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If he was using a mbc, that may probably explain it. When I used to have a Turbo XS mbc, the car would boost well until about 4500 rpm and then taper off to lower than stock level by 5500 rpm. That led me to decide that an ECU was a much better way to get more power.

Sometime after having my Hirsch ECU, I decided to see how high the boost protection was set at and such. A Dawes high performance mbc took it to quite insane boost that actually stuck around to redline. For fear of engine and transmission damage, it remained only a short lived experiment.

So depending on his boost curve, yeah.
 

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Discussion Starter · #43 ·
Indeed Eric (9-3 Hirsch) ... I looked at ERP's dyno sheets with and without boost controller. He has better power without it, but more torque with it. Since 50-100 is going to be affected about the same by torque as hp the time would probably be the same with either setup. And without boost controlled he made 227 wheel hp I believe ... with it was 214. I think both cars would accellerate about the same right now, which would mean they have nearabouts the same horsepower (as I do weigh a little more, especially in the videos)

Again though, I'm not trying to split hairs here or compete. Just show that we're both in the same ball park, and he needs a bigger intercooler. So likely I do as well.

Yours Truly,
Dubbya
 

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Discussion Starter · #44 ·
In reply to EVS ... I agree air to water intercoolers are far better. No argument there, but I also believe according to the post Mark A put in with his technical article, they don't cool any better than and GOOD air to air intercooler, and it would be much cheaper to upgrade your Saab unit with a larger one than switch to AIR/Water.

Yours Truly,
Dubbya

Edit: The BIG advantage of air/water is on rear engine turbo cars where a front mount intercooler is impractical, or on a Subaru boxer setup. Though it is beneficial even in a Saab, just expensive.
 

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Except, Adrian, that we've established that on many Saab models there are difficulties in finding the space for a large air/air intercooler. Which is where the water/air option, eg the Abbott setup on my 900 (and many others) starts to make more sense. Not cheap, but for the increase in
it was well worth it.

Cheers

James
 

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Originally posted by Eric (9-3 Hirsch):
[qb]So your saying 15 inchers are no good?  I guees my car is unsafe with 15 inch S03s on the Ring then?       [/qb][/b]
OK, going down the pedant route... maybe I should have said 65 profile on 15 inchers that are only H or at best v rated with compliant sidewalls... will that do?
 

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Discussion Starter · #48 ·
True James! I hadn't really considered the C900. But when I was thinking about modding my C900 before I got the Viggen, while it's a non turbo, if I had put on a turbocharger it would have probably been a similar water/air unit.

Again though, this conversation about intercoolers all started from a comment on iwantaviggen's car ... which is a 9-3 with the same intercooler I have. Hence the suggestion for a larger FMIC.

Cheers,
Dubbya

edited for spelling
 

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Originally posted by Mark E:
[qb] QUOTE
Originally posted by Eric (9-3 Hirsch):
[qb] So your saying 15 inchers are no good?  I guees my car is unsafe with 15 inch S03s on the Ring then?          [/qb][/b]
OK, going down the pedant route... maybe I should have said 65 profile on 15 inchers that are only H or at best v rated with compliant sidewalls... will that do? [/qb][/b][/quote]I dunno, I found 15"s with cheap 205/55's to be horrible and lacking in "grip-feedback". For me, 16"s didn't yield any perceivable degradation in ride quality.

Anyway, back on topic.

Intercoolers: too much for my budget, if mine gets punctured I MIGHT consider upgrading, but in all likelihood I'd go for a second hand standard unit. Since I'm aiming for near 300 (I'd settle for 280+), am I expecting too much from a standard 9000 IC?

BTW, whatever stanley's car has, one thing I noticed in particular was it's fearsome induction noise. From the rear passenger seats it reminded me of a clip I saw on an evo magazine cover CD, the car on that occaision was an RUF Turbo-R!!
 

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Originally posted by Jason (Mr Torque-Steer):
I dunno, I found 15"s with cheap 205/55's to be horrible and lacking in "grip-feedback". For me, 16"s didn't yield any perceivable degradation in ride quality.[/b]
Cheap, eh? Enough said!
 

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i would just like to say this is a great disscution and is FULL of information!!

if i was to get a new/bigger FMIC i would also logicly upgrade the plastic delivery pipe right?

seeing as it would be really restrictive...

well thats another $300 as ive only seen Abbott sell that....
 

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I have been going over this intercooling business again, and trying to figure out which law of physics is most closely applicable to it. I can only think of Boyle's Law.
His law gives the relationship between pressure and volume if temperature and amount are held constant.

If the volume of an intercooler is increased, the pressure decreases.

If the volume of an intercooler is decreased, the pressure increases.

Why?

Suppose the volume is increased. This means gas molecules have farther to go and they will impact the intercooler walls less often per unit time. This means the gas pressure will be less because there are less molecule impacts per unit time.

If the volume is decreased, the gas molecules have a shorter distance to go, thus striking the walls more often per unit time. This results in pressure being increased because there are more molecule impacts per unit time.

The mathematical form of Boyle's Law is: PV = k

This means that the pressure-volume product will always be the same value if the temperature and amount remain constant. This relationship was what Boyle discovered.

This is an inverse mathematical relationship. As one quantity goes up in the value, the other goes down. So fitting a larger intercooler must at some point in size hit a path of diminishing returns

The effect of temperature is quite obvious to any turbo owner. On those cool December days, that intercooler appears to be so much more efficient
.

Just my 2 cents, for what it's worth..
 

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Too late (and too much wine) to think. But some random thoughts (ramblings) anyway....

But PV/T is also a constant. The P will vary by friction through the system. It may also vary as it cools.

The size of an intercooler can vary in so many ways that the term is surely irrelevant?

After all an intercooler "twice the size" could be twice as long for the same cross section, or have passages that were twice the cross section for the same length, or have twice as many passages for the same length.

The purpose of the intercooler is to cool the air. To do this you need as much tube/fin surface area as possible, which means thin tubes, which means pressure loss. Or lots of thin tubes which means blocked airflow to the radiator.

So as you say, probably a compromise in there somewhere.

A black art?
 

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Discussion Starter · #54 ·
Pressure is controlled by your computer. We were referring to pressure drop. If you were to consider the Bernulli principle the smaller intercooler would flow faster, and the faster flowing air would be LOWER pressure. So really neither of these theories apply completely. (In fact Boyl's Law really can't be applied at all as it applies to a set mass of gas at different volumes and pressures, at least that's what it was intended for anyway)

Anyway, as Mark E pointed out, often fitting a larger intercooler makes the low pressure side of the intercooler (the side that goes to the throttle) increases it's pressure because at the same wastegate setting (the computer controlls it with a certain pulsewidth) since there is less pressure drop, you get more boost.

With regards to cooling I think it's better to think of how much flow is going to move across the intercooler, how long it will take to move across, and how much cooling surface area there is. Find out how much flow your engine will put out at maximum power, and find an intercooler with enough surface area and efficiency to cool it. IMHO the Viggen unit is very good till 200 crank hp, and can handle 230-250 crank hp in colder weather. After that, while it doesn't flow THAT well, cooling is the real issue and it doesn't to that horribly well either. You don't need some monster unit to cool the gasses however. Just maybe a 50% or so larger unit. (small by performance intercooler standards)

My personal choice is the fit something considerably larger there because if you ever go boyond the capacity of your 150% intercooler, you're going to have to upgrade again. So I want to save money in the long run by getting something substantial soon. What I meant by my post waaaaay back when this topic got started in the other thread was that fitting an "overkill" intercooler isn't really going to make some huuuge drop in performance, and if you plan on really making a very fast car it might be beneficial to just get the cooling aspect down now. Others may disagree, but I think the only downside to a large intercooler is cost, and I'd gladly spend $1000 on an intercooler which reduces engine stress (unless it blocks too much radiator flow, or is HUGELY oversized) than spend the same $1000 on a computer upgrade which will put more strain on the engine. Just my personal oppinion though ... I just feel that if my car wants to run 12 psi on a dry hot day, then I don't want MapTun telling it to do otherwise. Maybe once intercooling, exhaust, intake and such are all sorted I'll CONSIEDER upgrading the ECU. Personally I think the stock one is more than adequate.

Yours Truly,
Dubbya (Dubbya being a punn, since like GWB I seem to do everything no one wants me to do. That and, Adrian is a staff member, so I'm not just Adrian, I'm Adrian Dubbya)

edit: Boyle's law is also referred to as a "closed system" principle as it does not apply to systems where mass can flow into and out of the system at will. IE an intercooler.
 

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has anyone considered a 2nd intercooler? this would give an increase in cooling (say a top mounted 2nd one) becuase the heat from the air would be dropped to a much lower figure by the 1st IC, and therefore the 2nd intercooler would not be required to drop the temperature of the air as much as you are wanting the single IC to do. The only thing needed there would be cutom piping and maybe a scoop of some kind to be fabricated (or just rip one off the nearest subaru ) this is only feasable if you have enough room in the engine bay to mount another IC, but it would be worth looking into
 

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Discussion Starter · #56 ·
Certainly an interesting idea. But it might be more fruitfull to weld two intercooler cores together as I suggested earlier. Since that would allow for both to get full frontal cooling. (though that does sound kind of dirty come to think of it )

Yours Truly,
Dubbya
 

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2 stock IC's = twice the pressure drop


2 IC cores welded together with top end bottom tanks along the width of the IC = half the pressure drop (length of the flow path stays the same, only you have twice the # of rows)...
 

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Originally posted by Eric van Spelde:
[qb]2 stock IC's = twice the pressure drop  
 

2 IC cores welded together with top end bottom tanks along the width of the IC = half the pressure drop (length of the flow path stays the same, only you have twice the # of rows)... [/qb][/b]
Liquid cooled pre-cooler plumbed into the regular coolant cicuit as per my post above makes more sense, as additional flow restriction is negligible and it can be inserted in a piece of straight tubework, where rigging up a second IC means additional bends & lengths of tube...
 

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Discussion Starter · #59 ·
lol Actually welding two intercoolers wouldn't make quite twice the pressure drop, but I was referring to two intercoolers side by side, or one on top of the other per the link I supplied waaaay back. Also that might not equate the half the pressure drop either, flow dynamics can sometimes be rather complex.


As for the pre-cooler. I don't think that's feasable IMHO. The coolant never gets below maybe 130 degrees F, trouble is ... for that temperature of water to cool adequatly you'd need something roughly the size of a standard air/water intercooler. Which as per Mark A's post ... is no more efficient in the long run than a air/air intercooler (though a lot more controllable). Also I'm not sure your coolant ever even gets down to 130 degrees. And your intake temps before the intercooler are just over 200 degrees ... so it may not even cool it down enough to make any difference. And since you already have an air/air intercooler, for all that work of plumbing in a pre-cooler you may as well just buy another intercooler. Or you could make a double or "150%" core intercooler for about the same effort which would cool better. You'd just need to have a friend with a TIG welder, and ~$170 for the second core from Saab. That would likely get intake temps down below 20 degree C difference. Then if you still want additional cooling look into water injection. That's what I figure anyway. Keep on Saabin'


Yours Truly,
Dubbya
 

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Originally posted by Adrian W:
[qb] 

As for the pre-cooler.  I don't think that's feasable IMHO.  

Yours Truly,
Dubbya [/qb][/b]
Behr says it is, though. According to them, a simple pre-cooler plumbed into the engine coolant circuit takes care of an intake air temp drop from a typical 120 degrees C to 90 degrees C (before air/air IC), making the total charge air cooling in conjunction with a compact plastic tanked-type IC equal to that of a full air/liquid system, and about 15 deg C better than a typical large-surface all aluminium IC. This is on a six cylinder common rail diesel engine, however, which might run entirely lower coolant temps because of its higher thermal efficiency (I would think it simply runs less coolant, then), I don't know...

As for plumbing in - on a c900 for instance it would be extremely simple, just put it in the turbo-IC pipe run. Resorting to a bigger air/air IC will nearly always mean completely re-doing the pipe runs with the associated cutting and relocating of components (if it were easy, why wouldn't the OE have done it in the first place?).
 
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