BC

I think the problems in some of these discussions is that numbers like IAT and Exhaust temps are not given or simply not known.

I would much rather have 10psi with cooler air and less power below say, 3k, then a large torque table that ramps off above 5k but with 200 degree air temps entering the engine.

Herr-Kuhn

I opened that can o worms this week. My developments continue...the 4.5 twin is getting a major work over in the next few weeks. Euro cams, K-26, some new plumbing. My fabricator finishes up the new twin turbo manifolds for the 4.5/4.7 this Saturday. The K-26s are fresh like units and I have the new 38mm gates sitting on my kitchen counter.

We all heard the BS two years ago. "No way your car can make that much" I proved them wrong and guess what my car still runs really well today...even with lousy 1981 camshafts. 10,000 miles on the clock since the overhaul. 365 HP and 385 ft-lbs on 12 psig...all below 5,700 RPM on a 4.5 liter economy L-Jet motor. Make no mistake, the turbo can make some serious power if applied properly.

The S4 Twin is underway. 500 WHP not possible with the turbo...now that is really funny. How much power does it take to drive a screw compressor anyway? What, a 951 can make like 350 crank HP pretty easy with the old wedge heads. A couple of turbos, breathe on it medium level and see what you get... I have a 2.2 liter that makes 320 HP on pump fuel.

Hate to break this to you guys but Mr. Reeves Callaway did all of this in 1982-1984. He must be given the credit as No. 1. I know of only one turbo application on a 928 before Reeves' work. The work was not perfect, but given the era it was darn impressive. Contrary to popular belief there are at least 4 of these cars still out there, still running. Two in my family...the second one about to get more upgrades...a 4.7 liter beast is ready to emerge soon!

SC vs. SC...there is no doubt the twin screw wins that debate. Jim...if you were trying to stay on topic, then why knock the turbo work that has been done many moons ago? It is at least as, if not more impressive than any supercharger applications. I do think Dave's system is the way to go on the SC vs. SC spplication. But don't go knocking the turbo and making comments about what can't be done, because you simply don't know.

Bill Ball

John:

More info please. I volunteer for further testing! I'm about ready to install an intercooler and goose the boost.

MarkRobinson

Hi Marc: I'm the first (I believe) to offer kits. one-off's are done on just about everything. I dont care to take credit, just some familiarity. .

As for "can of worms" with twin turbos...I honestly have no idea what you're referring to. There's no reason for twin turbos when all your power/torque/spool can be accomplished with one.
Off to the gym! laters.

BC

Ah, John. I forgot, did you post dyno charts? Can you post them here so we can see them? Or maybe open another thread to stay on topic? Who did you prove wrong?

Damn straight that motor better b e good at 10k miles. It bette rbe good at 10 times that, and still tight. Because it its not....Well, then that leads to why it wasn't, and that it was attached to a turbo's heat.

Secondly, why is all this power below 5700rpms? The redline on a healthy 928 motor should be 6500rpm. Power during shifts needs to be between 4000-6500. So your saying that after my shift out of first, all my power band amounts to is a 4000-5700rpm blink of any eye?

Where is your torque peak on the 2V motor with 12psi? Where is the HP peak?

And don't try the "your car is in the garage" crap with me John - which is what you do whenever I talk about stuff that your discussing... I have built a 2V motor successfully, and am now on the 5.0L.
Which will be done successfully as well. I know more about this car and its systems then you may realize.

A very well built and assembled 81 motor should make about 260 or so hp. So if your 365 is crank, then you get 90hp out of 12psi?

James-man

If you get the power between 4000 and 6500 or 3000 and 5500 what does it matter? The only reason to take a car to redline is to take advantage of the power up there. If you get all of the power you need a notch lower, I don't see what the big deal is. That was a big "if", though. How much power does one need.

I feel like I am doing my car a favor by shifting at 6000 instead of 6500. My NA peak HP is right @ 6000, so there is only a small advantage to going beyond 6k. Sure, I took it higher last weekend, but only a few times and it wasn't particularly rewarding to do so. High RPMS is where failures occur, no?

I just thought I'd challenge conventional wisdom of setting up a car for max redline performance.

Brendan, I can't wait to see what you put together. You have obviously given it much thought and research. Any completion date estimates? Best of luck to you!

Peace.

Jon B.

Sorry about getting the arguments started fellas. To be honest, I did a little searching and usually when things got out of hand, I change threads. I guess I should have guessed i'd start something. To all the Austin guys, i'm not there right now actually to get a ride or have a gathering. I'm really bummed I missed Porschedillo this year as well. I heard James could have used my help preparing his '94. I'm actually just as interested in the TS system as well. But, since Mark is just starting his project, I figured if I had some questions about that I could just ask him directly. I figured he would chime in though. Nothing wrong with that and it doesn't make sense to me why it would matter so much that he did. I certainly don't mind. That's why I asked for opinions and all that other crap. Anyway, the Twin Screw system is pretty much what I have my mind set on. The powerband is awesome, and if the turbo systems can show that kind of repeatable power and still be affordable I might have to think seriously about that form of Forced Induction as well. Keep up the good work Mark.

Jon

Daniel Dudley

Intermission.

I think some of us on the sidelines are interested in a SC or turbo. We aren't engineers, tinkerers or mad scientists. God bless those of you that are.

I am hoping to see a few systems and maybe get a ride or two at the Frenzy just to get an idea about what I could reasonably expect before I plunk any big wads of cash. Boost is cool !

I have noticed that the pros have well thought out systems and are acting like adults in these threads. Thank you ! It's all Good ! Plenty of room in the pool for everyone. As for the rest of you, please, please, please, don't think about talking to me like that in a bar. Just a suggestion.

One week to frenzy ! And now, back to the show...

BC

Interesting idea James. (My sons name is James, and there is no jimmy, jim, Jamie or Jim bob in our home)

OKay. So what you are saying below is that if the power is from 3000 to 5500, so what, just use it there? That would be fine, but in my 89, and even more so as I recall in the 78, if I shifted at even 6k, then the revs drop back down in a 5spd to about 4k. So that power that John talks about at 3k, or even better for my argument, at 2500, is not usefull to me. The car is geared from the factory for a 6500rpm redline (or 6300 I think in some ofthe cars) SO maybe your point is to only shift at 5700rpm? I don't know, with the gearing in the car (calling Mark K for gearing info) I don't go as fast if I don't shift as close to that upper rev limit as I can.

So thats what I have to say about that. I'm not a gearing guy. A transmission is not exciting to me. An engine screaming at 6800rpm is. And I will personally be making sure it can stay together up there for many years. And be very fun from 3200rpm (just under 80mph I think in 5th) to redline. I have very little use for power below that, and infact as I recall, (someone correct me here) in the shift at near redline from 3 to 4, the revs barely drop past 4300rpm. On completion date estimates, I always say by christmas, but that seems to be every year. But this year is different (), the car is painted, and the engine is going along nicely in the maching stages. I already have tghe V-1, and the megasquirt just needs to be wired up and tuned.

Good conversation.

Jim_H

A new low for the FI threads, too bad.

BC

I always get caught up in these things. I came back from a very exciting ride in Tim Murphy's WIFE's car, not even his higher hp car, and I said on here that I would stop bench racing. I said its not worth it, with how fast just 400hp was, something like 8psi on Tim's Wife's S4, and with a freaking 4spd auto.

Asd an unexperienced passenger, stuff was already moving WAY to quickly to see a difference in boost application or any noticable rev ranges. The car was just sick quick. SICK.

Jim_H

Andy should be shipping my 2.4 (424) next week

The pull was pretty much linear, and the power deceiving. You don't get the 'flappy kick' at 4k rpm. The first time I had a chance to really run it through the gears, after I had got it home and evrything was buttoned up, it pulled so hard at 130 that it kind of freaked me out.

BC

Well, turn that boost up and show us! What, like 12psi?

Jim_H

I have seen dyno sheets from roughly 10 turbo 928's The new rear mounted, twin and single. Not one of these runs broke 400rwhp. No big deal, they still add a lot of whoop *** to the Shark. It seems however that when there is an SC thread started the turbo guys jump in and chest thump that turbos are better and throw in the 'I wouldn't own a Supercharger' comments.
Herr Kuhn had his turbo for sale twice and I asked about a dyno sheet 3 times, never got to see one. I was interested but this nixed my interest in a hurry

On the other hand I lurk on the turbo threads in this forum and notice that Andy, DR or Tim don't jump in and knock on turbos or promote their systems. These threads go un molested from the SC guys.

I imagine the Turbos can do what they say. There are issues concerning heat. There is the issue of putting 10's of thousands of miles on these systems. But... Andy (DR's) and Tim's system at this point are years ahead of a Herr's or Robinsons until the systems are proven. Yet they get offended when they are called on it.
Unfortunately I have received many e mails from members who won't get involved in these threads anymore because of this BS.
Too bad, there is still a lot to be learned.

928ntslow

I think the toughest thing is comparing fact to theory. I am rather intrigued with the twin turbo. I know a year or so back, there were similiar threads knocking the SC and how it couldn't be done efficiently. What gets me is why we have a huge problem supporting each other on these projects. I remember posts saying a turbo just can't be done on a 928 that is worth a damn. Looks like that myth is changing. AND, I would say it is still in it's infancy. I expect greater things to come of it and change several minds and opinions out there in the future.

It would be nice to get Gale Banks in on this! I bet he could build a system in time that would blow some minds...barring price

Here's a good question, why doesn't Porsche go the SC route with their rear engines instead of turbos? Seems they went with a turbo for their front engine SUV as well...wonder what they will do with the Panamera?

I think the turbos and SC's are both great. I guess only time will tell which one is the choice when both kits are plug and play.