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Old 01-14-2005, 04:11 AM   #1
SaabTuner
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Default I Could Use Some Help From Tuners on a non-Subaru Tuning Argument!!

I've gotten into a bit of an argument with some fellow Saab guys. This should keep you tuner types thinking for a bit ...

Here's the argument:

Many of the aftermarket tuners claim that they can take a "230" bhp engine to 290 bhp with only an intercooler, TBE and tune. Seems fair, right? I mean that's not a huge power increase for a 2.3L with a TD04HL-15T

Here's the problem:

1. The car runs an 05 cm exhaust housing which reaches "choke flow" at or below 4,500 RPM. No change in VE is possible above 4,500 RPM, and no significant change in pumping losses. (Very slight change, but minimal as the TBE still has a catalyst and the stock exhaust is 2.5" and all mandrel bent.) I'll give a small explanation of the fluid dynamics behind this at the bottom of the post.

2. The "tuned cars" run zero additional airflow compared to the stock car. The stock car pulls in 26.89 lbs/min, and the tuned car pulls in 26.8 lbs/min of airflow. (203 grams per second) The "tuned car" does get more torque from having more airflow at lower RPM, but only 10% more.

3. Intake temps are meaningless on these cars because the measure boost in milligrams/combustion; if the temps go up, the boost pressure goes up. In either case the difference in intake temps between stock and modified is only about 15*F at top end.

4. Fuelling is slightly changed on the "tuned" car; the air/fuel ratio at peak power goes from 11.2:1 up to 12.17:1. This might free up some power, but 60 hp? I think not.

5. No claims were made about improving ignition timing by any of the tuners I talked to. The stock car runs a lean mixture in midrange (12.5-13.5) and only 5-8 degrees advance, while climbing to 14-15 degrees by 5,500. Remember that this engine is 9.3:1 compression, has high quench, a very compact combustion chamber, square bore-stroke ratio, and the mixture will burn very quickly. It also runs a capacitative discharge ignition system.

Not only that, but the EGT has gone up with the slightly leaner mixture, so they could not have advanced the timing much if at all. Stock EGT is roughly 1800F and the car only survives with a nimonic set of exhaust valves and turbine.

Here are the tuners claims:

The change from 11.2-12.2 A/F ratio and the slight reduction in pumping losses from the larger intercooler, without ANY additional air getting into the engine, make 50-60 horsepower.

To me that sounds like BS. Some of the tuned individuals have posted video runs of their 100-200 kph times and they are quite good, but to me I feel tempted say they are going downhill.

I could really use some help figuring out how a car flowing more air than a stock WRX turbo is rated for can be "supposedly" only making 230-240 crank hp!! And how a car which does not flow any more air, only slightly less fuel, and no additional ignition timing makes more power!?

Thanks much to any tuners willing to share their thoughts!

Adrian~

p.s. Basics: In a given fluid the pressure and temperature of that fluid are directly related to the average velocity of the particles within. The pressure is the sum of the vector cross products between the momentum of the particles and the walls of the of whatever area of measurement you are using. It represents the sum of the forces of impact. The heat is the average Kinetic energy of the particles within. (Their speed.)

Choke flow: When a fluid flows through an orifice, the driving force of that fluid is the imapacts of the particles behind it. When the velocity of the fluid through the orifice in one direction reaches the average speed of the particles then none of the particles behind it can "push" it any faster because they are not moving any faster and do not impact them. The only way to move more "mass" of fluid through the orifice is to increase the fluid's density. (Compressible fluid dynamics.)

The result of choke for is that any change in pressure downstream of the turbine which does not drop the pressure ratio below 2:1 will not change the flow through the orifice at all. As the engine moves faster and faster beyond choke flow the backpressure increases nearly linearly irrespective of post-turbo exhaust backpressure.

You can actually see this effect on the turbine maps at www.atpturbo.com in which the volume flow through the turbine stops increasing beyond a 2-3 pressure ratio. Only the mass-flow increases from the increase in pressure.

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Last edited by SaabTuner; 01-14-2005 at 04:24 AM.
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Old 01-14-2005, 08:08 AM   #2
happasaiyan
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hmm, first off, at that stock EGT!!

well, the leaner AFR is probably where most of the gain is...going from 11.2 to 12.2:1 is HUGE. AFRs just went from richer than optimal to almost optimal.

not only that, but more efficient intercoolers have been known to produce 10-15whp just by themselves on subarus. its amazing what an efficient intercooler can do. its not only about better pumping losses, but also that the air will get more dense with the better IC.

the denser air + leaner AFR = more power.

60hp = 50whp on a saab? id say its do-able...but the ratio of gains caused by AFR to IC is probably about 70:30...and together they can make some nice gains.

this is just an educated estimate on my part...so take it for what it is...
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Old 01-14-2005, 09:04 AM   #3
ride5000
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put it on a dyno and stop pontificating about whether or not it's possible?

arguements are fun and all, but it all really happens where the rubber meets the road.
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Old 01-14-2005, 09:11 AM   #4
sammydafish
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I think the Air Flow Meter just doesn't read more than 26.8 lbs/min. the tunned car is really breathing more air, but the AFM is clamped at a certian output (maybe with an FCD or something), therefore making the ECU not see the aditional air (caused by the more efficient intercooler) cooler air = more dense air = more mass of air at same CFM so it had to come from somewhere. Because the ECU doesn't see the aditional air flow, it caps enrichment and the car leans out a bit. Bang, 50hp.

That's my story and I'm sticking to it
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Old 01-14-2005, 09:12 AM   #5
jblaine
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See: ride5000
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Old 01-14-2005, 01:13 PM   #6
bboy
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It does not add up. The AFR change is good for maybe a 10% HP gain, but I seriously doubt the ~20% gain you would need to make the power pop up 60HP with all the other flow mods. Me thinks more air + more fuel, or bogus.
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Old 01-14-2005, 01:44 PM   #7
serendipity
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You forgot: Saab tuners are mysterious, and the B235R is an invincible engine that beats anything else.

I dropped my Saab because the Saab performance scene was exactly like this. "I put a viggen intercooler on my 9000 Aero and outran an '03 cobra on the highway". Suuuure you did.

The fact is there's very little hard evidence in the Saab scene of gains. Engstrom will claim his PPC tuning and an exhaust nets you a 20% increase in power, but there are so few people using his tuning, and using it as part of a comprehensive performance program (including measuring performance before and after) that it's all speculation.

Having said all that, a friend of mine has a Viggen with some relatively basic mods - stock turbo, but front mounted spearco intercooler, Engstrom-tuned chip, and exhaust, WAS running increased boost, and was putting down in the neighborhood of 280whp and 330lb-ft. His engine eventually blew a piston though. So there's certainly room with the right tuning to get big power out of the B235, but I doubt you'll get there without increased boost.
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Old 01-14-2005, 09:00 PM   #8
SaabTuner
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Quote:
Originally Posted by serendipity
You forgot: Saab tuners are mysterious, and the B235R is an invincible engine that beats anything else.

I dropped my Saab because the Saab performance scene was exactly like this. "I put a viggen intercooler on my 9000 Aero and outran an '03 cobra on the highway". Suuuure you did.
I know, and it frustrates the heck outta me. The B234R (older engine) is pretty tough, at least from a shortblock standpoint. The pistons on it look like diesel pistons! There are a fair share of pretty impressive dyno-sheets from that engine. (Plenty in the 400-500 hp range on stock shortblock, but with LOTS of peripherals.) But the newer version, especially of the 1999 model year uses wussy pistons. If it were 8:1 compression it would be fine ... but it can't handle 300 hp with 9.3:1. The MY2000-2002 engines were fitted with trapezoidal small ends on the con rods to allow fatter pistons. They're slightly tougher ... but not that much tougher.

I've had my car on the dyno, and the other guy his. But I only have wheel hp, and he only has crank hp. He didn't bother to ask his dyno operator what his whp or tranny losses were , so it's almost impossible to compare. He says my dyno is full of it, and I say his is. He also repeatedly sends me videos of his car accellerating. It's quick ... but all the videos are in the midrange; his car DOES flow more in the middle of the RPM band. Peak horsepower is about peak flow at the RPM for peak hp.

And who knows if he found a nice downhill spot or not.

With regards to intercoolers, if the air gets denser on this Saab it will just run less boost. That's the downside to a MAF based boost system. You may get denser air ... but it won't mean MORE air, nor will it affect your A/F ratio at all. Besides that, I have datalogs for my airflow and he for his; for similar temperatures mine is only about 20*F warmer, and the stock intercooler barely reaches 1 psi of pressure drop.

It just doesn't make sense that a car with only 1 A/F ratio less would run 60 more hp. If my 213 whp translated to 260-265 crank horsepower (for whatever reason, I doubt it does), I could see the pumping losses and leaner ratio making up for the rest of the 25-30 hp on a good day.

With regards to the MAF sensor, it is the GM 3" unit. It can read much much higher than 26.8 lbs/min.

Thanks for all the replies!!

Adrian~

p.s. That's not the highest stock EGT either! Just the highest sustained EGT. Often in midrange the car will run 13.5:1 A/F ratio before richening up towards redline, at over 14 psi and only 5-8 degrees of advance! The EGT there gets in the 1900-2000F range for short periods! Still makes good torque on the dyno: 251 at the wheels for mine.

Last edited by SaabTuner; 01-14-2005 at 09:12 PM.
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Old 01-14-2005, 09:14 PM   #9
SaabTuner
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Quote:
Originally Posted by bboy
It does not add up. The AFR change is good for maybe a 10% HP gain, but I seriously doubt the ~20% gain you would need to make the power pop up 60HP with all the other flow mods. Me thinks more air + more fuel, or bogus.
Exactly!! If he had a better exhaust housing for the turbine, headers, a pre-turbo intake of some kind, and maybe cams ... THEN I could see pumping losses being dramatically reduced. If the effort to move air is reduced enough you can make lots of power without much air.

But his car is just "too stock". If he had 28 lbs/min instead of 26 this would be totally believable.

Adrian~
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Old 01-15-2005, 08:15 PM   #10
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maybe with race gas and a whole bunch of advance?
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Old 01-16-2005, 05:48 AM   #11
SaabTuner
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Quote:
Originally Posted by Jaxx
maybe with race gas and a whole bunch of advance?
I'm waiting for him to send me his ignition curves. He's reluctant to do so and keeps making excuses so I'm suspicious. That very well could be true though as Europe has higher octane than California.

With just a reduction in pumping losses across the board it would make sense. Oh well.

Adrian~
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