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07 fxt
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396 Posts
Discussion Starter #1 (Edited)
will a tune delete rear o2 sensor// road tune or dyno

I have had a cold air intake on my car for 9 months with no problems. no its making my p2097 rear 02 too rich code come up. so i put a new mass air flow sensor in and added the walbro while i was replacing the fuel filter. it went off for a couple days then came back so i switched my intake to a spt style. and it went off for a couple days and is now back.. im going to stage 3 soon should i just do it now and the tuner will delete the rear o2 usage???

second question.

this is the girls car. she likes her car fast but not looking for quarter mile times here. shes more of a midrange puller and 5th gear stabber on the freeway. thats why i chose the turbo i did.

is the dyno tune gonna be safer so to speak for the car than a road tune. im not looking to gain maximum hp out of my setup but the want the car to be reliable and safe

and thanks roo for answering that first question
 

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2005 Base 2.5x foz
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896 Posts
Yes, you can simply delete the rear sensor input when you tune.
 

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07 fxt
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396 Posts
Discussion Starter #3
second question.

this is the girls car. she likes her car fast but not looking for quarter mile times here. shes more of a midrange puller and 5th gear stabber on the freeway. thats why i chose the turbo i did. she never drives past 4.5-5k rpm

is the dyno tune gonna be safer so to speak for the car than a road tune. im not looking to gain maximum hp out of my setup but the want the car to be reliable and safe

and thanks roo for answering that first question

mods are
07 fxt 5sp
perrin dw downpipe catless ported & coated
3" catback
short ram
silicone turbo inlet
walbro pump
witchhunter 750s
08 sti tmic
evoIII big 16g ported & coated
gfb 50/50 bpv
 

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07 fxt
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396 Posts
Discussion Starter #4
witchhunter only list 820/870 cc injectors for top feeds on their site. will i need a larger maf for those to tune properly
 

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2009 Outback XT-B 5MT
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10,255 Posts
820s are fine on the stock MAF/housing.

A dyno tune isn't enough on it's own, but is absolutely required for a completely safe setup. You can see loadings you can't achieve on the street, which means you can tune for a time when you'll have 500 pounds of gear in the car. Just can't do that on the street.
 

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2004 Forester XT
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320 Posts
820s are fine on the stock MAF/housing.

A dyno tune isn't enough on it's own, but is absolutely required for a completely safe setup. You can see loadings you can't achieve on the street, which means you can tune for a time when you'll have 500 pounds of gear in the car. Just can't do that on the street.
Any competent tuner can take care of that during a road tune. It's just a matter of leaving enough knock headroom.

The only time dynos are ABSOLUTELY necessary is for stupid fast cars that would just be unsafe to tune on the street.
 

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07 fxt
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Discussion Starter #7
nice ill just get the 820s then.
or something similiar. they are just down the street from me.
if i have the extra money ill spring for a dyno tune i know it will prob give me more power but im not concerned with that. its a grocery getter.

i just want my girlfriend to feel safe and not have any problems with the car.
 

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2009 Outback XT-B 5MT
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Any competent tuner can take care of that during a road tune. It's just a matter of leaving enough knock headroom.

The only time dynos are ABSOLUTELY necessary is for stupid fast cars that would just be unsafe to tune on the street.
No.

Any car is fast enough to be unsafe to tune on the street. Gear ratios have nothing to do with power. 6000 RPM in 4th gear is just as fast in a 250whp car, as it is in a 650whp car.

"Leaving enough knock headroom" is what you learn in the "my first tune" childrens book. It's incomplete, ignorant, and a half-assed way to tune. Maybe it's just me, but I care more about my car than that.

A tune can only properly be done by first hitting the dyno, and then doing clean-up on the street. You can argue with me about this all you want, but you'll be wrong.
 

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2004 Forester XT
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320 Posts
No.

Any car is fast enough to be unsafe to tune on the street. Gear ratios have nothing to do with power. 6000 RPM in 4th gear is just as fast in a 250whp car, as it is in a 650whp car.

"Leaving enough knock headroom" is what you learn in the "my first tune" childrens book. It's incomplete, ignorant, and a half-assed way to tune. Maybe it's just me, but I care more about my car than that.

A tune can only properly be done by first hitting the dyno, and then doing clean-up on the street. You can argue with me about this all you want, but you'll be wrong.
Do you tune? If so enlighten me a little.
 

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2009 Outback XT-B 5MT
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Do you tune? If so enlighten me a little.
Pretty sure I already did...

You can load a car on a dyno far more than you can on the street. Actually tuning for load sites > "leaving headroom". This is a functional thing. A road-only tune wont ever be as complete as a dyno tune can be. At the end of the day, you are only guessing for load sites you can't reach.

You don't have to double speed limits just to tune high RPM. 6500 RPM in 4th gear is FAR too fast to be considered safe on the street. Plus, on a dyno (and a Dynapak in particular) you don't have to worry about losing control, a tire blow out at speed, brake failure, trans failure, engine failure, a deer/moose/child jumping out of the woods. You don't have to worry about losing your license either. You also can devote all your time to watching logs and monitoring what is going on.

You can't tune in a single pull, and the more street pulls you do the greater the risk you take. Imagine wrecking while doing a redline 4th gear pull. I'm sure your insurance company would LOVE to hear it. ESPECIALLY if you weren't the one driving.

Road tuning only is unsafe in any car. Your point about being "stupid fast cars that would just be unsafe to tune on the street" applies to any amount of power.

The ONLY right way: Tune it on the dyno, clean things up on the street.

You can road tune all you want, but the only way to optimize is to see the above.
 

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Pretty sure I already did...

You can load a car on a dyno far more than you can on the street. Actually tuning for load sites > "leaving headroom". This is a functional thing. A road-only tune wont ever be as complete as a dyno tune can be. At the end of the day, you are only guessing for load sites you can't reach.

You don't have to double speed limits just to tune high RPM. 6500 RPM in 4th gear is FAR too fast to be considered safe on the street. Plus, on a dyno (and a Dynapak in particular) you don't have to worry about losing control, a tire blow out at speed, brake failure, trans failure, engine failure, a deer/moose/child jumping out of the woods. You don't have to worry about losing your license either. You also can devote all your time to watching logs and monitoring what is going on.

You can't tune in a single pull, and the more street pulls you do the greater the risk you take. Imagine wrecking while doing a redline 4th gear pull. I'm sure your insurance company would LOVE to hear it. ESPECIALLY if you weren't the one driving.

Road tuning only is unsafe in any car. Your point about being "stupid fast cars that would just be unsafe to tune on the street" applies to any amount of power.

The ONLY right way: Tune it on the dyno, clean things up on the street.

You can road tune all you want, but the only way to optimize is to see the above.


"Pretty sure I already did," "You can argue with me all you want, but you'll be wrong."

Wow.... not worth my time.
 

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2004 Subaru FXT MT
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Pretty sure I already did...

You can load a car on a dyno far more than you can on the street. Actually tuning for load sites > "leaving headroom". This is a functional thing. A road-only tune wont ever be as complete as a dyno tune can be. At the end of the day, you are only guessing for load sites you can't reach.

You don't have to double speed limits just to tune high RPM. 6500 RPM in 4th gear is FAR too fast to be considered safe on the street. Plus, on a dyno (and a Dynapak in particular) you don't have to worry about losing control, a tire blow out at speed, brake failure, trans failure, engine failure, a deer/moose/child jumping out of the woods. You don't have to worry about losing your license either. You also can devote all your time to watching logs and monitoring what is going on.

You can't tune in a single pull, and the more street pulls you do the greater the risk you take. Imagine wrecking while doing a redline 4th gear pull. I'm sure your insurance company would LOVE to hear it. ESPECIALLY if you weren't the one driving.

Road tuning only is unsafe in any car. Your point about being "stupid fast cars that would just be unsafe to tune on the street" applies to any amount of power.

The ONLY right way: Tune it on the dyno, clean things up on the street.

You can road tune all you want, but the only way to optimize is to see the above.
You can alway throw 500# of sand in the backseat and trunk...You can always do pulls uphill too.

A dyno never properly simulates road loads. But you knew that.

Also, there is a reason they have test and tune nights at the strip.

In the end, we've had these arguements. Mark, Phil sees it one way. You and I see it another. We won't ever agree, and thats the way it is.
 

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07 fxt
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Discussion Starter #14 (Edited)
ok so gordon at witch hunter has a set of top feeds that flow between 856-864. can i use those with the stock maf setup

wait a minute. i just started looking up big maf systems. i thought they replace the maf sensor with a larger one. not just a tube thats bigger diam. if thats the case i can go ahead and get one i have a brand new stock oem maf sensor and thought that going big maf i was going to have to buy a new one. i like the perrin unit.
 

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2009 Outback XT-B 5MT
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Not worth it. The stock MAF is good enough for far more power than you'll consider making. You'd be wasting money on a bigmaf. That said, you can definitely use those 850's with the stock intake. Unless you plan on making more than 360whp, the stock intake or a stock-sized intake is perfectly fine.

Scott, you COULD do that... and still have all of the issues associated with road tuning. It's unnecessarily dangerous. But you knew that too. I'm not comfortable doing 6000RPM 4th gear pulls on a public road, maybe that's just me.

Do you think Porsche tunes their cars solely by "making overhead", or blasting down the Bahn for 4th gear pull after 4th gear pull? Subaru on the Wangan? Ferrari through the streets of Maranello? You think they legalize cars for US import by blasting them down the street to see "road loads" for emissions testing?

No. They don't.

All that matters is that you see proper load sites, and you can vary the load on the dyno to do so. I know you can, because I've actually done it while emissions testing a Porsche for US Legalization.

Tune on the dyno, clean things up on the street. That's the proper, safe way to do the job.
 

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2004 Subaru FXT MT
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Not worth it. The stock MAF is good enough for far more power than you'll consider making. You'd be wasting money on a bigmaf. That said, you can definitely use those 850's with the stock intake. Unless you plan on making more than 360whp, the stock intake or a stock-sized intake is perfectly fine.

Scott, you COULD do that... and still have all of the issues associated with road tuning. It's unnecessarily dangerous. But you knew that too. I'm not comfortable doing 6000RPM 4th gear pulls on a public road, maybe that's just me.

Do you think Porsche tunes their cars solely by "making overhead", or blasting down the Bahn for 4th gear pull after 4th gear pull? Subaru on the Wangan? Ferrari through the streets of Maranello? You think they legalize cars for US import by blasting them down the street to see "road loads" for emissions testing?

No. They don't.

All that matters is that you see proper load sites, and you can vary the load on the dyno to do so. I know you can, because I've actually done it while emissions testing a Porsche for US Legalization.

Tune on the dyno, clean things up on the street. That's the proper, safe way to do the job.
You're points are valid.

Be careful comparing tuning and testing though. Not the same. With emissions testing, you need a standard measurement system that is unchanging. Frankly, it doesn't have to have a direct correlation to the real world. It just has to be standard.

Much of OEM ECU tuning doesn't take place on a dyno either. A lot of their calibration work is done on test courses and tracks. Keep that in mind as well.

Also, just for clarity, I do road tune. But you do have to very carefully pick your spots. I only tune in two places. One is at the track. Obviously closed circuit. The second is a spot that is wideopen corn field, where there isn't a house or forest within 3/4's of a mile of the road I tune on. I don't have to worry about kids or anything else running out in front of me.

I will absolutely agree that if you don't have a place like that to road tune, it is very dangerous.
 

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2009 Outback XT-B 5MT
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My point about emissions was nothing more than the fact that dynos CAN and DO mimic loading you'll see on the road. A load site seen on a dyno is no different than a load site seen on the road. On the FED emissions legalization tests, you'd be surprised how accurately they replicate road standards. It's not a test where you cruise at 40mph. It's an extremely rigorous set of tests. The one I participated in was a 30 minute drive cycle replicating mountain roads and highway merge procedures. Varying throttle and brake situations, variable dyno load to simulate grade changes, all kinds of cool stuff. It also requires intense concentration by the test driver. Consistency is important, and test facilities are evaluated and calibrated monthly. I have a really funny story about the SMART and passing that test, but that's another topic.

I would argue that OEM ECU tuning isn't done on a dyno. I've seen a small share of automotive development facilities, and post-development testing is done on a track (though, obviously, extensive testing is required to be done on a dyno, for logistic reasons. Can't pay a driver to drive 24 hours a day for 6 weeks straight.) Test tracks are used to solidify suspension adjustments and make minor tweaks to tuning for drivability. The majority of initial and development tuning is done in environmental chambers on a dyno. That's been my exposure to OEM tuning, at least. You can't sell a car to someone in Colorado that has only been tuned on a test track in Arizona.

I still think the corn-field route is dangerous. That removes only a few of a long list of possible haphazards. A dyno allows you to safely do what is unsafe to do on the street.

Not to mention the legality of it. Imagine explaining to an officer why you happened to be tripling the speed limit!

I understand the value of road tuning. It's an important tool to put polish to a dyno tune and set up the tip-in-throttle and all that stuff. But to say that road tuning completely eliminates the need for dyno tuning is ridiculous.
 
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