Kfxguy

iTrader: (1)

you beat me to it although yours was worded better. I was trying to type while laughing and just spit out whatever came to mind. He’s trying to push stuff on this guy that he doesn’t need for his goal and then posting 8.90 slips like that’s proving something for a street setup. I’ve seen people go overboard on turbo and be disappointed because a large turbo in a street car (especially someone who hasn’t built a bunch of turbo cars) lags so bad that they end up taking it off and putting nitrous or a bigger motor. I’m trying to keep the guy happy/interested in turbo setups but if he overdoes his first build, that initial impression will ruin it for him. It’s better to start out more on the conservative side until….you know….the disease sets in.

07GTLS

What I get from your guys' posts is that this is kind of like choosing a cam. For a street car, for a cam, I'd always err on the side of the next cam down rather than the next one up, since if you over cam a car that is a street car, it's just not fun to drive and doesn't work well for what it's mainly used for.

OP, your converter is 3300 or so, so you want to get something that matches your cam, the whole combo, the stall you are running, etc. Average hp/tq is what's important, not peak HP numbers.

If it were me, I'd probably go with the smaller turbo. Worst case scenario is it's easier to install and you have more low end torque.

I wouldn't set some arbitrary hp goal. What I do is say my car weighs 3500 pounds, and I want to run 6.40 in the 1/8 at 5000 DA, and then figure out about how much hp I need to do that. I then build everything around that. 1000 hp on the street is a complete waste and no way you will ever get the car to hook anyway. Our hellcat is about 825 flywheel hp and weighs 4500 and with high performance street tires would be a total smoke fest on the street.

Build the engine/turbo to work well in the powerband where you are going to be using it, then work on your suspension.

My two cents. (From someone who has over cammed a few motors over the years, lol)

SkinnyG

As a long-time lurker here, I wade through a LOT of posts here who are after the all-out FTD kind of build. I confess, it does kind of suck me into the hunt for more.

But I also really appreciate the sane/street guys who are building the fun toy or daily. I have zero experience in all this.

My build is '61 C10, 6L/4L80E, stock cam, stock converter, 7875 - I want it to be giggles on the street, with enough jam to scoot up the hilly areas near my house. I have zero intention on even going to the drag strip. I'm sure this will work, and I appreciate what y'all have offered in this thread, despite it wandering around a bit (grin).

Kfxguy

iTrader: (1)

this is a good way to put it.

Too much power on the street is hard to put down

02redchevy

That's honestly what I've been thinking.
Which one is the smaller one though LOL the 7875 has a bigger wheel for the compressor side where the s475 is smaller, but the s475 is larger on the exhaust side where the 7875 is smaller.

Kfxguy

iTrader: (1)

if you get a regular 7875, that mates well with a 4.8, 5.3 and 5.7 (starting to be a little small for a 5.7). Then the gen 2/3 7875 would work well with a 5.7 and 6.0. Bigger than that…I’m not sure because I personally have no experience with running them bigger than a 6.0.
I have no experience with the s475/80 because they are physically way too large to use in my car unless I was willing to cut it up. Which I’m not.
I built my turbo setup back in 2018. I changed the turbo one time to “upgrade” to a billet wheel. Then later on I upgraded the exhaust housing. It’s been trouble free except for at first I had a warped flange on the crossover that was leaking. Once I fixed that, been working fine ever since. It’s daily driver capable but I choose to keep mileage down on it. It’s been on a few out of state road trips. I have daily it from time to time but when it’s cold, my truck has remote start and heated seats so I’m spoiled to that.


my son has a 5.3 Silverado and it’s getting a 7875. To me, it’s a good all around street turbo for non radical setups. They just work. And they are compact. But, yea there’s probably better choices, but more money. My buddy had a precision 7875 and that thing was nasty in a full size truck. Extra cab, full weight daily driver, it was trapping 122mph on only like 11-12psi. I drove the truck on 22psi and it was pretty damn impressive, especially being a full-size, four door truck. He took the kit off because he said it constantly burnt plug wires. (It was a purchased kit from a vendor, whom I won’t name because I have no reason to sling mud).

MY_2K_Z

iTrader: (1)

I value forcefeds opinions a lot on this forum I have read countless hours of his posts since my start in the boosted ls world in 2014. I have no experience on my own car with anything but a 7875. That being said though my friend built his truck with an identical set up to mine ly6 7875 4l80e only difference was our converters. He had some oiling issues and burned up his 7875 and decided to go bigger with an on3 8083 and it was a dog. Could have just been a dud but that turbo made all the right noises but just wouldn’t pull like the 7875 did and was extremely inefficient. After that he went to a China s480 with a t4 housing and it runs decent but it’s a little slower to spoil than the 7875. He has said numerous times he kinda wishes he had just stayed with the 7875. Anyways just wanted to throw in another example. I was planning on swapping to a t6 s480 in my own car but now I think I’m happy with the power it makes so if I ever change I think I’ll just go to a 1.25ar 7875.

ddnspider

iTrader: (26)

I want to make something clear. I'm not bashing the other way to do it or @Forcefed86 .I believe he's a valued member on here with very good insights as he's tried many different setups. We just have an apples and oranges view on what we believe are good street setups.

Kfxguy

iTrader: (1)

I agree.

LS1Formulation

iTrader: (13)

This whole thread has me really excited about getting my car together, although finances dictate that it's going to be awhile. The turbo I picked ( VSRacing 78/75 Gen 2.5 billet with a .96 A/R ) seems like it will be a perfect match for my built 5.3. With the Summit ProLS rods and pistons and 10.4:1 compression on E85, along with hand ported 243s with Ferrea valves, this should be an absolute beast of a street engine. Especially with a T-56 behind it.

laytoncamaroz28

iTrader: (10)

Lots of good info here. I started 10 years ago with the hurricane Benita, 78/68 on my 5.7 Camaro. Blew the ls1 up and with to an lq9 with the on3 78/75. Never pushed it hard but ran a 10.2@131 with it. Swapped to a precision 76/75 and ran a 9.58@141 with 1.45 60 at 3800 lbs on 18 psi. both turbos spooled great with our 5000 da but seemed like the precision made a lil more power. Then swapped to a forced inductions billet t4 76/92. It made WAAAY more power. But was very difficult to foot brake with our da. And was very laggy on the street. Ended up going 9.58@145 with it and swapped back to the precision. Makes less Power but more fun to drive on the street and I didn’t wanna swap to a non lock up converter to help spool. And one thing about stock4.8 nova setup is that he’s running a powerglide which makes footbraking much easier with the tall first gear. All about the cars setup and what you want outa it. But I really the 76/75s compact size and power it can make with being that small. I’d be really curious if gen 3 vs78/75 would out perform it.

Forcefed86

iTrader: (4)

Both you’re statements make no sense, and clearly show a lack of experience. Who are you two say “no one cares”? If someone has no experience comparing the turbos being discussed (not even with the different T4’s) Why even comment? With no direct experience, there is nothing of value to contribute. Worse, you downplay the opinion of those that do have direct experience.

It's not “my own setup” I’ve worked on many… and had direct experience with what the OP wants… Have either of you run a 370 with a T4 and switched to a T6? Instead of arguing, those without experience should listen to those that do. Or just not comment. I have zero issues with someone disagreeing. I only ask that if you do, have the data and experience to argue like an adult. What I hate to see is someone new being steered the wrong way by those without experience. Band wagon cookie cutter combos are rarely ideal. If I had known what I do now, it would have saved me a lot of money and time over the years.

You both also clearly don’t understand the point made with Stock48’s slip above. I could care less about impressing either of you. He’s at 3350 with a 6.0 trapping 158 with a T4. That about 1000 crank HP (around 800whp which is the OP's revised target. was originally 1000whp) with the S475 T4. He was also OUT OF TURBO at that point, only running 16lbs. The turbo would make more boost, but it was so inefficient, it slowed his times. What I’m saying is I’ve never seen a 78/75 do that. So if the OP is 100% set on a T4 the S475 is a better option than the 78/75. This example clearly shows that the T4 housing and T4 wheel are tapped out. Which also proves a T6 on 370 is hands down a better choice. If the OP is stuck with a T4, run the larger Exh wheel versions. A 75mm wheel is too small.

Forcefed86

iTrader: (4)

The T4 S475 has a 75mm wheel too. Its a 83/75. The S475 is just a better design with more efficient wheels. The guys talking about size differences are confused. The old gen1 78/75 is the only on that is smaller and it is grossly undersized/powered for a 370 w 800hp goals. Any of the new 78/75's that actually perform, have the exact same sized compressor cover as the S475.

Kfxguy

iTrader: (1)

well that’s why I’ve been saying “gen2” and “gen 3” in my posts. I even went so far as to break it down that a gen 1 7875 would work good on a 4.8/5.3/5.7 and then on a more radical 5.7 and 6.0 use the next gen units. I don’t think anyone recommended a regular gen 1 7875 for his combo.

btw, lots of people always say they want 1000whp. That’s easy to “say”. But you put them in a 700whp car and that will be plenty. 1000whp isn’t a good recipe for the street and I take that goal for people building a street car, with a grain of salt. It’s better to err on the more conservative side and having a nice driving vehicle they can enjoy than to go ***** out from the onset and not be happy with it.

ddnspider

iTrader: (26)

Do you have experience swapping a Precision PT101mm for the G5XR 105mm race series turbo?
Do you need to stick your hand in a fire to know it's hot?
I have direct 7xmm T4 turbo swapping experience and so does @Kfxguy and there's more than enough data available to show what does and doesn't work. You're so hard up on larger T6 turbo's and trying to prove the larger T6 is better by posting stock4.8's 8 second slip that you don't even grasp the arugment. We're not arguing the T6 can run a fast ET and make more power and is more efficient. Let's try the overt route:

I REPEAT- WE ARE NOT ARGUING THE T6 TURBO CAN RUN A FASTER ET, MAKE MORE MPH, MAKE MORE PEAK POWER, AND IS A MORE EFFICIENT TURBO. Better?

We really don't have anything else to discuss because you're making strawman arguments. You don't care about impressing anyone but you keep replying with information that has nothing to do with our stance. Give me more data showing how a T6 is better at racing and I'll keep responding with it's not applicable to our argument. I'm not sure how else to say it. All your information is not relivant to our argument. This 100% proves exactly my point. We have different goals, different build methodology, different viewpoints on what's a track car vs. a street car, etc. And that's cool. Just stop trying to force others to agree with your goals and definitions.

Forcefed86

iTrader: (4)

The size difference was mentioned... A gen2-3 etc is the same size as a t4 S475. So packaging a T4 S475 is no more difficult than the newer 78/75's. They use the same huge compressor cover. And the T6 units use the same sized compressor cover, which is the largest part of the turbo. So if you can fit a NEXT gen 78. You can def. fit a T4 S475... and likely fit a T6 S475 as well.

I don't tell people what they want. I let them tell me a goal, and I explain what I *think* is the bet way to get there.

Forcefed86

iTrader: (4)

Just wanted to say I don’t feel bashed at all. Perfectly happy discussing this stuff with anyone, I think we all respect each other here.

What I think is overlooked here constantly is the fact that the OP is talking about a “built” 370 and wanted 1000 whp initially…. and is “settling” for 800whp. That doesn’t sound to me like someone who wants a tapped-out turbo with no room to grow. Or a turbo that’s tapped out well before 800whp. If this was a “burnouts and ice cream:” SBE build, something like a 78/75 at 650 crank works great. But that wasn’t the power goal stated. I’m merely stating the turbo I’d use to hit that goal, since I’ve used most of the turbos mentioned. Which is the question that was asked.

Anytime you have twice the drive pressure behind a turbo it will spool more quickly. That doesn’t mean its efficient at making power. It doesn’t mean you will accelerate form A to B the quickest. Which IMO is what matters the most, street or strip.

If we are talking the gen1 “Small” 78/75 here that unit would be tapped before the goal was hit. My argument is that the S475 is no larger than the new gen2/3, next gen, blah blah 78/75’s. And performs better in my experience. A modded T4 S4xx with the larger 87/96 exh wheel is the way to go if he is sticking with those power goals on a T4 370.

Don’t take my word for it… call up Jose at forced inductions and ask if he’d suggest any t4 turbo with a 75mm exh wheel for a 370 with an 800whp goal. He’ll tell you the same thing I am. There are better units that will make much more power per pound for your setup.

As with anything performance, you generally can’t bolt something on and have it be ideal. You need to have all the parts working together. I can see someone bolting on a large turbo to a setup not designed to accommodate it not being happy. If you take the time to do that, a T6 S4XX turbo isn’t disappointing in anyway in my experience.

ddnspider

iTrader: (26)

Funny you should mention that. I asked Jose over a decade ago what his recommendation was for a street car 383. A 76mm or an 80/88mm, both Precisions. He recommended the 76mm turbo over the larger turbos for a street car 383.

Forcefed86

iTrader: (4)

Again, you don’t make any sense. I have direct experience with what the OP is asking, you do not. You are the one that is going off on a tangent spouting random nonsense, not me. Everything I said directly relates to his question with examples. I also said several times I understand if the T6 isn’t an option and suggested a better suited T4. Hopefully one with larger Exh. wheel.

Information is king. To turn down experience from someone that’s done exactly what you’re trying to do is just ignorant. What is it that you are arguing? You state that the T6 is better in many ways. Yet you’ve never run one and argue it’s not in others? Based on what? I’m telling you I have done it and its better all-around in his case. Yet you still argue against what I’m saying with ZERO data to back it up. A smaller turbo doesn’t always mean quicker A to B acceleration, period. Isn’t the goal always to accelerate from A to B the quickest you can?

The fact that a car was at a drag strip only means they have more data points for comparison. It’s perfectly relevant to racing a street car. Stock48’s nova won drag week! It was the definition a street “hot rod”. Left on the foot brake etc… Posting examples that show a smaller motor is out of steam using a t4 turbo that performs better than the 78/75 isn’t relevant? Give me a break… it couldn’t be more relevant! It clearly shows even an S475 T4 is too small for a 6.0. Until we see the 78/75 trapping 158 @ 3350lbs on a 6.0 that is… Maybe the new ones have. I only said I haven’t seen one yet.

I don’t tell people what they want… So if someone tells me 800whp on a 370… I tell them how to do that. Just like anything performance they will need the correct supporting parts and combination to make the most out of their selection. A decade ago the turbo world was VERY different. Call up Jose right now and tell him you want the best running turbo for a 370 and want 800+WHP. He won't suggest a 78/75... ever. The T4 Precision performance units all have larger exhaust wheels that are very efficient. They are a far cry from a VSR 78/75.

ddnspider

iTrader: (26)

It's 100% irrelivent because they're totally different operating conditions from what I'm talking about. You are assuming constant WOT and are completely disregarding transients and low rpm/part throttle. I care about boost threshold, boost and throttle at tip in, rpm at max boost. Boost at part throttle. My real street cars don't have a 1/4 mile of road with no cars. There are no 2 steps, T-brakes, loose converters, or light weight (3300lb is light), or 7500 rpms to make power. What I build drives like an OEM would have made it. It's about low rpm transient response and all the torque at low rpm. Spinning aint winning, I get it. But I want what an OEM would have built, just more. It's a Hell Cat in turbo form. That is fun TO ME.