hay for all the ca18det people wondering which turbo would be best as an interested in buying another turbo.. i was thinking gt25 (420hp) or gt28 as better top end? i have got a fully rebuilt motor with fordge's head work and bottem end done .. any advise would be greatfull...
im tending towards gt25...later on go for a t3/t4 rollaa...after $$ grows

Andrew reckons his 350HP GT25 was too small. You need to go the GT28. But seriously, the S15 GT25 is seriously good turbo, and certainly nice for street driving. You'll need to balance your engine to very fine tolerances if you want to run a big turbo and 9000rpm to make it worthwhile.

For my CA18, I've got the biggest GT28, with the .7 compressor and T25 flanged .86 exhaust turbine. I probably wont have it started before November, so I can't tell you if it's a good size. But a good condition S15 turbo would give you 180-190kW at the wheels, which is like 25% more than an HSV V8 Commodore, in a car 1/2 the weight. My brothers S15 turbo/SR20DET in his 1600 is seriously undrivable above 3000rpm..it's all sideways in all but 4th and 5th gear. Remember the days when it was cool to be able to chirp between gears.. seriously a different ballgame these days.

Chris

Any turbo bigger than the smaller GT25s will mean you'll need a custom manifold, which means new (modified) front pipe, new intake piping maybe, new oil lines and water lines. New boost signal pipe maybe etc. Only a couple of the smaller ones can be considered "bolt on". Yes they have the same exhaust flanges..but there's more to a turbo than just the exhaust flanges.

It really depends on what you want to use it for !!! If street duties and ocasional drag race I personally think you wont have to go any bigger than the 400hp GT25 these turbos can make well over 400hp if drag race only you could go bigger again but would be a bit of a dog to drive. For a daily driver the 350hp ray hall special trim GT25 would be optimum with great all round performance you could expect 200rwkw from this turbo with the rigth setup and still drive it around town all day without being a pig.
Good luck and let me know how it goes another freind of mine just got his rebuilt CA18 going last week it only has the 300hp turbo he is running it in at the moment will be intersting to see what it produces when run in then tuned for lots of boost. its in a little 1200 ute
heers Andrew

hey chris my first turbo was a 280hp GT25 it was a bit small still made 225hp or 170kw at wheels with only 15psi was pretty well maxed out at that still run 12.0@113 on street tyres.
Andrew

thanks for info mechanic said no point in going and bigger than a gt28 he reckon unless u spend big buck on the inside of u motor thats whenu gona get good use out of a bigger t3/4
i thought that as well seing as the motor is or was a 1.8 being bored out 2 nearly a 2lt ive decided 2 go for the biggest gt28 soo i dont have 2 change turbo's down track good for street and drag.. thanks heaps for info guys hoe 2 cya at jamboore hopefully my ute will be on road and can drive there...with new turbo..