[Supras] What is Max Boost for a MIII Stock Engine

[Dan Gyoba]

Well, I know that people have done 20+ PSI on a stock bottom end, but there is definitely work to be 
done before that point.

The fuel system is good to about 12 before something needs to be done.  A Lexus AFM and larger 
injectors, or a stand-alone EFI system (and larger injectors) is the real way around that.  An FCD will 
get you by, but you run the risk of a lean mixture, which will result in things breaking.

Some will argue that the stock head gasket/bolts/torque spec aren't up to stock boost.  They may well 
be right.  I think that the stock gasket may not be as bad as all that, but at the very least, the 
torque spec for the factory bolts is too low.  Certainly a proper metal head gasket job is stronger, 
though.  (Yes, I see that you did the head gasket, but you didn't specify details.)

The BOV will need to be better to handle the larger pressures and airflow as well.  The stocker isn't 
up to anything more than the stock fuel system, from what I understand.

The stock intercooler is supposed to be a good one from what I understand, but an upgrade will still 
help you make more power at less boost pressure.

And, as Jeff said, it comes down to POWER.  It's not about boost pressure, it's about the O2 that the 
engine takes in and uses to burn fuel.  That's what makes the power, and puts stress on the engine 
components.  14 PSI on a stock CT24 isn't the same as 14 PSI on an upgraded CT26, which isn't the same 
as 14 PSI on a T04.  Assuming that you have an upgraded CT26 from your description, as long as the rest 
of the system (Fuel, intercooler, BOV) is up to the task, you shouldn't have any real trouble running 
that turbo up.

On 28 Nov 2007 at 14:05, Daniel Hodges wrote:

> Hi Guys,
> 
>  What is the maximum boost a Stock MIII will take. Turbo has been
>  redone
> good for 20 PSI Head and gasket have been redone. Have not touched the
> bottom end.