pappy92651

Has anyone installed a hood scoop or hood scoops on a 928? If so, what were the results? The intent is to allow cool air to enter the intake and bypass the high temperature zone in the engine bay. I'm finding that it is very difficult to insulate the air box and intake tubes. They heat soak once you stop. A street driven car could benefit greatly.

Tony

http://www.customautotrim.com/hood_scoops/ford_cars.htm

bd0nalds0n

Tony did a beautiful cold air intake for his SC from the fenderwell. 944s run a cold air intake from the fender, too. Why not cut holes where you can't see it rather than where you can?

Garth S

An interesting question! Clearly, the coolest air source is desired, and perhaps the stock inlets above the rad support could be improved upon, perhaps not.
As to heating of the intake air once in the induction system, I cranked a few very crude 'back-of-the- envelope' numbers and came up with a mean residence time ** for a molecule of 'air' to be ~0.12 sec @ a 2500 rpm cruise. When playing harder, averaging ~4000 rpm, that would drop to ~0.07 sec.
Air, being nearly the perfect insulator, is very difficult to exchange heat with - and if the exposure time is anywhere nearly as brief as indicated over a reasonably small heat exchange surface, is there any measurable reduction of the 'delta' temp change of incoming air by further insulating the induction system in N/A cars?
It just strikes me that the residence duration and surface area available are insufficient to have much adverse impact on the density of the charging air: has anyone done some temp probe or dyno work to quantify a gain? Curious, for I do not know.

** mean residence time : time from rad inlet to MAF, two tubes ~3"x30" + airbox = ~0.5ft3. - estimate a bit too high
5l engine @ 2500rpm (4 cycle) ingests ~6250l/min (not allowing for fuel as 14.7:1) =217ft3/min

FlyingDog

There is a Gamballa on eBay with an interesting cold air solution. There are two ducts in the hood right in front of the stock air intakes. I think it's ugly for a street car, but seems like it would work well for race use.

Tony

I can tell you to the .1F what my temp gain is across my system from the airfilter....to the SC inlet..to the SC outlet...to the IC outlet is. One of these days i will get to writing it down and studying it a bit.

Actually on a 45f day a while back i was sucking in 34'F air : )
quess why?
Actually, under boost the air temp at my filter will get below ambient (if the heat of the fender well has already been dissipated by driving around )
My SC not only creates pressure, but on the upstream side creates a lot of suction! Low pressure...temps drops.
let me dig up pic of this principle.
A BIG axial compressor..."got boost"



Other tid bit. Fender mod is ALOT OF WORK. not for the faint of heart after i have BTDT. IMHO, looks and sounds cool and all, but not worth the effort.
Remember, aluminum is good conductor of heat and on a nice sunny day that fender gets pretty warm inside.

wicked944

I've seen a guy that installed air inlets in the prime location like the 968 turbo rs. He races it in the POC races. It looks a little funny at first but after a little looking at its pretty cool and very functional, and as we all are always trying to be, with a very factory race look.

BrianG

There's a 928 done up in a red/white/blue motif that has a decent rendition of a cowl induction scoop. Thanks Dan!

DANdeMAN

This member as done something to is 928
https://rennlist.com/forums/members/15-chris-lockhart.html

perrys4

What kind of gain do you think this will give you? I understand the cooler air with the supercharger and all but wouldnt it have been engineered differently iat the factory if significant gains could be achieved? Just curious.
The neon SRT-4 scoop is designed so it can be made functional by popping out the plastic and using a different airbox lid. Factory did all the routing for the air when they did the hood supports. Pretty cool. Leads a guy to believe they are planning something later huh! Might look at what they did.

pappy92651

Thanks all,

Following the axiom that more air + fuel = more horsepower, lets think about the system as a whole. Just adding a hood scoop might not produce more power. To see any real benefit the intake system, fuel delivery, ignition timing, heads, and exhaust must change. Some of these criteria also apply to S/C and Turbo designs. I saw one configuration that had the windshield intake mod. Alone it did little. After the exhaust system had been modified and the computer had been given a new fuel map a gain of over 40 rwhp was achieved. With intake manifold changes even more can be had.

You are probably wondering where I'm headed with all of this. There is a new motor in the works. If the systems surrounding the new motor cannot support it, the car will not perform well. Thats why I had Greg put new AMG hard parts in my tranny and why I have a stack of new parts waiting to go on the car. The car will be rebuilt or new from nose to tail. I'm building slowly on the work that others have contributed in order to avoid mistakes. I am recording results as I go. Having the ability to log data is paramount.

Tony - Thanks for all the research. Your configuration is very neat and functional. If I were to build an S/C I would follow your lead. Awesome looking engine bay!

Brian - Tony's fender intake makes perfect sense for a S/C. No doubt that you will be exploring this option.

Garth - Thank you for the analysis. Your point regarding temperature analysis is well taken. This is something that I need to do before I proceed.

Flying Dog - Hood scoops can be ugly. Finding a balance between function and form will be interesting. Water ingestion is a serious consideration.

Wicked944 - Hood scoops can work. The question becomes what is actually accomplished by adding them? I'm looking for 2 improvements, cooler air and greater volume of air. We shall see.

Brian G - I have been looking at the Chris Lockhart cowl induction system. It is a consideration and might be one of the most practical solutions.

Daniel G - A definite possibility!

Ron - I may be deluded but my thoughts are that Porsche purposely limited the 928 in order to maintain 911 sales. The 928 made all the right sounds and was released with enough power to make it fun. Beyond that Porsche stopped significant performance efforts after they released the GT. Knowing that the car could perform and hurt 911 sales lead Porsche to a decision. The 944 is another example of a Porsche that 911 enthusiasts wish did not exist. I have even seen hate mail defiling the 930 Turbo! I believe the performance limitation decisions were marketing driven.

perrys4

Wow!! A new car? Very cool. Any time frame for completion? I am sure after following your threads, this is going to be one sweet (and fast) ride. It is obvious you have put a lot of thought, knowledge and experimentation into this. Best of luck. Anxious to hear and see more.
Are you remaking the car in your avatar or did you get a different car to rebuild?

slate blue

The fender is a good choice because it is a very high pressure area. There may be others that are cooler but they also might be low pressure. This area being high pressure is the reason many race cars vent it to reduce lift. You may solve two problems at once.

pappy92651

Ron - The blue car is the target. I'm thinking that all the major work will be completed within 12 months. Moldex crank, Carillo rods, and NickoSil in the block. The headers, X-pipe, and 2.5" tubing will all be Cermakromed. The intake system is the big ??? Since the rest of the car has already been beefed up it's time to make more power. I got my a$$ kicked by a CL55 AMG (483 HP) this week. That must stop. A CL65 AMG (604 HP), perhaps!

Greg - The fender wells are a serious consideration. I saw a graph showing high pressure areas around the car. Among them were the fenders, nose, and top of the windshield. Something to consider.

Adam C

Been there, done that.

Two scoops ducted right into the intake tubes.

No noticeable difference. Save your money. I'm still sore over what it cost to plug them and repaint the hood.