Dash, I didn't mean to single out Lindsey, but was responding to your comments about them. I believe the same could be said of most of the other tuners out there as well. I am likewise not trying to disparage or endorse any particular vendor on this thread. I am convinced that the tuner market in general has not done proper background work on this particular mod, and its become an old wives tale that its effective, much like the vented nose panel that a bunch of folks sell.

As for why you don't see this more often, I think its application specific, not laziness, and I would assume that they used the following equation as the basis for the design:

Q = m x Cp x DT

Q is the amount of energy transferred
m is the mass flowrate of air through teh intercooler
Cp is the amount of energy that the air will absorb for each degree rise in temp
DT is the temp diff between source and exiting air

Amongst all the things that get factored into the design of an intercooler (any air heat exchanger, actually) will be the number of fins inside it. More fins gets you greater surface area and henceforth, more cooling, but you reach a point of diminishing returns eventually (too many fins and you'll impact flow), so you need to find the optimal point between surface area and flow to get the max Q. In my opinion, its a pretty easy set of equations to figure out how to build the thing. Porsche took the basic constraints that they had to build around, figured out how much overall area they could work with, figured out the practical surface area that would fit inside the overall area, and then computed the flow to match. The concave surface area was the engineering department "showing off" and I personally think that this particular design is *very* innovative.

Don't get me wrong, I believe that there are plenty of things that can be improved on 951's, including the intercooler, but I do not believe the end cap mod being suggested is one of them. Other people disagree with me, and for them, there are plenty of folks that will sell them a modded intercooler. Its all good.

Regards,

 

The real question and only question is, why is the inlet side of the IC concave and with this design it is obvious by looking at my photo's that the front 1/3 (where the air will be the coldest) is pretty much not getting much if any air flow??????? We know by looking at my photo that ther is not anything in the way of this that would force Porsche to make it this way. So the question is simple why is it designed this way? That is the only question, Ther will not be any pressure drop since we have added hardly any extra area. Were talking maybe 1-2 square inches if that with this design we are really just allowing air flow to get to the front of the IC

(When we do the Dyno run we will be having a powerful floor fan placed directly in front of the IC trying to simulate driving down the road and we will be doing it in March in centrial Ohio stilkl pretty cold here)

Cliff 88 951

 

That would be your postulation that the flow is blocked, not mine. If the air is so restricted, how do you explain how the air/fuel mix doesn't get way rich? I can't explain this any more simply that has already been done so, that end cap/so called "restriction" was done to create a pressure drop and optimize flow through the intercooler to achieve optimal exchange of energy over the surface area within it. Porsche DID restrict the performance of the 951, but they did so by limiting boost via software programming. There is NO conspiracy behind the design of the intercooler. The Porsche engineers used tried and true thermodynamic principles to design it, in my opinion.

Feel free to do that dyno test and let us know how it turns out. Keep in mind that dyno testing has a range of accuracy (factors include the design of the machine, how well maintained it is, operator, etc...), so you will need to run about three or four runs with each intercooler and take an average to get an indication of performance, and thats a pretty loose definition at best. One run each won't cut it. Lets see how it shakes out. I also have access to a dyno at a local shop, if anyone wants to ship me a modded intercooler, I will also run some testing (flow, ambient pressure/temp and dyno testing) and report the results and then return it to you. I am very objective about this sort of thing, and I do NOT have an agenda I am trying to defend (even tho I do have an opinion about how I think it will turn out).

Regards,

 

Scott the reson the mixture is consistant, It's called I believe an engine management system. O2 sensor, ECM, etc. I think that the IC is an O.K. design for the 951 in STOCK form but we are not talking about a stock 951. Wolf packs car is modified to a very large degree. The dyno will show if there is any HP increase. Scott if you want to test the IC I will ship it to you for $150 plus shipping after I recieve your core, if it does not work for you I will refund you $$

 

Scott you may have access to a lab to test this design to a greater degree than I have I'm sure of that, I have a dyno and some temp sensors to test the input/output of the charged air. So that being said if this does show some increase it would be nice to know in numbers the differance between the stock one and the modified one. This is a great learning project for everyone involved, lets see what happens next saturday at the dyno. We shall keep the pioneering spirit alive. LOL.Thanks Scott for keeping us on are toes on this project you have brought alot of good points to the table!!

 

No idea. Flow testing removed 7 cfm from a stock flow rate,and a friend of mine ran both the stock and the st. 2 IC with no noticeable seat-of-the-pants difference...if anything,it lost power on top. No bashing intended,I guess the one we had "was a bad one"...I'm sure all the others flow much better.

Is there any other Porsche with the same space constraints and 100-degree inlet air direction change around?

Ease of manufacturing,and most other IC's have no need to "guide" the air like the 951 does (because of space constraints)

Did they? To your eye,maybe. To my flowbench,they didn't. Air does strange things sometimes...a "clear line of view always flows best" doesn't always hold true.

You got it...BTW,if it's written by Corky or A .Graham Bell,I've probably read it more than 10 years ago...

 

Tiz Saturday... hopefully the dyno is running full tilt and the numbers are forthcoming.

 

Skunk Work2, does your flow bench test the IC in the car WITH AIRFLOW OVER AND THROUGH THE CAR, so it is like drivng at speed on the road?

Seems to me, if a dyno test does not have proper simulation of aerodynamic effects of driving at highway speed, then it cannot be very accurate at testing the WHOLE IC system.

After all, a IC is simply a heat exchanger, where ambient cooling air pulls the heat out of the internal charge air. So, efficient flow of cooling air is the other half of the heat exchange equation.

I would like to do tuft tests with small bits of yarn taped to the various location in front of, on, and behind the IC. This, with a small video camera and driving at highway speeds, would tell us what is really happening with IC cooling air flow, especially after it leaves the IC. Meanwhile, I would bet dollars to doughnuts that the stock configuration can be much improved.

 

T Tanner, I'll be happy to watch the results roll in, but I'm not inclined to send you a $150 deposit, in addition to my time AND the cost of using the dyno just to test your product. This has been an interesting discussion, hopefully we'll see some results before long and can make some conclusions.

Its been nice to have a discussion with opposing viewpoints that didn't deteriorate into a flame war. Thanks, guys!

Regards,

 

Thanks Scott, lets se what the dyno shows and maybe I'll ship one to you and have you run tests on it

 

I promise to return it if you do... Ask around, I'm pretty trustworthy.

 

Nope...but I'm not talking cooling efficiency,not cooling flow through the IC from the front of the car, I'm talking flow-through-the-core. It simply doesn't matter if the core cools the air back to ambient if the engine just doesn't get enough of that cool air to make 400+hp.. Like stated from that australian site (ARE),any core that cools almost the same but with the least pressure drop,is the best. Well...if you cannot flow enough,the actual PD through the core (because of restriction,not cooling ability) becomes several psi... hardly effective in any way.That is the main issue with the stock core,not the end tank design. As for why they made it so...I'll see if I can dig up a NACA paper I've read on why that design actually reduces pressure loss at the combined expansion/turn into the tank.

 

The question was asked "why didn't Porsche use this design on other cars?" They DID, on the C2 turbo intercooler. If you look at it, it very closely resembles the "restricted" inlet that the 951 has. Imagine Auto routinely installs this intercooler as an upgrade for 930's and high HP 911 Turbo derivatives that are pushing some MAJOR hp. I was just at Imagine Auto and saw two of these intercoolers, firsthand, and will try to post a picture or two of one sometime this weekend.

Regards,

 

We hit the dyno this past weekend to test the modified IC vs. the stock. The first run was with the stock IC and the second two were with the modified end tank IC. Please forgive my tune as I had not had time to tune this car yet. As you can see we didn't pick up any top end power, but there was an increase in midrange power and spool up time. This is amazing given the fact that this was on a cold day and on a dyno where you don't get the same air flow as you would on the street. I plan to do more test once the car is fully tunned and the air is warmer out. Next time I will do more runs on each so we could get an average of the two for better results. I believe the results will be greater with better conditions. Either way it's worth the $150 to me.

 

I'd suggest that when you do additional runs, that you start and end with the same intercooler, so that you can factor any operating temp changes in the car, otherwise, its hard to determine what is causing differences in numbers on a dyno. The key is to get a large enough sample size in each configuration (four or five pulls with a car thats been warmed up by driving it about ten minutes), and then return for one or two more pulls with the orignal config would probably get you close enough to have meaningful data. Hopefully you have an "in" with the dyno operator, I'd hate to pay per dyno pull for product testing. Any chance of measuring input and exit temps/pressures at the same time (I'm guessing that would be hard to do at a typical dyno shop unless you set up sensors ahead of time on your car so that you can monitor it yourself)?

I'll take torque increases over peak hp increases any day of the week, but I am hard pressed to explain why your second run produced more torque and your last run produced roughly what the first run did, and the second run produced boost earlier than the first or the third. Did the ambient temp drop during the second run? Was the car warmed up when you started, and then cool off during the installation of the intercooler?

Anyone else have an interpretation of the data yet? Good work on getting some real data, altho I am not sure I would make any conclusions just yet, but I am glad that you are happy with it.

Regards,