924Board.org

[-nick]

For 2.0L 924's.

So you want to turbo an NA?

This has come up so many times and there is so much mis-information
that I thought I would at least add up some slightly more realistic
numbers than what I've seen go around.

Target: 150hp with ~7-8psi
This would be about the lowest number possible to make this endeavor
even slightly worthwhile. Let's see what is involved.

Now what exactly would it take to put it together?
A turbo. Duh. Something with an internal wastegate and in reasonable
condition. I'll leave picking the correct AR to you. We'll say $200
for something decent.

Mounting: well, you're not going to duplicate the 931 setup or else you would
be changing the starter location, among other things. So mounting the
turbo on the exhaust side of the head is out. There simply isn't
enough room. So where? Well, lucky for you, that question has been
answered by the great people who produced the aftermarket ray-jay kit
in the '80's; pull out the washer fluid bottle and stick the turbo
in front of the timing belt on the exhaust side. Sounds pretty good
so far. Of course, you could pull the AC compressor out and mount the turbo there (real sports car owners smell like dirty pigs in the summer, right?), and then all you need to do is make a cross-over pipe that runs down one side of the engine, underneath the oil pan, then back up the other side into the
turbo. Then two more pipes that run out to the exhaust (turbo out and
wastegate out). You will now have the most in-efficient turbo ever!
Back to the original plan... Make up some funky mount from the turbo
to the block (~$30), then find something to replace the washer bottle
with ($20, you want to pass inspection right?) and you now have a
turbo. Cool! Oh yeah, plumbing...

Now that your turbo is bolted up, tow your car into the welder/exhaust
guy's shop (hmm, add on $100 for the tow to and from the shop). He's
going to be more than happy to see you, trust me. All you need is for
him to cut your stock exhaust at the flanges and weld on a new
manifold out of stainless steel. Wait, is it even possible to weld
stainless to cast iron? Probably not, I don't know, then I guess
he'll have to duplicate the flanges out of stainless too. Don't
forget, he also needs to weld and bend a pipe to mate the turbo outlet
to the exhaust. That's not all, you also need another pipe from the
wastegate outlet to the exhaust. "No problem!", he says, "it will be
ready in less than a year". Perfect, it will take you that long to
sell your house in order to pay for it. Really, how much could it be?
Well, I paid $400 to have a simple header-back exhaust made out of
aluminized tubing a few years ago. There were no complex bends and
the only welding that was done was for the o2 sensor bung. You need
some seriously complex bends, out of stainless steel no less, and a
manifold measured, cut, and welded, to fairly close tolerances. Think
about it. Just for fun, we'll say $500.

So the hotside is taken care of now. Whew! How about the cool side?
If we keep our stock CIS, then we need to remove the old plumbing that
connects the air-meter to the intake and change it to connect to the
turbo. Dump all the old plumbing, because you're running boost now.
You know all those cool photos of turbo engine bays with the bright
blue intake tubing? That's going to be you, about $75 later. It
would be cheaper, but you need a very large diameter 90 degree bend
right off the airflow meter. That's tricky. It's easier from there
on out, you just need some piping (can find it ready made on ebay) and
blue high-pressure hose couplers (also on ebay).

Now we're getting somewhere. The turbo hotside and coldside are
plumbed. Wait- you need oil to get to those turbo bearings to keep
them lubricated! All right, $100 for oil lines and fittings. Ah,
that turbo is really going to heat up the oil too- $100 for a ~10 row
oil cooler, $75 for an oil thermostat, $25 for a VW sandwich oil
cooler adapter, and another $100 for oil lines. I won't even bother
with the fabbed up brackets and hose ties that will end up nickle and
diming you throughout this project.

Ok, the turbo is done! It's cooled down with oil, hot exhaust is
going in, hot exhaust is coming out, inlet air is coming in through
the air-flow plate then into the turbo then out to the intake. What's
left? Fuel & timing. We can do this. The stock fuel meter is
probably good for more hp than you need, but with that hot air coming
in, you're going to want more fuel as the boost pressure rises or else
the engine is going to detonate. This gets tricky. Trigger the
5th/cold start injector? Forget it. All the extra fuel will get
sucked directly in the cylinder #4 and cylinders 1,2,3 will get none.
Bad idea. Only option is to piggy-back two extra EFI injectors that
are installed in the intake equidistant between the cylinders. In
other words, one injector is placed between cylinders 1&2, another is
placed between 3&4. We'll say $25 for two decently clean EFI
injectors. How are we going to drive them? I have no idea here.
Maybe you can get lucky and find some system that will just turn the
extra injectors "on" at 4psi and up (up means 7psi, you're not going
to break that number without an intercooler). We'll say $200 for such
electronics and the EFI connectors, MAP sensor, wiring, and wiring
connectors. I'd say that's probably very generous (on the side of
minimizing the cost).

Timing- this isn't too bad. MSD already has a nice kit for about $300
to retard timing under boost. And you already have some extra wire
and connectors left over from that $200 fuel controller above
(snicker).

One more thing! Boost gauge and controller. Toss in another $100...

Voila! Homemade 924 turbo. What did it cost? Hold on to your hats-

$1950.

Add in the purchase price of your 924na, say, $2000. Hmm,
$3950; you could find a 931 in decent shape for $3k, spend $950 on
intercooler, boost controller, ignition, and you've got 951 power. Or
you could have a 924na with 150hp that is ready to grenade at any
minute. Take your pick. Want more power or more reliability, just
add more $$, it still won't ever be cost effective to just buying what
the factory already made.

(Disclaimer- this is not meant for those who just want to engineer for
fun and have a couple years and a couple thousand bucks to kill).

PS- you have a 924S you say? Really the numbers come out to be about
the same (say $2k for a bare-bones turbo setup). Add that to your 924S
purchase price ~$4k, and you're now in 951 territory. All this for a
924S that now has an extra 30hp (being optimistic here) and doesn't
have the refinement of the 951.

Listen- these are great cars! A 924na is lots of fun. The 931 and 924S are
slightly quicker fun. Don't be fooled into thinking that they will
keep up with anything on the road just because of the badge on the
hood. Love them for what they are: fun, quirky, money-pits with lots
of personality!

Regards,
nick

[macBdog]

Great post. Glad I bought a 931.
_________________
1979 931 with a 350 chev
1973 911E with EFI

[endwrench]

[Raceboy]

Definitely, good post, all issues concerning turboing NA motor.
But being an amateur mechanic myself, I'd say that getting more power out of NA, is to install a supercharger: much less work, but in other hand they are in more expensive.
For a guys, who aren't skilled, just get faster car
_________________
'83 924 2.6 16v Turbo, 470hp
'67 911 2.4S hotrod
'90 944 S2 Cabriolet
'78 924 Carrera GT replica
'84 928 S, sold
'91 944 S2, sold
'82 924S/931 "Gulf", sold
'84 924, turbocharged, sold.
http://www.facebook.com/vemsporsche

[ideola]

[ESC944]

I did a rear mount for the 944 2.5. As long as you use the right kind of turbo, you can maintain at least 924 level performance. I talked about this in my other posts.

I will post a seperate post about this later. I also have some counter points to post on the NA conversion. But I will reserve that for later, right now I am off to the track to play with a friends 944 NA to turbo conversion.

[ideola]

OK, for further reading:

http://www.ststurbo.com/products
http://popularhotrodding.com/tech/0411phr_sts/
http://www.edmunds.com/news/autoshow/articles/103584/page011.html
http://www.supermotors.org/resources/articles/sts-a1-1.php

OK, so the dyno doesn't lie...why couldn't we come up with something like this for our cars????
_________________
erstwhile owner of just about every 924 variant ever made

[Lizard]

I think the origonal post by nick should be made a sticky and put at the top of the forum!

as for my comments, I agree 100% with you nick, and as for the faster car I am with ideola I got a 928


in regards to the comment of a rear mounted turbo, though cheaper NOT practical AT ALL for a sports car, these setups are good for tow vehicles they are laggy, and you will have to fab up a air inlet that is raised off the ground and shielded so you dont suck water as you drive through a puddle, and you will spend a small fortune in tubing the air back to the engine, you will still need the oil cooler and also the oil pump as well, I wont even consider this for my 928 as by the time you get boost in any gear that you are trying to accelerate fast in you will need to shift, and as for this setup with CIS you would have to run a pipe to the turbo from the CIS distributor (or relocate to back of car) and then another pipe to the intake manifold.
_________________
3 928s,

[ideola]

Heheh! Got it! So I shouldn't feel any shame at all about my shark, eh?!

That being the case, I second the motion to make this a sticky since it seems to be a recurring theme around here. Good work, Nick.

So the long and the short of it is that if you want a fast water-cooled Porsche, buy a 931/951 ... or even a 928!
_________________
erstwhile owner of just about every 924 variant ever made

[Raceboy]

OT: 928 have been in my shopping list for couple of years now My friend who has two 928's: '78 928 manual with '80 928S head and injection conversion (240->290hp, dynoed) and '88 928 S4 (320hp), both manuals and every time he lets me drive these dream-cars, I promise myself to by one of these things in near future. But that near future is lasted for 5 years already They are full of luxury and best daily drivers I have ever driven (Btw, I'm am kind of a journalist in local car magazine )
_________________
'83 924 2.6 16v Turbo, 470hp
'67 911 2.4S hotrod
'90 944 S2 Cabriolet
'78 924 Carrera GT replica
'84 928 S, sold
'91 944 S2, sold
'82 924S/931 "Gulf", sold
'84 924, turbocharged, sold.
http://www.facebook.com/vemsporsche

[leadfoot]

The guy that did my exhaust setup has a 928 supercharged to 450hp....it's a weapon on the road.
The one comment he made though which I thoroughly agree with is that the head gaskets are a weak point for these cars.
After having head studs put in he has had no further problems in this department. I know of a couple of people that have blown head gaskets a couple of times, lost their licences for speeding just as many too.
Leadfoot

[Eturbo924]

Nice post Nick.

My opinion. If you want decent power from your 924 it is better to get a reasonable set of higher compression pistons, port and polish your head, get a decent cam and high flow exhaust.

I have all but the pistons on mine (hope to put in my Euro pistons sooon) and as I have posted before I ran a 931 and stayed right on him from approx 70-100mph. Two things to note for those who have not seen this before.... The 931 looked in rough shape... body wise and I did not have to use 100% of my power to hold him. He was trying to loose me though. We ran a couple times with the same result. I did manage to get past him.

Oh and the 924,931,924S,944 will stay with the best of them on curvy roads.... that is not to say I condone racing on public roads. Though most of us have at one time or another.

www.geocities.com/eturbo924

Eric
_________________
1982 924
1992 968
2003 C4S
Parts Parts Parts and More parts.
E-mail me for parts you need!
Drive Fast!

[Chrenan]

[Eturbo924]

As long as the cam is not to agressive you should be fine. Let us all know how it is when it is all together.

Eric
_________________
1982 924
1992 968
2003 C4S
Parts Parts Parts and More parts.
E-mail me for parts you need!
Drive Fast!

[Chrenan]

The cam is pretty mild, Euro Race calls it their X1 cam, basically one step above the stock cam, but still appropriate for the CIS fuel setup. I'm hoping by mid-summer I will have the new motor swapped into the car...
_________________
1987 951 - M193 Version for Japan