Do you have pics of 911 front splitter/rear diffuser?

[BReyes]

Do you have pics of 911 front splitter/rear diffuser?

[BReyes]

I had a few but my other laptop locked up.

[rattlsnak]

unless you mean CGT, or GT1.... what rear diffuser?

[Jack Olsen]

My own, 'nut job with some aluminum' version:

[rattlsnak]

Jack, all you need now, is a steerable fin in the center, that turns the same way you are turning. Kind of like a rudder, or vertical stabilzer. Now that would carve you around a corner fast!

Have you had thay setup on the track? just curious how it felt,.
Most of the factory ones ive seen on Vipers, Saleens etc, are angled to the outside a little bit, not straight.

[Jack Olsen]

The pictures mask it, slightly, but each section is wider in back than it is in front (the center expands 2.5 inches; each side section expands 1.5 inches).

I've run it on the track, but didn't see a dramatic change in lap times. But other factors were changing at the same time. Ideally, I'd like to put some ride height sensors on the car so my data logger could record actual changes.

I may try it again this coming Wednesday.

[David]

Jack, the front and sides look good, but I believe you'll need to extend the rear diffuser back more so you can increase the radius. I bet you're getting flow separation fairly early in the diffuser so you're not getting the increased air velocity needed to reduce the pressure. JMHO.

[BReyes]

rattlsnak:
Do you have info on CGT, or GT1.... splitter/ rear diffuser. I'm just getting started on 911 splitter

Jack:

You are the man.

125shifter:
Have you drawn on paper what you are saying?

Best wishes for you and yours this holiday season!

[Yellowbird RS]

this is the only rear diffuser I have seen for mid year body



this is the 964 under tray


and the 993 ver.

[David]

Some explaination on the diffuser:
http://www.atlasf1.com/2000/feb16/gray.html

Check out the second to last paragraph for info on flow separation.

[jester911]

This is a valance with splitter I put on my car. No diffuser.

[tom1394racing]

Jack

Your rear diffuser looks really interesting. What impact does it have on the air cooling flow that gets directed straight down across the cylinders? It looks like it would block the cooling flow from exiting under the car and make the engine run hotter. How far forward does it extend?

[tom1394racing]

Another comment on rear diffusers for ground effects on Porsches.

I recall reading somewhere that the Porsche prototypes were always limited in the effectiveness of the rear diffusers because of the boxer engine configuration. The V engine based prototypes they competed against had more room under the car to design effective venturi tunnels and thus always had better rear suction.

Can anyone add anything to this?

[Jack Olsen]

Originally posted by tom1394racing
Your rear diffuser looks really interesting. What impact does it have on the air cooling flow that gets directed straight down across the cylinders? It looks like it would block the cooling flow from exiting under the car and make the engine run hotter. How far forward does it extend?

The not-so-surprising result of my first day of testing was that I didn't feel any tremendous seat-of-the-pants improvement in downforce. Without a wind tunnel for testing, or at least tufts and a camera and/or ride height sensors to measure real effect, the design is/was basically a shot in the dark. My next step (since a wind tunnel is out of the question) is to try videotaping wool tufts and/or installing some sort of ride height sensors to feed data into my DL1 logger.

But the surprising result of the testing day was this: it had no apparent effect on cylinder head temps or engine oil temps. When I run a roof rack with a second set of wheels and tires on it, I see as much as a 40-degree jump in cylinder head temps. With the spoiler and underbody pieces in place, the CHT stayed the same as when they weren't there.

The reason for that is that I have bigger openings than the 964 engine cover had:



The cost of these openings might be further degradation of the diffuser's usefulness. When you're trying to get clear air channels going, it certainly doesn't help much to have an enormous fan shooting air straight down into the mix.

But as I said, the jury is going to be out on the effectiveness of these pieces until I get the ability to meaningfully test (and tweak) them.

[Wil Ferch]

When I was in Germany ( on "asignment") over the summer...I had the oportunity to go to the 'Ring a number of times. One of those visits included the on-site museum. In the restaurant section ( K9handler / Smitty...are you here?) there were a number of cars displayed that competed in some long distance touring car championship...and one car was a black 993 with a rear diffuser ( "Manthay" Racing...or somesuch ??).

Recalling the Jack Olsen thread I crawled around this car quite a bit and found a very normal type diffuser...with 4 -5 vertical "strakes" on the bottomside...and the entire horizontal surface was hugging the body underside real close...but had a small stand-off gap near the front and a larger stand-off gap at the rear. I guess no apparent cooling problems either as this car placed ( as I recal reading) 2nd or such...in a longish 6-24 hour race ( obviously can't recall all the details).....

Wil

[raceman]

jack how do you mount the panels? looks awesome

[BReyes]

Do the strakes/venturis "suck" or is that through ducting in 2005 formula one cars?.

[Kevin Stewart]

[BReyes]

Kevin:
Have you considered what would front splitter pan/floor board rear diffuser would make this car look like viewed from below.

or rather flat out right hander.

What powers your lil cab?

[Kevin Stewart]

BReyes im not sure i understand you, the splitter is a gt2 and goes all the way back to the rack with louvers, the car has a 3.6, im getting ready to take it apart and do the suspension actualy just finish its just been sitting for about two years, Kevin