CT20 Qs

[GT4 20]

Once I get some forged pistons in, the plan is to run around 23psi with the aid of an Apexi Power FC ECU and Profec B Spec II.
Just wondering if the OE wastegate will need upgrading to handle that boost, or will it need a stronfger spring to help prevent boost creep?
Cheers
Gary

[vvega]

it would be sensible to upgrade the wastegate
that woudl let you get the best out of your gain in turn letting you build boost faster

it will also help with that with running that sort of boost you really sould be looking at a slightly bigger a/r exhaust to keep exhaust presures in check

just my views


v

[Al]

Boost creep? ct20bs dont creep.

[GT4 20]

So upgrade wastegate or leave as is?

What exhaust A/R upgrade? Are we talking bigger turbo here?
Gary

[Al]

If the wastegate presents a problem in reaching your goals get a better turbo.

[Dell'Orto]

Boost creep? ct20bs dont creep.

Yes they do! Well, mine does....hopefully its something small, and not a torn actuator diaphragm

I still think 23psi is too much for a CT20b to push efficiently.

[GT4 20]

There is no issue with current set-up - 1.2bar. Just wanted to know if there is likely to be an issue with upping the boost to that level.
Gary

[Al]

Yes they do! Well, mine does....

1.25bar and no creep for me.

[vvega]

IMO you really sould be looking to a more suited turbo
maybe a gt30 would be more suitable

i cant see 23 psi been much different than 20 psi but i guess dyno results will show

i think fivebob has some compressor maps for it maybe he will pop is and tell you when you go into surge

es a/r is important as you dont want to much pressure in the ex manifold as this can start to cause issues with cylander fill and turbine logtivity


v

[fivebob]

You won't have a problem with boost creep, but a CT20B won't hold 23psi, in fact it's pushed to hold much more than 18psi to redline. Also, judging by the compressor outlet temps I have seen, it would be well out of it's efficiency range.

IMO it would be far better to upgrade to something like the GT28RS ,or a GT30 if your goals are greater than 350HP.

[GT4 20]

How much difference is there between a GT28R and a GT28RS?
Gary

[vvega]

a gt28 is really just a t28 with a bb core more of a sidestep from your ct20
the 28rs has a uprated compressor and comes in different forms
the gt2840rs has a gt40 compressor on it

personally id think a wll matched gt30 woul be the way you want to head

the other option would be to4e
not bb but stull a hell of a good turbo for the price
you can get them here for under 800 brand new and with the housings of your liking



v

[GT4 20]

I assume that neither are twin entry turbos - do they bolt straight on to the exhaust manifold, or are extra mods required?
Gary

[vvega]

the tdo4's come in a split pulse design im nusure if the gt series do as well .......i would hope so

they will bolt on to your manifold with a adapter plate

i would recoment a manifold ethier way
that way if so desired you could have your external as well as a few turbos of thios level dont have internals


v

[vvega]

[GT4 20]

My only real concern is lag. A BB turbo combined with a tubular manifold would certainly help. At the moment, full boost comes in at around 4000rpm - don't want to make it any laggier than it already is. Any idea what the GT30 or TO4E are like lag wise?
Gary

[Scottie]

Fullboost at 4000 on a steel CT20B? Do you have a FMIC or something?

[vvega]

i have yet to understand why people think that turbo power comes without tradeoffs
one of those is lag

a turbo is not magic you cannot just keep winding it up and expect it to work
i guess by the fact you wanna run 23 psi you want more power
well a side effect will be lag or lag management i.e antilag
yes a bb will help but not that much

a properly sized turbo for what yopu want will not be much laggier than you have but it will be lagiier and come on later with some ferocity
trade off for this will be cost
a branded bb turbo can cost upwards of 2 grand with your selection of housings to get the best from it
all said and done its quite probably a $5500 + exercise
a floater will be around the 3-4000
is that what your willing to spend ??
what interccoler do you plan to run ??

the path we are starting to head down needs far more info than you have provided for a effective answer
what ecu do you plan to run ??

sorry if im abrupt but need to see wht you can afford or are willing to spend before we start talking moonbeams and antilag system

antilag turns your turbo into a throw away item so is not ideal for a abb system unless you have big notes to race with
then a to4e will not be laggy at all and cheap
and will give no less preformance
dose boost from idle sound like something you want ???

specailyy costing 1/3 of a bb turbo and also been more robuxt(bb turbos can be a bit sensitive in my experance)

have a think and deside what you wanna do

[GT4 20]

I fully appreciate the trade offs which come with a bigger turbo. Will accept a bit more lag - just don't want something which will come on boost at 5k plus! Please don't treat me like a complete idiot. I value your imput - but not if you're going to be condescending with it. After many years of working on Rovers, Toyotas and assosciated turbos are new to me.
I am currently building a Rover 220 rally car with a GT28R turbo which coupled with a tubular manifold will spool up fully at around 2600rpm. I have no experience with 3S-GTEs, GT30s or TO4Es, hence the questions. If you don't like my questions then either don't respond, or tell me to go elsewhere

Antilag is not an option as far as I'm concerned. Don't want to be replacing the turbo/manifold every few weeks. It's not even going to be incorporated into the Rover set up.

Plan is to stick with the OE air to water set-up on the GT4. Will improve it slightly by lagging the underside of the heat exchange unit as well as fitting a functioning water sprayer for the pre-rad.

And as for boost from idle, not even thinking of the supercharger route
Gary

[GT4 20]

Fullboost at 4000 on a steel CT20B? Do you have a FMIC or something?

No. OE set-up. What's it meant to spool up fully at? I haven't driven another WRC GT4 to compare.
Gary