Caterham Sprint- Carburation or Injection?

[Elise111]

Furthering my learning curve with my new (to me) Caterham. It is apparently a 1600 engine, so I think that means its a Sprint and not a Super Sprint. In any case, it has a DGEV 32/36 clone downdraft that turns out to be as bad as the many reports out there, not to mention the large cutout in the hood that was required to fit it. It all makes the decision to change easy. Options are Weber DCOE 40's, Dellortos, or bike throttle body injection. Seems injection is going to be the best for drivability but probably the most effort to make the change. Does it take the soul out of the 7? Let me know your views!

[SCse7en]

Soul is it! Fuel injection? Predictable and good for moderns but nothing makes music like a set of side draft Webers!

They add to the whole "low flying" effect....

[JohnCh]

I’ve had three different engines with DCOEs and one with Jenvey Direct to Head Throttle Bodies. To my ears the sonic signature is similar. The Weber fed engines did seem to go a little deeper, a little more baritone, but that probably has more to do with them running a bit richer than the FI car which is easier to get right A/F ratios across the rev range.

 

When done correctly, a FI system will provide a better torque curve, easier cold starting, better fuel mileage, and is easier to tune when you make upgrades. Part of this is down to the 3D nature of the ignition – which you can also add to a carbed engine – and part down to the granularity and flexibility of the mapping. But it is also far more expensive, and requires far more effort to install. You need a swirl pot, high pressure fuel pump, high pressure fuel line, high pressure filter, injectors, wiring harness with various relays, ECU, new coolant & air temp sensors, ITBs, TPS, crank sensor, crank trigger kit which involves modifying or replacing the crank pulley, etc. I’ve been there, done that. It’s a big project.

 

Before making the decision, I’d give thought to your plans for the car and what you like about the se7en experience. Is it scratching a vintage car itch or is it the best way to have a visceral driving experience in a modern world? Are you just changing the induction, then stopping, or do you think you will upgrade the engine (1700 cc, pistons, rods, cam, head work)? Any longer term thoughts of an engine swap to a Zetec or Duratec for a significant power jump? DCOEs and ITB-based FI are both great options, but they do scratch slightly different itches.

 

-John

[JohnCh]

One more thing regarding the question of soul. I've never found a difference in that respect when driving, but it definitely exists in the ownership/maintenance/tuning aspect. Using a laptop to make changes, or using data logs or a multimeter to track down a problem is far less soulful than changing gaskets to stop raw gas from seeping out, tweaking float heights, or playing with a various combinations of jets, emulsion tubes, and air correctors.

 

-John

[Elise111]

Thanks for the well considered responses. I am likely going down the path of dual Webers now. I have found the short style manifold in the UK. Since I don't have any reference for this installation, can anyone guide me on the linkage? All the images I see of Caterhams don't show the linkage, so I assume it is under the carbs. Weber offers a under mount linkage, does it fit in the Caterham engine compartment space?

Pete

[DavidL]

Where are you located? It might be easier to look at a car. I've got a 1700 Super Sprint X-flow with dual 40 DCOEs in my '90 Caterham. you would be welcome to come and see it, I'm in the San Francisco Bay Area (Menlo Park).

[coffee break]

The carb setup on my xflow is 2 Webers. The cable pulls down and is located by a steel fabricated bracket that attaches to (bridges) the carbs.

[coffee break]

it has a DGEV 32/36 clone downdraft that turns out to be as bad as the many reports out there

If you are interested I have a Weber 34DGEC you are welcome to have until you firm up your plans. Send me a PM if you are interested.

 

I have toyed the idea of replacing the Webers with ITB's but wasn't interested in all the fettling John was describing. I decided to leave the car old school.

[speedwagon]

there is a carb geru on thesamba.com who has info for making the Weber progressives work right. they were a kinda/sorta popular carb on air cooled VWs. the info can be found here; https://www.thesamba.com/vw/forum/viewtopic.php?t=386388 carb acts all the same on any engine of same size. Save money--drive car more = happiness. john (dinks with rotorery air VW and ford small blocks)

[Elise111]

Thanks again for the responses. I'll check with Redline in UK about the Caterham specific steel bracket for the throttle linkage. Follow on questions:

 

1. I assume 30mm chokes are ok based on some other posts. This is what the carbs come with standard. I also assume that I'll have to play with the standard jets. I think mine is a 1600, but until I take the head off, I can't be sure. In any case I see reference to 30mm chokes for 1600 and 1700, so hopefully this is fine.

 

2. What length of trumpets fit?

 

3. What height of air cleaners fit? Note that I am a ~1987 chassis, so nothing widened.

 

I will order my parts from the UK next week. Thanks for the continued input.

Pete