turbo performance Options

[nsyr]

I know there a few people out there with turbo 4's. Does anybody have any performance or reliability figures.

[Sammy]

Intercoolers are not magic, they are just like most mechanical devices. They offer a performance increase in some cases, but at a cost.

Even the very best designed intercooler will have some restriction. if they didn't they wouldn't cool very well. This restriction reduces the efficiency of the turbo and can and will increase turbo lag.
The trade off is that they allow the tuner to run a little more boost because the cooler charge does not increase the combustion temperatures as much as a hot air intake and it is more dense.

BUT...... if we study the law from that guy names boyles or boils or whatever,
air doesn't get very hot if you only compress it a little. It is not linear, prolly more like exponential.

At around 3 psi boost you would most likely not have any benefit from an intercooler. The intake air would prolly only be about 10 degrees over ambient (guesstimating from past ezperience here, cut me some slack) Probably just the opposite, you would have negative effects from intercooling at that low of boost. The down side would outweigh the upside.

Even as high as 4 or 5 psi (depending on the turbo efficiency rating) there is little benefit to an intercooler.
At around 6 or 7 psi it starts to make a difference and is justified but at that point you usually need to look at the rest of the engine to see if it can go much higher in boost anywho. These numbers are approximations and generalities and there will always be an exception.

My SC is a good example.
I'm up to almost 7 psi with it with no pinging and no problems, but if I get into the boost for an extended time (like two full passes through the gears on boost) the intake system absorbs enough heat that it gets "heat soaked" and I notice a loss of performance and sometimes even a ping or two. In that case an intercooler would be of a benefit at as low as 6 or 7 psi boost.
I found the threashold and do plan to build a custom intercooler. If I were to keep the boost down to 4 or 5 psi I prolly wouldn't bother with the intercooler.
I also plan to recurve the dizzy to take out 5 degrees advance and also install another hobbs triggered injector. With all that i predict I can get above 8 psi, but I doubt I can go much higher than that reliably.

Plus the big question is, where the heck do you put an intercooler in a 914 without hacking the poor car all up? a 911 is relatively easy, a 914 is not. The trunk is about the only logical place and that would require a whole bunch of tricks and scoops and holes and louvers to get enough air flowing over it to keep it cool.