Dash01

I agree, from a scientific validation standpoint, there should ideally be larger 'before and after' sample sizes, and methods to isolate the one variable (end-cap modification) tested.

That said, given the time, resources, and money these fine Rennlisters have already spent, I am very grateful to them for sharing their findings with us, and urge them to continue their research.

To save research money, maybe we can come up with a simple, cheaper way to test 'before and after' mods of the IC end-cap without need for expensive dyno runs.

In particular, such mods should be to enhance through-flow of charge air at the front ~1/3 of the IC, because that's where cooling air reportedly does the most good in cooling the charge air.

User 41221

Dash, if you can, try to take a look at the C2 intercooler (the Porsche 993 turbo unit). You'll see the same thing as our intercooler, with respect to the inlet. I'd like to get your thoughts on it after you look at that one. To me, it looks like Porsches engineers are using this design on purpose, but I would like to get some different perspectives on it.

I liked your water flow test idea, by the way, and think that would be interesting to dop at some point in time.

Regards,

Dash01

"Dash, if you can, try to take a look at the C2 intercooler (the Porsche 993 turbo unit). You'll see the same thing as our intercooler, with respect to the inlet. I'd like to get your thoughts on it after you look at that one. To me, it looks like Porsches engineers are using this design on purpose, but I would like to get some different perspectives on it.""

Scott, I'll do that ASAP. Meanwhile, I spent the weekend reading all sorts of NACA and other cites on intercooler and heat exchanger design, and found the concave/wedge-shaped IC end cap has scientific merit. If you'll PM me your email address, I'll try and dig up (from a long list) the cite and send it to you.

Based on that, on the posted picture no. 2 (which see) of the cut off IC end cap, and on the post today of the dyno test, here's what I preliminarily think may be the story on the stock IC: Porsche did the wedge shaped end cap per research I found, and wedges work well if done correctly. However, if you look at pic. no. 2 posted on Rennlist last week, you will see the wedge-shaped IC endcap would only allow a tiny crack for charge air to reach the front ~1/3 of the IC. Some experts (and I'm not one of them, BTW) say the front part of the IC (since it gets the coolest cooling air) does most of the cooling. Encountering such a narrow slit to reach the front part of the IC, the charge air simply takes the path of least resistance and goes through the middle of the IC, bypassing the cooler (best) front part. In other words, I suspect our stock IC may be too restrictive towards the front, and when modified per Wolf Pack et al, it works better per the dyno results posted today.

So, per my layman's theory, it's not just the flow rate through the IC, but rather what's most critical is the flow rate through the cooler front ~1/3 of the IC. If I'm basically correct on this, it would be interesting to test my theory by cleanly cutting off the entire wedge endcap, installing a shim around its circumference to raise the wedge another +/- ~1/4" (?) off the core, then putting the wedge endcap back on. In other words, enlarge the internal gap between endcap and core to enhance charge air flow through the front of the IC.

Whatdya think?

PorscheDoc

Scott, the C2 intercooler is off the 965. The 993TT uses a completely different setup.

kasturbo

There was a bit of cool down as we installed the intercooler, but it wasn't any cooler then before we made the first run as I was the second car on. I was most impressed with the 3rd run because the spoolup was faster and this was on a warmer engine then the first two runs.

PorscheDoc

And like scott mentioned (which is hard when you are paying to use someone's dyno), you really need to do 4-5 pulls with the same intercooler, so you can see what effect the heat soak has on the engine. Then test the 2nd intercooler in the same conditions on a different day, or later in the day when the car has had time to cool....i know not as easy as it sounds depending on schedules and such. I have seen Audi's with their highly inefficient intercoolers drop 30-40hp to the rear wheels (modded cars running about 350 crank) by the 3rd and 4th runs due to heat soak (their intercoolers are off in the drivers side of the bumper cover). On the other hand, I have run my 951 on the dyno in 90 degree weather 6-8 runs or more in a short amount of time (for various other testing/tuning), and have never seen a drop in horsepower like that. Rarely do you see a drop over 3-5hp, even when the car is getting beat on constantly. Of course i don't spend much time on the dyno, lol

kasturbo

Agree, next test will involve more dyno runs and hopefully temp. readouts.

PorscheDoc

What type of fan setup does the dyno have to stimulate a headwind, and feed air for the intercooler? We use a large fan that stimulates roughly a 60mph headwind. Proper airflow is crucial when doing this type of a test. If there is no airflow feeding the front of the car, you are not really simulating what would happen to the performance under road conditions.

jimbo1111

The diffusers are there to maintain equal static pressure before the charged air enters the IC. Removing the tapered end tank will divert the air to the top 50% of the IC. This will hurt efficiency because most of the air will flow through the path of leased resistance. Yes eventually there will be enough forced air in front of the IC to force the air evenly but by than it's time for an upgrade because the IC has become the restriction.

Let assume there is 400 cfm at the neck. I'm not sure how many rows the IC has so lets say 10. Let assume each row can flow 40 cfm's. For the charge air to flow evenly. Pressure has to be maintained on the header. How is this done? Simple. After every 40 cfm take off. The neck size is reduced to maintain equal static pressure for the next take off. This allows every row to flow the same amount of air.

User 41221

Hey Karl, can you post that pic of the C2 intercooler?

Regards,

kasturbo

There were two fans used on the dyno. I have no idea how much air flow they could push.

PorscheDoc

Here is the C2 intercooler off the 965 that scott was talking about.

965:


Aftermarket 930:




Stock 930:

TurboTommy

Sorry to chime in late in this thread.
I can't believe you guys are making such a big deal about this IC topic.
I've done alot of research and reading about this issue and I'm sorry to relate the cold hard fact (especially to those well meaning busy beavers) that you ain't gonna get any hp gains by attempting to alter the stock IC. Gains will only be realized with physically a bigger core (on a mildly chipped car it wouldn't even do much).
The notion that any little temp decrease you might achieve by playing around with this, will result in power increase, is false. Slight differences in IC exit temps have little effect, because downstream the injected/atomized fuel will have a cooling/equalizing effect which nullify small gains in IC cooling.
All this talk about the first third of the front core isn't doing any cooling (or whatever else was said, etc, etc), is just splittin' hairs, and by the time the intake valve closes it means nothing.
If Porsche engineering department were reading this, they'd be peein' their pants for laughter.

sh944; sorry man; some of your input, here, needs to be straightened out:
An IC system does not NEED pressure drop in order to achieve decreases in temps. It is just an enherent side effect of trying to get the heat energy out of the charge air. In fact, the least amount of pressure drop is what's desired. This is not a closed system and PV=nRT does not apply.
Your statement about why not going rich air/fuel, or whatever, has nothing to do with IC restriction. The air measuring device of your engine management system will "see" if there's more flow or less flow and fuel will be injected accordingly.

User 41221

Thanks for the feedback, Tommy. You and I share the same opinion on the subject and I appreciate your corrections, but all I was trying to point out was exactly what you stated - that pressure and temp are related. Also, I am well aware that the engine management system will make the correction to the air/fuel mix, but it is limited in it range of correction, and I was trying to get the point across that IF the intercooler was as big a restriction as was being suggested by some folks here, it would have to show up as a rich condition since the engine would have to be starved for air.

With regard to other statements, feel free to correct me as needed, but some of the comments I have made were more for illustrative reasons than for engineering support. Advice from anyone with better information or just better ways to say it, is always welcome!

Regards,

kasturbo

No offense, but until either of you can back up your claims with numbers, then your opinions are just that. I could give a rats hoot why you or the next guy doesn't think it works, but until you prove it with actual numbers, why would anyone believe you vs. the guy who says it does work.

Is it a FACT that cooler air makes more hp? Is it a FACT that the front part of the IC is the coldest? Is it a FACT the the current design of the IC restricts air to the coolest part of the IC. Yes these are all FACTS. Lindsey provides data to support these FACTS. Where is yours to prove them wrong. If you don't have them, then why are you posting?

Is it a huge increase in HP. Maybe not, but as Tab has said from the begining of this post, the first few hp are easy to get, it's the last couple that you will pay for.