allergic2milk

So if turboing the n/a motor is not worth it, what about swapping a turbo engine/ tranny into a n/a? would it still be cheaper to sell the n/a and buy a turbo?
If not, what is required?
Don't get me wrong, i love my car, its just that i feel as tho in the power area i am limited.
Suggestions? Sarcastic comments? help with spelling and general grammers?

Manning

Every now and then George B answers this question in the tech section of Panorama. Never a positive response.

This will likely evolve into a pissing match.

Just to start, NO you do not need the suspension bits from a 951 and NO the transmission was not beefed up on the 951. Not until 88 at least, only on the 951S for that year, and only the 1st and 2nd gears were shot peened to help strengthen them.

Yabo

Manning, ar eyou sure the ring and pinion was not beefed up compared to NA? I am pretty sure the S2 had a beefier R&P as well.

Manning

R&P were beefed up on the S2, not the 951. Got that straight from FSM and the regional Porsche tech rep.

Mighty Shilling

Interesting...then why does the 944 R&P blow all the time, yet the 951, we rarely hear about? could it be the initial torque of the NA, and the turbo lacks torque until it spools?

Manning

Beats the hell out of me. All I know is what I read in the manual and what was discussed in the tech session at Fred Baker's. Your guess may be right though, plus boy racer types figure you gotta launch an NA hard to get the jump. I imagine if you really looked into it though you would find more blown R&Ps than you think on 951s.

FRporscheman

I've heard the 951 trannies are more robust. Any comment I've read on how 951 trannies last longer has stemmed from a comment on their improved integrity. I could be wrong but that's what I remember reading.

I'm no turbo expert, but I think you would also need the DME and KLR. If your NA is of the early kind, you will need to cut your header panel off (the panel with the porsche crest) so you can put the intercooler underneath. If your NA is the late kind, this panel just comes off. You will need the 951 exhaust, since NA flanges are 3-bolt and turbo flanges are 4-bolt. OR you could have a muffler shop just weld your NA pipes to your turbo headers (bad idea).

xsboost90

of course the 951 trannies have oil coolers on them- im sure that helps some. It can be done, swap engines, dme harness', tranny, put some brakes on there to make it stop...im sure you could buy a turbo for the cost but it can be done.

PeteL

If you get the engine and computers, wouldn't it be a straight bolt-in for a late car?
Will everything fit in the N/A front end?

xsboost90

well... bolt in yes...straight- thats debatable. The intercooler will fit under the n/a nose, there are alot of small details you would still need like the brake mc heat shield etc...

VWaddict

My '89 951 had an S2 R&P retrofitted into it. The mechanic affirms that the S2 had the best R&P, though I seem to recall nim saying that the 88 'S' and all 89's (since all 89s were built to 'S' spec) also had strengthened 1 & 2 gears... I suppose that gives me the best of both worlds?

Keith

Manning

Yep, read my posts above. The 88 S and all 89 on 951s had shot peened 1st and 2nd. The S2 had a strengthened R&P.

Tom M'Guinn

At today's 951 prices, it's cheaper to just buy a 951.

Manning

I think that is the general concensus. On the other hand, as a project for the sake of doing it I don't think it is unreasonable. And if you can get EVERYTHING needed for a song, then why not. I also think it would be a hoot to stuff a 951 engine and such under the hood of a 924S.

But yeah, cheaper just to get a 951 to begin with.

Oddjob

I dont want to stray too far off topic (swapping in a turbo engine into an n/a), but I do want to clear up some info on the transmissions:

The S, Turbo, and S2 transmissions are stronger than an n/a. If you check, few of the major internal part numbers are the same as an n/a. The case is machined differently to fit the larger ring and pinions.

The factory manuals are very vague about mechanical properties and specific differences between the transmissions. They are mainly concerned with assembly and disassembly for maintenance and servicing, not engineering design specs for manufacturing. So dont rely on the FSM to explain which parts and transmissions are stronger than others.

I have no idea why any knowledgeable/experienced Porsche Technician would make a claim that a Turbo trans is not stronger than an n/a trans - that is completely false. And there are plenty of Certified Porsche mechanics that will say otherwise.

From a mech engineering standpoint, when it comes to strength, size matters; the larger/thicker the gear tooth is, the stronger it is.

The Turbo R/P is by far the strongest of the ring and pinion sets. It has the fewest/largest teeth of the bunch - 8 big teeth on the pinion head to match with 27 teeth on the ring gear.

The S2 has 31 teeth on the ring gear, so they are slightly smaller teeth (same outer circumference, divided by 31 versus 27 = a smaller size tooth). The head of the pinion gear is smaller, so the 8 teeth (which have to mate with the teeth on the ring gear) are also smaller than the turbo's pinion teeth.

The S has 9 teeth on the pinion and 35 on the ring gear. These teeth are smaller than the S2 r/p teeth, and therefore weaker yet. Although there are some that have and are successfully (?) running S r/p sets in 944Ts, the general consensus is that the S r/p can fail in a higher hp/torque use.

I have disassembled a 944S transmission, an 87T trans, an 89TS trans, and an S2 trans. Ive had a turbo R/P sitting side by side with the S2 R/P, and there is little doubt that the Turbo R/P is definitely beefier.

Now, it is well proven that the S2 R/P set is strong enough for even high torque/power applications, but in the end, it is not as strong as the Turbo (which just shows that the Turbo R/P has a very high factor of safety). The S2 may be a "preferred" R/P for use in a turbo, since the shorter final drive ratio will improve acceleration, but its arguable that its the "best".

The only uncertainty that I have, is comparing an S r/p to an n/a. I have not looked at them side by side. They are both 3.889:1 and have 9 pinion teeth and 35 ring gear teeth. But, since the S trans case has the different machining to fit a larger ring gear, and the r/p part numbers are different, I believe that the S r/p set is somewhat larger and stronger than an n/a. And S cars are not prone to breaking R/Ps, but n/a cars do.

There is not much difference between a standard turbo and a TS transmission (other than the LSD and Cooler options/standard). The input shaft has an additional hardening process performed on the 1st and 2nd gear teeth. This updated input shaft superceeds the previous shaft and is used on the 88TS, 89Ts, and S2s. Not sure how critical this update was, as there is little evidence that the earlier Turbo transmissions were prone to breaking the 1st or 2nd gear teeth off the input shaft.

The later LSDs (used on the AOR & AOT tramsissions) had thicker inner friction discs and so the pressure rings are machined differently to fit the thicker disc. These parts superceed the older parts and can be retrofitted into the earlier LSD units. For a street car, this is probably irrelevant. It was likely an upgrade developed during the Turbo Cup racing series, where the race cars were burning up the LSD friction discs faster than was expected.