Great work John. Cant wait for my ride. Booked up this weekend, but should be able to come down and see the beast in person next weekend. Hopefully in time for some cooler weather to see what she can really do. What injectors are you using at this point, and is the F/A plots available for our viewing pleasure as well? I assume you had the Sharktuner strapped on for datalogging... did you get any detonation pings on the counter?

Congratulations!
Hans

Let me know when you want to stop down.

The injectors are 42 lb Ford Units (disc style). I didn't plot the A/F ratio...it has a tiny lean spot at 3800 that I need to go in and snip out and also on tip in I have to add some fuel with the accelleration settings...minor changes really.

We picked up 3 or 4 knocks on the high load pulls...I snipped the timing back a bit in these areas and that knocked it out. Ignition tuning is so very important to engine longevity in a case like this.

Without the Shark Tuner, this project would have been a lot more difficult. Not impossible, but very difficult. Remember these compressors make a lot of boost mid range which is why my torque is so high. Add torque means added HP and added fun!!! If you choose to not shave ignition out in this area you are setting yourself up for disaster.

Special thanks to John Speake for the Shark Tuner and lending of his time along the way to discuss the options with me. John gave willingly of his time...twice in person when I was in the UK and many times over the phone with all the learning curves, etc.

Just wanted to add to this post about Dyno Pull Protocol

My dyno pulls were done using the standard protocol which is to lock the car in a mid range gear and pull from a low RPM up to maximum engine speed in one gear. The above high HP pull was made in 4th gear. You always try to pick the gear that is closest to 1:1 ratio to take the effects of the transmission (torque multiplication) out of the equation. 5th is not an option as it exceeds 190 MPH which is beyond the dyno's speed limits. Remember, the inertial type dyno measures the time it takes to spin up a drum...from here HP is derived and torque is calculated.

All engine speed (RPM) data on the sheets comes directly from a tachometer signal hooked up to the car's ignition, not through calibration to the roller speed by data entry from the dyno operator. This assures the pull was made in one gear and the RPM trace is straight off of the plug pulse of the ignition.

The pulls were made using the industry accepted protocol for measuring RWHP and RW Torque on a chassis dyno. One should always inquire about the testing protocol before making a purchase decision. Make sure you know what you are reviewing and always ask youself "does this make sense"? :D

Holy Cow !

I'm contemplating "freshening-up" this engine through the winter and then really cranking the screws down on it. All of the hardware is good well past 700 HP...I'm only 2/3 up the compressor maps. Just lowering the compression would allow more ignition to be used...so I could increae the power on the same boost...or on the flip side leave ignition where it is an add another 4-5 psig on the motor...I think I like option 2 better :)

if you do get into freshening the motor, don't forget to O-ring the heads while you're there?

maybe MLS head gaskets and a set of 968 valves, too??

I've got my Euro heads at the machine shop for a good going over---port and polish, 5 angle valve grind, clean the bowls up, head/block surface milling (just enough to clean it up), O-ring (for blower application), and possibly bigger/lighter valves with a fresh set of springs.

Combined with a Devek grind set of cams and light weight cam buckets, that should really wake up the top end of my motor......;)

Then again John, you could just leave it alone and see how long it stays together as is........as if there's any doubt it'll run forever the way it is now.:D

I actually have a set of 84 heads that are o-ringed. I'm not a big fan of specialized head gaskets...like copper or laminar aftermarket units. I'm of the opinion that a gasket will tank because of detonation. Certainly o-ringing the heads locks the gasket into place so it can withstand the abuse of some detonation without checking out. I've seen too many poeple use copper units or laminar units and end up with coolant leaks. Honestly I have never blown a head gasket on a turbocharged 928 and that is on all 4 cars I've built. A stock gasket is a pretty good joint assuming the surfaces are flat and it is torqued down.

One way to open things up would be with a new intake manifold...look at the stock power curve and you can see what I mean. Something with minimal bends but still having decent runner length to make the midrange torque required by a turbo junkie.

If I was running boost a box with short fat runners and an intercooler would be my choice.

Or something dual plenum with bigger runners like Mark A uses.

There are many ways to skin a cat. I had an idea for a criss-cross style manifold with dual inlets. One still has to meter the air somewhere before entry into the engine. For the twin turbo system I am not a big fan of going air to liquid...I already have to have two pumps in the system for the turbo oil and water systems...and air to air coolers just require no fussing with and at speed are typically higher in efficiency than air to liquid. For some, cutting open the bumper cover is not an option, but I think when tastefully done it is fine.

The engine bay in the 928 does not leave you with a lot of opportunity unless you want to have some form of a custom hood to clear what is optimal.

Just fitting the air cleaners in my car took a couple hundred hours of planning and labor to figure out. Many patterns and molds were hand built to make this a success. It is unfortunate, but there is no such thing as free space under the hood of a 928. I'm convinced this is one of the most, if not the most difficult engine bay to twin turbo within. If I was building a race car this package would look very different, but I placed aesthetics very high on my list of requirements for this specific system.

Why Twin Turbos and not a big front mounted single?

I'm often asked why I chose to go with twin turbos in the 928 instead of one big single turbo. There are many reasons for this...the following are some of those reasons:

1. Packaging...the twins allow for placement of the turbos right off the manifolds for max exhuast energy. Additionally the twins allow for the intake air paths to be as large as possible. With a front mounted single turbo, one would have to mount the air cleaner somewhere remotely and be stuck with say, a 2.75" inlet for all engine airflow. Placing one turbo in front of the timing belt cover was not a good idea because of the heat it would place on the timing belt and associated covers up there. If you run a crossover pipe from one cylinder bank to the other, the heat loss in that pipe can be sizeable...additionally any long crossover pipe will experience severe thermal expansion issues, so an expansion joint is always necessary.

2. Spool Time...Two turbos can cut down on spool time as compared to one larger turbo. This allows for excellent turbo response.

3. Heat input...two turbos essentially "split" the heat input as compared to one larger unit. The thermal exhaust energy is effectivley split, thus halving it as compared to what you have with one turbo. This is important if you plan on placing the turbos in the 928's engine bay. This gets back to "where would one place one large turbo if you plan on keeping it in the engine bay"? The rear mounted system is an entirely different animal altogether...I'm not making my comparisons here to a rear mounted system.

4. Air Filtration...Two medium turbos allow for two medium sized filters to be fitted into the engine bay. This keeps the filters out of harms way and allows for easy maintenance.

5. Intercooling...I wanted the simplicity of air to air intercooling for the 928...the twins allow me to route the plumbing to two side mounted heat exchangers which do not impede the radiator airflow.

6. Aesthetics...With the 928's factory attention to aesthetics I wanted something that enhanced the design philisophy Porsche had when they designed the car. I believe the twin turbo system to be one of the nicest ways to augment the design of this vehicle.

There are a few more reasons, but the above are the big ones.

Ask yourself...how would you fit this one into the 928's engine bay
http://forums.pelicanparts.com/support/smileys/wat3.gif

http://forums.pelicanparts.com/uploa...1191177376.jpg

Awesome. Thank you for sharing the information. Keep up the good work. If I ever get by your part of the world, I'd love to meet you and see your set up.

Diverdan

Any time, anybody is always welcome to see the car in person.

The TT is on tap at RL.

I heard about that...I actually thought Hans would put something up over here. I loved his first response when I dropped the hammer "Holy ****, now THAT's responsive" he said. I swear I saw him reach for the door handle a few times :)

People will have to come here if they want to ask me any questions. I made a promise to myself last year when I came here and I'm sticking to that promise.

Its lies, all lies.... ;) Seriously though, that car has some scary power to it. More than one time when john was driving, i wish he installed the fuse box lid so i had somewhere to brace myself against.

John, maybe you need to install an "Oh $h!t" handle in the TT. ;)

I had him put on his "depends" before we left :) The fuse box lid goes back in when I'm done tuning the car...my girlfriend doesn't complain about the fact that the ECUs are still on the floor ;)

I'm toying with the idea of pulling it out of the chassis next month, dropping the CR to about 8.5:1 and CRANKING down on those little screws. There is lotsa fueling left to be opened up upstairs ;)

How does 700 flywheel HP strike you guys?

There seems to be a lot of fuss over boosted 928 dyno sheet comparisons in the last 2 days. I would strongly caution people to make sure you ask exactly how the dyno tests were run before you jump to conclusions on the results.

Standard protocol is to lock the car into one gear as close to 1:1 ratio as possible and then do the pull while remaining in that gear...this takes the gear multiplication out of the picture totally and you are left with a rear wheel number (with driveline frictional loss), but not including the multiplication effect of the gear ratios...or at least it is kept to a minimum.

It's a well known fact that twin-screw (positive-displacement) superchargers trump the torque of any other form of forced induction system off idle and down low, say to about 3000 RPM...(thus the reason they are nice for off-idle and stoplight to stoplight bursts). This is the point at which a turbocharged car typically will start to out-torque a twin-screw car (assuming you fed the hampster(s) properly that day :)). Centrifugals rarely if ever match the off idle torque of the twin-screws (remember centrifugals build boost exponentially...whereas the screw super hammers the boost on hard as soon as the throttle is cracked...usually the boost is more of a plateau than a curve on a TS pump). Turbos roll on boost hard at say 3000 rpm and then hold that boost flat until redline. Centrifugal boost curve is exponential...if you are set for 10 psig at 6K rpm you will have roughly the square-root of that psig at 1/2 the rpm....in this case 3psi. At that point the twin screw pump will for sure be on "full song" (10 psig in this example) and the turbos will be ramping on pretty solidly assuming they were sized properly for the application and the car is loaded up.

Consider that the three forms of forced induction all have boost curves which are very different...all other factors equal and neglecting the energy required to turn the various forms of compressors (turbo pulls the least out of the motor to drive itself), the torque curve shape will follow the shape of the boost curve. It's a function of BMEP inside the combustion chamber, pure and simple. Torque multiplied by speed gives power...you can't have HP without torque AND shaft speed. By definition power is a rate of doing work and for shaft power one has to consider the torque and speed to arrive at the resultant power.

Again, I caution people when making these comparisons...you have to know how the tests were run before you make assumptions and comparisons. The protocol used for my pulls are listed in this thread and are "standard practice" for the industry.

Never assume and always ask questions.

So your planning on running it on an engine dyno?