This is all purely hypothetical, and I may have a fundamental misunderstanding of things but here goes. If the main limitation of using an HE engine for a race build is the exhaust valve shrouding and lack of high rpm breathing could one not reduce the displacement of the engine to a point where the valve flows the ideal amount or close to it?
If you did this by destroking the engine and making it more oversquare could it not pull more rpm and flow while doing it? I was reading about Burrows v12 parts and he goes with a 5.0L, I believe his stuff is for a flat head but would this not still work?
Kirbert
(Author of the Book, former owner of an '83 XJ-S H.E.)
2
What youāre talking about is taking a poor-performing 5.3 engine and making a good-performing 4.0 out of it. Itād still have less power than the 5.3, but itād look good for a 4.0. Of course, itād be the heaviest 4.0 ever.
maybe my thinking is better explained as: we know stock cylinder he heads flow āXā air max, what is the smallest cylinder size necessary to get that amount of fuel in and is that volumetric efficiency possible
Good question, but youād still need to pump the same volume for a given power output so I think Kirbert is absolutely right, youād have a good 4l instead of a restricted 5.4 and itāll still be heavyā¦
And while I donāt know about the restriction in detail, that restriction doesnāt change (then; would changing the resonance frequency of the intake help as bmw used to do?)
Tune per litre: yes, and more litres might still help
The smallest cylinder size to achieve needed flow is what bothers me: a restriction restricts; it doesnt completely stop flow, just lessens it, so you would do away with a slight reduction in flow by reducing the flow to less than it was before!
I can be just as wrong as you could be, but it seems theoretically logical at least.
David
Reminds me of an article I read in some hotrod magazine when I was in high school. It was titled āThe Almighty Inch.ā I thought that was true most of my life. But then I saw there Indy race cars with tiny little engines pumping out incredible power.
Ron
Power is actually kingā¦
Power is essentially about ārate of changeā.
Imagine pushing a 2 tonne car 10 metres. That is a certain amount of āworkā . This is measured in Joules and is a measure of energy. Say it is 100 Joules in this case.
Now if you add TIME to the story then you are talking power. Soā¦if you push the car 10 metres in 100 seconds then you have put a certain amount of power into the carā¦100joules in 100 secondsā¦which is 1joule per secondā¦which is 1 wattā¦1joule/second= 1 watt
Is you were asked to move the car 10 metres in 10 secondsā¦then you instinctively know that you are going to need ā¦say two more pushers.
So when you get to the 10 metres you have used 3x100joules in 10 secondsā¦which is 3joules/second which is 3 watts!!
You need 3 times the power to achieve this feat. This is the first calculation an Engineer does ā¦so you know how much power is required and then you know that Power is Torque X engine revs so you have to have a look at the power delivery curves of the engine you are going to use and select a range of gear ratios and engine speeds to keep maximum power pouring into the drive system. I have never done this for a car drive system but I have for several other electrically driven systems and this is how it is done.
Regards
Matt
Kirbert
(Author of the Book, former owner of an '83 XJ-S H.E.)
16
Iāve tried to explain that before. Itās a losing cause; too many non-engineers who simply cannot accept that torque is only part of the equation.
