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Don’t fret, I have done plenty of ls swaps over the years, most of them on cars that have engines that decided to not run anymore. 22 years ago it was the FD rx7 forums that thought it ruined the car with the LS1 and a pro charger, Mercedes sl600 R129 v12 concerted to an LQ4 with a turbo and 4l80e. Those people didn’t like it either. Even the Lincoln Mark7 LSC that I converted to an ls1 4l60e got forums in a uproar.
The 996 community is actually mostly tolerant, and understanding in the fact that the engine replacement in these cars can cost as much or more than the value of the car itself. The used engine market is just a crapshoot, and still expensive. You still have about 300hp after all that.
While I’m not a 4 cylinder guy, the obvious upsides are lots of weight reduction, and much more room to work on the car, and the fact that used engines are plentiful and relatively robust, and it works well with the gear ratios of the car. I would imagine with a few stronger parts the redline on the k24 could be taken north of 8000rpm, and that’s interesting as well.
My k24 with all turbo accessories weighs 87lbs lighter than the stock m96. If I did a more conservative turbo setup I bet I could shave another 15lbs off that too. And that’s obviously behind the rear axle!
This is my third m96 race motor and the first to be in substantially stock spec. Race spec motors blew up; they all blow up.
Specs:
ARP Bolts
BMC Air Filter
Motorsports AOS
LN IMS
LN Deep Sump
Electric power steering and no AC
997 x51 headers into straight pipes
Vision Motorsports tune
You’ll see the power band looks odd. This motor put out over 320 bhp unmolested, but I needed two things: most utile power to be up above 5k rpm, bhp to be closer to 310 for power to weight. By using mostly stock parts and detuning the power, the hope is this motor will last at least 80 hours. It’s at 15 hours now and neither of the race motors made it that far.
This is my third m96 race motor and the first to be in substantially stock spec. Race spec motors blew up; they all blow up.
Specs:
ARP Bolts
BMC Air Filter
Motorsports AOS
LN IMS
LN Deep Sump
Electric power steering and no AC
997 x51 headers into straight pipes
Vision Motorsports tune
You’ll see the power band looks odd. This motor put out over 320 bhp unmolested, but I needed two things: most utile power to be up above 5k rpm, bhp to be closer to 310 for power to weight. By using mostly stock parts and detuning the power, the hope is this motor will last at least 80 hours. It’s at 15 hours now and neither of the race motors made it that far.
300hp in this chassis is fun. What was the cause of the first two failures out of curiosity?
Same power within +/- 5 bhp, but could push the band way further up the RPM’s. After this pull we set the rev limiter at 7,250. Just no point in letting it spin up higher
Originally Posted by BaysideFab
300hp in this chassis is fun. What was the cause of the first two failures out of curiosity?
I hit 2 of the 3 common failures.
1) Aspirated case . Sent a rod through the bottom of the motor. Result was the harmonic issue the m96 case creates when spinning motorsports parts faster and lighter than stock. Fully blueprinted motor with JE pistons. Still no global fix identified.
2) Seized from oiling issues. Again, fully blueprinted motor with all the tricks (boat tailed, deep sump, case ported/polished, etc). To be perfectly fair, I’ll give this one 25% user error as it should never have been on the Autoclub Speedway Roval. Nothing showed in the data, but G’s plus significant banking = kaboom. Still no global fix for this either. Spoke with a number of well known engine builders on the third rebuild and the consensus was it’s an engineering fault with the case that cannot be solved. M96 was developed to be a street motor bridging the 911 and Boxster and Porsche simply didn’t spend the money to make it race-able. Anyone telling you otherwise is looking for your money.
Same power within +/- 5 bhp, but could push the band way further up the RPM’s. After this pull we set the rev limiter at 7,250. Just no point in letting it spin up higher
I hit 2 of the 3 common failures.
1) Aspirated case . Sent a rod through the bottom of the motor. Result was the harmonic issue the m96 case creates when spinning motorsports parts faster and lighter than stock. Fully blueprinted motor with JE pistons. Still no global fix identified.
2) Seized from oiling issues. Again, fully blueprinted motor with all the tricks (boat tailed, deep sump, case ported/polished, etc). To be perfectly fair, I’ll give this one 25% user error as it should never have been on the Autoclub Speedway Roval. Nothing showed in the data, but G’s plus significant banking = kaboom. Still no global fix for this either. Spoke with a number of well known engine builders on the third rebuild and the consensus was it’s an engineering fault with the case that cannot be solved. M96 was developed to be a street motor bridging the 911 and Boxster and Porsche simply didn’t spend the money to make it race-able. Anyone telling you otherwise is looking for your money.
ooof tough break man. Don’t even want to know what that cost ya. Ever consider just doing a LS swap to stop the pain? Cheap motors, cheap parts, more power.
Same power within +/- 5 bhp, but could push the band way further up the RPM’s. After this pull we set the rev limiter at 7,250. Just no point in letting it spin up higher
I hit 2 of the 3 common failures.
1) Aspirated case . Sent a rod through the bottom of the motor. Result was the harmonic issue the m96 case creates when spinning motorsports parts faster and lighter than stock. Fully blueprinted motor with JE pistons. Still no global fix identified.
Yea, all engines have an inherent Harmonic vibration resonance, some worse than others , but ALL have it..The best you can do is move the resonance frequency out of the "use zone" to minimize the effects from it..
I dealt with this problem on a 4 cyl inline race motor back in the 80's, it had a harmonic vibration resonance at 4krpm 8krpm and 12krpm, the "third order" resonance at 12k RPM was a killer. It would shatter all the flywheel bolts like glass no matter what size/type/method of bolts/retention was used.. The only cure is a "reverse rotating ballance shaft" or in my case I resolved to set the Rev limit at 11,500 RPM..
Originally Posted by mehoff
2) Seized from oiling issues. Again, fully blueprinted motor with all the tricks (boat tailed, deep sump, case ported/polished, etc). To be perfectly fair, I’ll give this one 25% user error as it should never have been on the Autoclub Speedway Roval. Nothing showed in the data, but G’s plus significant banking = kaboom. Still no global fix for this either. Spoke with a number of well known engine builders on the third rebuild and the consensus was it’s an engineering fault with the case that cannot be solved. M96 was developed to be a street motor bridging the 911 and Boxster and Porsche simply didn’t spend the money to make it race-able. Anyone telling you otherwise is looking for your money.
This is interesting, since I have always loved fault analysis , and has been my forte . What were the G-forces that were encountered?
I have no idea what the people you spoke to were talking about in regards to the " engine case" not handling the g-force. The metal of the case doesn't know or care what the g-force is or which direction it is coming from..Even at 2G the deflection force is only twice the weight of the engine, say 1k pounds.
There are forces in the tens of thousands of pounds acting on the metal of the engine and 1k lbs from the g-force in a turn would be like a gnat on an elephant..
Did the bearing journal turn blue from lack of lubrication? I suspect they are talking about the "sump design" can't handle the "G-Force" and therefore led to failure..
Yea, all engines have an inherent Harmonic vibration resonance, some worse than others , but ALL have it..The best you can do is move the resonance frequency out of the "use zone" to minimize the effects from it..
I dealt with this problem on a 4 cyl inline race motor back in the 80's, it had a harmonic vibration resonance at 4krpm 8krpm and 12krpm, the "third order" resonance at 12k RPM was a killer. It would shatter all the flywheel bolts like glass no matter what size/type/method of bolts/retention was used.. The only cure is a "reverse rotating ballance shaft" or in my case I resolved to set the Rev limit at 11,500 RPM..
This is interesting, since I have always loved fault analysis , and has been my forte . What were the G-forces that were encountered?
I have no idea what the people you spoke to were talking about in regards to the " engine case" not handling the g-force. The metal of the case doesn't know or care what the g-force is or which direction it is coming from..Even at 2G the deflection force is only twice the weight of the engine, say 1k pounds.
There are forces in the tens of thousands of pounds acting on the metal of the engine and 1k lbs from the g-force in a turn would be like a gnat on an elephant..
Did the bearing journal turn blue from lack of lubrication? I suspect they are talking about the "sump design" can't handle the "G-Force" and therefore led to failure..
Yes there is a cure for this..
Porschetech, sounds like you are the perfect person to speak to this with actual mechanical knowledge and I’d be interested to hear your take.
To answer your questions, yes, I was referring to the sump and oiling capacity of the engine, not the case structure. I was told the sump and the manner in which the oil was delivered internally were the Achilles heel and that they could be improved but not solved. The engine that failed had the LN deep sump with metal baffles, which I was warned would be best available but likely still not adequate for high G’s. To answer your G’s question, I’m not sure; will have to track down that data on an old *** computer somewhere in the garage. I recall possibly 1.2G on the banking and >2G in the braking zone (160 to 50mph), but honestly I have no clue. That could be utter nonsense my brain made up.
Porschetech, sounds like you are the perfect person to speak to this with actual mechanical knowledge and I’d be interested to hear your take.
To answer your questions, yes, I was referring to the sump and oiling capacity of the engine, not the case structure. I was told the sump and the manner in which the oil was delivered internally were the Achilles heel and that they could be improved but not solved. The engine that failed had the LN deep sump with metal baffles, which I was warned would be best available but likely still not adequate for high G’s. To answer your G’s question, I’m not sure; will have to track down that data on an old *** computer somewhere in the garage. I recall possibly 1.2G on the banking and >2G in the braking zone (160 to 50mph), but honestly I have no clue. That could be utter nonsense my brain made up.
Yes, the factory " Integrated Dry Sump System" and " Air-Oil Separation System" doesn't live up to expectations at all.
You can start to have issues at about 1G on the factory stuff, and this can occur even on the street...
I suspect your 1.2G on banking is about right.
I have already shown the UIDS at 1.65G on turns ( and this is without the help of UAOS) , and am still looking for someone with a car that can do more G than this for testing and improvements......such people/cars are hard to find...
Last edited by Porschetech3; 08-31-2022 at 02:42 AM.
Spoke with a number of well known engine builders on the third rebuild and the consensus was it’s an engineering fault with the case that cannot be solved. .
99 C2 with LS1 swap. SNS Stage 2 cam, ported LS2 intake, LS3 throttle body and injectors. 180 degree headers, Dr Gas mufflers, all 3” tubing. Tune is still rough, I’m taking it to another tuner here because it idles rich.
99 C2 with LS1 swap. SNS Stage 2 cam, ported LS2 intake, LS3 throttle body and injectors. 180 degree headers, Dr Gas mufflers, all 3” tubing. Tune is still rough, I’m taking it to another tuner here because it idles rich.
393rwhp
Thanks dude ! Spicy... Lot of power for minimal mods, must be a lot of fun in a relatively light weight early chassis. Throw the re-tune number up after you get it. Will be interesting to see how much more it has in it, lean is mean just not too lean.
@Triple Black Thanks a lot for sharing ! Is the yellow (275WHP) pre and green (291 HP) post tune, assuming yes ? Do you what MFG Dyno this was on ?
Those TQ drops of 25ish FT/LBS at 2.5K and 3.5K RPM's are weird. Couple of the other users have the similar thing, wonder why that is. I think in your case the scaling of the graph plays a part but those are 2 pretty big dips...
08-27-2022, 12:39 AM
. Sent a rod through the bottom of the motor. Result was the harmonic issue the m96 case creates when spinning motorsports parts faster and lighter than stock. Fully blueprinted motor with JE pistons. Still no global fix identified.
