MarkRobinson

an intercooler can remove up to 100d on a low-boosted 928 if it's sized/efficient enough. Mine was pulling about 80 or so at 5psi (about right). The extra hot air ingested w/o an Intercooler may make the car run warmer, not a good idea on the track. Since the track is full-throttle anyway, I'd rather have same/a little less power with a much cooler charged air temp than the other way around: will buy a bit of anti-heat insurance for those long track days. just my .02.

Imo000

Jim,

Yes, you have and I should have done the calculation then and not after the IC was completed. I remembered what you said and that’s the reason I didn’t chose to over spin the compressor.
Unfortunately if I change the bracket, pulley and some of the plumbing to accommodate for the new SC, there will only be 10% left of the original system. I would have to re do 90% of the work. So might was well say that it will require to build another system. I had the Paxton SC from a previous kit and that’s the only reason I decided to use it. It works well the way it is and I’m very happy with it. Too bad that it can’t be upgraded like some of the newer superchargers. This supercharger is still very good for an entry level system. It would probably work even better on the 4.5L 16V engines. If I don’t included the cost of the SC, it only cost me a few hundred $ to build the system and the car is way faster than any N/A 5L 928, regardless of what bolt-ons are on it. If I ever build another SC system and have a choice of compressors, I will go with a higher boost level unit.


Hacker,

The way your SC is mounted, you don’t have enough room to install this IC. I had to move the radiator forward 1.5” and fabricate 1.5” drop down brackets to lower the radiator. This was the only that the intercooler in/oulets would clear the radiator and they didn’t touch the hood. It’s a little hard to see this in the picture but if you look hard, you’ll see that the radiator is not at the stock location. I’ve fabricated an new bracket for the power steering reservoir cause that had to be slightly moved too.


Swaybar,

The IC needs to be pressure and flow tested to know exactly how well it performs. As I said before, it cools the air to near ambient temperature the question is how much is the real pressure drop. From research I found that the older design (pre bar and plate) intercooler are less efficient BUT they flow better than the bar and plate design. Maybe the IC is too restrictive and needs one more core for a boosted 5L 928. However it could still work very well with other, perhaps, smaller engines.

I don’t agree that a good IC needs to have short runners. In fact I believe the opposite. You need frontal area and volume to dissipate the heat. With short runner the air will not have enough time to cool down. Short runner intercoolers are sufficient for smaller engines that require much less air than a V8. That’s probably why majority of the intercoolers out there are not really big. Yes, the physical size of my intercooler is excessive, but that was due to the dimensions of the original Volvo cores. Don’t confuse my IC with a custom IC, cause that’s not what it is. It’s home made using existing vehicle parts. Just like every other part of my supercharger system.

The inlet and outlets are exactly the same location where they were originally. The cores are original Volvo unit and I’ve only “fused” the two cores together. The end tanks have the same shape as the originals. Unless you want to cut holes in your 928, this is the only way to run the in/outlets of an intercooler. They have to go over the radiator.

Imo000

Yes, you are absolutely right. But there were turbo cars from the factory didn’t have an intercooler and were low psi systems. I had one like that a long time ago and didn’t have any real problems with it until it reached 60K miles (POS Chryslers). After 60K they self destructed, but that’s another matter.

I don't have a condenser in front of the rad. so overheating will not be an issue. I'm not planning on tracking the car either. You points are all valid and correct but they mainly apply in racing conditions.

When you installed your IC, did you measure the boost past the intercooler, how much was the drop and what do you use for a boost controller?


As basic as my system is, I'm still faster than you!

hacker-pschorr

Wrong car - the 81 in my avatar uses an air to water intercooler. My 79 track car will be boosted with an air to air intercooler. There is nothing wrong with running an air to water IC on the track, I just want to cut down on the number of fluids I could possibly spill onto the track.

SwayBar

According to the documentation I've come across, and without going into a lot of detail, your statement is incorrect on several levels; I currently do not have the time to explain why.

However, if you look into the why's and how's, you'll find that the 'rectangular' intercooler picture I linked to earlier is proper intercooler design. It will cool the charge properly, and without appreciable pressure loss, which is it's intended job.

Imo000

Ahhh ok, sorry for the misunderstanding. I recognies the water to air IC in your pictures but then started to think that it was perhaps something else.

For track use an air to air is the best system.

MarkRobinson

"As basic as my system is, I'm still faster than you!"

I've run 12'8's before, i just got a better mph with my 12.9 run

TAREK

Corky Bell seems to agree with Swaybar on that issue. I've posted on the subject in the past, essentially wondering why so many aftermarket manufacturers and tuners (and some factory setups) violate the "book" and the universal principles of good IC design??!! No good answer yet and consequently, at least 50% of the people out there have bad (or less than optimal) IC setups

Imo000

Hmmmm Perhaps you are correct, but still, how come most of the manufacturers don't use these principals?

For exaple, take a look at transport and dump trucks. They have HUGE front mount intercoolers. The IC is as big as the radiator and for whatever reason, they work well. The original Volvo ICs that I used were essentially a smaller version of a big rig intercooler. I've always thought that the rectangle ICs were designed so they can be easily mounted in front of the rad and bellow the bumper support. Maybe this is not the case, I'm not sure anymore.

SwayBar

Imo, I propose a simple picture for you.

Suppose there are two floors in a building, and you are on the first floor, and need to get to the second floor; also, there are many other people who need to do the same in the shortest amount of time possible.

Now suppose that there are 10 long escalators to move people around; that is this intercooler:

http://www.g-force-motorsport.co.uk/...ercoolers.html

Now imagine there is another choice where there are 50 shorter escalators to move those same people around; that is this intercooler:

http://www.procharger.com/images/art...ntercooler.jpg

In this example alone, there are 10 times the amount of channels to move 'people' from one floor to the other; not only that, the distance traveled is much shorter, greatly aleviating the 'pressure' while awaiting to be transported at any given time.

Now to address heat-transfer and those 'short' channels.

First off, there are 10-times the number of available channels for transportation from one side to the other.

More importantly, there is a physical phenomenon where a relatively large percentage of heat is removed in the first couple of inches of the channel; after those first couple of inches, the amount of heat removed compared to those first couple of inches is relatively insignificant. What that means is that you can make those channels as long as you want, but the total temperature-drop versus the shorter ones will not come close to justifying their long length, and that long length equates to pressure drop. The 'people' waiting behind those in the channel must wait until those same people exits to the other side before they too can enter and get cooled.

Sure, a longer channel will remove more heat, but percentage-wise, it's not much after those first couple of inches. But worse than that, the comparitively narrow entrance, and subsequent long passage to the exit-side will cause a significant pressure drop.

That's why it's important to have more channels (..or 'escalators') to funnel the charge through to the exit-side like the ProCharger intercooler example. There is a insignificant pressure-drop as well as maximum heat transfer for the above mentioned reasons.

If you care to investigate, you too will find the same results. Looking at only 'real world' production examples is not a good idea since those designs are subject to bean-counters and not engineers.

Look no further than the ProCharger design!

heinrich

My thoughts also. Where's the radiator??

drnick

how are intercoolers rated, is there a formula for determining the size required for a given application? i dont understand when i see them rated in terms of BHP as surely engine effieciencies enter this equation to?? what size or rating would be required for a GTS engine - air to air..

Imo000

Swaybar,

Thanks for the info, I will read up on it a little more for future projects. I did know about the cooling phenomenon but not the theory behind the cooling runner length and pressure drop.


Heinrich,

The radiator was slightly relocated (1.5” back and 1.5” down) to make room for the IC and for the in/outlets to clear the top of the rad. The picture in this treat makes it hard to see. If you go to the last page of my SC build webpage, you’ll see how this is laid out. The whole package was very compact leaving very little room for anything else. Here is the link: http://norcal928.org/DIYSC/index.htm

Imo000

Ahhhh I seeee......looks better for advertising!!!!! That's not a bad idea.

I just post my shortest ET and call it my best time. Now I'll have to go back an look at the MPH of all my previous runs. I do remember seeing that some of them were, like yours, faster than my 12.8sec. mph.

When you installed your intercooler, did your boost controller compensate for the pressure drop thorugh the IC? What I mean by this is, was your non- intercooled boost the same as the post intercooler pressure? Turbos are much more flexible when it comes to boost controll and it doesn't take much to bring up the boost by a couple of PSIs to make up the loss through the IC.

drnick

mmmmm.... thinking in terms of boosting my GTS engine at say 8psi, if i intercool and see a pressure drop does this simply mean i can turn the boost back up with a smaller pulley (all else being equal)??

how much intercooled boost can a GTS engine handle?