The cold start valve and air tube seem like a redunance to me.

If the throttle is closed when the engine is cold, doesnt the IAC
act like a carberator "choke" and allow JUST ENOUGH air for
starting?


If this is the case,the engine should'nt really need the air tube, right?
My 91' astro has TBI and doesnt need an air tube or cold start valve
and it only has TWO INJECTORS!
(The fiero has SIX injectors and a fuel valve!?!)


The reason for asking is, I plane to eventually take the top manifold off
and remove any unnecessary vac. line clutter for a cleaner, sano intake.
( IE egr, egr tube, air tube, etc.)

Even though some of this stuff is HIDDEN, it buggs me knowing you
CANT periodically check these items for looseness or cracked hoses.

Everything is buried!!!


I already ditched the ridiculous throttlebody coolant tubes,
the egr solenoid and vac. lines, and the evaporator canister and lines


The cold start air tube SEEMS unnecessary.


If the IAC acts like a choke, and the main injectors still fire,
there should be plenty of fuel for cold starting WITHOUT
the cold start valve and tube, right???


Maybe my minimalist mindset is on hyper drive,
but dang I like SIMPLE ,clean looking engines.


If I could get away with it, I'd get rid of the IAC
and the CSV too!!!

The purpose of a carburetor choke is to act as a restriction in the venturi.
With airflow through the venturi, and the choke closed, this reduces pressure inside the carburetor.
The greater pressure difference across the jets cause the mixture to be enriched.

Fieros are fuel injected, the computer can just command higher injector duty cycles if enrichment is needed...

Now, for the IAC, it's purpose is NOT to act as a choke.
It simply allows a computer-determined amount of air to bypass the throttle body, through the air tube, and into the intake manifold.

If you remove the IAC / air tube, there will no longer be any computer idle control. You will have to rely on the throttle stop screw.
Then, you won't be able to compensate for cold temperatures, varying electrical loads, etc...

The throttle body coolant lines are not ridiculous. The local velocity of air is high around the IAC pintle. This causes a local pressure drop. Which reduces temperature. In conditions of already low temperature and high relative humidity, this can reduce the temperature below the dewpoint of the air. Which will cause icing of the IAC passage. I regret having deleted mine. In the past year I've been running without the TB coolant lines, my IAC passage iced up twice.

I think your deep down desire is a carb conversion!
In doing so, you'll unclutter the engine, and get a better flowing intake manifold than the stock one.

only car I know of that uses this crap.....

but, on thing you are missing: the IAC dumps the air into the air tube, not the plenums like modern IACs
so, unless you re-locate the IAC air path, the cold start air tube is needed.

I did the 7730 ECM swap, so I no longer need the cold start system. But, untill I replace the throttle body/plenum system - I must keep the air tube. I plan on using the 3.4 Camaro plenum setup, once I find one at the "U-Pull-It" yard. and yes - then I will no longer need the air tube system. and, have had day dreams of maybe re-tasking the cold start system for nitrous

Please excuse my obvious ignorance, but is this for the 2.5 or the 2.8? Or is this something that can go either way?

------------------
4,500 RPM in 5th gear is bad?

The Duke will NEVER DIE

I see you're from Michigan. You can do as you like, but if you remove the "coolant lines" (they're actually heater lines) to the throttle body, you will likely regret it as ice can and does build up not only on the IAC valve, which only impacts you at idle, but also on your throttle plate and TB throat. This has much more serious implications since you can find yourself cruising along the highway and have your throttle frozen open. Try explaining to the accident reconstruction inspector why your lines aren't connected after you take out a half dozen cars at the end of the off ramp. And then, it only takes about two to three minutes of sitting there with the engine stopped for the engine heat to melt any evidence of what happened. Your insurance company will have a hard time believing that you just didn't mistake the gas pedal for the brake pedal.

As for the cold start injector, it's not advisable to remove it unless you plan on driving the car in the late spring, summer, and early fall only. More than that, you'll spend a fair bit of time cranking the engine over to start it. Here's the description straight from the service manual: "This circuit is important when engine coolant temperature is very low because the other six injectors would not be pulsed "ON" long enough to provide the needed amount of fuel to start. The system is controlled by a cold start injection switch which provides a ground path for the valve during cranking whenever engine coolant is below 35*C (95*F). The switch allows the cold start valve to stay on for 8 seconds at -20*C (-4*F) or below. Above -20*C the maximum time the switch will stay open is proportional to the coolant temperature." From my own experience, I had a leak at the O ring where the fuel supply line connects onto the injector, only to find that they were no longer available. During the two week period it took to find a fuel compatible O ring that would fit, I drove my car in late September with the system blocked off. Be prepared to crank the engine for ten or more seconds before you get it to cough and start.

There is no 'cold start air tube' The IAC tube is what allows the engine to idle... helpful in todays world of 'on the go' commuters that want the engine to run.

The IAC allows the computer to dynamically adjust the amount of airflow into the engine at idle, allowing for compensation for loads like AC or high alternator loads, as well as adjustment of idle mixture and timing at idle to improve idle quality, emissions, and economy.

Every EFI car has a form of the IAC tube, some its internal to the TB.

As for the cold start injector, Fieros arent the only cars, a lot of cars including vettes had them. It temprarilally (while the starter is engaged and while the tempature is below a set point) enriches the mixture, allowing for better cold weather starting, and faster starting in general, so you dont have to pump the pedal. Granted this could have been integrated into the ECM and injectors, but its function is very helpful.

The TB coolant lines, as stated above, are not there to cool the TB, but to prevent it from icing over in the winter.

So far, the Fiero V6 is the only of its type that I've seen with the separate IAC tube and cold-start injector. All the other cars I've seen with a 60-degree V6 have the IAC passage built into the throttle body, and programming in the ECM for cold-start fuel enrichment. That's most likely the result of the Fiero being a test-mule for MPFI technology.

quote Originally posted by 86GT3.4DOHC: There is no 'cold start air tube' The IAC tube is what allows the engine to idle... helpful in todays world of 'on the go' commuters that want the engine to run.

LOL

Pmbrunelle,

I appreciate your reply.
But, I disagree somewhat.
The IAC does (in a round about way) ACT like a choke.
Initially,it only lets in enough air for start up.
When the engine is warmed up and running,
THEN the IAC becomes a more precision piece,
by regulating engine idle for various loads.

I already removed the A/C, and most electrical loads
dont affect my idle much, so the IAC just
seems like a trifle that could be bypassed
thats all.
Sorry if my questioning structure may
come off sounding a bit haphazard.
Actually, I HAVE comtemplated using just
the idle screw instead of the IAC, since the
engine upon start up always revs to 3000rpm
then EVENTUALLY drops to normal.


Again,
I have to disagree on the throttlebody coolant lines,
the entire throttlebody is positioned right over an
EXHAUST PIPE.
The cat (if you have one) ,and or glasspack(which i have),
is also positioned a few feet away.
With BOTH of these heat sources located close to the
bulkhead, T.B. warm up should'nt be a problem.
Michigan winters can get pretty damn cold,
and I NEVER (knock on wood) had a problem with starting
or idling in below freezing weather.
In fact, my fiero seems to run the best in cold weather
if I do say so myself.


What problems are you experiencing from T.B. icing???


Is the throttle sticking, odd idle?


A little elec. heater would be better.
The computer could SHUT IT OFF
when not needed.
(closed loop.)
Besides, Your throttlebody doesnt need HOT coolant
flowing through it when its summertime and 90 degress outside!!!!


My 2 cents,
but I think GM engineers look for EXTRA
little projects to keep themselves busy


Think about it,
whenever you go to get a part or whatnot,
there is like three different versions of the SAME
PART!
(Map sensors,egrs, IACS,clutch masters,clutch slaves
dist. etc. etc.)
If GM would just pick the BEST out of each catagory of
parts, and incorparate some adjustability, GM would
save money, WE would save money(and sanity)
and the parts suppliers would probably save money.

Also,
correct me if i'm wrong,
but it sounded like you agree that the coldstart valve
ISNT needed.
Too bad the CSV tube isnt needed as well.
I AGREE ,The injectors by themselves SHOULD be suffient
for coldstarting.
And, if the "cold start tube" is used primarily by the IAC,
then the diagram on page 139 in the haynes fiero manel is a typo.
(#5 exploded parts view)
The manuel should state "IAC air tube" instead to avert any misunderstandings.

I will admit that a carb conversion HAS crossed my mind.
But, you usually LOSE horsepower AND mpg
when you convert to a carb.


A dual throttlebody convert would be better,
but I got too much on my plate right now what
with bodywork, and clutch hyd./ cable problems.
Not to mention, the van needs plate/ tabs PRETTY SOON,
as well as leaf springs and exhaust.
Just looking to remove any engine clutter.


"Stock IS a compromise"

Brian.

Do your self a favor as well dont remove things like the EGR for "pretty" factor. Not only is it more pointless needless pollution but its going to decrease gas mileage as well with no performance gain. Im no tree hugger myself but these systems are NOT pointless and should be kept you will not gain "uber mad tyte permance" by eliminating emissions equipment ( Im lookin at you straight pipers )

Wow, alot of feedback since I last checked.

Thankyou for your replys though!

quote Originally posted by sunofjustice: Wow, alot of feedback since I last checked.

Wow indeed. There's lots of people here with decades of experience working with Fieros in particular and fuel injection systems in general providing you advice, but it sounds like you've made up your mind on just about everything regardless of what we say. My second-to-last piece of advice at this point is that you should do everything you planned and post how well your car runs after the mods. My last advice is to be sure not to throw away the extra pieces on garbage day.

quote Originally posted by Bloozberry: Wow indeed. There's lots of people here with decades of experience working with Fieros in particular and fuel injection systems in general providing you advice, but it sounds like you've made up your mind on just about everything regardless of what we say. My second-to-last piece of advice at this point is that you should do everything you planned and post how well your car runs after the mods. My last advice is to be sure not to throw away the extra pieces on garbage day.

X2

Bloozberry,


Even though I may not sound like it,
I'm pretty cautious WHENEVER I remove
or modify a stock part.


I always do a "wait and see" BEFORE
tossing ANYthing.


Regardless,
I accept your challenge, dear sir!
Maybe not all I mentioned,
but some of it.
Experimentation awaits.
AVANTI!


"to boldly go where no man has gone before..."

[This message has been edited by sunofjustice (edited 09-04-2009).]

It's actually more like indignantly going where most have already gone before and ignoring thier advice...

[This message has been edited by carbon (edited 09-04-2009).]

No offense,
but I KNOW this topic is small fry stuff.
Just standing my ground,
and trying to have some fun with it.

[This message has been edited by sunofjustice (edited 09-04-2009).]

quote Originally posted by sunofjustice: Michigan winters can get pretty damn cold, and I NEVER (knock on wood) had a problem with starting or idling in below freezing weather. In fact, my fiero seems to run the best in cold weather if I do say so myself. What problems are you experiencing from T.B. icing???

Obviously you won't have a problem with icing when it's below freezing. The humidity level is too low.

Do some reading on the dewpoint of air, and its relationship to pressure and temperature.

My problem with icing occurred at about 50 degrees Fahrenheit, while it was super muggy. The IAC passage iced up, preventing the IAC motor from being able to move. It was stuck in high idle.

And no, it does not matter that there is a hot engine right next to the throttle body. As long as there is airflow through the passage, it will stay iced up.

The only way to get the IAC unstuck is to stop the engine, which stops the cold humid air from flowing through the throttle body. THEN, the engine heat was able to melt the ice, and the IAC was free to move again.

Icing isn't dangerous if you can keep a cool head. Even if the main butterfly were to ice, it's not complicated to declutch and turn off the ignition switch. More of an inconvenience/hassle/drivability issue, but still, don't you want a car that runs great?

quote Originally posted by sunofjustice: A little elec. heater would be better. The computer could SHUT IT OFF when not needed. (closed loop.) Besides, Your throttlebody doesnt need HOT coolant flowing through it when its summertime and 90 degress outside!!!! My 2 cents, but I think GM engineers look for EXTRA little projects to keep themselves busy

Look again. The GM engineers were more clever than you thought. There are two coolant lines, one connected upstream of the thermostat, the other downstream.

When the engine is cold, coolant flows through the throttle body circuit.

When the engine is hot, the thermostat opens. Rather than flowing through the throttle body circuit, the coolant takes the path of least resistance. Right through the thermostat.

An elegant design in my opinion! Heats the throttle body when cold, bypasses when hot, without any electronic controls.

The carbon that collects on the back of valves due to EGR will most certainly reduce performance though. Undercut valves wouldn't exist if the shape at the bottom of the valve stem didn't matter. It's up to you though whether you want to trade the fuel economy for it.

EGR can actually improve performance at WOT though. EGR reduces cylinder temperatures in low load cruising, so that when you put your foot in it, you'll have cooler cylinders. Meaning, less hotspots, less likely to detonate. You can probably run more timing advance because of this.

I would leave PCV connected. Combustion gases that are not vented from your crankcase are acidic, and you really don't want that crap in your crankcase. You can use breathers passively vented to atmosphere, or a road draft tube...but it's still not as good as Positive Crankcase Ventilation. Otherwise, I'd want to change my oil on a more regular basis...

pmbrunelle,

The coolant tubes are still connected to the thermostat housing.
Metal lines can serve as a thermal conduit eventually resulting
in a heated throttlebody non the less.


The THEORY and execution behind how the coolant tubes sound
irrefutable, but I still find the aesthetics detestable.
Not to mention quite cumbersome when attempting to
service my ignition.
Thusly, I removed them.
Plenty of room, visually pleasing.

Since doing this mod, (back in 2000) there has'nt been ANY adverse effects
and/or multi car pile up debacles, thank you much.
Furthermore, my car ran GREAT without these tubes,
If it did'nt I would have reinstalled them, which I havent.


The only reason the egr is STILL on my fiero is, I'm familiar with the
pretense that an egr can COOL the combustion chamber.
Back when the egr was functional , I bought an all NEW egr,egr solenoid,and vac lines.
However, this was an excercise in futility.
The car would still run somewhat hot,due mainly to the fact that this IS a REAR engine
equipped vehicle with no fan in the rear.
I'm sure you can attest that fieros run great WHEN MOVING.
But, get stuck in bumper to bumper traffic and she will harbor umbrage
in the form of a lazy throttle and a possible boil over.


Yes, timing could be advanced......../IF you use a higher grade of fuel in tandem.

Using top-tier grades of petrol such as CHEVRON, SHELL,TEXACO etc.with the
highest yielding detergants helps as well.
(I still prefer MOBIL or BP, but I read they did'nt pay the fees
for testing that allow you to claim yourself top-tier.)


As far as the PCV is concerned, I strongly believe in them!!!
Yes,Positive Crank Ventalation helps remove blowby that ultimately
results in faster oil contaimanation, BUT it also helps seal piston rings
allowing the engine to attain its true performance potential.
I HAD plans to use an old racer trick (header crankcase evac. kit)
But, further research on the net concluded that it ONLY worked at 4000rpm
and above.
Even though we can rev that high, Ive read that continueous high revving
DOES NOT promote loooonger engine life.


A vacuum pump would allow removal of crankcase vapor.
Plus, add power (usually 2-5% gain or 9 rwhp)
Normally,the pistons have to overcome atmospheric pressure
(or 14.7 psi) in the engines crankcase.
To get MORE power,you have to lower the pressure in the crankcase.
A vacuum pump can acomplish this with aplomb.
However, it would probably negate ANY real horsepower benefits
on a mildly modifyed engine.
Since it roughly requires 8-10 hp to run a vac. pump.
Alky motors ,and HI compression engines usually benefit the most from them.
In theroy, you would still get SOME benefits.
(less blow by, less windage energy loss,nice ring seal.)
Although oil vapor would be removed, there IS a danger of
OVER VACUUMING.


If I recall, no more than 12-14 psi.
Otherwise ,oil misting is removed from either
the crank rods or mains, I forget.

You COULD try using a elec. vac pump like the grand natl. guys use,
Only foreseeable determent would be that they tend to OVERHEAT
with continuous operation. They are only good for intermittant usage.
(Dragstrip 1/4 mile)
The best method of REMOVING any excess oil vapor in the pcv
that is simple, thrifty, and very effective is the vac. catch can.
I had planned to do a write up on it here as well on another site
(which has a seven page sticky on hotrodding the 4.3 by the way)
but, what the hey..........


Vacuum catch cans are EASY to make for the DIY, and a COMPLETE system
can be purchased under $40. if you look. I'd flash you some pics but For some reason,
my pip is on hiatus.
I'll have to do a defrag on my trusty (maybe rusty) windows '98 and try again.

[This message has been edited by sunofjustice (edited 09-06-2009).]

quote Originally posted by sunofjustice: Cold start valve and air tube, is the fiero the ONLY car that uses this crap???

In various forms this "crap" design has been around forever. The Jaguar XK-120 sports car and MK-VII sedan (1948-1953), for example, employed a completely separate, solenoid-controlled carburetor and air tube for cold-start enrichment since SU and Zenith carburetors of the time didn't lend themselves to a simple choke butterfly design. A lot of other cars have had similar arrangements. It's not very elegant, but it works.

quote The THEORY and execution behind how the coolant tubes sound irrefutable, but I still find the aesthetics detestable. .. Thusly, I removed them. A paper filter RESTRICTS the incoming air more than a K&N. Slower moving airflow might have caused the throttle to ice up. ... I'm familiar with the pretense that an egr can COOL the combustion chamber. ... The car would still run somewhat hot,due mainly to the fact that this IS a REAR engine equipped vehicle with no fan in the rear. A vacuum pump would allow removal of crankcase vapor. ... To get MORE power,you have to lower the pressure in the crankcase. A vacuum pump can acomplish this with aplomb.

As far as I'm concerned, you can make any legal modification to your car that you want. But I have to say that, at least in this thread, you're a veritable fountain of misinformation.

For example, EGR is not active when sitting in traffic at idle, and a properly-functioning EGR system actually reduces the heat load on an engine's cooling system ... a beneficial result of lower peak combustion temperatures.

Concerning throttle body icing, I'll post a diagram later today that illustrates why it is most likely to occur at ambient temperatures of 30 F to 70 F, not when the temperature is below freezing. pmbrunelle is doubly correct when he states 1) that TB icing is less likely to occur at temperatures below freezing, and 2) that the primary reason for this is that there is so little water vapor present in the air at low temperatures.

quote Originally posted by pmbrunelle: EGR can actually improve performance at WOT though. EGR reduces cylinder temperatures in low load cruising, so that when you put your foot in it, you'll have cooler cylinders. Meaning, less hotspots, less likely to detonate. You can probably run more timing advance because of this.

I have to disagree with this, though. First, in all the engines I've ever encountered (including the Fiero) EGR is active only at low to moderate throttle settings and RPM ... e.g. when cruising at moderate speed ... and never at full throttle and/or high RPM. EGR doesn't reduce "cylinder temperatures," it slows the combustion burn rate and thereby reduces the peak combustion temperature of the gases inside the cylinder ... an important distinction. Especially in a water-cooled engine, each combustion event in a cylinder is pretty much independent of the preceding one.

[This message has been edited by Marvin McInnis (edited 03-11-2010).]

This morning, I was mulling over any possible , preventative actions
for "throttle icing".
Mainly,for those who wish to delete the throttle coolant lines for various reasons,
but are concerned with safety.

There are probably four different methods that should yield satisfactory, cold-
weather performance for the fieros throttle body.

1. WD 40

Even though it was primarily invented to prevent rust on sheet metal,
people still use it as a lubricant. Although, i presume, most people
continue to use it for its olfactory, stimulating tendacies.

2. Synthetic motor oil (10 W 20 or 30)

Synthetic moto oil is well known for its robust, cold weather lubrication.
Applying a modest, judicious amount upon the throttle blade(and IAC pintel) should suffice.
(a little dab will do ya.)

3. Antifreeze

A bit unorthodox, but the name in it self says it all.
Since antifreeze IS very slippery to the touch,and WILL NOT freeze.
A minuscule dollop, lightly rubbed on the throttle blade and surrounding area,
(plus IAC pintel)
should guarantee full freedom of throttle movement in adverse cold weather.

4. Thermal blanket insulation (plumbing supplies)

Not very aesthetic, and a bit crude......but, COULD be used in tandem
with one of the previous mentioned suggestions.

For those who do not wish to use any of these methods,
but find that the coolant lines on the throttle body Due get in
the way when working upon the distributer, you could keep
the hard, end fittings and use FLEXIBLE heater hose with
additional length to attach them to.

This modification can also broach some possible, visual customization
by incorporating different colored hose. If this is desired.

[This message has been edited by sunofjustice (edited 09-06-2009).]

From FAA data:



This data applies primarily to carbureted aircraft engines, where throttle plate icing is more of a problem, but it applies to the throttle bodies of fuel-injected engines as well. There are three primary causes of temperature drop in an engine's induction system: 1) fuel evaporation, 2) pressure drop through a carburetor's venturi, and 3) the abrupt pressure drop across the throttle plate and IAC pintle. Only the third is significant in the V6 Fieros. Note that icing can (and does) still occur at temperatures of over 100 F (40 C) as long as sufficient water vapor is present in the air!

[This message has been edited by Marvin McInnis (edited 09-06-2009).]

Marvin Mcinnis,

Me thinks you might be an engineer and maybe I touched a nerve?

Or maybe you just dont like the word "crap".

To be fair,
For those who ARE engineers, I apologize for any preconceived notion
of callousness toward you,and or your work.


This is still America last time I looked, and my opinions as well as view points,
(as long as they are civil and upright) ,should'nt bring about ragnaro'k

initially, I was just weighing " maybe I could ", or "maybe I should'nt" in my
head. But, my whimsical intent kept getting misinterpreted somehow during debating issues.

Regardless,
I dont really have a problem with retaining the IAC,I just dont like the way it controls
my idle once started. (3000 rpm, then drops down to 1000rpm)
Thats why I JOKINGLY suggested getting rid of it.

Furthermore,
I still believe the "cold start tube" or "iac tube" can be successfully removed, but ONLY with a computer retune done before hand.
Since the injectors dont pulse long enough for cold weather starting with my current computer.
For idle control, the throttlebody idle screw should suffice.
If a computer tune cannot accomplish this, then I will go back to using the IAC
for idle control.


Marvin Mcinnis,
you are incorrect about the egr not working at idle.
The egr works the BEST at idle, or zero throttle load.
Mainly, due to a higher vacuum.
How could you miss this little factoid?

Even if the egr DID help "slow the combustion burn rate" ...blah blah
and "reduces peak combustion temperature of the gases"...blah blah
it STILL introduces CARBON DEPOSITS that eventually, over time, would
ultimately REDUCE performance via sticking piston rings, and carbon coated
valves.

Maybe in kansas city you still have to take smog tests,
(or maybe you are an "all stock devotee"?)
Thats fine if you are.
but here in michigan ,older vehicles are exempt from smog tests.
Plus, most of the said older vehicles are classics,which DONT run
egr and, like my fiero, are in a minority.


I reiterate, my car has LIMITED usage.
It IS very well maintained as far as tuneups
and oilchanges, even if the emissions are disabled.
In juxtapostion, there are many fairly modern cars,
with their emissions still hooked up, that drive
around oblivious to the fact they are polluting
because they DONT TUNE their car.


Airfilters clogged up, sparkplugs and wires neglected,worn out sensors,
even low air in the tires contributes to loss of mpg and increased fuel consumption.
Creating more pollution.

Mechanicals are only half the equation, HOW you drive can also increase pollution.

Short stop and go trips, jack rabbit starts, excessive idling, over revving ,
all of these factors are of significant concern.

I try to avoid any of these said derogatory actions.

As testament to such,


Every car I've own, I use a dash mounted vacuum gauge .
these are VERY useful for monitoring throttle position
(in relation to engine vacuum)
so as to make readjustments to the throttle pedal for BETTER mpg.


Once you install a dash mounted vac. gauge,
you will be amazed at how leadfooted you really are.

Once accustomed to using said a vac. gauge,
you will have fun with it by perfecting your mpg driving
technique.

So, in closing , pollution can come from many OTHER sources
other than a deleted egr and its various nomenclature.
Sorry if you are pro egr and I offended you somehow.
I just dont want to use it, thats all.

quote Originally posted by sunofjustice: you are incorrect about the egr not working at idle. The egr works the BEST at idle, or zero throttle load. Mainly, due to a higher vacuum. How could you miss this little factoid?

How could I miss it? Because it's not true. You need to go do some research on how EGR control is programmed into the Fiero ECMs and then report back to us. Alternatively, you could just go out and actually observe the EGR valve on a Fiero under different engine load conditions. Hint: If the engine is otherwise healthy, throttle-closed idle is the operating condition where high combustion temperatures are least likely to be a problem with regard to NOx formation.

I agree that EGR dirties up the intake manifold, as does PCV. I don't like that part either. Cars can and do meet emissions standards without resorting to EGR, but in the Fiero EGR actually manages to decrease NOx emissions, decrease fuel octane requirement, and increase part-throttle fuel economy ... all at the same time. Except for the dirty intake manifold and additional maintenance requirements, EGR is a win ... win ... win proposition. On the other hand, there are Fiero owners who have disabled EGR and have reported their results. Those who were 100% successful not only removed the EGR plumbing but also disabled EGR in the ECM; unless you do that you will end up with too much ignition timing advance when the ECM thinks it is commanding EGR.

As I said earlier, you are certainly free to do anything you want to your car ... legal or illegal, wise or foolish, and what I think of it is immaterial. Experimentation is one of the fun aspects of our automotive hobby. What I do object to is someone posting technical information that's just plain wrong, and then refusing to acknowledge it when someone else offers a correction.

[This message has been edited by Marvin McInnis (edited 09-06-2009).]

quote Originally posted by Marvin McInnis: I have to disagree with this, though. First, in all the engines I've ever encountered (including the Fiero) EGR is active only at low to moderate throttle settings and RPM ... e.g. when cruising at moderate speed ... and never at full throttle and/or high RPM. EGR doesn't reduce "cylinder temperatures," it slows the combustion burn rate and thereby reduces the peak combustion temperature of the gases inside the cylinder ... an important distinction. Especially in a water-cooled engine, each combustion event in a cylinder is pretty much independent of the preceding one.

To be honest, I kind of pulled that one out of my ass, it was more of an idea than a fact I knew.

I was saying that the combustion event is not independent of previous ones, that there may be lingering effects of cruise operation while at WOT.

To know for sure, the best would be to see a modern engine with timing controlled by knock sensor, and then see if there is a timing difference at WOT depending if EGR was active during cruise.

Marvin McInnis,

Point blank, I'll admit I was incorrect about egr working best at idle,
when its really at higher rpms, my bad.
I'll also admit, its been roughly twenty years since the last time I had to do
a smog check in this state as well.
So, maybe you can understand that I'm not too enthusiastic about smog devices
and the myriad of tech terms to discribe how they work.

Plus, every car of mine that had an egr (four), even with meticulous attention to
tune-ups and maintenance, ran like defecation in its stock configuration.
I would ALWAYS try to work with these systems by cleaning,testing,and replacing them
if worn out.
What was GM's slogan back then? "keep your GM car ALL GM". "Use ONLY ac delco parts"


Like a mindless drone, I would buy ONLY ac delco.
I'd follow EVERYTHING it said in the Chiltons manual to a "T".
(circa 1986)
But, the car would NEVER perform well!
In hindsight, two WERE 1970's cars though. lol


Swapping in a better factory carb/intake helped somewhat.
Remember the pontiac 301 V8?
I adjusted the timing, uncoverd the idle mixture screws ,
added a brass float, NUMEROUS jet changes, vac. secondary screw adjustments,
epoxyed the infamous Q- jet fuel leak, replaced the fuel filter/pump, checked for fuel line restrictions,
went to true duels, Still sucked.
Classic case of trying to make silk out of a sows ear.


Using stock parts just feels limiting to me.
Everything seems to be more biased towards emissions.
Wheres the thrill of spirted driving???
Why should I accept this mediocre performance?
For that main reason, I turned to the aftermarket and started hotrodding.
I wanted to turn my lemon into lemonade.

To be fair, the aftermarket performance industry CAN be just as bad
(or worse) than factory.
However, I've achieved some significant progress out of my current vehicles
by deleting the stock smog equiptment.
I've been aware for years that a computer tune is necessary for optimum performance,
the drawback is you have to have ALL your modifications done BEFORE having a chip
burned.
At $300.-400. per custom chip, I obviously procrastonated and just settled for moderate
performance until all my future modifications were accomplished.


A few months ago, i found a computer modification that is for OBD1,
has EIGHT fuel bin files to choose from ($80. optional dash mounted switch),
allows egr shut off, vss changes,close loop /open loop adjustability etc.
is programmable from pc or laptop.


The price was $350.self install, it also involves light soldering, and for an additional
$30. charge they do it for you. (which is cool, because i DONT care for wiring!)
The only reason I havent tried it yet, is my cashflow was jacked up at around the same time of discovery.
I'm JUST now starting to get some free money. (Even if I got to use it to fix the vans leaf springs.)
Since its uncharted territory, and no offense, since most folk here are more critical......
I'll divulge the name after acquiring, and testing this mofo.

Hint: its not sinister perf.


Lastly.... I'll reiterate.....BOTH of my cars (91' astro ,86' fiero gt) run very well without egr.
Sure, Its a given that they require the prerequisite 'puter tune to realize a performance ascension.
Sure, they are probably wasting some mpg.
But, they ARE showing positive results WITHOUT being stone-cold stock.
Quick example, last time I did an impromptu stop light race ( gratiot/metropark road to garfield)
VS chrysler 300.........out of the hole I did pretty good.
Thanks to the aeodynamics of a brick , the 300 pulled about TWO car lengths on me.


The 300's lead did'nt last long either. my van WILL reel you in.
This was my first 4.3 ,and I'm quite impressed with its potential.
One of these in my fiero would be fun!


Other than egr delete, i added dual ram air, k/n with extreme lid,
raised the injector pod 1", added adj. fuel press. regulator,cut the
stock throttle spring and added old style spring(quicker throttle action),
throttle spacer (more torque on tbi's), msd 6a, hypertech 53,000 volt
coil, 300+ wires (wish to upgrade to msd, or taylor thundervolts)
NGK coppers, set at .35 gap to compensate for wear, with a moderate sidegap.


Deleted the mech. fan (15-17hp), added dual e-fan from some old parts in closet.
running the 160 degree stat with redline water wetter.Used to use amsoil,mobil one,
using royal purple (Noticed improvement right away,nothing major but BETTER)
used thermo tech wrap on heater hoses, added b&m transpak (full manual shift mode)
ditched cat, added heated o2 sensor, thrush glass pack (had a dualout magnaflow first,sucked!!!)
custom dual exhaust, fresh 3.73 gear upgrade.
Very simple mods on a stock engine that yield performance, reasonable mileage,
and its still pleasent to drive. (No offense, but all WITHOUT egr.)


Sorry about running off on a tangent, as well as being a bit off topic.
I do tend to lose my focus sometimes. DOH!!!

To all those who contributed their advice ,time, and energy .........
I offer my sincerest apologies for being a stubborn, block head.
Words are cheap, but thats all I got to offer right now.
(Especially since the pip/pip patch ISNT working.)


Actually, your egr advice has given me insight on newer tuning methods,
and brought attention to preventive maintenance, and POTENTIAL problems
with throttle icing.
Even though I have'nt experienced any throttle icing..... at least I can anticipate,
and deploy, a pre emptive strike if you will.

Again................Thank you.

[This message has been edited by sunofjustice (edited 09-06-2009).]

You have to wonder about somebody that would waste time and money modding an astro van!

Whats to wonder,
the fiero is sporty, but you cant carry any large items.
The van is utilitarian , but needed some pep.
Best of both worlds.

Wow... 15-17HP from switching to an electric fan? I will take a wild guess and say that you have never been to a real dyno with anything you own. You also seem to have no clue as to how these various 'smog' components actually work on the Fiero. You are not some Fiero pioneer coming to inform the unwashed masses about all the stuff that they have never thought of to try on their cars. The fact of the matter is, that most everyone here went through the same thoughts that you have had got laughed at and found that they do absolutely nothing for performance... the fact that you even mentioned 'Hypertech' in your mods list for one of your cars says that much. Good luck with ruining what was left of the fuel economy and efficiency of your Fiero. Have fun. And let us know just how much power you've freed up.

[This message has been edited by carbon (edited 09-06-2009).]