coyoteboy
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| posted on 14/9/10 at 09:38 AM |
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Design strategy
So, while I've been here a week or two now and I've posted in about 10 sections for advice on different engines etc, attempting to find
some generic ideas and info (rather than starting from "I want a V8" or suchlike, I've decided to compile a list of part weights
(approx) from which I can start a design strategy. I appreciate I've been given loads of useful info and it's helped me thinking through a
lot.
I'm looking for a combined set of goals. Most bang for buck (in locost theme!) but also I want to ensure I don't take the cheap, powerful
but not particularly good handling route. So I've compiled a list of part weights and car layouts to see how they stack up in both total weight,
power to weight ratio, and potential max sensible power to weight ratio for if I become rather flushed with cash.
Going from experience, the following link lists the approximate parts weights and required numbers etc - I'd appreciate it if people could look
over and comment on the weights/powers to see if I'm in a reasonable range. Happy to discuss here, and I think the latter sheets are editable by
anyone so if you fancy copy/pasting and making mods that's cool.
Would help if I included the link!
https://spreadsheets.google.com/ccc?key=0AmyE35lIUssjdEh0RUM0aHZSYUQtQzY1dW1HeGx5cEE&authkey=CKfa-McH&hl=en_GB#gid=0
Cheers all!
[Edited on 14/9/10 by coyoteboy]
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Irony
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| posted on 14/9/10 at 10:26 AM |
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I can't comment on the other engines as I only have any knowledge on V8's. I think your gear box and engine weights are a bit high or low
depending on what V8. If your planning a Rover V8 I would go with 185kg for the engine and 65kg for the box. Also when getting up 260Bhp on older
engines your costs will go up. I would suggest that these figures are high. I am looking at perhaps 200Bhp on my 3.9l RV8. You will need a more
modern Rover V8 to get up 400BHP and I think you will spend thousands.
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coyoteboy
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| posted on 14/9/10 at 11:14 AM |
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Cheers for the comments Irony - the V8 in question is an audi 4.2, so sits at 260 in stock form IIRC. It is indeed expensive to start from
though...tis a nice lump though:
I'm struggling to find references for weight of these, but I'm guestimating they're heavy. I'll add another column for rover
V8 with your info, much appreciated!
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Irony
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| posted on 14/9/10 at 11:38 AM |
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I personally feel that the Audi V8 would be the most 'awesome'. I believe that performance is not everything and there is a lot to be
said for the theatrics of a awesome V8. I doubt it's a locost option though.
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coyoteboy
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| posted on 14/9/10 at 11:42 AM |
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Yep, the giddy schoolkid in me wants as many cyls and as much noise as possible. The engineer in me wants the lightest most powerful option! I like
the audi layout more than anything, it's proper F1 styling and packaging and probably the best for handling (if it wasn't for the
weight).
And at the end of the day, I want to do it on a sensible budget and still have holiday cash left over!
[Edited on 14/9/10 by coyoteboy]
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RK
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| posted on 14/9/10 at 11:49 AM |
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Get your measuring tape out, and plan for some chassis mods to handle the extra power and weight! I'd MAKE it work, if I had that engine!
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coyoteboy
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| posted on 14/9/10 at 11:52 AM |
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I'm designing from scratch, I have no chassis limitations  It may or may not be a locost design chassis, we'll see what turns out the
best option!
RK - knock yourself out
http://cgi.ebay.co.uk/audi-a8-4-2-v8-ABZ-engine-/310244826261?pt=UK_CarsParts_Vehicles_CarParts_SM&hash=item483c085c95
[Edited on 14/9/10 by coyoteboy]
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scootz
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| posted on 14/9/10 at 12:35 PM |
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I take it you're going mid-engine?
It's Evolution Baby!
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eddie99
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| posted on 14/9/10 at 12:38 PM |
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Mind if i ask what happened to duratec?
http://www.elitemotorsporteng.co.uk/
Twitter: @Elitemotoreng
Facebook: http://www.facebook.com/pages/Elite-Motorsport-Engineering/153409081394323
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NOTE:This user is registered as a LocostBuilders trader and may offer commercial services to other users
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coyoteboy
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| posted on 14/9/10 at 12:51 PM |
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Probably mid engined. My thinking started off as "I'll make a locost". Then I thought I fancy more power. And something a bit
different. Maybe a bike engine, maybe a longitudinal V6/V8. Duratec V6 was one of many options but doesn't really stump up power, weight or
layout-wise. Here are my problems:
I really want mid-rear engined if I can do it, I'm not keen on teh engine being up front unless I have no other choice.
V6 weighs pretty much as much as a V8. Most V6's come with transverse boxes only which means no nice inline V, packaging "issues"
and relatively (very) low power for the weight without big mods, unless I'm mistaken?
V8's only really usable in mid-engine'd form if I get it with longitudinal FWD box (i.e. audi only from what I can see). Also weigh a ton
and maybe compromise handling. Possibly so much power I can't get it down to the ground. I'd love to use the 1uzfe but I can't find
a FWD long box that mates without £500 adapter arrangements.
Bike engines - sound like fun, certainly a contender but mixed feelings - insufficient power in stock form so would want it turbo or supercharged,
which adds lots of expense. No experience with bike engines. Would want to go megasquirt so need to buy injectors, make manifolds etc and find a
matching diff, so prices are rising.
3S-GTE - heavy-ish (about mid-way) but bombproof and very high specific power. Cheap (ok, not cheap cheap, but you can get whole donors for £500).
Some lack of grunt below spool speed (2500rpm) but that makes normal cruising easier. Stock gearbox puts engine forward of rear axle (if a little
high) and some come with LSD. This would essentially be an Atom.
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scootz
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| posted on 14/9/10 at 01:09 PM |
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If using the Audi, then the 01X transaxle is perfect for the kind of power you're talking about.
You will not find a cheap solution for sticking one of these engines up front... a modded Audi 4x4 box is a complete non-starter due to its bulk and
weight. Unless you're planning a mahoosive transmission tunnel, then forget it.
You can get a bellhousing from Tiger in Holland that will mate an Audi pattern to a Ford type 9 box (about €600), but I suspect your torque figures
will destroy that box in a fairly short space of time. You then move into the expensive realm of having a box strengthened or commissioning your own
bellhousing to fit a T5 box (or similar).
It's Evolution Baby!
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mcerd1
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| posted on 14/9/10 at 02:49 PM |
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remember that power is only half the story....
the torque of the V8 will more than make up for the extra weight in a strait line and in the middle of the right chassis your handling should still be
plenty good enough in the twisty bits
but I guess it comes down to the type of driving you'll be doing most of the time...
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coyoteboy
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| posted on 14/9/10 at 02:58 PM |
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It'll be primarily a weekend fun car, plenty of open country roads with good visibility near me, and some track usage if it's good enough
(would be nice!). Having driven FWD/RWD/4WD I have to say I've always wanted a 4WD super-light car for ultimate grip and cornering. My love is
not speed, but acceleration both straight line and cornering. I would happily top out at 100 (if I could keep a decent economy at cruise, moon on a
stick there!) for 90% of my use. I want it to stick like glue and go like it's got a rocket up its rear. I'm a function over form guy, but
the V's give me giggles so they're still in the picture, but I'm struggling to see a better choice than the 3S-GTE base currently.
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brianthemagical
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| posted on 14/9/10 at 03:24 PM |
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4 WD doesn't alter the cars ability to corner or increase grip over any other drive layout. If anything it just increases weight and application
of power would risk four wheel drifting, rather than the possible control through caerful power application afforded with a 2wd layout.
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coyoteboy
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| posted on 14/9/10 at 03:34 PM |
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It allows you to put additional power down without overloading the tyres as the force required to provide a fixed acceleration is now shared across 4
contact patches, not two, which provides superior traction through corners. Of course if you stick it in neutral and roll round corners then it has no
advantage  And 4 wheel slides are easier to control than 2, IME. This is generally why most people find even fast 4wd cars that are as quick as
their 2wd neighbours "boring" to drive - they're not, they're just capable of far more than the driver gives it. If they
allowed 4wd in F1 I assure you they'd take it up as fast as the rally guys did, despite having more dependable surfaces.
[Edited on 14/9/10 by coyoteboy]
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mcerd1
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| posted on 14/9/10 at 04:08 PM |
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quote:
Originally posted by coyoteboyIf they allowed 4wd in F1 I assure you they'd take it up as fast as the rally guys did, despite
having more dependable surfaces.
they did try it, but aerodynamics was a much bigger step forwards
you can't forget that the 4wd doesn't just add weight it also wastes more power (I've heard of 25%-30% losses on 4wd vs 10%-15% on
rwd)
dax have made a few 4x4 versions of the rush (admitedly just using the cossie 4x4 bits) - they changed to a rwd BEC (with or without turbos) as it was
quicker on the track
they reconed they gained more by loosing the weight that they ever would by adding the 4wd...
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hughpinder
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| posted on 14/9/10 at 04:09 PM |
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I think you should include a driver weight in your power to weight calcs - in a tintop it doesnt make much difference, but it will in calculations of
such light cars.
The actual weight of my zetec from a mondeo including gearbox, diff, driveshafts, engine mounts, alternator, all sensors, starter and a little of the
loom is 185 kg.
I think 30 kg for fuel/water/fan is is low, unless you are only having a 2 gallon race tank - especually if you have swirl pot/2 pumps etc.
I also think 80 kg for the "Hubs/Brakes/wheel assy x4" is pretty light - of course its possible, but you will have to have the lightest of
everything- even a 195/50/15 tyre weighs about 7kg, which would be 1/3 of your corner weight.
Send me your email via u2u and I email my excel sheet with actual weights. I am using 'cheap' rather than 'light' components
so you can look up your own weights if you want. (and all my other calcs if you want them)
Regards
Hugh
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scootz
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| posted on 14/9/10 at 04:28 PM |
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Another thing to consider in an Audi 4wd layout, the engine is waaaaaay out at the nose of the car!
If you don't have Audi's spondoolicks and R&D, then you're going to struggle to make that turn-in neatly with nearly 200kg
riding on the front bumper!
Not saying it's impossible (it clearly isn't), but not ideal!
It's Evolution Baby!
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coyoteboy
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| posted on 14/9/10 at 04:33 PM |
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mcerd - we don't have the benefit of aero
I had no intention of running "normal" 4WD anymore, but likewise this isn't a track race car. The original plan was to put in the
4wd system from a celica gt4, but that changed when I realised the packaging would be an absolute nightmare and leave it looking like a monstrosity.
The only 4WD option I was thinking is twin bike engines back to back, but it is a wacky and slightly questionable "because I can" option
Cheers Hugh, some good info there. I'll pop you an email. You're right, driver weight does make a bigger % difference on a light car -
I'll throw it in too.
Woowooo woo I was never considering the audi 4wd (or any car 4wd system!)
[Edited on 14/9/10 by coyoteboy]
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coyoteboy
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| posted on 14/9/10 at 04:50 PM |
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Original spreadsheet updated with driver weight (100kg, allowing for one heavy guy like me or driver and small passenger!). Colour coded green to red,
best to worst power/weight ratios.
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coyoteboy
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| posted on 10/2/11 at 12:33 AM |
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Updated the spreadsheet with some more actual weights of engines after some searching. Looks like the 3S "beats" the V8 with reasonable
costs, but is 100kgish heavier than a BEC with the related pendulus arse-ness Hidden the columns of less likely options (twin bike) etc.
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