Tazman861

iTrader: (2)

Hi all,

I have just fitted a FMIC to my classic and it is booked in for a re-map in a couple of weeks .

My question is this, I have been told I can drive it but I need to drive a couple of hundred miles this weekend. If I keep it off boost and drive like miss daisy will it be OK?

I take it that if I drive with boost the car will underfuel as it will be getting too much air for the amount of fuel going in and that will probably melt a piston?

Thanks...

Stealth

iTrader: (4)

errrmmmm if you have fitted the FMIC I am assuming yuo have fitted an induction kit as well chap?

If by some miracle you have managed to keep the standard air box (or the car was already mapped for an induction kit) you will be fine, nothing changes mate! The car is perfectly safe and it won't underfuel!

You are getting no more air in to the car with the FMIC if you have retained the air filter you had prior to the change, FMIC doe not determine how much air goes i nto the engine, it is simply a greater surface area to cool the air coming in through the airbox/induction kit and i nto the engine...

The FMIC is not a map reliant mod really.

scooby2010

+1
fitted a cone filter with the fmic = remap
cone filter already fitted and mapped = no remap

Tazman861

iTrader: (2)

It has a K&N induction kit and is currently using a Polar Parformance chip to up the boost, change the fueling and ignition maps and allow the use of 97RON fuel.

I will be fitting 440s and a 3bar map sensor before the remap but I had to fit the front mount as its a fair bit of work! There is no way you could keep the standard airbox or resonator as one of the pipes runs straight through where they are fitted!!

sonic93

iTrader: (16)

does need a map it won t run to good with out a map ask split pin,harvey

Stealth

iTrader: (4)

LOL yeah hence my comment "by some miracle" LOL

The car will be fine and will run fine becauase it has already been mapped for the induction kit and the other critical bits and bobs.

haroldhettaturbo

iTrader: (2)

this has always perplexed me.

why do u need a remap when u fit a cone filter?

The air still has to pass via the maf sensor so the ecu knows how much air the engine is getting?

It just enters via a cone filter rather than a panel?

mickywrx

iTrader: (29)

FMIC and standard ECU on mine, not remapped.



<<

Stealth

iTrader: (4)

Because the MAF curve on the ECU is scaled to suit the airbox, if you increase the area and rate that air can pass over the MAF the scaling will be a little wonky and will not give the ECU the correct readings, the engine will be recieving more air than the ECU can compensate for and it will run lean and blow the crap out of the engine.

So in short, no the ECU doesn't KNOW exactly how much air is going in, it thinks it knows how much air is going in.

There is a more complex answer and I'm sure someone will come post it up soon, all to do with air flowing over the MAF, voltage requried to keep it at a specific temp and Lambda readings or summit clever LOL (I am but a simpleton)

Splitpin

Stealth has already explained this very well.

No. The ECU will "know" how much air the engine is getting, yes. The trouble is that the figure it "knows" will be (sometimes very badly) wrong.

In practice the sensor only measures a tiny percentage of the total amount of air going through the measurement tube, and produces a voltage output that represents that amount. The ECU uses that voltage to look up a table that corresponds to the total quantity of air.

If you change the way the air passes through the tube, or change the diameter of the tube, the sensor will output a different voltage for a given amount of air than it did with the standard bits.

Because the ECU has no way of knowing you've skewed the measurement, it will miscalculate the total amount of air going in. The only way to correct that is to rescale the lookup table so that it accurately represents the altered intake configuration.

FB Tuning

iTrader: (30)

As above ^^

Changing the way the air passes over the MAF element (think - swirl and turbulence) or maf tube size, can radically change MAF voltage readings for a given airflow, and hence fuelling (as the ecu derives load values from airflow)

Fitting a wideband lambda sensor, and monitoring your operating AFR's (pre and post Induction Kit fitment) can be quite an eye opener

harvey

iTrader: (48)

The purpose of fitting a front mount is to reduce air charge temperatures and very significant air charge temperature reductions can take place providing you fit an efficient front mount. Reduced air charge temperatures require more fuel and there is a limit to the amount of compensation your ECU can make and at what throttle/load. A lot will depend on what ECU you actually have. Air flow to the engine is also altered because of the addition of the front mount and pipework.
After fitting a front mount you can drive sensibly but if you start giving it the beans you are in an area of great risk and at the very least should have your AFRs checked.
I would not encourage anyone to fit a front mount intercooler without a remap, even if it meant losing an intercooler sale. You could be risking your engine and what is for sure it will not run efficiently until remapped for the new conditions.
Whether you take this advice or not is entirely up to you, your engine, do what you want, we don't mind building them. Yes some people fit a front mount, don't remap, and get away with it but that is what it is and failing to have your AFRs thoroughly checked across various operating perameters particularly on full load is very unwise.

Stealth

iTrader: (4)

Really???? At the end of the day the Inlet manifold is still the same size, the join between the inlet and the Indcution piping is the same size (so there's one bottle neck) and the induction pipe is still the same size as it was prior to the FMIC going on (another bottle neck) so surely the air going is be damn near the same?

The temperature of the air going?? Sure the cooler air going in is densor so when the spark fire you get a more violent explosion making it a more effecient explosion, the AFR's will remain the same won't they as the same amount of air is going in and the same with the fuel.

It's like driving your car in 30+ Degree summer heats and then driving exactly the same car in -5 conditions in the winter..... That doesn't require a remap ??

Correct me if I'm wrong, this is jsut my understanding and I'm happy to be correct as to get a better understanding

Ta

dynamix

iTrader: (3)

There is more actual air if denser/colder.

+1 for getting it remapped.

Stealth

iTrader: (4)

I know there is more Oxygen particles etc etc per given volume in Denser/cold air but is there enough to make such a difference that the car needs a remap ?

Sorry for daft questions.

dynamix

iTrader: (3)

It depends how close to the edge of being safe it was beforehand.

sponners

iTrader: (4)

imo adding a front mount wont give you anymore power if not remapped, it just alows for more ignition/power to be run


so just fitting a larger cooler and no remap will be fine......but you wont see any gains until mapped.


(but, after any breathing mods it is always a good idea to get the fueling/knock checked just to be on the safe side)

Martin 2010

iTrader: (9)

its very hard to tell mate, if your very worried then id get it mapped or get it tested for compression and the other test cant remember what its called now but feistaboy has tested my today and im running FMIC induction kit de cat and Cat back stainless hks. with out a map and although its runing on the lean side its still running more than safe enough and mines still got plenty of compression left in it.

Martin 2010

iTrader: (9)

although thats not me sayin yours will be the same every engine and the way it runs is different and its a 50/50 thing but if i was u id get it checked or mapped mate

harvey

iTrader: (48)

I think there is a basic flaw in your understanding.
Look at it this way.
I don't understand why you are referring to bottlenecks.
The same in what respect.
The air will be at a lower temperature, it is denser, contains more oxygen and therefore requires more fuel to achieve an efficient and safe combustion ratio.
Here is where you may have to reconsider your thinking. Volume of air and weight of air or more importantly, weight of oxygen varies with temperature so obviously the AFR cannot remain the same. ie The weight of oxygen in a given volume of air at 70 C will be a lot less than the weight of Oxygen at 25C. This is why when you fit an efficient front mount you will have to add fuel across the fuel map from the point where the FMIC comes into play and from actual experience this is what happens.
You do not require a remap on a Standard Car ECU because the manufacturer has already devised a table to take account of varying ambient temperature changes and has test driven the car in both Artic and Tropical conditions to refine that map. At higher temperatures this will include reducing ignition timing and at some points in the map reducing fueling. At low temperatures the car is running richer and this is achieved by monitoring sensors which can include intake air temperature, water temperature and in some cases air charge temperature.
Running at a low ambient temperature is not the same as running with a front mount. The resulting conditions bear little resemblance taking into account engine load, throttle position, RPM, boost and so on and it is therefore possible with a front mount to be driving outside the perameters of the ECU that were previously mapped.

I hope this helps. If you want more on this let me know.

If the FMIC is efficient and doing its job not only should it add safety after a remap but also it will add power if there were a genuine need for the front mount in the first place. By the time you can reduce ACTs by 20C there are compelling reasons to fit an FMIC. Monitoring ACTs before deciding to fit an FMIC is usually a good way to determine you actually need on.
For every 4 deg C ACT reduction your engine will gain around 1% power and over several years this figure has held good on cars I have worked on and mappers can independantly comment on the need for more fuel with a front mount.
More fuel, maintaining the same AFR and boost = more power.

Stealth

iTrader: (4)

Thanks Harvey

I refer to bottlenecks as someone mentioned MORE air getting in, I simply pointing out that more AIR can't fit through the tube than it did before surely ? ANYWAY that is clearly irrelavent! LOL

OK humour me, if the manufacturer tests their engines and setup from hot hot temps all the way down to arctic and then insure the ECU can deal with these temperature ranges why would it no be able to adjust for a FMIC in the UK ?? The ECU has been programmed so that it can deal with the arctic conditions and the UK never gets to Arctic conditions.

Not looking for a fight, or an arguement, just a better understanding, Ta

Splitpin

You're assuming, of course, that Subaru have actually done the above, and got it 100% right to start with. FHI is by no means as big a company as, say, Ford, and thus it is likely that their pre-production prototyping/testing process is less extensive than some manufacturers. The hatch STi engine problem is one obvious example of this type of testing being imperfect.

It can't "adjust" for an FMIC, full stop. It will carry on controlling the engine exactly as it did before the intercooler was changed, and you would have to simply hope that the there is enough safety margin in the management system that the car was still running within a safe performance envelope.

ECUs aren't magical, all-seeing eyes, they are relatively simple digital computers at heart and can only "adjust"/respond in a defined manner based upon a relatively small number of sensors, and within pre-programmed limits.

You're right, even with the caveats above borne in mind, car manufacturers do test their vehicles in a wide range of environmental conditions and usage scenarios. The trouble is that even assuming all of that, when you modify the engine it is relatively easy to set up a performance envelope that is outside anything the manufacturer will have tested for (or equipped its control systems to adapt to).

Obviously enough, your ECU does not have a "decat detector". Doesn't have a "FMIC detector", so it can't magically detect that you've fitted one and respond on that basis. It doesn't have an "induction kit detector" either, so won't automatically spot you've fitted one and change its MAF scaling curve to suit. Standard ECUs don't have the sensors capable of alerting them to the by-products of intercooler changes either, so again, they can't actually respond. All the manufacturer can do under these circumstances is set the management system up in a way that works okay under as wide a range of environmental conditions and usage scenarios as possible.

The Subaru ECUs (on the newages and some classics) do have inlet air temperature sensors and thus can temperature compensate in a number of areas. However the sensors are, depending on model, located either before the airbox or in the MAF sensor housing. As such this sensor is unable to detect reductions in charge air temperature caused by fitting a more efficient intercooler. If it is unable to detect changes in charge temp, the ECU is clearly not going to be able to modify its behaviour in response to a reduction (or increase). It would need a temperature sensor in the throttle body or inlet manifold to do that - which many aftermarket ECUs do implement.

Without a sensor to detect alterations in charge temp, any effective leaning of the mixture would be undetected, unless it was bad enough to cause detonation, in which case you'd have to rely on the closed-loop knock control system to pick it up after the fact, which is the solution Subaru rely on.

That solution works, but it is inherently less desirable than adjusting proactively for temperature variation, and especially given that the knock detection system on the standard Subaru ECUs is by no means perfect.

One of the other aspects of fitting an FMIC, btw, is that you'll get alterations in the boost dynamics caused by the significant increase in induction tract volume between the turbo and cylinders. Again, the ECU can't proactively detect and compensate for that.

The corollary of that is that you don't actually know how well a UK specification Impreza (modified or othewise) will behave if driven in genuinely arctic conditions. If, for example, we were talking about a classic, it would likely overboost quite badly as it wouldn't have any form of air temperature compensation. That gives you one example of the limitations within the engine control systems.

It ultimately doesn't matter how much testing the manufacturer does in standard trim. If you bolt on one modification, you'll alter the function of the engine in one way. If you then bolt on a second, or a third, you're steadily eroding the safety margins mapped into the engine management, especially when the different changes start to interact with and multiply each other.

You get a perfect example of interaction when you fit an FMIC to an otherwise standard car btw. You have no choice but to fit an induction kit, which is likely to throw your MAF sensor scaling (and hence engine load/fuelling/ignition) calculation out, reducing your safety margin by an unknown amount. You fit your FMIC, resulting in a reduction in charge temperature, reducing your safety margin by a further unknown amount. How much, if any margin do you have left? Enough to deal with a bit of decat-induced overboost? Enough to deal with all of the above plus a slightly degraded airflow meter?

The default attitude of most lay people seems to be to assume that engine control units are neural net supercomputers literally capable of doing and responding to anything. Once you know how untrue that is, it is relatively easy to understand their limitations.

The only way the ECU could actually adapt to the range of possible bolt-on mods Impreza owners tend to fit is if it was a far more complex system, fed by a much greater array of sensors, than is the case on any roadcar you are likely to find.

You could, for example, build a management system capable of automatically detecting and recalibrating itself if the owner happened to fit a different set of injectors. The reason you don't see an ECU with that sort of capability on the market right now is primarily due to economics. It makes little sense to include something like that when it will ultimately raise the price of your product - for a feature hardly anyone would use.

The only way to make the control units we find in our cars nowadays control modified engines properly is to reprogram them. Otherwise, as above, you are relying/hoping that any modifications you make are insignificant enough to keep within any safety margins the manufacturer saw fit to include.

jayallen

iTrader: (31)

Ive run 2 imprezas with FMIC with no remap. The first was 5 years ago, a '95 wrx which when on the rollers made 313bhp with supporting mods. The AFR did show up a little on lean side but that was down to the SB ecu which by all accounts ran lean map from Subaru....that car is still running today with the same setup.

My second was my '97 STI RA, originally mapped via a simtec with the topmount. I fitted a FMIC 4 months before i had it remapped with bigger injectors and a different turbo. In those 4 months leading up to it being remapped i drove it hard and never had and issues, including a track day at castle coombe.

A friend of mine has just built a '96 wrx RA on a show string for track use whilst his forged 6speed track RA is off the road for a rebuild. Mods are FMIC, IK, parallel fuel lines, AFPR, TD05 converted to FE, intank walbro feading a swirl pot and a external walbro feading the fuel lines all controlled by a POLAR PERFORMANCE chip. We took it on its first trackday last month and drove it HARD!!! Apart from a slight boost spike....to which we have now sorted with a boost controller....it covered over 250 miles that day AND didnt miss a beat!...160 of those miles were flat out track miles.....The
car is booked in for another trackday nextmonth.

I know quite a few other people who have fitted FMIC's and have not had a remap but that doesnt mean im going against what has been said in this thread by saying a remap is not needed, im just commenting on my findings.....

harvey

iTrader: (48)

Like I said above:

I would rather not sell someone an efficient front mount intercooler than tell them a remap is not necessary. What they do after that is up to them.
Obviously if you fit an inefficient front mount intercooler then you have more chance of getting away with it than if you fit an efficient FMIC. Regardless, there is nothing more sure than the fact that you are not getting the best out of fitting your intercooler without a remap and without atleast checking AFRs across the rev range you may well be courting disaster. It seems obvious to me that those who fit front mounts in the belief that no remap is necessary lack a full understanding of what is happening.
I will try to explain further, later.

harvey

iTrader: (48)

I don't know about humouring you and I am sure you are not looking for a fight but I would like to try to help improve your understanding.
Firstly, you have to come away from the idea of volume of air. We are talking about mass and particularly mass of oxygen. Anything that can be done to encourage increased oxygen mass into the combustion chamber promotes development of power. This can be done by a number of methods including colder air charge, this is the same volume but a greater density and therefore more oxygen mass, the addition of Nitrous Oxide which has more oxygen than does air by weight, in the ratio 14:32 without looking it up or even the addition of water vapour done properly. H2O Ratio 2 Hydrogen:16 Oxygen.
The intercooler is nothing more than a heat exchanger to remove unwanted heat. This gives two great benefits. The reduced charge temperature results in a denser charge in direct proportion to the change in temperature, measured on the absolute scale and I think everybody accepts that a denser charge makes for more power. Secondly, the denser charge is less likely to lead to detonation, all other conditions being maintained.
This means that with efficient intercooling there may be the opportunity to increase boost pressure or increase ignition advance or both.

Do not work on the principle that any intercooler is better than no intercooler because there are some pretty crap intercoolers out there and it is not just temperature reduction you are looking at but also pressure drop across the core. With a pressure drop of 5 psi to produce 20 psi boost in the inlet manifold the turbo is working at 25 psi. Now with 2.5 psi pressure drop the turbo is working at 22.5 psi to achieve the same result. Less load on the turbo = less heat. This is a good thing.

Now Splitpin has already outlined that the boost dynamics will be different on a front mount intercooler system than on a TMIC system. Changing from one top mount to another will also change the boost dynamics and as Splitpin has pointed out there is a limit to the changes the ECU can handle or the range across which it can work.
Now the ECU can handle the changes from operating at -5 C to +30 C but it does not do it very well, in some cases, at the extremeties of that range and in any case the ambient temperature has only a small effect on the air charge temperature. The biggest effect on the air charge temperature is the ability of the intercooler. The manufacturer can conduct tests between say -5C and +30C and map the ECU within these parameters to deal with fuelling and ignition timing and reach a compromise situation. Now because ambient temperature has little effect on ACTs it is actually the ACTs the manufacturer is interested in and on a Classic top mount these might vary from 15C over ambient on light use to 60+ C over ambient on hard use subject to the turbo and TMIC design on that particular model.
Remember that the TMIC sits on top of the engine and is therefore influenced by engine bay heat, over time, so even without static heat soak the TMIC will be an interwarmer in some conditions.
Now fit an efficient front mount intercooler. The ACT might vary from 4C over ambient to 15C over ambient. Now, obviously if the ECU is mapped to handle air at 60C over ambient on WOT but now has air at 15C over, more fuel is needed for that denser charge to compensate and bring AFRs back to an acceptable level. The ECU has not yet reached a level to pull ignition because it is now in an area it is not mapped for. The ECU does not have adequate range, why should it? It is not designed to operate in these conditions and a manufacturer is not going to spend time designing an ECU to accomodate more than the basic range of operating perameters than necessary.
HTH.
Monitoring air charge temperatures can be very revealing.

Tazman861

iTrader: (2)

Loads of great info on here but my main reason for asking was that I wanted to ensure the IC was fitted and all joints sealed with no leaks and no funny sounds!! As I originally said its having a remap in a couple of weeks.

Anyway I have driven it and it all seems OK . The car still boosts to 16psi and there are no odd sounds. the engine does seem it have a different note on idle but I believe that is because there are new pipes touching parts that were previously on there own. The DV does however make a totally differnt sound - I think it sounds better but that is just my opinion!!

harvey

iTrader: (48)

Tazman: Your first question.
Driving the car on light throttle and mild boost and you will be OK. This does not mean you have to drive at low speed but it means you have to keep load of the engine.

Second question:
Yes, correct again. Melting a piston or nipping a piston in the bore is indeed a possibility if you have fitted an efficient FMIC system for the reasons explained above.

boosts to 16psi. This is not off boost and certainly not light throttle and mild boost but hey it's your engine and you might be lucky. Quite unbelievable considering your first post.

Effort was put in to giving the explanation above both by Splitpin and myself to assist Stealth in his understanding. We thought you had taken on board what we said.

Stealth

iTrader: (4)

Ahhh haaaa it all makes sense now, Thanks to Both Harvey and Splitpin, I am now considering myself schooled

Thanks chaps !

ginger321

Surely a remap would be the best thing to get the full benefit from your FMIC? Make sure your pride an joy is sweet as a nut!

daveturbo

classic wrx, k&n,z4,autobahn fmic,decat,stainless system, with these mods mine is over fueling to death, but cant afford my remap for a while, im only taking it round the block at the moment to keep use down, but as said above the majority would underfuel i think most of you said, mine is over fueling so any ideas whats goin on there?

it drives fine and that but just wondering maybe my car has adjusted too well maybe to the mods as in progressive learning from maf and the like?

many thanks dave