Questions: Autronic setup being configured for 210hp 2615cc

Duc · Post by **Duc** » Sun Apr 21, 2002 11:34 pm

<BLOCKQUOTE>quote:<HR>Originally posted by Shad Laws:

Most (all?) aftermarket FI systems use MAP only. Mass airflow sensors are quite nice, but pricey and difficult to setup. Since we don't need the absolute perfection of 2002 smog laws, a true 3D map derived from MAP and RPM does great.

True for our setups it may not be needed, but if you want that last smidgeon of performance out you do need it. MAP cannot give an accurate airflow reading alone, esp. in non-steady state situations.



Using TPS as the primary means of airflow measurement is very inaccurate. It's one of the big downfalls of CB's system. No compensation for pressure, for one... also, when your air filter gets dirty, your mixture changes. Just about everything effects it...


I wish they were a little more open about that issue.

Most good aftermarket FI do have temperature. However, AFAIK, there is no system OEM or aftermarket that can bring into account humidity. Please do correct me if I'm wrong as it's a question I've been pondering for awhile!

I actually don't know of any too many systems that actually measure incoming air temps. Yes they have engine temps, which can be used as a starting point, but what about long term?

The problem is this: for our purposes, atmospheric air can be roughly divided into two parts: regular, dry, combustible air and water vapor. The more humid it is, the larger the latter portion is. MAP sensors have no problem with elevation or barometric differences, but cannot sense the partial pressure due to humidity, which should be subtracted from the overall pressure to determine the actual dry, combustible air. So, all other things equal, on a humid day, you run rich. Of course, in closed-loop mode, the O2 sensor can compensate, but that's the only way I know of to compensate for humidity...


Actually I forgot, baro changes, while running, can only be measured with a secondary preasure sensor. Granted unless you are racing in the hills you will never use it.

Yes, that is true, closed loop is the way they compensate. I am sure someone has a method to measure humidity.

Heck with some of the stuff they race with they probably measure the heart rate of the drivers (I know they do that for medical in F1), and slow the car down when his heart stops!!!

D

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Shad Laws · Post by **Shad Laws** » Mon Apr 22, 2002 1:55 am

Hello-

True for our setups it may not be needed, but if you want that last smidgeon of performance out you do need it. MAP cannot give an accurate airflow reading alone, esp. in non-steady state situations.

It needs compensating sensors (like air temp!) to do it right.

Perhaps the biggest "problem" with MAP is that there is not a direct correspondence. For example, a MAF tells you directly how much air is going in. MAP requires fuel maps to be built. If the engine configuration changes, so must the maps.

I wish they were a little more open about that issue.

As well as many others... *sigh*. Once you're done paying for the t-body(ies), the pump, the pressure regulator, making the manifolds, fuel lines, rails, setting up injectors, wiring, etc. it seems silly to me to skimp on the ECU itself. Ah, well.

I actually don't know of any too many systems that actually measure incoming air temps. Yes they have engine temps, which can be used as a starting point, but what about long term?

The Autronic, at least, does have an intake air temperature sensor. It also has a coolant temperature sensor (oil temp works well... basically tells you if you're warmed up). Then, it has something called "Charge Temperature". This is used in the actual calculation of the air density. Here's the cool part: they let you determine the relationship between the three! For example, if you think that the intake air temp sensor is representative of the temperature directly at the pressure line, then make charge equal to the intake air temp. But, if you think it heats up a bit due to the warm engine (you can measure this with a couple temp. probes), you can tell it how much of the "coolant temp" to use to bump up the charge temp. And, you can change this relationship depending on RPM and MAP... VERY clean.

Stock D-Jet has intake air temp, too.

I'm not very well versed in other aftermarket FI systems... do most of them really lack intake air temp?

Actually I forgot, baro changes, while running, can only be measured with a secondary preasure sensor. Granted unless you are racing in the hills you will never use it.

MAP stands for "Manifold Absolute Pressure." It measures the absolute pressure of the manifold (i.e. relative to a perfect vacuum), not the pressure relative to the atmosphere. Therefore, barometric changes have absolutely no bearing on MAP-controlled FI systems. If the barometric pressure drops, it just thinks you're running at a lower load and compensates accordingly without even thinking about it. MAF works the same way, since the density of air drops, it just thinks less air mass is going into the engine and compensates automatically. However, while immune to barometric changes, they aren't immune to humidity changes. In fact, I'd think that MAF would be more screwed up than MAP due to specific heat differences...

Yes, that is true, closed loop is the way they compensate. I am sure someone has a method to measure humidity.

Heck with some of the stuff they race with they probably measure the heart rate of the drivers (I know they do that for medical in F1), and slow the car down when his heart stops!!!

Aye, true!

Take care,

------------------
Shad Laws
LN Engineering
http://www.lnengineering.com

Post by **Tom Notch** » Mon Apr 22, 2002 6:59 am

Haltech also has intake air temp input along with coolant temp, with adjustable correction maps for both.

I get my new Mallory vacumn advance equipped dizzy and will install it this week. Now I'll be switching my Haltech F9a system in my Notch over to MAP from TPS. Just have to hook up the vacumn line to the MAP sensor and start programming , AGAIN!

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Tom Notch
Tom's Old VW Home

Duc · Post by **Duc** » Tue Apr 23, 2002 12:06 am

<BLOCKQUOTE>quote:<HR>Originally posted by Shad Laws:
Hello-

Perhaps the biggest "problem" with MAP is that there is not a direct correspondence. For example, a MAF tells you directly how much air is going in. MAP requires fuel maps to be built. If the engine configuration changes, so must the maps.


Ok, MAF gives you reference to the air flowing into the throttle, MAP gives you the air preasure in the throtle body past the throtle plate. The formulae for calculating the Air Mass flowing into the cylinder, is based off of both; not the measured air flowing into the thortle given by the MAF.

Yes, any changes to any engine needs the fuel and ignition maps adjusted.



The Autronic, at least, does have an intake air temperature sensor. It also has a coolant temperature sensor (oil temp works well... basically tells you if you're warmed up). Then, it has something called "Charge Temperature". This is used in the actual calculation of the air density. Here's the cool part: they let you determine the relationship between the three! For example, if you think that the intake air temp sensor is representative of the temperature directly at the pressure line, then make charge equal to the intake air temp. But, if you think it heats up a bit due to the warm engine (you can measure this with a couple temp. probes), you can tell it how much of the "coolant temp" to use to bump up the charge temp. And, you can change this relationship depending on RPM and MAP... VERY clean.


Nice. Should have gotten an Autronic.


Stock D-Jet has intake air temp, too.

I'm not very well versed in other aftermarket FI systems... do most of them really lack intake air temp?


Don't know. I took some notes on all of the Aftermarket setups I could find. Some were better than others. I actually have the Autronic listed with out air temp sensor capability. Though this is based off what they have on the website.

Well I will be getting a real good education soon, going to be paid to work on an ECU!

Have fun,

D

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H2OSB · Post by **H2OSB** » Tue Apr 23, 2002 1:52 am

Duc--

So what'd you find out via your notes? What are the draw backs of the SDS system? I like it for it's simplicity and low cost but am certainly no expert.

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johnL (aka H2OSB)

Duc · Post by **Duc** » Tue Apr 23, 2002 7:29 am

Each one has it's avantages and disadvatages. It really depends on what you are trying to do. SDS is quite a decent setup for the price, but lacks some of the higher options, which is fine. I don't think that any are bad. I kinda got burnt, the Haltech I bought will do 4 injectors and only 1 ignition. Well I wanted to run waste spark setup. Yeah I should have asked before I got it but now I have it. The sw on it is painful (DOS ASCII based no 3D maps), but I want more detail. Again it really is personal opinion.

D

<BLOCKQUOTE>quote:<HR>Originally posted by H2OSB:
Duc--

So what'd you find out via your notes? What are the draw backs of the SDS system? I like it for it's simplicity and low cost but am certainly no expert.

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PapaG · Post by **PapaG** » Tue Apr 23, 2002 8:11 am

DUC:
What haltech system do you have?

Duc · Post by **Duc** » Wed Apr 24, 2002 12:36 am

<BLOCKQUOTE>quote:<HR>Originally posted by PapaG:
DUC:
What haltech system do you have?<HR></BLOCKQUOTE>

ECM-6

D