SLS what is most effective

s2t · newbie Joined: 22 Sep 2016 Posts: 30

I have some wiggle room with my power to weight ratio within the class. So have been pondering which way to go....increase power or reduce weight. With my car weight reduction would now be achieved by replacing the panels with carbon fibre ones so I suspect the cost between the two options would be in the same ballpark.
Whilst technically should end up with same result I suspect the power increase will pragmatically be more beneficial just interested what others think

AK

IMO i'd always go with saving weight over more power.

More power normally = less reliable, harder worked brakes and suspension.

Less weight essentially makes everything that little less strained. Easier to stop, easier to accelerate, easier to turn
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David Long

Tend to agree with Adam. Weight is the enemy, and the less you have of it the better it is for everything.
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s2t · newbie Joined: 22 Sep 2016 Posts: 30

Certainly wouldnt put added stress on the engine and increasing any potential unreliabilty

foz01

Add Lightness!

What car is it btw?
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Ali M · user Joined: 09 Jun 2008 Posts: 190

Provided you don't have traction issues and already have good brakes, I think power increase could get you more lap time improvement per BHP/ton than making the same change through weight loss.

Personally I would maximise the cheap / easy weight loss from removing things then add enough excess power over and above your class cut off that you can cancel out by adding in the maximum ballast allowed by regs. That way the ballast can be distributed around the car according to corner weights.

Weight loss is great but at Knockhill there is pit straight, railway and between chicane and Clarks that can all use a bit of power.

alistairolsen · established user Joined: 16 Nov 2007 Posts: 715

Weight will always be the better route, however I'd wager it's always more expensive once the free stuff is done and most people spend the money in the wrong place (sprung).

Looking at some previous posts, you're running a westfield, where there isnt a huge scope for weight saving anyway. Depending on what you mean by 'wiggle room', and assuming for example that you're in class C (210-270bhp/tonne) with a 600kg car with 156bhp at the wheels (260bhp/tonne), a 10 bhp/tonne increase is either 6bhp (fairly cheap and easy to find) or 22kg which is VERY expensive to find in a westfield.

Not knowing your current weight, engine and state of tune, it's hard to be sure, but unless youre way down on bhp/tonne I doubt it will make a lot of difference which way you go apart from in your pocket.

If you do go for weight saving, carbon panels is the wrong place to put money IMHO. Westfields are hampered by the unsprung/spring ratio and money should be spent on wheels/brakes/tyres/suspension to reduce the unsprung weight and get the suspension to work effectively. After that I'd be hunting top weight (cage) long before spending a small fortune to save a couple of kgs at the COG.

scottish scrutineer · established user Joined: 27 Mar 2013 Posts: 576

Less weight, especially unsprung or reciprocating/rotating weight. Lighter wheels and tyres, lighter discs. Remove unnecessary parts, lighter battery, less fuel, and lighter driver (no offence meant )
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Riggers · newbie Joined: 19 Sep 2015 Posts: 65

I'd go with less weight too , more power just helps you on the straights , less weight helps you everywhere
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Arch · user Joined: 14 May 2015 Posts: 158

Depends where you take the weight from it's easy to remove weight from the rear of a front engined car but a lot hard r to get it out of the front in the same proportions.

s2t · newbie Joined: 22 Sep 2016 Posts: 30

Thanks all for your comments -sorry havent been on here for awhile and didnt receive notifications of additional comments.
So first of all Remmy, driver weight loss - no offence taken and indeed this is part of the regime so far -5kgs since the early July SLS meeting!
Ok just to run through the numbers and yes I am running the Westfield. From RA Power at wheels 155.4 total weight incl me and 9kgs of fuel 632 kgs so power to weight is 245.9 as is and 248.6 with 2kgs of fuel. So to get to just under 270bhp/ton I would need to increase horsepower at wheels to 169 an increase of 15 so lets say 20hp at flywheel or reduce weight by 50kgs.
Now we are talking a Suzuki Hayabusa engine so things arent quite as simple as a car engine for 'bolt on power' especially when it is a relatively modest number. The standard hayabusa engine at the flywheel is 175hp to achieve +20hp I would need a new set of cams a different crank and possibly rebore.
On the weight side the car is pretty light, has a lightweight battery, Team Dynamics Pro Race wheels 4.5kgs each, could loose another .5kg I suspect using split rims, running Nitron Shockers which seem to be reasonably light may save a few gms with the springs, lightweight 4 pot calipers, solid rotor. Full rollcage is I think about 12kgs but I wouldnt want to mess around with that.
However since writing initially the weight has started to come out of the car -12kgs for the passenger seat -2.5kgs replacing double aeroscreen for single smaller screen...other bits and bobs removed lets say 2kgs so total 17kgs plus my 5! so 22. Technically the P/W is now 258
So increasing power at wheels by 8hp would therefore achieve my goal. I will need to investigate this as just dropping in a different set of cams may well achieve that.
The weight loss programme will continue (especially on me) having raced yachts previously weight was never a huge issue but this has given me a personal challenge
(Sorry this has gone on a bit)

AK

Yup, 8hp seems a lot more achievable and may be possible from just a remap/exhaust/inlet tweaks. Is it just a 'standard' map on the ECU just now?

Cams may just shift the powerband up the revs a bit, and make it less driveable in the lower ranges
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Impreza Race Car - SLS/SMRC
Mini Race Car - SMRC
911 - 1981 Air Cooled 3.0
500 - 1969 Fiat 500 L
Toureg 262 RLine
Track Scotland

Garry.M

With that sort/spec of car I'd go for power
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nefarious · user Joined: 02 Nov 2008 Posts: 218

I know it's off topic a bit, but I found very good lap-time gains through some basic aero mods to my Westfield (230bhp redtop, 570kg).
The vast majority, I suspect, was from a front-to-rear flat floor in 1.2mm ali, rubber sideskirts, and slotted vents in all the wheel arches. Weight penalty was 7kg, but I got most of that back by switching to a Lithium battery (4.5kg saving over the lightweight racing one in there before).

Progress report: http://www.trackscotland.co.uk/forums/viewtopic.php?t=7867&start=0 (although photos now gone thanks to bastard Photobucket)
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nefarious · user Joined: 02 Nov 2008 Posts: 218

Oh yeah - just remembered - I saved about 2kg switching to an ali rad. Was a standard VW Polo one before (steel/copper?), but when I replaced it the "OEM Alternative" from Dingbro was aluminium and only £30. Cheers!
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