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Location:
The Eastwood MASSIVE !
Registered:
May 2003
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Headers and exhaust camshaft modding.
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Wed, 15 October 2003 08:21
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I do enjoy tuning and modding my 4afe , makes a great hobby for me being a 1st year apprentice mechanic . And as a first engine its not too bad. At the moment the exhaust system consists of a " highflow cat " and a 2" exhaust ending in a straight through muffler.
Now I was reading that a respectable amount of power can be brough out of this engine by fully unlocking the exhaust system on this engine. Two things that were mention were 4-1 headers and altering the timing on the exhaust cam.
If anyone knows of information on either 4-1 headers for a 4afe , hey if they are only like 100-150 bucks why the hell not ay , or knows of articles concerning altering the exhaust cam shaft timing through the internal sissor gears then can you point them at me please 
And as for posts concerning " get a better engine and such " these are unneeded as yes I have an engine conversion in progress but I feel that small mods like this help me to greater understand dynamics of engines as a whole and I do love working on my little beast.
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I supported Toymods
Location:
NE Melbourne
Registered:
May 2002
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Re: Headers and exhaust camshaft modding.
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Wed, 15 October 2003 12:14
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i could be totally wrong, but reading your post got me to thinking...
if you want to alter the exhaust cam timing, you will have no other choice but to either advance or retard the cam by one full tooth on the sicsor gears which it drives off the inlet cam. because of this arrangement there is no other way to alter the timing of one cam relative to the other (except for having custom cams made with altered timing in relation to the drive gears - unjustified cost for such an engine)
for this reason you will have to consider just how much moving the exhaust cam one full tooth will advance/retard it in degrees. this is simple, just divide 360 by how many teth are on the scissor gear. off the top of my head this seems like it will be a lot ( how many teeth are on these gears???), and i'm not sure that such a large increase (if it is infact large) will make the engine any better.
then there is the other school of thought, if Toyota could get extra power by just altering the exhaust cam timing, why didn't they just do that from factory??? (emissions issues aside of course)
IMHO, whoever suggested the exhaust cam timing alterations is pissing in your pocket!!!
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Location:
Kita-Ku, Sapporo, Japan
Registered:
January 2003
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Re: Headers and exhaust camshaft modding.
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Wed, 15 October 2003 12:31
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good to hear you are actually interested in modding the engine rather than just bolt ons and gold dipped wheels 
4-1 extractors are primarily best at high rpm, like above 6000rpm. below that, you will still benefit from their free flowing nature, but you would be best making up a 4-2-1 tuned length set. should be pretty easy for a FWD motor, and may or may not make a difference. making the primaries and secondaries around 1.5 feet long would be a good start and will tune for maybe 4500-5000rpm?? the collector (the last pipe) shoudl be about twice as long as the first sections (ie 3 feet, if the others are 1.5 feet each) before the cat, although this will prolly make the cat less effective (less heat in it).
as for exhaust cam timing, retarding will increase overlap, and may help draw more new charge thru the intake valve (scavenging effect) ... but the cost of getting adjustable timing gears made up might be bad.. you could always drill new dowel positions on the sprocket to offset it, cheap if you have a machining buddy...
then you can muck around with it and see how it affects things..
imho, the best way to learn is have a go, and don't be afraid to start with an 'unpopular' motor
have fun,
Cya, Stewart
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Location:
Lost in the K hole
Registered:
May 2002
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Re: Headers and exhaust camshaft modding.
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Wed, 15 October 2003 13:12
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| dorikin wrote on Wed, 15 October 2003 22:14 |
just divide 360 by how many teth are on the scissor gear
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actually, its 720deg, as the cmshafts rotate once for 2 crank revolutions... suddenly i cam gear tooth become very large!
| oldcorollas wrote on Wed, 15 October 2003 22:14 |
imho, the best way to learn is have a go, and don't be afraid to start with an 'unpopular' motor
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like say, a 7mge?
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Registered:
August 2002
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Re: Headers and exhaust camshaft modding.
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Wed, 15 October 2003 13:26
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Location:
The Eastwood MASSIVE !
Registered:
May 2003
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Re: Headers and exhaust camshaft modding.
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Thu, 16 October 2003 07:52
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Well after doing a fair bit of research and actually taking a opened up 4afe head , not mine hehe , The external cam gear sits on the exhaust cam , judging by the placement of it and relation to my own engine and its headers. So this means the exhaust cam drives the inlet cam off the internal gearing. Talking to some poeple in the know it looks like the gears cannot be removed from the sissor gears and remeshed as it would ruin them.
At a glance I think there was about 50 odd teeth on the gears. this means that using the 720 degree and 50 teeth , one tooth is 14.4 degrees , way too much to consider jumping teeth.
As for the headers , the fuel cut of the engine is 6300 , the engine will always hit 6000 with the CAI and advanced timings , so I'm not sure if 4-1 or 4-2-1 headers would be best. This is of course if they are not too pricey as the gains would hardly be worth it.
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