Jump to content
Click here if you are having website access problems ×

Caterham HPC


Jules Martin

Recommended Posts

I know I am a "K" series man but I have a serious question for all you Vauxhall engine experts.

If you had a bog standard HPC and were looking to improve it's performance on a fairly tight budget, where would you start ?

The obvious things are adjustable bilstein front dampers, perhaps suitably shod 13" wheels; but what about the engine ? How could £1000.00 be best spent ?

I would be grateful for any advice.

Thanks,

Jules

 

 

Link to comment
Share on other sites

Barry,

 

£1000 goes a long way in your part of the world......

 

I would go Tyres and Dampers - even if it has race Bilsteins I would get rid of them and get something with more appropiate valving.

 

For a road and track car ACB10's are the obvious choice so long as you've done the dampers first. This eliminates the querky handing charecteistics that so bogged the SLR.

 

If your not going on the track go for CR500's

 

Jules, Unlike the K, you dont have to start developing the engine with exotic cranks rods and camshafts to get a car with reasonable pace.

 

Arnie Webb

Organiser- L7C Le Mans Trip

To book for this years Le Mans Trip see The Le Mans Trip Website

It really is very very very very full now!!!

 

Edited by - fast arnie on 9 Feb 2001 10:41:47

Link to comment
Share on other sites

Personally,

 

1 - 13" wheels and CR500's or Yoko's

2 - carbs (if it's Vx standard injection). If money allows - TB's.

 

over budget now but already a huge difference.

 

3 - cams - the standard Vx is so under tuned. Cams make a huge difference.

4 - suspension - Personally I think the standard Bilstein setup is pretty good and the progressive rears are a good compromise. Worth checking the setup against a sorted HPC.

4 - gearbox - SPC / Quaiffe closer ratios

5 - front brakes - Alcon if price is an issue.

6 - deeper pocket light pistons, steel rods, porting, race springs, bigger valves, dry sumping, slicks, turbocharging, nitrous

7 - Carbon wings tongue.gif

8 - R500 aero wishbones teeth.gif

 

Alex

 

 

Edited by - Alex Wong on 9 Feb 2001 11:31:27

 

Edited by - Alex Wong on 9 Feb 2001 11:32:12

Link to comment
Share on other sites

It's an 'HPC' with a Vauxhall. So it should already be on Webers. The first thing I'd do is fix the gearbox ratios/shift and fit a much lighter flywheel/clutch.

 

It should be possible to trade a set of HPC wheels for a set of 13*6. Tyres are disposable so their cost doesn't factor in as a 'mod'.

 

Paul

Link to comment
Share on other sites

On reflection.....

 

Swap the cartwheels for 13 inchers and Yoko's

 

Wide track - reduces the understeer and upgrade the rack to a 22% type - £500

 

LSD ramp mods and reducing initial loading settings move understeer to end or out of corner. £300

 

Set of adjustable plaforms for STD bilsteins will get the cornerweights more desirable )or alternatively a side exit exhaust (HPC's cam std with a underfloor rear exit system.) £200

 

There's my £1000 spent.....

 

Alex - does your browser add an extra zero to currency figures????

 

 

 

 

 

Arnie Webb

Organiser- L7C Le Mans Trip

To book for this years Le Mans Trip see The Le Mans Trip Website

It really is very very very very full now!!!

Link to comment
Share on other sites

Andrew,

 

The Race Bilsteins Caterham sold with the VX cars were over damped and non adjustable for rebound. The range of bump adjustment was minimal, so Caterham overcame this by fitting springs which were too soft, hence the cars whould hit the bump stops when driven hard over bumpy surfaces (although they tended to work OK on billiard tables and most tracks)

 

The result on a road car was a high degree of instability at high speed on bumpy surfaces - to the extent that you could drive fatser in a tin top straight bumpy roads as you had the reassurance that you were not going to be pitched off line and hence off the road.

 

This was addressed when the faster K cars were introduced ( the 1.4k was nopt really capable of the speeds this problem occurred at) by the discontinuation of thertace damper and an adjustable plaform road damper being added to the line-up. I think Caterham had made Bilstein valve these more appropiately for the weight of the car so the low poundage springs tend to owrk on the newer cars.

 

No other type of car I have ever driven, (including a Mazda RX7 which has only about 2" of suspension travel) suffered this problem, as no londer does my Seven which fitted with Spax "Trak Spax" Alloy dampers (.95kgs each!) has the bump and rebound valving ganged by a single adjustment knob. Diferent valves can be used depending on the strength of the spring used, and the range does not go from zero to max but rather itgives 12 settings between the mid low and m,id high points.

 

With the Caterham Race Bilsteins many people would beef up the springs to 400 or 500 lbs, which resolved the bump stop problems, but made traction and comfort unbearable. There are also stories that ArrowStar had a couple of chassis break with this extreme springing!

 

 

 

 

Arnie Webb

Organiser- L7C Le Mans Trip

To book for this years Le Mans Trip see The Le Mans Trip Website

It really is very very very very full now!!!

Link to comment
Share on other sites

Jules, I take it this is Robin's car. From my limited experience in the driver's seat I would recommend some care and modest ambition. For a start, it should be ensured that all the components that are there are working properly.

 

Given that the handling was very ropey, I would suspect the front dampers.

 

Bilsteins. They may not be *ideal*, but you and I know that they work.

 

Inspect the whole steering gear to ensure there is no stiction.

 

Ensure the rear radius arms are in the lower position. Adjustable platforms on the back to tune the rear steer.

 

Springs don't tend to give up working, so presume they are right although they are cheap to change if you can't determine their rate. The fronts should be ~300 lb/in. The rears could be the standard progressives or otherwise nothing higher than 150lb/in. A 5/8in front ARB would be a good match.

 

IIRC, it is a plenum injection VX. Any engine mod should concentrate on improving the manners first and foremost rather than the out and out power. Throttle body induction will need some form of 3D mapped ignition/injection. This would use up the budget, give a bit more power and much better manners.

 

What Paul says about the flywheel and clutch and gearbox are also true.

 

An LSD could be somewhere in the priority list.

Link to comment
Share on other sites

Having had a Vx inj myself, my priorities would be:

 

Carbs to get the power up to a more sensible level (and cams if I could afford it)

 

Lightened flywheel (absolutely essential)

 

14 or 13" wheels and Yokos

 

Better gear ratios (ideally with helical gears)

 

Slightly above budget, but the above will transform the car

Link to comment
Share on other sites

Peter

What difference does the rear radius arm position make?

Is it noticable for road use or is it more suited to tracks?

On my 7 the lower position has no thread. What is required by way of washers etc to move this. Does the inner panel have to be removed to drill a larger hole? I assume the ali panel would just wear away leaving a loose bolt.

 

Thanks in advance James

 

Link to comment
Share on other sites

Depending on year of manufacture, I would start by checking anti roll bars are fitted front and rear to the correct dia. and not the latter post 96 "camp bed leg" dimenions, next the gearbox should be put out to graze and replaced with SPC item, next a set of cams (not yet done but due this year), followed by big brakes and master cylinder.

 

P.S. all this assumes that you are already on 13" wheels

Link to comment
Share on other sites

Arnie

 

Thanks for your advice the other day.

 

The characteristic you describe is familiar, but with 13 inch Yoko 21s the car I have now is better than my last, a Supersprint with Prisoners and NCT tyres, so I had just decided I needed to drive it better and enjoy the power. It would be nice to point and squirt at the same time however.

 

I had a look at Trax Spax in the DT catalogue and saw a variety of lengths and spring rates. Did you decide what to buy by trial and error or did you just go for the 150-350lb version? Presumably you can decide on length by measuring the old ones?

 

I think I saw you mention that you had an anti roll bar fitted by Juno sports Cars - are they the people to talk to on Suspension generally?

 

Finally, I have seen some Leda dampers supplied by James Whiting - did you consider these as an alternative to the spax. They seem to be intended as a cure for the same syndrome and they are a little cheaper.

 

AJSenior

Link to comment
Share on other sites

Andrew

 

The Leda's are also good, but heavier than the Trak Spax. The Leda's only come rubber bushed from JW. My Trak Spax are rose jointed all round, but I had to get special fittings (cones)made to attach them to the chassis.

 

The 150 - 350 lbs represents the adjustment range on the valve - ie. position 1 is for a 150lb spring, position 12 is for a 350.

 

As for lengths, even Spax screwed this up first time, but I think this is because I was running wide track.

 

 

 

Arnie Webb

The Fat Bloke blush.gif in a Slow Old Vauxhall wink.gif

Link to comment
Share on other sites

Post 96 camp bed! I'm refering to the almost non existant front anti-roll bar combined with the totally extinct rear anti-roll bar, which makes for a very soft car!

 

Mine was constructed as above, following a test drive in an older Vauxhall (mine was sick with broken 3rd gear @3,000 miles)the parts were ordered and fitted before I would take it out again.

 

Gordon Cardew has had a simiular experience with his K-Series, so you can imgine what it would be like on a Vx.

Link to comment
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now
×
×
  • Create New...