924Board.org

[Revis Rose]

Ok this may sound like an old question, but what is the max Safe Limit of boost for a Seires 1 931 with or with out an intercooler? I am thinking of racing the Ratted Out Shell, the rules will determine wether or not, if it gets a charge cooler. I am doing reserche as to classes and restrictions, and if it is allowed I will put an intercooler on it, other wise not. I have heard that the 7.5CR S1 931 can take everything from .8 to 1 bar. What accual expeirence does anyone have on this? Any help would be appreciated.

[numbers]

Well, at the risk of getting called stupid again, I will tell you that I have been running my '80 931 at 17 PSI for three years. I am using 91 octane pump gas with no intercooler, and stock timing. I have had no detonation, even though I am at 5000 feet of altitude. However, the car runs hot. I have upgraded to the Performance Products heavy duty radiator, and this helps, but I will still get into the red zone on hot days in traffic. The only other problem I have is that I keep running into the rev limiter, because the car accelerates so fast in first that you hit the limiter almost as soon as the boost comes on. I am not recommending that you run that much boost, just letting you learn from my experience, so you can make your own decisions.

[16 w/porsche931]

dear dave
how did you get 17 psi. are you using stock turbo i know it can't be stock waste gate or pop off valve? yeah i have a 931 in the process of rebuilding the engine and clutch(but need a head) i'm 16 and all my friends have these hondas that well, they are pretty fast so i didn't want to make a bad name for porsche. so i wanted to run some serious psi. i was also thinking of running a boost controler to keep temps down and still go fast when i want to.
thanks nate

[John H]

Just as a guide the over boost switch on the Series II units (same as the early ones?) cuts the fuel pumps off at 1.4 bar (about 20 lbs) boost.
Therefore you could run up to that - but whether the motor would last for long is debatible.
I run a Carrera GT replica with 8.5 compression piston's, GT intercooler and 96 octane gas for road and 100 octane for race and up to 1.1 bar (16 lbs) boost. I've being doing this for 14 years and the motor still starts well, develops good power (though with 260,000 miles on the clock it is a bit tired now)

[ This Message was edited by: John H on 2001-11-07 11:08 ]

[numbers]

I use a variable boost controller that I made by retaping a cheap air pressure regulator from an air compressor. You will also need a boost guage. I have pictures available if you decide you want to try it.

[16 w/porsche931]

if you have more info on the custom boost controler i would love to see it thanks alot nate. email me

[TonyMechanic]

I too am interested in your boost controller. Please email me at xplosive_10101@yahoo.com. Thanks

[Rick MacLaren]

Numbers: You're not stupid. You've just got more balls than the Toronto Raptors.

[numbers]

Well you know Rick, I spent a long time doing analysis before I took the plunge, and I am still suprised that the head gasket hold that much pressure. However, looking at what John is doing with the higher compression pistons confirms that these little engines are well built.

[numbers]

Tony, I tried to email you some pic's of the boost controller but got a message indicating that your mailbox would not accept that size file.

[John H]

Tony,

Go to the following site - I've loaded aword document that explains how to make an adjustable boost controller
http://communities.msn.co.nz/924CarreraGTInfoSite/messageboard.msnw

[Rick MacLaren]

Probably your heavy duty rad does a lot of the cooling work when the car is under intense load.

[TonyMechanic]

Numbers: could you try sending it to TonyMechanic_10101@yahoo.com? I appreciate it greatly.
John: your site tells me that I need to login to access that file. Is there any other way?
Thanks for all your help, you guys make up the nicest message board I've seen online. Way 2 go!

[Cbass]

Is this the infamous Home Depot boost controller? Call me overcautious, but I'll stick with factory parts.

[wdb]

diagram of infamous home depot boost controller
http://www.924board.org/viewtopic.php?topic=1822&forum=4&0

[ This Message was edited by: wdb on 2002-03-29 00:01 ]