Tiago

iTrader: (27)

Figured I would ask here for some other experienced folks to chime in

Project is a 3.8L V6 Fbody. Fresh forged motor.

intake and heads are ported, cam is 218/218 528/528 114, manley single coil 150# springs, not sure on the installed height, need to find out from LME, but not too worried about this since the graph doesn't show any valve float..Only revving to about 6300 rpms, graph already crested over at this point and not rising any more.

turbo is S74 0.81 A/R T4 turbine 3.5" downpipe.
Have 2.5" pipes from each header going into turbo, 1.5" primaries on the headers. intercooler is OBX intercooler 30x12x4. 3" pipe to the throttle body.

AFR was in the 11's on all runs.


during the dyno session, this is what we observed (I am rounding numbers as I don't have the graphs in front of me):


10 PSI = 290 rw - this is shitty, a stock motor on 10 psi from a MPT70 will make ~ 350 rw.

20 PSI = 580 rw ( made this much on 2 lbs less on old motor )

23 PSI = 620 rw

26 PSI = 650 rw.
at 26 PSI I was expecting the power to really be closer to 750 rw.

as the trend shows, the higher we turn it up the less power it makes per pound of boost, almost like the turbo is running out of steam, but the turbo should be good for 1100 fwhp. Boost holds steady. So the question is, what else could cause this phenomenom?

we checked the plugs and they look ok, running out of ideas.

sevanseriesta

iTrader: (34)

I hate to say this but I am not sure how much response you are going to get, you kind of intimidate us little guys. How would we be able to diagnose for you.....LOL

Does it have good compression. I know My Mr2 did not make much power when the compression was low!

OUTLAWZ RACING

iTrader: (9)

What was the compression and how new is the motor? I was going to say the intercooler because I had a obx and it suck big time. Also what was the intake temps on each run? The HP per Psi seems down.

Tiago

iTrader: (27)

LOL, there are far more experienced people here then I

I have not checked compression, but motor has maybe 100 break in miles on it. Intake temps were only 108 def F in the 26 psi pull.

OUTLAWZ RACING

iTrader: (9)

Dam 100 miles LOL! My vote is to put some miles on that thing. Hell its not even brocken in. I Oh not to bring bad juju but you can hurt the turbo by not letting that thing break in. All the little **** that needs to be worn in like ring can leave shavings in the oil and the turbo can pick that stuff up. But I duuno To the top for Tiago!

10sec_rx7

looks to be out of turbo... going by the turbo name im guessing it is a 74mm comp wheel??

try putting a larger rear end on it.. .81 is tiny, try something in the 1.00 range.

have you measured the manifold back pressure?

Tiago

iTrader: (27)

have not measured back pressure but it is my only lead at this time

yes 74mm ETT compressor wheel. Should not be out of turbo but Hopefully Dr. Turbo will chime in.

DrTurbo

iTrader: (3)

Is the boost dropping?? That is the first key.....if not then you still have plenty of turbo. Also yes....backpressure #'s are a must!! Might need to swap to the larger A/R's BW has.

DrTurbo

iTrader: (3)

Ok re-read the post......its not the compressor side since boost is holding steady. Also what makes zero sense is the intake temps are cool, so that means the turbo is barely working on the compressor side as well. When a turbo is done the outlet temps reach 350-400 degF. So that means we either have a restriction on the intake side or the exhaust side. If the turbo was done you will see boost peak then fall toward the end of the RPM range. Talk to Jose...he will know.

10sec_rx7

thats exactly what it will need..

a .81 T04 housing is what we run on 2L motors over here... on a 3.8L i wouldnt be starting any less than 1.0 and would more than likely be using a 1.32..

Roadie

Sorry to be off topic, but what kind of gas mileage does that thing get?

qqwqeqwrqwqtq

Where does it make peak torque and what are you using for engine management?

one fast zo6

iTrader: (490)

what spark plugs and what gap?

daniel6718

iTrader: (36)

tranny? is it an auto which the converter might be crapping? or clutch going?

Inspector12

iTrader: (29)

It has a T56 in it last I remember the stock 5 spd didnt hold up. Tiago what did you change on the motor besides the Pistons and Rods? Is that the cam from the original motor? Heads etc... I would be looking at what has changed since the new motor install. Is the new motor Lower compression? Give us a quick rundown please. Have you tried the old turbo to see what it did? Just a few questions to spark your own thoughts on it etc... GL!
Jeff

hellbents10

iTrader: (10)

To properly diagnose this you need a back pressure readings at the turbine inlet and after the turbine housing on the down pipe. I bet that that .81 with the 83mm turbine wheel is not going to cut it. Even with a 1.25 and a 83mm turbine wheel we are at 2+:1 PR's on 700 or so whp v-8's.

engineermike

Check this out. 780 rwhp at 34 psi from a pretty radical 3.8 setup isn't too far off from yours:

http://turbohightechperformance.auto...o-t/index.html

Or this. . . Only 440 rwhp at 21 psi with ported heads and a 218 cam:

http://www.turbobuick.com/forums/gen...rs-inside.html

When compared to the other 3.8's, you're doing pretty dang good.

Also, note that lower compression will always make less power than high compression, even on boosted motors. This may explain why your power is down at 10 psi boost from a stock Series II 3.8.

Mike

Linxs

iTrader: (4)

I think it peaks around 5000 RPMS. I'll get the graphs if Tiago did not get them yesterday....


The motor has over 200 miles on it and the turbo have about 1500 miles on it.
9-10 mph

TR8's gapped at .030

It's a built T56 Clutch is a Stage 5+ from Spec. Again only 1500 miles on it....

Changed from old motor to new motor:

Interal coatings, bearings, crank, pistons, con rods, heads received air path coating along with a coating in the comb. chamber. Intake also received an internal coating as well.
Upgraded the stock fuel system to a -8 setup had special fuel rails made and upgraded to 120LB injectors.

I'll check on the comp. but it should be 8:1

Old turbo is sold.

The car made 614 RWHP on 19.3 PSI with the old motor. Made on 109 race fuel. We were running Q16 on the runs above...

The exhaust is dumped infront of the Passenger seat (3.5" pipe). Do you think it may be back preasure still?

engineermike

So, the new motor makes 580 rwhp at 20 psi. IF...the new motor is 8/1 and the old one was 10/1, then the old one should have made about 10% more power (~5% power per point of compression) every step of the way. 580 x 1.10 = 640 rwhp. So, you gained 25 hp from coatings and a turbo upgrade if my compression ratio assumptions were correct.

Tiago

iTrader: (27)

We are going to try a 1.1 A/R

10 mpg?

stock PCM, HPT. On the street about 4000 RPM peak tq, on the dyno at about 4800rpm.

TR8s, 0.030 gap.

Yes has a T56. Nothing changed internally on the motor at all, they just cleaned up the parts and put new bearings/rings on it, fancy coatings, and properly clearanced the bearings The previous motor had the same parts and probably a slightly lower CR, aas we milled the heads during the refresh. We don't have the old turbo anymore, but we have checked out the new turbo, everything looks ok.


thanks for the links, but Im just going by the numbers, it doesn't add up on the new 3.8s. The last motor was already 8.0:1 it wasn't the original motor.


also I should mention that we changed fuels, we started the runs with Q16, and it was only making ~520 at 20 psi, when we put VP109 in, we instantly, picked up 60 rwhp. But a few runs later it started picking up knock, with no changes on the tune or boost, so we called it a day to inspect everything and do some troubleshooting.