true effectiveness of upgrades [Archive] - SaabCentral Forums

: true effectiveness of upgrades


chuckles07@aol.com
23-09-02, 11:30 PM
i met with amechanic today because my clutch is screwed, but anyway. he said that putting a high-po exhaust on my car would really do nothing. he said that the system that came in my saab now looked large and very good. he said there is no reason to tinker with anything except the muffler, and there is no pooint in doing a cat back. he also said ECU upogrades will not improve gass efficeincy while moving, only while idling. also, making a bigger air inlet will only do so much considering saabs engines can only handle so much air without booring the pistons. is all of this seem accurate?

ERP
24-09-02, 01:21 AM
The mechanic is not entirely wrong, but he knows nothing of turbos. A large exhaust will not increase overall horsepower by any significant amount. I have a 3" downpipe/cat and the 2.5" sport exhaust, it probably gives me and extra 10-15 hp by itself (top end). However, the large exhaust allows my turbo to spool up much quicker, I can reach full boost by 2100 RPM. So my powerband is improved by giving me more power low in the RPM range, where we all drive most of the time. My downpipe decreases backpressure, which allows for greater turbo speeds and higher boost pressures, ultimately giving me more horsepower. So the exhaust in fact can give a substantial increase in horsepower when the entire system is considered.

http://www.lehigh.edu/~erp4/saab/Upgrades/DownpipeTop.jpg

The mechanic's statement about ECU upgrades and gas efficiency does not make a whole lot of sense. Increasing the efficiency means more power is extracted from the same amount of fuel. This can be accomplished in a number of ways, for instance switching to a synthetic motor oil will decreases friction within the engine, less power is wasted and efficiency goes up.

I have an upgraded ECU and the purpose of it is to increase boost pressure and provide a fuel map for the increased boost. In general efficiency is not changed, although there is enough technical information to argue the topic for days. In terms of gas mileage my ECU can handle 21 psi and I can still get 30 mpg on long highway drives.

Basically what it comes down to is that turbocharged vehicles follow some different rules than naturally aspirated vehicles. What works for one type wont necessarily work for the other. But nobody can know everything, I'm sure that this mechanic knows more then me about tuning NA engines.

Eric

chuckles07@aol.com
24-09-02, 01:31 AM
im sorry, i should have clarified i have a 9002, NA engine. this woulkd probaly be the opposite of your statemtns?

ERP
24-09-02, 01:45 AM
Sorry about that, you do have a post titled "Help me upgrade my 1995 900s" which I should have remembered. I have the bad habit of assuming that all Saabs have turbos.

Eric

chuckles07@aol.com
24-09-02, 01:51 AM
so im assuming the opposite if true?

woodnutz
24-09-02, 05:15 PM
ERP..where did you get your 3" downpipe? I have a question. Is your cat a 3" in and a 2.5" out? I already have the 2.5" swedish performance exhaust on my car and I can notice a little more snappy accceleration? Can I make a 3" downpipe. I know the top of the pipe is tapered to fit in the turbo, but can that be manufactured by any pipe bender? If your cat is not 3" in 2.5" out, would that be the way to go to increase a little performance? How about a 3" down pipe right into the the exhaust with no cat? What could I see there?

ERP
24-09-02, 11:07 PM
I bought my 3" downpipe through Engstrom; http://engstrom.net/scstore/ Here is a picture of my downpipe, http://www.lehigh.edu/~erp4/saab/Upgrades/DownPipe.jpg

It comes with an adapter down to 2.5" so it will hook right up to your performance exhaust without any modifications. I bought the downpipe without the cat because it was a lot cheaper with plans of installing the cat later. I ran it without a cat for a few weeks but it is just too loud, a Saab exhaust should never turn heads. I finally bought a 3" Catco cat from Summit Racing for $50, then had it installed at an exhaust shop for another $50. This made the cost of the downpipe + Cat $350. A good exhaust shop could make you a downpipe for the same price. You should ask around to see which shop is the best and what they will charge. The parts that make up the doenpipe are all premade, the shop just cuts and welds them together. Make sure that you install the second O2 sensor after the cat so you do not get a CEL (check engine light)

Good Luck

Eric
http://www.lehigh.edu/~erp4/saab/Upgrades/3Downpipe.html

woodnutz
24-09-02, 11:19 PM
IS that picture of what all came when you bought it? If so, it looks like it was designed to take the place of the cat. When you had the cat installed was it cut into the second straighter pipe so you still had the taper to the 2.5" exhaust? Thanks for your input. Does the car sound better with the catco 3" cat then the stock cat?

dschneid25
25-09-02, 11:42 PM
hey ERP, I don't have so much a question about the downpipe itself but rather about Engstom's. I was thinking about getting an ECU from them but would like to know your input on how reliable they are and any problems you had with them, etc.
Thanks

chuckles07@aol.com
26-09-02, 10:31 PM
i wentr to a saab specialist place today and they said they had a saab sport exhaust for my 1995 NA for 380. iu thouhg thtis sounded like a good deal, but i was wondering if it would be worth it to put an aftermarket 2.5 or 3 inch in inseatd. (which the saab place said they could get for 4-500)

slob900
26-09-02, 10:40 PM
Do u know what manufacturer made that saab exhaust for ur n/a saab??? Is it saber performance??? I wnat a diff exhaust but i want to know how happy other people are they have gotten them done particularly on an n/a saab!

ERP
28-09-02, 02:20 PM
woodnutz - Yes, that is what came for the 3" downpipe. It connects directly up to the 2.5” sport exhaust, so I have no stock exhaust left on my Saab. The 3" cat was installed in the second long section just before the taper, farther back than the original cat. I think my Saab sounds better now, it is a nice lower note.

dschneid25 - Engstrom was easy to deal with and communication was good. The only inconvenience was that he had to order directly from Sweden and it took about 5 weeks for me to get it. In the US there aren't many options for ordering parts from Sweden, but Engstrom does a good job.

chuckles07@aol.com and slob900 - $380 is the cost for the Saab Sport Exhaust, and the exhaust is the same for NA or turbocharged Saabs. I don't know how it would sound on a NA Saab though. If you do get a custom exhaust I would not suggest that you get anything larger than 2.5"

Eric

Eric's Saab Site
http://www.lehigh.edu/~erp4/Saab.html

richard_ashworth
30-09-02, 04:49 AM
The mechanic is not entirely wrong, but he knows nothing of turbos. A large exhaust will not increase overall horsepower by any significant amount. I have a 3" downpipe/cat and the 2.5" sport exhaust, it probably gives me and extra 10-15 hp by itself (top end). However, the large exhaust allows my turbo to spool up much quicker, I can reach full boost by 2100 RPM. So my powerband is improved by giving me more power low in the RPM range, where we all drive most of the time. My downpipe decreases backpressure, which allows for greater turbo speeds and higher boost pressures, ultimately giving me more horsepower. So the exhaust in fact can give a substantial increase in horsepower when the entire system is considered.




Regarding back pressure and engine mods. Most people dont realise the usefulness of backpressure. Helping an engine breath in this way (i.e. high flow exhaust/induction) increases max power but you loose low down torque as the back pressure aids this. Its always a trade off so remember this before you spend thousands increasing peal power - you may loose some driveability.

ERP
30-09-02, 01:41 PM
You are correct richard_ashworth, it is important to recognize that in tuning a street vehicle the focus should not be merely on max power. But a good power and torque band through the RPM range. For turbo charged engines the turbo acts as a resistor and produces backpressure on the engine. Large exhausts after the turbo do not significantly change the backpressures caused by the turbo.

richard_ashworth
01-10-02, 02:49 AM
interesting.
i guess all the info i've been given has always been very general and not specifically for turbos.
maybe i will get that exhaust after all....

Zehone
28-02-03, 11:18 AM
Here's aquestion...
If increasing the exhaust too much hurts the torque and driveability of a N/A engine, then should i think smaller when upgrading the exhaust on my 98 900s? My car, being non-turbo, is DEFINITELY a street vehicle, how big should i go...2.5"? smaller...
what about just cutting out the center muffler and putting on a performance rear muffler without changing the pipe diamater, which i think is about 2.25" stock (is that right)?

Munki
28-02-03, 02:20 PM
he also said ECU upogrades will not improve gass efficeincy while moving, only while idling.
Frankly he is talking out of his ar5e.. :!

I had my ECU upgraded yesterday (1995 900S Coupé n/a) and, while it is not going to set any land speed records, there is a noticeable increase in power the car pulls better and even sounds better :!

All in all it's much more drivable than it was.

Mark P
28-02-03, 03:11 PM
I had my ECU upgraded yesterday (1995 900S Coupé n/a) and, while it is not going to set any land speed records, there is a noticeable increase in power the car pulls better and even sounds better :!

All in all it's much more drivable than it was.

Mine's done too, and it's considerably more drivable. The BHP increase is only in the region of 10%, but there's a significant increase in torque pretty much from idle upwards, and that (IMHO) improves the car no end! :cheesy: