Heheheh cant resist a dirty sounding title.

Friend of mine who is relatively knowledgeable about cars, not a talking out his ass type moron and I were talking about my car yesterday and I told him i had thought about putting a 1GG supercharger on and keeping it at low boost (about 5psi) but after having to buy a unichip and all that it might just be cheaper to do the DOHC conversion.

He said "With a supercharger at low boost, you probably wont need to get a piggyback ecu, your computer should be able to adjust to the changes"

Now normaly id dismiss this as bull****, but he isnt an idiot so i thought id ask.

Is he right or wrong?

Heheheh cant resist a dirty sounding title.

Friend of mine who is relatively knowledgeable about cars, not a talking out his ass type moron and I were talking about my car yesterday and I told him i had thought about putting a 1GG supercharger on and keeping it at low boost (about 5psi) but after having to buy a unichip and all that it might just be cheaper to do the DOHC conversion.

He said "With a supercharger at low boost, you probably wont need to get a piggyback ecu, your computer should be able to adjust to the changes"

Now normaly id dismiss this as bull****, but he isnt an idiot so i thought id ask.

Is he right or wrong?

It all depends on the ECU setup and programming. The 2nd gen V6 would take advantage of higher octane fuel (by adjusting timing) and using a knock sensor to trim back the timing in the event of detonation. So yes it could do some small self adjustments, but it can only do so within it's programed limits. These limits are generally to small for the differeace even a low boost application would make.

It might run in the end AND produce more power, but it will be far from running efficienttly. Good example is the EL ECU's. They can adapt to some fairlly aggressive cams (for street applications) without needing external tuning, and they will happilly run with the cams, but they arn't running at optimum, and external tuning always nets better gains and efficiency.

ha ha i only clicked on this thread coz of the title

I'd be surprised if it worked as well as your friend indicates. I'd want to plumb in a wide band oxygen sensor to monitor air/fuel ratios in any case.

ha ha i only clicked on this thread coz of the title


Haha me too..:P


Ok, Now ill go..:P

Not gonna work with factory ECU.

The MAF will not know about the extra air and the ECU will not get the mixture right.

Damn is this about an engine :doubt:
hey will we get banned if we start dirty threads :dancin:
just curious :redface:
dee

TL-R wrote:
Not gonna work with factory ECU.

The MAF will not know about the extra air and the ECU will not get the mixture right.

Where is the engine going to get the extra air from.
There is only one hole in and the MAF reads all that air.

I've been told VERY RELIABLY that the stock ECU can deal with 'several' psi of positive head. (please don't ban me for that pun :pray: )

Good to see the AMC chicks are good sports, hey Dee!

And what's gonna compress the air (ie changing the air/fuel ratio) which is AFTER the MAF.

Think about it.

Good to see the AMC chicks are good sports, hey Dee!

:eh: ......awesome :D

It all depends on the ECU setup and programming. The 2nd gen V6 would take advantage of higher octane fuel (by adjusting timing) and using a knock sensor to trim back the timing in the event of detonation. So yes it could do some small self adjustments, but it can only do so within it's programed limits. These limits are generally to small for the differeace even a low boost application would make.

It might run in the end AND produce more power, but it will be far from running efficienttly. Good example is the EL ECU's. They can adapt to some fairlly aggressive cams (for street applications) without needing external tuning, and they will happilly run with the cams, but they arn't running at optimum, and external tuning always nets better gains and efficiency.
undefinedundefined Read your script about supercharger boost a fellow fitted one and got minimal performance gains for his dollars so he had it back in the shop for turbo fitout and is blowing em away in dandenong
keep cruising xi :cool:

And what's gonna compress the air (ie changing the air/fuel ratio) which is AFTER the MAF.

Think about it.

You say some funny things sometimes, A boost reading is pressure above atmospheric.
The engine still consumes it's normal amount and the supercharger supplies it with an excess of air, so much so that it creates pressure in the intake. The supercharger doesn't compress just the air that would have normally entered the intake it doubles or even triples the air the engine flows, thats where the boost comes from. All this air supplied is drawn through the MAF, or if you change the ecu through a MAP sensor or once again, through a carby. An ecu doesn't need to read boost if it measures Mass Air Flow, this will tell it the engine is consuming huge amounts of air and will fuel accordingly up to it's sensor limits.

Matthius

But the MAF is sensing air at regular air pressure and NOT the compressed air pressure. Although it is sensing the amount of air, it is assuming it's a regular air pressure and NOT the compressed for it will be inside the cylinder.

But the MAF is sensing air at regular air pressure and NOT the compressed air pressure. Although it is sensing the amount of air, it is assuming it's a regular air pressure and NOT the compressed for it will be inside the cylinder.


For fuel adjustments that doesn't matter, because to gather the extra air TO compress it the supercharger must draw it through the MAF. If the engine consumes X air, it needs X fuel to achieve X air/fuel ratio, all air entering the engine is metered unless you have a vacuum leak and the MAF/ECU will account for it to the end of it's abilities, limited as they may be. Otherwise carbies couldn't be superchared as they wouldnt have a clue if the intake was under pressure or vacuum.

Matthius

yes you will get banned for starting dirty threads, i found out the hard way :cry:

but i'm all good now :cool: i've learnt my lesson,

as for the supercharger, why run it low anyway? wouldn't you want to take advantage of the forced induction?

as for the supercharger, why run it low anyway? wouldn't you want to take advantage of the forced induction?Low pressure is cheaper to set up. Otherwise you have to decompress the motor and/or run stronger pistons and rods.

But the MAF is sensing air at regular air pressure and NOT the compressed air pressure. Although it is sensing the amount of air, it is assuming it's a regular air pressure and NOT the compressed for it will be inside the cylinder.
All it cares about is the mass of the air going through, not what happens to it afterwards including whether it's gone from 1 atmosphere to 1 bar.

^You are right - the MAF sensor won't care but my point is the Air/Fuel ratio for compressed air is different to that of atmospheric pressure air.

^You are right - the MAF sensor won't care but my point is the Air/Fuel ratio for compressed air is different to that of atmospheric pressure air.Not it isn't. The Air/Fuel ratio is the same. 14.7 parts of air to 1 part of fuel for stoichiometric. So long as the MAF knows the engine has consumed 4L (or whatever) of air it can work out how much fuel to supply. The trick is going to be finding out what the ceiling is for the MAF and establishing if there is enough head room to cope with the extra load.

as for the supercharger, why run it low anyway? wouldn't you want to take advantage of the forced induction?


Several reasons.

1. Its a 1GG supercharger and originaly off a 2L. I wouldnt want to try and run high boost untill I find some information about how much air they can pump. Nobody can give me any and I cant find any.

2. I have a 10:1 compression ratio, anything more than a few psi will so me blasting a head gasket

3. Its primarily the getting it fiting exercise. 1 or 2 psi would make me happy aslong as it wouldnt damage my engine.

Im actualy keen on running a natmo setup myself. But id like to see if i could make a kit for supercharged 2nd gens in the future. so im curious.

Physics 101

http://www.msc-smc.ec.gc.ca/education/msi/m1/multimedia/m1-010.jpg

Image number 2 is what the MAF/ECU THINKS is going into the cylinder.

Image number 1 is what is ACTUALLY going into the cylinder. There are more molecules in compressed air and therefore the A/F ratio will not be correct.

If you don't understand that then i give up.

Then the role of the O2 sensor comes into play. It is used to correct the fueling despite metered air inputs.

Just try it! It if doesn't work, unbolt it!

If a normal engine sucks in a certain amount of air in N/A form and the S/C motor sucks twice the amount of air in then the N/A motor then the MAF will read this and the computer will compensate for this as long as it is within its limits. E.g bolting a 1000hp turbo to your motor and running it at 6psi with a standard ECU is out of its limits.
Sorry dude if you dont get the concept by now you never will.

The AMOUNT of air is NOT the issue - it's the DENSITY!!!!!!!!!!!

BAAAAAAAAAAAAAAHHHH.

The AMOUNT of air is NOT the issue - it's the DENSITY!!!!!!!!!!!

BAAAAAAAAAAAAAAHHHH.

The amount of air is the issue thats the whole point - it doesnt matter what pressure it's at in the combustion chamber because it gets compressed to 10:1 anyway, does the MAF account for that ? Every engine has air under pressure in the combustion chamber, it's only a matter of how much and when, all the ECU "needs" to know is how much air the engine is consuming and accordingly supply fuel.

Matthius

The density of the air is important - the computer uses two sensors to determine this.

MAF - Mass Air Flow
IAT - Intake Air Temperature

If you run both of these sensors correctly, then you wont have issues with the computer.

The computer uses these sensors to work out the VOLUME of air ingested.

If you ran a 14.7 psi boost turbo, and mounted the MAF and IAT on the intake side of the turbo (pre-turbo), then it would register TWICE the airflow as opposed to when the turbo wasn't fitted and the same temperature. (14.7psi being atmospheric pressure, you are consuming 2X the air volume (atmospheric) to make this, ignoring losses) - At these drastic levels, the computer has no information in its maps (at this intake temp, airflow and RPM) so it gives up, and causes a limp-home mode.

A MAF on a pressurised side of a turbo or supercharger is a bad idea - MAF works by assuming the pressure is 14.7 psi (ie. atmospheric) and works things out from there.

Within the levels of sensibility, our computers can cope with a marginal increase in airflow - there is some room in the maps. Running a non-intercooled supercharger, you would want to make sure that the intake temps are monitored carefully as well.

Cheers
Heath Young

The density of the air is important - the computer uses two sensors to determine this.

MAF - Mass Air Flow
IAT - Intake Air Temperature



The density of air entering the MAF can be important but you can compress it after that all you want as far as fueling goes, obviously component strength/detonation and pressurised air temps will limit possible compression. The magnas run an IAT but not all systems do, the O2 sensor can do what a IAT does just with a slight delay, as the air/fuel has to pass through the motor first

Matthius

The computer uses these sensors to work out the VOLUME of air ingested.
Err... mass.

If u gonna turbo/supercharge a N/A engine put bigger injectors in it and retard the timing. A mate of mine got an import 323turbo engine and but the turbo manifold and turbo on his astina. At first it was leaning out and pinging badly so he put bigger injectors in off the turbo engine.

If u dont get the bigger injector part, your putting a lot more air in the engine than it's programmed to take, if u run to much boost ur gonna lean out, if u put bigger injectors they will open for the same time as the org ones but since being bigger there is more fuel being injected.

Retard the timing to stop pinging with high compression, of course you will loose power untill it's tuned properly but u wont put a hole in a cylinder.

Physics 101

http://www.msc-smc.ec.gc.ca/education/msi/m1/multimedia/m1-010.jpg

Image number 2 is what the MAF/ECU THINKS is going into the cylinder.

Image number 1 is what is ACTUALLY going into the cylinder. There are more molecules in compressed air and therefore the A/F ratio will not be correct.

If you don't understand that then i give up.

You should have given up about 5 posts ago. Thats when you started to embarass yourself. Wether the air is compressed or not........ it all get drawn thru the MAF sensor, and therefore the ECU knows how much is going into each cylinder every time the intake valves open........ it also knows the volume of each cylinder, and therefore....... would determine that there is greater than 1 atmosphere of pressure. This point is irrelevant - like everyone else has said....... the ECU has already compensated for the extra air which has passed thru the MAF sensor, by providing the correct volume of fuel to maintain the correct AFR for the specific revs / throttle position.

The original poster of this thread asked wether or not the stock ECU would be able to comphensate for xPSI of intake air........ I would have thought not.... but EZ boy referenced a relaible source in an earlier post claiming that it would....... I tend to believe what he says.

it also knows the volume of each cylinder, and therefore....... would determine that there is greater than 1 atmosphere of pressure.

How did you figure that?

What has the VOLUME of air got to do with the DENSITY? In my picture above the air voulume is exactly the same but it's the DENSITY that is the difference which the ECU will NOT be able to handle.


I agree that the ECU will know what the MASS of the air is but will assume it is at regular density and not the density which is caused by compression.

How did you figure that?

What has the VOLUME of air got to do with the DENSITY? In my picture above the air voulume is exactly the same but it's the DENSITY that is the difference which the ECU will NOT be able to handle.
I agree that the ECU will know what the MASS of the air is but will assume it is at regular density and not the density which is caused by compression.

What people are trying to say is the density of the air once past the MAF sensor DOES NOT MATTER. The volume will not be the same, it will be completely different once supercharged, for EG: 4 cubic feet of air enters the MAF(random number), the ecu decides to supply x fuel, the air is compressed to 3 cubic feet by the s/c, thus being more dense, but not changing the amount of air that the ECU needs to compensate for.

Matthius

How did you figure that?

What has the VOLUME of air got to do with the DENSITY? In my picture above the air voulume is exactly the same but it's the DENSITY that is the difference which the ECU will NOT be able to handle.


I agree that the ECU will know what the MASS of the air is but will assume it is at regular density and not the density which is caused by compression.

DENSITY = MASS x VOLUME

In an experament involving a sealed plastic syringe containing a set volume of air....... as the plunger in the syringe is pushed down, the volume decreases, and density increases.

Conversly - in the example of a supercharged engine, the volume of the engine is constant, but as the volume of air forced into the engine increases (caused by a mechanical compressor, AKA a supercharger) - the mass also increases.

You even hit on the exact concept in this sentence:

In my picture above the air voulume is exactly the same but it's the DENSITY that is the difference

Yes..... Volume is the same in both boxes, and yes the Density is higher in box number 1. The Density is higher because the Mass of air (not the volume) is greater. Mass of air is what is measured by the MAF sensor.......

Lets for argument sake say that the ECU needs to know the density of the air to properly run the vehicle, okay??

The ECU knows the VOLUME of the engine, and it knows the MASS of air which has flowed past the MAF sensor.......... then the DENSITY can be calculated by multipying the VOLUME (constant) by the MASS (variable) of inducted air.

What people are trying to say is the density of the air once past the MAF sensor DOES NOT MATTER. The volume will not be the same, it will be completely different once supercharged, for EG: 4 cubic feet of air enters the MAF(random number), the ecu decides to supply x fuel, the air is compressed to 3 cubic feet by the s/c, thus being more dense, but not changing the amount of air that the ECU needs to compensate for.

Matthius


You said exactly what i was trying to word but couldnt.

lol i should of read this thread earlia

its no different to a cai

cold air is densor

you can bolt a turbo on to a efi with out probs s/c no different

The ECU knows the VOLUME of the engine, and it knows the MASS of air which has flowed past the MAF sensor.......... then the DENSITY can be calculated by multipying the VOLUME (constant) by the MASS (variable) of inducted air.
Sort of, except in this case it doesn't need to know the density but it might read the density based on temperature to reach this value. All the ECU cares about is the mass of the air and it's this figure which it matches the alotment of fuel too. Whether the mass of the air is in a cubic inch, cubic mile or a 3.5l block doesn't matter.