So... working on my own car today- the '98 S70 GLT. (13G turbo) It's been losing power a bit- mostly the lag has increased a bunch- and consuming a good bit of oil. the car has just over 150k on it, so I've been suspecting that the turbo is on its way out. So today, I took the air intake hose off and checked the turbo. Full of oil, as I suspected, somewhat excessive up- and- down play, but not horrible... and HOLYCRAP! wow, that's a lot of end play! I attached my dial indicator, and the end play is about .070"! So... the turbo is done for. Here's my question: I have a 15G (or 15T, can't remember which, but it's the stock turbo from the donor car) out of a '98 S70 T5 that is in excellent condition. I know it will bolt up, but do I need to worry about anything else if I don't make any other changes? I will probably add a boost gauge when I do it, and I'm also getting ready to do the timing belt and all associated parts. At that time, I might put in an intake cam from an NA engine- I don't want both cams, as I understand it'll cause too much overlap. The only other mod I'm ever likely to do to this car is swap in a T5 ECU. I don't want a race car, and I don't have tons of cash to spend. Is the cam a good idea?- I'm looking mainly to improve off- the- line performance with that change, which is the one thing that annoys me about this car, and I know the slightly bigger turbo will only make that worse.

And I know some people ask... so yes, aside from the timing belt, which I'll be doing in the next week along with water pump, tensioner and idler, this car is totally current on maintenance, with recent plug wires, plugs, filters, oil, etc. So no need for a "stage 0."

Basically, while I'm a good mechanic, I'm not that knowledgeable on performance upgrades... so I need a bit of help from those who are! Any suggestions on this? mainly:

1. Any risks in switching to the bigger turbo, without changing anything else

2. will putting in an NA intake cam (or both cams) improve low- end power? and how should I adjust the cams for this?

 

Hey man, don't have the answers to your questions but I will say this... Our S70 GLT is hell off the line. I recently got a ticket from spinning the tires so bad that the cop had to wait for the smoke to clear to come get me. ) I think you would be happy if your turbo wasn't going out. Also, select the S button and I think you will be fine.

Heck, go test drive a few GLT's as if you are thinking about buying them and test them yourself.

 

See, I've driven a few other GLTs, and I've noticed that those were all better than mine off the line, too. Since most of them have been 99 and 00 models, I attributed it to different throttle response from the ETM, but I've also driven other '98s, and those have been better off the line, too. And mine's been like that since I bought it at 98k miles. The turbo was fine then, of course. My best thought on this is that when the original timing belt was changed, maybe they didn't set the cams correctly after loosening the bolts. I plan on using the factory tools to set them when I change the belt so that I can rule that out. This car has always been a hoot to drive and it pulls great under load, especially when passing, but it's always sucked from a dead stop, even before the turbo started to go. And I have "S" activated most of the time, anyway- it really doesn't do anything from a stop, though... all it does is hold out shifts.

Anyhow, the car goes under the knife next week. Timing belt and everything it touches, turbo, and depending on what people tell me on here, maybe the NA intake cam. I also might put the intake manifold and throttle body from that NA engine I have the cam from, not that I think it would do much, but just because I can The NA motor I have lying around is one that had its timing belt break, so it's basically parts and scrap now, anyways, and I got it for next to nothing.

Any thoughts, anyone?

 

Know you're a good tech; seen your advice here and it is always top-notch!!

Re: #2; though i can't say from personal experience, I would think the NA cams would move the pwr curve up in rpm rather than down given their higher lift and overlap.

Would think the bigger turbo would also do the same but would certainly increase pwr once it's spooled up, but again, more lag off the line.

That's why a lot of newer perf cars are using twin turbos; a smaller one that will spool up quickly (for low-end response) and bigger one (that takes longer to spool up but has more cfm flow) for increased pwr across entire rpm band.

I have both a 850 NA and '98 S70 GLT; the 850 definitely is freer revving than the GLT, but if you stomp on the GLT off the line you better have room in front of you because it's a going .... now!

Have you ckd the compression?

I know gilber, ibified, and I think tech have all gone to NA cams on their T5's but I am sure they've done lots of other mods too so comparison may be apples and oranges. Anyway, i would ping them for their experience.