V8 or V4

S0lo · Posted: Sun Mar 15, 2009 10:57 am Post subject: V8 or V4

This guy keeps telling me that the newer v8 BMW engines have this economy feature that when at low speeds works on 4 cylinders and when it runs at more than 80Km/h it works full capacity on 8 cylinders!!!

He knows a bit about cars, but I just can't get this into my head. How in the world would an engine do that without the driver feeling any thing at all, not to mention other technical difficulties. Did any one hear any thing about that? I couldn't find any references about it and he couldn't give me any either.
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rizin · Occasional Member Joined: Oct 20, 2005 Posts: 52

Perhaps possible, i had felt the speed difference and performance while driving the different old and new model cars with 4 cylinder capacity. if the difference itself in 4 cylinders Why not with v8 Smile

When you drive some new cars you feel the difference comparing to old model 2003 cars Both run on 80 km/hr But there is increased speed in new cars.

Apparently it is not only with volume of cylinders but with other advanced technical methods applied on camshaft and fuel injection etc..

Well Shall we know the brand name of your car Wink

How Would be a Car manfuctured by the brand name FIREWALL Smile

Rizin
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S0lo · Posted: Mon May 18, 2009 11:54 pm Post subject:

Thanks for the feedback rizin Smile

, I agree with you on all. But I think I did not explain it really well. This guy is telling me that the SAME V8 car runs at lower speed on only 4 cylinders. In other words, 4 cylinders will be moving and the other 4 are STATIC!!, not moving at all!!, until the car reaches a certain speed, then those static cylinders suddenly start to move, and the car moves on 8 cylinders!!

So under 80Km/h, it's a V4, over 80Km/h the SAME car is a V8!!!

I find this really wild, I can't begin to believe it.
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TheBishop · Posted: Tue May 19, 2009 12:13 pm Post subject:

I find that improbable. All the cylinders are connected to the same crankshaft so they will all be moving. However I suppose it's possible that only four of the eight will be generating power - i.e. undergoing compression and recieving fuel - and the others will be brought on-line when extra output is needed. You could do that with the fuel injection computer. You might get a bit of extra economy that way I suppose, but it sounds like a lot of effort for the return. Unless the engine drives two separate crankshafts that have their output combined in some way then I don't see how it can be done

S0lo · Posted: Tue May 19, 2009 10:04 pm Post subject:

TheBishop wrote:

You could do that with the fuel injection computer. You might get a bit of extra economy that way I suppose, but it sounds like a lot of effort for the return. Unless the engine drives two separate crankshafts that have their output combined in some way then I don't see how it can be done

Ya, give me more of that TheBishop Smile

. That sounds much more understandable. The "fuel injection computer", hmmm put more fuel here than here. Ya I could buy that Cool

.

The thing about the "two separate crankshafts" is that (I think) that the driver has to feel a jump or a change in engine tone or something when the transition from 4 to 8 happens. I drive the BMW V8, but I never noticed that. I might be wrong.
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Every solution breeds new problems.

Ammar Muqaddas
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www.firewall.cx

E_Money · Posted: Sun Jun 27, 2010 7:00 pm Post subject:

Your friend is correct. There are also a few trucks in America that have the same function. Dont know why they didnt think of that years ago.

Do they actually make 'v4's in kuwait or do you mean a i4 ( inline )??

Nevins · Enthusiastic Member Joined: Jan 26, 2010 Posts: 217

There is only one thing I look at on cars: Total cost of ownership over 6 years.

Purchase price + Matiance (6 yr) + gas (6 yr assume 40% bump in gass cost)= TCO(6yr)

All other thing are relitively not in my scope of planning.

TheBishop · Posted: Thu Jul 01, 2010 1:49 pm Post subject:

If it's true, how does it work then?