Jim bailey - 928 International

Kelly Moss bought a block , stroker crank , rods and 968 pistons .........from 928 International but they opted not to use those rods or pistons and used parts derived from their 944 racing experience in a Nicasil coated block . They initially tried cams from a vendor of 928 parts but quickly concluded that they were too mild for their application (very light weight purpose built tube frame race car ) and had custom grinds made . It has dynoed @711 HP as I recall .

John Veninger

All things being equal..... ( )

Will a motor with Nicasil coating produce more HP than a motor using the stock bore material?

Jim bailey - 928 International

There is some verbage which promotes that claim . The NASCAR boys in their cast iron blocks are convinced that they do get a bit more so much so that they had been airfreighting them to England to be processed . Now they are done in the U S . No one has proven that Nikasil has less drag than alusil that I am aware off ......Joe Fan's 6.5 is Nikasil it does make more power BUT all things are not equal .

bcdavis

I think it is pretty common knowledge that turbochargers are more efficient and more powerful than superchargers. That's why they banned them from NHRA drag-racing...

What we are talking about here, is real world options for the 928...

Even if turbos are better, there is not a kit for the s4 for sale anywhere, nor is there a test car yet...

Even if all the options were available as kits (NOS, SC, Turbos, Stroker), we would still be arguing over peak power, versus cost, versus reliability... All reasonable considerations...

And when you are comparing John's car to a SC car, maybe Quick Carl's car would be a better comparison, since they are both s2 cars.

But like I said, we are still comparing 928s under boost.
The method does not matter.
They will all be really fast.
They are all great cars.

The big question is cost, availibility, and how long it takes to do...

I see the outcomes of Stroker, SC, and Turbo, to all be pretty close.
HP numbers on similar engines, with similar boost, or a good stroker,
will all be in the 500rwhp range. I'd be happy with any of those engines.
The question is which option is a viable one, for the cost, time, etc...

Right now, SC is the ONLY reasonable option for 95% of the owners out there,
who want a 500rwhp car. Unless you have 30-50K to burn, you are looking at a SC...
Strokers in the 500rwhp range require heads, headers, intake, cams, motec, etc.
So you are talking about $20,000 PLUS all those extras...
And there are no turbo kits out there, and no test cars for the s4.

So a supercharger is the only cost-effective option other than NOS.

Debate over.

When you have a cheap stroker kit, or a cheap turbo kit, then the market will change.
Until then, people will still say that they got the same HP, for 1/4 the money...
You can't argue with that math!

Tony

From my understanding, their is a twin turbo 928 out there.

Im sure we will hear/read of it soon enough.

2V4V

bc, et.al.,

Actually (for the most part) they banned twin-screws and centrifugals and axial flows (superchargers) as well as turbos.

Why? Because they ALL are far more efficient than a Roots type blower - which no matter how much you optimize it, is still as stone age and inefficient as a carburator. The people who make those silly looking whiny polished hood phalluses want to stay in the antique production business just like the guys who make carbs. The ONLY way that can happen is by legislating the far superior new technology out, because if they allowed modern tech, everybody in NHRA (any anywhere else that they are the only option) would run to the dumpster with their carbs and their Roots blowers. Or they would lose.

It is quite curious that we are still stuck talking about ~500 RWHP as something 'impressive' on the dyno. Anybody seen what the Mustang guys are getting out of the current Cobra? ~775 RWHP. Simple, relatively cheap bolt-ons. Reliablilty? Well, I personally wouldn't run it for an extended pull, but for "drag racing" and short dyno-pulls, I'm sure it'll be just fine, they've been doing it for a while now.

Turbos are hardly the be-all/end-all. They have inherent limitations and though they are driven by 'free' energy from exhaust gas, they have huge plumbing limitations, compromise your exhaust flow, and heat up your intake charge because the exhaust side will get rather hot in extended use - like glowing red hot. And you have to size them correctly - like any forced intake scenario- but it's far trickier with a turbo than a positive-displacement blower.

There is a lot of HP/TQ still on the table with the current crop of 928 blower stuff out there. Yes, it will require more money to make it better, but not a lot more. Yes, at some point it will probably cost you some longetivity.

Mark Kibort and I were having this discussion just a bit ago on the 'carb 928' thread - it's more about what Porsche did to make emissions than inherent limitations of the design that limit HP output. There's no inherent design limitation to getting more HP out of the 2v/4v cars, Porsche got more (300+ BHP out of the CIS and LH2 4.7 L 2V RoW cars), than most current 'performance' offerings get 20 years later. With newer tech on the ancillary and management systems, there's plenty more HP on the table. Porsche simply did not want to completely overshadow the pipsqueak 911, or the 928 would have always been more powerful than it was, even in USA/Japan emissions trim, let alone RoW cars.

As to why the 'stroker' crowd isn't here en masse, in the center of the Porsche universe, Rennlist? C'mon guys. There's really a whole world full of people who don't care about anything but a fast car. They don't hang in chat rooms or boards, they write a check for whatever speed they need/want, then they enjoy it at their leisure. They don't give a flying f--- what happens out in cyberspace, they just write the check because they can. If they want a faster car, they go buy one or have one built. This online world/community/whatever matters not one whit to them. There's really not much here for them, why would they bother? There's also folks who don't know what eBay is, let alone Rennlist.

Marc has some neat stuff. Some folks will say he spends too much time on R&D. Maybe he does, but that's his way of doing it.

Some will say that most of the supercharger "kits" on the market are woefully inadequate, and don't thoroughly (if at all) address many critical
issues. Addressing of these limitiations is required to get anywhere near the output/longetivity ratio that the 2v/4v engine is truly capable of. But hey, people are buying and getting better performance out of their 928s.

In a couple of years, hopefully we'll all look back and chuckle about most of these threads, like you do when you realize that an Evo or a WRX will smoke an original 930 Turbo.


Greg

Flott Leben

Just my thoughts:

High horsepower numbers are great; steep and high dyno curves are great; but usable horsepower that can be put to the road is really what matters. The amount of horsepower has to match the car's dynamics (i.e., transmission, gearing, differential, suspension, brakes, etc.) to produce a "better" car, meaning faster and quicker than, and at least as good a handling car as, the Porsche engineers designed her to be.

I have yet (and correct me if they are out there) to see actual, professionally performed acceleration results for either the supercharged or stroked cars. Has anyone done 0-60 mph or 1/4 mile runs? I, for one, am not too concerned with which method produces the most horsepower on a dyno. What I would like to see is who has produced the faster car, acceleration-wise.

500, 600, 700 horsepower? What good is it if all you are doing is burning excessive amounts of fuel and rubber (other than increasing top speed - which has a lot more to do with aerodynamics anyway)?

Normy is on the right track: gearing modifications could do a heck of a lot to improve the 928's 0-60 and 1/4 mile times. Has anyone made any modifications in this regard? Has anyone even looked into it? Even 400+hp with new gearing and other mods (brakes, for example) would produce truly amazing results that you could use, day-to-day.

Gretch gave some good reasons as to why he chose the supercharge option. I would like to add one more: "bolt on" and its converse, "bolt off." The "kits" that Tim Murphy and GoSnoRide have been working on offer flexibility that other methods do not. Once you start modifying the engine by boring, stroking, or changing pistons, heads, valves, etc. you are headed down a one-way street that is impossible, or at least a very difficult road, to get you back to where you started. For some of us the ability to do the modifications and to undo the modifications to return the car to stock has some real value and offers piece of mind. With the SC you can also adjust the amount of boost (and hp) to your liking and to more closely match the abilities of both you and your 928.

Just my thoughts.

Jim Nowak

"Did you consider for once that my statement would be based on an even playing field (i.e. turbo S4 vs. Centirfugal S4)? When you make a comparison like that, or any other Enginnering (okay so you aren't an engineer) comparison for that matter you always use a common playing field. It is sort of like doing ANY experiment and holding all other variables constant. In this case, HP of a given engine is a function of Boost. "

That's a good point. I know the 4 valve heads flow much better than the 2 valve heads. So with that in mind, at 7 psi the S4 will be flowing much more air than the 2 valve at the same boost level. Boost is really a measure of backpressure in the intake. I'd imagine if John's exhaust weren't such an inefficient design, no offense meant, he would be making less boost and more power. I recently had custom headers made for a supercharged Mercedes I own. The original exhaust manifolds looked much like John's. After the swap, I lost 3 psi of boost but I picked-up over 40 rwhp.

The difference in displacement between John's 928 & Lagavulin's S4 as well as engine efficiency will make the two very tough if not impossible to compare. I applaud both for their efforts to make the 928's power increase so dramitically.

What you really need to compare is a 928 motorsports supercharger kit for the 2 valve and John's twin turbo set-up. Carl advertises that his 12 psi kit on a CIS 4.5L motor will yield 400 RWHP. That's more power than John's 366 RWHP car does at the same boost level. Looks like the turbo system is only as powerful as the entire system is efficient. I'd bet with a better designed manifold John's car would see much higher hp at a lower boost level.

Jim bailey - 928 International

Tim I believe that nearly everyone who has undertaken a major car Project with nearly ANY SHOP .....finds it often takes way too long (years not months ), costs way too much (far more than the intitial talking numbers) and after waiting so long all too often has less than the expected results .............. . Many small business's need to sell the part first , take deposits in order to be able to buy the necessary parts for a project or make a deposit for a large order . The big problem is if the project has a $30,000 estimate it might have $10,000 of " profit " built into it . HOWEVER if you collect a $10,000 deposit ........on day one your cash flow and " profit" is $10,000 ; if it is spent on "other things" ........Any subsequent time spent on that project MAKES NO MORE PROFIT so do you replace a headlight motor on another car and make labor and parts mark up or go stand in the corner and work on the project which you already have taken all the "profit" out of . So time passes , little seems to get done , customer complains so enough work is done to be able to go back to the customer and ask for more money and the cycle continues . The easy quick immediate cash flow jobs come and go ...to pay the rent , wages ...the projects languish in the corner but once it is all apart it is probably not going anywhere ! ............. Just to put some "profit" back into the project it often helps to "upsell" it make some modifications to the original plan so the $30,000 becomes $40,000 . Sad but somewhat funny example was a small shop "restoring" 356s several years ago when the speedsters hit $100,000 ..... several cars were in process ....pieces here and there powder painter , chrome , engine builder ,transmision builder , upholstery guy .............. when the last car was finally pulled out of the shop there was nearly nothing left of it bits and pieces were "borrowed" from one car for another to get it DONE and the money collected for that car .......musical chairs with car parts . Shop folded owner moved to Arizona
.... There have been several detailed acounts of body shops doing a complete strip and respray ...........and it takes for ever...... Shops which work on RACE cars however are usually very accustomed to working with deadlines , doing what it takes to meet them . If you are going to run the 24 hours of Daytona it only happens once a year !! Missing the deadline is NOT an option .

Carlos

There you go with that damn reality again Jim.

Jim bailey - 928 International

Carlos ....there is no reality.........just the illusion , smoke and mirrors misdirected attention ............and the elephant disappears BUT it was not really there in the first place when the act began it only seemed to be there . So do not question the "disappearance" ; question whether it was ever there in the first place ..............

grimbro

Good entertainment here guys!

gbyron-

Just had to jump in here. I can't take anything you say seriously, as I see that you do not have at least 1000 posts under your belt!. I have to laugh...my thoughts exactly on the whole cyberspace topic. There's a whole world of 928 owners out there that either don't know/care about Rennlist or any other discussion boards. I don't know why it is assumed that everyone is present here. I venture to guess that there are many out there that visit to get a good chuckle once in a while. I know many owners that have incredible examples that simply have no interest or no time to partake in these discussions.

I don't doubt one bit that there are many satisfied SC and stroker customers out there. The fact that they are not spouting out claims, etc. here on Rennlist does not mean that they do not exist. If anyone wants testimonials, take care of it the old fashion way and find out from the vendors whol there clients are and quetion them. Just my .02.

Tom
'93 GTS
5 spd

Z

Doubled from what? Do you have a dyno chart of your car as it was completely stock? You don't even have one from the car in it's original Callaway configuration for comparison, do you? Are you forgetting that besides the turbos, your car has a free flowing exhaust, no cats, a MAF conversion, and an engine that was rebuilt with non-stock parts?

In case anyone's interested, or actually still reading, in the Pro Mod 5.0 class turbos were not banned. They just weren't competitive anymore. All of the current fastest cars and record holders there were centrifugally supercharged the last I saw.

That's why the centrifugal superchargers have been dominating that Pro Mod 5.0 class. By the time you get to those higher gears, the other guy's already holding up the winner's trophy. Charts of Porsche's own testing of a turbo vs supercharger are shown and talked about in "Forced Induction Performance Tuning". The turbo made higher peak horsepower, but the supercharger out accelerated the turbo in every gear.

That's probably the most accurate of any of these comparison's that can be made at this point. I'm not talking about Tim's or Lag's latest dyno charts, since they're making more maximum boost in those charts than Andy was in his. It's been a while, so it's probably a good idea to repost one of Tim's old dyno charts. This is the one with Tim's car making 8psi of boost, which is what Andy said his posted dyno chart was. Since this is how the kit is supplied, this is basically about what can be expected from it. Personally I think much of the "bottom end" that what some people seem to be so concerned about is overblown to a large degree, since I don't upshift as soon my car gets to only 4,000 RPM. Feel free to pick out any RPM point you might be interested in when comparing the charts though.

Lagavulin

Hehe! I guess you just bring out the best in me, John. You’re so easy...

Looks like your having problems with math again.

Twin-turbo gain at 12 psi:
(12 psi rwhp) / (NA rwhp) = 382 / 195 = 1.95 = 95% increase

Centrifugal gain at 11 psi:
(11 psi rwhp) / (NA rwhp) = 513 / 265 = 1.94 = 94 % increase

So you ‘DOUBLED’ your horsepower? Well, according to your standards, it looks like I did too even though I’m running 1 psi less boost.

So your point is... what?

Yeah right. You appear incapable of doing even the simplest of calculations as shown above, so how would you know any better?

Agreed, there’s still a long way to go before anyone can have anything to REALLY talk about, especially compared to those Supra guys.

Guilty as charged!

There is a thread of someone who did it an early 80’s model and was quite pleased with the results, but I don’t know where I read it. I think he took several transmissions and swapped out gear-sets for the ratios he wanted. I do not remember if it was that 'easy' either.

GlenL

Volume or distance?