As soon as the tax cheque gets back I am going to do the suspension and also the exhaust - was thinking extractors at the same time. Seems most people here do pacemakers but Liverpool Exhaust where I was thinking of going specialises in Hurricane.. anyone got these and what do you think? What do you think about the extractors and exhaust at the same time? Any other suggestions about places to go or waht I should do? What kind of power increase can I expect from these changes and willthis then chew petrol like there is no tomorrow?

u will get better fuel, unless u put yur foot down more then u will use more petrol

got rpw extractors (made by liverpool anyway) and 2.5" cat back later on, on both occations the difference was quite noticable (i thought it was well worth it), particularly above 3k rpm once all done and yeah ur fuel economy should get better as u'll be making more torque at less revs (mine dropped but about 1L/100ks almost immediately)

depends on ur driving style, if u don't tend to rev much above 4k rpm and don't have to have that top end rush i'd go for just getting the extrators alone..... i did this and some days i wish i could go back as it was perfectly quiet and still made decent mid-range gains, u can always do the rest of the exhaust if it's not enough..... expect decently more noise if u get the whole cat back system tho.......

u will get better fuel, unless u put yur foot down more then u will use more petrol
ahh.. you reckon?

On all the cars i have added extractors and exhausts, my fuel economy has become worse.

Power + greater economy dont go hand in hand. :)

Adding a simple 2nd CAI will make you use more fuel.

From what i've heard from people with extractors is that your fuel economy is worse if you have an aggresive driving style, but remains pretty much unchanged if you're not gunning it all the time, and if you drive alot of freeway/highway km's it will improve (sits on a lower RPM).

(sits on a lower RPM).

it won't sit on a lower RPM. To do 110km/h you still need to be doing X rpm no matter what you've done to the engine, unless you alter your gearing.

The enhanced fuel economy, if any, you get from exhaust and intake changes must come from higher volumetric efficiency, and more combustable air per cycle.

From what i've heard from people with extractors is that your fuel economy is worse if you have an aggresive driving style, but remains pretty much unchanged if you're not gunning it all the time, and if you drive alot of freeway/highway km's it will improve (sits on a lower RPM).

rofl....

rofl....

My foot has gotten heavier since the exhaust upgrade. $$$

it won't sit on a lower RPM. To do 110km/h you still need to be doing X rpm no matter what you've done to the engine, unless you alter your gearing.

The enhanced fuel economy, if any, you get from exhaust and intake changes must come from higher volumetric efficiency, and more combustable air per cycle.
In my TR, my car would sit on about 2400 rpm doing 100km/h. When i put an exhaust and CAI onto it dropped down to 2000-2100 and i had improved highway economy. I dont know about all the mechanics, but that's what happened.

@Bain - that's what i've heard/semi-experienced...

got paccies, and lukey muffler.... idle is at 900rpm... fuel consumption 12's....city driving...

In my TR, my car would sit on about 2400 rpm doing 100km/h. When i put an exhaust and CAI onto it dropped down to 2000-2100 and i had improved highway economy. I dont know about all the mechanics, but that's what happened.


re the above: A question for those with more of a clue than I've got.. could an auto box slip either more or less with altered engine output, or is that just being silly?

re the above: A question for those with more of a clue than I've got.. could an auto box slip either more or less with altered engine output, or is that just being silly?
Idle wont change at all mate. Gear ratios dont change from adding an exhaust or extractors.

The only time the idle or coasting rpm would change is if its been retuned.

Idle wont change at all mate. Gear ratios dont change from adding an exhaust or extractors.

The only time the idle or coasting rpm would change is if its been retuned.

Explain that part to me. What's being retuned to change the coasting RPM?

Isn't it all about the power getting to the wheels?
IE. A few members have increased their maximum speeds by increasing their power, but they haven't changed the gearbox?
So if power increases at the wheels, wouldn't that mean the engine would work less to maintain a certain speed?

Isn't it all about the power getting to the wheels?
IE. A few members have increased their maximum speeds by increasing their power, but they haven't changed the gearbox?
So if power increases at the wheels, wouldn't that mean the engine would work less to maintain a certain speed?

Just increasing your engine output won't improve your top speed unless you:

a) maintain the same engine speed but use taller gearing, or
b) keep the same gearing but allow the engine to spin faster

Booya got to 280km/h because his engine was built to spin to 8000rpm.

re the above: A question for those with more of a clue than I've got.. could an auto box slip either more or less with altered engine output, or is that just being silly?

If X amount of power is required to push the car along the highway at coasting speeds, the engine needs to make that X amount of power, but some will be lost through inefficienies eg restrictive exhaust manifold. If you get extractors which are less restrictive, the engine will make that same amount of power at a lower rpm, so yeah it could be possible.

If X amount of power is required to push the car along the highway at coasting speeds, the engine needs to make that X amount of power, but some will be lost through inefficienies eg restrictive exhaust manifold. If you get extractors which are less restrictive, the engine will make that same amount of power at a lower rpm, so yeah it could be possible.

But the speed at which the car travels is governed by how fast the wheels turn, not how much power the engine puts out. The gear box and diff modify the engine speed in fixed ratios that aren't affected by power output.

Its not a cvt, the gears are a fixed ratio. I would belive for sure that with the added torque from extractors on many occasions it would stay in top gear more often and not shift down.

I thought autos had a fair bit of slip though if they're not locked up?

From my understanding the HP output of your engine is a measure of how many set weights it can lift againts gravity (now measured using a dyno).

So if a car has a higher HP output it does not have to work as hard to overcome the forces of wind resistance and friction on the road, using less fuel.

Top speed would be a different issue, it would depend if your engine just doesn't have enough power to overcome the increasing wind resistance or if the gearing just does not allow you to go faster, usually it is the engine just doesn't have enough power, if you don't believe me get to top speed on a flat then try it on slope, either up or down.

Isn't it all about the power getting to the wheels?
IE. A few members have increased their maximum speeds by increasing their power, but they haven't changed the gearbox?
So if power increases at the wheels, wouldn't that mean the engine would work less to maintain a certain speed?
Maybe. Depends on power delivery and wind resistance.

The only way to increase a car's max speed in top gear is to change it's gearing or change it's amount of power, (actually, it's torque), and how it's delivered. If you change your gearing to be taller then you'll probably need more torque to get you there anyway.

Hope this helps

Here is just a bit of what I have heard about extractors, it may not all be correct but it’s pretty close and makes sense

Properly tuned extractors helps exhaust flow out smoothly making the engine more responsive, more powerful and more efficient
Every time the exhaust gas is forced out by a piston it makes pulse/puff of gas shoot out. Properly tuned extractors will utilise each “puff” from every cylinder and put them into order so u get 1 puff followed closely but another puff and then another and so on
If the engine is revving fast, all the little puffs will be bunched together in a big line moving quickly, the momentum of all these puffs moving down the pipe can start to create a vacuum for the puffs waiting to come out.

This is when you can get a scavenging effect (when the exhaust is sucked out of the cylinder’s) this only happens when the inlet valves and the exhaust valves are open together. (Valve overlap) The scavenge effect causes the new fuel air mixture to be sucked into the cylinder as well. Meaning more power. Because the cylinder has all of the exhaust gas sucked out and if filled with freshly unburnt fuel.
This may or may not happen depending on your engine setup. However if the scavenging effect is to great it will suck un burnt fuel out of the cylinders and into the exhaust pipe as well, meaning bad economy

Just a few more reasons Why extractors may not be economical:


1-

Pipe diameter to large, it the pipe is to large the gas will flow slowly. Therefore it will be unable to build up momentum, meaning every time gas is expelled from a cylinder it will have to push its way out. (Not good) (some extractors are made this way because they are expecting the engine to be revving its guts out, and the pipe diameters are made to cope with a large amount of gas flowing through them, these extractors will make an engine more efficient as higher revs but not at lower revs.)


2-

Pipe diameter 2 small. This will create unnecessary back pressure when the engine is revving hard. The exhaust gas may be moving fast & have a lot of momentum, but the pipe will be restricting flow meaning every time gas is expelled from a cylinder it will have to push its way out. (Not good) (some extractors are also made purposely like this, because it will make more power and efficiently at low revs, but at sacrificing power at higher revs)

3-

Poorly made/designed extractors. If they are made poorly, bad bends that change the volume in a section of pipe the puffs/pulse’s may not come out smoothly, which could result in too puffs entering the main pipe at once or 2 close together or 2 far apart, causing a non smooth flow. Making it harder for the gas to build up momentum.




Properly made/designed extractors should make a car run more efficient. Because the engine doesn’t’ have to do as much work getting the exhaust gasses out.
Eg u have a 124kw engine with stock exhausts.
Lets say that the stock exhaust’s are made in a way that means an additional 12kw are used up in forcing exhaust out from the cylinders. Then we put some extractors (well made/designed ones) on we will reduce the amount of power needed to get the exhaust out of the engine, lets say form 12kw to 5kw, the remaining 7kw is now free 124kw >> 131kw engine.

more power = faster speed

So if my car can do 215kph before it hits the rev limiter, and its a 147kW engine, a 800kW Kenwood truck should be able to 1170kph...lol
No more power DOES NOT equal faster TOP speed! The truck is GEARED differently.

More power means you will be able to get to a certain speed faster, but your top speed will not change unless your gearing changes or you top rev limit increases.

Unmodified... 0-100 in 8 sec top speed at 6000rpm is 215kph.
Modified... 0-100 in 6.5 sec top speed at 6000rpm is 215kph.
There is no change in top speed as the gearing of the engine/gearbox/diff HAS NOT CHANGED and the engine has not been built to rev any faster!

So summary:
More Power = faster ACCELERATION not speed :)

Then i dont know how it's possible that my TR's rpm at 100km/h changed when i had my exhaust/cai on.

Also if you raise the base idle, doesn't that increase the rpm through all gears? How does that work (if correct)?

more acceleration can mean faster speed though.... IF originally your car didnt have enough power to 'pull' that gear. although i doubt any manufacturers cars have this problem...

Also if you raise the base idle, doesn't that increase the rpm through all gears? How does that work (if correct)?
All adjusting base idle does is adjusting how much the throttle opens without using the accelerator to open the throttle. It doesn't have a flow on effect through the rev range.


more acceleration can mean faster speed though.... IF originally your car didnt have enough power to 'pull' that gear. although i doubt any manufacturers cars have this problem...
That's still purely subject to how torque has been affected, if you've change wind resistance or made the car lighter. i.e. the main way you affect this is by how you're getting your air in so cams and forced induction is the main driver here. Just because you fit cams that double the amount of torque from 1000rpm to 4000rpm which increases your acceleration by 25%, doesn't mean you're car will actually be faster. By the nature of cam design etc, chances are it will actually be slower. But yeah, if you've increased torque around the point of peak power or pushed it several hundered rpm higher then yeah, you're car should be able to travel at a higher speed.

I thought Liverpool Exhaust had a poor reputation?

As I said before, give the guys at Surflow exhaust a call, they even have their own dyno. Mainly specialise in LS1s but Im sure they could prob. do a Magna.

I thought Liverpool Exhaust had a poor reputation?
Depends on who you talk to. Some customers are happy, some aren't. Every exhaust shop is the same. It seems to be a industry which has consistantly varying opinions from customers.

Re tommo19 (nice name btw ;))
Yeah that pretty much explains it, but also it would reduce the amount of exhaust gas re-circulation(EGR) due to removing all of the exhaust gasses and possibly some of the air/fuel mix. Efi cars will run in a closed loop cycle when cruising at a fairly constant speed, this is where the oxygen and detonation sensors are the only inputs being used, to lean out the fuel mix as much as possible. If all of the exhaust gasses are being removed then more fresh air will be drawn into the combustion chamber to replace it. More fresh air will require more fuel to be added to the mix to retain the correct fuel mixture.

That said, due to the scavenging effect of the extractors, less pressure is required to remove the exhaust gasses, reducing the amount of fuel being added. Even though the engine rpm at any speed will be the same, the amount of friction/compression losses will be lower, hence less fuel may be needed.

So all in all, I don't think that you should worry about extractors making the engine use more fuel.