15 replies to this topic

[haggi961]

Has anyone added more then the 2 ducts on the N/A and the 3 on the turbo. My thinking is more ducts is more cool air entering the engine keeping the heat down. Would there be any specific places to put them?

[iceman]

Mine fell out as they were put in upside down by a certain tuning firm that shall remain nameless and, whilst i have them in a bag somewhere, i've never bothered to refit them. I was told by a vx member that i respect to not bother, so didn't. I'm only running 161 bhp though, so extra cooling would probably not be beneficial for me. I guess it all depends what power you are putting out as to what number of vents you'll need. Best regards... ..icey

[Nev]

Try running without a rear undertray and see if you notice any handling difference. If you don't then leaving it off will maximise cooling a bit more than adding a NACA duct. Your engine/intake temps will improve and your gearbox will be thankful. Assuming you are making 370 BHP, and your gearbox losses are around 11%, that means you gearbox has to dump approximately 30 KW (ie 30 1-bar electric heaters). Adding an extra NACA duct isn't likely to impact that amount of heat capacity.

Edited by Nev, 28 April 2013 - 10:58 PM.

[haggi961]

Thats a idea but is there not a reason why its needs to be there. I would of thought it would keep the car stable when driving at higher speeds.

[Nev]

Thats a idea but is there not a reason why its needs to be there. I would of thought it would keep the car stable when driving at higher speeds.

Ideally/theortically, I'm sure it's a great thing to have a flat belly as it's just common sense that it helps smooth airflow. However, in pratice it may not be warrented until a you reach a certain speed (whatever that may be) when you have to offset it against the negative things (such as stopping heat evacuation).

VX220s have loads of parts on them that have "no reason". For example the boot spoiler on a VXT is just cosmetic. Removing this spoiler would IMO make your car very slightly faster for example.

I think the only way you can answer the question is to drive with the floor pans on and off and see if you think there is a difference at the speeds you normally drive. I did this and came to the "educated guess" that with my potential heat build up in the engine bay, I'd be better off without it. One of the hidden benefits of this might be that (so far) I havent suffered from any sort of gearbox problems (like the dreaded melted fork selector ends), even though I am putting 400 ft/lb through it.

Edited by Nev, 29 April 2013 - 08:54 AM.

[TheRealVXed]

It will make little difference as the pressure of the air running under the car should (if all the other bits are working) be lower than the air on top. Most of the engine cooling comes from the side vents and top. Peace

[mbes2]

The middle duct on the under tray feeds flowing air up to help cool/flow the turbo. Then all hot air vents from the top.

[CocoPops]

Do you not risk tearing the rear clam without a rear under tray? ie the lower section acting as a scoop?

[Nev]

Do you not risk tearing the rear clam without a rear under tray?

ie the lower section acting as a scoop?

I wondered about this too, but I did incrementally faster runs and haven't had any problems. I did roughly measure the heights of the leading edge of the rear of the clam and it is several CMs higher than the front floorpan, so I think it is mostly out of the main air stream. At extreme speeds though it may be a serious risk...

Edited by Nev, 29 April 2013 - 10:10 AM.

[TazN]

Ran my na for most of last summer without rear undertray. Ran it upto about 90 with no ill effects, will be putting it back on when it's back up and running though as I don't have space to store more parts and don't want to throw it out...

[siztenboots]

if you mod it, then add more cooling to the gearbox

[Dave E]

if you mod it, then add more cooling to the gearbox

I doing just this, I've got a new naca duct which will be position to cool the 'box, it's the pikey and lighter version of what I was planning, pump/rad etc,

Edit, 2000th post in 7 1/2 years, there's just no stopping me

Edited by Dave E, 29 April 2013 - 01:10 PM.

[Winstar]

Try running without a rear undertray and see if you notice any handling difference. If you don't then leaving it off will maximise cooling a bit more than adding a NACA duct. Your engine/intake temps will improve and your gearbox will be thankful. Assuming you are making 370 BHP, and your gearbox losses are around 11%, that means you gearbox has to dump approximately 30 KW (ie 30 1-bar electric heaters). Adding an extra NACA duct isn't likely to impact that amount of heat capacity.

that a rather over conservative calculation even flat out on track you'll never be able to put any where near the full power of the engine thorugh the drive train for any length of time and 11% is more like the full drive train loss than jsut the gearbox

I think the only way you can answer the question is to drive with the floor pans on and off and see if you think there is a difference at the speeds you normally drive. I did this and came to the "educated guess" that with my potential heat build up in the engine bay, I'd be better off without it. One of the hidden benefits of this might be that (so far) I havent suffered from any sort of gearbox problems (like the dreaded melted fork selector ends), even though I am putting 400 ft/lb through it.

The answer, as proved by the Hoffman Europa, is to fit a dedicated gear box oil cooler running flow on the out side of the gear box won't make that much difference, torque has nothing to do with the heat is viscous shear from the gears.

It will make little difference as the pressure of the air running under the car should (if all the other bits are working) be lower than the air on top. Most of the engine cooling comes from the side vents and top.

Peace

I suggest you go and look up how a NACA duct works.

The cooling flow on the NA, with all the important hot bits at the back of the engine, works by flowing up through the NACA ducts over the engine and out of the top vents. Which is why when people space their diffuser they short circuit this and actually incrrease the temps in the exhaust and gearbox area.

[TheRealVXed]

Fair enough. I wasn't really thinking right this afternoon and omitted in my brain the effect of air over the car and the action of the naca ducts. And my post should have red out of the top...

[drunknmunky]

Mine didn't have an undertray when I bought it, only the rear diffuser section, ran like this for 3 months through the depths of this winter just gone, and finally got one and put it on in march. It runs 3 or 4 degrees cooler with the tray on, (standard n/a ducts) and is noticeably less twitchy on the back end over 85 or so!

[drunknmunky]

Also, I think it accelerates slightly better upwards from 85 ish