620 tuning

[Amris]

fergus said:

Very high quality dampers, valved to suit, with appropriate spring rates, all setup on a flat floor with suitable geometry.

That way, you can both get the power down and go round corners. Amazing

Agree, suspension is the only thing I would be changing on a 620! I would go single way adjustable so you can quickly change between track and road.

[bcr5784]

xcentric said:

given the tune of the engine already, I think you'd be better focusing on improving the aerodynamics to make it go faster and give it downforce and not lift..... that's the most cost-effective way to make it go faster and better.

I'd agree with that - but does anyone know how without completely altering the style of the vehicle? There are some fairly obvious things like fitting an aeroscreen, solid tonneau cover and possibly CSR style cycle wings. But I doubt that will do much for front end lift and the understeer that results from it.

[griff7]

grenpayne said:

k20erham said:

Hi when you take out the ECU as it's locked to replace it with something you can tune, take out the loom and the lump of scrap that's fastened to it they call it a Duratec I think, then replace it with something from Terry Bourne. keep the Sadev box but put Geartronics on it.

Obviously we're talking K20s here I'm pretty familiar with the K20 having owned a Civic Type R and whilst it's a great engine it's not exactly an easy install is it? And my understanding is there aren't that many around now? So isn't it a bit unfair to call the Duratec 'scrap'? It certainly is reliable at 300bhp and works well in the car.

The Duratec is the best all round engine that Caterham have fitted IMHO especially for circuit racing.As said above 300+bhp is now reliable with effortless torque and mated to a Sadev box is superb.

Andy

[SimonRogers]

No understeer necessary if you fit the correct damper spring combination.

[bcr5784]

SimonRogers said:

No understeer necessary if you fit the correct damper spring combination.

Fundamentally you can get rid of understeer at modest speeds by the conventional changes of rear ride height or rear roll stiffness, but the increasing tendency to understeer at higher speeds is a consequence of front end lift. Practically speaking it's impossible to get a neutral balance at both high and low speeds without reducing front lift - which would need some fundamental aerodynamic changes to achieve.

According to Caterham the aerodynamic tweaks on the CSR (ducted radiator, strakes and changed cycle wing profile) reduced lift significantly - but definitive figures for lift and drag are hard to come by - a pity, because, dire though they are, windscreen, wings, and the various things Caterham have done do make a difference.

Edited by bcr5784 on Friday 9th December 21:37

[DCL]

bcr5784 said:

Fundamentally you can get rid of understeer at modest speeds by the conventional changes of rear ride height or rear roll stiffness, but the increasing tendency to understeer at higher speeds is a consequence of front end lift. Practically speaking it's impossible to get a neutral balance at both high and low speeds without reducing front lift - which would need some fundamental aerodynamic changes to achieve.

According to Caterham the aerodynamic tweaks on the CSR (ducted radiator, strakes and changed cycle wing profile) reduced lift significantly - but definitive figures for lift and drag are hard to come by - a pity, because, dire though they are, windscreen, wings, and the various things Caterham have done do make a difference.

Edited by bcr5784 on Friday 9th December 21:37

That may be true in a generic terms, but specific to 620 is the additional weight it carries up front. That just needs more attention to sort than say a lighter k-series. So using a good quality adjustable shocks gives you the ability to work the front harder without destroying rear end grip, or grip overall for that matter.

[bcr5784]

DCL said:

That may be true in a generic terms, but specific to 620 is the additional weight it carries up front. That just needs more attention to sort than say a lighter k-series. So using a good quality adjustable shocks gives you the ability to work the front harder without destroying rear end grip, or grip overall for that matter.

Accepting what you say about weight (and the effect the strakes and ducted radiator have) the fundamental (if reduced) problem Caterhams have with front lift remains - whatever balance you create at modest speeds will inevitably transition to greater understeer at higher ones. From what I read the CSR reduced front lift from 100lb to 50lb at 100mph. Not sure how valid the figures are - but either is big (or vast) for a car only having 600 or 700 pounds on the front axle to start with. And obviously it will be much greater at the sort of speeds a 620 is capable of.

Edited by bcr5784 on Saturday 10th December 21:19

[SimonRogers]

But it all depends on the setup of the springs and dampers. I take your point but the degree at when this becomes an issue is shifted vastly with good set up and dampers.

I always used to run the regular 15mm of rake. I am now down to 5mm and zero understeer! I am also carrying a much larger rear tyre size in proportion to the old set up.

Pinpoint turn in and also able to just hit any kerb without fear of upsetting the car.

[bcr5784]

SimonRogers said:

But it all depends on the setup of the springs and dampers. I take your point but the degree at when this becomes an issue is shifted vastly with good set up and dampers.

I always used to run the regular 15mm of rake. I am now down to 5mm and zero understeer! I am also carrying a much larger rear tyre size in proportion to the old set up.

Pinpoint turn in and also able to just hit any kerb without fear of upsetting the car.

I think all you are saying is you can trade rake for rear roll stiffness (relative to front) to achieve the same effect on mechanical grip balance - which is obviously true. On a race series car your options are limited by regs and on a 620 you have more degrees of freedom. But aero overlays all that, and obviously only affects higher speeds to a significant degree. Unlike on an aero car you cannot alter aero balance to any significant degree, and will always tend to understeer in a Caterham. That's all I'm saying. Unless you have some secret Caterham aero tweaks you will be subject that too. Mind you, personally, I'd prefer a bit of high speed understeer on a 620 rather than wearing brown trousers or having my balls shot-peened.

[SimonRogers]

My own 7 is not at the same power level as a 620 but it's not slow.

It has zero understeer in any type of corner at any speed, power on or off.

Clearly aero would allow it to corner faster but in terms of balance there is nothing to change.

[bcr5784]

SimonRogers said:

My own 7 is not at the same power level as a 620 but it's not slow.

It has zero understeer in any type of corner at any speed, power on or off.

Clearly aero would allow it to corner faster but in terms of balance there is nothing to change.

I'm bound to feel that you are probably not being as critical as a professional racing driver might be - Formula One teams fail to achieve that consistently.

[DCL]

bcr5784 said:

I'm bound to feel that you are probably not being as critical as a professional racing driver might be - Formula One teams fail to achieve that consistently.

I think unless you have bought a set of 'top end' shocks from Simon, and used his recommended setup, there's no point in arguing. There are those of us that have, and what he says is quite achievable.

[bcr5784]

DCL said:

I think unless you have bought a set of 'top end' shocks from Simon, and used his recommended setup, there's no point in arguing. There are those of us that have, and what he says is quite achievable.

There is no point in arguing - if there was such a magic set-up (on any car) race engineers would be out of a job

[dino ferrana]

I believe in an early iteration of the Caterham CSR it had a moustache-like chin spoiler, but it upset the balance so much the car drove like a Scalextric car. I think it had a tendency for the rear to come unstuck even in a straight line!

[Bob Sheeley]

I've recently bought a 620r.
I've done a couple of track days and am well pleased with the car so far.
I found playing with tyre pressures got rid of mild understeer.
Any more thoughts re tuning and/or suspension mods?
Bob

[nigelpugh7]

Bob Sheeley said:

I've recently bought a 620r.
I've done a couple of track days and am well pleased with the car so far.
I found playing with tyre pressures got rid of mild understeer.
Any more thoughts re tuning and/or suspension mods?
Bob

Hi Bob,

If you are interested, you might want to join us on the dedicated 620 owners Facebook group, we have a lot of 620R and 620s owners, who have experimented with a range of suspension options, and got some fantastic results.

Send me a private message with your email and I can send you an invite.

[Mitch911]

Bob Sheeley said:

I've recently bought a 620r.
I've done a couple of track days and am well pleased with the car so far.
I found playing with tyre pressures got rid of mild understeer.
Any more thoughts re tuning and/or suspension mods?
Bob

Speak to Simon at Meteor Motorsport, knows his stuff and his all round service is brilliant

[upsidedownmark]

glailey said:

I have driven it a bit. I agree not enough to know that I would want to spend a very large amount money money tuning it just yet. But I also know how much fun I have had upgrading my current car. Hence the hope I got to play the same game with this one.

I'm a sucker for modifying for more performance having experienced how much a production car seems to leave on the table.
The suspension, toe links and top arms Lichfield have created for the GTR makes the car incredible and more than capable to deal with more power. Surely there is more to be had in the 620.

With this in mind, DCL I'm really interested to know what changes you would suggest to the suspension?

To the question of "Jesus you want to make it faster" , absolutely. As long as faster isn't worse.
I'm not looking for faster for faster sake. I'm looking to make everything about the car just that little bit better and therefore faster, more exciting, more ridiculous, and therefore more giggle inducing.

However sadly no one has come back to this post saying....these guys are brilliant....go and see them...they may be in Scotland,but they will build you the best 620 in the land.

Yeah, but.. apples and oranges. A GTR is a very heavy, production oriented car with an inherently compromised suspension design (before you even talk set up), too much mass and a lot of power. A caterham is a rather different proposition and rather more single minded of purpose.. and a 620 is a fairly evolved version of the breed.

[bjd7326]

Apologies for appearing stupid, you refer to Rake... is this camber or caster or have i got it totally wrong?

[Matt W]

Rake is how much more ride height there is at back of the car than the front.