smooth underside

24SEVEN

24SEVEN

Anyone tried smoothing off the underside of their car? i.e making a proper splitter/undertray under the car for smoother airflow, and to some extent protecting your car's underside from speedbumps if you're running low.
 
just curious... I'm hardly going to go and make one for my 1.4...

There is a point if you want to use your car as a trackday/autotest/race car as well.
 
ive thought about making a proper engine bay undertray, to try and stop some of the mud/water etc coming up through. as i live in middle of nowhere, most of the roads are caked in mud this time of year.
 
see, a practical reason for it. it would probably be the best way to protect your car from grit salt in the winter too. sheet of water treated plywood cut to fit.
 
i guess wood WOULD work lol, but i was thinking of metal of some kind, with some slats vented backwards to allow anything inside to run out.
 
that's gonna add a fair bit of weight tho. water proofed wood. it's softer too so if anything hits it it's not gonna risk denting and crushing something in the engine bay.
 
yeah i was thinking that too about the wood. i was thinking metalwise, some thin aluminium maybe. i'll never get round to it though lol
 
the idea behind this is prob to help air travel under the car as best as poss can be. Lots of race cars have this and with "active" (read: not ones that look all nice and fancy - but splitters that actualy do a proper job of causing down force) splitters. Benifits:

1. Less drag on the car as air passes under it
2. It can help "suck" the car onto the ground if designed properly.

But we are talking race cars here - it will have little, if any effect on our cars unless you are willing to spend the time and effort to research into it to design it properly...


Also worthy of a note, the bottom of the engine gets rather hot and im guessing there will be some sort of draft under there. Blocking this off could increase engine bay temps... IE on the primera, there is a vent in one of the splash trays for gear box cooling...
 
Yeah thinking about how flimsy the plastic splash guards are, they could easily have extended it further back, and they obviously didnt for a reason (heat like you say). My thoughts on it were purely to stop crap getting in, but it'll be fine as it is.
 
Spose there are downsides to it too, but as you said SplanK, there are right ways and wrong ways to do it. Wondering if anyone had tried to get it right.

Could always do it in a way that actively vents air into the engine bay, but mesh it over to stop too much crap getting in there, or do it in a way that causes a sort of vacuum in the bay, drawing air out from underneath and in through a bonnet vent or something. there's one way of looking at it.
 
if you have a scoop under the car, its just going to pull a ton of water into the engine bay - not what you want really...

if you are that worried about your car, either..

1. dont lower it
2. Buy a sump guard as thats the must vunerable part of the engine when it comes to hitting things
 
sump guard... simple answer to a stupid question :D.

though it could be advantageous to setup a running airflow through the engine bay if you're running a sizeable intercooler or fairly hefty turbos. or would the extra air under the car cause a problem?


Smooth off the rest of the underside as well :D:D:D
 
extra air isnt hte problem, its all the crap that it would suck up... you also have the issue of where the hell is it going to go.

I thionk air enters through the front and escapes through the bottom (unless you have backwards facing vents on your bonnet...
 
I meant have something under the engine bay that would suck air out from underneath. Doesn't the GTi-R have a top mounted intercooler, hence the bonnet vent? Where does the air go?

Force more air into the bay by createng a vacuum driven by a vent under the bay. Like having a bonnet vent that draws air out of the engine bay underneath the car, drawing air in through the top.

if you get what I mean.

P.S. for anyone thinking I'm going to chav up my mera with this, don't be stupid. I'm just having a bit of fun
 
TBH its not worth it on our cars... yes the GTiR has a bonnet vent for the inter cooler - however thats for hte intercooler. This is not required if there was no intercooler!
 
if anybody puts the intercooler on top of the engine on a almera they deserve shooting - everybody knows that its one of the worst place to put an intercooler as the engine heats it up at low speeds
 
SplanK said:
if anybody puts the intercooler on top of the engine on a almera they deserve shooting - everybody knows that its one of the worst place to put an intercooler as the engine heats it up at low speeds
Click to expand...

That maybe but it is there to reduce turbo lag, just like an impreza turbo as they have one in the same place. They would be less effective running around in traffic but you don't really need it then anyway. Once running at a decent speed it's going to be kept cool due to the airflow.
 
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