Lizard928

I've done 2 mid mount turbo setups (only possible on a 5 speed), and 1 rear mount turbo setup.
They are an absolute blast.

The rear mount I did produced 450rw ft lbs and 370rwhp @ 5psi.
Mine with 5.8psi put down over 410/410rw but I have massive cams. The third I will be getting onto the dyno soon and be getting some numbers.

MjRocket

Colin

Those are impressive numbers no doubt, but im curious as to why it seems we must run such low boost pressures? By this I mean most of the mustangs, subbies and assorted ricers around here seem to run boosts ranging in the 15's to 20's on little 4 bangers. Not that I would ever wanna run such high boost in my 928, but out of pure curiosity is there a reason why some don't/can't?

ptuomov

Suppose that you have a turbo system with a good intercooler. On '87 S4 that has 9.4:1 compression from the factory, you can tune it to run well at 10 psi up to 5000 rpm. After 5000 rpm, you can linearly increase the boost by about 1 psi per each 200 rpms. Because the cams are so small, running 20 psi at 7000 rpm is about as knock prone as 10 psi at 5000 rpm, provided that the intercooler has capacity. The torque curve will stay about flat at 650 rw ft-lbs until you run out of turbos.

killav

1. Cost.

2. See above. You up the boost, so you get bigger injectors for more fuel, then your Maf won't work (meter) all that boost, so a Super Maf is in order. Might as well get an electronic boost controller. That air is awfully hot now, might need an intercooler, which all low PSI kits I have seen do not come with, so now all the charge piping needs to change, and on and on and on....Making a competitively priced kit to boost a 928 is a losing proposition. The vendors just don't sell enough of them. There is maybe 4 or 5 places to get a "kit" and get boosted all vying for maybe 20 or 30 in sales a year.

3. Simplicity. The average Joe needs to be able to buy it, put it on , and it work without blowing up or having tons of fitment issues. Low boost kits fit that bill. 20 PSI kits, although possible, do not.

I run 10 PSI now. I added meth injection, which didn't come with the kit, to make absolutely sure I kept detonation at bay. I added a blow off valve, which also didn't come with the low PSI kit. I added a couple of open type mufflers, cause it was just to loud for me. I added a turbosmart manual boost controller. I added a toggle switch so that I could toggle between three different ignition maps. Basically, I took the stock low PSI kit, and made it a 10 PSI kit on my own which was a lot of fun.

10 PSI on a well running 5 liter engine should make at least 500 hp at the crank. For me, this was enough. In my opinion, running lots of boost through the stock manifold has diminishing returns anyway.

Lizard928

I ran the low boost to start and for reducing the need for an IC.
Once you up the boost, you need to cool the charge temp etc.

The latest car I've done is an 82 running MS. Low boost is 9psi, high boost setting is 17 psi.....

Abby Normal

I guess you could call my set up somewhat of a hybrid, using the original mid-mount location and then the Kuhn intecooler and intake box. John Kuhn redesigned the entire charge side of the syatem using his Twin Bell charge coolers.

At 11psi it made 454RWHP/490RWTQ. The dynograph shows above 400ftlbs from 3000-5900rpm.

So much more potential in my low compression motor but I need to scrap the fuel system to do so. I'd love to run 18-20psi.

Don Carter

We have a couple of Mark Robinson mid mount turbos in Houston, the most recent was "finished" just a few months ago. I say "finished" because I don't think it's completely sorted/tuned yet. Anyway, you might want to contact him directly on the Pelican forum to check availability.

Lizard928

All I can say when it comes to boosting your 928 is that you really need to have it properly tuned once it is done to ensure reliability.

I don't produce "kits" as I cannot guarentee the outcome on a vehicle.

However I will turbocharge anyone's 928, just bring it to me. I will go over what needs to be done maintenance wise etc. in order to get you a car that is as reliable as stock. But a complete blast to drive!