Mivec Owners Group

Lesson learned
@Benett; if you can close that trailing edge down, then do it as it raises engine bay temperatures while the car is moving as mentioned.
If you want a long technical explanation of why that occurs, I'll post it.

Mitsubitchy how certain are you of this?
There was a time that I had my hood raised like that as well, and even though I never took engine bay temperature measurements I did notice that hot air was entering the vents for the HVAC.
The vents are between the hood and the windscreen, and the hot air was from the engine bay. So naturally I expected that the raised hood was helping circulate air in the engine bay and hence lowering temps.

As you can see (think very carefully about it, little bit counter-intuitive at times) in the diagram, raising the trailing edge of the bonnet is actually going to further increase pressurisation of the engine bay when the car's moving with more and more speed as the rushing air will be drawn in around the enlarged gaps (don't forget the sides) with greater pressure, increasing the downward pressure at that point. By increasing pressure in the engine bay like that, you'll end up reducing the natural beneficial airflow path through the radiators, intercoolers etc.

Even anyone thinking of adding scoops/vents etc.- aerodynamics can very often be counter-intuitive and these parts need to be carefully planned and not just slapped on anywhere. Even exhaust manifold wrapping upsets the natural flow through the pipes thereby not even being beneficial, but a hindrance in many cases.

My interpretation of the above diagram is that the yellow areas are high pressure, the white ones being low pressure.....so the base of the windscreen will suck air out.

Ignoring the diagram, the engine compartment is open at the bottom anyway, whatever goes in at the front comes out of the bottom. Lifting the rear of the bonnet will make a very tiny difference, probably insignificant.
Personally I think it's pointless raising the back of the bonnet, like many other mods are pointless. Here in NZ I doubt it would be road legal as there's often hooks so that when you crash the bonnet forms part of the crumple zone

But putting a 3.8 into a mirage....brilliant.

Steve

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6G72 mivec Twin TDO5 20Gs up and running.
6G72 mivec bored and stroked to 3.4 litres...Frankenmitsi build
6G74 mivec bored and stroked to 3.9 litres....Frankenmitsi build.
6G75 under construction....4.2 litres bored and stroked.Another Frankenmitsi.

True, lower pressure than the yellow areas, but still a substantially large amount of downward pressure considering how much air pressure there is acting on the body profile, from air rushing over it at 100km/hr. Open up that bonnet trailing edge gap and a lot more air will pour down the opened exposed sides of the bonnet excessively pressurising the engine bay, disrupting the normal flow of air.

Out the bottom is right in every context By excessively pressurising the engine bay from above, the incoming air from the front that sweeps past the radiator air can't freely flow from the front of the bay to the rear through the engine bay as easily as it will be hindered by excessive pressure from above filling the bay causing a higher pressure differential within the bay blocking the path. Hence the warm radiator air resides in the bay for longer, thereby cooling is inhibited, even more so as the car gets faster.

@Bennett, any more pic/videos of that beast?

hi guys, sorry for the late updates!!!

the car has been dyno'ed and has currently 310whp with 285ftq... is being used as a daily driver and feels and pulls awesome on the street...





New bits like Seibon Carbon fiber hood and JDM Trunk... also notice the custom made 15x3 rear rota slipstreams in the back for race purpose only...





here are some latest videos...

dyno video when had 309whp
http://www.youtube.com/watch?v=LcN7G2b5Hhg

track video 1/8 mile no time because it's a friday event to help people quit street racing... also missed 3rd gear LOL... on this video has Mickey Thompson ET Street tires 000 treadwear on a 225/50 size running at 8psi...

http://www.youtube.com/watch?v=DWxyOgETcq0

anothe pass on the track... this time clutch slipping problem in 3rd gear... :/

http://www.youtube.com/watch?v=S2i1Z0nS218

How's this one going?
No problems with the big bore size and sealing problems with the heads?

Steve

_________________
6G72 mivec Twin TDO5 20Gs up and running.
6G72 mivec bored and stroked to 3.4 litres...Frankenmitsi build
6G74 mivec bored and stroked to 3.9 litres....Frankenmitsi build.
6G75 under construction....4.2 litres bored and stroked.Another Frankenmitsi.

no one knows what has happened with that one since last summer...

here's a buddy of mine with a custom intake manifold with 3 80mm throttle bodies... has 362whp & 327ftq...

Best time is 10.51 @ 132mph

Very impressive work there.

How do the 225 tires fit at the front?

since i have 15x7 rota slipstreams with +40 offset the fit just perfect! if i had +20 or +25 offset wheels it would look like a atv lol

Do you get any rubbing at all?
I was thinking of using 225/45/15 tires as the rolling diameter is the same as 205/50/15 but was concerned with tire scrub

95mm is the max you can go without sealing issues with the DOHC heads, but the DOHC heads on the 6G75 will bump compression somewhere near 11.5:1 or more.

Necro reply but no doubt this thing blew up.

Changing from a 6G75 head of 57 or so cc combustion chamber to a 6G72 head of 46 cc bumps the CR to about 14 to 1.

_________________
6G72 mivec Twin TDO5 20Gs up and running.
6G72 mivec bored and stroked to 3.4 litres...Frankenmitsi build
6G74 mivec bored and stroked to 3.9 litres....Frankenmitsi build.
6G75 under construction....4.2 litres bored and stroked.Another Frankenmitsi.