WHAT A DIFFERENCE!!!!!!!

I live in San Antonio Texas and these last couple of days have been cold (50F). Yesterday has been the first cold day I have driven my car since the restoration. I have a 2.0S with webers and boy is this weather making a difference. I know that it caused by the air density and cold air but I wouldn't have imagined it would make such an impact on performance. Although cold weather sucks (no offense), my car seems to love it. A question for you all. Is the engine trying to tell me theres something wrong that I misadjusted or is it the things I mentioned above that I cannot regulate?

my 71 with 2.2 and webers is also sensitive to weather. Here in NC we get many really humid days and the car runs different than it does on Cooler, dry days. I think the webers are just sensitive to the environment. a slight change in the mixture makes the car run well in either condition.

PS it is just now cooling off. I hope to get home from work early enough to take the car for a spin. The newfound power will be nice.

Jamie
71 911T targa http://www4.ncsu.edu/~jpnovak

Same deal here in Houston, it's been cold for the past two days and my 88 loves it, definate difference although it takes a long time for the oil to get warm.

I have posted a couple of times on the topic of cold air induction and the advantages of ram air. The surge of power you feel now is what I get for free every day. Dynos can't show it but it is real!

So when its 105 deg F, your 'ram air' makes as much difference as a 'normal' induction system experiencing a 50 deg drop in ambient temp??? I think not. What I'm talking about is similar to the difference you would get on a turbo with or without the intercooler for a given ambient temp, i.e. advantages of cooler, DENSER air, not neccessarily more (ram) air. Anyway, I always thought speed cost money!

As for RarlyL8's ram air setup, I can probably say, yes it does have a noticeable effect. Run your engine and let it get up to temp. Have a thermometer inside the engine compartment near where the air is taken in to the induction. It will be higher than the air temp outside of the car when the car is moving. Plus, the air is being forced to some degree through the induction...sort of like a turbo with about 1 psi boost.

So, yes, it does make a difference. Why do you think that Pontiac and the like boast about having a Ram Air induction.

Paul

Here's the deal: A stock air cleaner SUCKS hot air in from inside the engine bay. This air may be well over 175F. The air cleaner assembly also acts as a heat sink, so hot air is being drawn into an oven and then into a VERY hot head.
Forced air induction FORCES ambient temperature air into the hot engine. More air is forced into the intake than would normally occur AND the air is possibly 100F cooler depending on how hot it is under the hood and how hot it is outside.
This IS free horsepower (not a lot, but hey, it's free!)

I thought that a stock 911 (at least the injected ones) actually suck cool air through the big grille on the decklid!

Hint: Take a piece of thin plastic (like the kind you get at the hardware store used to put over furniture, etc. when you are painting the inside of your house) and stick it over the grille while the engine is running. You will be shocked at the ferocity in which cool air gets sucked through the grille.

RarlyL8, you seem passionate about this, it's a logical idea and I'm not going to disagree with you. But I also had a brief e-conversation with Warren in an earlier thread about fan volume. My spec book says 1500 liters per second. I thought this cannot be true, but it is. Warren knew how many liters in a cubic foot, which was still a huge volume.

I can tell you cool, dense air is the REAL DEAL.

Wait a minute. Wait a doggone minute. That huge volume of air is getting sucked into the engine, which means the intake scoop at the end of the air cleaner cover is living in a vacuum. Aren't we all.

Anyway, moving the mouth of this thing into a place of atmospheric pressure, instead of a slight vacuum, might make a big difference. Rarly, is this what you've done, moved the air cleaner mouth outside the engine compartment?

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'83 SC



[This message has been edited by Superman (edited 09-26-2000).]

I remember back in the days I worked on a circle track car, the nights that were cool in the fall produced the fastest lap times.
The heavy air produces more HP. We used an air density meter to help pick our "pill" for the Hilborn injection.

Randy Jones
1971 911

This may be of interest, someone posted it before but these guys talk a bit about cold air induction. I'm still puzzled as to where you would move the inlet on a 911 to take advantage of a so called 'ram air' set up? http://www.electricsupercharger.com/www-electricsupercharger-com/eramdsc.htm

With all this new found power (ha ha), I was challenged last night around 2:30am by a 199? BMW M3. man, was that bastard fast. I was impressed. Of corse the race was initiated by him passing me up , I pass him up, etc etc. My last glance at the tach read 5500rpm in 5gear. I know that probably isn't much for most of you guys with better faster newer porsches but the feeling was great anyway. comment: them webers do get noisy when you open them up. Its just nice to know that at least my car (1972 911) can keep up with or pass soem of the newer sporty cars. I can just imagine it not having much competition in its prime.

Beetos, know anyone who's gotten that E-Ram setup? For $300, I could bolt on 6%....that's 13-14 hp for me. Hmmm. I'd like to hear some non-solicited opinions of the kit.

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Mark Szabo
1986 911 Targa 3.2

Big S - I am trying to spread the word about fresh air. It's free for cryin out loud! No gimmics, and I'll never make a buck on it (ha!). The entire "trick" is to get the inlet to the induction system OUT of the engine compartment and into the outside air. That's as cold as it gets! Everyone who has posted knows that cold dense air increases the efficiency of the "air pump" that is your engine. More in - more out. How you do this depends on the bodywork of your car. I realize that my wing is not that popular with the street car crowd, but it was designed for the racetrack and they wouldn't have that parachute back there if it didn't work! Run a hose from the intake to any spot on the grill or wing that recieves positive pressure from the outside. If you can't RAM the air in at least you can DRAW in cooler air. Anything is a help and it doesn't cost much (hose and clamps). I plan to try this setup with a supercharged or turbo application - I'm pretty sure that this could be key in offsetting detonation when the motor is hot. I'm going to have temp sensors in front and behind the intercooler so I should be able to get good data.
There is another thing that I have noticed but cannot prove - the throttle responce from the CIS seems to be a litle bit better at speed. I think this may be because instead of the motor PULLING air it is being PUSHED into the intake. It is sitting there banging at the door and rushes in when the door starts to open (kind of like my wifes idiot cat). Every little bit helps.

There is actually an equation for how much horsepower increase you will get from cooler denser air. If I remember right it was something like for every 20 degrees you lower the ambient intake temp. equals a six horsepower increase. I will have to find the magazine I read that in (I think it was BMW Power, I also have an 97' M3) and get back to you.

Rarly,

You make me wonder about doing a bit of fiberglass work inside my RS 3.0 tail to route the air from the secondary grille to a 4" outlet, and run a piece of clothes dryer hose to the inlet of my airleaner housing. Of course, it would add about an extra pound back over the bumper, where the engineers hate to ... let's see, if I use balsa wood, that might cut it to half a pound, over that galvanized air outlet piece from the refrigeration supply house ...

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Warren Hall
1973 911S Targa

The Japanese motorcycle engineers have known about ram-air for years--take a look at almost any late model "superbike" out there and you'll see big honkin' scoops somewhere in the headlight region. These have become more and more common as they fight for top speed bragging rights (turbo/supercharging is considered cheating, I guess). Although you can't really measure the benefits on a dyno (unless it's a combination dyno/wind tunnel!), ram-air induction does provide a few percent increase in power. When you're moving fast. And I'm sure there are benefits to pulling in denser ambient-temperature air (which you can measure on a dyno).

I'd put a scoop on my SC if I could figure out how to attractively route it through my Carrera tail without totally butchering it (and interfering with my A/C condenser). Even if the ambient air is 110 degrees out here, that's better than what's under the lid! Plus, whatever gets pulled through the grill has to go past the A/C condenser anyway, which makes it even warmer.

If you want to get really detailed, a smooth path from the scoop to the intake on the air box would benefit the most, because it'll reduce turbulence and give you a nice straight flow right into the box (and the lowest reduction in the air's velocity as it travels down the pipe). Must say though it's been years since my fluid mechanics lectures...

blue

'81 SC Targa

Skeptical Superman says this is worth looking in to. I don't be believe, by the way, that the air get any cooler. I really don't. There is such an enormous volume of air moving past the intake mouth on its way to the 11-blade fan (remember 1500 liter PER SECOND?) that there is no time for this air to heat up. My belief.

On the other hand, I do believe that this idea is good because it places the air intake in a positive pressure environment, instead of a vacuum environment. And air in a vacuum is thinner than air at atmospheric pressure, even if temperature is constant.

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'83 SC

Warren - carbon fiber, that's the ticket. I've got a running joke with a fellow employee who is a motorcycle racing nut. He has carbon fiber bodywork on his bike. I told him he could've saved himself hundreds of dollars by putting down the doughnuts intead.
Big S - The air doesn't get cooler, the source of the intake air is cooler. The air that your motor pulls into the engine bay does not go directly into the intake. It becomes part of the collective, if you will, and all this air is warmed by the engine. The intake pulls in whatever happens to be at the inlet which is warm air. Really hot, humid days exagerate this issue. This is when detonation can rear its ugly head, 90F air is better than +150.
Another option for location is to use a cone-type filter (such as done in supercharging applications) on a stalk that puts the cone next to the grill. You can even fab a shield for it that seals it from the engine.

[This message has been edited by RarlyL8 (edited 09-27-2000).]

Has anyone tried the insulation wraps for the exhaust headers and pipes. It's suppose to keep the engine bay cooling by preventing heat from exhaust pipes excaping into the bay. Any practical expriences?