Bulvot

Note: The injectors that I listed below did not work. It turns out that one or more of them were bad. Read my follow up post in this thread from 9/13/2019 for more details.

I just finished installing Siemens Deka IV 60# Injectors in my 1987 928 S4. They are the long style with EV1 connectors. I paid $$319.99 for eight of them from here:

https://treperformance.com/i-2061903...jectors-8.html

They each come with the right size o-ring for the top that goes into the fuel rail, but the bottom o-ring is too small for the hole in the intake. I purchased larger o-rings from 928sRUs.com. They have the right size o-rings readily available for a good price.

With the right lower o-rings installed, they fit perfectly and plugged right into the existing fuel injector wiring harness. No leaks at all and fired right up the first time after purging the air.

To make them work with the car, I used the SharkTuner to set the injector size to 56.6 with an injector opening time of 1.14. I left all other injector settings alone.

I have to give credit to Colin (Lizard928). He provided the SharkTuner parameters for the injectors. I did spend some time adjusting the settings to see what worked best, but the settings that he provided were spot on. Obviously, you should do additional tuning of the fuel maps once the bigger injectors are installed, but the above settings save a lot of time in getting things setup properly.

ptuomov

What's the plan for the engine? I am guessing something interesting as most engines don't need eight 60 lbs/h injectors...

Bulvot

Mid mount turbo. 12psi. Liquid to air intercooler.

Chris Lockhart

Good luck brother! Boost is a wonderful thing!!

ptuomov

Good luck. These cars respond to manifold pressure well.

How about this video?

ptuomov

By the way, Jim Corenman has a clever algorithm to estimate the injector offset. We tweaked the algorithm a little bit based on the MAF signal data and that's how we ended up calibrating the big injectors in my car.

Bulvot

So...what's the algorithm?

Fun video. Was that Colin? That thing is LOUD.

ptuomov

Jim should chime in. He's got a write-up on it.

Does your '87 have piston oil squirters?

Bulvot

To the best of my knowledge, no.

soontobered84

No, that's Shawn Hamilton's car. (Popo). Shawn built his own turbo set up. He has previously owned a supercharged GT. (namely one of DR's supercharged GTs) and several other 928s.
And that's John Kuhn in the car during the dyno pull. Herr Kuhn is well known in the 928 turbo world for twin-turbo beasts.

ptuomov

Then your engine is very much the same as the first that we run in the car. We threw everything at it, including forcing the wastegates completely shut and letting it make 750 lbf-ft of torque while knocking at the old compressor mass flow limits. The engine survived everything, including very high boost and maxed out compressors. We pulled it out somewhat frustrated by our inability to break it in an interesting way. We haven't opened it up yet, but it'll be interesting to see what's the shape of the ring lands and ring grooves. For all I know, they might look like new -- but that's to be seen.

The '87 S4 engine is basically the ideal starting point for a turbo conversion 928 project. The piston oil squirters might help further to control the piston temperatures, so maybe the early '87 S4 squirter block would be the ultimate stock engine to turbocharge.

Bulvot

That's very encouraging to hear. Do you know what psi your maxed out at? I won't be doing anything nearly as intense as your setup, which is really impressive. In my mind, what I'm doing is pretty mild. As long as I don't do something stupid, I have high hopes for it running well and lasting a long time.

I thought that the video might have been Colin because it's mid-mount and a water cooled Comp turbo, which is what Colin recommended to me. I spoke to John Kuhn a little and he's given me some good things to consider. I bought the SuperMAF from him with lips ground into the ends.

Fun to see John Kuhn and Shawn Hamilton dyno-ing the car. Thanks for sharing the video.

If you have any suggestions on things to consider or watch out for, I would welcome the input.

ptuomov

You can take a look at the now-locked twin turbo thread to see all the mistakes I've made.

I'd say that if you can fuel it with a single Bosch 044 pump for your horsepower goal, then it's going to be easier. What you want is a strainer in the tank with bigger outlet feeding the 044. Then, you want sufficient damping in the fuel rails. I've got two 951 dampers in the front and the stock damper and regulator in the back. You want to verify that the fuel temperature is stable and fuel pressure is rock solid. The regulator must be referenced to the manifold pressure between the throttle plate and intake valve (the same pressure that the injector is pushing against). There's a thread on how I designed the crankcase breathing system, there the most important thing is to vent out of the rear of the engine under braking and out of the front of the engine under acceleration. Getting the exhaust to be both quiet and low restriction took a lot of time and money. Be on the lookout for the point at which the Bosch MAF hotwire system runs out of range and flatlines, you need a whole new MAF to go beyond that power level in a turbo system. If you can stay in the region where super MAF compresses the signal while he sensor itself is still within range, you'll save a bunch. Retaining the flappy valve system as operational will help the turbo to spool, so keep that. If you add plenum spacers to both sides, you can bring the first torque peak to lower rpm with may also help with spool, you want that peak where it helps you spool the turbo.

Other than that, I'd say that you should think long and hard before replacing any stock components with aftermarket "performance" components. The stock components are almost always better. The original stock components are also often better than the currently available OEM replacements.

Bulvot

Thank you. That is very helpful. I am hoping for 625 at the crank, but anywhere north of 550 would be acceptable. I plan to tune for smooth throttle response and a margin of safety. Definitely not going for the ragged edge.

I will look up your crankcase venting thread. That is one item that I haven't yet finalized.

GregBBRD

When the 944 GTR's started making over 475hp, they found that two smaller injectors worked much better than one giant one. Can a modern 60 pound injector deliver fuel in tiny amounts (idle/low speeds) and be happy?