Sold the 8-71 off my 355 sbc, The winter plans are to install a new turbo.. I have all the parts except the turbo..

355 sbc, typical block prep, 4-bolt, steel crank, scat rods, etc,etc, 8:1CR, Vic Jr Alum heads (O-ringed w/studs), Super victor int.. 750dp(mech secondary) th350, 3500 stall, 4:11 gear,
cam: 242/252 541int/561exh 112

I've done all the calculations.. plotted my engine air demands and preassure ratio's, the turbo that came above all others was the T-76.. I had to double check.. sure enough my plot went right through the sweet spot better than small compressors (t-72, t-66, etc) I see motors on the net making 1000+ with this turbo..Am I missing something?(My goal is 650-700. W/10lbs)

**On a side note I will be building a new small block next fall to handle 700+ and up to 15lbs, I'm going to buck this one until something pops.

Called Turbonetics and they were no help (choosing size)..everyone else I talk to seems to be a "Yes" man. I need someone else to tell me that this thing will pull....or to give some pointers

Is this thing going to be a slug until 5000rpm? I want the turbo to come on full (10lbs) at 3500-4000 and hold until 7000rpm shift.

More info:

The turbo will be passenger side mounted.. I will be using shorty headers connected with a "Y" than up to the turbo.. I have a Powerstroke intercooler, but I dont think I will use it to start, I'm going to try to plumb straight into the carb..(and keep my eye on inlet temps)the fuel system is done and good to 20psi.

Well.... tell me what you think

Gene

Care to share your calculations and maybe post the compressor maps to help us help you out?

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The Chevelle Page (http://www.geocities.com/diels12000)

Spend the $325. and have Scott at SD Concept Engineering do the carb fo you. On a blow through application there are several mods that need to be done. I've done several blow throughs with centrifugals and the carb is the key. Jetting alone isn't enough. Solid floats, milled housing, re-worked metering blocks, adjustable air bleeds, and sometimes different boosters are needed. The difference is night and day as far as power and driveability. His number is (401) 732-4047.

As far as turbo sizing, I would e-mail these two guys. They seem to have a lot of knowledge on turbo sizing.
http://www.montygwilliams.com/
http://www.grapeaperacing.com/GrapeApeRacing/

Jody

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MY CAMARO (http://www.camcojb.com)

compressor maps can be seen at www.turboneticsinc.com. (http://www.turboneticsinc.com.)

I tryed to use several boost levels and rpm ranges.. ( I used the equations shown on http://www.grapeaperacing.com/GrapeApeRacing)I settled on 12lbs avg with a pressure ratio of 1.81.. I used an inlet temp of 75F, 192F temp rise, 1.53 density ratio, this yeilds (depending on what I entered) an engine air demnd of 60-90lbs/min, The problem was I couldnt calculate what the preasure ratio would be at lower engine rpm.. my plot went horizontally through the maps (It should have gone diagonally.)

I guestimated the curve up to my calculated maximum demand. I found that smaller compressors would "fall off" at 7000.. the T-76 maintained 75% efficiency

***dont forget I plan to wastegate to maintain my desired boost for this motor.. I want the turbo to support my NEW motor next fall.

If you need anything else let me know

Gene

Gene, here's what I come up with for your airflow requirements. this is at 12lbs of boost.

RPM LBS of Air
3000 28.43
4000 37.91
5000 47.38
6000 56.86
7000 66.34

using a T-76 Compressor map your good pretty good until about 6000 RPM, then your effifiency drop off fast and your off the map. I think you need more turbo. Dave

My exact calculations were 64.54lbs/min at 7000 w/12lbs. http://www.chevelles.com/forum/smile.gif I was considering as big as a T-80, Doesnt that sound like over kill?
How can guys support so much power and airflow with this turbo(T-76)? Are they spinning the guts out of it and loosing efficency?

I've also been looking at the ceramic bearing option.. If you get this, do you still need to plumb an oil supply to the turbo?

Gene

No, a T-80 doesn't sound like overkill at all. Most all of the local 5.0 racers I deal with use T-88's or bigger. Garrett has a web page with listings on there Aftermarket stuff that shows what size turbo's make what HP, but I can't seem to find it. I got the link at work I"ll post it up Monday. Yes ball bearing turbos need a oil line just like a normal one

Gene, here's that link I was looking for, lots of good info!
www.turbobygarrett.com (http://www.turbobygarrett.com)

The catalog is 38 pages so if your on a modem it may take awhile to download

[This message has been edited by turbodave (edited 11-26-2002).]

Thanks for the link

I've been scoping out a T-88, looks like a healthy size turbo, and can keep up with my max RPM air demands

I'll keep you posted..

I have another question about exaust sizing.. Is there a rule for header primary size, and colector to turbo tube size? I want good exauhst velocity, but dont want to sacrifice flow..

Gene

Gene,not sure what to tell you on pipe size. Most setups I've seen they use whats easiest to fit the car. Maybe Dave Andrews will chime in here,or maybe look up his email. He is a engineer for Garrett and would be the expert to talk to about this. He is in the process of turbocharging his chevelle, although I haven't seen him post in a while.
I can check around with some of the local shops who build systems and see what they got to say. Dave

[This message has been edited by turbodave (edited 11-26-2002).]

Well, I made up my mind and went with a
PT-88 with a four bolt flange, It should be adequate for 7000rpm, I hope its not to big and Laggy at the track..

It'll be in my hands middle of next week, I'll keep you posted on progress, I hope to chassis dyno it just after christmas..

If anyone else knows any tips let me know..

Thanks again!!

Gene

Gene,

I'm very anxious to see the results! http://www.chevelles.com/forum/smile.gif

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71' 3880# with me. Big Block 402, Merlin oval heads, 10.2:1CR, TH400, 3.73 posi,
1/8th: 8.0 @ 88mph
1/4: 12.5 @109mph w/ 1.89 sixty foot (street tires)
Picture of me roasting the tires and other guy stuff (http://www.auburnextremeracing.com/drivers/mike/)
My other site, picture oriented (http://www.chevelle-ss.com/Member's_Pages/Mike_S.htm)

-Heart of Dixie Chevelle Club www.chevelle-ss.com (http://www.chevelle-ss.com)

You should really consider EFI. Alot better for the turbo. You lean that thing out 1 time, and it is history.

Hopefully if I'm nice to santa I might find a gift under the tree... http://www.chevelles.com/forum/smile.gif

I'm going to try the carb for this season (since its here). I have to send it away to get modified..

I've looked pretty close into blowthrough carb, I should be safe with my set up.. I wont be pushing mountains of boost through it at first.

I'm going to a boost sensitive regulator to keep fuel preasures safe.

Gene

Gene, here's a good website for blowthru carb setups
http://www.boards2go.com/boards/board.cgi?&user=huntracers

The blow-thru carb forum has been very helpful for me. I know nothing about turbos, there is a Yahoo turbo blow-thu group, do a search.

Slowly the mystery of blow-thru carb setup is being unveiled. And its about time - given the first popular availability in the 1950's (Studebaker/Packard/Thunderbird). There are guys running more than 20 psi through a carb. What I noticed most about my Carb Shop http://www.customcarbs.com prepped carb is what appears to be custom drilled billet boosters.

Thomas

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"Bomber" '67 El Camino, Beater comes back to life.
Was 350/TH350 14.90 @ 93mph, 360,000+ miles on car.
Now 406 roller, 340rwhp, more hp coming, 3.08 gears.
Street radials, left in drive, 13.20 e.t.@108.35 mph.
8/1/01 added Plum Mist '67 to collection
ProCharger D-2R 468 in the dyno! 1st pass = 716.6 tq @ 4300, 604.4 hp @ 4500, much tuning left!

Thanks

I've been a part of the blow through carb board for sometime, there are alot of very wise people on there when it comes to tuning, etc.

There is another blow through board on yahoo. http://groups.yahoo.com/group/BLOWTHRU/
some good guys there as well!!

Gene