trying to learn some more about the 968
09-09-2006, 05:37 PM
#17
It has nothing to do with the intake manifold itself...its a great piece. But the dual resonance system makes our intake manifold very deep, and there simply isn't enough space. I looked into doing an exhaust side turbo, but there really isn't enough space anywhere. The only reasonable space is under the intake manifold, 951 style. Here is a picture to help you maybe see a little better.
https://rennlist.com/forums/attachme...d=122105&stc=1
Thats with only a moderately sized turbo. You only can go so big over there, but an new intake manifold has to be made. The things to consider though is where/what kind of power you want. If you want a lot of torque, then running a very similar to a 951 spec intake manifold will give you that. If you are going for raw power, short, quick runners for the intake manifold is what you are looking for. By cutting the OEM 968 manifold we don't have to worry about intake angles and such. The hardest part is welding the tight spaces and it being aluminum.
Wes
https://rennlist.com/forums/attachme...d=122105&stc=1
Thats with only a moderately sized turbo. You only can go so big over there, but an new intake manifold has to be made. The things to consider though is where/what kind of power you want. If you want a lot of torque, then running a very similar to a 951 spec intake manifold will give you that. If you are going for raw power, short, quick runners for the intake manifold is what you are looking for. By cutting the OEM 968 manifold we don't have to worry about intake angles and such. The hardest part is welding the tight spaces and it being aluminum.
Wes
09-09-2006, 06:21 PM
#18
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lol - i know that one all too well - we did a twin turbo 240Z that just seemed endless - fast as heck, but a handfull to keep together - we'd fix one thing, and it would break another - finally got the engine working right, and stopped blowing rear ends and trannies, and then started ripping out the rear suspension - the car, which started out as somebody's idea of a really hot street car, became completely undriveable on the street in the end, and became a race car - did rpetty well until it stuffed a wall - still not enough brakes for the power
a lot of this is the problem with our car too - the rubber bushings and soft springs are not up to the job of more than 325 tops - even with what i have now, they were all showing themselves to be a weak link - the car was a mess to drive really fast - in stock trim it is a mushy setup - it was balanced and all that, and very predictable, and very nice for the road, but not for handling power or going really fast - no worrries - it is a road car and not a sportscar after alll - i'm currently at twice stock stiffness, with lots of goodies, and still think i'm too soft for the power - getting closer though
these things have to be thought about when doing such a project - to handle 400hp, and actually use it, you can figure in about 4 grand in suspension and braking to do it right - heck, most people find out in a hurry on their first day at the track, that they can't fully use the power they have now, let alone more
these cars are all about the corners, and to do that, with that much power, you need to set the rest of the car up to work with it - otherwise, if you are just looking for a stoplight racer, you should just get a GTO or a mustang, and not sweat it
i guess it comes down to how you will use the car though, and what the motivations are - if you aren't going to drive it hard and fast, then you won't see the problems - but then, why would you turbocharge it? that's an entirely different philisophical question for another day
anyway, that's why i think that a turbo on this car, that makes 400hp, will likely cost more than the car - it's not just the turbo - it's the prepping of the engine to handle it, the suspension upgrades, the brake upgrades, and other miscellaneous junk - it all adds up
fun for sure, from beginning to end, and i applaud those who undertake this endeavor, but it is not for the lighthearted
a lot of this is the problem with our car too - the rubber bushings and soft springs are not up to the job of more than 325 tops - even with what i have now, they were all showing themselves to be a weak link - the car was a mess to drive really fast - in stock trim it is a mushy setup - it was balanced and all that, and very predictable, and very nice for the road, but not for handling power or going really fast - no worrries - it is a road car and not a sportscar after alll - i'm currently at twice stock stiffness, with lots of goodies, and still think i'm too soft for the power - getting closer though
these things have to be thought about when doing such a project - to handle 400hp, and actually use it, you can figure in about 4 grand in suspension and braking to do it right - heck, most people find out in a hurry on their first day at the track, that they can't fully use the power they have now, let alone more
these cars are all about the corners, and to do that, with that much power, you need to set the rest of the car up to work with it - otherwise, if you are just looking for a stoplight racer, you should just get a GTO or a mustang, and not sweat it
i guess it comes down to how you will use the car though, and what the motivations are - if you aren't going to drive it hard and fast, then you won't see the problems - but then, why would you turbocharge it? that's an entirely different philisophical question for another day
anyway, that's why i think that a turbo on this car, that makes 400hp, will likely cost more than the car - it's not just the turbo - it's the prepping of the engine to handle it, the suspension upgrades, the brake upgrades, and other miscellaneous junk - it all adds up
fun for sure, from beginning to end, and i applaud those who undertake this endeavor, but it is not for the lighthearted
09-09-2006, 08:17 PM
#19
Not at all Raj, no offense taken. My post really did need a little clarification there.
Best,
-Mirror
Best,
-Mirror
Originally Posted by 968TurboS
Mirror, that was not meant for you but instead was a response to this statement,
Sorry, if I offended you in any way.
Regards.
Raj
Sorry, if I offended you in any way.
Regards.
Raj
09-09-2006, 11:40 PM
#20
Flash,
I agree that brakes, and most importantly suspension needs to be taken into account. I don't/didn't add those into my cost because they are already done. The engine is the last thing on my list. I would definantly agree that I will be in well more than I paid for the car when I am done with everything, but not in the turbo ALONE. I mean my wheels/tires were close to half my cars value, esp...if you go with KBB value. Brakes another $1500, suspension is at about $2000, you get the idea. But in the end, those are all items that would be taken care of. Springs sag over time, shocks blow seals. I would venture to say that to replace every item to OEM I would be in more money. As to the tracking, I definantly feel that my car has a lot more to give. I mean I can get it down to running within 2 seconds every lap, so either I need to become a better driver, or the car can offer more. I find myself weak on the straights, but great on the braking/corners...easily taking on almost any 964/993 in that catagory. As soon as it opens up though I am weak. I am sure if I was cam'ed, custom chiped, headers, etc...I would be fine. But for that cost I will be in my turbo. I am building a linear, NA type powerband. I will see peak power around 6500, with a smooth curve all the way up hopefully. My car will definantly be tracked, but mostly I am looking for more power to just enjoy. Something to toy with on my way to work.
Wes
I agree that brakes, and most importantly suspension needs to be taken into account. I don't/didn't add those into my cost because they are already done. The engine is the last thing on my list. I would definantly agree that I will be in well more than I paid for the car when I am done with everything, but not in the turbo ALONE. I mean my wheels/tires were close to half my cars value, esp...if you go with KBB value. Brakes another $1500, suspension is at about $2000, you get the idea. But in the end, those are all items that would be taken care of. Springs sag over time, shocks blow seals. I would venture to say that to replace every item to OEM I would be in more money. As to the tracking, I definantly feel that my car has a lot more to give. I mean I can get it down to running within 2 seconds every lap, so either I need to become a better driver, or the car can offer more. I find myself weak on the straights, but great on the braking/corners...easily taking on almost any 964/993 in that catagory. As soon as it opens up though I am weak. I am sure if I was cam'ed, custom chiped, headers, etc...I would be fine. But for that cost I will be in my turbo. I am building a linear, NA type powerband. I will see peak power around 6500, with a smooth curve all the way up hopefully. My car will definantly be tracked, but mostly I am looking for more power to just enjoy. Something to toy with on my way to work.
Wes
09-10-2006, 01:27 AM
#22
hmm...1099 foundation...beyond me. Got your PM over on 968forums. My budget has an engine rebuild in it, but I would like to see what stock is capable of. I mean if I can reliably push 400hp, then that says a lot. If I get to 500hp before exploding, then we would now know the abilities better.
Wes
Wes
09-10-2006, 07:25 PM
#23
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it's a CHP thing - gets you out of tickets - very hard and expensive to join - no idea if it's nationwide though
just to be clear, it's not upgrades i'm concerned or talking about - high boost forced induction puts a lot of extra load on bearings, valve seals, rings, seals, etc - a used motor will show the weak points in a hurry - i would just refresh it to start - then if you blow something, you know it was a weak point, and not a worn component
good luck though
just to be clear, it's not upgrades i'm concerned or talking about - high boost forced induction puts a lot of extra load on bearings, valve seals, rings, seals, etc - a used motor will show the weak points in a hurry - i would just refresh it to start - then if you blow something, you know it was a weak point, and not a worn component
good luck though
09-10-2006, 10:41 PM
#24
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I don't think anyone here is talking about a high boost forced induction set up though...
and boost really doesn't signifcantly increase load on those components that much... certainly not as much as increasing the redline, and there seem to be plenty of people out there that have no qualms about bumping the redline up. The peak inertial load on the bearings from bumping the redline up to 7800rpm is about equivalent to what running around 400bhp from a turbo would result in.(inertial load increases with the square of the rpm increase, where as doubling the power output through a turbo results in an 18-20% increase in peak cylinder pressure)
how many of the chips out there raise the redline to around that range.
and boost really doesn't signifcantly increase load on those components that much... certainly not as much as increasing the redline, and there seem to be plenty of people out there that have no qualms about bumping the redline up. The peak inertial load on the bearings from bumping the redline up to 7800rpm is about equivalent to what running around 400bhp from a turbo would result in.(inertial load increases with the square of the rpm increase, where as doubling the power output through a turbo results in an 18-20% increase in peak cylinder pressure)
how many of the chips out there raise the redline to around that range.
09-10-2006, 11:42 PM
#25
Sax,
I agree that more load will be seen at higher rpms, actually cylinder pressure typically starts to lessen. Its peak is at peak torque, so regardless, increasing torque increases cylinder pressure...if that makes any sense. I troll EFI101 forums a lot, and there was a huge discussion about this. An F1 engine at 19000 rpms has less cylinder pressure than a Supra 2JZGTE at 30psi, and 900hp. Both are at 900hp, just different points. So yes, 7800rpms puts a large stress, I think doubling the torque would put as large if not a larger stress. Just my opinion though.
To answer your question though, there isn't much gained by going to 7800rpms. Peak power is well below that, and the transmission is close enough that 7000-7200 is all you need. My car is chipped to 7800 and I have YET to hit my redline. Cams, probably...but stock not worth it. I would have been just as happy with the 7200 rpm chip over the 7800.
I still don't 100% agree that the stresses exerted will destroy a higher mileage engine. These engines are built well. I mean, my headgasket will be replaced, rod bearings already one, intake manifold and exhaust manifold gaskets will be new, probably will get the head completely redone and ported, so the only real thing left are the main bearings and rings. I expect some blow through, but my current compression is great. So I am still unsure of what you are expecting to go wrong...I mean if there is something I am missing, I would love to know about it so I can take care of it. You and Raj have been in the game a lot longer than me, so I take your opinions seriously.
Wes
I agree that more load will be seen at higher rpms, actually cylinder pressure typically starts to lessen. Its peak is at peak torque, so regardless, increasing torque increases cylinder pressure...if that makes any sense. I troll EFI101 forums a lot, and there was a huge discussion about this. An F1 engine at 19000 rpms has less cylinder pressure than a Supra 2JZGTE at 30psi, and 900hp. Both are at 900hp, just different points. So yes, 7800rpms puts a large stress, I think doubling the torque would put as large if not a larger stress. Just my opinion though.
To answer your question though, there isn't much gained by going to 7800rpms. Peak power is well below that, and the transmission is close enough that 7000-7200 is all you need. My car is chipped to 7800 and I have YET to hit my redline. Cams, probably...but stock not worth it. I would have been just as happy with the 7200 rpm chip over the 7800.
I still don't 100% agree that the stresses exerted will destroy a higher mileage engine. These engines are built well. I mean, my headgasket will be replaced, rod bearings already one, intake manifold and exhaust manifold gaskets will be new, probably will get the head completely redone and ported, so the only real thing left are the main bearings and rings. I expect some blow through, but my current compression is great. So I am still unsure of what you are expecting to go wrong...I mean if there is something I am missing, I would love to know about it so I can take care of it. You and Raj have been in the game a lot longer than me, so I take your opinions seriously.
Wes
09-11-2006, 12:02 AM
#26
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I wasn't pulling those numbers out of no where... Doubling the torque production of the motor through forced induction creates an 18-20% increase in peak cylinder pressure. Because load increases exponentially with rpm increase, this same increase in peak cylinder pressure occurs to the motor when moving from 7200 to 7821rpm(18% peak cylinder pressure increase) to 7887(20% increase).
The point about moving the rpm up to 7800rpm wasn't that it helped anything, but that it's a very common thing for people to do without much concern for the consequences.
Have a compression and leak down test done... if the results of both come back positive, boost away.
Comparing a turbo supra motor and an F1 motor is a bit of a moot point as they're completely different motors... and while it's certainly interesting, doesn't help much when discussing turboing the 968 motor.
The point about moving the rpm up to 7800rpm wasn't that it helped anything, but that it's a very common thing for people to do without much concern for the consequences.
Have a compression and leak down test done... if the results of both come back positive, boost away.
Comparing a turbo supra motor and an F1 motor is a bit of a moot point as they're completely different motors... and while it's certainly interesting, doesn't help much when discussing turboing the 968 motor.
09-11-2006, 12:12 PM
#28
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Buy a cheap 928 ($6K-$9K), install a supercharger for $5K (parts only) or pay another $5k and have it installed and you'll have luxury and performance easier and at a cheaper price than the 968 seems to be able to achieve. However, the 968 is the more desirable conversion and would hold it' value better. Add $10 to a $6K 928 and you'll probably end up with a $10K car. I'd hope the turboed 968 would hold its modified value better.
Harvey
Harvey
09-11-2006, 01:12 PM
#29
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what i meant by high boost is anything over .5 bar - 14psi is high boost
i'd at least replace the bearings - every stroke will see more force, thereby increasing wear - it is extremely common to spin a bearing when attempting something like this - the valve seals also often blow from the increased pressure
personally, i would not want to have to go back in - i'm the "do it once, and do it right" type
hypothetical question - at 200k, would you take the engine, as is, and race it, without expecting problems?
i'd at least replace the bearings - every stroke will see more force, thereby increasing wear - it is extremely common to spin a bearing when attempting something like this - the valve seals also often blow from the increased pressure
personally, i would not want to have to go back in - i'm the "do it once, and do it right" type
hypothetical question - at 200k, would you take the engine, as is, and race it, without expecting problems?
09-11-2006, 03:07 PM
#30
Flash,
At 200k miles, I wouldn't compete in a driving event. Thats sustaining + 5000rpms, mostly 6-7500rpms for a couple of hours. I am talking 4-7000rpms for maybe 15-20 seconds under 10psi. I think the stresses are completely different in what you are speaking. I run my 170k mile car to 7000rpms atleast daily. Its hard to not do it, and it just keeps wanting more.
Wes
At 200k miles, I wouldn't compete in a driving event. Thats sustaining + 5000rpms, mostly 6-7500rpms for a couple of hours. I am talking 4-7000rpms for maybe 15-20 seconds under 10psi. I think the stresses are completely different in what you are speaking. I run my 170k mile car to 7000rpms atleast daily. Its hard to not do it, and it just keeps wanting more.
Wes