Author Topic: Stage 2 turbo technics turbo  (Read 7877 times)

DIZZY DAZZLER

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Stage 2 turbo technics turbo
« on: 00:43, Tue 10 July 2012 »
Hi folks I am new to this forum and im seeking a little advice.

I have a renault 5 turbo and to cut a long story short it was running a turbo technics stage 3 turbo and on the rollers it made 210 at the wheels, the problem was it was way too laggy round town. Because of the lag I decided to downsize it to the smaller stage 2 turbo that has a t25 compressor and t2 turbine houding etc. Whilst the turbo comes onto boost far faster it feels like i have lost too much power and i am thinking of going back to the stage 3.

What do you think I should do as I was expecting the stage 2 to spin up to boost really fast but I find that it struggles to build more boost after say 17psi and I have tried everything, checked for boost leaks, altered the wastegate etc etc I have even pulled the wastegate pipe off to see if the turbo will cary on boosting but it appears to struggle ( the engine is built to take big boost so i wasnt worried) is it a case that i have a dodgy turbo as its near new with only around 200 miles on it from turbo technics or is this the nature od the smaller t2 exhaust housing.

Also I recently set the mixture to 3.5 at around 1200rpm. What should it be set at to ensure there is plenty of idle fuel to get the turbo spinning?

Sorry for all the questions but I am unsure of what to do.

markey mark (bd)

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Re: Stage 2 turbo technics turbo
« Reply #1 on: 17:21, Tue 10 July 2012 »
What spec are the stage 3 and stage 2 turbo's mate? To be honest the 'stage' name doesn't tell most people about spec and size of the turbo and this will help in to know what the turbo will react like and be capable of.

If the smaller turbo is struggling to make more than 17psi it might be fact that its working past its effective efficentcy so working it harder won't get you any more power.
Whats the spec of your engine mate? If the larger turbo was abit laggy there might be ways to help make it less laggy depending on whats been done to your engine or what you could do to it to help out.
If you got any pics of the turbo might be worth putting them on here if you not sure what specs they are, will help determine what you got

As for idle, ideally you want it about 2.5-3% at around 850-1000rpm. Remember the mixture screw only fuels for idle nothing else, when the turbo comes in or your driving the fuel is delivered from a different part of the carb. Do you know what your carb spec is if you have had anything done to it?
BD Autosport - Renault 5 gt turbo tuning and repairs.

DIZZY DAZZLER

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Re: Stage 2 turbo technics turbo
« Reply #2 on: 18:52, Tue 10 July 2012 »
Hi there, many thanks for coming back so soon. To start with my engine spec is as follows:

Standard pistons and liners 7.9:1 com ratio
Ported and polished head with matched inlet
GT tuning stage 2 cam
Ktec tubular manifold (original first model that cracks)
large bore turbo elbow
GT tuning 2.5" down pipe and 2.5" cybersport exhaust
Group A carb with .9 air corrector and I think 1.3 main jet
GT tuning air filter with ram pipe
The usual copper rad and lobster back etc
GT tuning double capacity intercooler

The original turbo was a full t25 hybrid
http://www.turbotechnics.com/turbo/s157.htm

This turbo was laggy but the guy who dynod it upped the mixture to get it going which resulted in the car smelling of fumes on a long journey etc however when it came in it moved well.

Because of the lag i fitted the smaller t25/t2 which I think has a compressor ar of .63 and turbine .60 i believe http://www.turbotechnics.com/turbo/s117.htm.

now i feel like the turbo is either not right or its the reduction in turbine housing thats holding it back.

Tonight i may check the fuel pump is delivering enough pressure but i feel like i am grasping at straws and would appreciate any help you can give.

markey mark (bd)

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Re: Stage 2 turbo technics turbo
« Reply #3 on: 21:06, Tue 10 July 2012 »
Firstly you need to change that carb mate, that'll be one part of the problem as i recon its leaning out due to the way they are poorly set up

I don't think either of those turbos are too big, when was you getting full boost on the larger one? Also when you wanting full boost by?
BD Autosport - Renault 5 gt turbo tuning and repairs.

DIZZY DAZZLER

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Re: Stage 2 turbo technics turbo
« Reply #4 on: 21:52, Tue 10 July 2012 »
I am unsure of what to do now. Is it worth rebuilding the standard 25mm venturi carb, with .9 air corrector jet, redrilling the 2nd stage to 1.1mm and refitting the 1.2mm main jet.

I have just been for  a spin in the car and the t2/t25 didnt come on until full boost until around 4500 rpm.  Is this normal as the full t25 didnt come onto fulll boost until about 5000rpm.

Will the 25mm venturi carb still flow enough for big power 200+.

markey mark (bd)

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Re: Stage 2 turbo technics turbo
« Reply #5 on: 15:24, Wed 11 July 2012 »
Quote from: "DIZZY DAZZLER"
I am unsure of what to do now. Is it worth rebuilding the standard 25mm venturi carb, with .9 air corrector jet, redrilling the 2nd stage to 1.1mm and refitting the 1.2mm main jet.

I have just been for  a spin in the car and the t2/t25 didnt come on until full boost until around 4500 rpm.  Is this normal as the full t25 didnt come onto fulll boost until about 5000rpm.

Will the 25mm venturi carb still flow enough for big power 200+.

I would rebuild the carb with a standard venturi, standard main jet and mod the enrichment circuit to fuel it more on boost.
Yeah the standard venturi will flow well over 200bhp mate, i've done 230-240bhp before at 24psi on my old engines and it still ran slightly rich after the mods i done to the carb.

I would of expected the T2/T25 to come in earlier than that, you may have a fault somewhere else causing it to come in abit late.
BD Autosport - Renault 5 gt turbo tuning and repairs.

DIZZY DAZZLER

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Re: Stage 2 turbo technics turbo
« Reply #6 on: 18:29, Wed 11 July 2012 »
Ok my plan will be to mod the standard venturi carb. what do you suggest as a start. Assuming a bog standard cab, should I fit the 0.9 air corrector jet, 1.2mm main jet and drill the second stage fixed jet to 1.1mm with a plan to running around 19psi. Is there anything else I need to do as i understand there in another jet in the section of carb that bolts to the passenger side of the carb, does this stay untouched.

From memory when I had it on the rollers the guy dynoing it ended up filing the idle mixture screw to get more fuel in to get the previous t25 going. I assume he should really have concentrated on the second stage fixed jet? as I am sure on tickover it was like 9% on the CO.

What do you think.

markey mark (bd)

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Re: Stage 2 turbo technics turbo
« Reply #7 on: 18:59, Wed 11 July 2012 »
Quote from: "DIZZY DAZZLER"
Ok my plan will be to mod the standard venturi carb. what do you suggest as a start. Assuming a bog standard cab, should I fit the 0.9 air corrector jet, 1.2mm main jet and drill the second stage fixed jet to 1.1mm with a plan to running around 19psi. Is there anything else I need to do as i understand there in another jet in the section of carb that bolts to the passenger side of the carb, does this stay untouched.

From memory when I had it on the rollers the guy dynoing it ended up filing the idle mixture screw to get more fuel in to get the previous t25 going. I assume he should really have concentrated on the second stage fixed jet? as I am sure on tickover it was like 9% on the CO.

What do you think.

Filing the idle mixture screw!  :?   Sounds like person who played with carb hasn't got much clue as to how these carbs work. 9% at idle on the CO, thats way too rich that'll be donw to large main jet and poor mixture set up
To start with you want a carb body with a standard 25mm venturi, then fit the standard 1.2mm main jet. To know what you need to do to the carb you ideally need to see what the AFR's are doing at the boost you want. If you going for the full T25 at 19psi then i would say around 1.2mm on the second stage and then 1-0.9mm on the ac but that'll depend on what the AFR's say. The 1st stage can stay 1mm as standard.

This is only a guide mate so might work as a base but need to see how it fuels driving it right through rev range to see if its sorted it
BD Autosport - Renault 5 gt turbo tuning and repairs.

Ash-Lee

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Re: Stage 2 turbo technics turbo
« Reply #8 on: 19:17, Wed 11 July 2012 »
For reference.

I run a T25 @ 22PSI. (GT Tunings Stage 5 HE5B) It reaches maximum boost pressure around 3.5kRPM.

This is with a standard cam, head etc. Carb had standard venturi, 1.2 main jet, 0.9 A/C, 1.3 2nd stage and it still runs a little on the rich side (high 11 AFR)

How did it ever pass an MOT with a mixture like that?  :shock:

You can't go far wrong with listening to the above advice.

DIZZY DAZZLER

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Re: Stage 2 turbo technics turbo
« Reply #9 on: 22:10, Wed 11 July 2012 »
Ah thanks for the advice chaps. Can I ask so may of you dislike the group A carb, is it because it messes up the fuelling or because the standard 25mm venturi is best suited to the remains of the carb design.

By the way what is the size of the standard second stage jet also how do you manage to drill them so precise given the tenth of a millemeter makes so much difference. Also so you are aware i took the car out today and in fourth gear i floored it at 3000rpm and the turbo didnt do a lot and by 3500rpm thstandard boost gauge was in the middle which is about 7psi I think. Surely this is not right, I am thinking of sending the turbo back to turbo technics for testing as it should boost a lot faster than it does.

markey mark (bd)

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Re: Stage 2 turbo technics turbo
« Reply #10 on: 21:38, Thu 12 July 2012 »
The standard venturi works alot better than the larger one due to the design of the carb, the way tunuers use to jet the grp A carbs too also caused alot of probs as it caused the car to over fuel on idle and low revs but lean out high up the revs

To be honest mate i wouldn't be reving/driving it hard if the carbs not right, you could cause damage to the engine

I doubt the turbo is at fault, i recon there might be some other factors causing it. Do you know how much preload is on the actuator?
BD Autosport - Renault 5 gt turbo tuning and repairs.

DIZZY DAZZLER

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Re: Stage 2 turbo technics turbo
« Reply #11 on: 07:14, Fri 13 July 2012 »
I have adjusted to actuator to boost to a max of 15psi as i then use an in car to bleed a further 3>4 psi off. I am going to do as you said and rebuild the standard car and if it instantly feels better i am going to fit an aem afr kit to tune it as best i can. I thing as a start i will fit the 0.9 ac, drill 2nd stage to 1.1mm and fit the 1.2mm main jet.

I assume this should get me started to tune further.

Regards

markey mark (bd)

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Re: Stage 2 turbo technics turbo
« Reply #12 on: 22:17, Fri 13 July 2012 »
Why not set boost on the actuator and leave it mate? Use an under bonnet bleed valve if needs be to get the eaxtra if you need it to get up to 19psi
I would remove the in-car controller
BD Autosport - Renault 5 gt turbo tuning and repairs.

DIZZY DAZZLER

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Re: Stage 2 turbo technics turbo
« Reply #13 on: 08:58, Sat 14 July 2012 »
I could do that however i was concerned that it would be too much sring pressure pilling on the wastegate arm.

I have srtipped both the froup a carb ans standard carb with a plan to ovehaul and build the standard carb. I will keep you posted. If the car feels better i will get myslef an aem afr kit and tweak it further.

I am still thinking that the turbo is at fault as i clamped the pressure feed to the actuator and put my foor down expecting the turbo to keep boosting and boosting until distruction, however it didnt go much more than 22 psi so its either the turbo or fuel and pump pressure related.

markey mark (bd)

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Re: Stage 2 turbo technics turbo
« Reply #14 on: 20:48, Wed 18 July 2012 »
Quote from: "DIZZY DAZZLER"
I could do that however i was concerned that it would be too much sring pressure pilling on the wastegate arm.

I have srtipped both the froup a carb ans standard carb with a plan to ovehaul and build the standard carb. I will keep you posted. If the car feels better i will get myslef an aem afr kit and tweak it further.

I am still thinking that the turbo is at fault as i clamped the pressure feed to the actuator and put my foor down expecting the turbo to keep boosting and boosting until distruction, however it didnt go much more than 22 psi so its either the turbo or fuel and pump pressure related.

If you clamped vacumn pipe to actuator and it still didn't boost all way then sounds ike actuator fault to me not turbo. Will have nothing to do with fuel pump

Yeah let me know how you get on with carb
BD Autosport - Renault 5 gt turbo tuning and repairs.