Thought I'd ask Chatgpt

[bmw2800cs]

AI will undoubtably lead the path to our dystopian future, until then we can ask questions like this one . Yes it got the stock carbeurator wrong on a 2800cs. Thoughts? How did it do?

Question:
If I put three Weber two barrel DCOE 40MM carburetors in my 71 bmw 2800cs and a more aggresive cam what will my horsepower be?

ChatGPT said:​

If you're putting three two-barrel Weber DCOE 40mm carburetors (total of 6 throttle barrels) on your 1971 BMW 2800CS (E9), and upgrading to a more aggressive cam, you're making serious performance modifications to the engine. Let's break this down and estimate horsepower gains.

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​

• Engine: 2.8L inline-6 (M30)
• Stock HP: ~170 hp @ 6000 rpm (SAE gross), ~150 hp (DIN net)
• Induction: Single downdraft Solex 4A1 carburetor (or sometimes Zeniths) - Wrong!
• Compression: ~9.0:1
• Very mild camshaft, built for drivability

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Your Upgrades:​

1.​

• Big improvement in airflow and fuel delivery
• Much more responsive throttle
• On a healthy M30, this alone can add 20–30 hp, especially with proper jetting and tuning

2.​

• Higher lift and longer duration = more power at high RPM
• Depending on the cam, expect another 15–30 hp
• May sacrifice low-end torque for high-rpm power

 

[bmw2800cs]

Estimated Horsepower:​

Here are some ranges depending on how far you go with tuning:

Setup	Estimated HP (Net)
Carbs + mild cam	190–200 hp
Carbs + aggressive cam + headers	200–215 hp
Fully built (head work, high comp, tuning)	220–240 hp

Realistically, with triple DCOEs and a good cam on a healthy engine, 200–215 hp is a solid, streetable expectation without needing a full rebuild.

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Notes:​

• Tuning is critical – DCOEs must be correctly jetted for your engine and altitude
• 40mm chokes are good for a 2.8L, but if you go extreme, you might want 45mm for top-end
• Drivability: You may lose some smoothness and cold-start ease, but gain big in responsiveness and top-end power

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Would you like help picking a camshaft spec or jetting for your Webers?

 

[Honolulu]

IIRC there were M30 motors with a single carb and manifold to match, I just don't recall which cars them. Could be E3, E9 or E12.

 

[bmw2800cs]

IIRC there were M30 motors with a single carb and manifold to match, I just don't recall which cars them. Could be E3, E9 or E12.

Maybe a 2500cs?

 

[Stevehose]

I think realistically it is the bottom # of each range.

IIRC there were M30 motors with a single carb and manifold to match, I just don't recall which cars them. Could be E3, E9 or E12.

Yeah - 5 series

 

[Bmachine]

I have been very impressed with the quality of some of the responses I have had from chatGPT, and this on all types of subject,. Especially the new version 5.0.


Of course, it really pays to double check the responses if an important decisions hinges upon them. So I often ask "What are your sources for that information?"

 

[Mike Goble]

IIRC there were M30 motors with a single carb and manifold to match, I just don't recall which cars them. Could be E3, E9 or E12.

I have an M30 with a Quadrajet on a Euro 4-bbl manifold.

 

[bmw2800cs]

I have an M30 with a Quadrajet on a Euro 4-bbl manifold.

Yeah I remember you mentioning that a while back. Is it easier to tune a 4 barrel instead of 2, 2 barrels?

 

[Mike Goble]

Yeah I remember you mentioning that a while back. Is it easier to tune a 4 barrel instead of 2, 2 barrels?

Much easier. No synchronizing. No external linkage to adjust.