Jump to content
SAU Community
  • Welcome to SAU Community

    Welcome to SAU Community, like most online communities you must register to view or post in our community, but don't worry this is a simple free process that requires minimal information for you to signup. Be apart of SAU Community by signing in or creating an account.

    • Start new topics and reply to others
    • Subscribe to topics and forums to get email updates
    • Get your own profile page, build reputation and make new friends
    • Send personal messages to other members.
    • See fewer ads!

    Consider joining our newsletter for the latest content updates

    Click here to register


N/a Modifications Explained


Recommended Posts

After reading that some people are getting fustrated at telling others that they shouldnt expect there n/a to be 100 times more powerful with basic modification's lets try and put one together with the help of everyone that explain why you do it what they do and what results should be felt or will happen to the engine....

how about

Part:

why:

Result:

and or Explaination:

Link to comment
Share on other sites

Part :CAI plus air filter or pod

Why : to reduce the ammount of restriction the standard system has and to give the car colder air

Explaination: The standard system cardboard filter is quite restrictive (poor water through paper then through a siv)

with a phome filter or good pod the air can flow more freely into the induction pipes through afm ect ect

Problem : Pod without CAI or proper box will turn out worse Hot air is less dense and has less oxygen (i think)... (heat saturation)

Solution: CAI to deliver colder air to the now better flowing pod or filter

Result: Possible..... slight!.... gain in power but more importantly allowing the engine to recive colder air at a faster rate allowing it to breathe better changing its efficancy and response

Link to comment
Share on other sites

Part : Extractors

Why: To help the exhaust "pulse" flow and the speed and rate the exhaust gas exits the car

Explaination: as the exhaust gas leaves each cylender we can now call this a pulse... on a standard system each pulse meets from each cylender along the pipe at the same place.

Result: extractors go 3 joints to 2 one joint to the end joint so this now pulls the pulses on the corrosponding cylenders down the pipes allowing them to escape better faster and in most cases louder :)

Car is now more efficant at removing the gases and will also deliver slighty higher results but again is more efficant

Link to comment
Share on other sites

Part : Extractors

Why: To help the exhaust "pulse" flow and the speed and rate the exhaust gas exits the car

Explaination: as the exhaust gas leaves each cylender we can now call this a pulse... on a standard system each pulse meets from each cylender along the pipe at the same place.

Result: extractors go 3 joints to 2 one joint to the end joint so this now pulls the pulses on the corrosponding cylenders down the pipes allowing them to escape better faster and in most cases louder :)

Car is now more efficant at removing the gases and will also deliver slighty higher results but again is more efficant

Thanks for the thread, I will now fill with my long and boring stories :)

On this

Good Headers/Extractors cost thousands, the ebay/other cheap ones are rubbish. If I ever get the time I will nut out a decent design for some and have a set made, because I am sick of seeing crap products being passed off as good.

Also Primary pipe length/size will vary depending on where you want peak torque/power, factory cams or aftermarket, Port work/valve sizes, whether you run mufflers or not, Exhaust pipe size and lenght all play a part in the design of the headers/extractors

So yeah, as an Eg, an old mate of mine who is an engineer has an XA falcon with a 383 cleveland that was putting out 430rwhp, It had a set of generic 1 7/8" 4 into 1 extractors.

We decided one day to nut out a new set with the aim of making bulk torque in the mid range to get the car off the line at the strip.

So many many beers (re: weeks) later we had the design (went shorter in the primary pipe length and increased the angle of the collector) he made them up at his shop, fitted them and went back to the dyno, the car picked up 10hp peak, but made 40 yes 40hp more at 4500rpm, just by changing the headers and altering the jets in the carb to suit.

Link to comment
Share on other sites

Part :CAI plus air filter or pod

Why : to reduce the ammount of restriction the standard system has and to give the car colder air

Explaination: The standard system cardboard filter is quite restrictive (poor water through paper then through a siv)

with a phome filter or good pod the air can flow more freely into the induction pipes through afm ect ect

Problem : Pod without CAI or proper box will turn out worse Hot air is less dense and has less oxygen (i think)... (heat saturation)

Solution: CAI to deliver colder air to the now better flowing pod or filter

Result: Possible..... slight!.... gain in power but more importantly allowing the engine to recive colder air at a faster rate allowing it to breathe better changing its efficancy and response

gains from a CAI depend on how well the factory intake was designed. some cars benefit more than others.

Part : Extractors

Why: To help the exhaust "pulse" flow and the speed and rate the exhaust gas exits the car

Explaination: as the exhaust gas leaves each cylender we can now call this a pulse... on a standard system each pulse meets from each cylender along the pipe at the same place.

Result: extractors go 3 joints to 2 one joint to the end joint so this now pulls the pulses on the corrosponding cylenders down the pipes allowing them to escape better faster and in most cases louder :)

Car is now more efficant at removing the gases and will also deliver slighty higher results but again is more efficant

there are different theories behind headers. for example, on a 4 cylinder some will run a 4-2-1 setup while others will run a 4-1 setup. length of the primaries and secondaries will determine where in the rev range the power comes in. primaries are the pipes immediately out of the head, secondaries are after the next join.

next comes the exhaust. a lot of people think bigger is better, and that is true to a point. others think you need back pressure and if you go too big the lack of back pressure is the reason why you can lose power by going too big. this is false. back pressure is bad in all exhaust systems, however sometimes you have to put up with it to get the power characteristics you want. if you want a car that is good on fuel, has plenty of pull in the lower rev range then you have to go a smaller exhaust. this will flow gases better at low rpm than a bigger exhaust due to a syphoning type effect that goes on. the downside is more restriction at high rpm. this is what the car manufactures base their exhausts off because on the highway, etc you aren't sitting at high rpm. if you put a bigger exhaust on you will lose a bit of low down power but gain high end power. this gain in the higher rev range often masks any loss in the lower rev range. if you go too big then you will lose even more low end power and it will become a slug for everyday use and might not gain any power up top. the same applies to extractors.

Link to comment
Share on other sites

Camshafts -

Difficult topic but i'll do my best.

The job of the Cam(s) is to open and close the valves, they are the true power maker in a Natmo engine

Altering when the valves open and close has a marked effect on power/torque peak rpm etc

In simple terms, Production cams are designed with a broad torque curve and smooth delivery in mind, and are generally quite mild, with low lift and a short duration.

Now if we want more air to enter the combustion chamber we can do many things, we can increase the amount the valve lifts off the valve seat, we can lenghten the aamount of time the valve is open for (duration) and we can alter the cam timing (advance or retard)

Now I have never seen an aftermarket Cam that only increases lift or only increases duration, it is a combination of both that nets the best result.....

....But at a cost, larger cams require more RPM to work, and move the power band further up the rev range the more lift and more duration means the engine loses low speed efficiancy (no doubt you have all heard a lumpy idle on a hot rod or drag car) This in the case of very large race cams, requires stronger/lighter conrods/crank shafts/valve train etc that can withstand the higher RPM needed.

Larger cams also bleed off more cylinder pressure out the exhaust valves during the compression stroke (due to the valves being open for longer) So you effectivly lose compression (this is called dynamic compression) , so higher compression pistons are required to mantain the same dynamic compression ratio.

They also need modifications to the ports (commonly called port and polish) , there is no quicker way to kill the performace of a car than to stick huge cams in the motor and leave the ports and compression ratio as is.

So the heads need to be ported to match the cams, usually focusing on gas velocity (bigger ports are not always better, and in some cases the ports are filled with epoxy to make them smaller and therefore increase velocity)

I wont go into to how to choose a cam as there are too many variables.

But there are two different way to measure a Cams duration, there is Total duration, and duration a .050" lift, what that means is they count the duration from when the valve has actually lifted off the valve seat and can start flowing air.

All the Japanese cams are listed as Total duration, so while a 280degree cam sounds huge for a small motor (like an RB) the actual effective lift is closer to 235degrees depending one which brand of cam it is (some are more some are less)

I think I should also mention this - The more duration the further the powerband moves up the rev range, so you will often see something like this.

In - .513 236deg @ 050

Ext .530 240deg @ 050

^^ that there is a basic performance V8 camshaft (I just made it up btw) the duration as you can see is at .050" lift

and would give a 5L V8 good power upto around 6000rpm

Along side those details you will see something like

4000-6500

That is to give you an indication of where the powerband will be.

May also give info like

Rough idle, needs high compression pistons, 4000rpm stall or manual gearbox

Now if I saw something like that, I could make a choice, I would look at my current engine and think, "can it rev to 6500rpm without falling apart" "can I live with the rough idle and limited power below 4000rpm or do I need something smaller/larger" "Is my Stall converter large enough to get the car into the powerband at the drag strip?"

Things like that are what you need to think about, most street cars Dont need huge cams, just makes them a pig to drive and use heaps of fuel.

Also notice that in the cam specs they DO NOT give an estimated power or torque figure, that is because there are WAY too many variables to give an accurate figure.

I hope this helps.

Any questions let me know.

Andrew

Link to comment
Share on other sites

cams simply open the valves longer and further than the stock ones, allowing more air and fuel into the engine.

head work increases the speed and volume of air that can enter the combustion chambers.

injectors allow more fuel to enter the combustion chamber. as you increase the amount of air that enters you need to increase the amount of fuel to keep the air fuel ratio right. petrol requires a certain amount of oxygen to get maximum bang. different fuels (alcohol fuels, etc) have different optimum levels.

damn, zebra keeps beating me to it (and with more details, lol)

Link to comment
Share on other sites

do those Pon cams work with the n/a standard ecu like they claim to work thith the turbo one or is it differant ? is there a very small step one cam that will work a little bit better than standard ....with standard internals or once u step into cams u should always get head work done ?

Link to comment
Share on other sites

i'm going to go a little bit different now. suspension.

everyone thinks lower, stiffer suspension is better. this isn't always the case. lower is better because it lowers the centre of gravity, reducing body roll and keeping weight more even across the tyres, thus giving you more grip. stiffer suspension also aids in this. there is a limit to how stiff is good. on a rough road then super stiff suspension will give you less grip than a softer suspension as the stiff suspension will cause the car to skip over the bumps rather than absorb them, but on a super smooth road then you can go a bit stiffer. stiff suspension does put more strain on other parts of the car though. things like engine mounts, gearbox mounts, etc will all wear out faster because they are getting more stressed. in the case of drag cars though, softer suspension (at least in the rear) is a benefit because you get more weight transfer to the rear of the car and more weight over the rear tyres then the less wheelspin you will get. stiff suspension on a car will actually make it harder to get off the line cleanly, so if you ever see a car setup for drift at the drags you will usually see pretty crappy 60ft times from them compared to a car with stock suspension.

Link to comment
Share on other sites

do those Pon cams work with the n/a standard ecu like they claim to work thith the turbo one or is it differant ? is there a very small step one cam that will work a little bit better than standard ....with standard internals or once u step into cams u should always get head work done ?

unlike aftermarket ecu's, most stock ecu's will adapt to simple mods as they have a fair bit of headroom above where they are running standard. aftermarket ecu's are tuned specifically for the car and are generally running closer to the limit (hence why they put out more power than the stock). that said, if you do make a change to something like cams then the gains you get from the individual mod will be greater with the aftermarket ecu since it can be tuned to make the most of the mod rather than simply adapting to it the best it can.

Link to comment
Share on other sites

http://www.cranecams.com/268-269.pdf

This is one of the best cam catalogues I could find relating to Import performace motors, You can see what I was talking about regarding what the cams require.

There is other info in there, Such as lobe separation angles etc, I deliberatley left that out, but I will touch on it briefly

the Lobe separation Angle or LSA is the angle between the Intake and exhaust lobe (which is the lumpy bit on the cam that makes the valves open)

This can be altered on RB engines by the use of adjustable cam gears (which is why I didnt mention it) But plays a bit part of older Engine cam engines (eg Rb30 or American V8s)

But the closer the angle eg 110degrees in the case of the EVO motor above means the engine will produce more top end power than say having them set at 114degrees.

It is effectivly the amount the valves overlap, eg the intake valve opening while still on the exhaust stroke, or vice versa, and you can see that info where it says

Open/Close

@ .050”

Valve Lift

Int/Exh

That tells you when in the 4 stroke cycle the vavles are open or closed.

Link to comment
Share on other sites

hmmm $880 dollars for poncams ? worth it for the results with the standard system ?

In short no, the car will run yes, but wont net any real gains without a decent exhaust at the very least.

Also Cams for turbo engines differ greatly to NA engines. So while you can have a 260deg 8.8mm lift cam for a turbo engine and an NA engine, things like the LSA and the ramp rate of the cam lobe are quite different.

So while the Poncams etc would work ok, there would be better results had by getting a custom set done specificly for your NA engine.

Link to comment
Share on other sites

does a lower car also have a better or worse aero dynamic efficancy ?

would very much depend on the car. what most people think of when thinking about aero effeciency is the front of the car, however it is often the rear of the car that makes the biggest difference. for example, back in the late 80's and early 90's volvo racing cars were wagons as they were better aerodynamically than the sedans, despite having the same front end. a lot of cars actually get a big swirling vortex at the rear of them which creates a low pressure area behind them. this actually sucks them backwards a bit. anyone who has driven a station wagon or hatchback in the rain will see how much spray from the tyres ends up on the rear window. if you look at the back of a lot of wagons you will see a little spoiler type thing that directs air downwards (my vt wagon has one). this helps to reduce the vortex, or at least move it further back from the car to reduce its affect.

this vortex does have 1 advantage though. if you happen to be able to get behind a truck on a bike then you can really get some speed up without much effort.

Link to comment
Share on other sites

does a lower car also have a better or worse aero dynamic efficancy ?

Depends on what you mean by "Aero dynamic efficiency" and on what car you are talking and what you mean by "a lower" car.

Will lowering your stock GTS Skyline 1" off the ground make it handle awesome? No.

Link to comment
Share on other sites

Part: Splitfire , super spark . yellow jacket ..... coil pack

why : standard coil packs burn out ... they work in extremely hot conditions and with really high ammounts of electricity

burn out means eventual engine light and horrid missfire usualy in the conditions late at night in the rain and no were near a work shop :P becasue the spark is not going were it should

results : desputeable gain but more importantly relyability :) and not having to baby your car home couffing farting spluttering and carrying on

Link to comment
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
 Share



×
×
  • Create New...