924Board.org

[NiceOldTurbo]

I have owned my 931 for almost a year now and I love it. But I am feeling the need for more horsepower. What are the best and cheapest mods out there for my car? Thanks in advance for everyones help.
tyler

[Joes924]

Look around do a little research ....theres

alot of stuff more so for your turbo I think
since yours is a 82

[ This Message was edited by: Joes924 on 2001-10-29 13:17 ]

[NiceOldTurbo]

thanks, what are some of the best places to look? ive looked at a few Performance Parts magazines and Automobile Atlanta but didnt really find anything. any advice would be appreciated. thanks again.
tyler

[eturbo924]

Post this question down in the 931 part of the board. Bob is just waiting for these questions. Also check out some of the 931 sites. Intercoolers and more boost are the going mods.

Eric

[Rick MacLaren]

You have a turbo?

Get a boost spring or boost controller. That'll satisfy your speed needs for a while.

The spring is like $100 US. Same with a good controller, although cheaper ones are out there.

[NiceOldTurbo]

thanks a lot, do u know where i can find a spring or controller? sorry i dont know these things... like i said ive only had it for a year. thanks again

[Rick MacLaren]

I think Andial sells the spring. I bought mine off the web for $50. It brings your boost up to like 1 bar. Then they sell spacers. I use, on my car, the 1 bar spring, plus a 0.2 bar spacer, plus a boost controller. I leave it at around 15 PSI and now that it's cold, no alcohol or water injected.

Any place that sells 911 parts will have the 911 1 bar boost spring.

[NiceOldTurbo]

I might just be stupid, but I didnt see anything on andial about the 931. I did see the 930 turbo, is that the same thing? Can I use another boost spring or boost controller for another car on my 931? I'm new to the Porsche scene and need some help.
thanks,
tyler

[924RACR]

The 931 has some rather unusual turbo hardware compared to modern EFI turbos, but it shares all the technology with the 930. So yes, most 930 parts and mods will fit, at least as far as the turbo stuff. They just don't market to the 931 owners, because there's so fewer.

Read the Tech Section (link above), the info is all there, including the links to Andial. That's why the Tech Section is there.

_________________
Vaughan Scott
Webmeister
'79 924 #77 SCCA H Prod racecar
'82 931 Plat. Silver
#25 Hidari Firefly P2 sports prototype

[Rick MacLaren]

Hi NiceOldTurbo...You said:

I might just be stupid, but I didnt see anything on andial about the 931.

True. You might be stupid, or even boneheaded, but nothing you've said to date indicates true stupidity yet. You earn the badge of "Truly Stupid" once you've bought your second 924.

You said: I did see the 930 turbo, is that the same thing?

Yes. They're the same thing. Even the part number on the wastegate, where the spring goes, is a 911 part number.

You said: Can I use another boost spring or boost controller for another car on my 931?

Yes. There's no reason why you couldn't use the spring from an old washing machine. But it won't necessarily be 'tuned' to allow only 1 bar of boost. The trick with the 911 extended boost spring is that is is TUNED to provide EXACTLY the right amount of boost. You can't get that kind of precision from any other aftermarket part.

Yes. You can use another boost controller from another car providing it is not electronically rigged. Also, you won't be able to bet on how much PSI is actually delivered. You'll need to use your gauge to figure that one out.

I think this is probably the only case where the cheapest solution comes from buying the 911 part. If I were you, I'd just put out the money for the 911 extended boost spring, 1 bar, and be happy. You'll spend ages trying to find a cheaper alternative.

One thing about the Porsche 924 Turbo: It's the cheapest thing to soup up. And you'll never get tired of hearing that whistle noise.

The boost spring, or equivalent boost controller, is the cheapest way to get horsepower from your 931. Arguably, you can hook up a manual boost controller with a little dial and reduce the amount of air reaching your wastegate. But that solution is frought with difficulty, notably, people tend to crank up the boost waaaay past where it 'should' be to run successfully. Many guys have done this act. And they are the ones writing into the board asking "What does the car sound like when you've melted the head?"

Rick
_________________
1980 Porsche 931 C2H5OH/H2O injected 15 PSI
1979 Porsche 924

[ This Message was edited by: Rick MacLaren on 2001-10-30 07:13 ]

[Peter]

Check out this link for a DIY boost controller and a good explanation of how it all works.
http://www.autospeed.com/A_0670/P_2/article.html

-Peter A. Holiat

[Rick MacLaren]

Yeah Peter's boost controller is pretty good.

However,...

Ok. First, the wastegate system on most of these cars is 20 years old. What happens to a wastegate in that timespan?

1. The spring, under tension, grinds into the aluminum housing of the wastegate and creates indentations in the aluminum.

2. The rubber boot that is attached to the wastegate erodes and typically gets a hole or worn away.

By using an extended boost spring, you are guaranteed to have to open up your wastegate and have a look. Once you see inside, my guess is that you'll want to:

1. Buy a new spring, cause you'll see how much deformation of the spring can happen over 20 years.

2. Buy a new boot ($50) cause you'll see how much wear has happened on your boot.

3. Fix and recondition your wastegate.

Here are some more reasons you'll probably prefer the boost spring over the boost controller.

1. If you use a boost controller like Peter is showing you, then without a boost gauge you'll likely blow up your car.

2. The boost gauge is an added expense that you really must have to use a boost controller. Sure, you can use a boost controller without a gauge, but then you're beyond stupid, or you are extremely wealthy.

3. Once you crank the boost, you're gonna put more heat and wear on your wastegate. And my bet is that after 20 years, it's gonna wear out anyway, and then you'll still be calling Andial for a boot and spring and you'll still have to recondition your wastegate.

Finally, in most climates, you can't USE a boost controller over around 15 PSI anyway without either an intercooler or alcohol injection. Sure, you can use it when it's really cold, but you're still risking detonation with the kind of boost you get from a boost controller, and you'll have to up your gas intake with a new fuel distribution unit.

Save your money. Get a spring. When you want to spend more on a fuel system and maybe an intercooler, then get the controller and gauge. That's my advice.

[Peter]

My previous post was mainly to provide a link to an interesting article that is right on point. Also, for those who are not familiar with Auto speed magazine online, it is worth checking out as they have numerous relevant articles for FREE. Anyway, back to my reply.
I agree with Rick that these cars are old and any increase in power sought should first be undertaken by examining, repairing or replacing (updating possibly) the core mechanicals. In this case the wastegate spring and diaphragm and maybe rebuilding the turbo (since you are halfway there already), should be done if you want the car to last. Once the wastegate is disassembled, it’s easier to just go with the 1 bar boost spring and leave it at that. This is the cheapest and easiest way to go, and for many, the best route. Others choose a different path.
And by Rick’s signature line, he has chosen the other path by going with alcohol/water injection, which requires, an additional pump, reservoir, fine-mist nozzles to atomize the spray, pressure regulated switch to activate pump, knowledge, patience, time, etc, etc.
As for choosing a different path, I plan on using an adjustable boost controller (which is basically an air valve, like on your Sears compressor), boost gauge (which again is just an air gauge like on your Sears compressor), an additional air valve to control wastegate creep (read the articles linked in my previous post), an intercooler (either a 951 installation like on Jon Furst’s web page –how is it going Jon) or a Saab 900 intercooler mounted where the oil cooler is (with dual oil coolers mounted where the horns are) , and a pressure activated switch to active the cold start valve (which is basically an full open/close electronic fuel injector) to increase fuel upon greater boost.
What I don’t like about going for a 1 bar spring is that you might not want to run 15 psi. Rick is running 1 bar but he also has alcohol/water injection to cool the charge and I am sure that his car is well maintained, as he appears to be very knowledge. However, and although I don’t have enough information to be definite, I believe that running 1 bar on an old series 1 931 without any mods to cool the charge or knock sensor to retard timing may be detrimental. Anyone who is currently running this set up without mods please reply.
Anyway, my point is that there are many ways to achieve your goal. Do a little research and ask some questions. Then budget some time and money for your project. Then multiply this figure by three. Soon you will be there.
-Peter A. Holiat

[NiceOldTurbo]

thanks a lot guys, i appreciate it.
tyler

[Joes924]

detonation ... bed word all sounds near enough though..must be fun bein turboed