danglerb

The S4 does give a torque bump, but real torque, take your pick.

Boost, turbo or supercharger. $5k to $10k, comes off every two years for smog.

Stroker, $25k gets you a nice reliable motor, less gets you less.

Swap in some cubes, $12k to $25k depending on level of insanity.

Nitrous, $1k plus refills.

Torque in the raw sense is how much air does the motor pump through per revolution. Torque in the make it go sense is more like how much air does the motor pump through per mile, which includes the gearing, and without inviting long debate with gears that match the situation, max HP is max acceleration.

blown 87

That is one bad *** motor right there.

Larry Velk

For some info on this topic see:
PCA publication "UP-FIXIN der PORSCHE" Volume IX, pages 276 - 281.
Includes lobe areas, part numbers, for the most part, all SOHC stuff. Old data, but the 2 - cammers are old also. Owner had problems with the factory calibrations when using the modified cams. He chip - tuned the car supposedly due to vacuum problems.

BC

the 2V motors have enough room to go pretty big on the intake valve. Unshrouding could get into the bore wall, but hey, its fun. Jim's main point as that no matter how big you go, you have two limitations:

- Lobe size per bearing size on the shaft/case fit
- Revs - the valves will float over 7k I think. Too heavy

Plus I assume not many have looked at valve spring prices. I found a Ford Spring that worked, but had to recut the spring seats.

Jim bailey - 928 International

dangler you have arguably the best most experience 928 engine builder already working on your car. Greg has worked on more 928 engines than ANYONE I know , you mentioned seeing an Article from 20 some years ago about "hot rodding" a 928 and yes that was Greg... You have seen the car in the bubble at Greg's that is 944GTR 2 valve 4 cylinder 650 HP Trans-Am car and yes Greg has rebuilt those engines...So yes you get much conflicting " advice " , that from Greg and that from everyone else He is the only engine builder I personaly know whose engine has finished the Daytona 24 hours ... . I know for a fact that Greg has in the past refused to assemble an engine simply because he did not like the collection of parts and did not want anyone to think it was a Greg Brown engine if it failed . I may not agree with him all the time but do very much respect his opinion. besides about all you are going to get on Rennlist is abuse... And Yes I do sometimes get a bit cranky.

dr bob

That torque improvement is the result of the compression increase and maybe valve sizes.

I'm interested in the definition of the results of the 'improvement' you are looking for. Absolute max dyno ponies? Quickest accelleration 0-60 available with your existing driveline/gears? Best 70-100 passing times? 1/4-mile times? Just curious. This is the part of the calculation that should precede all others, IMO.

heinrich

John V

Bob,

I was going to comment on this earlier and decided against it. Your point seems to fall on deaf ears and I for one agree with you. One mans "improvement" is anothers gripe. It seems folks get so tied up in a number that they ignore the realities of driveability and feel. I'd much prefer a wide flat torque curve over a peaky horsepower figure of higher value. Some would disagree as to which one is the "improvement". I've alway been under the impression our engines were intended and tuned with emphasis on torque over horsepower, unlike many engine manufacturers where peak horsepower is normally higher than peak torque. The horsepower number sells, but in driviing some of these cars, the impression is less than impressive.

I remember some months ago going out on purpose to find a replacement for my 1981 928 (the least powerful version with a rather paltry 220 HP rating). I Test drove a new Nissan Z with 286 HP and was so unimpressed that I thought that car was flawed and not really making the stated hp. I went on to drive a new G35 coupe, which had 10 less HP, and was heavier.. yet it "felt" quicker than the Z, but still not as potent as my measly 25 year old 220 hp car. The difference, as far as I'm concerned, is exactly what your referring to in defining improvement with respect to cam grinds- TORQUE, generous levels over a broad RPM range- Thats what feels strong, not a peak number that exists for a breif moment in time.

I'm sure cam companies receive requests for these types of grinds but I would bet dollars to doughnuts that they receive exponentially more requests for a cam that will make that impressive Dyno number... even at the expense of over all performance.

danglerb

I'm looking to make the car as fun as I can without spending more than I can convince myself isn't ridiculous.

Its a process like picking a major in college. When I grow up I want 350 rwhp. After some study I didn't especially like any of the ways to get it, and began to question the basic merit.

Then I bought my 83 and with no point of reference didn't realize it was not running properly, extremely rough over 3500 rpm with a major drop in power. I assumed it was normal or not far from it and grossly under powered, and started working at increasing the power as much as practical.

Now its pretty much running fine, so I am narrowing my goals to barely managable traction with 245/45/16 tires on the rear in first and second. Any variation of the Euro S motor should be able to do that.

Parallel goal is just to make the car nice, fix leaks, replace parts, make the car nice.

Talking about the cam specifically, I wanted to see whats in the box and then make up my mind about which way to go. If it ended up faster than a S4, thats a cross I could bear too.

danglerb

A good street cam does NOT sacrifice low end, but a cam is hardly a panacea for torque, it takes a cam working with a resonant tuned intake and exhaust to get really good low end torque. Long tube headers make torque if done right, but the 928 driveability issue is from the first gear ratio being so low. Most fast feeling street cars shift out of first at 30 mph or less, that gets you going quickly and feels like loads of torque for part throttle.

No point in worrying over what can't be fixed.

danglerb

My point is that the US and Euro S motors feel almost exactly the same until the RPM goes up and then the US motor power drops quickly and the Euro S doesn't. Its not sacrificing the low end, its just opening up the flow so the top end doesn't die.

danglerb

Don't I know it, but he doesn't venture many opinions on the merits of what I should do. We have talked about things two or three times before I realize that while he has never said he isn't doing it, he isn't doing it.

I was going to say, can you imagine what its like to work with nothing but Porsche owners year after year, but I guess you can. Greg is totally immune to the crazy idea, or wondrous new device customers come to him with, and pretty clearly I need people to tell me the idea is crazy in plain language, sometimes.

With the hybrid motor all he has done so far have been CIS, so he told me to go ask here, see what people have to say about using the L brain etc.

I am really not worried "how" it will turn out, it should be great, I am just working on having some gas money when its done and getting the best parts I can.

mark kibort

dangler, as i said, I probably have the most experience in pushing the 4.7 in stock form, 4.7 in part euro form with the euro cams and the 5 liter part euro 2 valve, as well as the S4 5 liter.

from racing and the dyno runs performed, it looks like this:

4.7 stock US flat feeling 200rwhp and 245rwt
4.7 US with euro intake and euro cam, peppy feeling 246rwhp and 245rwt ( so no trade offs for the cams, just 45hp gained!)
5 liter part euro with bigger euro valve heads, and 5 liter displacement, powerful, fast and reliable with 290rwhp. there is no real difference in the usable torque range for a given HP . the flappy thing is only a street drving thing. (ie 3000 to 3700rpm) after that, all the porsche 928 engines perform pretty close to the same. i showed you the JV HP/torque curves. from 3700rpm on, the shape of the HP curve was the same as the S4, and there is no difference in the proportions of torque.
acceleration = Power/(mass x velocity) Its all about power produced at any particular, relative, MPH.

MK

mark kibort

oh, and by the way, all my euro mods and the 5 liters were done with the Ljet . my opinion is that if i could loose the AFM flappy, because of its size, i could have gained 10-15hp max. until we find a euro 84 LH jetronic system powering a 5 liter 85 block, we will never know!

mk

mark kibort

remember, acceleration is proportional to power. what you are saying is that you want more power down low in the rpm ranges. im sure, if you can operate a 928, with its engine design in the 4500rpm to 5500rpm, there will be no chance of accelerated wear. keep i mind what ive put the stock 928 engines through. try thinking about 2 back to back 24hours of Lemans, plus 20 years of intermittant driving, and its still running like a champ! (knock knock)

The rear end ratio doesnt mean much as has been discussed, its the overall ratio is what counts. better to look at max speeds in each gear and compare. its a short cut, as easy as using HP instead of torque to determine acceleration potential of any car at any speed.

MK