my setup:

S4 TII, 46k miles
stock turbo, with a 34mm ported wastegate
RB REV TII turbo back
Rtek 1.7
RC 750cc secondaries
hallman pro rx MBC
K&N drop in air filter

right now the car is at the stock 6psi, and never creeps.

my question's are:

1. What is a safe maximum boost level if i wanted to throw a few more pounds of boost at it with my current setup?

2. Would it be wise to up the octane to 93? or should i stay at 87?


i have a wideband on order, and after that is installed, i would like to install the MBC.

thanks.

 

You run 87?!

I thought Premium (91) was required for T2's?

 

I think the general rule most people go by is use the highest octane available if you start running more boost than stock. It's just good insurance. You should be fine running as much as ~12 psi with your fuel setup (if you have an upgraded fuel pump too), and at that range I run nothing but 91 octane. There is no 93 octane around here unfortunately.


No, all FCs are rated for 87 octane from the factory. It's covered in the owner's manual.

 

oops, i forgot that i have a walbro 255, and a fuel pump rewire.

93 octane is readily available.

i was actually thinking 10-12psi would be safe with mysetup, but id still like more opinions if possible.

thanks so far.

 

I had the exact same setup, same 750 injectors, rtek, eveything you have on my old TII, except I was running a FMIC, intake, and a SAFC neo on top of the rtek 1.7.


I tuned it off of a NGK AFX wideband, 91 octane. I was running 11psi regularly, and with 0% correction I believe my AFR's stayed around 11. With the safc adding the most correction, I could get AFR's in the low 10s. Now my wastegate was mildly ported and I got on it in 4th once, and at 4500 rpms the AFR's hit 13 @ 15psi(yeah stock turbo).

EDIT: however this was on a streetported motor, so obviously the afr's would be lower on a stock port.

I would suggest that you could do 11-12psi, as anything more and the stock turbo pumps heat.

 

Be careful, you can get spiking with an internal wastegate and an MBC when it gets cold out

 

anyone else have an opinion on this?

 

Holy crap, does this go for JDM FC's as well?

 

i agree. i'd see how it is @9, and then maybe go 10-11. you probably wanna run more octane too.

if you drive like an animal, you might want to also consider colder spark plugs, like 9L and 11T, two steps colder

 

if you have all the above mods done that is what we are saying.

 

Get the Rtek 2.1 and monitor your intake temps through the factory IAT sensor in the manifold.

 

In the 10-12 psi range with the stock TMIC, the IATs aren't too horrible. Depending on ambient temperature, I generally see them around 100-130F during a long WOT pull. The stock turbo will only be able to make more than 10 psi in a small RPM range anyway, so as you're winding through the gears, it will be making less boost in the high RPM range. Of course intake and exhaust setup have a large influence, and this is with pressure measured at the manifold (not the turbo outlet).

 

Cool. Ill put 93 in it, and start at 10lbs, then go from there.