88T2 w/ J-Spec Motor with about 50000 miles on it, Full Racing Beat Exhaust w/ FCD, Cold Air Intake.
Boost is a little better than stock until around 6000 RPM then gets up to 7psi, hits about 7-8 something in 2nd gear and peaks about 9 at the top of third and fourth.

I have a 255lph walbro fuel pump ready to install and I want to raise the boost to 10psi with a manual boost controller. I'm at about 5300 feet elevation so I think that running 10psig should be no problem, after the secondary injectors are working.

I'm just a little worried that I won't have enough fuel to handle 10psi under 3800rpm. From other's experience has anyone had a problem with this setup? Also, will I even hit 10psi before 3800 rpm? And using the stock wastegate would I possibly see any boost spikes above 10psi if I'm not getting any already without the use of a boost controller?

 

I wouldn't worry about fuel delivery for the most part under 3800RPMs myself. Also, a walbro should be fine up to 10psi with a FCD. As for boost spikes, if you have a stock S4 WG you will probably see spikes with full exhaust and intake. A boost controller won't correct this either. You have to pull your turbo and port the wastegate.

 

A little confused as to what you mean...

This is the thing, right now I have the stock s4 wastegate and I am running the Racing Beat full Exhaust - downpipe, with the three mufflers and y-pipe- and I have never seen more than about 9.5 at 6000+ rpms in third gear and higher, mostly I think due to the elevation being 5300ft here. So the max boost is about 9.5psig, but is due to creep, I haven't yet seen a sharp spike. I don't want to lower the boost, what I want is to raise it to 10psi by the MBC, so I see more boost before it increases due to creep, mid range boost, but I also want to be able to use this engine for at least another year, so I worry about sick spikes.

So are you saying that with using a MBC set at 10psi and running the full racing exhaust I will encounter spikes above 10, even if I'm not seeing more than 10psi now from creep and the small stock wastegate?

 

0.5psig is not going to give you any significant amounts of power, so be happy with what you got. If you're worried about the safety factor, then I wouldn't recommend doing it.


-Ted

 

I believe that running 10psi from 4000rpm to 7000rpm rather than 6psi and creeping to 9psi will give me a noticeable performance gain.

Anyone have an answer to the spiking question?

 

I hit as much as 13psi (on a cold night) at about 3krpms. Never had any problems with my current setup.

If you DON'T port your wastegate you will blow your engine up. If you do port your wastegate you will be fine.

Boost spike is different then creep. Put your MBC as close to the wasgate actuator as possible to eliminate boost spike. Boost creep will go away with a ported WG.

 

You need to invest in an EBC. Trying to tune an MBC is going to be tricky if not downright impossible.

The low spiking is due to your elevation. If it's not spiking now, the MBC shouldn't spike as much either.


-Ted

 

What is a stock s4 psi at??

 

if you use a MBC, you won't be running 10psi from 4-7. if you have it set up to hit 10psi at 4k, then it is still gonna creep until you let off. which means you'd then be boosting...let's say 13psi by the time you hit 7k. the only way to really control boost is to have the ported wastegate to get rid of creep. only then will you get the most from a boost controller.

 

5.5psi last i read.

 

Ahh, I see what you mean now...
I guess since I have the tools for porting I might as well port, it seems about a days work.

 

i was going to port mine while i was doing the motor swap. but changed my mind when my dad(thinks he knows everything) warned me about the possibility of getting small pieces of metal in/near the main bushing that the shaft rides on. i tried to take housing off the rest of the assembly but wouldn't budge. yes, i removed the six bolts. it won't be a problem till i get the exhaust on.