Torqueshaft

Have a debate going with some buddy's over which CID would be best for the "cheap" b/w s475 (75/96 1.32 a/r)

Assuming all three have the same heads(799)/cam(spec. for turbo)/compression(9.1) running intercooled on 91 with meth.



1) 5.3

2) 5.7

3) 6.0

Curious to see everyone's choice and why.

Beanslsxnova

iTrader: (1)

In my opinion with a good cam spec'd for the combo that turbo will work good on all 3 engines. I've had that exact turbo on a lq9 6.0 and now a 370 and it's been awesome on both. It's more about the set up then the CID with these 3 v8's and that turbo.

HexenLord

Won't be much of a difference in boost between the three. Maybe a couple more psi to make the same power with the 5.3, but alas, it'll still make the same power. You're only looking at a 5% increase in displacement from 5.7 to 6.0. With boost, this is almost trivial.

The 5.7 should be removed. The only 2 contenders here are 5.3 and 6.0. The 5.7 engines are far more expensive than either without much reason. The 5.3 can be had in aluminum pretty cheap, and are plentiful and proven. The 6.0 is more expensive and more scarce, but opens up option for the L92 and LS3 heads which is where most of the power difference will come from when comparing to the 5.3. The 5.7 is usually reserved for the actual LS engines and carries an unwarranted price tag when going boost. It won't be anymore reliable or easier to replace.

Torqueshaft

Thank you both for your input.

We understand that it would work on all three engines.

We have access to all three (well the 5.7 would be made out of a scored 5.3 block and some ls1 rods/pistons we have laying around, so it was thrown into the choice as a "middle" ground.)


The debate centers around is one more optimal for that size turbine/compressor/ar ?

It's understood that the difference is most likely small but in theory one should be a better fit.

Some of the things that have been debated are...

Turbine lag on the 5.3 vs the others.

Compressor side running out of steam on the 6.0 at high boost levels.

Advantage of 5.3 at higher boost level.

Which one would be closer to the the "sweet spot" on the compressor map at max boost ?

This and a bunch of other things were just being thrown around while bench racing and having a few brews...

Figured it might make for a good debate on here, as a lot of people use this turbo because of it best "bang for the buck" status.

Oh...And just to make it more fun...

Lets throw in the other "cheap" b/w turbo.

The s475 (75/83 1.10 t4) into the mix.

HexenLord

Boring out a 5.3 takes away the best part of it, the extremely thick cylinder walls, and names it bad for boost. 5.7 is pushing the limits of the max overbore for most 5.3s, especially boosted.

So once again, the real contenders are the 5.3 and 6.0. Either turbo is going to be 8 second capable on either engine, why complicate things to find out which one inches out the other? The 6.0 has access to rectangle port heads and will have more torque out of boost. That sounds like two good reasons to me.

Either motor with stock or small cams, stay with the smaller turbine. Cammed? Bigger turbine.

mrstepheneades

Im all the way stock ls1 with a cam. 800+rwhp and 20psi on that exact turbo on my setup.

Torqueshaft

HexenLord...

I think you are possibly missing the point of my post...

It was intended as more of a academic exercise to get the mind juices flowing.

I agree with you on the two reasons you gave for the 6.0. And you touched on one of the advantages of the 5.3... thicker cylinder walls.

To a degree I also agree with you on the "stock or small cams, stay with the smaller turbine. Cammed? Bigger turbine" theory.

Except on the 5.3...With the wrong valve events it's possible to make it lag more.

We will have to agree to disagree on the bored out 5.3 as I know someone with a forged rods/piston bored out iron 5.3 that has been been running as high as 26# boost and 1100+ rwp for the last 2 1/2 years without a hitch...Oh and it is his daily driver and runs it around 18# for the street.

smokeshow

iTrader: (17)

5.3 will make the most power. Reference: compressor map.

Torqueshaft

Got a link to the maps ?

Only on I could find for the 75/96 1.32 turbo was really small...When you blew it up to see it, you couldn't read any of the numbers.

mrstepheneades

José told me the 5.3 would make more boost than my 5.7 on this turbo.

smokeshow

iTrader: (17)

This is for the S476. While not exactly the same as the S475, the lesson to be learned remains the same: the turbo will move more air more efficiently at higher pressure ratios.

https://lh4.googleusercontent.com/-O...6_comp_map.jpg

slowlsx

iTrader: (28)

I personally am thinking of doing a forged 5.3 with 12 to 13.0:1 compression with a 76R and 96mm turbine on E85.

I see several advantages of this

Sweet spot on the compressor wheel (75-76mm)
torque of a larger cube motor
Lower backpressure of a small cube motor
Thicker cylinder walls and shorter stroke of a 5.3
Higher Rpm engine

How much power do you gain per point of compression? I thought it was 4%??

If thats the case going from 9 to 13 to 1 is a 4 point increase which is roughly a 16% increase in power. That would make the 5.3 pretty close in power in terms of a 9 to 1 370 with all the advantages I mentioned.

Blown06

iTrader: (32)

I gotta disagree there.

Torqueshaft

While I have run 12.1 compression on a blown alcohol (methanol) BBC, I don't think you have a chance of running that high of compression on e85 with any kind of boost or timing.

Second...A 5.3 has the same stroke as a 5.7,6.0 or 6.2. The only one with a shorter stroke is a 4.8.

slowlsx

iTrader: (28)

Strange I have herd of other cars running more than that with ethanol.

HexenLord

I've seen 13:1 on a turbocharged setup before with E85. The guy went to the extreme to keep IATs down and was spraying straight water instead of a water/meth mix. It worked, but he admitted it wasn't an ideal setup, as he had to keep the boost down at higher RPMs with his cam because he was seeing some signs of detonation.

I've never run this high. Most I've ran is 10.5:1 with E85 and didn't see any issues. I wasn't exactly pushing the envelope, either.

slow67

iTrader: (2)

This car is around 12:1 on E85

Torqueshaft

I'm impressed...

What type of intercooler is he running ? A2A or A2W...

Any idea on the timing at that boost ?

I am real familiar running with boost on methanol but have never had the chance to mess with e85 but would love too. (not available in my area)

I am going mostly by what I have read about other peoples experience/set ups.

smokeshow

iTrader: (17)

If you have octane at your disposal...compression is your friend.

Torqueshaft

Yep...

Back in the day... Used to get 100/130 or 115/140 av gas depending on what engine/car I had.

Used to drive right up to the pump at the airport and pump it in...

Always loved the smell of it...Miss those days.

By the way...What is the octane rating of e85 ?