Motor is a stock d16z6 in eg civic

Turbo is Garrett 18g

Right now the turbosmart IWG is set to 10psi which I think is too much for my stock motor. I'm going to order a new spring for it but I don't know what rate to order it at.

So how do I estimate how much HP the turbo will produce per psi

 

Thats a 400 HP turbo. Way too big for a 200 HP goal.

 

the previous owner was making 330hp at 20psi So I should be able to lower it to 200hp

 

Yes you can run a 5-6 psi spring in the gate and adjust it to 200 HP. It will be laggy but its your car.

 

It's only temporary until I build up my extra block. Im learning how to tune with this so I want to run conservative while doing so

 

Honda Horsepower Calculator by ZealAutowerks

has worked well for me, it cant be exact but its still helpful

 

I wouldn't bother than. The 18G is TERRIBLE trying to run out of its efficiency range under 10-18psi which is well within it. If you were doing 300-350whp, that's a different story. Otherwise, for 200whp, you're even fine with a SAAB /Volvo turbocharger or something in the 24lbs/min range. Although for a D-series engine, for 200whp, I wouldn't bother turbocharging at all until having some internals installed. That's better left for a B-series swap or something.

It's not the PSI that matters whether or not it will blow an engine but how it's tuned and the internals of the engine itself. You can't make a turbosmart go down past it's spring rate of 10psi, and the standard GReddy internal gate is a 8PSI rod actuator. you can't go below that either.

Stop thinking of PSI. That thinking never works.

 

To the crankshaft, yes, possibly at about 640cfm or 41lbs/min.

 

turbosmart makes a 4 lb and 7 lb spring. I want to learn to tune with a turbo so I thought lowering the psi would make it safer for the block. It's not really about making power at this point so much as learning to tune with boost and power later with a built block

 

Yeah, but when you learn to tune you would be at the lower levels anyway at partial throttle tuning (that's what the acclerator is for..) So,you wouldn't be at full throttle to get the 10psi anyway. Many a car has been tuned without using the absolute lowest spring possible.

Listen, you can pop a motor at 2psi with a 15G. As I stated, PSI DOES NOT MATTER AT THIS POINT YET.

 

Used to have a 18G on my 95 Talon. Seems like I made the same power at 16 psi as I did at 20 psi. Went to a custom 20G and it was night and day difference.

 

I have a Z6 block w/y8 head right not at approx. 9.45:1 CR. I'm looking at doing a Vitara build with custom rods that would put me at about 8.61:1 CR

Is going .84 lower even going to be noticeable?

 

I dont think you would notice it that much on a D-series since they are so weak off boost anyways..

 

If you're going to spend the money on custom rods, why not use better pistons and get the CR you want? You're already spending a lot of money rebuilding it, what's another $1-200 on the correct set of forged pistons?

 

It's a combo from P2P0 w /138.63mm rods and vitara pistons for $387 shipped.

If you know of a forged combo for round that price let me know.

 

gotta pay to play...I wouldn't bother with vitaras, not gonna be very much fun to drive off boost with that CR especially on a D series.

Then again I wouldn't bother with a D series anyway. The thing with dseries is they are alright when using a stock block build IMO. once you start getting into building the block with forged internals the price between just going to B-series is negligible and well worth it at that point.

 

Turbine wheels were different between the GReddy unit and the ones for DSMs. Plus, psi differentials between Honda D16 and 4G63 also account for differences in head flow rates

 

I keep throwing around the idea of a b-series but I would be spending almost twice as much for a stock b series as I would to build the d-series.

 

I never understood why the D series crowd jumped on board the vitara boat for a street car. 8.5:1 isnt streetable at all.

 

Actually, 8.5:1 isn't that bad. It's that 7.4:1 & 7.8:1 that are just awful.

 

When I first read that, i wanted to disagree...then thought about the CR for my STi. Its only 8.2:1, but matched with a tiny little turbo, its pretty responsive

 

And you get throttle response before boost kicks in with it that low? (the Vitara people, not the subbies)

 

Even the newer STi's with the slightly larger VF48 are pretty doggy off-boost. My 06 with the VF39 was much more responsive

 

I remeber boosting my 8.8 B20 and it lagged before the turbo kicked in. I hated it. Anything from a dig required brake/boost

 

I can get to 8.81:1 taking the middle out of a y8 gasket or 9.09:1 with a single layer Cometic gasket

is gaining .49 in compression really worth $90?