# Why don't auto manufacturers build V8 engines smaller than 4.0 liters? **URL:** \ **Category:** Factual Questions\ **Created:** [January 14, 2004, 10:49pm UTC](https://boards.straightdope.com/t/why-dont-auto-manufacturers-build-v8-engines-smaller-than-4-0-liters/224471 "2004-01-14T22:49:50Z")\ **Posts on this page:** 5\ **Page:** 2
**Author:** ![Duck\_Hook](https://avatars.discourse-cdn.com/v4/letter/d/91b2a8/32.png) [@Duck\_Hook](https://boards.straightdope.com/u/Duck_Hook)\ **Post date:** [January 15, 2004, 8:32am UTC](https://boards.straightdope.com/t/why-dont-auto-manufacturers-build-v8-engines-smaller-than-4-0-liters/224471/21 "2004-01-15T08:32:48Z")
> [@dutchboy208](#): > > Besides, the truth about the Alfa Montreal experiment is obvious to anyone who’s driven one. Yes, it was a wonderful motor, with an nice smooth powerband, and it sounded great. Unfortunately, like almost everything Alfa built from about 1964 onward, it fell apart quicker than the model aeroplane I built out of polystyrene and a cannibalized r/c car motor when I was eight. > > That engine quite literally shook itself to bits. That seems to point to Alfa’s quality control problems and not an inherent flaw in the concept. ---
**Author:** ![Dog80](https://avatars.discourse-cdn.com/v4/letter/d/6bbea6/32.png) [@Dog80](https://boards.straightdope.com/u/Dog80)\ **Post date:** [January 15, 2004, 8:43am UTC](https://boards.straightdope.com/t/why-dont-auto-manufacturers-build-v8-engines-smaller-than-4-0-liters/224471/22 "2004-01-15T08:43:55Z")
[http://www.e31.net/engines\_e.html](http://www.e31.net/engines_e.html) ---
**Author:** ![Dog80](https://avatars.discourse-cdn.com/v4/letter/d/6bbea6/32.png) [@Dog80](https://boards.straightdope.com/u/Dog80)\ **Post date:** [January 15, 2004, 8:50am UTC](https://boards.straightdope.com/t/why-dont-auto-manufacturers-build-v8-engines-smaller-than-4-0-liters/224471/23 "2004-01-15T08:50:04Z")
If engine sound is your only concern, you can get that V8 rumbling from a 4 banger by splitting the exhaust manifold. Instead of a single 4-2-1 or 4-1 manifold, you can use two 2-1 manifolds with slightly different pipe lengths. I’ve heard it is very effective! ---
**Author:** ![Desmostylus](https://avatars.discourse-cdn.com/v4/letter/d/c57346/32.png) [@Desmostylus](https://boards.straightdope.com/u/Desmostylus)\ **Post date:** [January 15, 2004, 9:24am UTC](https://boards.straightdope.com/t/why-dont-auto-manufacturers-build-v8-engines-smaller-than-4-0-liters/224471/24 "2004-01-15T09:24:10Z")
The two main advantages that can be gained through having more cylinders: 1. Better balance, and so less vibration. This has become pretty irrelevant these days, with better understanding of the problem, more experience, etc. Vibration from a big 4 cylinder Toyota engine, for example, is a lot less than from a 1970s vintage V8. 2. Shorter stroke. For a given physical engine length, if you double the number of cylinders from 4 to 8, you can keep the bore pretty much the same and halve the stroke. This halves the maximum piston speed for any given rpm. Assuming you’re using similar materials for both engines, that would allow the V8 to safely achieve double the rpm. So your 7,000 rpm redline 4 cylinder could go up to 14,000 rpm in V8 configuration. Torque is proportional to engine capacity, but power is proportional to both engine capacity and rpm. The 120 kW 4 cylinder engine could be turned into a 240 kW V8. This is precisely why Formula 1 engines, which are of limited capacity, tend to have more than 4 cylinders. But Joe and Jane Public tend not to like running engines in “screaming” mode. It’s better from a marketing perspective to just stick a supercharger on the 4. ---
**Author:** ![Desmostylus](https://avatars.discourse-cdn.com/v4/letter/d/c57346/32.png) [@Desmostylus](https://boards.straightdope.com/u/Desmostylus)\ **Post date:** [January 15, 2004, 10:45am UTC](https://boards.straightdope.com/t/why-dont-auto-manufacturers-build-v8-engines-smaller-than-4-0-liters/224471/25 "2004-01-15T10:45:37Z")
> [@Desmostylus](#): > > For a given physical engine length That should read “For a given **engine capacity and** physical engine length”. [Previous page](https://boards.straightdope.com/t/why-dont-auto-manufacturers-build-v8-engines-smaller-than-4-0-liters/224471.md?page=1)