Almost Ready!

[Steve Hummel]

It is an addiction...I build road race cars for others in my "spare time" (I am a PhD that teaches Porsche/M-B/Bosch/etc people in Stuttgart and I am a full-time faculty guy here in Canada)...so my darling beloved motivates me to build a Porsche because it will allow my son & I to spend time together...well we know the outcome, he discovers girls and I am left with a disassembled 930...so I get the car done and in the process play with the CIS warumup regulator and the rest of the components, modifying them extensively to run at higher fuel pressures with some adjustability of the fuel curve (it is that scientist thing).

I actually ran this as a SRED project, sponsored by the federal government, because the concept of the CIS intrigued me, I felt that there was more to learn in terms of advancing knowledge and I had access to the people over there that originally designed and built it so I could get some deeper insights. Anyway, our 1977 930 test mule achieved 375whp@6,200rpm on pump gas with 1 bar of boost with stock compression when we finally got it together in 2007, after I blew the engine once playing with the fuel curve on the dyno. Having 2 doctorates and 2 masters and an engineering degree means that you are real good at making mistakes...

So I ran it the last 4 years in vintage races, refining the warmup regulator and other components, until I broke a rocker arm half way through the racing season last summer. I have an AIM data system on the car with an Innovate AFR probe so I was able to get a lot of data on what made the system work in the real world (the car is a mobile test platform with all the electronics measuring things but the CIS is pure hydraulics).

The rocker arm failure was caused by fatiguing valve springs, necessitating a major rebuild because of bent valves, so I decided to advance my knowledge further because the dyno results indicated that there was a pretty big hole in the midrange of the 3.0litre engine.

So, I ported the heads using a computer model I developed in 1988 for a cylinder head engineering firm I had back in the day and we got more air flowing through a 36mm intake port than a small block Chevrolet performance head (we are using stock 930 valves in these heads) with comparable balanced flow through the 36mm exhaust port. I had originally ported the heads to 34mm but felt that we could still get good velocity in the ports if I went to 36mm. I thought that going the Carrerra size was too big (I ran the numbers on velocity & evaporation, remember, you cannot burn a liquid) and we would get too much wet flow. We sleeved the exhaust ports because the MODE exhaust we used since day one (thanks to Bob Holcombe, smart guy, great fabrication and right dimensions) has flush mountings.




So then to improve reliability we cross-drilled the crank and replaced the modified stock rods with a set of Carrillos. We used the original Mahle pistons and barrels from the first rebuild, only having Swain coat the piston skirts and domes. We replaced all the rocker arms and put racing valve springs/retainers on the new stock valves. The oil pump was good and the car already has a Smart Racing front oil tank with a -20AN feed and -16AN return with a -16AN breather so the oiling system was good to go.

We sleeved the Carrerra intake manifold down to 35mm (some talented machinists here in Southern Ontario, Forrest & Forrest Racing in Ayr did it as well as the crossdrilling and new crank plugs) with no degradation of flow when bolted to our 36mm intake port heads. We also modified the Carrerra intake to accept the CIS injectors.




So it all bolted together and we got it in the car. I have to say that Cole's post on 934 CIS stuff motivated me to talk to the old Germans over there so since the new intake made it difficult to locate the CIS air valve in the original location I moved the unit to the passenger rear and plumbed it. up.


Along the way we decided to twin plug the heads because while we have only played with boost at 1 bar so far I want to try to measure results at 1.1 and 1.2 bar, still staying with pump fuel. Andial did the distributor for us and a local machinist did the heads (Motec).

So the plan is to fire it up on Monday. Uli Furtmair at FAST in Bridgeport will facilitate that as he has pretty deep knowledge of stock CIS systems and all the right test stuff to help me to calibrate it. Hopefully I have re-assembled the engine properly.

Other notable mods are;
- 993 brakes front & back
- early 934 tail (it really works)
- matching dive planes on front (had to put on, 934 wing generates a lot of downforce)
- Smart Racing re-valved Bilsteins with matching torsion bars (no coil springs on car)
- very light (2,250lbs ready to go), lots of aero friendly fiberglass/carbon fiber
- K27 with GT35 wheel (thanks to Brian at RarlyL8)
- MSD ignition
- Fuel Safe big cell
- Porsche rollcage, improved by Lionel at LJ chassis
- Complete Custom Wheels, 18", 3 sets, 2 dry, one wet
- lengthened front control arms
- Racer's Group sway bars with rear modified by me to have blade adjustment in cockpit
- Elephant Racing rear control arms
- solid suspension bushings everywhere
- WEVO shifter
- 930 transmission with Guard diff and short 934 rations across the board
- self designed/built aluminum flywheel with light Sachs clutch & pressure plate
- 964 cams from Webcam (thanks for great service Wendy)

I have been teaching in Germany now for 6 years and frankly have forgotten many of the "little things" that we did to the car because each time I would come back after talking to people over there and we incorporated new stuff all the time.



My goal is to crack 400whp at 1 bar with the new intake with a much better torque curve. I have driven front engine SCCA GT-1 cars pretty much my whole racing career so I am not even close to comfortable in this car yet. It is way better than my ability and is phenomenal in the rain (acceleration and braking). Once we get it tuned I will experiment with the other wastegates I built (stock Porsche, just stronger springs) to see how things work out with more boost. Anyway, any insights on build and test plan are appreciated.

My long time crew chief, Tim Snyder, has been very patient with me due to the engineering stuff but now it is time to drive it! Thank you to the many vendors and old race guys who offered their insight and guidance, any failures are clearly due to my learning curve...which is not close to being mature...

Best,

Steve

Dr. Stephen J. Hummel

[speednme1]

Cool project, interesting placement of the intake.

[IMR-Merlin]

Very nice build.

Subscribed

[Steve Hummel]

Front view, big ATL cell, oil tank on left, NASCAR breather for tank is the round aluminum looking "can", big filter beside it to protect front oil cooler, battery relocated to front passenger side (downsized to Mazda Miata size) by the fuel cell, all oil lines are -16AN in the front.


Bottom view of MODE headers, these have 4 racing seasons on them, no issues.
Closest AN line is for turbo tank vent/overflow, next AN line is oil return from turbo scavenge pump, transmission AN line for oil cooler is also visible further back as is the -20AN oil in line to the oil pump.


We had to build a vacuum/boost log to attach all the sensors and wastegate, it is an aluminum tube with a bunch of threaded holes in it for the various sensors and stuff and it is just bolted to the intake manifold.



Wastegates are all Porsche, this one is 1bar, you can see Brian's turbo and the MODE headers, turbo oil can, and wastegate exhaust pipe, looking forward to see how much faster Brian's turbo spools up.


The aluminum flywheel was carved from a billet piece, Timeserts to mount pressure plate, and replaceable wearplate ground from steel very similar to brake disc & steel flywheel material, it is really light!


Yes, it is street legal, even has a new stereo (and a Motorola race car radio). The box with the red button beside the stereo is a standard Ford G-switch, in the event of an accident it shuts off the fuel pump in the tank and the Bosch pump at the back of the car. It is a standard safety item for Trans-Am cars, Irv Hoerr sells them, it is cheap and they work. Every car I have built has one, fuel fires are not forgiving.


Here is some hard data, modified 36mm intake port versus stock 41mm Carrerra intake port and stock 32mm turbo port (shape matters) and the exhaust port.
I have the stock 3.3 turbo exhaust for reference, my modified 3.0 port, the Carrerra exhaust port, and I modeled a "W" port on the flow bench (used the head porter's most important tool, Playdoh) in an effort to get more flow at the higher lifts, it worked but the fabrication effort (TIG welding inside the port) is huge so I just stuck with my normal port shape design. All the flow was done dry although I did wet flow the final design for the intake port, it was very nice because the smaller 36mm port had nice velocity numbers.


The improvement both the intake and exhaust ports came primarily by reshaping the short side radius.

Best,

Steve

Dr. Stephen J. Hummel, P. Eng.

[RarlyL8]

Hey Steve, glad to see it all coming together! I'll be tuned in to see how she runs!

[Steve Hummel]

Thanks Brian. Finishing other cars, all the academic stuff, and a sick wife have slowed the schedule a bit but persistence is paying off.

Below are the initial dyno results from the start of this project. I have calibrated accelerometers in the car hooked to the AIM data system so verifying what a "rolling road" dyno tells me is just math and this avoids "optimistic" results. When the project started we used stock fuel pressures and a modified stock exhaust system as well as racing fuel (C-12) to avoid detonation problems. As I learned more about the Porsche motors (I am no expert) we moved to pump fuel and improved the exhaust. We went to MODE in 2008 because of the abuse that I was inflicting on the engine on the dyno and the race track. We also began to raise the system fuel pressure to improve atomization. It all worked but I did go a bit far and killed a motor by too much fuel curve "optimization". That was a bit expensive but I learned the limitations of the system components. These motors are pretty impressive, I beat the hell out of them on the dyno and the track and they were quite robust. The Porsche people put some serious thought into them as they are pretty resilient.


Now I need to learn how to drive it fast.

Best,

Steve

Dr. Stephen J. Hummel, P. Eng.

[RarlyL8]

The medium tube equal length header design works really well. I hadn't seen a set before I made mine but wasn't too surprised as convergent designs become a given with all the constraints for room on a 930 engine. Measuring events in individual cylinders can sure be a challenge due to those same design/space constraints.

[Steve Hummel]

Brian, you are absolutely right. When I figured out that I needed to improve the slightly modified stock system I found out that there were very few vendors on the market in 2008 that made a header with the tube dimensions that I wanted. You were not selling headers in 2008 (I think). I was set to build them, since I am not a good TIG welder I took them to my fabricator, the guy that built innumerable sets of V-8 racing headers for me (and my clients) and he said $5,000.

I actually thought that was a fair price because it was similar to what I had paid in the past for custom V-8 stainless steel headers and the material costs here would be a bit more due to turbo heat and mount construction. Since I was funding this project and I am half Scottish I called the German network and that is how I found Bob Holcombe and MODE. At $3,000 a set in 2008 they were 40% cheaper than building up here and they had the dimensions and quality that I wanted. After I tried them I bought a second set for a twin scroll project that I was working on and it worked well too.

Frankly, looking at the pictures of your headers you seem to have almost identical dimensions. This is great, because it is hard to beat physics so you have good science which means good results. The single biggest improvement that I made in my program was better exhaust. Since I was after higher AVERAGE horsepower across the operating range rather than highest PEAK horsepower these dimensions were pretty good.

I am looking forward to your next generation of products....

Best,

Steve

Dr. Stephen J. Hummel, P. Eng.

[RarlyL8]

Thanks Steve, appreciate the info. Actually there is a thread where the folks on this board helped me design the headers. I asked for all the negative and positive points found in the existing offerings and addressed them all. That is where the funky waste gate circuit design came from, an answer to complaints of overboosting mostly due to the "elephant nose" pipe seen on most short tube headers (a little comes from old OEM waste gates).

Interesting what you did with the intake. How much do you think it helps % wise increasing power? I've tossed around the idea of designing an intake but so far don't see where the HP/$$ would be worthy.

[cole930]

Steve:

Really nice work !!!!!! Love the car:

Cole

[Steve Hummel]

Cole, your fault I moved the CIS unit. I do not surf the net too much but I "stole" some time and saw your posts about 934 stuff and thought that hey, this guy has something going on. I was about to close down my project and just drive it and thought this might be a way to fix the "hole" in the torque curve of my 3.0l test mule. The engine works like "Jack the Bear" between 4,000 to 6,500rom but sucks below 4,000 rpm. I ran the numbers on the tuned port length of using a Carrera intake, compared it to the flat "pancake" manifold and thought that it might just work.

I wanted to stick with the CIS unit versus EFI as it has been really reliable and pretty easy to tune once I "paid the admission price" of wrecking some stuff. I like the longer runners and the large plenums at the end of each side of the Carrera intake, the volume is substantially more than the flat "pancake" manifold so I thought that increasing runners and having larger plenum volume to act as a capacitor might result not so much in more peak horsepower but a better torque curve in the midrange. This will make the car more driveable as right now it is a "point and shoot" machine. I geared the transmission for 1,700- 1,900 rpm drops between gears so the car, in normal racing without traffic problems, always stays in the best performance range.

Hopefully I can get it on the dyno within a week or so given we break it in without problems on Monday. So, no huge power increase expectations at the top end, more an effort to improve the torque in the midrange. Brian's question is a really good one, will it be worth the expense? I think the answer is only if really picks up the torque. The stock flat "pancake" manifold is a pretty good piece of equipment. Porsche's racing engines during the day were quite similar to the stock Carrera intake in terms of runner length and volume so maybe they had the same thought. I will share the results once I get it on the dyno.

Only way to find out was to spend the $ and effort then measure it...

Best,

Steve

Dr. Stephen J. Hummel, P. Eng.

[philip j]

Good to see this kind of talent north of the boarder. Hope this brings more guys out of the woodwork! subscribed. Philip

[cole930]

Steve:

Glad to have you onboard with hanging onto the old CIS. I
originally relocated mine because I had calculated something
close to 1000 ci. of space that had to be re boosted every time
the throttle was lifted. Between the pancake manifold,
recirculatuon assy, and 3.5 ft. of plumbing I thought there
might be some lag time to be saved. If it doesn't help lag time
any the Old School Cool Factor of the 934 is still worth it. Who
knows, and it keeps me out of the bars.

You've got an awsome build there and real quality work !!!!!

Cole