I would have thought that peak hp really doesn't matter, it's the torque you have to stop with your brakes. Seeing as an 300hp V8 can probably produce 300lbft at 1000-2000 rpm and a 300hp 4-cylinder won't be even close to that torque at the same rpm. You have a lot more torque to stop in a V8 than a 4-cyl and that must demand bigger brakes.

Same argument for suspension upgrades, the extra low down torque in a V8 will affect the chassis much more than the same hp 4-cyl engine due to much higher torque coming into play earlier.

How much torque are you producing when you let off the throttle to brake?

C'mon...

9FF - correct.

as for a 4 cylinder and torque capabilities, if you had a roots blower, you could make that torque at 2krpm. with a centrifugal you'll only get about 220 at 2k, and won't see peak until 4k. with a turbo, you won't get diddly until over 3k, but you could get more at peak.

it took quite a bit of time and money to get my blue 968 to be able to handle the power it has now, and even now i am at the limits of the car. a bigger, heavier engine (yes, the LS engines weigh more), with more torque, would need even more.

id love to feel the torque of an NA 3.0 8v...

I would ask that you please don't encourage and reinforce thoughts that are not fully formed. How can you say this is correct: You need bigger brakes to stop a v8 because it produces more torque????

No. Absolutely incorrect. The output of the engine for HP/torque does not translate directly to brake requirements. Brake selection is better when considering the total mass you are attempting to slow (entire weight of the vehicle)and also the frequency of brake operation. Engine output is not primary in considerations.

You need brakes to match your driving style regardless of the engine swap. It's a popular modification to put smaller diameter rotor brakes on quarter mile cars so you can run a smaller wheel and thicker sidewall tires. If you are overrunning stock 944 brakes on the street then you need to slow down.

I'm aghast at the misinformation here. Absolutely ridiculous.

If only those 2.7 heads were not so expensive. It would be fun, but i think the 968 would still out torque it due to the variocam. The S2 has some really good grunt, even down low and then revs so quickly due to the heads ability to flow. Its so fun! I say this and i'm at 6000ft and loose something like 18% of my power to the altitude, if i took this car to sea level i'd be in for a treat. I know my S lost 25hp on the dyno in denver vs its altitude corrected number. It put down 152hp altitude corrected vs its real number of 128, this was at the wheels.

It was more a query than a fact I was posting, that's why I started the post with "I would have thought". We're not all physics geniuses here, it's a forum, we query things and ask questions, and don't expect to be ridiculed because we don't know everything, thanks for your input.

Not directed at you - asking questions is okay. I agree questions and answers are why we are here. When the answer is completely wrong we need to make sure the bs is nipped in the bud. That method will make us all smarter.

So to clarify the brake query, the only reason you need bigger brakes for a LT/LS conversion is because of the weight difference?

944na to LT/LS is 150-400LB more weight
951 to LT/LS is 50-200LB more weight

So you do need to upgrade brakes and probably suspension, correct?

The weight difference for an Ls swap is 50lbs.

Would you upgrade brakes and suspension for that amount? Maybe. If you were dialing in a suspension for a specific track. Necessity? No.

i dont know what it is, but every 968 ive ever driven feels slower on the low end than any S2...i dont doubt they are faster overall but for going around town...id take an S2 any day.

S2 engine swaps have built some successful 944 race cars. I know that to be true.

Always thought these engines started with Buick?

More tq might just be a number on a page but I believe what he's saying is that if you have it at your feet, you'll use it more readily. So if you have the low down tq of an n/a V8 you might be prone to be travelling faster at the next stop light (wherever) than if you had to reach your peak (and lesser) tq at 5000 rpm. You may not be so inclined to rev the rings out of the motor to make it reach 100 mph with a smaller n/a motor. Just hypothesising here. Nobody is saying you need bigger brakes to slow down the same mass..but if the mass is travelling faster then perhaps you might. Same as adding stickier tyres. How would this necessitate bigger brakes? You go around the corners faster therefore reach your next corner at a higher speed. You brake at a certain point to pull you up in time to make the next corner or come to a complete halt. The brakes don't care about what motor you have up front, but they are used proportionally to the speed you're travelling at. With higher earlier tq you may just be going faster, sooner.

As for justifying a V8 swap on the basis that it produces 300bhp...puhleez...what would be the point? That would be just another ****box you see advertised on Craiglist...and I'm not even from the US. If you are going to do the swap, you want at the very least 400bhp and then, yes, you should factor in for the better suspension, brakes blah blah blah....

That's more logical and thank you for the thoughtful reply. It all comes down to how you drive which has to do with the driver not the engine under the hood. The initial implication that a v8 swap required such and such mods over the hot rod 4cyl is what we've just debunked. The weight similarities could nearly be eliminated with a battery relocation or smaller unit. The difference is so small that between drivers you might see more of a difference (driver Bob weighing in at 240lbs after a healthy breakfast, driver Tim weighing in at 160lbs after visiting the port-o-let).

I had a 1.8L 4cyl GTI in high school that I cut my teeth on that is similar mass to a 944 (~2600lbs). I could get those brakes glowing and smoking on the back roads hauling ass. I didn't need an increase in HP to require bigger brakes I only needed to drive like a maniac on public roads. It took work and recklessness to get those brakes hot.

"I have a faster car so I'm going to automatically drive faster." We're not in highschool anymore (well, maybe a few of us literally are) so hopefully we know better than to run a Porsche to the mechanical limits of the brakes on public roads. The brakes these cars come with are not 9.1" solid rotors with miniature drum brakes in the back like my similar weight GTi example above. These Porsche cars come with decent brakes relative to other makes. With these better, OEM Porsche brakes, it will take far more aggressive and prolonged driving than the canyon/gulf runs and it won't matter which engine you have if the power output and weight is similar.

Don't forget Lapkritis, the 50lbs difference is a comparison between the 951 and all the turbo accessories to the GMV8 and all accessories. There's folk out there putting the V8 in the na which is about 100-200lbs lighter than the 951 depending on the MY. iirc an LS1 in an early na adds nearly 200lbs to the cars weight. Definitely need to work the suspension and brakes in that case.

Please share your data source for the 200lbs number. I have an 8v here on the stand with balance shafts and all accessories. It's HUGE and heavy.

Have you worked with an LS before? They're also aluminum. They're light and relatively compact. They're easy to modify and perform superiorly to the 944 powerplants across the board and at a lower cost.

Even if we arrive at 200lbs difference eventually (which I doubt when comparing apples to apples)... my point remains. It's a small difference in weight. The point that the number of cylinders somehow relates to the size of brakes required is complete hogwash. Take a 500hp 4cyl swap in a 944 with LIGHTER weight than the 944 engine. Should I go both smaller brakes then? The logic doesn't work. This topic is done.

lapkritis - what i was agreeing with was 9ff's comments about the chassis.

as for brakes, if you drive faster because of more power, as EVERYONE does, you need more brakes. it is as much about speed as it is about weight. that's why 951s have bigger brakes than a regular 944, though they are nearly identical weights.

333 - thank you - that's exactly what i was getting at

re: weight difference, it's more like 100lbs when you are all said and done, using the all aluminum version. you have to take what is on the internet with a grain of salt. american engines are weighed without intake, or any accessories bolted on. german engines are weighed complete. also, the increased cooling capacity required, and added exhaust weight, and other such items, all factor in. in the end, you gain about 100lbs up front.

How about a turbo volvo 5 cylinder? I don't know anything about them other than a friend had one that was impressively quick after he did some mods to it.

The 50lb difference commonly banded about it the overall difference in car weight between a 951 with a 4cyl and a 951 with an LS1. They are comparing engine/turbo/piping/intercooler, etc to the LS1 weight with all accessories and it's about right. The na doesn't have all the turbo accessories to start with, it's a lighter car by about 100-200lbs overall depending on MY compared to the turbo.