super charger gossip
05-28-2003, 08:43 PM
#1
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super charger gossip
I just heard from a cusotmer who got 525 RWHP on a Dyno jet yesterday. He has a stock 87 5.0 with 13 lbs of boost. Sounds like some people are doing their homework.
05-28-2003, 09:12 PM
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For how long is he going to get that power?
I mean, is he going to end up like the guy with the Eclipse who tried to race the M3?
I once followed a supercharged Boxster at a fast fun drive. Sure, that thing was incredibly fast, could easily pull away from me on full acceleration. However, everytime he floored it or lifted off, I saw a puff of burned oil coming from his huge exhaust pipe. I've often wondered, if this engine is still alive...
I mean, is he going to end up like the guy with the Eclipse who tried to race the M3?
I once followed a supercharged Boxster at a fast fun drive. Sure, that thing was incredibly fast, could easily pull away from me on full acceleration. However, everytime he floored it or lifted off, I saw a puff of burned oil coming from his huge exhaust pipe. I've often wondered, if this engine is still alive...
05-28-2003, 09:43 PM
#4
Drifting
yeah i agree nicole, reliability is apparently an issue with engines melting and so on. more to the point, has anyone ever simply bolted one of these things on without a kit either missing some necessary component or else having to fabricate and re engineer parts? not to mention post instalation tuning, now who can reliably do that?
05-28-2003, 10:04 PM
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More supercharger gossip:
I was at the Thunderhill track on Thursday doing a driver's ed event with the Norcal Racing Club. There was another 928S4 out there owned by a gentleman from Sacramento. Under the hood there was a Vortech blower from a FAST kit.
If I remember the details correctly, he was running 7 lb boost on 91 street octane and using the Unichip piggback. He wasn't having any problems with detonation but cooling was an issue on the track (it was about 100 degrees that day). He had just gotten the car running after having heads and valves done after an unrelated timing belt failure.
So no data on long term usage, but hopefully it will continue to run well and add to the knowledge pool.
-Dennis
I was at the Thunderhill track on Thursday doing a driver's ed event with the Norcal Racing Club. There was another 928S4 out there owned by a gentleman from Sacramento. Under the hood there was a Vortech blower from a FAST kit.
If I remember the details correctly, he was running 7 lb boost on 91 street octane and using the Unichip piggback. He wasn't having any problems with detonation but cooling was an issue on the track (it was about 100 degrees that day). He had just gotten the car running after having heads and valves done after an unrelated timing belt failure.
So no data on long term usage, but hopefully it will continue to run well and add to the knowledge pool.
-Dennis
05-28-2003, 10:04 PM
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Yeah... If the F.A.S.T. kit is all sorted now, I would like to hear a testimonial to that effect. That you bought the kit, bolted in onto your stock 928, and now are making XXXrwhp...
As far as reliability, it is all about how much boost you run, and how strong you build your engine. If you build a strong engine from the ground up, and supercharge it, it will probably last a long time. But if you bolt it onto a stock engine, your engine life will be decreased somewhat.
But regardless of lifespan, the object of people who supercharge is to have insane horsepower, not long-term reliability. I always chuckle, because some 928 owners want things to stay stock, and appreciate the engineering, and longevity, of the stock engines. Doing something like bolting a supercharger on your engine is purely to be fast, and it is not in the same realm as a porsche-engineered engine, etc. It is hot-rodding at it's finest, and I think that the guy making 525 rwhp with their car could care less about longevity. He is just having fun with a damn fast car...
As far as reliability, it is all about how much boost you run, and how strong you build your engine. If you build a strong engine from the ground up, and supercharge it, it will probably last a long time. But if you bolt it onto a stock engine, your engine life will be decreased somewhat.
But regardless of lifespan, the object of people who supercharge is to have insane horsepower, not long-term reliability. I always chuckle, because some 928 owners want things to stay stock, and appreciate the engineering, and longevity, of the stock engines. Doing something like bolting a supercharger on your engine is purely to be fast, and it is not in the same realm as a porsche-engineered engine, etc. It is hot-rodding at it's finest, and I think that the guy making 525 rwhp with their car could care less about longevity. He is just having fun with a damn fast car...
05-28-2003, 11:14 PM
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Fantastic results....Look forward to the posting of the dyno charts and a "regular report" on durability!
Lets hope that 928 Developments intake on your racer has similar results.....looks like it is complete by the advertisments on 928D site...any dyno numbers yet??
Marc
DEVEK
Lets hope that 928 Developments intake on your racer has similar results.....looks like it is complete by the advertisments on 928D site...any dyno numbers yet??
Marc
DEVEK
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05-28-2003, 11:15 PM
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Great timing Mark. I was just going to post when I saw this thread.
A while back a dyno chart from Tim Murphy's Vortech supercharged 1988 928S4 was posted. The chart was a dyno pull he did last Fall. Unfortunately there were some supercharger belt slippage problems at that time, so the numbers probably weren't what they might have been. What it ran is what it ran though, and there's no point in speculating what it would have, should have, or might have done if it wasn't for the belt issue. Since then, the supercharger bracket and pulleys have been redesigned, and it was time to try the dyno again. Belt slippage isn't a problem now like it was back in the Fall, but unfortunately a new issue became apparent this time. The stock fuel pump isn't flowing enough fuel. It's running out of capacity, and power is dropping off at the high end because of it as the mixture goes leaner than optimum. Oh well, better luck next time I guess. Hopefully after a larger capacity fuel pump is installed he'll finally get a decent dyno pull. No sense in speculating on that either though. At this point he's only able to do as well as this:
He's had the supercharger on the car for going on three years now I guess. No, it wasn't always making this much power. The belt slippage was a big part of that. When I first saw it on the dyno almost two years ago it was only making 410 rwhp or so.
A while back a dyno chart from Tim Murphy's Vortech supercharged 1988 928S4 was posted. The chart was a dyno pull he did last Fall. Unfortunately there were some supercharger belt slippage problems at that time, so the numbers probably weren't what they might have been. What it ran is what it ran though, and there's no point in speculating what it would have, should have, or might have done if it wasn't for the belt issue. Since then, the supercharger bracket and pulleys have been redesigned, and it was time to try the dyno again. Belt slippage isn't a problem now like it was back in the Fall, but unfortunately a new issue became apparent this time. The stock fuel pump isn't flowing enough fuel. It's running out of capacity, and power is dropping off at the high end because of it as the mixture goes leaner than optimum. Oh well, better luck next time I guess. Hopefully after a larger capacity fuel pump is installed he'll finally get a decent dyno pull. No sense in speculating on that either though. At this point he's only able to do as well as this:
Originally posted by Nicole:
For how long is he going to get that power
For how long is he going to get that power
Last edited by Z; 07-19-2003 at 07:24 PM.
05-28-2003, 11:24 PM
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[QUOTE]Originally posted by Z:
[QB] At this point he's only able to do as well as this:
I'd be happy rebuilding engines every year if I get "only" this much rwhp!!!
Tarek
[QB] At this point he's only able to do as well as this:
I'd be happy rebuilding engines every year if I get "only" this much rwhp!!!
Tarek
05-28-2003, 11:28 PM
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Only thing to say about Tim's 928 is What A Ride! I've never felt my eyes being sucked that far in the back of my head before. But on the highway? Cruise control on, A/C blowing cold, quiet as a new Mercedes. The ultimate GT.
05-29-2003, 03:43 AM
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Very cool! <img border="0" alt="[burnout]" title="" src="graemlins/burnout.gif" />
Tim is <img border="0" alt="[king]" title="" src="graemlins/r.gif" /> ...... <img border="0" alt="[cheers]" title="" src="graemlins/beerchug.gif" />
Tim is <img border="0" alt="[king]" title="" src="graemlins/r.gif" /> ...... <img border="0" alt="[cheers]" title="" src="graemlins/beerchug.gif" />
05-29-2003, 09:37 AM
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</font><blockquote><font size="1" face="Verdana,Tahoma,Helvetica">quote:</font><hr /><font size="2" face="Verdana,Tahoma,Helvetica">It is hot-rodding at it's finest, and I think that the guy making 525 rwhp with their car could care less about longevity. He is just having fun with a damn fast car...</font><hr /></blockquote><font size="2" face="Verdana,Tahoma,Helvetica">Well said! <img border="0" alt="[cheers]" title="" src="graemlins/beerchug.gif" />
I do think the longevity issue people are mentioning is a bit over-done though.
For example, doubling one's horsepower equates to double the internal stress, right?
Wrong, and here’s why:
Firstly, lets assume the engine is optimized: air/fuel and timing are spot-on, and a good balance of compression ratio/boost temps, so that detonation won’t be a factor. In other words, the engine was supercharged the right way.
To start with, the greatest internal stress on a engine occurs at max RPM on the exhaust stroke at TDC when the tensile strength of the connecting rod is tested to it’s max as there are no compressive forces whatsoever to help decelerate the piston's mass as it reaches TDC since the exhaust valves is wide open, offering no resistance, or compressive force. It is here where a rod will more than likely come apart, not under a compressive load such as the power stroke. You can picture in your mind that when an object is experiencing a tensile load, that object is trying to ‘fly’ apart whereas in a compressive load, that same object is being ‘packed’ together. Thus, it is known that a connecting rod can handle much higher compressive loads than a tensile one.
With that said, the max RPM of a normally aspirated engine is usually the same as it’s blown counterpart, so the tensile loading of the connecting rod will remain the same.
Now for the loading upon the crankshaft.
Once the charged is ignited, the cylinder pressure will continue to rise until it reaches it's peak at approximately 20 degrees after TDC (..on the power stroke), and is exerting a max compressive load first on the piston, and is tranfered to the rod, bearing, crankshaft, and finally bearing.
Now lets supercharge that engine so that it’s horsepower is now doubled, and again let’s measure the peak cylinder pressure where the compressive loads are greatest. One would be quite surprised to find out that the peak cylinder pressure has increased by only 20%, since all the extra air/fuel does not burn all at once.
Because of that, by the time the crank rotates to 90 degrees after TDC, there’s still ‘tons’ of air/fuel mixture remaining to be burned and subsequently used to push upon the crank at such an optimum leverage point. It is at this point in time where most of the massive amounts of torque is generated in a supercharged engine.
So we doubled our horsepower, yet only increased the peak load on the bottom end by only 20%; that's a nice surprise!
Apparently, Tim Murphy has achieved this supercharger nirvana to the tune of 525 rwhp. Of course, time will tell reliability-wise, but in the meantime, all indicators are pointing favorably for Tim.
Good job, Tim! <img border="0" alt="[cheers]" title="" src="graemlins/beerchug.gif" />
I do think the longevity issue people are mentioning is a bit over-done though.
For example, doubling one's horsepower equates to double the internal stress, right?
Wrong, and here’s why:
Firstly, lets assume the engine is optimized: air/fuel and timing are spot-on, and a good balance of compression ratio/boost temps, so that detonation won’t be a factor. In other words, the engine was supercharged the right way.
To start with, the greatest internal stress on a engine occurs at max RPM on the exhaust stroke at TDC when the tensile strength of the connecting rod is tested to it’s max as there are no compressive forces whatsoever to help decelerate the piston's mass as it reaches TDC since the exhaust valves is wide open, offering no resistance, or compressive force. It is here where a rod will more than likely come apart, not under a compressive load such as the power stroke. You can picture in your mind that when an object is experiencing a tensile load, that object is trying to ‘fly’ apart whereas in a compressive load, that same object is being ‘packed’ together. Thus, it is known that a connecting rod can handle much higher compressive loads than a tensile one.
With that said, the max RPM of a normally aspirated engine is usually the same as it’s blown counterpart, so the tensile loading of the connecting rod will remain the same.
Now for the loading upon the crankshaft.
Once the charged is ignited, the cylinder pressure will continue to rise until it reaches it's peak at approximately 20 degrees after TDC (..on the power stroke), and is exerting a max compressive load first on the piston, and is tranfered to the rod, bearing, crankshaft, and finally bearing.
Now lets supercharge that engine so that it’s horsepower is now doubled, and again let’s measure the peak cylinder pressure where the compressive loads are greatest. One would be quite surprised to find out that the peak cylinder pressure has increased by only 20%, since all the extra air/fuel does not burn all at once.
Because of that, by the time the crank rotates to 90 degrees after TDC, there’s still ‘tons’ of air/fuel mixture remaining to be burned and subsequently used to push upon the crank at such an optimum leverage point. It is at this point in time where most of the massive amounts of torque is generated in a supercharged engine.
So we doubled our horsepower, yet only increased the peak load on the bottom end by only 20%; that's a nice surprise!
Apparently, Tim Murphy has achieved this supercharger nirvana to the tune of 525 rwhp. Of course, time will tell reliability-wise, but in the meantime, all indicators are pointing favorably for Tim.
Good job, Tim! <img border="0" alt="[cheers]" title="" src="graemlins/beerchug.gif" />
05-29-2003, 11:20 AM
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Lagavulin,
thanks for you post.
For those of you who don't want ot believe him, and are still skeptical on the longevity of SC engines (don't get me wrong, it is somewhat of a concern but as Lagavulin says, overplayed) grab a copy of Corky Bell's "Supercharged". Great read for those interested in keeping up with M3's and souped up Civics.
thanks for you post.
For those of you who don't want ot believe him, and are still skeptical on the longevity of SC engines (don't get me wrong, it is somewhat of a concern but as Lagavulin says, overplayed) grab a copy of Corky Bell's "Supercharged". Great read for those interested in keeping up with M3's and souped up Civics.