Turbo thoughts, educate me!
 

I'm still undecided whether to go turbo or SC (Sprintex mostly).

If I go turbo, I want to go custom. I've built a 600 whp SR20 S14 in the past, so I'm not afraid to work on the car, plus I have friends who are fabricators/welders, so they'll help me build the header etc.

My question is about the turbo itself.

A turbo with the following specs
60mm inducer
84mm exducer
63 A/R, 3" downpipe outlet etc.
On straight E85

Almost exactly like a Garrett GT35R.

Would that turbo be viable for ~300 whp? My thinking here is that a smaller turbo would make more cylinder pressure at lower rpms (when you have a bit less oil pressure), create higher EGT's due to higher drive pressure and be a bit more prone to detonation..

But at the same time, it's still a bigger turbo, may create more lag etc, but the boost would still be low, around 10-12 psi or so, with E85. The high compression of the FA would also help in this case..

Is it a viable idea? I honestly don't need instant power at low rpms, but I don't want only 1000 rpms of usable power band either..

It hardly takes anything to make 300WHP with most common turbos if you keep the stock compression ratio. If you build it and lower the compression ratio, it will take more boost to make the same power.

There is endless information on this forum about getting the 300WHP badge - Even basic kits like the JDL, SBD, Full Blown, PTuning, AVO, etc will hit 300WHP with a good custom tune.

EDIT - Just realized I misread the post. Didn't realize you had a turbo already. As has been said, that's overkill, if anything. You'll certainly make your goal.

You have way, way too much turbo for "just" 300whp or 10-12psi.

I make 300whp on 5.5psi on ethanol with my 18G.

that's a big ass turbo for about 300whp. I have a GTX2860r on ethanol and I'm making about 350whp. I know these turbos are good for up to 400 or 450? I don't remember off the top of my head.

Oh I'm well aware of that, trust me :) The turbo in question is capable of well over 600 to the crank.

Let me clarify - my concern is not at all if the turbo is big enough or will make the power. My only concern is, how bad would it be driving with it. I am expecting lag, but also not post-5k rpm for boost kind of lag.

I've been looking around Youtube for GT35R vids on spring pressure/low boost setups with 2L engines, that have significantly lower compression. And they don't seem to be that horrible to be honest. Just unsure on what to do.

To be completely honest, if a turbo of a larger size is at least drivable, but at the same time slightly "safer" for the engine (for the reasons I stated in the first post) then that's preferred in my world.

But maybe the difference is so small it's not worth it? I have no idea..

IMHO if that's your goal, go with a quality pre-fabbed kit, they've worked out all the kinks. You'll have a lot of extra money to invest reliability mods :)

Not so sure about that - excluding the absolutely cheapest kit/kits, I'm looking at ~$4500 for a turbo kit. That means turbocharger, header, downpipe and intercooler with piping. Plus a few bits.

Add shipping to the other side of the world on that, and 25% import tax, plus duty fees. All in all, $5000+, easily.

Whereas my idea of a custom kit would be sub $1000 for the turbo then the header and downpipe etc is mostly material cost. My friends will weld it all up.

Yes, then I need the intercooler, wastegate (unless I buy an internally gated turbo) and a BOV. Silicone couplers and such, sure, but the total cost won't even be half of a prefabbed kit..

Skeptical but interested :D Keep us posted on your progress

Usually paying for custom fabrication is $$$ but if your friends are super generous cracker-jack fabricators then I'd be interested in seeing how this turns out.

Sell the turbo and whatever else you have and put the money towards a kit.

Everything will be a guessing game because there’s not the range off off the shelf parts like for an S14.

I'm sort of skeptical myself, but still don't see this as anything impossible..

Where's the fun in that? ;)

Funny thing is, normally I'd say the same if for example a friend was in the same situation.. But I'm still pretty confident I can make this work. And read my post above about the cost - I am 100% positive that the custom route is cheaper than a kit for me, since I'm not in the US. A good kit with shipping and import fees and tax will be way over $5k.

I got a custom turbo kit done, paying minimum labor with a brand new GTX3076R for around 5500, that included going all out on several things like a garrett IC. I agree it's doable for cheaper than a quality turbo kit given the fabrication part will be done for minimal labor charge.

My recommendation is either a GT28 or GT30 turbo. GT35 will be considerably laggy.

G25 :D

Define lag.

Transient reponse? Spoolup window?

Why do you want a big turbo? Unused potential is meaningless potential.

I make your target 300whp on 5.5psi with a powerband of 2700-redline, real world, with my Greddy T518Z kit.

Spoolup was my main concern.

Partly because of the reasons I stated in the OP, and partly because the turbo in question is available for a super cheap price, brand new with warranty.

But it's not a must for me, I might go with something in the GT28-range instead :)