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Help needed- difference in power range? 

 

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Posted: Tue Jun 21, 2005 2:35 pm 
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Hmm youve got me thinking now shuggs lol, its possible after i reset the ecu that the shift patterns were changed also... mabe it only kicks down when the rpm is high? i dunoo coz even when you drive it normally and you dont put your foot down you can really feel the power higher in the rpm than usual.... :?

 

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Posted: Tue Jun 21, 2005 2:40 pm 
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What about a shift kit.

http://www.shiftkits.com.au/ShiftKitsFord.aspx

There are DIY topic's somewhere around Ford Mods.

Shugg
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Posted: Tue Jun 21, 2005 2:41 pm 
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Shugg wrote:
That may be a contributing factor. The engine want's to open up more, but the gearing in the auto could be holding it back. Unless you have any major mods planned, have you considered a chip and custome tune?


Hmm i had no REAL plans for major mods.... well until ive finished paying for her atleast lol :roll: but a manual conversion would be nice, and i would like to have some decent power...

I will see what happens, i might just do a full service and tune on it soon and see how it responds to that? I can work it out but its definately a different drive to what it was when i first got it :)

 

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Posted: Tue Jun 21, 2005 6:12 pm 
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There was a guy who developed and sold an exhaust system valve controlled by backpressure (adjustable) - the idea was to be able to do without any mufflers because this big butterfly valve thing would progressively open according to backpressure and it's adjustment. I think it was on Autospeed that I saw this thing - have wondered about whether it might be worth using it in a 2.5 sport system to recover bottom end.

Another thought is using a Pajero muffler - I believe they have a spring loaded bypass flap inside which is designed to give the benefit of good silencing and backpressure until the system really needs to flow better. Might make a sport system too quiet tho - and I'm not sure if they're 2.5 inch.

 

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Posted: Tue Jun 21, 2005 7:20 pm 
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Shugg wrote:
What about a shift kit.

http://www.shiftkits.com.au/ShiftKitsFord.aspx

There are DIY topic's somewhere around Ford Mods.

Shugg


Yeah i wouldnt mind a shift kit, cheap and relatively easy to do... Only problem is im not much good soldering wires etc... I supose i could always get someone to do it for me :roll:

 

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Posted: Tue Jun 21, 2005 8:47 pm 
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my theory is that u dont have enough back pressure down low thus causing the gases to escape slower,but when up top the bigger pipe allows more gases to escape than the stock pipe.

 

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Posted: Wed Jun 22, 2005 2:11 am 
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So whats causing this 'lack of' back pressure when the rpm range isnt so high? :? Is it possible that extractors might fix this? Hmm ne way extractors will hopefully be getting done later on this year.. :roll:

 

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Posted: Wed Jun 22, 2005 12:23 pm 
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Extractors will worsen the situation - the lack of backpressure at low rpm means that at the same time the incomming mixture is trying to fill the cylinders, the good flowing exhaust system has created a suction at the exhaust - so you're trying to increase the cylinder fill from one side while it's being sucked out ("scavenged") from the other - during the period the valves overlap.

Good exhaust flow becomes beneficial at higher rpm - and because the power equation includes rpm as one of the variables then this is what's needed for best max power - but obviously this great max power figure comes at the cost of low down grunt.

A lot of people completely miss the point that a truly sporty / powerful engine needs to be revving - so if they do up their engine to make good max power but the gearing isn't suitable then they'll end up with at best no improvement in low down performance and possibly even worse.

 

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Posted: Wed Jun 22, 2005 1:14 pm 
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Yeah okay.. i sort of understand that.. So your saying that mabe the best thing for me to do would be something like a manual conversion with an aftermarket ECU?

Either that or an auto shiftkit may improve this.. i dunno. But its not a real big issue i mean i would rather have power at a higher rpm ne way.. Means overtaking and country driving is more fun... :roll: I meant that in a good way. :)

 

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Posted: Wed Jun 22, 2005 4:13 pm 
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try and blow air threw a straw gently ,then do it hard.
now try and blow through a piece of garden hose the same length and effort as the straw ,u will understand then

 

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Posted: Wed Jun 22, 2005 4:24 pm 
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Hmm okay... No i do understand its fine. :)

 

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Posted: Thu Jun 23, 2005 9:32 am 
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hello,

I got a redback 2.5in mandrel bent system with 2 mufflers last week and it improved low down torque dramatically. I am running the stock 2.25in cat and exhaust manifold. My power rev range actually dropped, pulls alot harder from the lights. Top end is a litttle better but not as noticable as down low where i got all my power gains.


I'd say the fact I have the original cat and exhaust manifold I am still getting good back pressure at low rpm? I will never put extractors on my car unless i have a mild cam in it, you loose to much acceleration off the line.

Cheers Luke.
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Posted: Thu Jun 23, 2005 12:22 pm 
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EL_Fairmont wrote:
hello,

I got a redback 2.5in mandrel bent system with 2 mufflers last week and it improved low down torque dramatically. I am running the stock 2.25in cat and exhaust manifold. My power rev range actually dropped, pulls alot harder from the lights. Top end is a litttle better but not as noticable as down low where i got all my power gains.


I'd say the fact I have the original cat and exhaust manifold I am still getting good back pressure at low rpm? I will never put extractors on my car unless i have a mild cam in it, you loose to much acceleration off the line.

Cheers Luke.


Ah-HA!! - thanks for posting! - you've confirmed something I've suspected for ages - ie. that a great compromise is to fit 2.5 behind the cat but not worry about the manifold or the cat itself - keeps cost right down but yields really good result for everyday driving. Perhaps the std 2.25 full system gives a tad TOO much backpressure, so freeing it up but leaving the normal manifold and cat = just the right amount.

 

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Posted: Thu Jun 23, 2005 12:41 pm 
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My theory is that the exhaust has moved the peak power further up in the rev range. The exhaust now suits the engine better at high revs... comprimising some of the low end...

Anyways, heres an interesting read... doesnt really answer your question but I was just in the mood for posting a link, lol. Certainly clears a few things up about back pressure :)


http://www.nsxprime.com/FAQ/Miscellaneo ... theory.htm

 

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Posted: Thu Jun 23, 2005 12:51 pm 
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4.9 EF Futura wrote:
My theory is that the exhaust has moved the peak power further up in the rev range. The exhaust now suits the engine better at high revs... comprimising some of the low end...

Anyways, heres an interesting read... doesnt really answer your question but I was just in the mood for posting a link, lol. Certainly clears a few things up about back pressure :)


http://www.nsxprime.com/FAQ/Miscellaneo ... theory.htm


LOL sorry i just had my immature moment their reading the link... Types of Muff... yeah sorry made me laugh :roll:

But yeah i would also tend to agree with what Martin is saying, but i mean until i get this tune up done (which needs to be one) it could be just a flat spot .. New leads and plugs would possibly fix that :?

Also the ONLY way to know for sure is to get my car on the dyno again as well, as that will determin whether or not the power has increased further on in the rpm range. :)

 

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