CSR 200 and CSR 260 talk.

[pethier]

I just arrived back home in Minnesota after buying a CSR 260 in California and I have questions.

 

Because the CSR 200 and CSR 260 are a bit different from other Caterham cars, I thought I would start this thread to attract input from USA7s members who own, or have knowledge about, these cars.  

 

 

[pethier]

Who is interested this thread concept?  

 

Or should I start individual topics for each question?

Edited June 2 by pethier

[demoray]

I own a CSR260.  I imagine that long term, we'll be better served by having a distinct thread for distinct topics.

[pethier]

OK.  I will start that way.

[Croc]

@pethier  Makes sense to keep things separate as they are vastly different cars from the De Dion.  Nothing wrong with a stream of consciousness thread.  Enjoy Darren's ex-CSR.  Its been well developed over the years.  

 

In case you have never noticed, there is an extensive collection of CSR technical literature in the library.  As I find things I keep filing them there.  

 

[mccasksl]

Inquiry to the collective wisdom of the CSR folks:

What Duratec do I have and how to find out more about it? Focus 2.0L, Ranger 2.3L, block / head?

 

2005 CSR 200 

engine number: YDG0001 (no bar code found on front of engine (like my 29/05/08 2.0L Duratec) or rear bell housing mounting area as ref in the Ford/Mazda engine assembly chart)

Factory (Cosworth?) applied seal on front cam cover bolts: "000133 Cosworth" who might I contact / may keep records of the build / Cosworth applied seal / number? 

The block measures slightly taller than my 2008 2.0L Duratec, so 2.3L consistent w/ my understanding of 2005 CSR 200?

The intake ports and throats to the valves etc. are massive compared to my 2.0L Duratec but only have 5 bolts retaining the large intake plenum (no studs shouldered and non-shouldered as pictured / called for in Cosworth Duratec documentation, or seven bolts as per my 2008 Duratec)

Very large (compared to 2008 2.0L Duratec) intake plenum w/ cast individual internal trumpets) / one throttle body no multiple throttle bodies or roller barrels as per Cosworth Duratec documentation CSR 260.

 

A search of build documentation received w/ the car does not provide anything other than 2005 CSR 200. I've reviewed the cache of CSR documents uploaded to the USA7s site but may have missed something.

 

Any questions / words of wisdom would be greatly appreciated.

 

Cheers!

Steve

IMG_8292.MOV

Edited June 3 by mccasksl
typo correction, added video

[JohnCh]

Both the CSR 200 and 260 used the 2.3L, which has a 13mm taller block than the 2.0L. To get the extra power for the 260, Cosworth used more aggressive cams, higher compression forged pistons, forged rods, head work, and roller barrels.

 

Your comment about the visibly larger ports and throats is puzzling. I've researched this area a lot over the years, and the heads in both cars should be the same. The topic of Duratec heads is a little convoluted, so I'll share what I know based on that research and having had 2.0L, 2.3L, and 2.5L heads in my shop for comparison. If anyone has information that refutes the following, please jump in.

 

The 2.0L and 2.3L heads are the same down to the casting numbers. Each was available in either a low port or a high port version The better flowing high port design, which refers to larger reshaped throats, was used in the 2.3L Focus, and various non-US 2.0L Fords, whereas the low port was used in the 2.3L Ranger, all US 2.0L, and some non-US 2.0L Fords. My understanding is that Caterham has always used the high port in their Duratec-powered cars. The only head that has visibly larger port openings — i.e. the opening that mates to the intake runners — is the 2.5L. They are taller, giving a more squarish shaped appearance than the more rectangular openings of the 2.0/2.3L. The first photo shows a stock 2.0L low port, and the second is the 2.5L. 

 

 

[pethier]

On 6/3/2026 at 11:26 AM, JohnCh said:

Both the CSR 200 and 260 used the 2.3L, which has a 13mm taller block than the 2.0L. To get the extra power for the 260, Cosworth used more aggressive cams, higher compression forged pistons, forged rods, head work, and roller barrels.

 

Your comment about the visibly larger ports and throats is puzzling. I've researched this area a lot over the years, and the heads in both cars should be the same. The topic of Duratec heads is a little convoluted, so I'll share what I know based on that research and having had 2.0L, 2.3L, and 2.5L heads in my shop for comparison. If anyone has information that refutes the following, please jump in.

 

The 2.0L and 2.3L heads are the same down to the casting numbers. Each was available in either a low port or a high port version The better flowing high port design, which refers to larger reshaped throats, was used in the 2.3L Focus, and various non-US 2.0L Fords, whereas the low port was used in the 2.3L Ranger, all US 2.0L, and some non-US 2.0L Fords. My understanding is that Caterham has always used the high port in their Duratec-powered cars. The only head that has visibly larger port openings — i.e. the opening that mates to the intake runners — is the 2.5L. They are taller, giving a more squarish shaped appearance than the more rectangular openings of the 2.0/2.3L. The first photo shows a stock 2.0L low port, and the second is the 2.5L. 

 

 

 

 

For the 260:  Do you recommend 93-octane gas-station fuel?

 

Can I get away with 91-octane if 93 is not available?

[JohnCh]

44 minutes ago, pethier said:

For the 260:  Do you recommend 93-octane gas-station fuel?

 

Can I get away with 91-octane if 93 is not available?

 

Have you checked the owners manual in the Library?  The CSR 260 used 12:1 pistons, and doesn't have knock control, so I'd personally be more comfortable with 92 or 93, but it really comes down to how they set the ignition map. Given they sold that model in CA, where 91 is the highest available at normal gas stations, it might be ok. Hopefully an owner can chime in with real-world experience, rather than my speculation.

 

 

[demoray]

Earlier this year, I put a few gallons of 91 when I was nearly out and that was the only thing available in my 260.   It ran like garbage.  No knocking I could detect, but it had a far rougher idle.  After a full cycle of 93, it went away.  I won't be doing that again if I can help it.

[Croc]

Stick to 93 octane.  I know the standard ECU map is stupidly rich but it will start to knock on 91.  You can get away with a blend 91/93 but why would you unless it is an emergency (e.g. no other option while touring).  @pethier I think you bought Darren's CSR out of San Francisco?  I'm not sure that received a standard map when the second Cosworth went in? (from my admittedly fuzzy recollection).  If I was you I would assume you need 93 all the time.   Its a Cosworth engine so you have to treat it well - one of my favorite engines of all time.  

[pethier]

22 hours ago, JohnCh said:

 

Have you checked the owners manual in the Library?  The CSR 260 used 12:1 pistons, and doesn't have knock control, so I'd personally be more comfortable with 92 or 93, but it really comes down to how they set the ignition map. Given they sold that model in CA, where 91 is the highest available at normal gas stations, it might be ok. Hopefully an owner can chime in with real-world experience, rather than my speculation.

 

 

Thanks for the link to the file.  I don't yet completely understand how use the USA7s Library.

 

[pethier]

3 hours ago, Croc said:

Stick to 93 octane.  I know the standard ECU map is stupidly rich but it will start to knock on 91.  You can get away with a blend 91/93 but why would you unless it is an emergency (e.g. no other option while touring).  @pethier I think you bought Darren's CSR out of San Francisco?  I'm not sure that received a standard map when the second Cosworth went in? (from my admittedly fuzzy recollection).  If I was you I would assume you need 93 all the time.   Its a Cosworth engine so you have to treat it well - one of my favorite engines of all time.  

I am used to finding BP stations around the Twin Cities metro area, most of which carry 93 for my Cayman and my F-150.  The Cayman demands 93.  Ford is flexible, saying the 3500 twin-turbo ought to have 93, but the computer will adjust, and the truck will carry on with reduced power.  I have been using 93 in the truck as much as possible. I have identified 93 sources near Road America, for instance.  On the trip out to the San Jose area to collect the CSR from Darren, I seldom found 93.  I didn't really notice any power loss with 91 on the rig.  Other drivers, when they see my pickup with a full-width enclosed trailer on an entrance ramp, seem to assume it will be slow, but it got up to the speed limit  in a heck of hurry, even in 80-MPH zones at altitude.

 

I will stick to 93 octane for the CSR, as I do for the Cayman.  I have done better at finding 93 in the Central Time Zone than out west.  I drove the Cayman to the Porsche Parade in Oklahoma and managed to find 93 for the entire trip.

 

I didn't take time on my California trip to look for the supposed 93 source on the south side of the Salt Lake City metro.   I should investigate that before the LOG in September.

 

 

[JohnCh]

1 hour ago, pethier said:

Thanks for the link to the file.  I don't yet completely understand how use the USA7s Library.

 

You're missing out on a lot of valuable information. Click the Library link at the top of the page, then look for the list of folders on the right. The number next to each one identifies the number of documents it contains. There are a number of CSR-specific files in both the "Caterham Build & User Guides" and "ECU & Electrical" folders.

 

[pethier]

I'll try again.

[Croc]

Given I have owned a CSR for 15+ years, I have made it a point of collecting technical information over the years to help me.  It has been pulled together from other owners of CSRs I know globally.  All of that gets put in the library for sharing.