Both are priced crazy, but forgetting that for a moment, can someone shed some light on the differences for me? At this price, you'd think it would be clear.

Gruppe M: It looks as though it keeps the aft design but does replace the tubes to the front with wider inlets that may / may not introduce engine compartment air. It looks like its intent is to go flush with where the silly snorkel tubes currently go, but not through.
https://mbworld.org/forums/attachmen...1&d=1136589314


Renntech: The aft section looks different... supposedly computer optimized... but what about the intake tubes themselves? Am I misreading this pic, or are those the same stupid restrictive bend out of shape tubes we have now? Do they actually keep the STOCK TUBES?
http://renntechmercedes.com/Show_Eng_Air_V8.html

Help would be appreciated. I may be wrong, but I think the actual intake tubes have to be one of the most restrictive parts of the intake setup, so leaving it stock and paying $3750 to optimize the rear section seems silly. Likewise, the Gruppe M looks clean, but what, if anything, do they do to the rear?



Loren

Don't know about the airboxes.

But I do know your car looks awesome!! Very nice!

FYI! The Gruppe M stuff is top notch. I had one on my 964T.

At $189.75/hp for the Renntech box.....forget it! However, it does look nice.

You know what's REALLY funny? Take that $189.75 and multiply it by 469hp... and bingo, you're at $88992.75 as the cost for our cars. Sound about right?

So, in a twisted way, we've already spent that much per horsepower 469 times already! I wonder if THAT'S HOW THEY CAME UP WITH THE PRICE... they figure we're already used to that cost per hp, so what's another $3750?

Sick trivia...



Loren

Loren,

Ken will give me a description of the airbox in his own words later today. So i will give you a reply later in the evening.

For that money better get Evosport cooling package or K3...

Between the 2 systems, I would say the Renntech is the better system. After doing all the research on all the options available, if I were to purchase one to try out it would be the Renntech box first.

I think there are better designs that can be implemented than these 2 and that is why I am currently working on a new air intake system myself. Both of these 2 systems are still prone to heat soaking because of the long path the air must take before it enters the throttle body.

GruppeM
----------
Pros
-----
- bigger air boxes than stock
- Nice looking carbon fiber


Cons
------
- connections at the back of the air boxes that go to the throttle body remain stock (no increase in diameter). Also would prefer to see a smooth Y-pipe

- the large scoops that sit at the end of the air intake tubes are "loose mounted" behind the grille. There is no physical connection to mate them to the grille which means that hot engine compartment air can enter those scoops

- long air path to throttle body and therefore susceptible to heat soaking

- Suggested 15hp (crank) improvement for $3795 = $253/hp

Renntech
----------
Pros
-----
- larger air boxes than stock
- nice carbon fiber construction
- stock y-pipe is completely removed and gets replaced by their 1-piece air box design. This creates a smooth airflow path right from the air intake tubes to the throttle body.

Cons
-----
- long air path to throttle body and therefore susceptible to heat soaking

- Suggested 25hp (crank) improvement $3795 = $152/hp

I have the Renn Tech airbox on my SL55 but I had it installed at the same time that I had other Renn Tech upgrades performed so it was difficult to tell the difference.

For the hell of it I put the airbox on my wife's "06 E55 to see if I could see any difference. At a standing start I could tell little but when the supercharger engaged there was a fairly significat differenc. It seemed to hit the red line quicker and felt as though it was stronger. Maybe it was my imagination or the fact that for the cost of the airbox it had to be better.

Hey Lou,

I have an idea.. Send me that Renntech airbox and I'll do some testing for you.. I'll even provide some before and after dynos to show the gains..

What a deal. Let's do it twice to make sure.

The guys @ Renntech has given me this information.

I was only kidding around Lou. Didn't you see the smiley at the end of my sentence.. I will buy my own unit if I want one.

I was omly kidding as well. No malice intended.

Do any members have the Renntech air box. If so, what are your thoughts? Adam, have you installed any of these boxes. What are you hearing from customers?

See my earlier post in this thread. It seemed to me that it did feel stronger.

Well, after much thought and friendly advice, I've come to the conclusion it can't help that much. Variability in outside air temperature likely has more of an effect than these boxes. Think about it.

The first thing the air does when it enters your engine is travel through the air filters. From there, it then goes through the "Y" pipe, through the throttle body, into the inlet of the supercharger, where the air is then compressed and discharged towards the intercooler. After the intercooler, the air travels back up to the top of the engine, and back down into the cylinders. All of these pipes, intercooler cores, inlet manifold, etc. represents a restriction. By removing one restriction (the air box for example), but not doing anything to remove the rest of the restrictions further down stream from the air box means that all you're doing is providing a larger volume of air to become restricted by the throttle body, supercharger inlet manifold, etc. This does not equal more HP, since the air is still fighting all of the other restrictions that are further down stream from the air box. It's similar to a restrictor plate in a race car- you can have the freest flowing air box ever made, but if you still have a tiny hole to squeeze all that air through, you won't make any more HP.

So, until I see a more complex setup that addresses all of the intake, I'm putting this one to bed.



Loren

Loren,
I agree with your theory, but are you making one large assumption which is:
If the car is tuned, ie. headers, pulley, ECU etc. isn't there a very good chance that more air could flow through the engine. What if the restriction was at the air box and not within the engine? For example, the last time I went to the track I noticed a gentleman with an older Camaro that had no air filter what so ever on his throttle body. He said that it ran faster without it. What about the results that people are seeing with a simple K&N air filter upgrade that allows more air to flow through. Correct me if I am wrong, but based on your theory and assumptions you would see no improvement what so ever with a K&N air filter upgrade because the bottle neck would lie within the engine not at the airbox. How do you explain the increase in HP & torque that Renntech claims?

Well, having K&N's myself, I know what people are talking about. And I also know the difference between "claims" and proves.

First, let's separate the NA's from our cars: That camero has a much shorter path... a RAM air actually can work. The point of our dual intake tube intensive intercooled super charged cars is obvious: Its like unwinding the arteries in your body... damn that's a long path.

Now, specifically, my question was whether the Renntech or Gruppe M's methodology is better... modifiying the Y or the intake hoses themselves, as each does one OR the other, not both. When you follow our air flow path, there are many other more restrictive bends and paths the air must take following the controversial Y and intake tubes... and each of them are equally restrictive. Opening up one or two is just a piece in a 20 piece puzzle.

That said, the larger the piece, the more of an effect you'll have on the overall path. Air filters are obviously the number one source of resistance in this puzzle... when I moved to the K&Ns, I could HEAR the air getting in a bit better... and the throttle seemed a little faster. Was it me, is this real, am I imagining this? All of us have wondered about that. And that's the first point. If we are still arguing about the most resistant part of the puzzle... air filters are still a hot topic here, and "claims" are tossed around left and right, then exactly how much more releveant would the intakes themselves be? I mean, come on! People here still can't agree on $50 K&Ns versus greens versus stock. AND THOSE items are the most restrictive part. Its all about diminishing returns.

Just for ****s and giggles, do what I did with a quick test: take your air filters completely out. Now pop off the intake tubes too. You're left with an unprotected completely free flowing, shorter system that mathematically exceeds anything either the Renntech or Gruppe M systems can. Forget the arguments about inhaling warm engine air, blah, blah, blah. This is a quick 2 run test done in the cold morning. Let your engine warm up a little bit and THEN close the hood and immediately go for a quick couple of runs. The engine isn't hot enough to generate the kind of heat that would affect all this... and the supercharger hasn't even run yet. What do you notice? Its sounds deeper and seems a teeny bit faster. Its not night and day. Your Renntech kit won't match that setup, so that too is as good as it gets.

That's the second point... that that is the largest most restrictive piece in the stock equation. Every other modification after that will yeild LESS of an impact since there are so many other pieces left (bend, tubes, etc). And since the mild effects of air filter swaps or complete removal are as good as it gets in terms of undoing blockage, any subsequent air path mods will have an even LESS noticable effect than them.

Go look at the air path in our engine and you'll graphically see what I'm talking about. YES there may be some difference... but I suspect its so mild, its irrelevant. After all, if it actually was proven and really did work, two things would be obvious:

1) There would be cheaper intake kits not necessarily made of uber expensive CF, like every other car has and

2) We'd all have them. We don't for a reason... the only kits that maybe have a mild overall affect are very expensive and obviuosly not worth the money, period.

Otherwise all of us mod crazy people would be all over it. If anything, someone should design a ground up PLASTIC or aluminum intake kit ... forget CF... let's concentrate on function here... and redo the whole thing.

Lastly, even if you do get 10hp out of it, what exactly does that mean on a car with 600 hp? Nothing. That doesn't even effect trap speed measurably. As someone once pointed out to my shock, our own superchargers, at engine redline, CONSUME 120hp to spin that fast. Imagine how much horsepower our cars would have if we could enjoy the effects of the supercharger without having the drag of one?

Crazy stuff. I just don't see the real benefits of these systems. That said, I'd get the Gruppe M because it looks better and I hate red.



Loren

LoL Loren, you gave a lengthly explanation and then decided to go with Gruppe M because of the appearance and color.

Exactly... I had to pick between them based on criteria OTHER than function, because that is limited.

Next up, appearance... and the Gruppe M is way better looking.

Of course, I haven't officially bought anything yet. I'm still getting over getting killed by Exotic Warranty...



Loren

..............one practical consideration is that GruppeM is sold by Rennsport.com. I understand that they are the sole distributors of the GruppeM product in North America. Simply put, they are a miserable company to deal with. Expect orders shippped months after they were promised, orders not shipped at all and no returned e-mail or phone calls. Renntech is the opposite.

Ted

Well, then, there you have it... I'm back to no intake at all!



Loren

With GruppeM, you'll lose your engine cover too, coz the intake tubes block it