Last week I did some quick testing of a rear mounted turbo on my S4. It's a cool looking rig--kind of a cross between a chainsaw, howitzer, and flame thrower, complete with a megaphone! I'll post a pic if I can figure out how to do that.

In my test I used a slip joint to connect the turbo pipe to my tailpipe and the entire apparatus was supported on a jack at the rear of the car. About 15ft of aluminum tubing routed the pressurized air to my front mounted MAF. I had what looked to be a really nice pump to supply oil to the turbo, but just as I was ready to fire up my engine, discovered the pump was non op. So I lashed together a quick gravity fed oiling system and of course this entailed spilling a quart or so of oil on the floor!

The engine started right up, made some new sounds, and ran a bit rough. I idled for 5 min to break in the turbo and during that time the computer became more familiar with the new environment. I did a couple part throttle runs and all seemed ok. Next an increased throttle run. Lots of things to keep track of on the dyno and I had my eyes glued to the AFR display. A quick glance at the boost display revealed a pressure above 5 psi and rapidly climbing. As I had no waste gate, I shut down prematurely.

I put my foot into it a little more on the next run and there was a loud POP. My face turned ashen white. What the...? My observers were laughing near hysterically--the turbo pipe had merely detached from the tailpipe! Tighten the heck out of the slip joint. Time for a full bore run, but only to 4500 rpm. At 4400 the pipe popped off again, but I had the info I needed.

There was plenty of boost available (5.3 psi @ 4400 rpm in this case with a much less than optimal setup) at quite low temperatures. The turbo only reached 330 deg F and the intake pipe at the MAF was the same temp as the ambient air. Both temps would have risen with sustained running. With this setup and such low rpm the turbo didn't have time to really to really be very effective, so the performance numbers were not exciting. However, the boost is available and with that will come power.

I will be installing a more permanent turbo system in my '89 S4 and shortly thereafter in my nice new (to me) '79.

Tom Cloutier

 

Barry, while I applaud your efforts, the oiling system you describe sounds risky. For one thing, Oil pressure in the shark is more typically in the 100psi range. What you have described will get you 3 bar at best. And what about flow? I imagine your oil flow will be way down too. I would suggest having two pumps; one to pick up turbo oil supply at the drain plug in the pan and pump it rearward, plus your scavenging pump back at the turbo. It should be real easy to drill the drain plug and put a fitting in it. Then, pull that plate off the block and put your Porsche oil filter back on. I don't think you really want to try making an extra 100 horsepower with half the oil pressure and some unknown fraction of the intended oil flow. JMHO.

 

Wouldn't it make more sense to have an independent oiling system set up in the back of the car?
I would think that with all those feet of oil lines, that it would only be a matter of time before
you had a leak, and lost all your oil. For both the car, and for the turbo... It seems a lot
smarter to have a small pump, small cooler, and return lines, all back in the rear of the car...

 

Everyone's doing rear-turbos now!

Where's this mystery S4 in the NW too?

I would prefer a separate oiling system, too. If an electric pump could supply sufficient oil pressure, that would be ideal, or perhaps a crank driven oil pump and an electric return. But it's not my money!

 

Barry,

If you already have all the lines run, you can use a restrictor to limit oil pressure from the block. The motor pressure is 100+ PSI, so I think this is wise..

However,

BC has a good point.. As you have a pump, just run a closed loop with an aux cooler... 1+2qt should be more than adequate...

my .02,

 

Tom,

Looks cool, but you have the coffee can in the wrong place.

 

Tom,

Good going..! Loks like an easy way to make some progress for a low Budget system...

Regards,

 

I too believe that a separate oiling circuit should be somehow explored. I understand that investment in the full system has already been put out, but hey, this is R/D.

I think this is something I want to do on the 78 just to see. I mean, even 1psi is better then none right? The good thing about the 78 is that I will have a map based system, so I can simply suck in air at the rear, push through the turbo right into the TB.

Maybe an air filter in the right rear fender area.

 

A seperate oiling system would be ideal, and very doable. Since I have to use a pump anyway, I'll most likely just eliminate the remote mount filter and run the pump and lines in the back of the car. I had thought about doing that, but you gotta start somewhere .
Setup looks nice Tom, but why did you put the MAF all the way at the rear of the car? I actually wish I was doing this on my S4, because hooking into the intake would be much easier than the AFM.
Back to the garage!
It also hurts to have an almost zero dollar budget too... But, that just means that it will be 'cost effective'

 

Thanks BJ!

The MAF is there just for the sake of the photo. It really is located up front and to my intake snorkel. Also this is just a test rig. The real thing will be further forward where the exh gases are much warmer. I am debating whether to have separate oiling and cooler or just a return pump to the engine sump. The separate system appeals to me.

Tom Cloutier

 

...wow... thats um, different! Wheres the MAF in that loop?
Do seperate oiling... It just makes sense and then you'll never have the possibility of getting turbo bits in your engine oil supply. The question is, since its a seperate oiling system and doesn't necessarily need a pump like the welden/mocal, any other alternatives? Something like an electric fuel pump, but one that can handle oil? Thats what I'm looking for...

 

Something like this?
http://www.emp-corp.com/html/product...c_oil_pump.htm

 

tom, those are some cool pics - nice work!

 

I like that intake assembly in front/top of the radiatorTom.
Is the stock filter where i think it is...Underneath out of view?
Thats almost exactly what Im goign to do with my SC intake for V2.0

 

You don't like the fender intake that you did Tony?