K10 Max Power (split)

[SammoHung]

Original thread - http://www.micra.org.uk/showthread.php?t=2890

you will only go through gearboxes if you mistreat them

MA series with 4 branch exhaust manufold, full system, aftermarket air filter and a weber carb? In my opinion, its no better than a bog standard MA10 engine, except its not as smooth, louder, worse on fuel and looses its bottom end torque.

IF you want to go fast, simply get a faster car, or put a bigger engine in.

I was recently advised by a custom exhaust & maniflod designer & fabricator that; for the case of a 1 litre engine...if the custom pipework is anything greater than 1 3/4 inch bore, then your N/A torque will drop off (due to reduced back pressure)...however fitting a greater bore pipe will allow greater torque gains if you are boosing (with either super charger turbocharger or Nos etc..)

Does anyone have an oppinion on these comments?



ALSO,

There has been many discussions on the differences between the MA10 and MA12's.....but what ar the main differenced between the MA09 and the others......in particular the engine bits I am interested in for example pistons, block head gasket, head, mantfolds, clutch, gearbox driveshafts....(not the super and turbo charging bits)


Cheers All

 

[Arnold]

Thread split from other one. Please dont bring back oldies!

 

[Alienfish360]

in all cases a change of exhaust is there to do 1 thing, speed up the process of removing exhaust gasses from engine.

However, if the bore is too big, this gives the exhaust gas more room to expand and therefore cool. The cooler exhaust gas is heavier and therefore puts more demand on the engine to move it, resulting in the opposite of your task, you're actually slowing the flow down.

However, there's not much point going bigger than your exhaust ports in your primaries.

 

[Ed]

in all cases a change of exhaust is there to do 1 thing, speed up the process of removing exhaust gasses from engine.

Indirectly yes. but more to the point the 1 thing should be to allow an easier more efficient path to remove the gasses, which is not quite the same as to speed them up.

However, if the bore is too big, this gives the exhaust gas more room to expand and therefore cool. The cooler exhaust gas is heavier and therefore puts more demand on the engine to move it, resulting in the opposite of your task, you're actually slowing the flow down.

This is totally backwards. Where did you hear this? I heard almost the exact same recently on another forum. The limiting factor in the amount of power an exhaust system can produce is its flow resistance, or amount of back pressure it produces. Anything you do to reduce the flow resistance at a point the engine is making max power will help it to produce more power. (however often this form of tuning can cause side effects elsewhere, and result in a loss of torque or engine efficiency)

Cooler gasses means they take up less space and you can often have a smaller diameter pipe at the rear end of an exhaust system because of this fact, with no real loss in top end power and sometimes an increase in midrange power and economy.

 

[Krian]

Hey Ed, just out of curiosity, what kind of side effects are you likely to see?

I've heard a lot about engines needing back pressure in the exhaust to operate at the best effiency, but havent been able to find out too many details as to exactly why ya need it Pointers to websites or good books on the subject would also be greatly appreciated

 

[AMY]

Original thread - http://www.micra.org.uk/showthread.php?t=2890



...however fitting a greater bore pipe will allow greater torque gains if you are boosing (with either super charger turbocharger or Nos etc..)

Does anyone have an oppinion on these comments?






Cheers All

It's only really turbo cars that require large exhausts to free up power Super charged and nitrous exhausts should be tuned in a similar way to N/A

 

[Turtle]

This is totally backwards. Where did you hear this? I heard almost the exact same recently on another forum.

This is what forums are for slightly dodgy second hand information and social internet anarchy.

I'm looking forward to going to uni and finding out for myself

 

[Ed]

Hey Ed, just out of curiosity, what kind of side effects are you likely to see?

I've heard a lot about engines needing back pressure in the exhaust to operate at the best effiency, but havent been able to find out too many details as to exactly why ya need it Pointers to websites or good books on the subject would also be greatly appreciated

The reasons why you can't find anything (good) to help you is simply because back pressure isn't what you want. Its an over used and over simplified and misunderstood term.

Exhaust tuning is all about extracting used gasses and helping get in new gasses with as little fuss as possible. The pulses that leave the engine from the exhaust are used to help the ones that follow and almost drag the following gasses out of the engine, the trick is using the right diameter pipes and lengths to most effectively use the exhaust pressure waves in a constructive fashion.

The important thing to remember is the exhaust cannot be considered as an individual part, everything from the way the cams are ground the inlet design and the RPM range in which the exhaust is intended to be used all has a massive influence on the design.
Again this is why system design are so sketchy and info is so hard to find. How can anyone be precise when so much about an application may be unknown.
What you in fact want to avoid at all times is a situation where you create back pressure. Any back pressure at the point of the valves when they open can only hurt the engines ability to remove burnt gasses. So the basic design of an exhaust manifold is to separate the cycles to prevent as far as possible thus reducing one cylinder pressurising another one when its valve opens (K10s suffer so badly in this respect with their combined near on square manifolds).
There are various ways to do this 4-1 or 4-2-1 being the most common examples. The 4-1 gives the most top end power over a narrower RPM range the 4-2-1 (which is almost always the ones used on a Micra) offers a broader range of power but a top end loss of upto 5-7%.
Exhaust gasses leave the engine at about 90 meters per second. However the pressure wave is nearer the speed of sound and can be in excess of 500 meters per second. The black art of exhaust tuning is using the pressure waves to help removing the gasses that follow them. This is done by designing the negative pressure behind the pressure wave to coincide with the valve over lap period. This is where lengths of pipe come into play.

 

[Krian]

Ah, so as I understand it the initial release of exhause gases from one of the cylinders creates a wave front, helping to push out the gases from the cylinder that previously released its exhaust gases helping speed it along and out of the car?

I take it the fairly narrow bore of the exhaust helps create this, hence going over a certain bore reduces these pressure waves having a negative effect in total on how quickly gases leave the car, and as such affecting performance? What about things light the mid level silencer, does that then cause reflection causing a negative pressure wave to bounce back to the cylinder and help pull along exhause gases? Wouldnt a straight through stop this?

Do you know where I might be able to find some more info on that Ed? Anything that specifically covers the MA10 would be nice But i'll settle for general tech docs Possibly uni text books that i might be able to pick up, etc?

Oh, and one more quick question, any idea on the exhaust output of an average ma10? Mebe litres per second at 1000rpm and 3000rpm?

Thanks!

 

[SammoHung]

Oh, and one more quick question, any idea on the exhaust output of an average ma10? Mebe litres per second at 1000rpm and 3000rpm?

Thanks!

For MA10 988cc will be pumped through after 2 revolutions so for 1 revolution this will be 494cc (0.494 litres)

so...1000 revolutions will pump 494 litres (494 litres per minute for 1000 rpm)
<or 8.2 "litres per second" is eisier for me to picture in my head>

and 3000 revolutions will pump 1482 litres (1482 litres per minute for 3000 rpm)
<or 24.7 "litres per second" is eisier for me to picture in my head>

 

[Turtle]

For MA10 988cc will be pumped through after 2 revolutions so for 1 revolution this will be 494cc (0.494 litres)

so...1000 revolutions will pump 494 litres (494 litres per minute for 1000 rpm)
<or 8.2 "litres per second" is eisier for me to picture in my head>

and 3000 revolutions will pump 1482 litres (1482 litres per minute for 3000 rpm)
<or 24.7 "litres per second" is eisier for me to picture in my head>

Sammo, :unclesam: you win the prize for the most entertaining posts on the MSC. Seriously dude, they are a pleasure to read. First class, thank you.

 

[SammoHung]

HAHA...cheers LOLz

You can thank the tennants super for this type behaviour from me most nights!!!! LOL

 

[Krian]

Hey Sammo, explained like that, it seems pretty logical Cheers!

 

[Ed]

As usual its not quite that simple, since after the combusion the energy produced and heat etc, there will be a much larger flow of gasses coming out than was going in.

 

[Krian]

Final question, anyone got any idea of the temperature of your exhaust gases? Something slightly more useful than 'hot' would be good

 

[paul_k10_Lx]

The reasons why you can't find anything (good) to help you is simply because back pressure isn't what you want. Its an over used and over simplified and misunderstood term.

Exhaust tuning is all about extracting used gasses and helping get in new gasses with as little fuss as possible. The pulses that leave the engine from the exhaust are used to help the ones that follow and almost drag the following gasses out of the engine, the trick is using the right diameter pipes and lengths to most effectively use the exhaust pressure waves in a constructive fashion.

The important thing to remember is the exhaust cannot be considered as an individual part, everything from the way the cams are ground the inlet design and the RPM range in which the exhaust is intended to be used all has a massive influence on the design.
Again this is why system design are so sketchy and info is so hard to find. How can anyone be precise when so much about an application may be unknown.
What you in fact want to avoid at all times is a situation where you create back pressure. Any back pressure at the point of the valves when they open can only hurt the engines ability to remove burnt gasses. So the basic design of an exhaust manifold is to separate the cycles to prevent as far as possible thus reducing one cylinder pressurising another one when its valve opens (K10s suffer so badly in this respect with their combined near on square manifolds).
There are various ways to do this 4-1 or 4-2-1 being the most common examples. The 4-1 gives the most top end power over a narrower RPM range the 4-2-1 (which is almost always the ones used on a Micra) offers a broader range of power but a top end loss of upto 5-7%.
Exhaust gasses leave the engine at about 90 meters per second. However the pressure wave is nearer the speed of sound and can be in excess of 500 meters per second. The black art of exhaust tuning is using the pressure waves to help removing the gasses that follow them. This is done by designing the negative pressure behind the pressure wave to coincide with the valve over lap period. This is where lengths of pipe come into play.

is this why now ive fitted the 4 - 1 it pulls harder from about 3 where it used to be about 2.5krpm???

 

[SammoHung]

As usual its not quite that simple, since after the combusion the energy produced and heat etc, there will be a much larger flow of gasses coming out than was going in.

good call!

Obvious really once it has been pointed out, but I honestly hadn't considered this HAHA

Ignoring any volume changes from fueling I guess that the most significant factor would be temperature.

Also ignore gasses cooling along the length of the exhaust pipe (contracting)

Also assume gasses can expand freely (no pressure differential) then the next approximation could be:

(say 15degrees C intake chage) roughly 288K with no combustion pumping compared with 1188K heated exhaust is roughly a multiplier of 3.

new (HOT GAS) approximates

1000rpm 1482 litres per minute (24.7 ls-1)
3000rpm 4446 litres per minute (74.1 ls-1)

In reallity I think from assumptions that the real figures wile lie between the minimum values from the previous post and these maximum values but I guess that they will be closer to the max values....

Anyone know the temperature of the TIP of the exhaust outlet when hot? may be its only 300 Deg C?...anyone got any solder (joke)

These figures should be taken with a pinch of salt but will give an indication of the order of magnitude