Since fitting of a V-mount the undertray on my FD has not gone back on yet - what do you guys commonly do....run with or without?
Are there any issues regarding running without one?
I\'ve heard they are important for air flow out from the engine bay!
Well - I was advised by a well know specialist that airflow was improved by running without one.....
Has anyone had any issues with grit or stones flying into belts etc.?
Who was that??
I was only saying what I\'d heard....not being a know all :P
depends on how you intercooler is setup, on FMIC I ran without one for a while I put back the undertray and got better cooling for the water rad.
On a V mount it may be different
My car runs a shedload cooler with the undertray on.
Also feels a lot mroe stable. That\'s an FRP one though.
I really would put it back on if at all possible, they make a big difference.
mine was taken off by reworx when they fitted the vmount, and not put back on as the rad projects lower, they said it wasn\'t necessary anymore - haven\'t had any probs over the last year, although i cr**p myself over speedbumps. With a standard engine, it does make a difference though.
ive been drifting for most of the season on a V mount setup with no undertray...
trust me.. run with one! temps are ALOT higher without one as the air hs a path with less resistance to run.. I\'d advise the undertray at a minimum if not.. additional ducting if your running a V-mount. :)
dont run with one and have no intention of running with one. Temps are all good whatever conditions.
As above it all depends on setup of rad and IC
hmmm...lots of different opinions. I may try and rig something up that caters for the lower radiator on the V-mount.
I\'m more concerned with stability at speed, and I can\'t imagine that gravel traps do it much good either.
Some intersting stuff for you :
http://www.autospeed.com/cms/A_2159/article.html
http://www.autospeed.com/cms/A_2160/article.html
http://www.autospeed.com/cms/A_2162/article.html
There\'s some stuff of relevance in there :) Worth a read, anyways :)
That\'s a really fascinating read, excellent links, SiH. Especially interesting the way that his intercooler "scoop" actually worked as a vent, sucking air up off the radiator and blowing it the wrong way through the IC! Then you read the third part, and it\'s obvious that the vent was in the worst possible place for it to act as an intake, the area of lowest air pressure across the bonnet. It shows with startling clarity that the shape and direction the vent faces is almost completely irrelevant compared to the pressure gradient involved.
Those experiments show that vented bonnets like the Mazdaspeed/KnightSports style ones where the vents are right forward between the headlights should work much better than the FEED style ones where the pressure measurements imply that if anything, their vents are more likely to be sucking air back into the engine bay rather than exhausting it out. That\'s exactly what the Yanks discovered forty-odd years ago with things like the cowl induction hoods on Camaros and Pontiacs where they utilised the high-pressure wave at the base of the windscreen to force air back under the rear of the bonnet to feed the carbs.
Exunctly :) It\'s the link that I dig out when people post up pictures of their bonnets raised at the back \'drift spec\' because it \'makes it run cooler\' :)
It could also go some way to explain why my AD9 bonnet didn\'t really seem to make much of a difference to cooling at all - I see FAR better temps with my MS undertray and stock bonnet. Goes to chow that you don\'t neccessarily need a vented bonnet with a V mount :)
It\'s a shame I never got round to actually doing a test like that with my old bonent, I just measured intake temps etc.
I have been thinking about this and i don\'t see the need for the undertray with a v-mount. As long as the v-mount is properly boxed in and ducted from the front bumper.
If anything would this undertray not keep extra hot air in the engine bay as the rad fans blow air in to the undertray and not directly out of the bay.
Quote from: redgti;640245I have been thinking about this and i don\'t see the need for the undertray with a v-mount. As long as the v-mount is properly boxed in and ducted from the front bumper.
If anything would this undertray not keep extra hot air in the engine bay as the rad fans blow air in to the undertray and not directly out of the bay.
Evidently not.....
I think it\'s down to the undertray keeping a nice, fast, smooth stream of air flowing under the car that a) sucks air out the rear lip of the tray due to moving faster than it and therefore creating a pressure drop at the rear and b) not being all messy and turbulent, thus making it easier for airstreams from the engine bay to merge with the airflow around the car.
Quote from: redgti;640245I have been thinking about this and i don\'t see the need for the undertray with a v-mount. As long as the v-mount is properly boxed in and ducted from the front bumper.
If anything would this undertray not keep extra hot air in the engine bay as the rad fans blow air in to the undertray and not directly out of the bay.
Have a read of the links I\'ve posted dude - Undertrays can make a huge difference, and the flow through the bay doesn\'t work the same way as a lot of people think :)
yeah i\'ll give it a read later i think. i wish i\'d done a study like this for my dissetation.
Well - here\'s what I\'m going to do. Go for a blast and check the Water / charge temps on the Power FC with the tray on, and then with it off - that should settle this one!
You need to get a lot more enpirical data than that if you want to fet some conclusive results dude. Repeated runs in tne same conditions, with the same exrernal temps etc at the very least.
I dont agree - same day conditions, run the car from 2,000 rpm to redline in 3rd and see what the temps do. if the airflow over the V-mount is compromised without the tray then the charge temps should reflect it noticeably - if they dont then I dont see that there is an issue.
I asked a friend of mine about the articles posted earlier in the thread - this was his response:
Aerodynamics is something of an art besides a science.
The pressure gradient across the rad front face to back face would give more indication of air flow through the rad. Also there will be a pressure variation at different places on the face of the rad. So the whole story would not be so simple.
The 25% variation in the under bonnet pressure would not translate to a 25% air flow change through the rad.
Temperature measurements in conjunction with the pressure measurements would give a better picture of what is happening.
Ok - temps wise there is s*d all difference with the tray and without it on a moving car.
The only bit left to decide on is whether the stability is effected at high speed, which is a little more difficult to test!:3Confused
i have a v mount without and under tray and have had many a high speed run 150 160 mph and no issiues with stability
the undertray acts as a kind of venturi which helps remove hot air from the engine bay. id doubt that a clipped/screwed on piece of plastic sheet could massively effect stability at speed a huge amount as the engine sub frame and sump take up a lot of space which would keep the air flow smooth enough. might be a different story if the sheet was made of strong aluminium and was incorprorated into making the entire bottom of the car as flat/smooth as possible. id guess that would make a lot of downforce. but im no aerodynamics professor.
I havent got round to making my undertray fit back on after my v-mount set-up, temps have been 20-40air and 82-85 water...so no drastic (if any affect so far)
But, I will be making the undertray fit again....as I don\'t really want to risk high speed instability...do you??
i\'ve not noticed any instability either over several track days
the way some vmounts are done (like mine) the rad fans would be totally obstruced by an undertray, my rad is only about ten degrees slant from the floor- i don\'t think i\'ll be putting it on again, no probs with temps either. The mot common style vmounts with the intercooler mounted 90 degrees to the floor and the rad at about 45 degrees would probably benefit though i suppose.
OK - have you had any issues with gravel traps on track days...:Thumbsup!
most of my track experience has been at nurburg, no gravel traps there lol
A stone took out my aircon rad and radiator when i had no undertray when my car was stock.
just trees and other stuff to hit then!:Thumbs-up
I have a V-mount set up with no undertray. Both temps are decent. As for high speed stability can\'t really comment as I have a RE style diffuser and it plants the car to the ground on motorways.
I guess for those people changing their front bumper the undertray will have to go anyway. My plan is to get a feed front bumper and get one custom made to match it.