Newbie: CT26 to CT20b Direct Swap?

[TrevorV]

Just did a direct CT26 to CT20b turbo. Do I need to change the actuator as well. Car won't boost past 0.5 bar and start to splutter when spooling up.

Any help will be appreciated.

[shinny]

Hi Trevor,

As I said via text, you shouldn't need to change the actuator from the one supplied on the turbo.

I'm assuming you have a stock rev2 engine with standard rev2 ECU and AFM. You have remembered to reconnect the AFM, right?

The reason I ask is because it doesn't seem a millions miles away from how my car drove (or didn't!) when the map sensor vac hose fell off. On the rev3, that meant that the engine didn't know how much air was going into the engine and thus would under fuel when on boost and it would stutter about as far as 0.5bar tops. Now that's a rev3 (which uses the MAP sensor to meter air) not a rev2 (which uses the AFM to meter air), but I wonder if a disconnected AFM would have a similar effect?

[TrevorV]

Hi Mark,

I'll double check the AFM and all vac house have been reconnected properly

cheers.

[TrevorV]

All connections to AFM and VAC pipes checked, still no joy.

My understanding was that I could do a direct replacement from a CT26 to CT20b turbo on my MK2 REV2, but just wondering if I've missed something else.

I'm getting a lot more pressure coming through, as the standard dump valve is making a lot more noise than when the CT26 was fitted.

Maybe I got my information wrong, and this is not just a straightforward Ct26 to ct20b swap.

If I don't get any joy today I may have to put the Ct26 back in

[jimGTS]

100s if not 1000s have done this swap with no issues.

The only tweak needed is to use your old supply/return oil line, and that's it.

You need to check connections of other items, IC, afm, pcv etc.
Actuator pressure of both turbos are the same.

[TrevorV]

All sorted now.

It turned out to be the standard recirculating valve. Disconnected the hose and blocked it off, boosting fine now with no issues.

Either my circulating valve is duff or it can't take the extra pressure from the CT20b turbo.

So need some advice on a good dump valve that can handle the CT20b turbo pressure.

Thanks to the guys that have responded with some sound advice.

A big thank you to Luke at Pacific Works who gave my local mechanic a nudge in the right direction.