So I've run my current setup for a summer and I've been bit by the more power bug. The setup is....

D16z6 bored to 75.5mm
wiseco 8.5:1 pistons
Eagle Rods
stock head
Greddy 18G turbo w/ Turbosmart internal waste gate
MAC boost solenoid
RC 750 injectors
Walbro 255 pump

The car made 225 hp and 215 tq at 12 psi. The tuner said that was about the max for the turbo. It's tuned at 15 psi but it spikes to 15 psi and drops to around 12 psi. The car is fun to drive and the power band is nice. I would like to go up to around 300hp that still spools decently quick.

So the question is what are suggestions to reach my goal of 300 HP

 

You're tuner is off base. Those easily make 350whp at over 18-21psi. You need better boost control and the gate itself. You sure your not talking about a 15G? That has a limit of about 260whp.

 

nope it's a tdo5sh 18g. I was reading some other threads that you were saying about the flapper for the internal gate not being able to handle it. The spring in the trubosmart IAG is set to 8lbs.

it's a very reputable tuner so I trust him when he said it was spiking at 15 psi.

so would welding the flapper and converting to external an external gate be my best option? If so any suggestions on a manifold? From what I've read it's a t25 flange and they seem hard to find for a d-series

 

Are you using the Greddy manifold and cast elbow?

 

If he is, what he needs to do is to reset the wastegate slightly higher, and to either get rid of the cast elbow & custom make another one that would work with that Turbo.

The internal flapper door would need to be ported out to about 34 mm and preload of the wastegate should be said to about 12 to 15 pounds on the arm.

He would then need to have actual boost controller. Even if he uses a manual one, he'll be fine.

Either way, no need to get rid of the turbocharger

He does not he have to get rid of the greddy manifold at all. I've had those worked over 400whp on D & B series engines easily

 

I would agree w/ that. The elbows are awful. They can be heavily ported all the way through along w/ the gate port. I wouldn't change setups just to make 300whp if everything you have is in good condition, but I would without a doubt port the elbow, gate housing and probably match the manifold itself.

 

No I'm not using the Greddy DP elbow. It's a custom 3 in Vband DP. I should've mentioned that. So I should...

Port the flapper to 34mm. Does that mean I would need need a new flapper to cover the bigger hole?
Get a 12 or 15 lb spring for the IAG

I do have a boost controller. I'm using a solenoid controlled through Hondata.

 

There's enough material in the gate opening (you can see the smooth-casted area around the door area) without having to replace the door itself. Changing to a higher spring for your Turbosmart IWG with a slightly higher pre-load setting (that's the threaded area at the base of the actuator arm). This helps keep the door closed longer to help avoid spikes.

For now, I'd do these things and forego the solenoid/laptop controlled boost control as part of your test, and use a manual boost controller to test to ensure that the spring preload is set properly. It's difficult to know whether or not your port job was successful. The fact that you got the old elbow out is great, but you need to see if your new physical settings are legitimate before using laptop control.

 

Awesome. So let me make sure I have this all straight.

port the waste gate hole on the flapper side to 34 mm.
get a 15 lb spring for the IAG
unhook the solenoid and use a manual controller.
So if I get a 15 lb spring I could set the boost controller to say 12 psi and if it holds there and doesn't spike then I will know that the port job was successful. So I should be able to do this before taking the car back to the dyno since it was tuned at 15 psi and that will give me some wiggle room if it spikes?

Or would I get a 15 lb spring, set the boost controller to say 16 or 17 psi and see if it holds there without tapering down.

Sorry for all the questions. This is new stuff to me and I very much appreciate you both sharing your knowledge with me

 

Use PSI for pounds, not LBS. Remember, you're not measuring/seeing weight, you're measuring / seeing inducted air pressure over atmospheric barometric pressure at the intake manifold.

You would get the upgraded actuator spring, and see if it holds steady at 15psi, even if it slightly spikes to 16-17 then tapers downward. Remember, smooth and steady acceleration in 2-4th gear, (no launching), to see if the pressure holds after

 

ok awesome. Sounds like I have a plan for winter then. I'll have to get a hold of the guy that had the turbo before me. He had a 14 psi spring in it and was making around 320 or 340 hp and had the dyno graph. Perhaps it was already ported.

Again thank you. It's always nice getting straight knowledgeable answers.

 

So I was doing some thinking. if boost creep is not one of my problems is there really a need to do the porting? Since the psi is dropping wouldn't I just need the higher psi spring to keep the wastegate closed?

Correct me if Im wrong but from what I'm reading porting the gate is more for preventing boost creep/spike

 

Yes. You need to port that gate opening, if you've changed that spring and there's no positive result. (You're saying someone else already made 320whp, which is why I'm surprised you're asking for bigger turbo options. Perhaps you thought it wasn't possible based on what your tuner said? .

Honestly, I'd do it first anyway just to be certain, once you have the other gate spring.

 

right. No harm in doing it so why not. I thought about the bigger turbo because the other guy had a cam, head work, intake manifold and such so I thought maybe that had something to do with the extra hp.

in reality I asked alot of questions about the turbo on different forums and got mixed answers. Some said the turbo would be too big for the engine some said too small. The tuner said it was too small. Anyone could post a dyno graph and claim numbers so I trusted what the tuner said which wasn't entirely wrong. I just reached the max of what it could do in that state.

I even worked out the math with the compressor map. Live and learn. I trust your advice. I've followed your answers on the forum for years and you know your stuff.

 

Thanks. Much appreciated. Sometimes, as much as people trust tuners, they're only limited to what they've seen from certain turbos, and not what they actually know.