Power Fc V's Microtech LTX-12

[lwells]

What sort of cost are the Microtechs for install, and what about for a tune?

Cheers,

LW.

[Sydneykid]

Hi Guys, let me throw this one at you. Power FC's use AFM's and when the air temperature rises the air density decreases. The AFM senses this lower density and the ECU compensates for it. MAP sensors read pressure and thus have no idea about air temperature. So it is logical that an ECU that relies on a MAP sensor would need a air temperature sensor as well.

So the fact that the GTST Power FC has the capacity to use an AFM can in many ways be more beneficial than an ECU that uses a MAP sensor. Remember that Nissan didn't think a GTST needed an air temperature sensor, and the cars run millions of K's in all sorts of temperatures from way below zero to over 50 degrees. Maybe that's why they went for the more expensive solution of AFM's over MAP'S, they are better at a wider range of conditions.

My opinion would be that ECU's with MAP sensors have a deficiency in not having built in air temperature correction sensing and thus their manufacturers have to use a separate air temp sensor to overcome this deficiency.

This is why in Steve's case, he (and many thousands of others) has not had a problem. Plus Nissan saw fit to use a dash board warning light to alert the driver to problems. I simply don't see the use of an ECU that rips timing out or adds fuel when the sensors get outside its mapped parameters. Do these corrections stay there permanently? ie; when you start the car the next time, is it still retarded and rich? If it is, how do know it? The car feels slow and sluggish, but I don't know why. I have to take it to the tuner to find out why.

Or when you turn the ignition off does it return to its tuned program? Only to then go to its retarded and rich mode next time whenever what caused it happens again. Sometimes the car feels sluggish and sometimes it doesn't? I don't know that there is anything wrong or even worse, I book it in to get it checked and they can't find anything wrong with it. Because whatever caused it doesn’t re-occur on the dyno or in short distance drive around the local streets.

The reality for me is I would much rather have an ECU that compensates for the largest possible range of occurrences and has wide enough mapping to handle these circumstances. If there is a problem the dashboard light tells me and, if it’s really bad, the ECU goes into limp home mode. Now this is a more expensive proposition for the ECU manufacturer, more processing power, more load points and larger maps. It is much cheaper to scrimp on these and add a cheap bit of software that compensates for this lack of capacity by whacking in some more fuel and retarding the ignition

In conclusion, do the more expensive ECU's like Motec, Autronic, Motronic, Marrelli have this? They spend the money on more processing power, more load points and wider parameters. If the engine gets outside these wide parameters then, for example, the Motec shuts it off completely. Logically this is the better approach, as, if the engine is so far out, it needs to be shut down, right now. You can then download the data and look for what is wrong and fix it, much like the dashboard warning light.

Now, having given my personal opinion, I'll just sit back, and wait for the responses.................

[Jimbo2000]

"I don't know everything"

:bs!:

[Roy]

My biggest problem with the Power FC is availiability for the RB20.

That and i find it hard to justify the expense of an aftermarket computer that doesnt allow me to store and quickly change MAPs, say street driving on 95RON and 0.65bar, then an alternative tune for VP/or 98RON-toluene mix for the track and 1.3bar.

At this minute if i had to buy an aftermarket ECU it would be Autronic SMC. At under 3k installed and tuned it isnt that more expensive by the time you buy the PFc & Z32/Q45 AFM and have it tuned.

[B-Man]

Hi Sydneykid,

How does the AFM detect oxygen density in the air, based on temperature - when, as I understand it, the AFM measures air flow.

[Steve]

it uses a hot wire, that measure a change in the flow of an electrical current as air passes it. Denser (cooler) air will have a greater effect than thinner (hotter) air, at a guess:)

having said that, its interesting that my detonation is actually lower during hot days than cold ones, I am thinking the the car is running a bit richer - but this may alos be because of the afm being beyond its peak flow voltage, and the ecu cannot tell the difference.

B-man, want to sell your bodgey Power fc frying Q45 AFM? pm me if interested

[Sydneykid]

Hi Roy, I paid less than $1,500 for an RB20DET Power FC, Commander and Q45 AFM. It cost $250 in my time to tune it at the normal dyno hourly charge out rate. But I shopped around for a few months, had cash ready and jumped within 1 hour of the adds going up on the forum, they sell quick.

That said, if I hadn't found it I would have chipped my standard R32 ECU, for around $700 inc dyno time, it was a pretty good alternative. Each upgrade and retune would be around $200. I had about 5 steps, planned. So $700 + ($200 X 5) = $1700 which was more than the Power FC and bits, so I went that way. But if you only had 1 or 2 steps in your power up plan then it is well worthy of consideration.

Moving on to the two set ups (1.3 bar & VP versus 0.65 bar & 98). Well I don't really see a problem with using a PFC. You set up the boost correction table appropriately, at 0.65 bar you have the correction set for 98 octane and at 1.3 bar you set the correction for VP. I would tune the car for 1.3 and VP first, then drain the tank, limit the boost to 0.65 bar and then apply the necessary correction at that point on the boost table. When you are running 1.3 bar, the engine will rip thought the 0.65 boost point so fast it won't matter that it is not optimal for VP.

There is no problem with doing this other than it won't be a perfect tune for 0.65 bar, if you had individual maps you could get it a bit better. But let's face it, you obviously don't care about the last 5% of performance at 0.65 bar otherwise you would run 1.3 bar all the time.

We do have Datalogit for the GTR's which allow uploading of different maps to the PFC, but we simply never use it. It is good to have the lap top programming and access to those parameters that the Commander doesn't let you. Plus we use the data logging all the time. I wouldn't buy a Datalogit system just so I could run 2 sets of maps, it simply isn't good value or really necessary anyway.

Hope that clarifies some more

[Abo Bob]

Hi Guys, let me throw this one at you.  Power FC's use AFM's and when the air temperature rises the air density decreases.  The AFM senses this lower density and the ECU compensates for it.  MAP sensors read pressure and thus have no idea about air temperature.  So it is logical that an ECU that relies on a MAP sensor would need a air temperature sensor as well.

..

If the air temperature in a given space increases, the air density can't decrease unless some of it is removed, right? So if the air isn't removed, isn't the pressure increased? If so, a MAP sensor does have some idea about temperature, albeit a second hand idea.

My modern car knowledge is sparse and I'm trying to bring back some high school physics for this one so shoot me gently if I've got this all wrong.

[Abo Bob]

How slow does my brain work!? I think about 5 posts walked in there while I was cogitating!

[RNS11Z]

Well my R33 had the Microtech Mt8. I have it running at 320rwkw currently. Only problem i had with it was Idling (apparently i needed a tps switch) and my computer would lose rev signal. Other then that the car ran perfectly.

[Steve]

If the air temperature in a given space increases, the air density can't decrease unless some of it is removed, right?  So if the air isn't removed, isn't the pressure increased?  If so, a MAP sensor does have some idea about temperature, albeit a second hand idea....

not really relevant, the air density varies before it hits the AFM, warmer air will have molecules further spaced apart.

If you compress 50 litres of air (at sea level, so 1 bar absolute pressure) with an ambient temperature of say 40degrees celcius to 1.5bar, it will have less mass than 50 litres of air (at sea level...) at 15degrees compressed to 1.5bar -

What SK is saying (if I am right) is that a map sensor will only see the 1.5 bar, and therefore wouldnt be able to discriminate between the differing air densities, and this is why they use air temp correction in alot of cases.

[B-Man]

OK - This AFM thing has got me thinking.... - If the AFM was an oxygen density sensor, I would agree with Sydneykid - but it essentially measures air flow based on a drop in temperature accross a hotwire - yes/no ??? Hence ambient temperature plays a part in it's effectiveness to calculate correct flow data for the ECU - Unless the ECU has an ambient temperature sensor and compensating map.

Forgive me if I have missed to point completely.....

[Steve]

cooler air is more dense, the hotwire senses the amount of air that passes it - if the air is denser, wouldnt it result in more air passing the sensor for the same given velocity?

This probably wouldnt be a huge amount, but cooler air would take more heat out of a hotwire sensor, thereby showing greater flow.

[Roy]

Hi Roy, I paid less than $1,500 for an RB20DET Power FC, Commander and Q45 AFM.  It cost $250 in my time to tune it at the normal dyno hourly charge out rate.  But I shopped around for a few months, had cash ready and jumped within 1 hour of the adds going up on the forum, they sell quick.

That said, if I hadn't found it I would have chipped my standard R32 ECU, for around $700 inc dyno time, it was a pretty good alternative.  Each upgrade and retune would be around $200.  I had about 5 steps, planned.  So $700 + ($200 X 5) =  $1700 which was more than the Power FC and bits, so I went that way.  But if you only had 1 or 2 steps in your power up plan then it is well worthy of consideration.

Moving on to the two set ups (1.3 bar & VP versus 0.65 bar & 98).  Well I don't really see a problem with using a PFC.  You set up the boost correction table appropriately, at 0.65 bar you have the correction set for 98 octane and at 1.3 bar you set the correction for VP.  I would tune the car for 1.3 and VP first, then drain the tank, limit the boost to 0.65 bar and then apply the necessary correction at that point on the boost table.   When you are running 1.3 bar, the engine will rip thought the 0.65 boost point so fast it won't matter that it is not optimal for VP.

There is no problem with doing this other than it won't be a perfect tune for 0.65 bar, if you had individual maps you could get it a bit better.  But let's face it, you obviously don't care about the last 5% of performance at 0.65 bar otherwise you would run 1.3 bar all the time.

We do have Datalogit for the GTR's which allow uploading of different maps to the PFC, but we simply never use it.  It is good to have the lap top programming and access to those parameters that the Commander doesn't let you.  Plus we use the data logging all the time.  I wouldn't buy a Datalogit system just so I could run 2 sets of maps, it simply isn't good value or really necessary anyway.

Hope that clarifies some more

Didnt relaise that you could use the boost correction table to get the desired result i was looking for.

I did get myself a Pfc for my car, but it had a fault when it was bench tested prior to delvery (2nd hand) Since then ppl seem to be asking a premium for them due to availiabilty, about $1800 was the last one i saw.

But for my sutuation...

As for re-tuning std ECU, thats what i have at the moment. Its running different AFM and bigger injectors and a bigger turbo. Seems to be doing a good enough job for the time being, but i suspect its not ideal.

But as well as running different MAPS for different fuels/boost im looking at rebuilding my engine, in which case my exisitng ECU will be no good, and my current big turbo wont be so big anymore.

And since a Trust T67 is a bolt on upgrade for my setup, i like the idea of T67 on for things like Drag and Phillip Island/Eastern Creek (im working between Syd/Melb now) and the smaller TD06-20g for street, rallies and tight circuits like Winton and Wakefield. To do this i suppose i could have two remapped ECUs but id prefer to have something like an Autronic.

My big problem is my plans are always changing due to work commitments,

[B-Man]

cooler air is more dense, the hotwire senses the amount of air that passes it - if the air is denser, wouldnt it result in more air passing the sensor for the same given velocity?

This probably wouldnt be a huge amount, but cooler air would take more heat out of a hotwire sensor, thereby showing greater flow.

Cooler air is more dense with O2 molecules. But 'air' flow (air velocity) would be the same would it not ? Hence why I'm thinking the AFM should be called an O2 density sensor.

More air velocity also results in more dense O2 saturation.

Oh bugger it - I'm getting myself confused now.....

I think I am splitting hairs......

[Steve]

its all good - I am being somewhat hypothetical, perhaps I should just do the big handball back to sydneykid and ask him to explain why???

SK??

(BTW B-Man, where are your dyno results?????)

[GTRgeoff]

Atmosphere is ~70% nitrogen and 28% oxygen and the rest hydrogen and everything else. This doesn't change, but the densities can change due to barometric and temperature variations.

Hot wire anemometers usually maintain a constant temperature, and when the air is cooler it increases voltage to maintain the same temperature, allowing the ECU to modify the fuel and timing to compensate giving more power. Likewise for hotter air it will reduce fuel and timing advance resulting in less power. But the temperature is not everything....the mass flow of air at any temperature is what is required to elicit the change, so for a given temp at sea level, the same temp at altitude would have a differing effect.

Ultimately a Hot wire will in one unit give a huge number of influencing parameters input in the computer that cannot be offered by MAP without temp.

Hope this clarifies a little

[B-Man]

(BTW B-Man, where are your dyno results?????)

Coming coming - Clutch being replaced as I lunched it at the drags (too much power) - also final tune this week - after that new dyno run and I will post results. Lets just say, I have a BIG smile on my dial......

[B-Man]

The AFM takes it's measurement before the air goes through the turbo and intercooler - so what dynamics does this play on what temperature the air is when it actually goes into the head anyway ?

I could have no intercooler at all and the AFM is still going to tell the ECU the same thing.

So what is the real benefit of the AFM ?

I know, I know, I am prolly missing something.........

[GTRgeoff]

If you change the intercooler the effect is hotter or colder charge air depending on which way you go. You know the limitations of the computer can be exceeded even though it has a knock sensor so you could assist or kill the engine. There is no perfect solution without good tuning using knock sensing amplifiers but the hot wire afm is the current ideal solution AFAIKfor everyday and power. If you just want horsies, go MAP for the lack of restriction I suppose.