Downpipe without ecu upgrade on t-7 - The Saab Link Forums

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Performance Modifications for the NG900 / Old 9-3 This forum contains PERFORMANCE related Q&A's for the NG900 and 9-3. This may also include suspension.

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Old 07-17-2004, 08:55 AM   #1
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Downpipe without ecu upgrade on t-7

just wondering if anyone has this or knows anyone who does, as i would like to know if it is ok and how it runs.
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Old 07-17-2004, 10:27 AM   #2
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There is much debate regarding whether or not the T7 ECU will allow power increases over the stock levels. I am inclined to believe it will but again there are many who insist there will be no change in peak power. At worst you will have a much faster spooling turbo. There are no downsides if the installation is done correctly but you really should be adding a sport exhaust if you don't already have one.
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Old 07-17-2004, 02:39 PM   #3
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I think I may have figured out why the T7 has such a coniption about mods like this.

It's pretty well known that Saabs base their boost control on air-mass/combustion (even T5 did that, at least in the later years) ... but T7 uses the Air Mass Meter to control boost pressure, and the MAP system to control WOT fuelling.

Ordinarly that doesn't cause a problem, but when you put an exhaust on the engine it changes the Volumetric Efficiency. Now the same boost pressure equates to more air moving into the engine. On T5 that isn't a big problem, the engine just overshoots it's air-mass/combust and doesn't know anything is wrong. On T7, it gets confused.

Now the MAP sensor is saying that the same air-mass/combust is entering the engine because it cannot detect the change in Volumetric Efficiency ... BUT the Air Mass Meter CAN detect the change, and the two sensors are now in conflict. The sensor that actually controlls boost (the AMM) is trying to cut the boost back because more air is flowing for each revolution than should be, but the MAP sensor is telling it that the same air is entering as was before, and is also only fuelling for such.

In the end the sensors are battling it out and it's that inconsistancy that causes what appears on the dyno to be an adaptation downward.

Yes the turbo will spool quicker, and no you won't loose very much horsepower. But there probably isn't a ton to gain because of that problem.

Adrian~
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Old 07-17-2004, 04:22 PM   #4
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How does this apply to upgraded ECU's? What causes the BSR stage 2 for an Aero or Viggen to jump 10lb/ft when the cat-back is added? Wouldnt there be similar adaptation down to the stage 1 power levels?

Do the modified ECU's have the VE adaptation you mentioned on SSc?

Here is a link to a thread with some nice discussion of this topic. Good stuff as usual Adrian...

http://www.saabscene.co.uk/ubb/ultim...ic/23/889.html
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Old 07-17-2004, 04:57 PM   #5
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Quote:
Originally Posted by xaamottomaax
How does this apply to upgraded ECU's? What causes the BSR stage 2 for an Aero or Viggen to jump 10lb/ft when the cat-back is added? Wouldnt there be similar adaptation down to the stage 1 power levels?

Do the modified ECU's have the VE adaptation you mentioned on SSc?

Here is a link to a thread with some nice discussion of this topic. Good stuff as usual Adrian...

http://www.saabscene.co.uk/ubb/ultim...ic/23/889.html
Hopefully the new thread I started on SSc will make another good discussion. Until I had a chance to view the WIS program for myself it didn't make much sense to me why T7 would adapt downwards. Now it's clear.

The BSR stage 2 would probably have a different programming to the BSR stage 1. But ... even if it does not, small changes in VE are tolerated by the system and do not affect it. A full 3" exhaust causes too large a change.

I doubt the modified ECU's have an adaptive VE ... in fact modified ECU's for Saabs worry me quite a bit. They program the fuel and ignition curves very differently from the factory. It may yeild more power, but it is also much much harder on the internal parts.

The stock T7 ecu is programmed VERY aggressivly. The only reprogramming I would personally have done to a T7 car is retuning it for modified exhausts. I do not want to increase the thermal loads much on the engine. There are just a few small changes that I'd make.

Examples (to better clarify my point):

1. Re-tune for new exhaust, ported head, camshafts, or other device which changes VE. Keep ignition timing and boost pressure about the same (maybe small increases such that knock control registers the same average knock/minute/degree celcius), let the better VE give the additional power, keep a/f the same. More power, no extra strain on the internal parts.

2. Re-tune for water injection. This allows more boost without strain on the motor, and requires more ignition timing to be effective. Again I'd try to keep the knock sensor averaging about the same number of corrections it did before, possibly less.

Both of those tuning techniques would not alter the strain on the engine significantly. Knock kills engines, and there are two ways to make the engine weaker, and therefor easier to kill:

1. Raise the power, either by boost or increased volumetric efficiency. This actually doesn't increase the strain and thermal loads very much. As long as you keep the ignition timing where it was previously and don't take away any fuel (keep things nice and rich, OR use water injection) things stay nice and cool and your engine will be happy.

2. Raise the boost a LOT and retard the ignition timing all to heck. This is what 99% of the aftermarket tunes are like for Saabs, mainly because Saab tuned the engine like example 1 from the factory. The only way to get more hp and torque than example 1 is to use example 2, or to buy lots of hardware parts. (Water injection, exhausts, intercoolers etc.) So to get hp gains, they raise the boost a lot, pull back the ignition timing and "fatten the curve". But it increases the thermal loads on the engine so much that the aluminum pistons, which are normally much stronger than necessary, become weak (heat makes aluminum MUCH weaker) ... on T5 that's ok, they can handle it because they are way way way way overbuilt for a stock car. T7 was just not designed for that. It has lighter and weaker pistons, which help fuel mileage a LOT, but also make it easier to break.

Hope that all makes some sense.

Adrian~[/i]
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Old 07-17-2004, 10:01 PM   #6
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The BSR stage 2 would probably have a different programming to the BSR stage 1.
The program is the same. Perhaps the software's WOT map is designed for the extra air flow provided by the exhaust and without the exhaust it is running rich. I don't know of any stage 1 dyno runs posted on the web and I havent done my car yet so I can't be sure. The documented instances of broken pistons caused by knock doesn't support this theory but again the ratio of stage 1 vs. stock ECU's with piston failure is unknown. I think the main problem with the stage 1 is the increase in EGT over stock .

Quote:
let the better VE give the additional power, keep a/f the same. More power, no extra strain on the internal parts...... (keep things nice and rich, OR use water injection)
I found it interesting that Nordic uses an uprated FPR in their higher stage T7 packages...In these days of marketing, the cheaper the stage 3, the more people will buy it. HP/$ is what everyone seems to be worried about. Nordic seems to abandon this philosophy in order to compensate for the biggest threat to a tuned T7 engine (knock and broken pistons) by providing much more fuel at WOT.

Quote:
Re-tune for water injection. This allows more boost without strain on the motor, and requires more ignition timing to be effective.
If the stage 1 software is retarding timing, getting the water injection tuned properly would be very difficult. Nick T. would know about this as he is running said software and water injection with good results.

Quote:
1. Raise the power, either by boost or increased volumetric efficiency. This actually doesn't increase the strain and thermal loads very much. As long as you keep the ignition timing where it was previously and don't take away any fuel (keep things nice and rich, OR use water injection) things stay nice and cool and your engine will be happy.
This is the direction I want to head but it is expensive and is going to take time. Intake and exhaust mods are the first step for me. Exhaust especially now because of the increase in EGT with the stage 1 software. This has me worried a bit but opening things up with the 3" DP and 2.5" cat back, ceramic coating the downpipe should help with intake temps and heat soak. Running lean worries me as well with the increases in airflow without the MAP system providing enough WOT fuel. Higher octane fuel is my only real way to compensate and try to eliminate knock at the moment.

Custom software is the only real way to get the most out of the modifications in the safest fashion.
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Old 07-29-2004, 02:20 PM   #7
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What about the O2 sensors? They will conpensate for a lean condition won't they?
And of coarse run the highest octane fuel available.....
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Old 07-29-2004, 02:37 PM   #8
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to answer your question ricot83 i have a 3in DP on my T7 with no cat...the CEL is on but runs fine.....not as much of a hp increase as i would have liked, but im shure that will come when i get my SQR stg 3...

for me i have all these bolt on parts to get ready for the ECU upgrade....
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Old 07-29-2004, 02:47 PM   #9
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Quote:
Originally Posted by iwantaviggen
to answer your question ricot83 i have a 3in DP on my T7 with no cat...the CEL is on but runs fine.....not as much of a hp increase as i would have liked, but im shure that will come when i get my SQR stg 3...

for me i have all these bolt on parts to get ready for the ECU upgrade....
Actually your CEL causes the car to have reduced performance in the form of bogging down. I get the same light since I'm catless, and my car bogs down a little. Once I had disconnected the battery for a while, the CEL disappeared and there was a noticable performance gain. Later the CEL come back on and the bogging continued.

I plan to add a cat soon as its not difficult to have done.
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Old 07-29-2004, 05:31 PM   #10
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yeah i remember nick T saying something about it...i too plan to get a cat but i think when i get a new muffler set up...so i can do it all at once...
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Old 07-29-2004, 07:42 PM   #11
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u guys think if i have a cat that it might not throw a cel... cuz i want a cat on there personally
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Old 07-30-2004, 02:08 AM   #12
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yeah we are getting the CEL because our O2 scensor is reading that we have no cat. i have been trying to find away around it...i know they sell an O2 scensor bypass that will eliminate the CEL w/out getting a cat...but i dont know wich wire on my car to splice...
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Old 07-30-2004, 02:09 AM   #13
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the reason i dodnt get a cat is because it was another $300.oo added on the the DP.....
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