Bill Ball

If you can put Jim inside the kit somehow, this would work very well. I'm not exaggerating Jim's importance to the result. It's just true. We spent more time cleaning than most people would spend on the whole build. We spent more time measuring, remeasuring and calculating, again, more than most people would spend on the whole build. We spent more time reviewing the various approaches to establishing the correct bearing clearances and even just selecting the target clearance range than.... Dennis and Jim performed flow tests of the oil system and tweaked a few points in the oil galley. We fussed over the cam installation for a couple of days. Then there was the tuning and Jim's approach which I could only observe. Oh, I helped him make sure a few spreadsheet formulas were correct, but that's about it. The list goes on. A lot of this would be quicker the next time, but you would need somebody like Jim with excellent engine dynamics knowledge and a compulsive attention to detail. I'm sure there are many experienced engine builders who could get it done right. But I think for Jim to feel good about this, there would have to be a lot of time put into some accompanying instructions.

Speculating on what part contributed what to the final result is a fun sport. Mark, I hope you're having fun. Trying to figure out what might happen if you just installed certain parts in place of others to try to develop a bargain kit and what the results might be is a fun sport. If Jim did this, I might trust it.

OK, so being practical, I'm not saying Jim needs to install this for it to work right, but a kit would have to be more than a parts list and a few torque values.

RyanPerrella

Bill,

Could his map for this engine not be used as a starting point though?

It sounds like he solved some very tricky questions with his tuning. Would those questions not be the same for most anyone else tuning the car to get the same or similiar results? Could this map not be used as a starting point.

It sounds like you guys played with flappy opening and closing as well. (At least i thought i read that) Thats some stuff that i dont think anyone else has played with have they? That is very cool, it sounds like NO STONE WAS LEFT UNTURNED!

Great Results

Kibort, you havent accounted for the exhaust anywhere in your predictive percentage gains. I believe Dennis's car had the bevek headers, x-pipe and full 2.5" exhaust. Surely thats where allot of the gains are no? Not all but quite a bit.

What do you suppose this car would make with just stock GT cams? I am imagining the price on used S3 cams just went through the roof. But it also sounds like the modifications that need to be made cost about $1000. Which now gets you right back to GT cam prices.

the flyin' scotsman

Thanks Bill................realise the effort that went into the project.

Jim Morton

Ryan:

Let me make a comment the best I can without getting sucked into this "estimation" debate...

I would suggest that anyone taking on a engine development where you are incleasing the breathing of the engine to model (estimate) the airflow. Knowing the CFM at various valve lifts, manifolding on and off pays off bigtime when it come to tuning. Using the airflow, lift and RPM, you can look at injector sizing.

If the engine is using the basically stock castings for the intake, I think the base maps in Sharktuner are a decent starting place for the LH map. Also, Sharktuner allows for the selection of several different commonly used injector sizes, as well as permits custom selection of Lbs per hr for te injector. I would recommend downloading John Speake's Sharktuner manual to learn more.

As a datapoint, Dennis' engine made just under 350 with the base ST LH map for 24 # injectors and did so within safe ranges of AFR. Please note that I would not want someone to take the above statement as fact, but if starting out with a base LH map and a good WBO2, using the base Sharktuner maps should get the engine running. From there you can monitor the AFR's while tuning and be stay safe.

Bill Ball

My experience says no. I have seen several attempts to run maps from one car in another "identical" configuration just not work at all. They are so far off, you might as well start clean. We are currently facing that issue in George Suennen's car.

It appears that a big variable is MAF calibration. For example, we found that Dennis's MAF and my MAF in Dennis's car produced totally different MAF voltages. So, a kit including a tuned chip MIGHT be possible if the kit included a calibrated MAF of KNOWN calibration, but even then I am doubtful.

The flappy setting and the injector changeover to every other rev firing are adjustable with the Sharktuner. We got better results holding the flappy open all the way to redline. I don't remember if we fiddled with the injector changeover.

RyanPerrella

Jim sounds like a great idea to read the manual on the sharktuner.

I also have th Bosch fuel injection handbook which ive had for about 8 years and never read more then a couple pages. Considering that gains to be had by optimizing these systems i think its time i cracked that thing open!

mark kibort

Actually I did . Both my S4 motor with GT like cams and the Rons GT was the starting point. Both had nice headers and wide open exhausts. I think there is some concensus that the dual 2.5 with x pipe is near the same as the straight 3.5" pipe out of the headers give or take a few.

I think what the boys have done is good work. (great work) and could be used as a starting point now. however, to Bill's point, he is seeing different MAF voltages for different MAFs, so that is a serious issue. as it stands now, I would bet that one more time on the dyno could see 98% of the potential gains of my engine because of the cooperativeness of my MAF in keeping the fuel ratio curve a flat line to redline. (under WOT only, as who knows what it is like at part throttle,yet it does drive on the street very very smooth and as good as it was when it was all stock)

On the holbert machine, it dynoed at a consistant 335rwhp /335rwt actual and SAE that one day with little tuning (a half of a turn on the new fuel regulator) tail pipe readings were in the 13:1 range going fat up top. I was using stock 19lb injectors with the fuel pressure turned way up to 71psi. Dennis sounds like he has done all of this with 24lb injectors at near stock fuel pressures. Is that right???

Fuel ratios are important. I have a friend with the 6.5 liter that was able to tune it from 380rwhp to 420rwhp just with optimizing fuel. (no spark) with the shark tuner. Im trying to find out what the ratios were to start to see where the changes really came from. I have to imagine that the cams are a big part of this. Even though there was painstaking effort in doing every little thing right. I bet there are great gains for the average performace seeking 928 owner, in just a cam mod with a fuel regulator and the 24lb injectors (stock '85s). Remember, after all the debate, took my cams after setting them where I had found them originally, and moved them by 6 degrees to retard side. The result was the HP didnt see much change and the torque max went down by 20ft-lbs. As much work as Dennis and team did, hard to imagine that there could be even more things they could have done. cam setting changes with all the different fuel and spark combinations point to endless possiblities to find that last 2-3%.

Yes, it is fun to guesstimate. The main thing we have found is that the 5 liter S4 has a lot of untapped potential.

mk

hacker-pschorr

So what you are trying to say is, as long as you have the air / fuel optimized, any gains from ignition timing will be minimal (2-3%)?

Dennis K

I'm pretty sure other folks have played with it as it's easy to do w/ Sharktuner. It did result in some of our most dramatic graphs. Here we played w/ advancing the flappy opening 400 rpm and delaying 400 rpm. It turns out the stock setting for opening rpm still works pretty well even with this particular set of mods.







I agree with this. I also believe there is more available.

IcemanG17

I wonder what the limit for a 5.0L NA motor is.....I would say for a smog legal, 91 octane motor with good street driving ability....Dennis's motor is about it....of course pure race engines with far higher CR on race gas and crappy idles & big cams are a different story..... But typically you have to rev higher to get more power...which increases the oiling problems inherent in the 928 engine design...

With Dennis's engine making about 77whp/L thats comparable with pure race strokers like Andersons and Tim Dey around 79-81whp/L Of course the king is Louie at almost 90whp/L...... But that took a better intake and new ECU.... Using Louies output as a guide...in theory about 440whp is possible...maybe more in a pure race setup...450whp?

FBIII

There must be quite a bit more available. This engine has stock porting, stock valve sizes and a stock intake manifold. Has anyone tried extrudehoning to try and balance the intakes manifolds uneven flow issues, or tried an 85-86 manifold?

hacker-pschorr

Just to put things into perspective, my friend has a 2003 ZO6 Corvette track car. Only mods are the intake (before the manifold) headers with free flowing exhaust and a dyno tune to make the most of these upgrades. His power is right around 380rwhp. This is also a 5.7 liter motor!

IMO the stock intake manifold is still a big limiting factor for these cars. I know there are a few people working on a bolt on replacement that will correct some issues with our stock intake.

Jim Morton

FBIII:

I have a 6.1 liter engine in the works. Heads are completely reworked with custom valves, reworked ports as well as reshaping parts of the combustion chamber to improve "squish" area. I have been approaching this engine not as a 928 engine, but as a 4V engine, using performance objectives as would compare to all manufacturers. I can't say that the project is for any real purpose other than fun, so things move quite slowly as being a family guy it's not like I can dump all sorts of $$$ all at once.

Right now the basic heads, pisont and rods have been completed. Some good flow bench work has been done on the heads with and without manifolding. The next step is deciding how to best handle the intake flow problems as well as matching cam profiles / timing to what's been modelled for flow. I am narrowing my next move decisions pretty quickly after tuning Dennis' engine. However, the $$$ and lead times associated with some of the parts makes me very cautious as I proceed.

As a related fun fact, I recently restored my Deckel CNC tool and die milling machine to operational status. With this, I plan on completing a few trinkets for the 928 for both the 6.1 intake setup as well my new GTS suspension. It should be a fun winter !

soupcan

It's awesome to see enthusiasts doing what the factory should have done 20+ years ago. Imagine what the 928 could have been if Porsche would have just raced the damn thing.

mark kibort

I think the big gainer will be in the obvious. Any of the cars ive mentioned before, including the Z06, have very efficient intake manifolds. Ours is crap. great for what it was designed to do, but crap for big power. Our 5 liter could possibly run near what Dennis is seeing for just the cams and a crude direct flow intake, even if it was ported to a single TB and stock MAF. I hope someone bolts something that is inbetween the Loiue Ott ITB and the stock manifold. Something made from aluminum tubing, that has big plenums joined at the front or rear using the stock MAF would be ideal.