How big of a TURBO?

[ttypelova]

I can't decide on which size turbo I should go with. I have a sg1 block with fully ported heads and bigger vavles, 10 3500 converter, 206/206 roller cam. I was thinking of a pt-70, does anyone think that this is to big. I only want to run 17 lbs. on the street and 24 at the track, but mainly the car will be driven on the street. I was reading somewhere that the pt-70 doesn't come alive until 26-30 lbs. of boost but I really don't want to run that much boost. And also, does anyone think that there would a lot of turbo lag, how much. Thanks fellas!!!

 

[Two Lane]

Our Virginia bud Red can give you first-hand experience/opinion
on your question!

 

[REDS HOT AIR]

not me I dont know what low boost is..

actually I'm running 17# on mine right now because i have a 25 degree timing chip in it and 93 octane fuel

mine is an LT 70-1 which is a John Craig version

3500 stall is perfect for the 70 turbo ...when I was running a 2800 converter with it it spiked the boost right at 3400 so with your converter you should be right on the money.

I'm going to the track again this sunday and i'm consitering making a pass at 17# just to see what it does...It feels ok but nothing like it feels up in the mid 20's on boost

car is capable of running mid to low 10's at around 130 mph at 25# boost range...I've been having a problem getting enough fuel to it at them levels but with a crappy 1.81 60 ft I managed a 10.97 at 126 and was backing out of it from 1000 ft mark on due to it leaning out.

I've now added a second fuel pump and hopeing that will help for now cause all my local tracks close after this weekend.

see sig for motor details..

My LT 70-1 is p trim exaust with a garrett 63a/r housing and the big turbonetics intake side with 4" inlet and 2 1/2 outlet.

with this turbo and a street chip at 20 degrees timing with the front mount i/c i have been up to 24# boost on 93 octane fuel but 17-18# is all I can seem to get with the 25 degree chip thats in it now.

 

[blackbuick87]

If you dont want to run big boost why bother with a big turbo? Get a 63 or a 45 instead and it will be a little more streetable

 

[PsychoBuickBoy]

I have the exact same turbo that Reds has and it is great! I have not stepped up my injectors yet so obviuosly I have not ran it over 20 psi. I run it right at 20 psi with 22 degrees timing on 101 octane unleaded fuel. It runs like mad! Can't wait to step into some appropriate injectors and see what this thing does at 25 psi! 3500 stall with this turbo will have you going sideways through an intersection from a stop, my tires break at anything under 40mph!

John Craig turbos are cool!

I have not used the alky system in a while because I had problems bogging the turbo from spooling whenever the alky would kick in.

 

[blackbuick87]

Try a smaller jet or a higher turn on point. At 14-15psi there should be no bog

 

[Trbobuick]

Black buick- define "streetable" ?

It really depends on the combo

There are 4 street t-76's here and they are all on the street. I plan on running my BB76 on low boost ( 15 -18 psi) sometimes. And it will be streetable.
I also have 272 cubes so i have more cubes to pump the turbine wheel

 

[blackbuick87]

Well he didnt list his combo or speed goals, so everyones definition of streetable is different.

But it is foolish to get a big turbo to run 24psi, when a smaller one that spools faster will do the same job

 

[ijames]

But it is foolish to get a big turbo to run 24psi, when a smaller one that spools faster will do the same job

Not really; it's the old efficiency game. A big turbo will most likely be more efficient at a given boost and so will give a cooler charge and thus will flow more air at the same boost. Further, the turbine side will be less restrictive so again, more airflow at the same boost. The price, as you say, is lag, but if you have the converter to spool it, there's no question that a bigger turbo will make more power at the same boost and thus be faster.

 

[BUICKTR]

With that block I would have a T-70 or T-72. You may also look into the ball bearing turbos if you want a faster spool up.

 

[PsychoBuickBoy]

quote:
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But it is foolish to get a big turbo to run 24psi, when a smaller one that spools faster will do the same job
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I know this LT70 sends my car down the street ALOT quicker then the TE62 I had before or the stocker at 20 PSI. I think it is an efficiency thing.

 

[John Wilde]

Get the 70

I have run the PTE stealth 70 and the 70-1 on the street.
as long as you are set up fuel, timing and conveter wise I think this would be a great choice.

 

[TType85]

i'm running a LT-70 with .85 housing on the street with a 9" is too tight. I'm going to the .63 housing so it should be all good.

The car with bone stock heads went 115mph in the 1/4 on 15psi. I have some GN1's going on it so I should be able to run some good numbers soon.