Power - What route to go now??

[Big Supes]

New poster! (less than 10 posts)

Hi guys, looking to order up the parts for my new engine build, but wanted to rack the brains of the guru's before I do.

Here's my current set up:

KTR - Level 3 gas flowed head.
Uprated head gasket set and bolts.
KTR uprated cam.
Group N Clutch.
Lightened Flywheel.
KTR alloy intercooler, group A carb, group A dump valve, induction kit, in-car boost kit.
Hi output starter motor.
Samco hoses
Garrett T2 Turbo
Scorpion Exhaust

The car was running 20psi all the time and never gave me any issues. The main reason for the rebuild is to refresh the bottom-end.... and here's my question........

Would it be ok to fit forged pistons, but not the forged con-rods and steel liners to run 25+ psi?? I know this sounds a bit 'bodge', but there's a massive price difference and TBH, I only want to run a bit more power than what it was before.

Any help would be appreciated.

[Maka]

from what ive read many times over

standard piston and liners
standard carb (not a group A)
decent intecooler
T25 or T28 turbo
an Lm-1 afr gauge of some sort
and someone who can help you drill your carb jets to suit 20psi.

should make all the difference if your already running a decent Cam.

my word isnt gospel just what ive read a few times

[Big Supes]

New poster! (less than 10 posts)

I think I remember reading that the standard pistons and rings won't cope with going over 20psi.

[TrixNFlix]

from what ive read many times over

standard piston and liners
standard carb (not a group A)
decent intecooler
T25 or T28 turbo
an Lm-1 afr gauge of some sort
and someone who can help you drill your carb jets to suit 20psi.

should make all the difference if your already running a decent Cam.

my word isnt gospel just what ive read a few times

[Rob@Backyardracing]

Firstly a T2 is a tiny turbo IMO and would be dead at 25psi... thats up to you and what you want the car for.. Also stock cast pistons are fine to high levels of boost (even 500Wheel!!!!hp+ in other cars) depending on tapper and piston to wall clearances (machine your own maybe)... I havnt messured stock GT pistons over a forge so i cant say there..

[Maka]

New poster! (less than 10 posts)

I think I remember reading that the standard pistons and rings won't cope with going over 20psi.

not sure, but i do believe some of the quicker cars on the 1/4mile may have run on standard pistons/liners. up to 23psi i think.

id be more worried about fueling for 25 psi in 4th and 5th than your pistons at present.

[Big Supes]

New poster! (less than 10 posts)

Firstly a T2 is a tiny turbo IMO and would be dead at 25psi... thats up to you and what you want the car for.. Also stock cast pistons are fine to high levels of boost (even 500Wheel!!!!hp+ in other cars) depending on tapper and piston to wall clearances (machine your own maybe)... I havnt messured stock GT pistons over a forge so i cant say there..

Yeah, there's other ancillaries I'd replace to go over 20 psi... I was just referring to the internals.

That's f'in awesome news regarding the standard pistons! With the money I could save, I wonder if a machine shop could sort the piston to wall clearances.....

I know the forge pistons lower the compression.

not sure, but i do believe some of the quicker cars on the 1/4mile may have run on standard pistons/liners. up to 23psi i think.

id be more worried about fueling for 25 psi in 4th and 5th than your pistons at present.

Yeah, fueling and cooling (boost) are my two main concerns. Thinking about trading in my uprated cam for K-tecs 285 cam and uprated valve springs.

Does anyone know if the standard fuel pump is up to the job of big boost??

[Rob@Backyardracing]

I think you should use your old pistons with new liners and rings, if your planning a rebuild its what i do. Maybe machine the crown off only depending on what your head hight messures at (if its been skimmed alot before) and what your plan is for the engine... Piper 285 and T28 seems a proven winner for good power. Spend your cash on set ups and good charge cooling.. The Ph1 GT fuel pump will work ok, check to see what you have fitted allready??? black rubber casing over pump then bin it... it wont be uprated

[Big Supes]

Cool.... sounds like a good plan.

When replacing the liners, would you recommend going for the steel liners that K-tec supply or just go for standard replacements?

K-tec's T28's are insanely expensive. Do you know of any other reputable tubbys that people use?

[Rob@Backyardracing]

Poss Adam L on here for a turbo is best bet i get alot of my parts from US these days or ATP so cant say... Standard liners will do fine... All in set up and balance of parts...

[Big Supes]

Sh!t.... and there was me grumbling that I had to pay £25 to join this club, but in hindsight it has saved me over a grand already! Cheers!

Will possibly get in touch with Adam regarding the turbo. Think it could be wise to get the crank lightened/balanced/knife edged while it's all out.

[Rob@Backyardracing]

Lol Nope no real point in that either... GTs are cheap as chips to tune and rebuild and the ££££ - BHP its cheap.... If your after a rebuild just do a stock rebuild with new rings and shells, gaskets etc full check over... Poss cam swap + springs and turbo then spend time and cash on getting it set up.. THIS IS the main reason why so many fail. Peeps dont have them set up correctly etc..

[Big Supes]

Sweet! I'm going to sleep tonight with a big grin on my face.

Totally agree about peeps not getting them setup right. I always took mine to K-tec to get it done and it never gave me any issues at all, despite people constantly telling me it would go pop "because it a GTT".

[Markey Mark (BD)]

Sweet! I'm going to sleep tonight with a big grin on my face.

Totally agree about peeps not getting them setup right. I always took mine to K-tec to get it done and it never gave me any issues at all, despite people constantly telling me it would go pop "because it a GTT".

Honestly mate tune the carb yourself or have some help from here, the carbs from 'tuners' have been known to never fuel correctly, you'll gain abit more just from that itself.

[Big Supes]

I may get the whole thing tuned on a RR and have a look it then. Will definitely consult you guys before hand though.

[Penfold aka The Dealer]

Make sure you go to a decent RR, there maybe some members on here who can recommend a place to go...

The club is full of people who have been tuning there cars for years and do a better job than the tuners...

[Big Supes]

Sweet. Once it's up and running I'll maybe looking into meeting up or something with some of the guru's on here to get it dialed in. Either that or just take some advice while trying to do it myself.

[rs250nut]

Ah sweet as another member on the south coast, if you need a hand with anything give us a shout.

[Big Supes]

Awesome, mate. Cheers.

May take you up that.

[Tiny Tim]

I'll stand by and drink the beer.

[Big Supes]

I like your style.

[Maka]

what i found form experience is big tuner names drop big main jets in and alter the air corrector.

bout as far as they go. therefore over fueling during normal driving and under fueling on full boost.

ditch the group A carb and read this article steve did: https://www.rtoc.org/boards/showthread.php?t=460


works a treat

[markey b]

mine has dished std pistons, std liners and std rods, runs up to 27psi manifold... got a MSM high comp engine but std parts

[Big Supes]

what i found form experience is big tuner names drop big main jets in and alter the air corrector.

bout as far as they go. therefore over fueling during normal driving and under fueling on full boost.

ditch the group A carb and read this article steve did: https://www.rtoc.org/boards/showthread.php?t=460


works a treat

Just subscribed to that thread for future reference. My car definitely felt as if it was over fueling during normal driving.

mine has dished std pistons, std liners and std rods, runs up to 27psi manifold...

Nice.... what turbo are you running? Any idea how many horses you're putting out?

got a MSM high comp engine but std parts

what does that involve?

Cheers

[Mart]

o.e piston ringlands won't like prolonged use over 1.5bar (*), so if you're planning on running more than that, go forged (J.E is my recommendation).

o.e liners will take a fair bit more boost than that, but again there are forged (and graphite) liners available if needs be. In my experience though, they're not needed.

The bottom-end is pretty much bullet-proof, so the o.e rods will be fine for whatever you chuck at them, and likewise for the crank & its bearings/shells as well.

* And if that is the case, you'll need to look at improving fuel supply (float chamber) too.

[markey b]

Nice.... what turbo are you running? Any idea how many horses you're putting out?

runs a VNT, dyno figures are 217bhp 256.4lb/ft torque but dyno figures are just that, and i'm sure need to be taken with pinch of salt. did a 105terminal at pod on road tyres so is probably around that figure somewhere.

as for the high comp engine, i think markeymark knows a bit about them, but last i heard there is easier ways of tuning the c1j

[Big Supes]

o.e piston ringlands won't like prolonged use over 1.5bar (*), so if you're planning on running more than that, go forged (J.E is my recommendation).

o.e liners will take a fair bit more boost than that, but again there are forged (and graphite) liners available if needs be. In my experience though, they're not needed.

The bottom-end is pretty much bullet-proof, so the o.e rods will be fine for whatever you chuck at them, and likewise for the crank & its bearings/shells as well.

* And if that is the case, you'll need to look at improving fuel supply (float chamber) too.

Ideally, I'd like to go 30psi.... would you recommend maybe just go for the forge pistons then? I was under the impression that the standard ones would be fine if I had the crowns machined down.

[Mart]

Compression ratio wise, it'll help at 30psi, but the ringlands won't be upto the job. Give it a trackday or several runs at the Pod, and they'll crack quicker than humpty dumpty falling off a wall.

30psi will take some trick fuelling/carb jetting.

Aim for a power figure rather than a max boost figure...

[Big Supes]

runs a VNT, dyno figures are 217bhp 256.4lb/ft torque but dyno figures are just that, and i'm sure need to be taken with pinch of salt. did a 105terminal at pod on road tyres so is probably around that figure somewhere.

as for the high comp engine, i think markeymark knows a bit about them, but last i heard there is easier ways of tuning the c1j

Yeah, dyno's can be a bit hit and miss, but even so, that's quite a good torque reading.

[Big Supes]

Compression ratio wise, it'll help at 30psi, but the ringlands won't be upto the job. Give it a trackday or several runs at the Pod, and they'll crack quicker than humpty dumpty falling off a wall.

Noted.

Forgies will have to be ordered in that case.

30psi will take some trick fuelling/carb jetting.

Aim for a power figure rather than a max boost figure...

It's a bit of a bugger as I never got a power reading as the car is now @ 20psi. All I know is that not a lot of cars could keep up with it off the lights. When I say I'd like 30 psi, I'm just estimating a 30% power increase.

[Mart]

And old c1j rule of thumb, in most cases anyway - For every psi of boost you increase, you'll gain ~5hp.

[Maka]

Noted.

Forgies will have to be ordered in that case.



It's a bit of a bugger as I never got a power reading as the car is now @ 20psi. All I know is that not a lot of cars could keep up with it off the lights. When I say I'd like 30 psi, I'm just estimating a 30% power increase.

will the geabox take a prolonged use of 30psi? even if you crack the fueling for the carb!!

[Big Supes]

And old c1j rule of thumb, in most cases anyway - For every psi of boost you increase, you'll gain ~5hp.

Ahh, quite a handy one to know (as a gauge).

will the geabox take a prolonged use of 30psi? even if you crack the fueling for the carb!!

Not sure, tbh.

Someone once told me that the gearbox off the diesal 1.7 (I think) R5 is a good option. Apparently it gives a higher top end and is more durable...

[Maka]

Ahh, quite a handy one to know (as a gauge).



Not sure, tbh.

Someone once told me that the gearbox off the diesal 1.7 (I think) R5 is a good option. Apparently it gives a higher top end and is more durable...

over 80mph my doors try to open themselves and i swear i can hear the front wings creaking!

not sure personally with my car id want to be aiming for a high topend

[Matt Cole]

over 80mph my doors try to open themselves and i swear i can hear the front wings creaking!

not sure personally with my car id want to be aiming for a high topend

I think there is something wrong with your car mate if it does all of that at 80!! 140mph and i would agree with you.

[Big Supes]

over 80mph my doors try to open themselves and i swear i can hear the front wings creaking!

not sure personally with my car id want to be aiming for a high topend

Yeah, I agree with Matt that something is up with your car.

It's not so much that I want to go faster.... having a high gear ratio would bring the revs down while motorway cruising.

[jesus in the seat of a 5]

Yeah, I agree with Matt that something is up with your car.

It's not so much that I want to go faster.... having a high gear ratio would bring the revs down while motorway cruising.

..sounds like a lie..., standard boost rules..., you can keep your monthly rebuilds and eternal quests for reliability......, seriously though, 25-30psi..id reccomend you give these guys a call ... http://www.theaa.com/search-index.js...oogleBrand...:)

[Maka]

I think there is something wrong with your car mate if it does all of that at 80!! 140mph and i would agree with you.

you can definatly see day light through the top of the door when accellerating at full pelt over 80mph
and no not through the window.

my cars beautiful, nothing wrong with that!

[Rob@Backyardracing]

also worth noting, 20psi on a t2 is no comparison to 20psi on a t28.

a bigger turbo (t28 or so) at the same boost as your running now will yield
far more power, so again, dont aim for a max boost figure, aim for a target hp.

i`d suggest going out in a gtt with a t28 fitted before you spend any money
and decide if you like the power/delivery.

as for forged vs cast pistons, maybe just luck, but i had a set of wossner forged pistons in my gtt, and they took far less abuse to detroy than old stock cast jobbies,
in fact they lasted a full week, and was £500

[Brigsy]

you can definatly see day light through the top of the door when accellerating at full pelt over 80mph
and no not through the window.

my cars beautiful, nothing wrong with that!

If you have flappy doors get the doorpins done

[Big Supes]

..sounds like a lie..., standard boost rules..., you can keep your monthly rebuilds and eternal quests for reliability......, seriously though, 25-30psi..id reccomend you give these guys a call ... http://www.theaa.com/search-index.js...oogleBrand...:)

PMSL

Jesus, you speak wise words, but taking the sensible option has never been a strong point of mine. If it was, I'd keep my Nissan Micra and sell the 5.

My GTT has run 20 psi for around 2 and half years with no serious problems. I think the only thing that kept letting go was clutch cables..... still need to do the soft pedal mod.

There's no doubt that I won't go for big power if it means it could break any second.

also worth noting, 20psi on a t2 is no comparison to 20psi on a t28.

a bigger turbo (t28 or so) at the same boost as your running now will yield
far more power, so again, dont aim for a max boost figure, aim for a target hp.

i`d suggest going out in a gtt with a t28 fitted before you spend any money
and decide if you like the power/delivery.

Good point.

Taking on board your point, I think I'll still be going T28; even though the GTT is great fun @ 20 psi with a T2, I'd still like more power. If it turns out that 20 psi delivered from a T28 will do the job, it'll be a bonus as the engine will be capable of more (won't be pushed to the limit).

as for forged vs cast pistons, maybe just luck, but i had a set of wossner forged pistons in my gtt, and they took far less abuse to detroy than old stock cast jobbies,
in fact they lasted a full week, and was £500

Sh!t!! Sounds like bad luck to me.

[Maka]

If you have flappy doors get the doorpins done

its on the list of things to do.

thanks fella

[Big Supes]

Just bought a ported and polished inlet manifold.... they seller claims it gives an extra 15bhp, but I can't really see it....

[Mart]

Port matching the manifolds is a worthwhile mod, but polishing, boring out, etc is a waste of time - The roughness inside the inlet manifold is good for fuel/air atomisation, and no need to enlarge the runners/headers as the carb venturi will still be the pre-engine restricition.

Likewise for the exhaust manifold, in that you want to retain the same diameter/bore all the way through to maintain gas speed/heat/pressure (cue Boyle's Law) to aid turbo spool.

As for the 15hp gain...

[Big Supes]

Oh well..... it's shiney which is always a plus.

I've always wanted to get the KTR exhaust mani, but it's insanely expensive!

[Maka]

i think theres been quite a bit of discussion on the tubular manifold option.
i believe its not really of huge benefit plus you loose the tractor sound!

[Big Supes]

All joking aside, losing the tractor sound would actually stop me from getting it.

[5alldaway]

theres nothing like the good old tractor, the gtt is always so distinctive, theres a local 5 that comes past my house sometimes and i always know its him when im tucked up in bed

http://www.youtube.com/watch?v=WhzeBeqlNJc

[Big Supes]

You can't beat the signature sound of a 5.

[Andrew Cooke]

http://www.youtube.com/watch?v=WhzeBeqlNJc

ooh, tuning on the workshop dyno