[WooSAABy]

Hi all,

I sent an email to Hirsch Performance AG (SAABs official Tuning Partner!) asking if they will ever produce an Air intake induction kit or a Blow Off Valve for the 93 SS. Heres the reply I got:-

"Modifying intake components upstream of the air mass meter is a very difficult task, and requires complete engine recalibration to avoid severe engine damage due to poor turbo control resulting from the changed flow characteristics through the air mass meter, or air mass meter damage caused by oil deposits from cheap "sport" air filters. Therefore, we only include modified intake components on upgrade packages with so high output that it is absolutely necessary. Simply replacing intake components without recalibration is a sure way to crack the pistons of a modern turbo engine.

The main advantage of aftermarket blow-off valves is that they sound cool. Technically, they are quite pointless, and since we are primarily interested in real power, we prefer to leave them as they are.

Sorry for the dry answers.

Cheers,

Erik"

What do you all think of that then?

 

[cjhutch]

I agree with almost everything except for the cracked pistons coming from a modified air intake. I have never heard of that and if CAI were destroying pistons then they would be thrown out the door by now and nobody would use them. The face remains that they do provide some performance increase on some cars, but our cars are not in that group. A BOV is pointless until you are making over 25psi of boost from what I've heard.

 

[ctrlz]

A BOV is pointless until you are making over 25psi of boost from what I've heard.

The pressure has nothing to do with it. CBV's are better because they don't affect the A/F ratio and allow the turbo to maintain speed.

Hirsch's reponse somewhat echoes that of BSR on the subject of intakes. I think Hirsch is being a bit more forthright on the topic of flow characteristics and how sensitive the MAF is to any changes. The "engine calibration" they mention is the MAF transfer function, which is a set of parameters that accounts for any and all flow characteristics of the tubing and filter. BSR's Optiflow stays close to the original Saab configuration, but changes the filter. Although I can't prove it, I strongly suspect that's enough of a design change to invalidate some of the data points on the MAF transfer curve.

BTW, WooSaaby, I think it's great that you e-mailed Hirsch and that they gave you an actual explanation. They could have just said, "We don't sell 'em 'cause they don't work!"

 

[DavidMorgan]

Cracked pistons? hope no-one ever has them..

But it comes back to the often repeated fact.
Changing air intakes do nothing but cost money, make noise and result in poorer filtering which could consequently be a risk to the engine....

 

[ctrlz]

Simply replacing intake components without recalibration is a sure way to crack the pistons of a modern turbo engine.

What do you all think of that then?

What they mean by "cracked pistons" is the problem with using larger diameter intakes than stock. Most CAI kits sell on the basis of "bigger tubing is better." This causes a leaner A/F ratio and higher intracylinder temperatures. The 93SS does not tolerate this for long, which is a good thing.

 

[Vector-SS]

But wouldn't the car throw a CEL prior to actually screwing up the car? If the MAF is really that sensative, then any slight detection of increased/decreased airflow will be detected after at least 3 runs?

 

[krock1030]

Even though the BSR Optiflow isn't far off from the OEM air intake... it's still different, does that mean I should not buy the Optiflow because it may mess up the calibration? I'm asking because the air intake was going to be one of my first mods..

 

[mike saunders]

But wouldn't the car throw a CEL prior to actually screwing up the car? If the MAF is really that sensative, then any slight detection of increased/decreased airflow will be detected after at least 3 runs?

Yes...

The variances in airflow won't be great enough to lean out and crack a piston, even with a modded car.

 

[ctrlz]

But wouldn't the car throw a CEL prior to actually screwing up the car? If the MAF is really that sensative, then any slight detection of increased/decreased airflow will be detected after at least 3 runs?

The problem is if you use a larger tube, the MAF and car still think it's the smaller tube. The MAF only samples a small cross section of airflow about the size of a dime.

 

[SAABRoma]

The problem is if you use a larger tube, the MAF and car still think it's the smaller tube. The MAF only samples a small cross section of airflow about the size of a dime.

You're exactly on point ctrlz. The MAF sensor is designed for the smaller tubing. Its like using a BB gun to shoot a bear (only analogy I could think of at the moment).
Question: Is there a different MAF sensor which would have the same analog/voltage reading scale, but designed for the bigger pipe ?

 

[ctrlz]

Question: Is there a different MAF sensor which would have the same analog/voltage reading scale, but designed for the bigger pipe ?

The same MAF sensor could work. The ECM would just need a different transfer curve.

The MAF basically reports air mass per unit time. Say it reports 10. The ECM has a lookup table that knows 10 means a total flow of 100 for the stock tube. If you increase the size of the tube, the air mass gets more "spread out." So a MAF reading of 10 may mean a total flow of 120 for the larger tube. But the ECM doesn't know the tube is larger, so it adds fuel as if the air mass flow were 100.

Some intake kits for other cars include a MAF which reports a lower voltage to compensate for the larger tube. This allows the same ECM settings to be used for the larger MAF.

 

[cjhutch]

I think using a larger MAF even if it works would be pointless because from everything that has been reported the restriction of air flow is on the exhaust side and not the intake.

 

[SAABRoma]

The same MAF sensor could work. The ECM would just need a different transfer curve.

The MAF basically reports air mass per unit time. Say it reports 10. The ECM has a lookup table that knows 10 means a total flow of 100 for the stock tube. If you increase the size of the tube, the air mass gets more "spread out." So a MAF reading of 10 may mean a total flow of 120 for the larger tube. But the ECM doesn't know the tube is larger, so it adds fuel as if the air mass flow were 100.

Some intake kits for other cars include a MAF which reports a lower voltage to compensate for the larger tube. This allows the same ECM settings to be used for the larger MAF.

By your analogy, should it report a higher voltage ? Or are the voltage and sentor reading inversely proportional ?

I think using a larger MAF even if it works would be pointless because from everything that has been reported the restriction of air flow is on the exhaust side and not the intake.

Its true that this upgrade wouldn't make an impact on performace. However, once you get that downpipe upgrade, this issue would come up.

 

[ctrlz]

By your analogy, should it report a higher voltage ? Or are the voltage and sensor reading inversely proportional ?

Erik from Hirsch has a reason to be short in his reply. Although sensor "cheats" are advocated in some forums for other cars, this is a compromise solution at best. This article explains it pretty well:
http://www.allfordmustangs.com/Detailed/583.shtml

Manufacturers spend tens of thousands of dollars to develop a MAF trasfer curve for a given intake configuration. This involves some specialized equipment (like a flow bench) as well as road testing. It is pretty naive to think that a $200 intake kit can improve on this.

The MAF sensor is probably the most important sensor on the car, moreso than either oxygen sensor.

 

[traqweapon]

Well for development costs, tens of thousands is nothing. Tens of thousands was probably spent just to make the decision to use our rediculous cup holder :lol:

Intakes, BOVs...
I wouldnt call them useless. They just dont bring the biggest steak to the table when it comes to performance. Im familiar first hand what it feels like in a car with a decent turbo on it that cant dump the charge air during a shift.

Plus, BOVs on MAF cars is nothing 'arcane'. Look at the mods done to some rediculous DSMs. If you have to have the sound... get a BOV and just recirculate the damn thing :lol:

 

[ctrlz]

Im familiar first hand what it feels like in a car with a decent turbo on it that cant dump the charge air during a shift.

I suspect this is why CBV's are designed the way they are. The turbo manufacturers made the bypass system integral to the turbo. They must have gotten sick of warrantying turbos that didn't have separate BPV's or BOV's set up properly.