Hey all wrote this up about 4 months ago in word, never got around to finishing it as I lost my Rolla and interest for now tongue.gif
So I may as well post up what I had typed up even though it is not really finished
Might be of help to N.A 4age fans wink.gif
Matt’s Modified N.A 4AGE Page
For modifications to the GEN 1, 2 & 3 4AGE 16v
( TVIS Bigport’s and the Smallport )
First some basic back ground info for better understanding:
What is Camshaft duration & lift?
Camshaft lift is measured from the top of the base circle to the tip of the lobe. In this case, the lift is 7.1mm. This lift is generated over 116 degrees of cam-lobe duration. Since the cam spins at half crankshaft speed, you double the duration to come up with an advertised duration of 232 degrees.
If you have a 7.1mm lift cam this douse not mean your valves open up 7.1mm they actually open up less due to the Valve clearance that you set with the Shims.
Standard clearance is 0.15 to 0.25mm for the intake & 0.20 to 0.30mm for the exhaust
So if they’re set to 0.15mm your valve will open 6.95mm
The above drawing I based measurements on a standard Smallport cam shaft.
The Bigport camshaft is 240 duration & 7.56mm lift
Aftermarket performance camshafts are designed to open the valves more and for a longer period. When you build performance N.A engine’s you normally need to run a much higher RPM to make more power then the standard engine would make.
Performance Camshafts are designed to keep making the power at those higher rpms you need to run, though the downside of this is you loose your bottom end power.
So the bigger profile of the camshaft the higher the RPM range you make peak power at and the less bottom end you will have. Also the engine must be made to idle at a faster rpm. The bigger the cam the faster it must idle depending on the tune.
It would also determine how street able the engine would end up being.
Advancing and retarding Cam shafts what does it do?
To advance and retard your engines cam timing you would need to buy a set of adjustable cam gears, you could skip a tooth on the cam gears but this would be too much and affect the performance of the engine.
The Crankshaft does 720 degrees for 1 complete cycle, In that time the camshaft has done 360degrees
The 4age has an 18tooth crank gear to spin the 36tooth camshaft gears at ½ engine speed.
So 1 tooth on the cam gear is 10 degrees for the camshaft on the 4age 16v engine
Advancing your camshafts will move the standard power curve of the engine which would give you a low to midrange power
To do this you must rotate the cam gears in a clockwise direction.
Retarding the cams will do the opposite, give you more mid to top end power
To do this you must rotate the cam gears in an anti-clockwise direction.
Usually when buying performance cam shafts they come with a cam card that tells you at what degree the camshafts need to be dialed into.
Dialing in cams is when you place a degree wheel on the crank shaft and two dial indicators on the shims/lifters.
One for intake side and the other for exhaust side. This is so you can set the cams to exactly the right degree to start opening or closing the valves.
It is also a good
for a third dial indicator down the spark plug hole if you can, so it can sit on the piston to check TDC and the degree wheel has not moved when your rotating the crank.
This is the cam card that came with my 270duration & 7.9mm lift cams
They are designed as a midrange camshaft and improved the torque of the engine much more then it gave power as the peek rpm they are designed for is near standard.
Reduced: 69% of original size [ 741 x 383 ] - Click to view full image
After installing these cams the engine became very responsive and peaked much faster then a standard 4age. The power Curve in result was much more aggressive. The only downside is I lost power under 4000rpm, and it idled very lumpy at 900rpm.
Engine Balancing:
Engine balancing is when we make the rotating and reciprocating mass the same weight so the engine spins more free and smooth,
For an example an unbalanced engine is like running as fast as you can with a brick stuck to one foot.
I wont go into it too much as it is not something that can really be done at home, Though if you are thinking about building a performance engine I would seriously recommend it getting done buy a professional.
3 angle valve seats!
3 angle valve seats in the 4age or any modern engine for that matter you will find is standard from factory.
The reason for this is so the air can flow past the seating aria more freely (More air into combustion chamber) then it would with just a 45 degree seat common on much older engines.
There are 5 angle seat cutters, so you can have 5 angle seats witch would be better again.
Facing valves!
Normally valve faces are ground to 45 degrees to match the seating aria to seal the ports off from the combustion chamber when valves are closed.
To improve the flow of the valves you can have a back cut ground above the face of about 20 degrees or so. Not sure how much difference this modification will make as I did not do it on my engine as my ports and valves where pretty much stock.
This pic I drew may help understanding.
Reduced: 82% of original size [ 620 x 370 ] - Click to view full image
Piston, Con Rod & Crank shaft terms:
Compression Ratios:
Compression ratio is the volume of a combustion chamber and cylinder, when the piston is at BDC and the volume when the piston is at TDC. The higher the compression ratio, the more mechanical energy an engine can squeeze from its air-fuel mixture. High ratios place increased oxygen and fuel molecules into a reduced space allowing for increased power at the moment of ignition.
This link is a quick calculator to work out your compression ratio.
http://www.csgnetwork.com/compcalc.html
Engine Power Calculator
HP = C.I. / 150.8 x RPM / 5252 x C.R x (14.7 + boost) x V.E.
C.I = Cubic Inch
RPM = The rpm in which it makes it’s max power
C.R = Compression ratio
V.E = Volumetric efficiency
V.E is a percentage so when you put it in the math formula if it is 99% you would put .99 if it is 102% you would put in 1.02
EG:
Workings for a Smallport 4AGE 16v
98/150.8x7200/5252x10.3x14.7x.99 = 133.5hp
Standard 4A-GE 16v Bigport VE = 1.02
Standard 4A-GE 16v Smallport VE = .99
Also bit of useful info, there is about 19.4kw Loss through a C52 gearbox and final drive in 3rd gear
Building a 4AGE 16v N.A engine
There are many different things you can do to a 4AGE 16v engine to make them perform better then standard. You may have cold air induction or a nice set of extractors installed for a little extra power (2-3kw maybe?), the real difference to be made is buy pulling the engine down and machining and replacing parts for performance items.
The first thing you could try is installing some small profile camshafts. They say that the biggest camshaft the standard ECU can take is around a 264 duration cam, when I installed a set of midrange 270’s the stock ECU could barely keep the engine running. So a piggy back computer had to be fitted to sort it out. Any bigger then a 270 duration cam and it would defiantly need to go to a complete aftermarket ECU.
As the cams I installed had an advertised power range of 3000rpm to 6500rpm they did not make much more power then the standard engine as the peek power was around the same RPM. What the cams did do to it is give it a bag full of torque.
To make a bit more power with that size cam you could give it more compression.
The late model 4age’s run around a 10.3:1 compression ratio.
To achieve more compression you could get the cylinder head face machined down to decrease combustion chamber CC. The standard 4AGE 16v combustion chamber CC is 38-39cc. Machining it down to a 36cc combustion chamber on a standard 4AGE 16v will leave you with a CR of around 10.8:1 , and an increased power over a standard 133.4hp 4age of 6hp (4.47kw) in theory.
So the only real way to improve the power is bigger cams. If your after more top end power I would recommend something around 290duration & 9mm lift as this cam would make power around 8000 – 8500 rpm. Though it would be a very good
to install some aftermarket Valve springs that can take the 9mm lift without the spring coil binding. It would also have to be a stiffer spring so that it can take the rpm’s and close the valve in time before it reopens.
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