I bought a GT2871R turbo for my TGP on 11/2005, sat on it for several months, and installed it during 06/2006 and have been running it ever since.  In my opinion this series of turbo is the ultimate TGP bolt on turbo.  I went with the 743347-2 model which features a larger 53mm 56 trim compressor inducer capable of supporting 475HP, compared to the standard GT2871R 743347-1 model which has a 49mm 48 trim compressor inducer, flowing a maximum capacity for 400HP.  I also went with the .86 exhaust A/R.  It turns out that this turbo is pretty laggy and I should have gone with the 743347-1 400HP model for better spoolup (and I seriously doubt any 4T60 or HM282 could withstand the torque produced beyond the 400HP point anyway).  I get 4-5 PSI boost at part throttle so it's still very decent but nothing like the Roots-blower-style spool of the stock T25 with a manual boost valve.  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).

Anyways, the install was a monster project, requiring at least 100 hours of combined labor and running around to get all the little bits & pieces to make this a 100% complete install with zero sacrifices/cheats.  I took a ton of photos and intended to write a big install guide but never got around to it.

Is anyone interested in this?  Speak up and I'll write a nice web page if there's enough interest to make it worth my time (several hours I'm sure).

Here's the finished product:

MEMEME

Interested...

Quote from: GutlessSupreme on June 20, 2007, 11:53:11 AM
MEMEME

Me Too

Quote from: TookyCat on June 20, 2007, 03:18:20 AM
Here's the finished product:

OOH me likey!!! :icon_twisted:

I'm down.

So, your power is peaking at only 4,000 rpms Josh? Have you verified this on a dyno or are you going by the datamaster program that you use(I seem to remember you posting a pretty accurate "dyno" from that datamaster program before anyways)?  Every TGP dyno I've seen seems to have power peaking just under/around 5K or so. What injectors are you running now?

Glad to hear there is some interest already in this guide.  I'll start looking for some time to publish a comprehensive photo guide.

Quote from: mfewtrail on June 20, 2007, 10:13:03 PM
So, your power is peaking at only 4,000 rpms Josh? Have you verified this on a dyno or are you going by the datamaster program that you use(I seem to remember you posting a pretty accurate "dyno" from that datamaster program before anyways)?  Every TGP dyno I've seen seems to have power peaking just under/around 5K or so. What injectors are you running now?

Yes and now I'm becoming more convinced it's a very serious loss of horsepower that I'm experiencing from 4000-5100.  After replacing the valve springs and no change; is it possible my 200,000 mile camshaft has worn lobes?  I mean it is a flat tappet..  I should have checked the lift at the valve when I had it open for the valve springs. 

I only have Datamaster Dyno to show for:



...but you can feel it exactly as the DM Dyno chart appears.  I'll try to illustrate: when you hit the gas, there's some lag, and then the boost starts to come on real fast and the torque really puts you back in the seat, and then it reaches 4000 where the boost first peaks at 14 PSI, and for the remainder of the gear (4000 to 5400), it practically feels half as fast as it did from 3000 to 4000.  Considering that I go down the quarter mile almost entirely from 4000 to 5400 and back again, this seems to really be responsible for my car having less power than I expected at WOT.

Judging from the "normal" TGP dyno charts, I would expect the car to remain "fast" from 3000 to 5000 (at least), instead of just 3000 to 4000.  I'm still trying to finish a Walbro fuel pump upgrade, maybe that will help a little but I doubt it is my core issue.  I'm all ears if anyone has any suggestions.  I keep the ignition parts maintained, and it's running about 11.8 AFR at WOT and the boost is very flat at 14 PSI.  The motor sounds great but just gets weak after 4000.  The injectors are some used 150,000 mile 28#(30#) Syclone injectors from a friend of mine.  However it has always shown this exact same dyno curve, even when I had the stock turbo with stock injectors (it was just a less powerful dyno obviously).

I'd definetly be interested in a write up too.  It's a plan of mine in the future!!

man i don't know about these TGPs just dieing like a mad beast after 4k....i recall kuntzie had a similiar turbo with very similar curve....we'll have to see if his new big snail solved the top-end shit out!  i know these cars aren't top end cars but you'd think the right turbo/wastegate and dp would at least hold the ponies up to 5k or 6k!!

kuntzie quite F'n around and unveil already!!

im getting antsy!

Nice  :icon_twisted:

You'll keep falling flat after 4K or so because of the Cam profile and the intake manifold desighn. It's all ment for low-mid rpm torque. You'll need a larger profile cam. You can go to a 3100, 3400 top end swap or go nuts and use a 3500 manifold with the 3400 heads. THe later top end better supports top end power. Or you can just blow on it harder  :icon_exclaim:  :icon_mrgreen:

Quote from: futuretgp'er on June 21, 2007, 09:29:55 PM
man i don't know about these TGPs just dieing like a mad beast after 4k....i recall kuntzie had a similiar turbo with very similar curve....

im getting antsy!

He had tuning issues and was running out of fuel there from what I remember. I don't see why Josh's chart should be any different from a stock turbo TGP(they still make good power to 5K, just take a look at YOUR own dyno chart future'...I forget your real name? :icon_redface:).


^hope you don't mind me posting your chart there... ;)

EDIT: Everyone thinks these cars die after 4K because you've just passed the torque peak there where it feels so strong. People make similar comments about L67 powered cars. ;) In Josh's case above, his power is dropping off hard up top.

On a sorta related note, my NA 3.1 seems to be doing exactly as your car is Josh. It nosedives past 4K and just gets noisy as hell now. I do believe my problem is valve spring related(~230K miles or so on my engine). I noticed this problem a lot more after swapping in some 1.6 ratio rocker arms. :icon_redface:

yeah your right i should have specified the tourque....not exactly the hp.  my bad!  :icon_redface:

ps would still like to see a dyno curve with both trq and hp jumping up and staying up till redline

Quote from: TookyCat link=topic=4165.msg28462#msg28462
is it possible my 200,000 mile camshaft has worn lobes?

definetly a big possibility.. several members have had a lobes 9 or 10 wipe out completely, myself included.

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.

Good looking install.  :icon_cool:You should do a write up, and yea it will take some time. Maybe Kenny would make it a sticky. About a third of the PM's I get are questions about turbo installs.

Jud