Nathan Valles

JOE DYER: That's an awesome car. It looks great and I'm sure it runs great.

MY PERSONAL OPINION: If you have the money to spend on it, and you don't mind, GO FOR IT. It's your car and your money. Don't let anyone tell you different.

If on the other hand you need ample justification to spend money (and possibly the wife's permission) and this doesn't qualify then DON"T DO IT. It's that simple. Only Joe knows what he did and why he made the choices he did. If you were in his shoes with his circumstances and his reasons you might just have made the same choices yourself.

As for me, Congrats to Joe and all his hard work. It looks BEAUTIFUL.

Abby Normal

I'm interested in your compression ratio, because a 10:1 compression engine running 11PSI on pump gas does not make 569rwhp, it is mathimatically impossible. No stones, just wondering. The engine looks beautiful!

Lagavulin

Why do you say it's 'mathematically impossible'? What hp number do you suggest? Please provide your reasoning.

For the time being, I will stand by my calcs which suggest that if the car is running 11 psi measured in the manifold, it should very well make around 569 rwhp, give or take.

However, according to the picture, if the boost measurement is taken from the blower only, there will be a pressure drop between it and intake manifold, so the actual boost the engine sees will be a little lower, probably 10 psi. 10 psi still puts it at 546 rwhp; that's still a lot of power to the rear wheels.

Abby Normal

To high compression ratio for the amount of pressure / fuel octane rating of pump gas.

Does it make power? yes.

Will it hold up?

Time will tell....................

For $35k he better hope it does.

Brent 89-GT

I have to side with Abby on the durability issues. With a couple of rebuilds, were forged pistons used the second time? I would think that an upgrade like that would be mandatory if you were rebuilding it anyway. With forged pistons I would bet it would live a long time if the A/F ratios were correct.

Of course it sounds like the shop did a great job of bolting it all together but, might be lacking in the critical area of tuning such a beast.

Best of luck to all running SC'ed 928's.

Z

Tim Murphy's car was making 14 psi of boost with 10:1 compression on pump gas. No problems.

Sounds like they used oversize stock GTS pistons. GTS pistons are forged, but they're also 10.4:1 compression, not 10:1. Actually I'm not sure how that 10:1 compression figure suddenly popped up. Don't anybody expect forged pistons to save you if the system isn't done well. There are an awful lot of blown up forged pistons out there in the 944 turbo world.

Brent 89-GT

I'm a guy who blew up his 944 T twice. Forged pistons wont save a botched job but they certainly add stregnth and durability. Both times my turbo blew, it was on a racetrack. I fully intend to continue to run my 928 on the track 2-3 times a year. My biggest concern, and the reason I haven't yet approached Tim, is whether or not a SC'ed 928 will live on the track. Running hard on the street is no comparison. Obviously durability is compromised by pressurizing the engine. How much? I think that remains to be seen. Would I feel better if my car already had forged pistons, OH YEAH!

Abby Normal

The 'Tilo' Giant Killer 928 resides here in South Louisiana now and is a regular at the track. This is a stroked 6.5 litre SC'd motor. It seams to hold up fine, however this application is only running about 6psi of boost.

Z

If done right, I really don't see a problem with it. If I were running on the track, I think I'd be more concerned about the 2/6 rod bearing thing than anything really supercharger related. For some reason some people seem to to think that just because a car is supercharged there's something inherently wrong that will cause it to blow up. So far, with a well done system, there's no history of that as far as I know. I can't help but think some of those same people would have been the ones saying the same sort of thing about stroker motors when the first ones were starting to be built.

Brent 89-GT

well..I'm not one of the guys that would have thought something like that about a stroker. The stroker engine is a completely different method of making power. I would definatley consider it a less stressed engine. The SC is being put on an engine designed for lower operating stresses.

I knew when I posted that, somebody would make an attempt to compare "hard" street running with putting 250 track miles on a car in a day. There is no comparison. There is no way you can even come close to running that hard on the street.

I know a lot of guys in the 944 community that ran the exact set-up as mine on the street for years without a single problem. The problem came when run under duress on a racetrack, TWICE.

I don't think that a SC'ed car is somehow more liable to blow just based on the SC install. I know that it places more stress on the engine and that racing compounds that. I would like to see someone like Kibbort bolt one on and run for a season. THAT would be a test.

Z

So the engine is designed for the stress of having it's displacement increased by 1.4 or more liters, it's piston speed increased, it's horsepower and torque increased, and at the same time have it's cylinder walls reduced in thickness?

Quick Carl has been tracking his supercharged '78 without issues related to stress on the engine from the supercharger. He'll be at Road America again this weekend with it.

Still waiting to hear more than just opinions on the engine not being able to handle the stress of a well done supercharger installation.

OahuJames

Hey Joe, The engine looks amazing. Especially, since I just had my hood up and was thinking my engine looked pretty good.

I would imagine since your car is a '93 the body looks great to.

Do you have any other pictures you can post?

Congrats,

Fastest928

Z,
I posted BMEP numbers for different configurtion. Do you consider this an opinion?

Supercharged stock longblocks have yet to be dyno'd every year at different ambiant temps, with different octanes, or even after 50K miles to see if there is any power degradation. Or dyno'd 10 runs in a row to see the effects of heat soak, etc. What data do you have that backs up your "reliability" statements?

No supercharged engine has yet to reach 10,000 miles!!

There has been no formal testing, no testing plan (except the one I wrote for a supercharger kit manuf over 5 years ago). Which I doubt any current kit will pass, yet stock engines as well as strokers pass! If you think a current stock block sc application has a chance, bring it on out and I will dig up the test and run it!

Dont get me wrong, I like boost....even to the point of considering building one of my own sc 928 engines to see what can be done when it is done with the intention of supercharging from the start...but stating or alleging that any 928 stock block supercharger application is equal or lower in stress to a stroker is incorrect.

HP for hp, stroker engines produce less stress than supercharged engines.

Marc
DEVEK

Abby Normal

Marc,

Is the 'Tilo' car a Devek Stroker? For some reason I was thinking it is. That car has to have a fair amount track time... I'm guessing here.

If so, that engine is holding up well!

Z

Nope, but i do consider it an opinion that BMEP is some sort of ultimate indicator of whether an engine can withstand the stress of supercharging or not. If so, remember that I posted the BMEP of a Yugo engine in addition to those you posted.

Maybe not by you. Are you assuming that means nobody has ever done it? If so, you're mistaken.

You mean that you know of. Again, I'm affraid you're mistaken.

If you'll read my posts, I never said anything about the stress of a supercharged one in direct comparison to a stroker. I have said that strokers have higher piston speeds, higher bearing speeds, and thinner cylinder walls than a supercharger installation on a stock displacement supercharged engine, and that stock engines weren't designed for being stroked any more than they were designed for supercharging.

Stress to what? I'm not going to argue that either way. Stock engines have less "stress" than either stroked or supercharged ones. Want low "stress"? Keep it stock, do the regular maintenance, and never go over 2,000 RPM. Low "stress", low cost, low BMEP. Should last a long time.