heeman10

Bit of a technical discussion perhaps, I don't know if it's been discussed much before I've recently completed a Zetec Turbo installation in my Mk3 Fiesta, and of course, things are pretty tight. The exhaust manifold and downpipe are heat wrapped, and there is a turbo insulation kit in an aeroplane somewhere over the Atlantic at the moment! I've done about 30 miles in the car, giving it no beans whatsoever, and I'm very wary of the heat under the bonnet when stopping.

The question is; is it better to have rear-facing vents or forward-facing vents? I don't see temps on the move being a problem so much, more when the car's come to a standstill after enthusiastsic driving. I think, because the car will be taking in the majority of air from the front (ie through bumper and under bonnet), forward-facing bonnet vents will create a ram effect which will force cool air into the engine bay. There is (in my mind) already a body of air in the bay, remaining fairly stagnant, as it doesn't have anywhere to move to.

Rear-facing vents would perhaps be encouraging the hot air already in the engine bay to be drawn out, and create a good convection current of sorts. What do people think? A few shots of the car in question, showing how tight the engine bay is, and the bumper cutout:







Your comments are very welcome! I'm leaning towards Cool Louvre-style vents in the front horizontal section of the bonnet at the moment, just above the exhaust and turbo to let it vent when stationary.

Wazzzer

rear facing vents drag the air out on the move and also allow it to rise when stopped, front facing are more for ramming air through something like an intercooler or rad so I don't think these would be very benificial

Andy-R

Ive been monitoring underbonnet thermol temps the past couple of weeks how does 256 degree's sound thats peak temp btw and taken from around the plenum area.

Much as I dislike bonnet raisers I recon they are going to have to be used to aid in the extraction of hot air!

Anonymous

What a fantastic little car

heeman10

I'm wanting to use additional bonnet vents (the car normally has a FRST bonnet on....standard bonnet was just grabbed in haste!) so I don't have to use bonnet blocks. I think they ruin the look of the car That info's interesting though....not the sort of temps you want around the inlet are they?!!

I should mention...that is a Forge recirculating dump valve, not a noisy atmospheric one...and after the first gentle run out I pulled it off and plugged it! Chatter was so much nicer

Wes - My thoughts precisely. Got air moving backward and upwards after entering through the bumper, so forward facing bonnet vents would force air down onto air already rising.

EIL132

Lift the rear of the bonnet, get the hot air out

heeman10

cip - Thanks

EIL132 - I know that's a good way to help things, I just really don't like the look of it I do allow form to follow function with quite a few things, but bonnet blocks will be a bit of a last resort.

Form followed function with the bumper to a degree. I don't like huge cutouts, so this one's a slightly pinched-in version of the majority of big cut-out FRST bumpers:

heeman10

Where would this mystic fan blow anything to though? (sounds bitchy but isn't!) I don't think it's so much a case of getting air in there as getting it out, and getting some good circulation passing through the bay. It gets rammed and sucked in at the front, then hits then engine/bulkead. Heat rises, but it's all sealed in there bar the two little FRST bonnet vents! Because heat rises, it's not so keen to go down and under the car no doubt (only real exit route) so it just hangs around under the bonnet, insulating everything and taking the temps higher.

Anonymous

heat rising isnt really an issue when there is a current of airflow anyway, its only really when the air is fairly static, its a very gentle effect

even a rear facing vent though you may find pushed air down into the vent rather than allowing it up, aerodynamics is SOOO much more complicated than people give it credit for, some really weird things can happen with airflow.

Anonymous

PS

personally i would try removing the flimsy bit of bulkhead so that the air can get between the engine bay and skuttle panel, as that is full of vents anyway.

that way it would still look identical.

heeman10

True about aero effects. If anything though, I'd expect air rushing over the rear-facing louvres to create negative pressure and in effect, positively draw hot air out of the engine bay. The reason I'm being quite careful in my choice of action is that there isn't really much of a current going on IMO, it's all a bit stagnant because of lack of escape routes. Plenty of in-routes, and two fans aiding that, but nothing major supplying an escape to give good airflow.

Anonymous

Thats what you would expect to happen logically, but it often doesnt, and the air goes in the vent at the back, down past the back of the engine and out under the car, and things like that, until you see something in a smoked wind tunnel its hard to imagine some of the things that happen.

But sadly we dont have those sort of facilities at home so have to go for guesswork instead!


BTW, nice job with mounting the cooler so far from the rad, should seriously help to control heat soak

heeman10

Chip - My bulkhead panels carry all the wiring...engine loom and other wiring, it'd be a mess without. Plus they look like this:



Would be a waste to leave them out, plus they keep rain out of the bay and protect the heater blower. Photobucket just deleted my first pic of the thread, how gay!

Rudey - I see what you're saying, would just like to improve things if possible, and give everything an easy time

Anonymous

fook me, that bulkhead is mad, it looks like behind the back seat of a skyline!

heeman10

chip - Very true, I fully understand the mythical behaviour of fluid flow! I study them a bit, but haven't had access to a wind tunnel for a couple of years. I feel you're mistaken about the intercooler/fan gapping! The intercooler bottom pipe sits too low for me to push the cooler any further forward. I'm not 100% convinced my dimensions were followed very strictly when it was made, and it's made things very difficult for me. I was adamant that it sat below the top face of the bumper so I kept a mildly standard look from the front, but I've really had to work to make it fit, and the same problem is stopping me from moving it forward.



Hard to see from that pic really. I've lost a few pics on Photobucket, but the backs of the fans are no more than 1mm off the front face of the radiator, which will not be helping things.

heeman10

Haha what you on about?! It's chromed, so looks a bit more busy than it is because everything's reflected!

Anonymous

Ah its just the angle in that first picture then, looks like there is about 6" between them!

heeman10

Ah right, nope, just standard layout See what I mean about the issue I'd have if I just removed the panels though?

I've fixed the missing pic at the top of this thread now....you can sort of see how close the fans are the rad. I suppose there's a fairrrly ok gap between the rad and cooler.

Sadly the car was only on the road for one night because the gearbox was utterly unuseable. The diff had torn itself to bits, so the car is now over the pit at home:



Diesel box going in tomorrow just to get through MOT and mapping at MSD, then Stage 1 Bernie box going in when it's built

Anonymous

Thats the best thing about cars breaking, good excuse to build them back better than ever

looks a good sized garage that

heeman10

I did nearly all the work in that smaller garage above (pic showing front of car with number plate on) but my dad's let me use the big shed to swap the boxes over, as it's the quiet season for his business at the mo Can't wait to get it all back together and go down to MSD! Couple more pics, as I haven't shown any of it on PF really, I'm a fiestaturbo.com man

It had a 150bhp Mondeo TDI engine in last year, hence the TDI badge still being on it:











I won't turn this into a build thread, but just a few bits of what I've done anyway

heeman10

Me too! Hope Stu's feeling kind about slotting me in somewhere Missed the mapping session because of the gearbox issue. Fingers crossed, will put some pics and things up in the gallery when I've seen him

Uncle Henry

google is your friend

http://autospeed.drive.com.au/cms/A_2162/article.html

heeman10

Linky no worky

heeman10

It worked after a few goes. Could only read the first few lines, then they try to make you buy stuff! I was thinking of putting the vents closer to the front of the bonnet anyway, something like the two crappy mock-ups below (it's hard to draw louvres in MS Paint! )





Any opinions? Preferences?

RSeb

works ok for me

RSeb

looks ok just remember when you place em that ur gonna get water in there when it rains, replaced the vents on my erst with louvres and was forever having to dry out the air filter!!!

heeman10

Air filter's tucked down to the bottom left of this pic, in the cool air stream between the radiator and upright of the chassis:



Should be ok there methinks! The bracing under the bonnet looks as though it may get in the way of putting louvres in where I want

Rippers

This also interests me and I did some research myself and I was told by a great tuner whom I trust that the Fiesta was designed to flow the air through the front and from the vents on the bonnet and then under the car.. and basically the rear bulk head your talking about has a rubber seal on it for a purpose and thats to stop air leaking out from the top and affecting the way the air flows.
In his opinion a way for improving this type of air flow was to have an under engine sheild. so the air direction was flowed better through the front hole of the bumper then out again under the car. The only Fiesta I've seen with this done was Gadgets (funny he uses the same tuner) alfa blue one, if you remember the feature there is a shot of under the front of the car and you can see alloy cheque plate covering a lot of the front underneath the engine.. that wasn't done for looks Will be considering a simluar mod.
I don't quite understand how it works but its to do with a airflow and different streams of air hitting each other, But basically the alloy blocks don't only make you car look like a chav mobile thats had a small front end crash but also unsets these aerodynamics. To be fair the only way they would help is when the car is stationary and the hot air has a chance to rise.
Hope this makes sense??

heeman10

Yeah I do remember Gadget's chequerplate, thought he was just getting ready for some slag action!! The latest idea is this:



as inspired by the 2.0 T16 Group B rally car. Simple cut and fold, which would change the air flow characteristics you're talking about. It would encourage air to flow through the cooler/radiator and sweep straight up and out of the bonnet and over the car. I'm fairly sure it would benefit the coolant temps, and at a standstill, with the cutout positioned correctly, would let the exhaust vent directly to atmosphere.

The vent looks a bit extreme there, but could be smaller with smoother edges, with the two triangular gaps (left when the tongue is folded down) covered with plate metal. What do you think?

SS1

iTrader: (3)

FOOK THEM PICS
AA MAN would eat HIS HAT

Wazzzer

looks like a small RS200 vent

heeman10

What do you mean? Don't AA men like poor photoshopping or something??

Wes - Yeah, it's sort of like the RS200 vent, but is closer to the 205 T16 vent. Can't make my mind up, particularly when it comes to rain water running into it etc.

Rippers

My Kevla bonnet doesn't have any vents

heeman10

I've been trying to rein the spending in a bit of late, so Kevlar won't be on my list! Think I'll just see how things go once the insulation kit for the compressor housing has turned up and I've put the FRST bonnet back on. Cheers for your input Paul, and I hope to see you around the place over summer! Catch you on FT probably

Brookesy

How about removing 2 spoylights and fitting ccol air ducts

heeman10

I'm focusing on getting air OUT of the engine bay as opposed to in really, I think the bumper should be letting more than enough in there. Also I'm trying to keep the looks of the car as standard as possible, sorrrt of street sleeper style, ie not giving away too much. I know it's no fire-breathing 400bhp monster, but still, I'd like it to look close to Ford's design