My buddy and i are trying to figure out what size turbo would equal my D-1sc. He is a turbo fanatic and i like superchargers, He thinks that a D-1sc would be out performed by a t-76mm turbo in the same application and i told him i think it would be close but he thinks it wouldnt compare. So what do you guys think. Is it comparing apples to apples or no? Thanks

 

A 76mm turbo would pwn a d1sc on peak hp and tq. bottom bottom end will be better with the blower though. There is so many factors ,couldnt fit in the reply box. I saw a stock lt1 run 130mph with a 72mm 7 years ago when turbo where coming up. Just read you sig why are you even messing with an lt1 when you have an 434 with AFR's with an 300. lol

 

^^ I would say in any normal situation the 76mm would come on faster too. People can talk about lag all day long but until you drive a turbo car you won't understand.

Maybe on the dyno from 2k rpms the blower would do a bit better for a short period. But on the street or a proper drag application I'll take the turbo.

 

Tough to answer without considering a ton of factors, but here is my opinion:

D1SC = 1400CFM max (rated for 925hp)

T72 = 900hp

I'd say max hp they are pretty equivalent. This is simplifying it at best though. A T76 would put a raping on a D1SC though.

 

Its funny you would say that cause everyone that knows me says the same thing but when your camaro is a daily driver and you have had fast cars you are always looking for more in your daily ride. But on a serious note in the next year or 2 i see the nova with a turbo and dfi but thats another story.

http://www.youtube.com/watch?v=j3CdnCw6vXE

Here is a link to my buddys ford powered grand national and yes a real grand national that he cut up it runs mid sevens and is twin turbo this car makes me wanna turbo my nova especially when it up on stall and you here the boost coming up it is sick

 

a t76 would rape a d1sc as stated. a t70 is about equal to a p1sc, so id say a t72 would be on par with a d1sc.

However, if your getting a turbo, go big or go home. The "lag" you hear people speak of, only applys to first gear for an automatic anyways.

 

why is that? please explain i have ran many turbo cars and even with my p1sc i can run with the best of them

 

I think the turbo cars you have run have had one of two issues most likely:

1. they are not running to their potential (whether it be tuning or engine combo)

or

2. They aren't running a t76 like we are talking about.

A P1SC will have a hard time pushing an fbody into the low 9's @ 145-150mph... a T76 car with a front mount turbo can do that... and has done it plenty of times.

Any more info on the turbo cars you ran? What do you run at the track or make power wise?

If you set up each car identical (even keep the blower cam) and swap out the P1SC for a t76, a t76'd car should run 1 full second and atleast 10-15mph faster. That turbo pushes way more air than the P1SC can push.

 

My bolt-on LT1, stock internal/heads/TB/3.23/ + PT76GTS @ 8psi pump ran 11.5@125 on the 2nd shakedown pass. Turbo starts to be noticeable in the car at 2000rpms (Sound wise). Not sure when it starts to make boost, but I couldn't say that there was any noticeable lag at all. I foot brake the car to 1100 rpms, and ease into the throttle. Car would 1.7 60' before the turbo, and now it spins a 1.8.

125 trap seems almost too much for 8lbs on a LT1. Am I wrong in thinking this? AFR's were 10.5-10.8 when I looked over at the gauge at almost the end of the 1/4. Boost was creeping up to about 8.5lbs at the end. It was supposed to be a 6.5lb spring, but adjustable. PCM log shows no knock, 42lbers were pretty maxed, Mail order tune from Bryan- PCMforless 26deg@WOT I think.

76mm FTW!

 

Turbo comes onto full boost a lot sooner than a blower does, and, in most cases, has a pretty killer torque curve to boot.

 

From everything ive read about superchargers vs turbos they say exactly the opposite. S/C although they're driven by engine rpm, seem to hit full boost almost instantaneously @ WOT and dont seem to gain much after that from my research and honestly somewhat limited (1 year and 2 different setups) exp. of my own. Turbos and lag have always been spoke of hand in hand as the exhaust flow needed to spool them isnt there at lower rpm. Now I know theres 10 different ways to kill a cow, and turbo technology has come a long way,......but this is what ive always read and been led to believe about the two. Someone please do correct me if im wrong and explain why.

 

Centrifugal S/C's build boost with rpm (compressor is driven by a belt off the crank pulley.... faster the crank spins, the faster the blower turns)... as you increase rpm you increase boost. Example, if you run 10psi pulley, you will make boost like below:

2000rpm 2psi
3000rpm 4psi
4000rpm 6psi
5000rpm 8psi
6000rpm 10psi

A turbo will show something like this:

2000rpm 1psi
3000rpm 5psi
4000rpm 10psi
5000rpm 10psi
6000rpm 10psi

Lag is typically associated with launching the car. With a turbo car, free revving does not build boost. the engine needs load. It's like launching an n/A car until you get traction and the engine get's loaded... then the boost comes on hard and fast.

A roots charger is a positive displacement SC, so full boost happens as soon as the bypass valve closes (when you go WOT).

 

And if your anybody, you either have a stall on an automatic car or trans brake that'll allow you to build boost at the line, or a 2 step on a manual transmission car so you can build boost at the line as well. Lag is pretty much not a problem for anybody serious about their car.

I am going to be spooling an 80mm turbo with a 4.8L with no problem

 

I got a 3k stall. I guess Ill have to pay a little closer attention and do a roll from 3rd gear, because in the lower gears they scream by so fast all I see is the gauge go str8 to 10 psi and stay there when I hit WOT. I am spinning my supercharger pretty quick though, so im sure thats moving the "power range" down in rpm. So that leaves me wondering,....I have one smaller pulley,.....is it actually going to do anything or is the charger possibly already maxed out. Even at 6500 rpm I dont think ive seen more than 11-12 psi.

 

If you guys want a little simpler explanation then convert your boost numbers into airflow. It would look something like:

Blower (linear power curve)
2000 rpm 300 cfm
3000 rpm 450 cfm
4000 rpm 600 cfm
5000 rpm 750 cfm
6000 rpm 900 cfm

Turbo (non-linear power curve)
2000 rpm 300 cfm
3000 rpm 450 cfm
4000 rpm 900 cfm
5000 rpm 900 cfm
6000 rpm 900 cfm

Keep in mind that's a very simplified way of looking at it.