Does The Spoiler Slow You Down ?

[Turbo_Steve]

Right, In principal I knew this was a possibility, but I would never have believed it would have made as much difference as it has on our car....

As some of you are aware, my rear window was recently destroyed by something inside the car deciding it preferred the M1 to a nice comfy Legnum (Regunamu).

Now, we've had a window fitter come out with the wrong window, which he only discovered after stripping down the tailgate. Rather than put it all back together, I've stored the parts safely, and so we've been driving around without a spoiler (and a bin-bag rear window).

So what has happened? I was first alerted at 60mph, that the car felt curiously "front heavy" and steered a little better: more direct. After a brief overtake (just near our house, where I know very well what my terminal is as it's on approach to a roundabout). My normal terminal speed on this straight would be level with the layby, and would be around about 80mph.
Then in and braking.

Without the spoiler, it's 110mph. Yes. I was surprised too.

It's not the weight of the glass...it was shattered and removed, and has been for a while. It's either the weight of the interior trim (it's not that heavy) or it's the spoiler.

And it's the spoiler: 50-100mph is suddenly very eager. Think in terms of losing a passenger and a half. Not sure what it's done to the handling: car feels a little more FWD at speed, but cornering still seems planted and stable, though obviously this isn't a track so I'm not prepared to really shred it.

:speechles

So....spoilerless carbon fibre tailgates all round?

[elnevio]

Wow! :o

I wonder if we can test this theory with a spoiler removal at JapShow?

[Wodjno]

I think your speedo is reading in kph Steve.. Think you need a new converter /yes

Or someone has installed and set-up a nice new ebc and ecu without you knowing ...

Even then !!

At a speed of 80mph normally, i would say thats apprrox 300 yds distance. Now your clocking 110mph at the same point ? That would suggest you would achieve around 120mph+ at 1\4 mile /Hmmm

These speeds haven't even been achieved with 330bhp and a 100 shot of NOS ?

[scott.mohekey]

So....spoilerless carbon fibre tailgates all round?

Just make it into a ute ;)

Seriously though, I'm not really surprised at this.. the new evos have vortex generators at the back edge of the roof in order to force the air flow to be closer to the rest of the car body. On the legnum you'd end up with a large eddy directly behind the tail gate. At least I THINK that's how it all works.

[Kieran]

Steve.... Interestng.

Couple of thoughts. I wonder how well the AYC will now work.

The other thought... I suspect it's the gap between the tailgate edge and the spoiler.... I've always thought that this was a deliberate gap to introduce a venturi and get some turbulence back there to suck the rear of the car onto the road. Probably explains also why the rear glass gets so mucky so quickly.

I wonder... When you have the spoiler re-fitted, I wonder what effect a layer of masking tape would have over that gap?...

[bradc]

Or how different the facelift and super vr4 spoilers are, as well as the dolphin style ones

[AlanDITD]

Im not sure when you guys are going on the strip next but for me its the 3rd of may. My 1st time ever but im happy to put this to the test.

30mph seems a crazy amount of extra speed from just removing a spoiler, not that im doubting you obv, but ill let the scinence prove either way

Also the other reson i would be surprised is a certain corsa round my parts with 488hp runs a 12.0 and the terminals are around 135 iirc. thats half the weight and double the power. Granted FWD but even so.

How easy are they to get off?

Alan

[Turbo_Steve]

I think your speedo is reading in kph Steve.. Think you need a new converter

Or possibly to re-read my posts before I press ok.....you're quote accurate wodj, that was supposed to say 100mph, not 110mph. D'oh.

And yes, even then, it still seems high to me. I've had a think overnight about why: the only other variable I can come up with is that the passenger was reading the speedo and not me, so this could allow for maybe 5mph? More like 2mph, though.

The point is that it really is a LOT faster.....just as you say, it's like having an EBC fitted...only more so. It's just like having a passenger and all their luggage for a 2 week holiday get out...and half a tank of fuel.

The road noise is quieter too.

I wonder if the transmission is being less "lossy" without the load on the rear wheels. Or if something cunning in the gearing is making it report the speed incorrectly.

The Zed had aerodynamic problems at a (reported) 175mph, where the speedo would flick up to the end stop and back down to 170mph and suddenly back to 175mph. In the end I had to get a friend to follow me in his 430, and he diagnosed the problem as the car leaving the ground! :eek:

[Davezj]

my old 1.3L mark II escort did the speedo flick at terminal velocity (on an old runway of course) but that was 105 flat out and it would flick to 115 for a few seconds then back down again and back up and back down, etc, etc.

but that was not the car leaving the ground it was a crappy speedo.

[Turbo_Steve]

LOL! I had a MkIV with the same problem at about 115mph (indicated) :D
The Zed's speedo topped out at 180mph, and from GPS runs it got more and more innacurate past 110mph, so my real speed was probably no more than 160mph...the Ferrari said it was showing 170mph matching my speed, but of course his speedo would be innacurate as well. No GPS unfortunately.

He stated that as the car hit small bumps in the surface, it would "ride too high", and that a little puff of smoke would come from the wheels as it "settled". The revs would mash against the limiter whenever this happened. As the car had active suspension, I originally assumed this was something electrical, but apparently it's a known issue with older cars at high speeds, where the body doesn't have aerodynamics designed for such high velocities.

Anyway, I digress.......going to try and get another properly 'timed' run tonight when it's quiet. I suppose what we really need is someone with onboard telemetry (racelogic or -meter or similar) to try a run on a despoilered Legnum - doing before and after for both straight lines and (as suggested) a circuit run.

[Turbo_Steve]

Oh, and spoiler is (I think) four bolts behind the plastic trim and two rubber grommets. Unfortunately, it's also covered in that gooey double sided sticky stuff, though I'm not sure why as it's REALLY dirty under there!!!

Maybe easier to grab a V6 tailgate off someone.

[Turbo_Steve]

Right..update. The lack of spoiler has definitely changed the handling of the car, and possibly the acceleration.....however it appears I have been duped by an underlying issue: after some discussion with Wodj, he pointed out quite accurately, that my car is as slow as an old dog with a broken leg. So it seems that whatever intermittant fault is at work is also affecting my acceleration.

I suspect I have a coil pack breaking down, or something similar. And it's getting worse: spend long periods running on 4 or 5 when the car is hot.
As it's heat related, this does rather point to a coil pack. Gutted.

[Wodjno]

Got plenty of coilpacks kicking around Steve /yes
It maybe just a lead though thats arcing out to the engine..

Soon have it sorted either way :D

[AlanDITD]

A coil pack will be easy enough to replace mate, get it done then do some proper testing :D

[peter thomson]

I'd sort that out soon Steve as a coilpack failure killed Keith's engine ecu last week

[Turbo_Steve]

Hmm...good point. How do you identify which coilpack it is on an intermittant fault, though? heat the whole lot up and measure resistances?

Wodj: Thanks - and yes, I agree the leads probably aren't helping...I was shocked at how thin they are!
I'm fairly certain the whole lot has never been touched....I barely touched the leads, and all the plastic clips simply fell away, which isn't a good sign.

And everything is very VERY tight...so I am not going to touch it until I have a complete set of plugs, leads and at least one coilpack waiting to go on.

Then, yes, I would like to borrow someone G-meter (or whatever they are called) as I will take a reading with Wodj's tailgate, and one with the spoiler back on.
It definitely feels different...whether it's quicker now looks more doubtful. Sorry everyone.
Mods...thank you for the title amendment!

[Fully]

Spoliers do slow you down in a straight line. They do give you faster cornering speed.

We put a new big racing spolier on our race car, dam talk about being slow on the back straight, I was being passed by everything. But dam a lot faster on the corners. So after a few laps, back into our pit area and off it came!