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If you like your mileage you can keep it. by RayOtton
Started on: 12-19-2013 10:37 AM
Replies: 22 (663 views)
Last post by: dobey on 12-22-2013 11:21 PM
RayOtton
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Report this Post12-19-2013 10:37 AM Click Here to See the Profile for RayOttonClick Here to Email RayOttonSend a Private Message to RayOttonEdit/Delete MessageReply w/QuoteDirect Link to This Post
See what I did there?

This should be under technical discussions but we're encouraged not to post anything remotely political over there so since I couldn't NOT use this lead in, I'm posting it here. Sorry in advance for those who will be completely, utterly offended.
Anyhow, I'm not sure how much of an issue this is but I'd like some input.

I've done some mods to my '88 Formula V6/auto:

1 - Cat delete
2 - Underdrive pulley set
3 - 195 degree fan switch
4 - 80 pound weight reduction
5 - 11 degrees initial timing advance using 89 octane NON ethanol fuel. ( no pinging experienced )
6 - Dawg style intake and new EGR tube ( the original was completely broken off at the manifold end )
7 - Ported exhaust manifolds

Up until the last two mods I was consistently between 24.5 and 26 MPG. I run right around 80% highway miles all the time and unless "provoked" I have a light foot.

With the last two mods, which were done at the same time, I'm running 23.5 to 24.5 MPG. Not a big change but definitely lower. I THOUGHT I'd see a little improvement.

As for performance, I have a measured distance that I use to compare my various vehicles. It's somewhere around 1/8 mile on a VERY safe stretch of country road. I have seen a consistent standing start 4 MPH increase with the Fiero since adding the intake/exhaust mods so I know that they are actually improvements. Seat of the pants, the car is more responsive, especially in the mid RPM range.

Did I miss something?
Maybe an electronic "reset"?
EGR wasn't working and now it is?
Don't worry about it?
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dobey
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Report this Post12-19-2013 10:56 AM Click Here to See the Profile for dobeySend a Private Message to dobeyEdit/Delete MessageReply w/QuoteDirect Link to This Post
I'd say, install a new cat where it should be. You'll probably get better MPG with it, than without.
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lateFormula
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Report this Post12-19-2013 11:48 AM Click Here to See the Profile for lateFormulaSend a Private Message to lateFormulaEdit/Delete MessageReply w/QuoteDirect Link to This Post
1) As Dobey said, put a cat back on it. New Magnaflow converters can be had from Summit for <$70, and installing a new one will not affect the performance of the car.
2) What about the obvious, like the inflation of your tires?
3) You've got an auto, is your torque converter locking up at cruise speed? Your loss in fuel economy looks to be on par with a non functioning torque converter lock up solenoid.
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Raydar
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Report this Post12-19-2013 01:36 PM Click Here to See the Profile for RaydarClick Here to Email RaydarSend a Private Message to RaydarEdit/Delete MessageReply w/QuoteDirect Link to This Post
I disagree that a cat will help the fuel mileage. It may not hurt - at least not much - but I don't see how it can help.
Having said that... When you're on "outings", a cat will help to prevent your car from making the eyes of the people behind you burn.
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2.5
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Report this Post12-19-2013 01:50 PM Click Here to See the Profile for 2.5Send a Private Message to 2.5Edit/Delete MessageReply w/QuoteDirect Link to This Post
What did you do to lose the 80 lbs, besides the cat?
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dobey
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Report this Post12-19-2013 01:53 PM Click Here to See the Profile for dobeySend a Private Message to dobeyEdit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
Originally posted by Raydar:

I disagree that a cat will help the fuel mileage. It may not hurt - at least not much - but I don't see how it can help.
Having said that... When you're on "outings", a cat will help to prevent your car from making the eyes of the people behind you burn.


The other mods can reduce back pressure in the exhaust system, which would could cause a slight decrease in low end torque. The lack of a cat, will also affect O2 sensor readings, and does cause the exhaust to smell rich. Also, removing the cat is illegal. A new, properly functioning cat will have almost 0 effect on performance, will get rid of any rich smell from the exhaust as a result of not having one, and will restore back pressure in the exhaust. The restored back pressure will give a slight bump to the torque output, and will likely result in a ~1 MPG increase at cruising speed.

And if a cop pulls you over and looks under your car, because your exhaust is loud/smelly, they won't have opportunity to give you several tickets and possibly impound your car, because you ripped the cat out.
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Report this Post12-19-2013 02:00 PM Click Here to See the Profile for 2.5Send a Private Message to 2.5Edit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
Originally posted by dobey:
.. and will restore back pressure in the exhaust. The restored back pressure will give a slight bump to the torque output, and will likely result in a ~1 MPG increase at cruising speed.



How does one know when they have the right amount of back pressure, is it measurable?
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RayOtton
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Report this Post12-19-2013 03:19 PM Click Here to See the Profile for RayOttonClick Here to Email RayOttonSend a Private Message to RayOttonEdit/Delete MessageReply w/QuoteDirect Link to This Post
I read a lot about the odor from the exhaust without a cat but honestly, there's no notable difference and trust me, wifey would notice. ( I can't believe her sense of smell sometimes)

Could that be an indicator of something wrong?

Not the wife, the car.
Motorcycles and cars and trucks older than 25 years old are exempt from smog and emissions testing in Virginia. Of course that doesn't mean the cat can be removed but really, I've been pulled over a number of times in 44 years of driving and I've never had an officer crouch down to see if all the mechanical bits were in place. First off, out here in the boonies many of the officers couldn't crouch and secondly, seems like they wouldn't want to mess up their uniform pants.

I haven't noticed a reduction in low end torque either, in fact, I ALMOST got the tires to chirp on one of my runs. That could be due to the weight reduction.

As for the weight reduction, I removed the rear wing, the cat and heat shield, replaced the battery with an Optima, removed the spare tire and lost 10 pounds of ugly fat. Me, not wifey, she's perfect just the way she is and in the same room as I write this.

Really, I quite happy with the modifications, I just thought the mileage would go up slightly.

Any other ideas?
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dobey
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Report this Post12-19-2013 03:57 PM Click Here to See the Profile for dobeySend a Private Message to dobeyEdit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
Originally posted by RayOtton:

I read a lot about the odor from the exhaust without a cat but honestly, there's no notable difference and trust me, wifey would notice. ( I can't believe her sense of smell sometimes)

Could that be an indicator of something wrong?

Not the wife, the car.
Motorcycles and cars and trucks older than 25 years old are exempt from smog and emissions testing in Virginia. Of course that doesn't mean the cat can be removed but really, I've been pulled over a number of times in 44 years of driving and I've never had an officer crouch down to see if all the mechanical bits were in place. First off, out here in the boonies many of the officers couldn't crouch and secondly, seems like they wouldn't want to mess up their uniform pants.

I haven't noticed a reduction in low end torque either, in fact, I ALMOST got the tires to chirp on one of my runs. That could be due to the weight reduction.

As for the weight reduction, I removed the rear wing, the cat and heat shield, replaced the battery with an Optima, removed the spare tire and lost 10 pounds of ugly fat. Me, not wifey, she's perfect just the way she is and in the same room as I write this.

Really, I quite happy with the modifications, I just thought the mileage would go up slightly.

Any other ideas?


Well, a 1 MPG difference on highway is statistically insignificant, as well. Unless you've gotten that difference consistently for 3 months, I wouldn't put much stock in it. The amount of difference in torque that could cause a 1 MPG difference in highway driving, is also small enough that you wouldn't notice it. You'd have to measure it on a dyno.

As for the lack of smell, running with amount of advance you are in the ignition, you might be getting a more complete burn than normal, which would help mitigate it. However it's a common complaint for people who remove the cat on their Fiero.
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dobey
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Report this Post12-19-2013 04:03 PM Click Here to See the Profile for dobeySend a Private Message to dobeyEdit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
Originally posted by 2.5:
How does one know when they have the right amount of back pressure, is it measurable?


It's measurable/calculable, yes. But the only real way to know the "right" amount is to spend a significant number of hours on a dyno, measuring everything possible, and tuning the car, to get the right balance between power and MPG.

Generally, even with better flowing aftermarket exhaust, if you keep the right components in the right places, and use the right size tubing, it will be close enough. The factory engine in the Fiero was built and designed to be run with the convertor in the exhaust system, and the ECM programming is also part of that. Removing it can have an adverse affect on performance/MPG, even if it's small enough that most people won't notice it.
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Report this Post12-19-2013 11:42 PM Click Here to See the Profile for cmechmannClick Here to Email cmechmannSend a Private Message to cmechmannEdit/Delete MessageReply w/QuoteDirect Link to This Post
I would be curious as to when you did the last mods.
Between September and now we have had a big change in temps.
With that, longer warm up times. Later TCC(until warm).
My brother lives just outside of Suffolk and my father used to live near Fredricksburg. I can tell you unless the pumps state no ethanol, there is at least 10%. Most likely more. And the ill effects are felt more during cold weather.
Last winter did a run from Maryland to Alabama. The mileage did increase a little in the warmer areas.
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Report this Post12-20-2013 12:11 AM Click Here to See the Profile for KhwClick Here to Email KhwSend a Private Message to KhwEdit/Delete MessageReply w/QuoteDirect Link to This Post
Has it been awhile since you drove it? As in, could it have had summer blend gas in it and you recently filled it up with winter blend? If I remember correctly, winter blend usually causes a mile or so per gallon drop.
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Report this Post12-20-2013 12:29 AM Click Here to See the Profile for KurtAKXSend a Private Message to KurtAKXEdit/Delete MessageReply w/QuoteDirect Link to This Post
The "reduced back-pressure creating a loss in low-end torque" is horseshit. This old wives tale is the result of but dyno perception error; the back pressure kills performance at higher engine speeds so the low end feels comparatively better.

The only way to reduce torque with a reduction in back pressure is to do something which kills scavenging, (like running without exhaust manifolds, for example)
"Scavenging" is taking advantage of the inertia of the exhaust gas in evacuating the cylinder.

Logically, more back pressure means the cylinder doesn't get as empty, which means there's less room available for fresh fuel and air in the next charge. This is oversimplifying, but that residual fraction left in the cylinder from high back pressure is basically the same as having your EGR valve recirculating exhaust while trying to go full throttle.

[This message has been edited by KurtAKX (edited 12-20-2013).]

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RayOtton
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Report this Post12-20-2013 06:28 AM Click Here to See the Profile for RayOttonClick Here to Email RayOttonSend a Private Message to RayOttonEdit/Delete MessageReply w/QuoteDirect Link to This Post
I live on the Chesapeake Bay in a marine friendly town. Fortunately, because of that there, are two stations that supply non-ethanol fuel which I use in all my vehicles. I learned my lesson after having my brand new outboard fuel pump and injectors replaced after 15 hours. The additive that Yamaha sells that's supposed to work with ethanol didn't work at all.

FWIW, there's a website that lists the non-ethanol gas stations in every state. I was able to use them about 80% of the time on our last cross country trip.

I suppose it could be the switch to winter blend fuel that's causing the reduction. I was hoping I'd missed something simple and maybe that's it.

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Report this Post12-20-2013 06:31 AM Click Here to See the Profile for fieroguruSend a Private Message to fieroguruEdit/Delete MessageReply w/QuoteDirect Link to This Post
I agree, its likely ambient temp/winter blend related, but I would also expect the engine to want more ignition timing than stock at cruise with better cylinder filling. However, w/o a knock sensor you have to be very careful with adjustments. Also, the MPG benefits of an egr (by reducing pumping losses) are related to engine displacement, so smaller engines see less of a gain than the larger ones. On 2.8's I normally delete the egr and have seen up to 32 MPG at interstate speeds with a 5 speed in the summer months.
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Report this Post12-20-2013 02:36 PM Click Here to See the Profile for JohnWPBClick Here to visit JohnWPB's HomePageSend a Private Message to JohnWPBEdit/Delete MessageReply w/QuoteDirect Link to This Post
I am NO expert when it comes to these things, just some information I have heard over time, and contemplating possibilities. 80 Pounds is not that much when you are talking about highway driving. When you have it up to speed, maintaining that speed, Most of your fuel being burned is due to wind drag.

I would try putting the spoiler back on and running the same MPG test that you did. The spoiler does help alter the wind coming over the car and alter the wind stream / drag. Those improvements could more than counteract the weight of the spoiler. The results could be the same, or quite surprising.
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Report this Post12-20-2013 02:48 PM Click Here to See the Profile for PatrickClick Here to Email PatrickSend a Private Message to PatrickEdit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
Originally posted by RayOtton:

If you like your mileage you can keep it.


I thought you were going to explain how to disconnect the odometer.
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Report this Post12-20-2013 04:01 PM Click Here to See the Profile for Old LarSend a Private Message to Old LarEdit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
Originally posted by dobey:


It's measurable/calculable, yes. But the only real way to know the "right" amount is to spend a significant number of hours on a dyno, measuring everything possible, and tuning the car, to get the right balance between power and MPG.

Generally, even with better flowing aftermarket exhaust, if you keep the right components in the right places, and use the right size tubing, it will be close enough. The factory engine in the Fiero was built and designed to be run with the convertor in the exhaust system, and the ECM programming is also part of that. Removing it can have an adverse affect on performance/MPG, even if it's small enough that most people won't notice it.


I have records of all my gas usage and keep an excel spread sheet. I have done this for all my cars, and the records I have for my HHR is 29.4 average long term MPG with 1 sigma of 2.8 mpg. If you use statistics, 3 sigma is the acceptable range or +/- 8.4 mpg is statistically different mpg. I have all this data for the 127,000 miles on the car A car with a 1 mpg shift up or down becomes insignificant. When I replaced the tires on my HHR I saw a consistent drop of about 2 mpg at that time (statistically insignificant). It is hard to determine what can cause a mpg change unless you track anything and everything you do to your car and have all the records of what you do to the car.

I need to get a life, I know.

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Report this Post12-21-2013 11:44 AM Click Here to See the Profile for Tony KaniaSend a Private Message to Tony KaniaEdit/Delete MessageReply w/QuoteDirect Link to This Post
Read the latest issue of Motor Trend. There is a great article of how mpg figures are influenced. There are so many variables to consider. Many I did not ever think of in my 41 years. Technical stuff folks.
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RayOtton
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Report this Post12-21-2013 01:20 PM Click Here to See the Profile for RayOttonClick Here to Email RayOttonSend a Private Message to RayOttonEdit/Delete MessageReply w/QuoteDirect Link to This Post
I understand that there are a myriad of variables involved in this.

Still, I drove the car over the same roads with the same traffic, same fuel, same payload, same tire pressure and with the same style and I am seeing a consistent 1 - 2 MPG decrease since installing the new intake and exhaust.

Also, the wing has been off since a week after I bought the car so the 24-26 MPG figure takes that into account.

So my concern was whether I'd missed something in setting up the engine with the mods but maybe it's as simple as the fuel formulation.

In any case, thanks for the input
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Report this Post12-21-2013 01:59 PM Click Here to See the Profile for Tony KaniaSend a Private Message to Tony KaniaEdit/Delete MessageReply w/QuoteDirect Link to This Post
From what I have learned by the Motor Trend article, fuel from the same gas station can give up to a 7% difference in numbers. MT is using a formulation of fuel that is recordable in its makeup alleviating that percentage of sway.
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Report this Post12-22-2013 06:18 PM Click Here to See the Profile for WKDFIROClick Here to Email WKDFIROSend a Private Message to WKDFIROEdit/Delete MessageReply w/QuoteDirect Link to This Post
I'm curious and perhaps someone can answer the question about the 190 deg fan switch. If the fan were to come on at 190 deg when does it turn off?

Could that be where he's losing some mpg if the fan is turning off while cooling it to closed loop?

The previous owner of my 87 GT went with a 160 switch and I'm not only getting horrible mpg but its starting to affect the plugs.

I typically, with my Fieros, went with a manual fan switch (on if sitting in traffic or sharking for parking) and stayed with a 180 thermostat with the stock fan switch.
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Report this Post12-22-2013 11:21 PM Click Here to See the Profile for dobeySend a Private Message to dobeyEdit/Delete MessageReply w/QuoteDirect Link to This Post
 
quote
Originally posted by WKDFIRO:

I'm curious and perhaps someone can answer the question about the 190 deg fan switch. If the fan were to come on at 190 deg when does it turn off?

Could that be where he's losing some mpg if the fan is turning off while cooling it to closed loop?

The previous owner of my 87 GT went with a 160 switch and I'm not only getting horrible mpg but its starting to affect the plugs.

I typically, with my Fieros, went with a manual fan switch (on if sitting in traffic or sharking for parking) and stayed with a 180 thermostat with the stock fan switch.


You're probably not getting horrible MPG because of the fan switch or thermostat. I got the same MPG in my 87 GT whether I had the stock thermostat, a 160 degree thermostat, or no thermostat at all. The engine doesn't have to be running at 200 degrees for the ECM to be in closed loop mode. The thermostat/switch might give a small change in MPG, but nothing on the order of going from good/reasonable to horrible, unless you only drive very short distances and the engine doesn't have time to get to a reasonable operating temperature.
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