Celica Gt4 Mods

[Jonny0069]

Hi I have read a lot about my gt4 Im not sure if anyone remembers me but the reason i joined here was I was going to try and make a rev 7 celica into a gt4 but realised it cost to much and did get a few prices but was then let down so decided to sell the vvti and just get a gt4 as I have done.

I was looking at fensport and they sell a turbo there for a 1000 ish claiming high bhp however I am confused because as I understand it if stronger pistons are used the car can get to the 350bhp mark as it is. Am I way off the mark here?

Thank you

[Leeky]

Yes the problem with the standard engine is that 340/350bhp is about the absolute limit. To go higher than this you need forged pistons, as the standard pistons start to melt at 1.2bar boost. You'll also need to get a better turbo as the standard CT26 (Sometimes incorrectly reffered to as a CT20B) runs out of puff at around 340/350bhp as far as i am aware.

So essentially, 350bhp and upwards costs at least £2k in parts, let alone fitting and mapping.

Mine makes 330bhp on the dyno at 1.1bar boost which I've decided i'm more than happy with. It just costs way too much to get this up any higher.

[Jonny0069]

That`s excellent Im honestly looking for 300 - 350 and i`ll be happy with that because I think it will be more than fast enough for daily driving.

What exactly would I need for this and would it be silly to keep it at 350 or would it cope or simply safer to buffer it at say 330bhp.

I have seen custom manifold would this aid the decat and exhaust system that I think I will need?

Thank you again for the help

[Leeky]

The problem with the 350bhp limit on a stock engine is that you are literally on the limit, so if you had a cold day where you over boosted your engine would go pop. There is no safety margin.

320-330 is as high as i would recommend you go on stock internals, just so it stays reliable and safe.

Aftermarket manifolds are honestly a waste of money. The standard manifold is fine.

Easy way to over 300bhp - Cooler grade 7 spark plugs, full service inc filters and all fluids (rad, charge cooler, engine oil, gearbox oil, dif oil, clutch fluid, brake fluid), performance panel filter or induction kit (as long as there is a good cold air supply), decat with a free flowing exhaust (eg Mongoose Full System & Auzzie Downpipe) and lastly a boost controller. Ideally you want an electronic one like a Blitz/HKS/Apexi as those cheap metal bleed valves arent perfect by a long shot.

That'll see you to over 300bhp on a good engine.

[Jonny0069]

Ok excellent thank you 320 - 330 is plenty well untill I can afford the pistons anyway but when your talking 2k and the car off the road it can be a pain really.

That`s what I was thinking with the boost controller but Im not a 100% what I should get it set to as some say 18psi others say the turbo is at it`s limit at 15 psi.

Im hopeing to get is fully serviced soon and I have a Induction kit already so hopefully not far to go now. :-)

[Leeky]

18psi is over 1.2bar - thats piston melting territory.

Im currently running 16.5psi (1.15bar)

[Jonny0069]

Ok excellent so should I stay at 16-17psi max or would you recoment 16-16.5psi I know it`s not much but i don`t want new pistons lol

[Leeky]

The standard ECU's fuel cut comes in at 17psi (which i actually hit today on the way into work as it was a very cold morning) so at 16-16.5 you'll sometimes hit the fuel cut on cold days.

17psi and you'll just hit it all the time which means you need to get an aftermarket ECU or use a fuel cut defender to remove/move the fuel cut - but i wouldnt advise this on a standard engine as its a really good safety feature.

[Jonny0069]

Yer I have been looking into a fuel cut defender but like you say over 17psi and I need pistons anyway so might as well leave it alone untill I have the money to go over 350.

I was thinking is there a minimum psi you have to run the engine to avoid any damage as I had though of geting a 3 stage boost controller and setting the psi to say 2 on one mode as a economy mode in order to gain extra mpg?

Thank you for all your advice it`s much appreaciated

[Leeky]

Sorry i dont know what you mean by a 3 stage boost controller. Do you mean a boost controller that you can just preset a number of different boost levels?

On my HKS EVC EZ when its switched off i get 0.8bar boost (and decent MPG), when its switched on i get 1.15bar. I usually drive with it off and switch it on for when i hit the track.

I've just bought a motorbike as a commuter and wont use the GT4 much anymore, so im actually considering putting my car back to standard and selling my HKS EVC EZ if you are interested. I was thinking about putting it up on eBay or the GT4 owners clubs. Its a complete kit with 100% everything you need.

[aderiley]

I would suggest you keep the fuel cut, the ct20b is fitted to the gen 6 and their are some differences, it is a slighltly better turbo, that said they interchange. there are hardly anyspare parts for these turbos as they are unique to Toyota, I had turbo dynamics make me a hybrid from some ct20b and ct 26 bits and machine to fit a main shaft and other bits, cost £850 and they are really helpfull, you wil also need an uprated actuator, i bought a 12psi one but they also do a 14. the 12 allows me to have this as low boost and with a gfb dual boost raise to 15 when needed. Make sure you get a 2.5 inch down pipe. i have a 3inch and curing the boost creep was a pain. lag the underside of the charge cooler and the filter to turbo pipe (i used reflective radiator insulation from b and q) heat wrap the down pipe before you fit it.

[Jonny0069]

How much would you want for it as Im not really sure how much they are worth being new to the boost controller market lol. And yes that`s what I meants sorry I have seen one that lets you set 3 presets so you could have low boost for everyday to save mpg say a 300bhp setting then a max 340bhp setting that you could use for a bit as to not melt the pistons lol.

Thank you for your advice everyone tell me to leave out the fuel cut defender so I think i`ll go with you and not bother then cheers. Im not sure what acuator I have at present I think it`s standard but Im not sure if the dumpvalve has taken over as I think the small pipe is connected to that.

[Leeky]

I would suggest you keep the fuel cut, the ct20b is fitted to the gen 6 and their are some differences, it is a slighltly better turbo, that said they interchange. there are hardly anyspare parts for these turbos as they are unique to Toyota, I had turbo dynamics make me a hybrid from some ct20b and ct 26 bits and machine to fit a main shaft and other bits, cost £850 and they are really helpfull, you wil also need an uprated actuator, i bought a 12psi one but they also do a 14. the 12 allows me to have this as low boost and with a gfb dual boost raise to 15 when needed. Make sure you get a 2.5 inch down pipe. i have a 3inch and curing the boost creep was a pain. lag the underside of the charge cooler and the filter to turbo pipe (i used reflective radiator insulation from b and q) heat wrap the down pipe before you fit it.

Just thought i'd mention that there is no such turbo as a CT20b, its a fictional name given to the ST205 version of the CT26.

Its mentioned on this site - http://www.madpsi.net/MR2PEKit.htm

• What is the CT20b?

This is the 3SGTE 3rd generation turbo that came with the Celica ST205 and MR2 SW20. There is no casting designation on this turbo that labels the turbo model. The casting on the housing reads "Toyota." Some Toyota literature refers to this turbo as the CT26. This would make it a later generation CT26 than the one that was available in the United States with the 2nd generation 3SGTE. Most people will refer to this turbo as CT20b. This turbo is not a ball bearing turbo. This is not, however, Toyota's official name of the turbo. A Toyota CT20 turbo does exist, but it was used on the 3TGTE, 4TGTE, and 22RTE engines in the 1980’s and will not bolt on the 3SGTE manifolds. Since most people call the turbo the CT20b, we will minimize confusion by also using this model name.

Also you dont need to change the actuator. I have a standard actuator and run 16psi all day long. I've had 3 ST205's now and have never change the standard actuator.

Jonny0069 - The cheapest HKS EVC EZ on eBay is £135 inc postage. You'd also need to buy vacuum pipes, filters and a brass T-Piece. I'll sell you mine for £130(inc postage) including all the pipework and fittings already cut to the correct size for an ST205 so it'll go straight in without any messing around. I've got the unit screwed into the plastic panel under the steering column (was the most convenient location) and i'll even throw in that panel with the holes drilled as i have a spare i can put on my car. Let me know if you are interested.

[aderiley]

I would suggest you keep the fuel cut, the ct20b is fitted to the gen 6 and their are some differences, it is a slighltly better turbo, that said they interchange. there are hardly anyspare parts for these turbos as they are unique to Toyota, I had turbo dynamics make me a hybrid from some ct20b and ct 26 bits and machine to fit a main shaft and other bits, cost £850 and they are really helpfull, you wil also need an uprated actuator, i bought a 12psi one but they also do a 14. the 12 allows me to have this as low boost and with a gfb dual boost raise to 15 when needed. Make sure you get a 2.5 inch down pipe. i have a 3inch and curing the boost creep was a pain. lag the underside of the charge cooler and the filter to turbo pipe (i used reflective radiator insulation from b and q) heat wrap the down pipe before you fit it.

Just thought i'd mention that there is no such turbo as a CT20b, its a fictional name given to the ST205 version of the CT26.

Its mentioned on this site - http://www.madpsi.net/MR2PEKit.htm

• What is the CT20b?

This is the 3SGTE 3rd generation turbo that came with the Celica ST205 and MR2 SW20. There is no casting designation on this turbo that labels the turbo model. The casting on the housing reads "Toyota." Some Toyota literature refers to this turbo as the CT26. This would make it a later generation CT26 than the one that was available in the United States with the 2nd generation 3SGTE. Most people will refer to this turbo as CT20b. This turbo is not a ball bearing turbo. This is not, however, Toyota's official name of the turbo. A Toyota CT20 turbo does exist, but it was used on the 3TGTE, 4TGTE, and 22RTE engines in the 1980’s and will not bolt on the 3SGTE manifolds. Since most people call the turbo the CT20b, we will minimize confusion by also using this model name.

Also you dont need to change the actuator. I have a standard actuator and run 16psi all day long. I've had 3 ST205's now and have never change the standard actuator.

Jonny0069 - The cheapest HKS EVC EZ on eBay is £135 inc postage. You'd also need to buy vacuum pipes, filters and a brass T-Piece. I'll sell you mine for £130(inc postage) including all the pipework and fittings already cut to the correct size for an ST205 so it'll go straight in without any messing around. I've got the unit screwed into the plastic panel under the steering column (was the most convenient location) and i'll even throw in that panel with the holes drilled as i have a spare i can put on my car. Let me know if you are interested.

Hi bit of internet myth that there is no difference between ct26 and ct 20 and there is no casting details , there are various differences between the 2 including the ct26 having a 7 stud fixing, but you can remove a stud to fit the ct20b. the reason to change the actuator (8psi on ct20b standard) is to stop bleed off which means the wastegate starts to open from 8psi instead of 12 which makes a cleaner boost. i have attached specs for the different turbos

Turbo Comp. Inducer Comp. Exducer Turbine Minor Turbine Major

3SGTE CT26 1.574" 2.559" 1.97" 2.36"

Supra CT26 1.75" 2.559"?? 1.97" 2.36"

3SGTE CT20B 1.88" ??? 2.05"

T3 - 45Trim 1.595" 2.367"

T3 - Super 60 1.90" 2.367

Mitsubishi 16g 1.83" 2.37"

Mitsubishi 20g 2.07" 2.68"

TO4B V Trim 2.18" 2.75"

TO4E 46Trim 2.00" 2.95"

TO4E 50Trim 2.12" 3.00"

TO4E 54Trim 2.17" 2.95"

TO4E 57Trim 2.23" 2.95"

Greddy TD06SH-20G 2.071" 2.677" 2.177" 2.559"

Greddy TD06L2-20G 2.071" 2.677" 2.126" 2.401"

Greddy T67-25G 2.381" 3.070 2.130" 2.402"

KKK K26

T3 Turbine - - 1.898" 2.319"

T3 Stage 2 Turbine - - 2.122" 2.559"

T3 Stage 3 Turbine - - 2.229" 2.559"

T4 N Trim - - 2.071" 2.922"

T4 O Trim - - 2.296" 2.922"

T4 P Trim - - 2.544" 2.922"

T4 Q Trim - - 2.693" 3.111"

[Leeky]

Thats a very handy list. Many thanks for that. But still, there is no such turbo as a CT20B im afraid.

You need to re-read what i said. I didnt say there are no differences. There are a dozen different versions of the CT26 but if you ask Toyota for a CT20B they will tell you the same - it doesnt exist. The CT20B name is one that the tuning community gave to the ST205 version of the CT26.

The Toyota EPC parts system says that the ST205 turbo is a CT26 and also the Toyota workshop manuals say its a CT26.

[Red123]

What's your recommendation about spark plugs if I want 300bhp+?

[Leeky]

NGK Iridium Heat Grade 7

[Red123]

Hello Leeky.

What if I install grade 7 spark plugs in the stock ST205?

Any downsides?

p.s.Is it original?

http://cgi.ebay.co.uk/NGK-IRIDIUM-SPARK-PLUGS-FIT-TOYOTA-CELICA-GT4-ST205-185_W0QQitemZ370260726125QQihZ024QQcategoryZ122139QQssPageNameZWDVWQQrdZ1QQcmdZViewItem

Thanks

[Leeky]

Heat Grade 7 sparks will be ok in a stock ST205 but if you plan to leave it stock you may as well get the cheaper Heat Grade 6.

Heat Grade 7 will be good for a stock engine running higher boost.

[Red123]

On how much boost can I get 300bhp?

[Leeky]

My first GT4 made 308bhp at 1bar.

It had a straight through unrestrictive exhaust (Auzzie downpipe, flexipipe and Blitz NurSpecR Exhaust) and a good unrestrictive intake (HKS Superflow). I also had a Link Piggyback ECU.

[Red123]

Thanks.

Seems like I need only to gut the cat and downpipe.

Any info how to cat back on ST205?

Leeky, what do you think is it possible to reach 300+ bhp on a stock ECU?

[Leeky]

Downpipe replaces the cat, so youd fit a downpipe or gut the cat.

Yes you can easily get over 300bhp on the stock ecu with the right amount of boost.

[Red123]

So If I install downpipe, it's not necessary to gut the cat?

Great.

What would you recommend me 3 Aussie downpipe or 2.5?

[Leeky]

Auzzie only done one size downpipe.