Pulling the wool over the Eyes of the T7---tuning questions - The Saab Link Forums

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Old 08-18-2004, 04:31 PM   #1
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Pulling the wool over the Eyes of the T7---tuning questions

Since we all know the beloved T7 freaks out at pretty much anything you do, MBC is out of the question....however... since it boosts to a target air mass, which is read by the MAF sensor, and since it bases fueling on that reading, would it not be possible to use simple MAF adjusting piggy back computer like an Apex-I S-AFC or MAFterburner to compensate those values, tricking the ecu into thinking that less air was acutally being metered, and in turn forcing it to boost more. This would increase boot, but the air would contin mre physically oxygen(being denser) than it thinks The one concern I can see is possibly running alittle lean, but a a 4 bar map sensor should be able to bring that back in line. I am just sick of this attitude that nothing can be done about the ECU's control over things. There has to be a way to get it to play nice
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Old 08-18-2004, 08:02 PM   #2
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I of course don't have a T7, but i don't see why i can't participate in this discussion as well.

Check out MP Performance's website. I didn't read it all the way through, but supposedly the SMBC device they speak about may be a solution to this without an expensive electronic "piggy back" system.
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Old 08-19-2004, 01:00 PM   #3
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We are not talking about your normal 8psi turbo car. B235R varies boost all the way up to 20+psi right up to the point knock occurs and then tapers boost off to keep your engine alive. Well when you start messing around with sensors or MBC's or SMBC's you are essentially disabling the knock control and rolling the dice. Do you want to risk your engine for some cheap extra ponies? I sure don't. I personally do not agree with most and I believe hardware mods can show benefits. Besides, tricking the MAF would only throw a CEL or limp mode because (contrary to popular belief) the MAP has the final say in fueling even with T7.
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Old 08-19-2004, 02:41 PM   #4
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I am not talking about slapping an MBC, shooting for 20psi and hoping for the best....
I am talking about a way to increase boost and fueling correctly, but tryign to get around the so called "intelligence" of the T7. Frankly It makes no sense to me that the ECU would boost to a target air mas alone. I too imagine that the MAP sensors are there for a reason so they have to play some role. However anytime I ask , I get the same answer..."the viggen boosts to a target air mass depending on conditions...blah blah blah..." So thinking along those lines, dropping the MAF reading say about 30% with an SAFC, and adjusting boost back up to compensate. Concurrently ading a 4 bar FPR to bring up fueling, then Dyno tunning the S-AFC to ensure you in a nice sweet spot, not too lean , not to rich aroun 11.5-12:1 AF. No you say the MAP controls boosting? How/why? That may throw a wrench in my idea, not that you can't get around that pretty easily clamping the voltage, but it adds another dimention. The reason for all this is I don't really beleive that the cost of the ECU's out there are justified. I mean almost $1000 USD everewhere I look. It's rediculous! I can almost buy a complete ECU tunning package for that from EVC, that will let me do as many ECU's as I want, and Make a buck or two at it!
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Old 08-19-2004, 04:35 PM   #5
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I can almost buy a complete ECU tunning package for that from EVC, that will let me do as many ECU's as I want, and Make a buck or two at it!
You and I think alike.. There is a big market for custom ECU tuning for all makes. I think the reason no one has tried it the way you speak of is because it is easier to tune the ECU than hack everything around it. Even if you have to drop the money for an emulator.
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Old 08-19-2004, 10:18 PM   #6
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Using a MAF controller would be the same that partly covering your MAF in debris or partylally bypasing it, because in these cases the ECU will measure less airmass than the actual flow is. It would be wrong to think that you would gain much power through this trick. Why?

T7 is will boost to a target airmass, specified in ECU maps for given rpm, load etc. MAF is the primery calculation value for fueling, but also MAP+ intake temp and VE are used to look out for this value to rule out possible MAF faults and help with fueling calculations in rapid load change situations like gear changes under WOT aso.
Now if you would want to tweek the MAF value, the current airamss flow to the engine would be x mg/combustion + tweeked mg/combustion part. ECU will only see the first one. I would be wrong to believe that the ECU would fuel loads more in these kind of situations to keep A/F healty because it wont.

If the MAF reads x mg/combustion ECU will basically try to fuel the system based on it. Now since we have the +tweeked airmass/combustion the engine will run momentarily lean since it is getting more air than the ECU did measure. With the help of lambda the ECU will know that system is running lean and adapt to the new situation.
In some margins the ECU will add fuel but remember that the airmass is also looked after with MAP+intake temp and VE. T7 It will CEL, either "system too lean" or MAF value too high. I dont know which one will come first, but the "system too lean" will be lit if fuel trim goes out of given "window". MAF reading too high is caused by too large variation in airmass between actual airmass (MAF) and calculated airmass (MAP+temp, VE).
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Old 08-20-2004, 05:33 AM   #7
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So what values are these ECU tunners modifying then to get increase in airflow/boost, without the CEL being engaged? A combination of all values from IAT, MAF, MAP? I doubt that they are going so far as to change all the parameters you are indicating. With most ECU tunning SW you can pull the Hexidecimal values directly in to a 3d map, and simply pull the points in the rev range you want for boost, fuel and ignition maps. It's definately not rocket science, and with a wide band, and a dyno, in maybe 3 hours max you would have a 99% workable , safe map set. So the costs of these ECU's is clearly not warranted on the most part. I just have never heard of and ECU being so troublesome as this. No other car I know is this difficult to tune. I have built cars running stand alone ECU's that seem to be an easier job then this thing!
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Old 08-20-2004, 06:39 AM   #8
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Quote:
Originally Posted by The Vigg
So what values are these ECU tunners modifying then to get increase in airflow/boost, without the CEL being engaged? A combination of all values from IAT, MAF, MAP? I doubt that they are going so far as to change all the parameters you are indicating. With most ECU tunning SW you can pull the Hexidecimal values directly in to a 3d map, and simply pull the points in the rev range you want for boost, fuel and ignition maps. It's definately not rocket science, and with a wide band, and a dyno, in maybe 3 hours max you would have a 99% workable , safe map set. So the costs of these ECU's is clearly not warranted on the most part. I just have never heard of and ECU being so troublesome as this. No other car I know is this difficult to tune. I have built cars running stand alone ECU's that seem to be an easier job then this thing!
I totally agree. I believe some people are making this out to be way more difficult than it actually is. I've have helped tune a few cars through this 3dmap your speaking about that contain the same sensors as a T7, and although its not easy if you don't know what your doing....I'm sure the T7 is no different.

I definately think that this is what all the company modifying the T7 are using as well. I still think that once the hexidecimal values are found and able to be edited, we can achieve tuning the T7 ourselves as well.
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Old 08-20-2004, 09:21 AM   #9
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Quote:
Originally Posted by The Vigg
So what values are these ECU tunners modifying then to get increase in airflow/boost, without the CEL being engaged? A combination of all values from IAT, MAF, MAP? I doubt that they are going so far as to change all the parameters you are indicating. With most ECU tunning SW you can pull the Hexidecimal values directly in to a 3d map, and simply pull the points in the rev range you want for boost, fuel and ignition maps. It's definately not rocket science, and with a wide band, and a dyno, in maybe 3 hours max you would have a 99% workable , safe map set. So the costs of these ECU's is clearly not warranted on the most part. I just have never heard of and ECU being so troublesome as this. No other car I know is this difficult to tune. I have built cars running stand alone ECU's that seem to be an easier job then this thing!
We are talking about two different things here
1.reprogramming the ECU
2.fooling the ECU

The first should not be that hard if you have the right tools. Just increase the wanted airmass/combustion to the wanted values and you are about done.
Since the system is expecting a increased airmass/C flow now why would it light the CEL?

What I wrote above is true when fooling the ECU, these things need to be looked after if you want to be sucessful in what you are doing. Search around in different saab boards and see how many piggyback systems will work with T7 that will work with many other car manufacturers. T5 can be fooled no question about it and it only has three maps to begin with. T7 on the other hand carries about 1000maps.

Why is the T7 so hard to fool? It is too smart compared to many other similar products in use by other car manufactures. For instance knock control, you wont find a similar ionization measurement in any ohter car. This feature alone will get you in trouble if you dont know what you are dealing with. T7 is constantly running on the "edge" when thinking from the view of knock. this is because the engine will perform the best when it is one the limit of knock.

I you want study around about the T7 there are many places to look.
Get WIS for starters and if that does not satisfy you, look here
http://www.fs.isy.liu.se/Publications/
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