J Chen

Oh one more thing, skim the head to bring compression up
to 9:1 . That will do wonders for engine responds & boost
threshold.

Wade B

I just wish I had gotten to drive it that day!

Anyway, I thought maybe I could step outside the box a little and offer my interpretation of things..............

I met Andy for the first time a couple of years ago when I first joined Rennlist. I have to admit that at first, he seemed like one of those "too good to be true" kind of guys that made you ask yourself the question, "Does this guy really know all this stuff for as young as he is, or is this all just BS?" But as you get to know him, and realize that, as he told me, after working at a Porsche dealership for a while and many, many hours of reading and researching the theories and ways of forced induction that, yes, he truly DOES know all this stuff. But like he says too, he doesn't profess to know it all, and is still learning as he talks to others about this and all things Porsche. Because R&D is part of this situation, too. You'll notice the reference to the "949" designation. When Andy first mentioned this idea to me a year ago, that was a big part of why he was doing this, and the WAY he was doing this. He had already done a "hybrid" of sorts by doing the swap into the "954" (combine 944 and 951). So when he was planning his next project, he wanted to reduce turbo lag and maybe increase performance along the way by doing another "hybrid" of sorts, but combining a 944 turbo with a 959 (in technology, that is). There are a lot of suggestions in this thread for getting more power and less lag and etc. But I'm surprised that no one has really noticed the intent on remaining a Porsche purist and doing things the way that Porsche would have done them. And learning and enjoying the R&D along the way. But I guess not everyone knows Andy like us SOW guys do. He is our resident thinker. And maybe you could accomplish things by doing them differently than what Andy has described, but I have faith that he will pull this off one way or the other. And I think most will agree that it will be cool. Just my $.02.

If I am wrong Andy, just tell me to STFU.............

Matt H

Because it isnt the way they would have done it. I am going out on a limb here with....they would have increased displacement. Call it a lucky guess since that is what they did do.

I am not saying he shouldnt try, I am saying:
1) There are far easier and IMHO FAR better ways to do what he is trying to accomplish
2) If he is going to do it he needs to know things like, a K26-6 will never be able to push enough volume to make 350HP
3) I think it is a cool project, really, I do. I just wonder what the goal is. Sometimes people who like to tinker get carried away in the project rather than the outcome.
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Porsche-O-Phile

To run a supercharger / turbocharger setup would certainly pose some issues - the supercharger WOULD allow for low-end / no-lag boosted performance, but is partially offset by the inherently low-ish 8.0:1 compression ratio of the 951 engine. You could boost compression (as has been suggested) through shaving the head, but I doubt you'd get an entire point (8.0 to 9.0) by this method. You also run into issues with throwing the timing off, since the distance from the cam pulley to the crank pulley is changed. Lindsey makes a compensator pulley for this, but it is very expensive and the massive amount of material that would need to be removed by shaving in order to go from 8.0 to 9.0 would probably exceed its limits (if you even had enough material left to allow the head to work!) IIRC a 0.060 shave will boost you about 0.2 points - I wouldn't want to go much more than that in any case.

So, you have a "low end" problem with the supercharger. In order to offset the 8.0 (or maybe 8.2-ish):1 compression ratio and get a nice launch & initial power, you obviously need a fairly high-boost supercharger (8-10 psi). This will run out of steam quicker and produce more parasitic drag on the engine as the RPMs come up, the supercharger effectiveness drops off and the turbo effectiveness comes up. You COULD run some sort of clutch mechanism for the supercharger to compensate for this (that would "kick off" the supercharger and eliminate its engine drag once it detected the turbo coming on and producing XX.X psi of boost or whatever, but I don't know enough about these to know if that's ever been done - you might be doing your own R&D for that one. . . It's also another belt / pulley / clutch to fail.

You also have to consider oil flow to both units and if you ARE running low-end boost for harder launches, I'd keep a supply of trannies and CVs on hand because they're likely to get torn up rather quickly. A lot of that is driver technique, too though. . .

Very intriguing idea though.

NZ951

Now, a SC from 0-3K would be nice!

inactiveuser92616

^^^ personally, I start off from a light at atleast 800RPM, usually more like 1100. But if you like turning off your car and launching it with the starter, thats cool too.

NZ951

Sadly sometimes I have to start at 4,500-5,000 to launch at the lights. The 1/4 mile lights that is.

Danno

Good idea Andy! I think combining the Callaway right-side turbo with the Porsche left-side turbo in a sequential-twin set-up is gonna be cool! Personally, I don't like the plumbing that Porsche used in the 959 as it really hinders the sequential configuration. Low-end lag on the 959 isn't any better than a parallel-twin set-up like the 993TT. Also the parallel configuration on the 959 isn't optimized either because the routing to each turbo isn't identical in a perfect Y. Yeah, I get that physical routing of exhaust has limitations in any engine-compartment and you have to do the best you can. That's why V and flat-6 engines are best with parallel-twin turbos and inline engines can better use sequential twins. The trick is to minimize the amount of exhaust-plumbing to get the best exhaust-velocity possible.

On your turbo selections, the K26/6 is caught right in no-mans land! It's got too much low-end lag for your liking, and it can't hold high-end boost either. You would want to use a twin configuration that use something like a K24/K27 combo to get low-end AND top-end.

Ideally, with the functional equivalent of two Y's in the exhaust and intake plumbing, you want to keep the split and two legs to be as short as possible and have the valving that changes single-turbo to twin-turbo be governed by both RPM and manifold-pressure. For example at mid-range/partial-throttle operation and low-boost, you may stay mainly on the small turbo and start to spool up the 2nd turbo from 4000-5000rpm. But at full-throttle/high-boost, you may start opening it up from 2500-3500rpm. Both valves needs to be switched over gradually, so you'll need some electronics intelligence controlling stepper motors here. The vacuum-activated stuff in the SupraTT is too complicated and when they fail, they grenade the #2 turbo by switching it on too suddenly.

nine-44

OK, I'm not relying only on the K-26 for up top, it's both operating together above 6-8 psi, that is my "on paper" changeover point. I can't go with an internally wastegatted turbo for primary, it would dump the driving pressure before the secondary. The VNT actually opens beyond full flow to restrict the exhaust flow acting as a wastegate and thus also forcing flow to the secondary to drive it harder without waisting any driving pressure.

Danno, yeah, even the 959 has some to be desired as far as layout, plumbing and restrictions. I hope to go smooth with bends, Ys and layout.

I plan to run a T-bird TC intercooler for the primary, possibly mouned as the callaway, low or up top kinda as a CGT, not sure. That's all packaging.

A SC is not the way I choose to go, changeover is a beeotch to get smooth between a mechanically driven unit and one that is driven by situations that vairy so much. I also thoght of the Delta S4 idea with an added clutch to kill the paracitic load up top, eh, I'm a turbo guy for better or worse.

As far as "waking up" the secondary turbo, I plan to pulse the exhaust brake to get it up and going before the bypass valve on the cold side is closed, much like the 959. The secondary will be up to spool with no load before it pushes much air. That's all in the R&D work there.

As far as what Porsche does, did and increased displacement... I hear that a 2.5 is too small for a sequential setup, hmmm. The 959 was a whopping 2.6L!!! If all goes well, when I build the internals, I hope to figure a way to go to 2.6L just for kicks. Before someone says it, yeah, the 959 was a 6 cyl, the added exhaust pulses with help a bit on lag and whatnot. I'll have to do some pulse tuning for driving the turbo the best I can. Again, R&D work.

Again, no, the K-26#6 or the K-26#8 won't flow enough for 350hp, wheels or crank, never did say that, with both turbos, each pulling their fare share, I'm planning for 350-500 hp, prolly just crank, we'll see.

NZ951

Are you sure the #8 wont flow 350 crank HP? I beg to differ...

J Chen

I don't think it's a matter of capacity. Rather it's
the number of cylinders. Closer firing pulses of
6 over 4 cylinder engine will definately add boost
threshold.

Matt H

2.6L motor is doable, destroked 3.0L. Contact Chris White he has at least one of them. It is common as 2.6L still fit into GT3 (IIRC) at any rate the 2.6L can certainly be done. Comparing it to 959 is apples to monkeys, if you know what I mean. Good luck to you.
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nine-44

Ok NZ, the #8 prolly could do it, I'd rather not push the envelope tho. The K-26 housing on the cold side is a bit small for my liking, I don't want to push too much heat. The #6 hot side is a bit small and shows it up top even on my car in close to stock form. I'm hitting my peak boost about 2500rpms an is too laggy for me and falls off in 4th and 5th gear about 5k or so and shows a little in 3rd way up. I'm running a manual boost controller leaving a bit to be desired. My original plan waaay back was to run 2 K-03s on an NA motor, I ended up going to 951 territory to have a better start on the project. I've been wanting to see 2 turbos on a 944 for some time now.

I know that trying to compare a mutt 944 thing with some homecooked malarky sequential setup to a 959 is really no comparison. I can not hope to be able to sink the Indy and Lemans derived technology into a 944 that the 959 was built on.

I'm choosing to build what I feel is the best design for the goal and application, it's just plain cool that it happened to be the design Porsche chose to build into their ultimate and timeless road car, the 959. They built it in 87 and 88, I have an 88 car with an 87 motor, lol.

Overkill is merely sufficient in my book.

NZ951

Do you have a Tial or stock WG?

Adrian

There was a real Porsche 954, it was the 250 HP 911SC/RS.
Ciao,
Adrian