carrera style badge panel

[Indi9xx]

Pete is spot on, the full under-tray, including the metal bit is important to get the most out of the ground effect.

Having said that, above 100mph you can often tell if a car is missing the plastic one, feels almost like the nose is pointing skyward and light.

Amazing that such a simple flimsy plastic part can keep the nose down on a 944 turbo, but its more to do with how the air is controlled and turbulence is avoided, than the tray actually forcing air in such a way to pull the nose down.

Recently had some flying lessons at Bournemouth airport, while talking in the club bar it turned out that the guy I was talking to was a previous red arrows pilot, anyway, we were talking about aerodynamics, and he explained that the red arrows have something that looks like a toblarone package stuck to the leading edge of each wing... the reason is because apparently as the plane hits a certain speed before its stall speed, the small device makes the whole plane shake as a warning.

 

[944 man]

ORIGINAL: Indi9xx

Here you go, sorry the car is a little dusty in the picture.

Thanks Jon. How critical is size and position? If I bought a pair of slightly larger vents from D9 and fitted them in approximetely that position would they work, and also: would they remove the left that my car suffers from due to the missing undertray and aero mouldings?


Simon

 

[944 man]

PS Im not mad about the CanCan! []

 

[j4mou]

The look a little like rs turbo vents, may work better too as they were designed for the same thing.

 

[TTM]

That would be Ben's ex 3.2 then? Should such ridiculous outlets bring such benefits?

Not sure I get the part about the standard intercooler and its efficiency - air slows down because the ducting becomes wider but even on the "upgraded" unit it remains a "problem"?

 

[JamesO]

ORIGINAL: 944 man

ORIGINAL: Indi9xx



Thanks Jon. How critical is size and position? If I bought a pair of slightly larger vents from D9 and fitted them in approximetely that position would they work, and also: would they remove the left that my car suffers from due to the missing undertray and aero mouldings?


Simon

Mine doesn't lift and feels very stable at speed. It has the bat wing, no undertrays, arch liners or plastic trims on the wings. What it also doesn't have is driving/foglamps in the bumper, just two big holes which I assume by some freak of luck help.

 

[944Scott]

I have the batwing and the ali tray but I dont think I have the secondary piece of undertray, anybody got a picutre.

Surely if using such a panel if you block off the feed from the PU slit and box in the intercooler behind the new vents you will create a ram air effect and remove any vortex's

What was the acutal set up on the 924 ?

Sorry but them bonnet vents look real cheesy, I never thought they looked good on an RS Turbo let alone a 944.

 

[944 man]

The 924 Turbo didnt have an intercooler. The 924 Carrera GT had a top mount and Skunk Werks specials had a vertically mounted intercooler in the front.

 

[944 man]

I dont believe that theyre Ford parts and I doubt that that is what James meant. By RS Turbo I suspect he was referring to the 'Turbo RS' vents sold by D9, although I believe that these are substantially larger.

Id still like to fit their RS replica bonnet intercooler vent, but I have little idea as to whether itll fit/work properly - I could do with a 3.0l 8v turbocharged 968 to compare mine with...

 

[JamesO]

Would have thought you would need to re-locate the intake for the 968 intercooler vent to work (if its the one I'm thinking of).

 

[Indi9xx]

For anyone with a full undertray, take it out for a blast up to about 125 mph and watch really closely at the edges of the bonnet where it meets the front wings... Then remove the undertray and do the same thing, ideally get a friend to drive, so you can watch it carefully (Also it will be his points if you get spotted)

We first noticed it when setting up boost on a private (ahem) road on tuned cars, taking them through 4th on full power and into 5th gear looking for boost spikes, we used to go out with two of us in the car, one to drive, one to monitor boost and AFR, and we started to really notice the difference of having an a full undertray fitted or not, as sometimes we would run with or without an undertray depending on what we were doing and at what point we were doing it.

What we tended to notice was the front end feeling looser at speed, but most dramatic (if you are looking for it) was the bonnet lifting or bowing in the middle along the edge with the wings.

Try it for yourself, it is quite an eye opener of what is going on under the hood.

 

[Indi9xx]

Vent position and size took a lot of work to get the right size and position to get what we wanted. Luckily bonnets are something we never get asked for, so every car I have ever scrapped has ended up with bonnets being stacked up when we should have just chucked them.

We did actually try vents from the Escort RS Turbo, Fiesta RS Turbo, Escort cosworth, sierra cosworth and various others, we even tried having bonnets pressed with louvres.

We recorded air pressure inside the engine bay during testing, as well as taped tufts of wool inside, in front, behind and either side of the vents to see what effect it seemed to have on airflow through and around the vents.

To big a vent seemed to cause slightly negative air pressure in the engine bay (very slight) at speed, which considering the car like many we work on had an engine bay mounted air filter, seemed counter productive to performance.

Positioning wise, we chose in the end to have the vents between the strut tops and the firewall to help promote air to flow through the front of the car (radiator and intercooler etc), through the engine bay, over the exhaust manifold and turbo on the other side, and out (as much as you can)

It seems to have done the trick, the car no longer melts plastic bits in the engine bay and with the engine idling after a hard run you can feel the extra heat escaping from the vents.

From all the testing we did, we found the Sierra Cosworth vents were too big, we wanted to keep them as small as was effective. The D9 ones seem to be massive, which I would be tempted to say is possibly a drawback.

Its never going to be viable to sell this as a product, it just takes too much work to modify the bonnet and make the vents. But it is the kind of thing we will probably keep up our sleeve for the more radically tuned cars where serious under body heat starts to be an issue.

Which admittedly, this car only seemed to have a critical issue on track days, possibly due to being run hard and then pulling into the pits and either idling or being shut down, causing a lot of heat soak without airflow, and with the vents its easier for the heat to convect upwards and outwards.

But on the move it certainly should help airflow through the engine bay to be where you want it and directing some of it above the car taking heat with it, rather than it heading downwards under the car and allowing heat to be almost trapped at the top of the engine bay.

 

[Indi9xx]

The intercooler issue that someone asked about.

The standard intercooler, the lindsay intercooler and our intercooler all use the same fin spacing, the closer you get to 1:1 ratio of front of car opening (leading to intercooler) to the frontal area of the intercooler you get, the closer the airspeed flowing through the intercooler will be to the road speed of the car. Beyond a certain airspeed, the turbulance caused at the leading edge of the fins reduces the ability of the fins to flow air, so even though the airspeed goes up, along with it the pressure on the front of the intercooler, the actually volume of cooling air goes down.

At short distances on boost, the thermal mass of the intercooler acts like a heat soak, so more heat is being absorbed into the intercoolers mass from the intake charge than the intercooler can release into the cooling air, not too much of a problem because the car will not be on boost for much of the time, even driving at fast speeds on a track, so during the off boost periods the heat soaked into the intercooler mass can continue to be released into the cooling airflow... However at high speeds, such as being above 140 mph for any time at all, the intercooler after a short time will only be able to absorb as much heat from the charge, as it can release into the cooling air, which is when things get critical.. Especially if you have increased the airlfow into the badge panel, because this is exactly the same kinds of speeds where due to the reasons above you will have reduced the amount of cooling air that the intercooler will be able to flow.

The other problem is beyond a certain air speed, you create a boundary layer on the fins of the intercooler, which further reduces the ability of incoming air to cool them down.

Hopefully this answers everyones questions.

 

[TTM]

I know this will depend on compressor efficiency and on the location of the cone filter, but how would you rate an intercooler set up that makes for intake air temps that do not exceed ambiant air temp by more than 25°C?

 

[Hilux]

I have limited experience of this however when I was in the Westfield club there were all sorts of thoughts about reducing underbonnet air resistance and additional underbonnet temperature reduction.

Cateringvans and Westfield owners simply cut slots and installed grilles (usually at the rear of the bonnet/engine cover below the windscreen) but ironically they did not work as air turbulence before the screen actually created a positive pressure and the vents were ineffective. Instead they found that opening up the rear of the front lower body panel was more effective. This is true of many cars. Bonnet vent positions and sizes are more critical than one might realise.

Equally, placing intercoolers and oil coolers in the nose cone vents alongside radiators created all sorts of problems as the airflow was blocked or became ineffective so Johns research is invaluable

Regarding the undertray`s, all I can add is that if you do a constant 155mph (on German Autobahn`s) the really noticeable downforce that kicks in around 130mph is amazing, the car actually sits down, you can actually feel the downforce and the steering getting heavy as the car is stuck to the tarmac. You then realise the research that goes into the cars and why little bits of plastic skirts and undertrays are there on Turbo`s.

 

[PSH]

ORIGINAL: Hilux


Regarding the undertray`s, all I can add is that if you do a constant 155mph (on German Autobahn`s) the really noticeable downforce that kicks in around 130mph is amazing, the car actually sits down, you can actually feel the downforce and the steering getting heavy as the car is stuck to the tarmac. You then realise the research that goes into the cars and why little bits of plastic skirts and undertrays are there on Turbo`s.

Having driven at these speeds and higher I can testify to Paul's comments, even at very high speed the car is sure footed and in-stills total confidence in it's ability not to loose contact with the ground. I can honestly say that I have never felt as safe in any other car as I do in the 944T at high speed and I have driven some exotic cars in the past.

I've included a picture of the two components that some may not be familiar with due to them being lost over time, naturally these items off of my car will be cleaned and polished before refitting to the car, well the rest of the car will have to match the engine won't it?...

Pete

 

[DavidL]

That's real shame - I had every intention of fitting the 924style as I rather like it.
Ah well.

 

[T3rra]

Maybe still fit it 4 the look, but use some ducting 2 make the air flow usefull? But 4 what?

 

[TTM]

I don't think the vents on the original 924 panel were even actually functional?

 

[T3rra]

Maybe just styling, but was the idea 2 flow air though then out the vent in bonnet?