Camshafts, where??? Options

[KAMiX]

kwanza I think you're wrong with the exhaust mate..

My muffler shop (huge performance experience) were telling me that going 2" upto 3" on the 6th gens doesn't lose ANY power whatsoever - and they showed me some dyno runs to prove it - mainly of lancers and celicas/corollas with 2.5" and 3" systems.

I was talking to them about this as I am planning on doing the swap, but want to get exhaust first.


From what I understand you only have to key in the exact size exhaust on turbo cars.. although he said going with a 3" on my engine will make it sound ****ING loud

[Kwanza]

QUOTE (kamixZR @ Apr 26, 2003 - 12:04 AM)

kwanza I think you're wrong with the exhaust mate.. My muffler shop (huge performance experience) were telling me that going 2" upto 3" on the 6th gens doesn't lose ANY power whatsoever - and they showed me some dyno runs to prove it - mainly of lancers and celicas/corollas with 2.5" and 3" systems. I was talking to them about this as I am planning on doing the swap, but want to get exhaust first. From what I understand you only have to key in the exact size exhaust on turbo cars.. although he said going with a 3" on my engine will make it sound ****ING loud

Sorry, but your exhaust shop seems to be confused. In Austrailia, I'm sure there are a bunch of turbo charged Corollas, Celicas, and Lancers, which will feel gains from large exhaust systems (2.5" to 3.0"). As far as a n/a 4 cylinder goes, excessive airflow creates very low back pressure, which is essential for the engine to function. It's sort of difficult to explain, but I'll try.

Here's a comparison: When you run/jog, you get tired right, and thus you need to breath harder, to inhale enough oxygen to get to your blood. Ok, now let's say you're running a relay in Death Valley, and then one in Aspen, CO (note the differences is elevation...but disregard heat/cold...we're talking about backpressure here). You will get more tired in CO than in Death Valley, why, because of the thinner air, easier flow, and less backpressure. I know it's not the best example, but crap...it's not easy to just explain.

Ok, back on to cars now... now we have a relative idea of what backpressure is, let's say you do slap on a 3" exhaust on your car. Your car will be pushing air out so fast, you'll hit negative psi of backpressure (if that's possible). By doing so, your car will tire and suffocate because it feels it's not getting enough air (and no...intake fans and stuff aren't enough...but forced induction is) Either way, there's a sweetspot, in the exhaust pressure than you want to try and control. Letting too much out too fast, you'll lose a lot of low-end power. Not letting enough out, creates excessive backpressure (restriction) in the exhaust.

Get it now...?

This post has been edited by Kwanza: Apr 26, 2003 - 11:28 PM

[SuperMica]

Nice little info. section and hay thanks for filling me in about back pressure.

[jayi12-15psi]

west once told me that the cams (at least on the 5s) will actually improve drivability. I think he also said that the crane regrinds produce almost 30 extra horse(correct me if I am wrong). but I'm not to sure about on the 7afe

[3TST]

Lets try and get back to basics on this.
You need to understand the engine firing cycle first. This is how I remember it...
suck, squeeze, bang, blow.
The fuel mixture is forced into the cyclinder on the down cycle of the piston (suck), the pistons compress the mixture on the up cycle of the piston (squeeze), the plugs ignite the mixture causing a down cycle of the piston (bang) and the gases are evacuated on the up cycle of the piston (blow).

So what does this have to do with the camshafts?
You have to understand what the camshafts do.
They open the intake valves to allow the fuel mixture to enter the cyclinder and then, after the firing seqeunce, they open the exhaust valves to allow the burnt gases to evacuate the cyclinder.

An increase in the the amount of mixture in the cyclinder means that the piston has to work harder to compress this mixture.
If you have an increase in mixture then you'll have an increase in the burnt gases thus you need to evacuate the gases better.

If re-grinding/upgrading your camshafts, to get maximum effect, you'll need to upgrade your air/fuel distribution, ignition and exhaust.

Hope that sheds some light on the issue.

[west_minist]

[3TST]

If your in Italy try:
http://www.colombo-bariani.com/storia.html

[BlackSTX]

[3TST]

Here are a couple of other sites that I found that might help with the explanation on camshafts:
http://www.drschrick.de/english/index.php
http://www.arrowprecision.co.uk/

Basically, an increase in the degree of the cam has the effect of opening the valve for a longer time thus this is the duration that the valve is open.
If the valve is open longer then this allows more air/fuel mix into the cyclinder (suck cycle) and more gases let out (blow cycle).

Something to bear in mind is that in order for the cams to meet there full potential other mods need to be done: air, fuel, ignition and exhaust upgrades.
(One example, no point in the the exhaust valve opening longer if the header is restricting/can't cope with the extra gases being forced out).

This post has been edited by vphmc: Aug 25, 2003 - 5:59 PM