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Discussion Starter #1
Hello all,

I have a NG 900SET with stage 3 power using Maptune for my ECU... i.e., 3 inch downpipe, racecat, k&n filter, hyperboost bypass, and one-pass aluminum intercooler.

If I can find an intercooler that provides increased air flow of say... 400+cfm vice the current 125cfm my aluminum one-pass intercooler upgrade has. Should I consider that vice a larger turbo.

I find that the intercooler seems to become the bottleneck in the car if you are considering a larger turbo.

I am considering a stage 4 upgrade..i.e. bigger injectors, wastegate, ecu, and larger turbo. The cost of an intercooler is about half the cost of a turbo used/new. If increased airflow/cooling is possible in the space on the car using a more efficient intercooler, I suspect there is potential for increased torque/hp.

Does anyone know of the airflow specs the hybrid t3/t4 or larger turbo on its output, vice the t25 of the ng900 T's? Also, has anyone experimented with porting the throttle body, or changing the spring rate on it?

Many regards

DC
 

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Discussion Starter #2
Hmmm..., sooner or later I'm hopeful the experts will pop in....but upon further thinking ..., that is if my logic is correct...

better intercooling, and potential for more airflow going together (bigger intercooler and turbo), might be some awesome potential...but can the ECU compensate with enough fuel from the bigger injectors?

hmmm
 

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As you may know, I have a 1999 9-3 tuned by Hirsch Perfromance. Upon my last tuning, they mentioned I should look for a better intercooler before worrying about a better turbocharger. I have the Viggen model I/C and they showed me the difference of it and their's. Their's is much thicker, therefore giving more flow and cooling capacity. By appearance, it looks about the same to the unit sold by Abbott, or the unit sold by Taliaferro, Speedparts, Elkparts, etc.

FYI I have a 2.0 with a stock T25 turbo. Other power mods are the intake mod, 3" downpipe & cat and, the Saab stainless sport cat-back exhaust. After the last ECU tuning, Hirsch got the power up to 260 hp and 350 Nm.
 

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In addtion to what the other Eric said, it's the relationship between intercooler flow and efficiency you should be looking at, not flow or efficiency only. For instance if you have an IC that flows 400 cfm, but fails to drop intake temps lower than 80 deg C for your particular application, you may well end up with less power and more lag than with, say, a liquid/air IC that only flows 100 cfm but delivers an intake air temperature of 30 deg C.

Then there is the internal air volume of IC and intake tubing to be considered. Some folks use big-a** truck IC's for their project cars with rather adventurous pipe runs to make them fit. The size is good for cooling efficiency - but after you squeeze the throttle that big column of air needs to be put in motion by your comparatively tiny air pump that a low(ish) compression 2.0 litre engine constitutes, before anything useful happens.

You say you already have an upgraded intercooler versus the OE item - unless you're planning on over 300 hp I'd leave it at that, and concentrate on getting the restrictions in your intake system sorted if you haven't done so already (Maarten and Eric -9-3 Hirsch- can fill you in on the details), sorting the exhaust, replacing your turbo with a more suitable model for your purpose, and have the fuel, boost and ignition maps within the Trionic ECU altered to match by a reputable tuner - seeing as you're in the US, methinks it wil be best to strike a 'package deal' with turbo and software from one and the same supplier - getting the car to Sweden or Switzerland for a custom re-mapping session might be a bit extreme.... As you already have the Maptun Stage 3 software in there, getting the Stage 4 including the necessary hardware (turbo) would be the obvious route, as you get a 90% discount on the new software.
 

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That is all the advantage of the Hirsch, Abbott and other units that replace the Viggen I/C. The thicker core although it flows a bit more, is just that much more efficient at the cooling process. I know for a fact that the Hirsch unit is nearly double the thickness of the Viggen unit.
 

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Discussion Starter #7
Thanks Eric's...

As 325 to 350 in torque is the "magic" number, matching boost pressure with the right amount of fuel will be the next stage ECU's job..., but considering a device (intercooler, I have) out of a car that comes out of the factory @ 225 - 250hp, perhaps a different way of thinking is required or necessary.

As you (second Eric) mentioned, I thought about whether the t25 pump/turbo would be ineffective with a larger intercooler. Like blowing up a small balloon vice blowing up a derigible. Your point is well taken..., but looking for measureable devices to base hypotesis or next configuration to reach the magic number more cost effectively before proceeding.

As the first Eric mentioned, bottleneck is my concern, especially with a larger pump; but as the second Eric mentioned, heat is also my concern, hence my deductive reasoning for a more efficient intercooler. The intercooler I'm currently researching is on "http://www.bellintercoolers.com/" and looks to be where I'll find a more customized solution.

I had also considered the "woosh" sound to blow off the added boost due to the increased heat, but have a preference for the conservative sound and will continue recirculating; although it may be difficult to achieve using 2.25/50 cat-back exhaust pipes.

I copied others in stages, to achieve similar results without having to dyno at each stage....now I'll have to dyno for a comparison at the next stage to see a difference.

Hmmm..., maybe Adrian will be the devil's advocate and have something to offer here as food for thought here...

back to "thinkering" ......

DC
 

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Time to play devil's advocate eh? First off ... typically turbo-lag associated with a bigger intercooler isn't a huge problem. Most of the racers I know actually noted considerably better throttle response when a larger intercooler was fitted. I'm sure there is a limit to this logic, but the Viggen's intercooler is not exceptionally large and one twice or even three times the size would not give a noticable increase in turbo lag provided the piping wasn't exessive.

Think of it this way: Intake volume isn't the big problem when it comes to turbo lag. In order to pressurize the intake system on the far side of the intercooler the air has to flow through the intercooler. So if the intercooler flows too slowly this process takes a long long while.

More food for thought: The Viggen intercooler has 8 tubes for air to flow through, each is about 1/4" thick, 2.25" deep, and 22.25" long. This gives the Viggen IC about 12.52 cubic inches of volume ... which is roughly the same as 4 inches of 2" diameter piping. So even doubling the volume of the Viggen's IC would increase the actual mass of air next to nothing. What's 4" of pipe next to the 4-5 feet from turbo to intake? Mr. Yankton's monster 18"x 15.50" x 3.50" intercooler has roughly 150 cubic inches of internal volume (the equivalent volume of a 3" diameter pipe 21 inches long), more than 10 times the stock Viggen IC, but he did not have any serious lag as a result. Why you ask? Because your Saab engine pulls in almost that volume of air every two rotations. And given how quickly it can rotate, you can imagine this is not really a significant increase.

As for the discussion on what to do next. At this point your Saab won't benefit from either. Big turbo won't work well with small IC, and big IC will spin your turbo outside it's compressor map and all that extra cooling will only barely makup for the decreased efficiency. Time to upgrade both.
If you have to only upgrade one though, go with the bigger turbo. You'll notice more lag, and it won't cool terribly well with the small IC, but it will be more efficient at high RPM where you're really worried about high intake temps. So even at stage 3 power, a larger turbo is a safer idea even if it doesn't make the car faster. Just my thoughts anyway ... onto the next discussion. *peruses through the forums*

Dubbya
 
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