plenum type intakes have inconsistent flow velocities as the flow goes from high volume to low volume, and reflects back into the plenum.

 

[alpine_64]

Jarrid,

Brians car is in a slightly different category given its a turbo. I think the HP we are talking baout here are all NA, so a better example might be your 1725 efi (that was 175bhp at the fly?)

The most powerful alpine motors i know of in AU are a stroker alpine on 45DCOE's thats putting out 150bhp and relaibly. The other was a 1592cc race motor custom roller rockers, pistons rods, pushers, etc.. 136KW at the fly on modified twin Zeniths.. but that was one VERY expensive motor.

 

[RootesRacer]

N/A vs turbo distinction not made...

Power is power although a turbo is far easier on the internals than buzzing the motor at 8000 RPM. Brians engine is built to take the revs, so IMHO we are talking about the same thing, that is a very high output engine that can rev into the 7000 RPM realm. His engine just happens to be able to make the 150 BHP figure without breaking a sweat.

My engine that was modeled to produce 175BHP (crank) was never tested on an engine dyno, it was however tested on a rolling road and produced 140BHP to the wheels. My estimate based on SWAG'd powertrain losses is 165BHP crank. Since this figure was done with twin 40mm webers (32mm chokes), when I put on the new EFI system with distributorless coil on plug, I anticipate 150 to the wheels, or what should match my original goal of 175 crank. If I dont get there on gasoline, there is always E85.

Jarrid,

Brians car is in a slightly different category given its a turbo. I think the HP we are talking baout here are all NA, so a better example might be your 1725 efi (that was 175bhp at the fly?)

The most powerful alpine motors i know of in AU are a stroker alpine on 45DCOE's thats putting out 150bhp and relaibly. The other was a 1592cc race motor custom roller rockers, pistons rods, pushers, etc.. 136KW at the fly on modified twin Zeniths.. but that was one VERY expensive motor.

 

[Jim E]

Tracy,
I may be alone in this but I really like the 150s on a fresh 1725 I was getting 30 MPG with no issues, flat spots or such. Something must be right about them IMO.

always sounded wrong to me (although it apparently isn't). The starting and stopping of the air flow as the valves open and close does not seem efficient. It would seem to dictate fewer venturi and longer, common intakes to maintain as constant flow as possible. Oh, please don't post any more photos of your set ups, I am starting to get depressed with my cruddy old Strom's...!

 

[Eleven]

Jim,

Tracy,
I may be alone in this but I really like the 150s on a fresh 1725 I was getting 30 MPG with no issues, flat spots or such. Something must be right about them IMO.

When they are right I don't have a problem with them either. Had them on my GT6 and it screamed. Mine are starting to leak air around the throttles and I am PO'd about the price to fix. I have the rear so rich that I doubt I am getting 20 mpg. Half the time I have to choke it slightly to stop it from stumbling. Besides that, the beauty of the set ups and quality of the workmanship on some of the cars here is outstanding. Makes my feeble efforts look very "Yip" ish.