What would you do? opinions please?

Right, if any of you read my post in the future plans thread then you will no i have recently purchased a Garrett T2/T28 Hybrid turbo to replace my vw/audi GT15 turbo,but ive been doing alot of thinking, here is my problem -

my car currently runs 125bhp @ 5800 rpm right through to 6666rpm and 135lb/sf of torque @3800rpm with 1 bar of boost (14.7psi), but at this boost pressure level the turbo is maxed out and is therfore heating up the air going into the engine which means it cannot give me the gains i want! the compressor can flow more air (around 140bhp max which is around 14lb/min) but not at this boost pressure - now this is down to my engine spec because my compression ratio is to low and by using 2 head gaskets and a decomp plate its messing up to fuel squash making the engine very unefficient, if the engine were set up with the pistons and rods im getting soon from the 16v punto i could do away with the decomp plate and extra gasket and have a better C/R making the engine perform better for the given boost, i bet with that set up i could make my 130 bhp @ as low as 0.85bar of boost giving room for better increases @ 1 bar.
Thing is ive been thinking about how the car drives at the moment and i really love it, because the turbo is small it spools upto a bar very fast and harsh making drivshafts and tyres frequant! but it means the pull from low down is emence for the torque level giving an instant neck snap at 3000rpm as you plant the pedal, and it will spool upto 0.8-0.9 bar @ half throttle meaning it is very drivable, i can overtake up hill in fourth at half throttle comfatably but setting of fast in first and second requirs some concentration.

So i have bought the t2/t28 hybrid to cure the low power/boost ratio problem,,,,,,,,,,,,,,,,,,this will dramatically effect the torque curve that i love so much, making the car very undrivable with no low end torque - mid range will be reduced too but the power and torque high up in the revs would be huge, around 150-170 bhp at a low boost level with torque being as high as 190lb/sf @ say 4500rpm. Using the hybrid it would also make the car more controlable and quicker to 60 because the spool up is less harsh and builds up slower so the torque spikes dont brake shafts and grip as easy, but overtaking would mean working the gears and revs more. At my current set up over taking in 3rd is very quick, it will pull from 3000rpm in 3rd from 30-60 in 4.5 seconds and im into fourth at 70mph (usually just changing as i level out with someones window hehe) so its effortless and torque through the revs like a diesel engine.

My idea to get what i want -

I could keep my flat torque curve and drivability by turning my turbo into a hybrid by fitting the compressor housing and wheel from a GT18 turbo. By doing this i estimate a power level (with engine sorted) of around 140bhp @ 0.8-1 bar boost with torque being as high as 150-160lb/sf, yes this would increase the chance of snapping more drivshaft but it would mean the the car would behave the way it does now but much quicker with lightning responce and huge pull for lightning overtaking rivaling some big powered cars.

So what would you do if it were your car -

1. Fit Hybrid T2/T28, sort engine, have a powerful 150-170 bhp car with huge straight line top end pull (motorways etc), more control due to a less harsh spool up, loose low end torque and mid range torque will be reduced, possabliy quicker upto 60.room for big poer -(this set up is capable of upto 250plus bhp)

OR -

2. Hybrid my current T15 with a GT18, sort engine, have around 140bhp with huge mid range and low end pull, fantastic drivability, Quick responce, more chance of snapping driveshafts and shreading tyres, loose out on much higher bhp outputs (max flow off this set up would be around 160bhp-170bhp), make full throttle launches more of a handful.This makes a very fast road car.

opinions please, it where you?????????????????????? 1 or 2?

both ideas sound a lot of fun to be honest mate, but at the end of the day its your daily car which most project cars arent, so you really need the driveability... or another car, with the lengths your going to go on this car maybe you could look into some sort of custom/modified driveshafts and possibly hubs that would accept a cv joint with a chunkier spline, how easy that is though might be a different story, it could be as easy as modifying something from a bigger or newer fiat, how do people go about it when they put in 4wd or an engine in the rear of a car that was never designed that way, surely its custom and do-able

its all a case of time and deep pockets, its harsh but 99% of the time worth it

in my opinion option 1, just because as said its your car to drive every day mate. i think option 1 offers more for your time, effort and money put in. 160-170bhp dont sound too bad to me. and although you will miss the savage acceleration as i would, i honestly think you would be better with the new hybrid turbo offering more power up top! but at the end of the day mate its up to you so i guess do what you want, this is just my opinion.

Thanks for the opinions guys, id hoped more people would have had a say but hey haha.

ricky - there are companys out there that build up custom reinforced shafts but there about 300 quid a piece so i have to stick to standard.

BUT i have made a decission, i spent a while on the phone with andy from Midland Turbos yesterday about the route i can go down and after exsplaining that i wanted to keep the torque characturistics i have, ive come to a desission of turning my turbo into a hybrid, using the GT17 DCI compressor wheel and housing mated to my turbo after a rebuild, this will give me room for improvement well within what im after.
I have made the desission to aim for 145bhp max although after the engine is done with the GT15/17 hybrid it will do more, the reason is because that is probably the limit before i spoil what is a good fast road car, whats the point in having 170bhp if im spinning the wheels all the time and causing bad handling etc (its much to light to have that power to the front wheels), 145bhp is enough to out accelerate some very serious stuff and it will enable me to get the full 132mph out of the car with ease and the mid range acceleration on the low gearing will be very very quick. Leaving me with room to improve if i fancy trying to up the boost some time in the future. The 0-60 will not be any quicker due to the fact that 7 seconds is roundabout the limit for a cinquecento on the standard box and front wheel drive setup but acceleration in the mid range is likley to be as fast as cars with 300bhp or more based on 3 150bhp cinqs on the fiat forum who visit santa pod regular (vids on youtube against a 200sx,subaru and a crx turbo)
So there we go thats what im going to do, its 185 plus vat for a rebuild on the turbo and 60 plus vat to hybrid it -

The other big thing i have decided to do after the turbo is fitted and the engine sorted with new management is to get more fuel into the engine without going to the torque robbing MPI setup, to do this im going to have my throttle BOB modified to house another 803 green cosworth injector along side my Vanaaken second injector, (side by side both firing down the side of the O.E injector) i can pipe these 2 injecotors of off the high pressure fuel line and it means will have the fueling capability of adding another 85 bhp's worth of fuel onto my setup, This also means i can now choose to either just control the ignition timing or fit the full greddy e-manage setup!

jason

Good decision to stay away from the larger turbo, Knowing what my spool time and boost was on a T28 on the little engine in yours this would be horrific
You wouldn't start to see boost till about 4k at a guess then not hitting full boost till after 5k meaning you would only see full boost for a very short time. Also off boost would be a lot less responsive than it is currently as when the turbo is not spooling it creates back pressure in the system.
Was the T2/28 a roller bearing turbo if so this would reduce the effects slightly but nothing like where you wanted to be, trust me i'm speaking from personal experience.
My car with the large turbo doesn't start boosting till 3k+ and doesn't hit full boost till about 4.2k but mine has an 8k red line so not so bad. Also with mine being a 2 ltr its still not too bad off boost.

a standard T2 off an old rs turbo wouldn't be a bad idea but need to be roll bearing.

swebb200sx wrote:Good decision to stay away from the larger turbo, Knowing what my spool time and boost was on a T28 on the little engine in yours this would be horrific
You wouldn't start to see boost till about 4k at a guess then not hitting full boost till after 5k meaning you would only see full boost for a very short time. Also off boost would be a lot less responsive than it is currently as when the turbo is not spooling it creates back pressure in the system.
Was the T2/28 a roller bearing turbo if so this would reduce the effects slightly but nothing like where you wanted to be, trust me i'm speaking from personal experience.
My car with the large turbo doesn't start boosting till 3k+ and doesn't hit full boost till about 4.2k but mine has an 8k red line so not so bad. Also with mine being a 2 ltr its still not too bad off boost.

a standard T2 off an old rs turbo wouldn't be a bad idea but need to be roll bearing.

Hi simon thanks for the input, yes i thought long and hard about the t2/t28 hybrid,,,,i took some time to dial my info into a compressor map for the t28 housing and small compressor wheel and i just dont think its a good idea on 1250cc it just wouldnt be making the most of it at my given flow rate. Good news is the GT15/GT17 hybrid conversion should be happening next month and ive decided to go to a clever setup -

The main problem with tuning the 1250cc SPI turbo engines is the standard manifold and single point injection is rubbish after about 130bhp and fuel distribution is naf which is a big no no at high boost as im sure you now,,,but i need to keep it to run the standard ecu (i cant afford indipendent as such yet) so what i have managed to do is mate an inlet manifold of off a punto 75 to my throttle body meaning i have a better flowing manifold with a plenum chamber and 4 injectors to take care of things when the car hits boost and the standard injector to take care of the off boost fueling! this alone can give 15 bhp over my setup but the other good thing is i have to fit the 75 head to match the manifold which happens to have far bigger inlet ports, bigger valves and a better flow rate at high rpm.
My Aquamist MF2 can continue to fuel the MPI set up when it sees boost. The MPI setup and the better head combined means i may be able to achieve as high as 170bhp if im willing to try running over a bar of boost and probably around 150bhp at my current boost, i also have a J and S ultra safe gaurd active knock controller on its way which will mate to a bosh knock sensor ive fitted to the block so i can bring the C/R back up to around 8.5/8.7:1 with safty. I have faith that this new set up and turbo will perform really really well, and it gives me room to go further should i want in the future.

thanks let me now what you think to this new set up.

jason

Just as a thought, have you considered using a 16v head as it should flow better? Chavellier was running a comfortable 150BHP with one so it might be worth thinking about

allanhelen wrote:Just as a thought, have you considered using a 16v head as it should flow better? Chavellier was running a comfortable 150BHP with one so it might be worth thinking about

Thanks martin, this is deffinatly something ive been thinking about. If i decided to go to standalone then it seems stupid not to but the thing that draws me to the 8v is the low end torque, but then i have never seen a dyno graph for a 16v 1242 turbo engine on a cinq,,,,id love to drive the 150bhp cinq. I would imagine using the 16v head would make for a very nice progressive power curve so it may give better traction over the 8v turbos like mine and your old one.
But would the low boost T15 turbine housing on mine be just to small for the higher flow head?? maybe it would call for a T2? my fear at the moment is that i have my turbo turned into a hybrid and build up the new engine only to find the power drops of early due to the turbine housing being to small

But i will have a spair 16v head laying around soon anyway so its on my mind,,,,,yet another spec to consider,,,, haha

thanks

jason

Right ive been doing a little research into the possible spec of my new engine and my new hybrid turbo.
I have found that my current Garrett GT15 turbo is a GT15454083-1 turbo with a 33.9mm compressor 56 trim wheel. At I run 15 psi at the inlet which means ill be running closer to 17 psi at the turbo, Ive found a compressor map for this turbo which indicates at this lelvel off boost im running a pressure ratio off just over 2, and flowing roughly 12-13lb/min off air which means my turbo is running only 70 percent efficiency at a massive 200,000rpm!!, its running close to the choke line meaning im on the limit hence the poor performance.
Ive been chatting with the guys from the mini turbo forum who got me the map and they are using the GT17 turbo from the Saab turbo which is good for upto 250bhp.

So tomorow when Midland turbos rings me back i need to descuss having the GT17 housing and comp wheel mated to my turbo.
The next thing is my compression ratio, as standard it 9.6:1, the 1.5mm decomp plate drops that too 8.6:1 plus the extra gasket which again drops it to 7.6:1. But my head is skimmed roughly 1mm raizing it upto around the 8:1 mark with poor fuel squash due to the lift on the head itself.
So tomorow when i finish work im going to whip the head off, throw away the decomp plate, remove the stage two head for a standard worked over head that hasnt been skimmed and use two head gaskets to drop the C/R to around 8.5:1 as a tester for the new engine.
Then when i get the hybrid back ill pop it on and go for a setup at 1 bar boost too see what this setup behaves like.

On the mini forum they are getting 150bhp from an 8v 1301cc with a garrett gt17 turbo and a big intercooler running 0.65bar of boost!!!! thats insane but it show what can be done with the right setup.

So im stuck at work tomorow night on my own for round 400 with the cinq

jason