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My car feels faster before it warms up. It slowly climbs to 3250rpm and then launches. Typically, an engine performs worse (and wears faster) before it warms up, so I try to go easy on it. Yet, as the tach slowly climbs to 3250, it rockets after that much more forcefully than normal. Either that, or it just seems that way, and the engine is simply making dramatically less power before 3250rpm. Like I said, I don't push the car until it's warmed up, so it's hard to tell.

All I know is that the engine isn't linear at all until it's warmed up, and it certainly feels faster cold. I like peaky engines- they're more fun when rowing gears.

Is this because the air under the hood hasn't warmed up yet? Is that what I could expect from a cold air intake, or is this surge of power created from something else (engine timing for emmissions)? In my mind, it seems a CAI would not cause power spikes, but a boost over the entire rev range- however a less restrictive intake would cause a boost as RPMs rise.

Do CAI's void your factory warranty?
 

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Reading Topic: Better breathing and cold air intakes

The '6 jumped from 220hp and 192ft-lbs to 242hp and 210 lb-fts with a short ram intake and new exhaust headers / Y-pipe (same car, same dyno). Those are huge benefits! Even if those results were exaggerated, it's still significant considering the statistical marketing wars between cars nowadays.

Why not do that from the factory? The cost of design and parts has got to be peanuts for an auto manufacturer!
 

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Reading Topic: Better breathing and cold air intakes

A better flowing exaust reduces back pressure, which increases high-end horsepower but decreases torque.

A turbo increases backpressure since the turbo's turbine creates resistence. Shouldn't this produce more low-end torque? Why then does a turbo engine typically make little torque before it spools up?
 

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Replying to Topic 'Better breathing and cold air intakes'

QUOTE
Originally posted by stretchsje


            The '6 jumped from 220hp and 192ft-lbs to 242hp and 210 lb-fts with a short ram intake and new exhaust headers / Y-pipe (same car, same dyno). Those are huge benefits! Even if those results were exaggerated, it's still significant considering the statistical marketing wars between cars nowadays.

Why not do that from the factory?  The cost of design and parts has got to be peanuts for an auto manufacturer![/b]
Two things, the DP headers do not have the precats that restrict exhaust flow. They are not emissions legal. Also look at the cost. I'm sure engine design teams would love to get the perfect exhaust system past cost accounting, but it rarely happens.

As for the air intake, IIRC When testing emissions the engine must run 50K miles with no service and still pass emissions. Wonder it the aftermarkets could do that.
 

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Reading Topic: Better breathing and cold air intakes

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Two things, the DP headers do not have the precats that restrict exhaust flow. They are not emissions legal.[/b]
Didn't think of that. You're right.

Anyway, the biggest question on my mind is still my first post. Is that surge of power while the engine is cold due to the cold air? Think a CAI will provide similar results?
 

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Reading Topic: Better breathing and cold air intakes

I am a Nissan man myself, but am looking into the 6 and awaiting news on the MPS 6 for NA availability. I am not at all familiar with Mazdas outside the FD3S, but am more impressed with this sedan the more I get to know it. That said, I'll try an answer to your first post- the engine will usually run different for two reasons at start-up. First, is the mode the ECU is in. The ECU will start and run in open loop mode until warm up for safety reasons. Open loop mode allows the ECU to measure and compare all the available sensor information continuously and determine the proper fuel delivery. Closed loop mode allows the ECU to simply run a pre-set map of fuel delivery based on throttle without having to calculate the delivery on the fly like open loop. This allows for greater fuel economy, but typically, open loop produces more power. Second, is the ambient air temp. like you mentioned. Colder air is more dense air, and again, in open loop the O2 sensors will read the additional oxygen and the ECU will adjust fuel instantly for the next combustion cycle. In closed loop the O2 sensors are also used but run through a map with pre-set parameters for fuel-economy and such. Also, open loop mode might have an impact on the VVT system.
Car companies don't usually have power on the top of the list for midsize family sedans. Just enought to run with the competition, but not at the cost of increased NVH and loss of emmissions capabilities. I have not seen, heard, or even know squat about the headers and intake for the 6, but most systems will remove at least one or two cats, as someone mentioned, and greatly increase the NVH levels of the car. Most consumers are not so willing to put up with that. Plus, there's a reliability issue. Cast iron manifolds are heavy but last- stainless is smooth and nice, but blues, will eventually wear despite the excellent heat properties, and comparitively expensive.
Finally, turbos and backpressure.... well, first let me say backpressure is maybe the first most misunderstood concept in engine dynamics. With that said, many people believe as you do that decreasing backpressure decreases torque. This is incorrect, but easy to miss. A long time ago people realised that putting a big exhaust helped power up to a point and affected different aspects of the engine's power delivery. After that point, power was worse and so people assumed backpressure was neccessary. The truth is backpressure ALWAYS hurts performance. The reason exhaust diameter is in question so often isn't to keep backpressure up, but to find the right resonance of the exhaust flow. Too small or large a pipe will affect the resonance and hurt the speed and scavenging affect the exhaust pulses have when exiting the combustion chamber. With a turbo, there are more variables and I have gone on long enough, so just remember bigger is better with F/I. As far as torque goes with turbos and where it peaks, that is primarily the design and efficiency of the turbo in question. A small T25 will not be efficient at 8000 rpm but will spool like a banshee off the line, a big T7 wheel wouldn't do much good on the street, but when it spools up, watch out! If you really want to know more on turbos and matching, I would highly recommend Maximum Boost by Corky Bell.
Hope this all helps.
 

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Reading Topic: Better breathing and cold air intakes

QUOTE
Originally posted by Jester

Open loop mode allows the ECU to measure and compare all the available sensor information continuously and determine the proper fuel delivery. Closed loop mode allows the ECU to simply run a pre-set map of fuel delivery based on throttle without having to calculate the delivery on the fly like open loop.[/b]
I think you have the two terms reversed. Closed loop the ECU uses the O2 sensor. Open loop (WOT) the ECU ignores the O2 sensor.
 

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Replying to Topic 'Better breathing and cold air intakes'

After finding out about the emissions issues involving the DP headers, I'm not pretty reluctant to buy that mod. After having pushed the car to its limits, I'm almost more interested now in smoothing out the power band and opening up the top end, rather than just more brute power.

I've been looking into getting a custom cat back exhaust made, which wouldn't involve screwing with the emissions equipment. The trouble with the V6 is, since its only available hear in the U.S., not many companies are developing performance mods, especially the good foriegn manufacturers. How would a cat-back effect the car without a header or intake? would improve the high end and smooth out the power over the rev range? I'm not planning on going wider than 2.5'' on the pipe. I can get this done for about $800 installed, which isn't bad, seeing as most duel exhausts run in the $700-$1000 range. Any thoughts?
 

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Reading Topic: Better breathing and cold air intakes

Some good info.

http://www.eiccd.cc.ia.us/~dhanan/ep2/NOTES7.TRP.html

Open loop:
Definition: A mode of operation in a computerized engine management system that occurs after a cold start. During open loop, the computer provides a fixed air/fuel ratio that is richer than normal to improve cold derivability until the engine warms up. See also Closed Loop.

Open loop mode produces a richer mixture unlike closed loop which uses all the sensors to adjust air/fuel mixture. The pre-set maps are used as tables to use when reading the values of the various sensors involved in engine control and operation. Thus, as the ECU receives data from the sensors, it compares that data to the tables in order to select a map. In open loop mode the mixture is determined as rich while waiting for the cats to reach operating temperature.
Closed loop is not so simple, there are actually many many calculations going on so as to deliver the proper mixture of air/fuel on the fly.

Tome
 

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Reading Topic: Better breathing and cold air intakes

"A better flowing exaust reduces back pressure, which increases high-end horsepower but decreases torque."

This statement is too general. When adding a larger exhaust, torque can increase as well, just not as much when taking backpressure into consideration. Jester, I agree, with F/I, the bigger the better. I also think backpressure is an over discussed and overrated topic around the circles. One should be worried more about keeping exhaust pulses equal than scaling down diameter to effect HP/torque. Jester's explaination explains why equal length headers are the goal of a good exhaust design.

"A turbo increases backpressure since the turbo's turbine creates resistence. Shouldn't this produce more low-end torque? Why then does a turbo engine typically make little torque before it spools up? "

The restriction shouldn't be "producing" torque. If you create a length of pipe that goes 2.5"-2"-2.5", that's adding a restriction and increasing back pressure. I highly doubt you will see increased torque gains, rather the opposite. If you did, maybe 1-2 ft/lbs increase? Yet the negative effects of the kink would defeat the whole purpose. The efficiency of a turbo way outweighs any restriction in the flow by the turbine, IMHO. The reason you don't get torque until full spool is because the spool doesn't come on in a linear fashion such as a supercharger. Essentially, the turbo is adding nothing before full spool, but then when its up to speed, the boost will build, and watch those torque numbers scream!
 

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Replying to Topic 'Better breathing and cold air intakes'

QUOTE
Originally posted by Brillo
How would a cat-back effect the car without a header or intake? would improve the high end and smooth out the power over the rev range? I'm not planning on going wider than 2.5'' on the pipe. I can get this done for about $800 installed, which isn't bad, seeing as most duel exhausts run in the $700-$1000 range. Any thoughts?[/b]
You'll get better response, which is what you are looking for. It just may not be the same as adding a header and intake.

$800 is ok for crush bent. There are two shops around here that will do crush bends customs starting at $500. My friend paid $850 for his Silverado, but that included dual mufflers and big 4" pipe. Shop around, look for someone reputable. My guess is they are only going to do it once, not R&D work as that would cost too much. See if anyone in your area does Mandrel bends. You'll realize more power that way if you aren't increasing exhaust size. Also watch what type of mufflers they are using. Some have more rasp and drone than others, which might be unacceptable to you for daily driving. I would goto www.contour.org and see what types people are using over there. Could give you a good idea of the brands you would want.
 

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Reading Topic: Better breathing and cold air intakes

It is going to be a mandrel bend exhaust, even if I have to pay more. What mufflers have people used that are quiet? I don't want it to be loud.....anyone have any good experience?
 

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Replying to Topic 'Better breathing and cold air intakes'

I like Simple_man's approach 2.5" mid pipe

Seems to me that most of the restriction would be in the small pipe and resonator before the split to duals.
 

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Reading Topic: Better breathing and cold air intakes

Jester, tha's some good info that you gave us. :thumb up.
You said that for F/I bigger is better. Although, I certainly agree as you can get much more boost from it. My question is wouldn't more be better? Bigger turbos mean more lag so wouldn't it better to have more than one turbo.
 

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Reading Topic: Better breathing and cold air intakes

I was referring to exhaust diameter. For turbo size, bigger is not always better, but niether is more. The fact is, it all depends. I have seen twin turbo set-ups on a SR20 before and they look sweet, but not at all efficient. A single, well designed and properly matched turbo will typically do better. Most twin turbo motors like the RB26 or 2JZ are converted to single turbo for better street-ability and power. But, this all depends on your personal preference for street-ability. Of course with a V6 or V8 twin turbos are more efficient than the plumbing required to equally space both exhaust banks from the turbo, but quad-turbos would not necessarily be better. Again, Maximum Boost by Corky Bell is, in my opinion, the most current and definitive source for turbo information.
And my apologizes on the open vs. closed loop misunderstanding.
 

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Replying to Topic 'Better breathing and cold air intakes'

Was looking at my stock filter box of my M6 V6, it appears the only real air inlet to the filter box is thru a butter-fly type actuated valve on the side of the box. This opening was only about 1in wide by about 3in long. Don't see that it can flow much CFM when the engine decides it needs a big gulp of air. There is a funny elbow sticking up attached to the box that goes to the bottom of the box. Not sure if this is an extra air inlet or not. Also saw the bottom of the filter box had a downward tube that went into some other auxilary box of sorts below the main filter box. My wifes V6 Tribute has this same basic engine and it has a ram air tube of sorts next to the radiator providing good inlet air into the filter box. Seems our M6 is missing this. One would think the engine design weenies don't know the KISS principle. I'm sure a good cold air filter box could have been designed that was much simpler in routing, cost efficient and breathed better than what they have now.
 

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Reading Topic: Reading Topic: Better breathing and cold air intakes

Made the same mistake. Open the air box and put your hand at the bottom back. There is an opening there on the floor from the snorkle at the front. You can't see it, you have to feel for it, it opens to the rear.
 
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