I have a modded 500hp plus sapphire and now have a 2wd standard bonnet as opposed to the 4wd vented bonnet I was running previously.
Do I really need bonnet vents to release the extra heat from a big turbo?
Or will the non vented bonnet be fine?
I will heatshield the underside of the bonnet and was even contemplating jacking up and spacing the rear of the bonnet on the hinges (I quite like that look tbh)

Cheers Paul

 

I think you will be fine. You will soon know though if you monitor the intake and engine temps.

I did raise the back of my 205 bonnet as I do want vents but haven't found a satisfactory way to do it yet as the bonnet is carbon fibre and I don't want to risk a Ł1500 bonnet and get it wrong.

I don't mind the raised back look but I have had some negative comments when some people look at the car....so not everyone's cuppa but I think thats more to do with the amount of standard 1.2 saxo's and clios do it cos fast n furious innit.

 

I had the raised bonnet blocks on my RS Turbo for a while and was constantly being told at traffic lights my bonnet was open,which got annoying. My cossie is 2wd and now has 4wd bonnet and I'd say at your level of tune your best having the vents to be honest.

 

Yes, I have had that too.

 

I have heard of cossies warping bonnets before but that may of been ones with no heat shielding before. AjamesC off here runs a big hp 2wd on a non vented bonnet see if he has any issues.

I'm sure the escort cossie vents make a good difference but don't know about saff

 

What no bonnet vents ban him...

I have no data to prove but anything that helps control engine bay temps is a good thing imo and lets face it bonnet vents are cool.

 

Only thing that annoys me about the bonnet vents is when u wash the car or it rains it makes a right old mess but I wouldn't do without them to let the heat out

 

Vents in a bonnet will defo help with getting the hot air out of the engine bay.

 

Never had them on mine at 500 and I'll not at 650. Never had issues with temp or paint damage to the bonnet due to heat. Mine did have the under bonnet heat deadening off a normal non vented bonnet as well
I really don't like the vents and certainly wouldn't fit a non rwd bonnet on mine

 

That's alright bonnet vents are probably to cool for you anyway

 

Ha ha always been an original fan I like to go against the crowd too many in the vents crowd

 

ajamesc. I am suprised that you have never had any engine bay heat build up problems, your cooling system, fans etc must be working overtime on a hot day when you are giving it some beans!

 

Temp gauge never moved charge air temps always good.
Will we see when it's back with 650

 

Its your personal choice but the other day when I had been out in mine which is only 450bhp and put it back in the garage I could feel the heat coming out of the bonnet vents. With 650bhp yours will probably be generating a lot more heat and I think what ever can be done to disperse it out of the engine bay the better.
Hope it all works out ok.

 

Like I say mate never had an issue as it was. When it's back we will see. Only way id ever change to a vented bonnet is if mark said you need bonnet vents.
But to be fair if there was a heat issue under my bonnet as it was you would see it in the temp gauge or damage to the paint on the bonnet
I had an oil temp gauge as well and never see that hot enough to worry about

 

I think to be honest (and just my opinion) it was as much to do with styling as it was cooling when Ford designed them with vents, seen plenty of cars running good power without them (sleepers are an obvious first thought).
Raising the bonnet can actually hinder cooling and airflow so I wouldn't do that.

 

Time will tell, once you are driving hard with your new 650 bhp upgrade you will soon find out if there are any engine bay heat issues.
What dont you like about vented bonnets?

 

It's more for me I like mine with the rwd lights and bonnet as that's how it came. Guess I just like the more plain look. Like the light I definitely like the orange indicators better

 

I can monitor all the temps as I have a secs monitor fitted so that's not a problem.
Will be a while till the cars up and running again anyway.

I don't mind the raised bonnet look.
I had it on my old rst too.
I know what you mean about people hating it though but comments on my own car from other people don't really bother me

Cheers Paul

 

Me too ha ha.

Cheers Paul

 

So your gonna stay with the 2wd bonnet?

Will you heat protect the underside of it?

Ceramic coat the manifold etc?

Cheers Paul

 

Hinder it? Really?

How comes?

Cheers Paul

 

Mine has a Ford sound deadening on it off a non cosworth sierra. But like I say mine never got hot at 500 with its gt3076. Oil / water temps good. When it's back I guess we will see. But I'd never change un less I was told I need to.
As it go's back together I will compartment the air filter area though and fit a cold air hose to direct air to it

 

When a car is designed the cooling system and air flow characteristics of the engine bay are all modelled/tested with the bonnet fully closed... Raising the back ruins all of this and can result in higher temps or at best the same.

 

I too was gonn ado that with the air filter or run it beneath the inner wing behind the bumper

 

Interesting.

Maybe just see what temps I'm getting with the bonnet sat normally then go from there then

Cheers Paul

 

It COULD also allow the air out the back of the bonnet and aid cooling. I can certainly see hot air (waves) at the rear of my bonnet so I know heat is getting out and my car doesn't overheat like it used to but that was more down to the header design that has now changed.

It all depends on the application. Car manufacturers have the ability to amend the design at that stage until it works, a manufacturer is unlikely to resort to lifting the back of a bonnet. Just because they work to their model it doesn't mean it wouldn't work but I can also see that it MAY cause issues on some cars.

The abarth 500 had the boot open the whole time for cooling and some 911's had different "boot" lid arrangements for aero and cooling.

 

I can feel the heat off mine too when i put the cossie back in the garage. I always open the bonnet and leave it open. When yougo backin the garage about an hour later i can feel the heat off the cossie init.

 

I have my ITG cone filter inside a Spec-R group A airbox and I think its a good idea.


Has function and style and also prevents any debris being sucked into the filter.

 

Heat will definitely exit the bay with the bonnet raised, but what makes a car overheat is not engine bay temps, it's coolant temps... raising the bonnet can disrupt the flow of air through the radiator and this is of course what keeps the engine cool and your temperature gauge where it should be.

But you're totally correct when you say it may work on some cars and not others, I've witnessed a CAD simulation using a BMW E30 and then later tested in a wind tunnel and it made it worse but that's not to say it does for every car.... Just something to bare in mind.

Oh and I've had RST's with raised bonnets (including my own briefly) where both coolant and intake air temps where very high compared to it being fully closed.

 

I always liked your engine bay and love the inlet from filter. Is it chromed or polished alloy? In the pic there is a hose off mid way, I assume that is mid progress as unfiltered air?

 

Polished alloy from Spec-R. There was a small hose but not sure why, but it makes more power with it off. Had no issues with it.

 

Do a Topspeed run with 35 sec at 100% WOT then report back Andy. You will have no probs with a 5sec squirt around the ring road whatever your Power. The vents aid cooling so if you ever intend doing a Vmax to see what it will do change the bonnet.

 

Can definitely see it being a factor held flat out for a long period as you have seen all these problems. Mine being used on the road with high power levels as you say impossible to hold flat out for a long period

 

That would suggest that the air filter is holding back the power and that open hose allows enough air in to compensate? Obviously that is unfiltered and possibly hotter air from the engine bay?

I wonder what the small hose did? Something linked to emmisions / breather system I imagine?...or recirc but surely too small for that?

 

i dont have any experience of cossies but my YB powered kit car which has limited ambient air flow around the plenum sees IAT sensor temps of 60c+ when in traffic due to sensor heat soak but much less with bonnet off and ambient around the plenum.

this in itself may sound irrelevant but the heat soak effect means that it takes 2-3 seconds of charge air on the sensor (i.e NON-closed throttle) before the heat soaking is overcome and the sensor believes IAT has dropped. during that time period the ecu is retarding timing to prevent heat induced det. probably not so significant on track but definately a consideration if you want a quick getaway from the lights

 

Its been a while now, I must look in the engine bay to remember what it was connected to. I did leave the small hose on it but not connected at the other end at first. What ever it was, it being off has not had any negative effect as the car goes really well.

 

To be fair a kit car with a yb crammed in it and they are squeezed in there very very tightly will have very different under bonnet temps to a sierra. Myself it was no issue having no vents rod I can see having an argument as he runs into problems no one else ever will as his torque and horse power levels have not been matched. But as a road car I'll be fine

 

I agree with that

Cheers Paul

 

I think my little 205 engine bay is crammed tight in comparison to a Sierra. I used zircotec coating to try and help, I did the inlet too as they suggest it keeps heat out too but if I go over to the individual throttle bodies next year I don't think I will coat that.