Engine lid jacking

[thetyrant]

Ive had a quick search but didnt find anything on this, basically in my old Evo days it was common practice to jack the rear of the bonnet with spacers to create an air gap to help let out the heat in the engine bay, there are some downsides due to pressures at speed etc... and people telling you your bonnet isnt shut all the time lol... but generally it worked well for me especially for track/sprint use, i was pondering doing the same on my Roadster now its turbo charged to help with the engine bay cooling, im thinking that spacing out/modifing the rear catch and making longer rubber stops so when latched there is a small air gap at the back of engine lid might work well.

Anybody done this on a roadster ?

[Petrus]

That would probably work quite well. Would most likely even improve the aero at the back a bit. Add a rubber lip to the edge of the lid and you increase the extraction even more and create sóme downforce.

Would look quite vintage NSU Prinz TTS too 

[105e]

Works well at the front as there is lots of cold air going in , pushing the hot air out,  not sure it would be so succesfull with a rear engine..

[Petrus]

not sure it would be so succesfull with a rear engine..

Tótally tried and tested

[105e]

They havent got any heat to get rid of,,   aero attempt..

[Petrus]

They havent got any heat to get rid of,,   aero attempt..

The NSU is air cooled and the Abarths seriously tuned with the liquid cooling being suboptimal.

If you want an example of combined heat extraction and aero, that existst too in the later Simca Rallye models that had a spoiler at the edge of the rear deck extracting air from both the louvres on top of the deck and the additional holes in the rear edge.

Bottom line; it works with rear engines. Véry well actually because the heat is góne whereas with front engines it first needs to pass the entire length of the car.
Additionaly, at the rear it does not add much if anything to the drag.

So to the OP; it will imo work very well. It´s just not very elegant. I pérsonally like it though....

[H1GRM]

Ive had a quick search but didnt find anything on this, basically in my old Evo days it was common practice to jack the rear of the bonnet with spacers to create an air gap to help let out the heat in the engine bay, there are some downsides due to pressures at speed etc... and people telling you your bonnet isnt shut all the time lol... but generally it worked well for me especially for track/sprint use, i was pondering doing the same on my Roadster now its turbo charged to help with the engine bay cooling, im thinking that spacing out/modifing the rear catch and making longer rubber stops so when latched there is a small air gap at the back of engine lid might work well.

Anybody done this on a roadster ?

I assume you have a fan mounted under the engine lid to suck cold air in so wonder how that would be affected? Would the intake of cold air flow straight out?

Greg

[thetyrant]

Works well at the front as there is lots of cold air going in , pushing the hot air out,  not sure it would be so succesfull with a rear engine..

The air pressure will suck the heat out at rear and as heat rises as well it will naturally escape if the lid was open.

[thetyrant]

I assume you have a fan mounted under the engine lid to suck cold air in so wonder how that would be affected? Would the intake of cold air flow straight out?

Greg

I haven yet fitted a fan no as its not a TTE kit I have, they suck air out the engine bay not blow it in as far as im aware, fitting a fan is also on cards as a possible but there are other issues with that and jacking lid might give a noticeable improvement without the need to fit fan.

[H1GRM]

I naturally assumed they suck the hot air out but am reliably informed that it is in fact cold air in.

@s12vea can you confirm?

[JB21]

Interesting thread and something that the MR2 needs especially with the 2ZZ dropped in. Mine gets so hot on track the gear linkages start to expand making shifts sticky due to the slack in the cables.

Whilst the engine is out of mine I'm wrapping the shifter cables in heat reflective pouches, applying copper grease to end link ends as well as wrapping the header in DEI titanium exhaust wrap. I'm also looking for ducting from the NS vent to the gearbox.

Opening the rear lid slightly at the hinge end would definitely help reduce engine temps further given the air flowing over the roof line and down the engine lid, fitting vortex generators would aid this further as air flow would be brought closee into the contour of the rear screen and boot lid.

[s12vea]

I naturally assumed they suck the hot air out but am reliably informed that it is in fact cold air in.

@s12vea can you confirm?

Correct they suck cold air in

[thetyrant]

Interesting thread and something that the MR2 needs especially with the 2ZZ dropped in. Mine gets so hot on track the gear linkages start to expand making shifts sticky due to the slack in the cables.

Whilst the engine is out of mine I'm wrapping the shifter cables in heat reflective pouches, applying copper grease to end link ends as well as wrapping the header in DEI titanium exhaust wrap. I'm also looking for ducting from the NS vent to the gearbox.

Opening the rear lid slightly at the hinge end would definitely help reduce engine temps further given the air flowing over the roof line and down the engine lid, fitting vortex generators would aid this further as air flow would be brought closee into the contour of the rear screen and boot lid.

Indeed im surprised there isn't more threads on this especially on SC over in US etc, to me heat build up in engine bay is the biggest issue these cars suffers especially on track, im not sure about hinge side as while it will help cooler air go into engine bay but its no help letting the hot air/pressure escape, both might be an option and if I do this I will try both ends separate so either front or rear lifted, also both together so hood has air gap all the way around as another option.

Fitting a fan and removing the under lid vent cover will help as well, but then rain can drip direct onto engine  where as with a small hood lift at least you retain some weather protection, I think just lifting rear to help pressure and heat escape will be most effective but we will see.

[thetyrant]

I naturally assumed they suck the hot air out but am reliably informed that it is in fact cold air in.

@s12vea can you confirm?

Correct they suck cold air in

Really that is surprising as there are fighting the rising heat, I guess its more for when in traffic etc to get some air into engine bay and not so effective at higher speeds where you have air flow under car helping with that.

[Petrus]

Really that is surprising as there are fighting the rising heat, I guess its more for when in traffic etc to get some air into engine bay and not so effective at higher speeds where you have air flow under car helping with that.

Still true; the fan blows air dówn.

I would try the engine lid lift. It is time prooven and cannot malfunction.

The fact that nobody has done it before on the MR is not proving anything. Obvious things are only so when someone does it. There are no modern rear engined cars nor many affordable mid engined ones so the once common practice simply is no longer part of collective memory.
Over hére btw there is a tuned Seat 600 about in the village. The owner uses it quite regularly and that has the rear lid open too.

[thetyrant]

Indeed lifting the rear of lid should be simple to do and have some useful effect, ideally i would probably have a 3 stage setup with it easy to swap between them so it can be either closed, small air gap for road use, or larger air gap for track use, will get to it at some point as lot of other things to sort first.

[Petrus]

will get to it at some point as lot of other things to sort first.

Since it is a simple thing to do, maybe give it a bit of priority as keeping the power house cooler may very well give you a few less complications.

[Petrus]

[Gaz2405]

Although I like the look of the vented hoods/bonnets. I don' really think additional cooling is needed.

On track my oil peaked at around 90, likewise with coolant temp never above midway, intake temps always below 40 too.

I'll add that I am charge cooled and oil cooler and have the inner rain shield removed.

I think it would be worse in traffic, but I'm also surprised the fan doesn't suck hot air out I think that's how I'd wire it if I had one.

I'll probably go for additional louvres, just for the look really.

[thetyrant]

Although I like the look of the vented hoods/bonnets. I don' really think additional cooling is needed.

On track my oil peaked at around 90, likewise with coolant temp never above midway, intake temps always below 40 too.

I'll add that I am charge cooled and oil cooler and have the inner rain shield removed.

I think it would be worse in traffic, but I'm also surprised the fan doesn't suck hot air out I think that's how I'd wire it if I had one.

I'll probably go for additional louvres, just for the look really.

Interesting thanks for info, sounds like your oil is too cold though so im guessing you dont have thermostatic sandwich plate ?  you really want oil to get upto 100c even under normal running so it burns out the moisture that accumulates while warming up from condensation, i would say on track 100-110peak is about right with good oil.

[H1GRM]

So has anyone reversed the fan to extract hot air on a 1ZZ TTE turbo?

[Gaz2405]

Although I like the look of the vented hoods/bonnets. I don' really think additional cooling is needed.

On track my oil peaked at around 90, likewise with coolant temp never above midway, intake temps always below 40 too.

I'll add that I am charge cooled and oil cooler and have the inner rain shield removed.

I think it would be worse in traffic, but I'm also surprised the fan doesn't suck hot air out I think that's how I'd wire it if I had one.

I'll probably go for additional louvres, just for the look really.

Interesting thanks for info, sounds like your oil is too cold though so im guessing you dont have thermostatic sandwich plate ?  you really want oil to get upto 100c even under normal running so it burns out the moisture that accumulates while warming up from condensation, i would say on track 100-110peak is about right with good oil.

Infact your right is was around 100-110 peak.

Just been to check the markings on the gauges 😂

[thetyrant]

Sounds better    what do you see under normal road driving out of interest ?  i plan to add an oil cooler next year before hitting the track and not sure if i need to use a oil stat or just run it open.

[Gaz2405]

It doesn't get much use in the road, but I'm probably taking it out tomorrow for an hour or so. So I'll have a check.

From memory it only went up around 10 degrees on track.

I think if I wasn't rushing the build a thermostatic plate would have been better.

I usually let it idle for a good 10-20 minutes before going out in, which I'm sure the neighbours love!

[jonbill]

Although I like the look of the vented hoods/bonnets. I don' really think additional cooling is needed.

On track my oil peaked at around 90, likewise with coolant temp never above midway, intake temps always below 40 too.

I'll add that I am charge cooled and oil cooler and have the inner rain shield removed.

I think it would be worse in traffic, but I'm also surprised the fan doesn't suck hot air out I think that's how I'd wire it if I had one.

I'll probably go for additional louvres, just for the look really.

Interesting thanks for info, sounds like your oil is too cold though so im guessing you dont have thermostatic sandwich plate ?  you really want oil to get upto 100c even under normal running so it burns out the moisture that accumulates while warming up from condensation, i would say on track 100-110peak is about right with good oil.

You don't have to run the engine long at 90c to drive any water off. A couple of mins tops I'd think.