[ktgeorge]

I have read about turbo conversions on the net but I was wondering if boring out the stock engine so that it was around 3.3L was practical on this block?



It might be a less expensive way to get more HP when rebuilding was being considered for an engine with many miles on it.





Thanks



Kimon George

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[BruceWard]

Huntley did this, but they are out of business now. There is a long discussion on their 3.4 which if I remember correctly they claimed produced 340 BHP on 968.net http://65.61.16.109/forum/topic.asp?TOPIC_ID=4871 .



I have not been able to find any vendor that can do this inexpensively. Boring, sleeving, stroking, replacing the pistons and rods gets very expensive. Then it may need an engine management system on top of the work inside.



I believe that you would get more HP & Torque for a lower cost with one of the bolt on super charger kits.

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[Leonard]

I agree Bruce. So will we be seeing your car with a supercharger anytime soon??

<img src="/forum/images/smilies/968/biggrin.gif" class="smilie" alt="" />

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[flash]

horsepower per dollar, forced induction reaps better rewards



boring will add torque and horspower, but can cost revs if it gets near terminal piston velocity



based on simple hp per liter displacement, a 3.4 oversize should bring about 32hp - this is in line with what i have seen on most overbore projects, and is in concurrence with a couple of guys i've talked to who have done it - the power goes up directly proportional to the displacement increase



all that good news aside, on a 3.4, there are a lot of complications with cooling and mixture control and emissions, so, for a street car, this is not necessarily the way to go



however, a 3.2 with some other mods could come in about 10 grand and get you to that magic 300hp mark fairly easily, add about 16hp, only a couple of grand to the project, and probably still pass emissions, which makes it more cost effective than forced induction, which in the end, would likely run at least 20 grand



something that most people fail to factor in when considering high output projects, is that the motor need to be rebuilt anyway - they are only looking at the bolt on costs, which are only about half the total cost - only someone who just wants to throw away money would high boost turbocharge or supercharge a motor with any real miles on it - take away the common rebuild cost, and suddenly the overbore gets pretty economical, as long as your expectations are reasonable



carrol said it best - no substitute for cubes



but there are very real limits to the power available through that route

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[ktgeorge]

[quote name='flash' date='Jan 27 2006, 10:13 AM']horsepower per dollar, forced induction reaps better rewards



boring will add torque and horspower, but can cost revs if it gets near terminal piston velocity



based on simple hp per liter displacement, a 3.4 oversize should bring about 32hp - this is in line with what i have seen on most overbore projects, and is in concurrence with a couple of guys i've talked to who have done it - the power goes up directly proportional to the displacement increase



all that good news aside, on a 3.4, there are a lot of complications with cooling and mixture control and emissions, so, for a street car, this is not necessarily the way to go



however, a 3.2 with some other mods could come in about 10 grand and get you to that magic 300hp mark fairly easily, add about 16hp, only a couple of grand to the project, and probably still pass emissions, which makes it more cost effective than forced induction, which in the end, would likely run at least 20 grand



something that most people fail to factor in when considering high output projects, is that the motor need to be rebuilt anyway - they are only looking at the bolt on costs, which are only about half the total cost - only someone who just wants to throw away money would high boost turbocharge or supercharge a motor with any real miles on it - take away the common rebuild cost, and suddenly the overbore gets pretty economical, as long as your expectations are reasonable



carrol said it best - no substitute for cubes



but there are very real limits to the power available through that route

[right][post="15146"]<{POST_SNAPBACK}>[/post][/right][/quote]

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[ktgeorge]

[quote name='ktgeorge' date='Feb 13 2006, 02:39 PM']



Ok, 10k or so to get to 300hp seems acceptable. if I have it bored out to around 3.2 what are the other mods you mentioned to get to 300 and do you have any reccomendations as to who.





Thanks



Kimon

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[flash]

it would be the same kinds of things we are already employing



i plan on building my own, just as i always have, so no, i don't have a recommendation for you

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[bob blackwell]

Kimon, contact Pete Fitzgerald at RS Barn. He has been working on modifying the 968 engine without adding supercharger or turbocharger. He is having some success with cylinder head work, new camshafts and exhaust systems. the quality of his products that we saw last year at the 968 Celebration in Washington D.C. was outstanding. Pete is a lot of fun to talk with too, good luck, Bob Blackwell.

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[968gene]

LS-7...any questions?

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[flash]

lol - drove a buddy's viper a couple of weeks ago - reminded me of why i think i don't really want a V8 in this car - tons of fun, gobs of power, but a real mess to drive fast

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[968gene]

LS-7 is a dry sump (I think), this should sit lower in the car and has all the power you need without the aded weight.

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[flash]

the problem wiht the viper is there is just too much power for the car - it is constantly fighting between understeer and oversteer - my concern is that this car will do exactly the same thing - it has not been difficult to induce those conditions on my car, and though i have reduced the weight a lot, i have not added that much power - it is showing me where the difficulties are going to be though



the factory suspension and drivetrain connections make it a great road car for its balance, but start talking about serious increases, and then you have to rethink the setup - as loose and sloppy as these cars are in stock trim, i have a hard time imagining really driving fast much beyond 300ft/lb without serious suspension mods



i think a 3.2 bore, in conjunction with the other things being talked about here, (tuning, intake, exhaust, cams) should easily produce a reliable motor of about 300hp and 275ft/lb - that is probably about the best setup this car could ask for with a stock or reasonably stock suspension and setup



the cost is not going to be small for the power increase, if starting from scratch, but if you have to rebuild anyway, the increased cost is not that much



this is very likely the route i will take

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[bob blackwell]

Flash, when you look at the output of the Porsche Factory 968 Turbo S and Turbo RS they had 304 HP and 337 Hp respectively. with the suspension and brake improvements they made there was no report of handling problems of any kind. While 500 HP might create problems, I don't think anything up to 350 HP will be a problem at all. We are not exploring "new ground" here. good luck, Bob Blackwell.

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[flash]

i think we're on the same page here, but may not realize it



i don't think they were stock suspensions - pretty sure they had the M030 setup as a minimum - they also had bigger tires and wheels - also, i've read in reviews about the higher output model, they did say, while very fast and fun, that it was a bit loose when pushed



that being said, 350 is very doable with little effort, like basic tire/wheel/strut,swaybar,shock changes, but that's not stock - i think 300 is about the limit stock



if you want to go past 350, then, there is a lot more that really should be done, but there are plenty of guys out there with 400 that seem happy - i'm just not sure they are driving any faster



you run track - you know what i mean - more power does not neccessarily mean faster

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[S_Cal968]

I would have to disagree, more power is always faster. It has more to do with the capabilities of the driver and the setup of the car.

I can floor my 968 right off the line, I can't do that in my muscle car [w/ a locker], I'll fry the tires. It's knowing when to apply the power....

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[flash]

i was referring to a road race course, where this car is more suited - there, more power often does not mean faster, especially in the extremes, and can easily mean slower - brakes and tires win races - not power



before reading the folowing, keep in mind we are talking about running on the edge - sitting at or near redline, and pushing the car hard in every corner - we are not talking about a 5-6k weekend poke along



but you are right - the setup is key - getting the power to the ground is the task - that is the problem with the 968 stock suspension - i have to be very careful off the line, and a little in the corners, or i break the tires VERY loose (and i have 285s back there)



it was pretty bad with the stock 255s and stock suspension and no lsd - no way would i have put more power in there - it's not bad now, and i can probably add another 25, but that's it - then i need stiffer springs, and probably rear unequal length control arms - the rear squat is sucking up too much power - i'm probably losing a full tenth of a second 0-60 to the squat now, but if i stiffen it up, then i'll have oversteer - it would be worse with more power - this also applies to full power exits, especially off camber



the beetle/rabbit suspension just isn't up to the job

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[PcarFan]

why are we talking about a viper??? its a 10 cylinder car that produces less power than the new z06..and the new z06 doesnt have any problems with being to much power for the car.... but i agree an LS7 would be too much for a 968 but a ls2 would be a great motor to put in the 968.. 400hp and easily tuneable

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[flash]

i was citing that as an example of too much power for the setup of the car - i think the 968 would exhibit many of the same kinds of poor handling characteristics if it had over 300 hp on the stock suspension



the viper is fun, but a real handful when you get on it - i think the 968 would be too if it had over 300 on a stock setup - i am pretty sure that even the setup i have now would see limits not far from there, and i would really need stiffer rear springs and better shocks to match



a quick test is to take the car through an .8g plus turn and stand on it at 5k - if it plants and pulls, it's fine, if it ducks, squats, or slides on either end, you're over the limit - kids don't try this at home (or on a local back road) - track only please



p.s. - the new vette stomps the viper in head to head road course matches for exactly that reason

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[968gene]

http://www.motortrend.com/av/112_0506_ls7e...ideo/index.html

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[S_Cal968]

Bob,

I wasn't referring to any specific mode of racing [weekend run or otherwise]. I mentioned my muscle car to provide contrast.

Cars that run at Road America don't win with just brakes & tires, they require a powerful engine. And, as noted, I specifically metioned "set up"...

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