mark kibort

I think that was deveks claim to fame. they had a secret formula for the coating that seemed to match the Porsche iron coating. don't know much about it, other than it worked. its been driven with no issues for over 100k miles. probably more than any other stroker. (albeit its only a 6 liter stroker, its still a stroker)

that would be interesting, but don't know what you would be able to really see

just as underwhelming as my 6.5 liter built on all the stock stuff, but I had 330rwhp from the 5 liter from the start due to headers and the GTcams and some minor intake mods. I went from 330 to 372 45hp for 5 to 6.4 liter. this 88 S4 went from probably 280rwhp to 320rwhp from a 5 liter to 6 liter. (also 50hp gain) BUT, it doesn't have headers and still has an S4 cam. (as a note, I just remembered, this '88 S4 has no Cats, and is registered in Arizona.)

yep, that's my thoughts. heavily restricted with all the stock stuff. the only break it has is that it has no cats.

That's really the situation. the engine is probably in great shape, as all the indications of clean oil, good even compression numbers seemed to show, but , it is a 100,000mile engine.

yes, as was said, this is not that build. no head work, headers, exhaust mods, brake mods, but does have the devek bilstien suspension with sway bar.

yep, that's all I know how to do, and that's all that could be done back in the day.

mark kibort

that's what we have all seen. 5 liter S4s need a little more to produce what the euro 4.7s made stock. after all, the euro 4.7 was rated at 310hp while the S4 was rated at 317hp..... near the same. But, if you fix the cam situation that lets the extra 300cc breath a little more, and real headers helps even more. remember the holbert car stock with out cats. Just like this car in discussion, made 290rwhp on the dyno in pretty rough shape. that's with GT cams. (or equiv). with headers and some fuel tuning, and a 3.5" exhaust with borla , it got to 330rwhp and was 320rwhp for over 8 years of racing and it was raced A LOT!! there were many 5 liters that got to the 320rwhp with just a GT cam and a race exhaust system. however, just bolting the stock stuff on a 6 .4 liter bottome end, only got you 50hp . 75 if you knew what you were doing, like what GB did with andersons first stroker, getting near 400 to 410rwhp before all the later more "modern" changes .

ptuomov

That's all great. It'll be a welcome digression from the regularly scheduled program to read people questioning other people's honesty w/r their g-tech numbers and not just w/r their dyno numbers! ;-)

In terms of turbo engines, matching the turbos to the engine and those both to transmission is certainly critical.

A case in point: With an unopened stock S4 engine, my estimation would be that my previous gt3071r turbos might be faster overall than the current gtx3576r turbos. With the old turbos, we had average power of about 650 rwhp in the 4400-6600 rpm range and over 500 ft-lbs of torque from 3500 rpm on. This with no lag whatsoever, it was instantly on like the new BMW M5 s63Tu on sport mode. With the new turbos, we're making about the same average power but the power comes on more gradually like in a high hp/l naturally aspirated engine (say my 2012 Carrera GTS Convertible). Both configurations are knock limited, and the lower back pressure of the new turbos doesn't help much at all because the S4 cams are so conservative. So why change the turbos? Because these turbos are for a lower compression engine with slightly bigger cams, and with that engine the new turbos will be clearly better.

By the way, the turbo system development credit should go to John and not me. He's doing the heavy lifting. I am just doing some analytics on the side.

With the correct matching and tuning, a 5.0 turbo car is going to walk all over a supercharged 5.0 car or normally aspirated 6.5L car. The supercharger is tough to beat in terms of $/hp, though. And an illegal, bigger displacement engine can be camouflaged to pass the California smog rectal exam. ITB's allow one to run big cams with perfect street manners and it's difficult to set those up with a turbo. Horses for the courses.

Do you happen to have dyno curves overlaid from your earlier supercharged engine and the new ITB-stroker engine?

The centrifugal supercharger on an otherwise stock S4 engine is extremely hard to beat on $/hp dimension. I don't like belt driven centrifugal superchargers for theoretical reasons, no clean sheet design would use that. Except, by a freak accident, the centrifugal supercharger happens to match the S4 torque curve in the top end almost perfectly, compensating almost exactly the right amount with added boost as the stock S4 cams fall on their faces. That's why the centrifugal supercharger is and should be so popular for S4 folks.

How about the average power under the best [x, 1.5x] rpm range?

dr bob

That mower would do the trick.

GregBBRD

I pay zero attention to dyno numbers. They vary from the conservative to the absurd....on this thread, alone.

That being said, I think your dyno numbers make sense. What would you need to do to make 60 more horsepower?

I can tell you this:

When you put the hammer down on Rob's car with my new prototype intake system....it is difficult to imagine a 928 launching any more violently and surviving. But it would be fun to bolt on a set of drag radials and see what would happen.

It's pretty damn crazy, already.

ptuomov

I am curious, which ones are the absurd dyno numbers on this thread?

IcemanG17

Georges current car is under 500whp...the same engine he went 210mph in....remember Tim and Cheryl's beast when 209.9 with just about 500whp....

Dr Rob's car could hit 200 with his power level, but its a gearing ??? Probably too many RPM's to do it

ORR is a different beast than street or even track cars....high load at high altitude for extended periods of time

ptuomov

Reliability is an interesting topic.

In this thread, I've read some reliability concerns about the Devek stroker in question. Did I miss something, or does this stroker car have 100k miles on it as a stroker?! I must have misunderstood the thread, because if so, all this reliability FUD would be wide off the mark.

The same thing about George's supercharged cars. He's been running this last engine for years now at high loads at high altitude for extended periods of time, as you say. Isn't that evidence that this engine was built to be very reliable?

soupcan

I wouldn't recommend it, dead hooking on the street is very addicting and replacements deplete the fun money quickly. 295/45-17 M/T's fit and are good for 1.7 60' at the track though.

hacker-pschorr

Don't bother, when dyno numbers turn to GPS based acceleration data, some will claim those are inaccurate.

When GPS based data is replaced with actual time slips from a drag strip, those same people will claim it must be a downhill slope or some other BS to discredit the results.

There is no end to this nonsense and why you don't see many people posting performance data anymore, myself included. It's just not worth the headache.

Multiple Supercharged Murf928 (and others like 928 Specialists) cars have posted 4 second and under 0-60 times using G-Techs with both 5-speeds and automatics on street tires.
That still isn't "good enough" for some people.

Not to mention those acceleration times were hampered by traction, not power.

SeanR

+1

I crack up anytime someone says "get your car on the drag strip and prove me wrong". My car will never see one unless it's parked outside while I watch cars built for the strip. Not take one that was built to cruise at 150mph. We have an 1/8th mile strip just up the road too.

Bigfoot928

the factory batch fire is the problem.... replace the fuel injection computer with anyting that will do sequential.... the 928 has so much unburt fuel in the factory exhaust its not even funny...

soupcan

Bingo! I posted an 11 second time slip and got emails saying BS, that was the end of talking drag times here for me. Not interested in arguing with people who have never even seen a dragstrip let alone run on one.

Just for the record though.

My car with x-pipe, dual 2.5 flowmasters and Murf stage 3 ran best of 11.9's with 2.0 60'. With small shot of NOS to get the pig moving on launch 11.5's with 1.8 60'.
That was using Hoosier R6's which hooked ok but slight spin with bottle. Using the M/T's at local 1/8 mile it has run 1.7 60' and 7.2 @ 101 mph which is .3 seconds and 3 mph faster than my best 1/4 mile pass.

I have had the kit for almost 4 years now and it delivers a pretty big smile and a few choice words from the wife every time I drive it.

Another useless data point, the wife's bone stock 86.5 runs 14.7 with her shifting like an old lady.

mark kibort

just put it on a dynojet. it never varies, NEVER. GREG, please understand or learn to understand how a dyno like a dynojet 248e works. There is NO fooling it, unless you really do something to trick it. (like lighten the drums, etc). what does vary is the SAE corrections, and that's where some trust comes in. BUT, if you can show an uncorrected run on a close to normal day, it is what it is. I always do a summer and winter run at the dyno and switch between two dynos as well. the runs are always the same.

as long as you have an uncorrected run, the run is at the mercy of the air conditions, cooling fan blowing up front, what gear its in, and how its strapped down.

you should also understand that the cars run different each dyno run too. heat soaked or not.... sensors working or not, etc. you can see 10hp per run difference until things stabilize out or start getting worse.

Its a great too and much better than anything we can come up with to test /compare performance . all others discussed here, has way too much human factors involved.

cheating is cheating. it can always happen. but if you have dyno that hasn't been rigged, its going to be very accurate. after all, you are just spinning up drums to speed. rate of change of kinetic energy is HP , by definition! very easy to measure and control the test environment of a dynojet 248e.

on my hundreds of dyno runs. I can tell you..... most all that ive seen has been expected and replicated with scary repeatability. ive gone from the stock 4.7, to modifiying it, to a 5 liter version, to S4 stock, to modified to a 6.5 liter change only....... repeated the tests on the 4.7 on another build, and countless changes to the 5 liter. all to find that over 10 years, the hp only varied around 10hp. I was able to fix problems that caused 20hp losses to get it right back to where it was.

I don't think that anyone can think that a 28% change in displacement with a 6.4liter or a 20% change to a 6 liter would provide more than 50% of its change in the form of HP. However, the 4.7 liter sure did, only going from 4.7 to 5 liter. ( 6% change that gave a pretty standard 15% gain in HP). don't know why this is, but it did happen. There are so many factors going on, here, most wouldn't know where to start.

BC

This