Bonnet weather strip

[Daninplymouth 61]

Hi, just a question on my previous car it was quite common to remove the rear weather seal strip at the back of the engine and the under bonnet insulation. This helped with under bonnet temperatures. I just wondered if anyone had tried this on this car and if it was worthwhile?

[GravelRash 62]

I've removed the rubber strip fairly recently as a quick (and free) solution to lower the under bonnet temperatures.

I've not measured it, so this is entirely broscience, but I think it's having a marginal positive impact. My understanding (from Google, not any scientific knowledge) is that the air-pressure at the base of the windscreen is low and therefore the air gets 'trapped' in this zone by the air rushing over the top of the bonnet and over the windscreen.

What I can say is that since removing that weather strip the bonnet no longer raises itself up at high speeds. It stays flat.

Back to broscience; the miniscule gap must be making a difference as the air buildup in the engine bay clearly isn't as much because the bonnet isn't being forced up.

I'm looking at other solutions and once I've decided on the way forward, the rubber strip will be re-attached.

I've not removed the under-bonnet insulation.

[nerdstrike 186]

Are there any other exits from under the bonnet? Is the radiator air supposed to exit through the undertray?

[Church 209]

+1. IIRC from pic from Velox/Verus CFD modeled air flows related to designing hood vents extra openings there won't do much to help evacuate hot air from engine compartment.

Linkie #1, Linkie #2.

So rather you'll loose more, as in more rain/snow will get there, then you will gain something cooling/venting wise. BTW, windscreen vipers put in that recess also are there for a reason, to reduce their impact on drag.

I suggest to make normal vents rather (eg. in same places as verus vent kit, or CSG trackspec one) in right bonnet places, where low pressure zones are. They do work/help with reducing underbonnet temps some and also for reducing front lift.

[GravelRash 62]

2 hours ago, nerdstrike said:

Is the radiator air supposed to exit through the undertray?

Yes, the undertray is vented to allow heat to be excavated via the air travelling under the car.

I believe Beatrush sell a panel that improves on this principle, although at a casual glance I didn't spot much difference between it and the OEM one.

My preference is vents on the bonnet. I have the Verus ones, but I flip-flop between liking the visual change and hating it. Opinions also vary across the people I mention it to.

[Church 209]

Purely looks wise i like CSG trackspec ones better too, then verus, but verus provide also optional rainguards & are of size to not cut over hood's strengthening ribs.

[Daninplymouth 61]

10 hours ago, Church said:

+1. IIRC from pic from Velox/Verus CFD modeled air flows related to designing hood vents extra openings there won't do much to help evacuate hot air from engine compartment.

Linkie #1, Linkie #2.

So rather you'll loose more, as in more rain/snow will get there, then you will gain something cooling/venting wise. BTW, windscreen vipers put in that recess also are there for a reason, to reduce their impact on drag.

I suggest to make normal vents rather (eg. in same places as verus vent kit, or CSG trackspec one) in right bonnet places, where low pressure zones are. They do work/help with reducing underbonnet temps some and also for reducing front lift.

I get the vents are a much better solution but just had a thought and wanted to see if there was any issues with removing the seal. For instance I have a track day in a few weeks and for the 30seconds it takes to pull off if it helps a little then it’d be worth it. On my old car you could see and feel the heat coming out

[GravelRash 62]

On my last track day, which I ran without the weatherstrip, I just lifted the bonnet when I come off the track.

On the track, the car is moving quite quickly (it should be  ) so the airflow through the front will probably suffice, unless you're running something seriously beefy under the bonnet.

I'm looking at cooling for the car in traffic and more daily driving experiences where lifting the bonnet isn't really an option. I'm not sure the wife would tolerate me parking miles away from other cars and then standing around for 5 minutes with the bonnet up, engine running to cool the oil off.

[Mike 458]

Removing the rubber strip at the back should be fine, I've been told it's a good way to help temps on track as it frees air trapped in the bonnet so gets more airflow. 

I don't think you need to worry about temps on a daily drive tbh... 

[nerdstrike 186]

In daily driving you usually want the car to get hot and also to warm up quickly from cold. The highest efficiencies are available at high temperatures (not the intake charge, just the engine) and the most wear occurs from being cold for longer.

I guess that the strip is there to help the engine warm up, and perhaps to stop the bonnet rubbing. The highest pressure in the CFD model linked above is around the bonnet/windscreen join, so removing the rubber strip could have the wrong effect at higher speeds even while it helps at idle.

[Deacon 1357]

Me and Will looked at this at Bedford comparing mine with the bonnet vents and his without (the rest of our spec is pretty similar). The bonnet vents (with rain covers removed) meant I was running about 10° cooler than Will for oil temperatures. 

[GravelRash 62]

1 hour ago, Deacon said:

Me and Will looked at this at Bedford comparing mine with the bonnet vents and his without (the rest of our spec is pretty similar). The bonnet vents (with rain covers removed) meant I was running about 10° cooler than Will for oil temperatures. 

Good info, also just to add, I've seen it mentioned that it's the under bonnet heat that lowers the lifespan of the #1 coilpack, which is the common cause of the misfire people seem to experience.

That's why I'm looking at the vents, I'd not bother if I was just daily driving, and also why once I get something else sorted I'm re-adding the rubber strip.

[Church 209]

Maybe lowers lifespan, but imho it's more about misdesign of early coilpacks, as supposedly updated coilpacks in later years don't show failures with them.