pillage6

I am looking to increase the boost pressure on my turbo and was wondering what the max is?

Also, is there a level of boost that has maximum efficiency?

Thanks for any responses, I am new to turbocharging, as if that isn't blatantly obvious.

pillage6

I am running 8 lbs. and I know I can push a lot more than that.

I saw a compressor map, but it was in some foreign math calculation that I have no idea how to figure out.

1FastT2

iTrader: (1)

23psi would be in the most efficient band of power for the turbo. You can run up to 40psi with that turbo before you have to worry about over spinning it.

Might I add that the 23psi would be running around 78% efficiency and the 40psi would drop the efficiency down to 70%.

There are alot of factors that need to be taken into the equation.

pillage6

What factors are those if I may ask?

What timing should I run?

I have a distributor, but no way of retarging the timing under boost.

I don't know if I want to push 23lbs., that seems kind of high.

the_glass_man

iTrader: (2)

Post the compressor map, it would help.

pillage6

I tried attaching the map, but it wouldn't work, tried many many times.

Here is the link: http://www.turboneticsinc.com/comp_maps/t76.html

eViLRotor

iTrader: (2)

Here is the basic rundown of how to read a map:

-The y-axis (vertical) is your boost in bar. To convert psi to bar psi+14.7/14.7 = bar.

-The x-axis (horizontal) is flow rate. 10 lbs/min = approx 100 bhp.

The center of the middle efficiency 'island' is your sweet spot for the turbo. With the T-76 that's approx 2.00 bar @ 50 lb/min.

But as you notice, each island is a range, so you could make more or less, depending on a lot of factors...

..you can make more power with more boost, but as you see on the graph that will reduce efficency (bigger islands) and increase turbine speed (the rpm lines)...

...hope that helps.

1FastT2

iTrader: (1)

Accually the 8psi you are running does fall within the highest effiency range provided you are making 350hp.

fdracer

as long as you keep backpressure in check there really is no max amount of boost for that large a turbo. your motor will die before that turbo will ever see it's limits. the sport compact drag cars are boosting 50-60 lbs. consistently.

turbostreetfighter

also a 76 is way too big for any street car!!! if you are only running 8 psi you may be better off with a 62-1 turbo for street driving. for that turbo to work right you need to be within a boost range that requires race gas.IMHO


MWW

Bridgeported

I agree, I would not use a T76 on a street 13B unless running at least 20 psi.

pillage6

Well, let me try 14 lbs. first, then if I don't hear anything or smell anything funny, then I will up the boost.

I am rich on the top end and timing is retarded pretty well, so cross your fingers and thanks for all the help guys!

I will start looking for a smaller turbo, any suggestions?

fdracer

a 66mm should work pretty good

setzep

depends on what king of HP and torque spread you want.

pillage6

Not looking to be the fastest, just quick.

I don't want to make more horsepower than what I can apply.

I don't like shopping for tires every couple of months.

pillage6

I think my car is pretty fast right now, and I plan on putting in a lightweight flywheel this week.

I turned up the boost and the car is not missing or anything on boost, so I think I am safe, for now.

Turbo 3

iTrader: (3)

Too big for a street car? ... Not too big for a 20B my friend

However I'd agree that it is much too big for a 13B unless he's running a 0.8 or 0.9A/R or thereabouts on the turbine so it actually spools up right away. You'll make a lot of boost all through the rev range without getting much out of the "sweet spot" for efficiency.

Pillage - What is the A/R you have right now on the turbine? Also, you sound like you don't have an EGT? You should get one so you know what is going on with your temps BEFORE you blow your motor. Right now it sounds like you are just turning up the boost with no idea what A/F you are running or EGT's and hoping for the best...

rotaryengineering

I disagree the T-76 is fine you just need to tune it for your applicatoin. Tuning and Jetting is the key with the Cartech Systems. Turbo 3 is right on the money you need to buy a "Computech" EGT Meter it will be money well spent. Much cheaper than building another motor.

Albert

pillage6

My air/ fuel was 13 at low rpm's and 11 at high.

I will be rejetting to get 11's all the way through. I have an A/F gauge, but the numbers I gave you were from the dyno.

I will be getting an EGT soon.

I believe the A/R is .96? Does that sound right?

Gearhead

iTrader: (1)

Just out of curiosity, what are your engine details?

pillage6

87 TII block, stock intake ports, I think my exhaust ports are ported, but I haven't taken off the exhaust manifold to look.

What else do you need to know?

Turbo 3

iTrader: (3)

0.96 A/R sounds right. We don't know what your application is so it may be too big, may be too small. For the boost you are running, sounds like it is fine but the turbo itself might be too large for your app. I'd still suggest, if you're looking for quick street response that is, to keep working through your fuel/ignition stages, buy the EGT, and keep turning up the boost until you don't feel safe driving the car anymore. Don't change any of the hardware until you know you're goals aren't being met.

At this stage we don't know enough info to help steer you in the right direction but continue with what you're doing...should be ok, just go slow and watch your data.

rotaryengineering

Neil, What size Carb and Jetting do you run on your Cartech setup?

I help a guy on the East Coast with a setup similar to the system you run. He runs a Weber 40 IDF Carb with a Turbonetics T-72. The system has seen 20-22psi boost and it runs 11.30's @ 124mph. I am building him a custom Turbo that I ran on my car for years and it works great. The new Turbo will be done this week I'll let you know how it runs. The turbo is built using the same T-76 Wheel you are running in your car now.

Albert

pillage6

40 IDF with:
165 mains
f3 emulsions
130 air
55 idle
28mm venturis

I am at 12psi right now, but that might change after I go to the dyno next week.

pillage6

I don't think I will be turning the boost up too much more since traction is becoming a problem and this is my daily driver.