V2Rocket

your money would likely be better spent with the arao heads because those 4v heads will outflow even the best 2v heads. especially if you cam/spring it to run at higher rpms (8000rpm is not hard with an sbc/LS so long as it has strong parts)

CarbonRevo

Must remember, the 968 is lighter than a C6 Vette. Not by much, but it is a difference. And before you say it, the LS2 will surprising not add very much weight to the 968, if any.

I would say with a simple cam and nice tune (looking at over 400whp), the car could easily pass 180mph. Your goal of 190mph is up there.

The LS2 is really a monster of a motor. I have very simple bolt ons and tune on my LS2 blazer and it put 360whp/380wtq down. Good for 145mph on a good day!

odurandina

i think Spencer (V2 Rocket) is right.

i would have to send the heads out for work.

i'll ask the nice folks at Total Engine Airflow what can be done but, i would only be changing out the cam for a top speed pass.

part of the "picture" includes having a silky smooth idle.




a splash of nitrous would, no doubt, help. no disrespect but, you'll see in time that most guys here frown the use of the bottle. i'm not yet driving a very potent Porsche, and i don't race. but i can tell you one thing. you won't be hearing too many kind words about nitrous around here.




since we're on the topic of speed i thought i'd copy a couple of interesting points the guys made on the 944 Turbo forum.

on the subject of ratios....



.

odurandina

Chris,

running the new gears, the car will see about 5,885 rpm at 190 mph, like, 6040 rpm at about 195 mph....

these calculations are "good," based on the 818 revolutions per mile for the dunlop 275-35-18s.

many people run shorter tires, ex: (a 295-30-18 is about 24.8")... running the larger 25.6" tires seems to improve the ride significantly, as i'm sure you know, and gives exactly 25 mph per 1000 rpm in the stock 6th gear.... so the speed/rpm numbers i've provided would be correct for the slightly larger tires i'm running....





968 6 Speed;

the 01e class of gearboxes have been run up to 700+ hp without failures... but in the case of a significant hp upgrade, not only is 1st gear too low, they're all basically "in between" gears.... in this post i'm going to be assuming that we're running a larger tire -- like a 275-35-18 (25.6" diameter tire)... two very good tire sizes for v8 swap cars are 285-35-18 or 275-35-18 such as XSChop and myself are both running.

here, the fix would be a taller R&P in the range of about 2.80~2.85:1... i've had a few conversations with Roger at California Motorsports (CMS) in Lake Havasu, AZ who in turn, has consulted with Albins Gear several times... after doing the research Albins determined that only a 3.00 or 3.10 R&P can be manufactured that will get close to the ideal "2.85:1" ratio for a street car... other gearsets including a 3.30 or 3.446 (the 968 Turbo S ratio) for a track/drag/street car can be made up. *(the 3.0 is the lowest R&P that is close to ideal but can still be set up for the 968 box).... the cost for one-off gearsets purchased through Roger are about $4,000. not bad considering....

either of these available ratios would be a better choice for a high torque/hp V8 (than the stock 3.78 ratio) for making gears 1-6 more useful.... and installing one of these combos (i believe the 3.446) results in a similar sequence as you have with 1-4 on the 944T box... however, i just couldn't see doing it. and not because of the cost ($4,000); but rather, because the final ratios of 5th and 6th still wouldn't end up being high enough for everyday driving... considering my investment in the V8 i will run is fairly enormous, my rpms on the faster secondary roads and slower state highways wouldn't be low enough to make maximum use of 5th gear, and my rpms between 65 and 100 mph on (interstate highways) wouldn't be cut down low enough in 6th gear....

hats off to Roger at CMS who first pointed out to me the importance of not just changing 6th gear but 5th as well, and he was absolutely right. not having the right gear for driving in traffic between 40 and 60 mph would really suck, as the 968 box's 5th is way to low....

after consulting with another Audi transmission expert (Scott Dewitt owner of Advanced Automotion in Corpus Christi, TX), i learned that what we need are 5th and 6th gearset options out of the Euro 2wd A4 diesel transmission... but, because the 2wd 01E never came to USA or Canada so you cannot source 01E 2WD gears through audi's North American parts distribution network. some (myself included ) have erroneously stated that the .680 6th gears found in many of the Audi A4 and S4 gearboxes over here in the states will fit the 968 boxes. but not so... these are of the 4WD variety, and will not fit any of the 2WD 01e's, and therefore not fit the 968 box... the 2WD box and 4WD gearbox share the same input shaft, 1-2 gears, diff carrier, diff case, and center housing, and even their rebuild kits are 90% compatable... however most everything else is different.

first, i located a transmission with only 48 k miles just 14 miles from my house. quite a coup... and keeping the stock R&P and with 1 through 4 this will remain a compromise... next, my first choice for 5th gear would have been something between about .750 and .800..... turns out the closest gear available without having something made is a .729 from the same euro A4 diesel (just a bit taller than ideal)... and for the high hp i'll be running, the ideal 6th gear would be about .620.... but, a .600 6th gear came from the same A4 diesel box..

that leaves a gap between 4th and 5th.... but since i'll be running a 470+ hp engine with huge torque, i'll only need to run the rpm up in 4th a bit higher than ideal before switching to 5th... but if i was attempting to blow someone's doors on the street, all i would need to do would be to run to the 6,100 rpm in 4th, to keep the engine north of 4000 rpm after switching to 5th.... and that torque available w/ the 388 c.i. LS motor solves the 'gear gap' problem in spades....

for any street driving and you're clearly better off with that gap happening after 4th gear, than having it after 5th when the car's horsepower demands are always going to be higher..... but the payoff is really there once you would experience the utility of having that tall 5th gear for cruising in traffic or running the secondary roads without premature wear on the bores, rings and bearings....

the problem of 1-4 still remains but in 5th and 6th, you're close to perfect...

running some numbers.... first, there's a considerable variance on speeds depending on what tires you use.... i'm gonna float some numbers using a tire that's fairly close to ideal no matter what engine you run—a 25.6" like you have with my Dunlop 275-35-18s. running the 35 aspect ratio not only offers a little more gear in 1st and 2nd, but of course, the ride is a lot less harsh.

stock 968 transmission;

1st; 3.182 :1
2nd; 2.000 :1
3rd; 1.435 :1
4th; 1.111 :1
5th; 0.912 :1
6th. 0.778 :1
final ratio 3.778

968 transmission with audi 2wd diesel 5th and 6th;

1st; 3.182 :1
2nd; 2.000 :1
3rd; 1.435 :1
4th; 1.111 :1
5th; 0.729 :1 (gap between 4th and 5th)
6th. 0.600 :1
final ratio 3.778

stock 968 gears w/ Turbo S R&P;
1st; 3.182 :1
2nd; 2.000 :1
3rd; 1.435 :1
4th; 1.111 :1
5th; 0.912 :1
6th. 0.778 :1
final ratio 3.446

bear in mind that whatever tire combination you run with a stock 968 transmission, your top speed in 4th gear will be about 82 % of your top speed in 5th gear.... top speed in 5th gear will be about 85 % of your top speed in 6th gear. my top speed running 25.6" tires in 4th gear is 113.8 mph @ 6,500 rpm... 5th gear (stock form) is 138.3.mph at 6,500 rpm, or 85.3 % of top speed in 6th gear.

my top speed running 25.6" tires and the stock transmission is 163 mph @ 6,500 rpm. in my case, my new V8 engine will be governed at 6,300 rpm so i wouldn't even be doing that good keeping the stock gears....


running the taller gears; some numbers....

starting with 5th gear, upgrading from the stock .912 to the available euro .729 01e gear, a V8 swap car will run like a rocket to 160 mph before switching to 6th gear at 6,000 rpm with a swapped V8 car and be able to make about 173 mph at 6,500 rpm if running a turbo 3.0.

running this large tire with a 0.600 6th gear would allow you to be able to reach 190 mph @ 5880 rpm and upwards of 195 mph @ 6035 rpm (stout LS2 or 3 with a cam).... and 200 mph @ 6189 rpm (could be possible w/ more head work and NO2).

now for running Turbo S, 3.446 diff.... ok, just multiply all the speeds listed above by 1.09349 (3.778/3.446)

top speed running 25.6" tires in 4th gear would increase speed to 124.4 mph @ 6,500 rpm (nice)... top speed in 5th gear increases to 151.2 mph at 6,500 rpm, and top speed in 6th gear goes up to 177.3 mph at 6,500 rpm.... however, the plot thickens because the Turbo S box came with taller 5th (.882) and 6th gears (.711) respectively... however, sourcing these gears will be next to impossible, (but they can be made up). so, life gets even better if you run Turbo S 5th and 6th with the Turbo S R&P;

Turbo S R&P w/ Turbo S 5th and 6th;

1st; 3.182 :1
2nd; 2.000 :1
3rd; 1.435 :1
4th; 1.111 :1
5th; 0.882 :1 (not easily sourced)
6th. 0.711 :1 (not easily sourced)
final ratio 3.446


if you wish to run these combinations for the smaller, more common 25.0" tire size... doing the math, my Dunlops make 818 revs per mile at 36 psi.... michelin Pilot Sport 2, 295-30-18s are 25.0" and make 832 revs per mile... Pirelli P-zero Corsa or Rosso 295-30-18 is also listed at 832 revs per mile... if you run the 25.0" Pilot Sport 2, or P-zero Rossa, just multiply all the speeds listed above by 0.9832 (832/818)

my transmission project, with the taller 5th and 6th is as follows:

transmission with 48 k miles; $1,800
purchase 5th and 6th gearsets; $1,730
labor to install/(4 hours)/misc parts/(local Getrag specialist); $620
total before adding the LSD is; $4,150.

used LSD; $750 (unfortunately,i still need to install it).


so in top gear i'll be able to see 70 mph at about 2,100 rpm....


from all ranges of driving, from putting around like an old lady on the secondary roads, to spirited, to flat-out, "see-ya-you-sorry-piece of ****" driving, the rpm numbers would look like this:


changing from 3rd gear to 4th at 2,583 rpm @ 35.0 mph will yield 2,000 rpm in 4th gear....

change from 4th gear at 2,800 rpm to 5th @ 49.0 mph will yield 1,838 rpm in 5th gear....

change from 4th/3,400 rpm to 5th @ 59.5 mph gives 2,232 rpm in 5th gear....

change from 4th/4,000 rpm to 5th @ 70.3 mph = 2,626 rpm in 5th gear....

change from 4th/4,500 rpm to 5th @ 78.8 mph = 2,954 rpm in 5th gear....

change from 4th/4,800 rpm to 5th @ 84.0 mph = 3,151 rpm in 5th gear....

flat out, changing from 4th/6,200 rpm to 5th @ 108.0 mph will yield 4,070 rpm in 5th gear with plenty of room to run to 160 mph at 6,000 rpm before changing to 6th gear.


as Tom (968LS1) mentions, the 1st through 4th gears are really bloody hell once more hp comes on board.... but, after taking a closer look, i think i won't find too much fault with running such a tall 5th gear, and it will still be a vast improvement over the stock 968 5th, especially, considering that i will be driving this car all over the country, and i don't wish to beat the crap out of the engine. it is a bit taller than i would prefer,

but, considering that the de-stroked LS7 can make about 400 + ft/lbs of torque in the low 3,000s,
switching from 4th to 5th still looks to be fine.



;

odurandina

you must have been reading my mind, as i've been to hell and back crunching the numbers for a long time and came to the same conclusion. talked to Tony G. on the phone a couple of times about this this as well, and the conclusion was unanimous — that the tall ratio 944 boxes are the only way to go.

running the bigger tires helps a little, but still not enough... i've determined that in real world driving, i'll be starting softly in 1st gear without dumping the clutch, and skipping second gear altogether.

that's the significant downside of staying with the 968 box.... but the biggest reason i chose to stay with it is that i reallllyy love the idea of being able to do ALL my long-haul driving between 5th and 6th and being able to keep the engine between 2,000 to 3,000 rpm all the way towards 100 mph....

if i ever make it out to my favorite lonely highway in south dakota again, i'm hoping to videotape a 190 mph pass from the roadside, and that threshold would be eclipsed at just under 5,900 rpm...

CarbonRevo

Taping from the roadside is just begging to be caught. Have to pass by, then come back and grab the camera. If I'm doing double the speed limit or more, I keep going in the direction I already was. Won't see me turning around lol

odurandina

that's one potential problem on this long 8 mile straight... but if you knew the location, there's almost zero law-enforcement in this area.


i'm surprised you all didn't mention the REAL problem:


will the engine EVEN be making enough power once i shift into top gear ?? look at the dyno numbers at 4,000 rpm for the LS2 vs the LS3.... it looks like i'll see very little if any net acceleration whatsoever once changing to top gear at 160 mph, as the engine will be turning 4,000 rpm at that moment... so the LS2 will likely not cut it... remember that i'm staying with the stock LS camshaft for bone smooth idle...

so, that means bumping up to LS3 territory or possibly even going to a larger bore w/ a Z06 block.


stock dyno: http://www.britishamericanengines.co...ngines/ls3.asp



first photo is the LS2 dyno second is the LS3....




.

944V8inDFW

**** getting new gears cut get build an engine that will rev higher stop bench racing and start working or at least saving your nickles for a engine that will rev beyond 7000 rpm and still make power

CarbonRevo

Have you ever riden in an LS2 powered vehicle? The torque is quite impressive.

Hell, my 4500lb+ blazer will do 138mph in 3rd gear at 6500 (stock redline). It then shifts to over drive (4th) and keeps on pulling to 145 (fastest I've done yet). It has absolutely no problem hitting that speed either. Even with 5 people in it.

Shoot DVC a message on here about his LS2 944. He puts down over 400 at the wheels. I'm sure he knows how that car feels in 5th gear. You would be surprised.