DKWalser

What is the ballpark estimate of how much it might cost to upgrade my 1990 S4 into a super car? I know it's a lot more than supercharging or even turbo charging. How much more is the quesiton.

GregBBRD

Like anything in life, totally depends on what "boxes" you check and if you do the labor or pay someone to do it. (My goal has been to engineer these pieces to the point where they can be handed to anyone has the ability to rebuild a stock engine and have them not know they are building anything different, until they turn the key.

About 15K is going to get you all of the internal engine pieces needed to build the bottom end and do the required machine work, using a Nicosil style cylinders. Slightly more, if a Alusil bore is used. (There are benefits and trade-offs both ways.) Add in an engineered header and exhaust system, with Sharktuning, and this will give some people all the power they need, especially if starting with a set of GT cams.

You can certainly go way beyond this point, with head work, intake work (or a complete new manifold), more aggressive cams, lightweight DLC coated lifters, etc, etc.

mark kibort

I still don't understand why the special pistons on the Uber GTS stroke crank . you say it can use the GTS pistons so that alone could turn an S4 into a GTS engine (GTS crank and GTS pistons with rods) But say you have an S4 and have S4 pistons, is the rod angle that dramatic so you can't use a GTS crank and special rods to make that work with stock S4 pistons? (because you would be using special rods anyway.)
and if you have to use special pistons (GB pistons) and custom rods, why not make the stroke in the 6.5 liter range to take advantage of that greater displacement? what am i missing here? is it possible to modify the stock 928 S4 pistons to cut the skirts down to make them work, or do pistons need to be unmodified from their original casting? (or are the wrist pin positions just not proper to allow for the rod angles for such a short rod)

I know this special crank is better balanced, special sized journals to have lower bearing speeds, etc...but is this solving a problem that the GTS has? i thought the only problem was the oil consumption.

GregBBRD

Pretty sure that your confusion comes from not realizing that I built many different crankshafts (and connecting rods) in many different versions....for completely different applications.

I do build a direct replacement GTS 85.9mm stroke crankshaft and connecting rods, for anyone that needs a superior replacement crankshaft. Lighter, stronger, stiffer, better oiling, better rod bearing selection, stronger rods, etc.

I also build a different crankshaft (and matching connecting rod) for high performance street use. This combination utilizes either a modified 968 piston for Alusil bores or one of my custom pistons in a Nicosil bore. This combination is designed for slightly higher rpm use than stock (7200 rpms.)

Finally, I build a brand new very light crankshaft (and matching connecting rod) for very high performance street use and racing use. This is designed for a special custom lightweight piston, for use at even higher rpms than the above combination.

I could certainly build a connecting rod that would allow the use of an S4 piston with this crankshaft, however the resulting connecting rod would be very short. Worth noting....no one has ever asked for one of these rods, except you....and I seriously doubt you will ever need or use one....so this is a very moot point.

Since the stock GTS and S4 pistons are extremely heavy, they work fine for stock applications, but certainly are not very desirable beyond their stock application.

I answered your question regarding why I'm going "down this current path" and not using the 95.25mm crankshaft, in detail, in post #42. I do not think I can answer that question any better than what I already posted, so if you read that post and didn't understand the logic, I appologise, but I'm not going to try and explain it any more than what I already have done.

Hope this helps with your confusion. Try and remember that I'm never "stuck in one rut", but always moving forward to try and build better pieces for different applications.

ptuomov

Nice crankshafts, good to see this project moving forward.

I think that the 928 S4 rotating assembly is very strong and great for relatively low rpms. (I don't have anything good to say about that of the GTS...) We're pushing it very hard in terms of gas pressures with the turbo cars, and it just keeps holding. What makes the 928 rotating assembly super reliable at 6000 rpm is also its weakness at say 8000 rpm: It's very heavy. So it makes sense that if someone wants to go to 8000 rpm, a lighter rotating assembly is needed.

8000 rpm is not a problem from engine breathing perspective now that we have ITB options to replace the stock S4 intake, again which is great at 5000 rpm but "sucks hairy *******" at 7000 rpm.

mark kibort

thanks Greg.. that makes it clearer, but still a little confused on the goal. maybe you can help me understand.


so you are saying you are not going the displacement direction because it provides such torque that one customer "rob" spun his large rear tire clad GTS at low RPM? that seems a little strange, as i have been running the 6.5 liter with all sorts of tires on the street for many years and with 420 ft-lbs of torque, i never even come close to seeing wheel spin, unless im in 1st gear .
also, with the GTS or any other 928, you get max torque at about 4000rpm. sure, we can get wheel spin in 1st.. but you need to floor the car... in 2nd, at 4000rpm you also need to be WOT, and in 3rd and beyond, there is not enough torque to provide spin unless you are in the rain

by taking away displacement and going back to GTS specs and making things lighter, that doesnt in itself, provide more power. 5-10lbs off a crank , as far as power goes, doesnt do very much, but sure, reving your engine for downshifts or reving the engine at a stoplight to impress friends, sure, its much better. on the dyno though, and as dynos measure HP, its over a time period. after 1st gear the rate of RPM is relatively slow, so 5lbs off a flywheel, crank , etc, doesnt buy that much in terms of HP. (something like 20hp in 1st gear, 10hp in 2nd gear, 5hp in 3rd gear 1.5hp in 4th gear.....etc)

I understand by using your speical light pistons, and smaller journaled crank you then have less bearing speeds and less forces on the bearings at high RPM and better oiling... but if you are going to use this masterpiece of a crank design, its really to get more hp at higher RPM. if you dont change anything on the intake, how is that possible engines dont make a lot more power just by having lighter components alone.


ok my question regarding your desire to "move forward" are you going to address the 928 age old question of are we ever going to have a good NA intake that brings the 928 intake system into the 21st century , where it is common place for the crappy MUSTANGS and Aston Martins 4.3 liter or 5 liters to make over 450rwhp with very little modifications? it seems to be most all intake system related.... and yes, they are twisting up to near 8krpm now and have designed their wet sump systems to survive high g loading and high rpm both.

so the question becomes do we need this racing crank, if we dont have the motor top end to support any more power at the higher RPM? after all, in looking at the HP torque curves of say, mark A's motor, it didnt make much more sense to drive the RPM above 7000rpm . even with the new intake, it didnt seem like going higher than 7200rpm was going to pay much in dividends.

It would be nice to see a S4 intake that bolted on stock, GTS and 6.5 liter engines that gave the kind of gains we saw in marks car, going from 420rwhp to 520rwhp with very little tweaking of the stock ECU components and fuel maps.

also, i do think when folks are evaluating their options, if you had the ability to use this crank or your own version of the GTS crank, to make any S4 into a GTS by even using the same pistons , it would be attractive. suddenly each rebuld could be a GTS conversion with only the cost of crank and rods. sure the GTS and more so , the S4 pistons are heavy, but again, the power band of these engines makes use of the heavier components quite well, in that they would rarely see RPM over 6400-6600rpm ..... especially, if this is designed for street use as you say. this even makes their marketability even greater. the other two cranks 6.5 liter and the light weight racing 5.4 to 5.8 liter set ups could be used for racing or just plain high quality builds as they often are in the street performance world.

Rob Edwards

Hoping to have lunch at Greg's today, will snap some more pretty pics of shiny things.

soontobered84

And I thought I was the only street punk hoonaholic on this forum.

Rob, did you realize the exact second you became a street punk hoonaholic? I have a pretty good idea when it happened for you. (and it was during this thread)

Jeez, I hope we can back to talking exclusively about new cranks.

Rob Edwards

I'm pretty sure it was the day I drove the stroker home from Greg's (May 12, 2010), and kept almost clipping the left rear bumpers of people I was passing, who were going too damned slow! I'm a nice guy, really I am. It is difficult to not become _that_ ******* Porsche driver in this car. Then it was a better clutch, then headers, then oil control, then Alpha N, then the uber intake.

I can stop at any time. Really, I can.

On topic, sorta: Managed to escape from Greg's with the new Zombie crank in tow. (More) Pictures at 11.

Rob Edwards

Kibort doesn't have a cat like this.


Squirrel!



Nice curves:

hacker-pschorr

I sure don't want to see the video of that cat doing what cats do.....knocking that crank off the counter onto the floor

the flyin' scotsman

Thats a beautiful piece Rob.

Can we see the other components before the disappear inside the block, pls?

worf928

Exactly my first thought also.

And Greg, do add Kibort to you ignore list. It's all upside.

Rob Edwards

Sure!

DKWalser

Rob -- Thanks for the pictures! Those are pretty pieces. They prompt two additional comments:

1. That's an unbelieavably nice garage floor! At least, I'm assuming it's your garage floor 'cause my wife would kill me if I were to put engine parts (no matter how beautiful or clean) on her marble counter top.
2. The connecting rods look really nice, but's what with Greg's logo? I thought we were all in agreement that 928 parts should not advertise who made them.

Seriously, this looks like you'll be building a very nice engine. I'm saving my $$ and hope to be able to do something similar in a few years.