i still dont understand a people take so long to install these..  i had it up and running in under a day

Quote from: sleeperred90tgp on June 23, 2007, 08:23:54 AM

Quote from: TookyCat on June 20, 2007, 03:18:20 AM

And don't fall for the myth that a larger turbo will make more power at the same PSI.  That's never happened (on a stock motor) in my experience, the only power gains come from raising the boost beyond what your original turbo could do (11-12 PSI for the stock T25 on a stock motor).

TookyCat think about what you just said.  Turbos are rated at # per minute at x psi.
It's the # of air forced into a motor that make power stock or not. The turbo doesn't care if the motor is stock .

Gt25 at 1.5 bar (about 7 psi) will produce about 6 # minute. A gt3076 at the same psi will produce about 10# min. Thats how a bigger turbo makes more power.

Jud I respectfully disagree.  The motor is 191ci, and a volume of 191ci filled at 10 PSI is the same amount of air, regardless of which turbo has filled it.  Think about that for a second - when you fill a nitrous tank to 1200 PSI, does it matter which type of gas compressor was used to fill it?  Not really, it's either full or it isn't.

If you had a 191ci motor at 10 PSI filled by a small turbo, and the larger turbo fills it with "approximately twice as much air", then your gauge would read 20 PSI instead of 10 PSI.

The only REAL difference is the much-ballyhooed "efficiency" of the turbo, which in ALL of my experience usually results in a VERY small difference (virtually undetectable) when upgrading from a small turbo at a certain boost level, to a larger turbo at the SAME boost level.  The BIG power difference is when your small turbo is already at (or past) it's limit of efficiency (around 12 PSI on a stock TGP with stock T25).  But that's not really what I'm debating here - I'm talking about all these guys who think if you put a really large turbo on, you'll magically go much faster at the same pump-gas boost levels.  I've never seen it happen.

I seem to recall you going a lot faster with your turbo upgrades than the stock T25, and doing it at low boost levels.  But didn't you have an upgraded cam, and intake, and maybe heads?  That's a HUGE difference versus a stock TGP and makes the calculations totally different.  Running a T25 at 12 PSI on a stock TGP motor is at the efficiency limit.  Running a T25 at 12 PSI on a heads/cam/intake TGP motor is far, far beyond the efficiency limit, so I would expect a big gain when upgrading to a larger turbo, at that point. 

One thing I definitely know is that my GT2871R flows up to 45#/min which is about double the stock T25, and it was absolutely without a doubt, no faster at the same 8-12 PSI boost levels when doing a proper before-and-after comparison.  Both tuned to the same AFR and all variables eliminated.

PS: It required almost no tuning to the AFR, proving that the airflow didn't change at the same boost level.  If it had really been delivering "100%" more air, without changing the tune I would have noticed a HUGE lean spot at WOT.  How come I never witnessed such a lean condition?  No more air was being delivered.

Quote from: kuntzie on June 24, 2007, 05:11:07 PM
i still dont understand a people take so long to install these..  i had it up and running in under a day

Hey that's great (and perhaps unbelievable).  But maybe you do turbo conversions for a living and had all the necessary oddball fittings and adapters and pre-made lines of the correct length all in stock the morning you started your upgrade, I guess.

The rest of us aren't that lucky, and so you can continue to post your thinly veiled insults, and I'll continue to post my how-to information, and we can see which one proves more useful to the members of this board.

alright.... on the same topic..

10 psi is 10 psi on any turbo correct.. but its the CFM


i never increased the boost on my tgp when i upgraded to the gt2871r to see amaizing results. the motor was unchanged aswell.


put a geo metro turboon your car and see what 10 psi gives you.


jud i 100% agree with you



also unbelievable.. the turbo phisically bolts right on to the car it even had the 2" outlet to hook up to the stock intercooler piping. i drilled a hole in the downpipe and welded a bung on it.

a place dwn the street from me made a steel braided line in about 3 hours (yes i ordered it on the same day i started)

i ordered the oil drain when i got the turbo, with a barbed end fittin. i then went to canadian tire and got some Fuel grade line to run from the drain plug to the oil pan.

the  coolant fittings were also ordered with the turbo and mad it very simple.


this was also my very first turbo upgrade ive ever did, i only replaced the turbo with an oem one prior to that.

oh ya i also used  alen head bolts for the turbo and a 1/4 inch drvie rachet with a 3"extention to make it even easier

Hello to all!!  I just purchased from my sister the 1989 Turbo Grand Prix my dad bought her as a high school gaduation gift in 1989. (much better than the 1977 LTD Wagon I got :icon_rolleyes:)  However, my dad loved this car alot and it was regularly driven up until late 90's when she got a new car and this car sat around a lot. My dad passed away and that is how I was able to purchase it. I have read almost every post on these forums and they are a wealth of knowledge. Now that the history lesson is over, I must say that this car has most of the same problems as everyone elses. Definitley has the cracked crossover as well as the various common electrical concerns these cars appear to be prone to.  I will save the electrical problems for other categories. My reason for responding to this thread is that the turbo is blowing oil into the intercooler and subsequently the intake. I pulled of the turbo inlet pipe and you can wiggle the impeller and see it has been rubbing the housing.  I have read w-body.com forums as well as these forums and I must say I am impressed with the h/p/torque and 1/4 mile times on your car. It goes without saying that I need new turbo but in all these posts you seem to be the most specific in choice of turbo. I definitely would like to know the materials required to do the same install you did. I am planning to get a Kenny crossover and chip. Do you recommend this and if so what else might I need to get the power you are getting out of yours. I plan to pull the motor and tranny and seal up any leaks.  Any suggestions for this newbie would be greatly appreciated. I look forward to communicating with you all. :icon_biggrin: