2014 Caterham roadsport 175 duratec conversion to ITB's

[Drakman]

Hello everyone,

 

I am going through the process of converting my 2014 Caterham Roadsport 175 to Jenvey ITB's.

My car is mostly used as a road car however i have made a few upgrades, suspension, Haltech ECU and a R500 exhaust system.  I have  a set of Kent D-Tec 10 cams that will be going in the engine when i fit the ITB's.  The car as standard is Drive By Wire.

I have contacted a couple of Jenvey dealers and been given quotes for 48 mm and 45 mm ITB's along with a choice of Electronic throttle actuator (Drive By Wire) or converting to a cable pull accelerator.

My questions are 1, what would be better suited to a mostly road car 45 or 48 ITB's. 

Question 2, what are peoples thoughts on Drive By Wire over cable actuated accelerator?  The Electronic Throttle Actuator looks to be a heavy addition on a car that wants me to add lightness.  What do you guys in the UK do in this situation, cable or stay with DBW?  

I will be doing a couple of track days a year and in all honesty the Caterham is not ever going to be a daily drive car. 

 

Cheers

Dave

 

 

 

[aerobod - near CYYC]

Hi Dave,

I would think 45mm is a better match to road use and low-end torque due to the higher air flow velocity with what will likely be 210-220bhp when complete with the DTEC10 cams. I'm currently rebuilding my engine with the Jenvey/Raceline DTH 48mm throttle bodies with DTEC35 cams and a target of 250bhp, but more of a bias towards high end power and track use.

I would stick with cable throttle actuation overall, as the DBW system is only really a benefit when it interacts with other systems and uses the enhanced ECU capabilities that are not really present in the MBE unit, so I expect the Haltech unit is also not 'feature enhanced' to make best use of DBW.

[Drakman]

Hi James,

Thank you for your thoughts, i think you are right about the 45 mm vs 48 mm ITB's, the inlet valve is going to be the restriction in the system not so much the ITB's or the porting.  A standard inlet valve is 35 mm? my cylinder head is one of the "hi port" designs but i don't think the valve size is any larger.

As for the throttle actuation my car is already drive by wire (can't say i am a fan of it though).  I don't know much about the ECU's used in modern cars these days.  When i had the Haltech fitted i was told i could have it set to swap between 2 maps if i wanted to use E85 fuel as well as 98 petrol.  I don't know what else it can be set to do though, i had it fitted for the tunability so i could make some changes to the engine performance.  The cable is a simple probably lighter and cheaper option, i might have to explore the cable idea a bit more.

 

Cheers

Dave

[7 wonders of the world]

Hi port heads have the same valve sizes 35/30, oversize valves are available, the inlet valve is no restriction though as will a little porting you can see 280bhp on stock valves.

Are you keeping OEM pistons and rods - if so this will limit the rpm,

If your changing these I would opt for a different cam and 48's you wont loose torque with the larger TB's as you would in Carbs,

As James DBW offers no real performance benefit,

Multi maps can be used for different fuel grades, a 'race' map, open loop map in case of O2 sensor failure or a touring map, I have 3 on my K3 Emerald

Dont forget some decent valve springs.....  

[Drakman]

Hi 7 wonders,

Thank you for your advice, i was thinking that 45 mm itb's would produce more torque than the larger 48 mm but i really have no experience with ITB's so i might just go that way now because 48 mm would be better if the power bug bites down the track.

It looks like i will go with the cable accelerator as well, cheaper, lighter and simple.

Yes i will be keeping the stock bottom end for now so i am limiting engine RPM to 7,500 max which is one of the reasons i chose  the D-tec 10 cams.

I have been following the valve spring dramas here so i am aware that they could be an issue.  I don't think overly heavy valve springs are a good thing though.  Does anyone make Titanium valve springs for these engines?

Cheers

Dave

 

[7 wonders of the world]

Kent do Ti caps,

if your investing a fair sum as you will be wort looking for steel rods and pistons which allow you to explore up to 8500rpm, maybe go for a slightly longer duration cam and mild porting and you will be knocking on the door of R500 spec.... and only one mapping session too... so saving you money..