LS4 w/ T76 as ultimate choice

[Atilla the Fun]

If you want a truly fast Fiero, and no figuring out how to get there, then read this:
http://www.ls1tech.com/forums/conversio ... hread.html
Then get you an LS4 and 4T65E-HD, have the T65 "built" and otherwise, copy this recipe. It proved good enough for nines in the quarter mile. For street driveability, I'd say get a pair of T4S04 turbos instead of a T76, but that's another $1000.
In fact, this is why I decided on a twin turbo LS6 and 600 rwhp, and HP was the one thing stopping me from knowing how to challenge the Enzo. But I digress. It's a great build, and it can give you the grunt you need to put your Fiero into the 9s, once you fix everything that this much grunt will break. I'd suggest a Quaife, and a widebody kit for the rear half of your Fiero, to house the 275-width drag radials.

[Shaun41178(2)]

http://www.youtube.com/watch?v=WftiQQcrH7A

[Aaron]

I just don't understand, why not go with the aluminum block?

[Atilla the Fun]

Oh! the glory of the boosted LSx killing an Enzo and a 'busa! Thanks for the video link. Aaron, the LS4 is aluminum block, but the other aluminum-block LSx engines are commanding a $2500 premium, even though the bare block can be had new for only $1000. And the aluminum-block RWD 5.3s are extremely rare at all, let alone for sale used. 88 pounds is a small price to pay to save $1000, plus all the gaskets to swap your parts into the aluminum block. The stang I linked to did use a truck iron-block 5.3, with truck cast pistons, and then spent thousands extra elsewhere, on things that are NOT necessary, so I too don't understand why no aluminum block or forged pistons, but the thing of interest to Fiero guys is that a cast piston 5.3L LSx, which the LS4 is, can make the power to push a 3000 pound car into the 9s, through an automatic, without spending another $1000 to put forged pistons into the engine.

[Atilla the Fun]

BTW, Has anyone done 9s on stock pistons with an L67? I doubt it.

[AkursedX]

BTW, Has anyone done 9s on stock pistons with an L67? I doubt it.

Actually ZZP's twin turbo GTP did 8's on a stock bottom end.

[Atilla the Fun]

8s!?!?!!!? I'm going to need a second Fiero.

[crzyone]

When trying to build a car to beat an Enzo, every ounce of weight counts. 80lbs is a huge difference.

I've become obsessed with weight now that I'm big into road racing. I care that my new hood weighs 10lbs more than the stock hood, but that's part of the cost of a widebody kit. I saved 80lbs taking out my all wheel steering system though.

My old (stock) GTR weighed 3250lbs. My goal is to get my current car down to around 3000 or less.

[Atilla the Fun]

The Enzo Challenge combo is aluminum block, I'm having my LS4 bored and honed to 3.905".

[darkhorizon]

A S2 3800 in a datsun is in the 7s with a stock block, rods, pistons.

Twin turbos are pretty much gay in most cars.... Singles are going to make more power every time, and when you only have 1 turbo to spool, typically street manners is better.

[The Dark Side of Will]

www.exvitermini.com

Yeah, that guy would totally make more power with a single.

Are you speaking from experience here, or just talking? Not seeing how a single would have better street manners than twins.

[Aaron]

Isn't the reason most companies go for twins is for the superior response? At double the price for the turbo hardware, it certainly isn't an economical choice.

[Series8217]

Isn't the reason most companies go for twins is for the superior response? At double the price for the turbo hardware, it certainly isn't an economical choice.

Correct.

when you only have 1 turbo to spool, typically street manners is better.

Incorrect.

[Atilla the Fun]

A S2 3800 in a datsun is in the 7s with a stock block, rods, pistons.

Twin turbos are pretty much gay in most cars.... Singles are going to make more power every time, and when you only have 1 turbo to spool, typically street manners is better.

You have that backward. 2 small twins far beats a huge single. Learn to understand the ramifications of what you see on compressor maps, then contemplate a mild 5.3L with twin T4s04s versus a single T76.

[Atilla the Fun]

Isn't the reason most companies go for twins is for the superior response? At double the price for the turbo hardware, it certainly isn't an economical choice.

Exactly. A new single T76 runs $2200, while twin T4So4s new will run $3200 for the pair. That's $1600 each.

[Aaron]

Yah, the cost of turbochargers increases very mildly with the increase in size, certainly not in proportion. I know the R series Garrett snails were pretty much equal across the board. We paid $1150 for the 30R, and $1200 for the 35 with a T4 housing.

[darkhorizon]

http://www.exvitermini.com

Yeah, that guy would totally make more power with a single.

Are you speaking from experience here, or just talking? Not seeing how a single would have better street manners than twins.

Experience...

Buddy with a terminator had decent T76 GTS and made 800 all the time... put on 2 60s and he made ~100 more horsepower (thats with like, 40% more flow available), and lagged a ton more... which i guess doesnt matter so much because he never raced from anything under 60 anyway. it was faster, but he just didnt like the idea of going T6.

Did a single T6 setup with my buddies built bigshot 358 SBC.. Spool was way better for traction on normal tires (boost comes up way slower than with twins due to inertia of the big heavy wheels), and was a faster car from a 60 roll due to the fact that it just made more power, with less flow according to the compressor maps.

I wont lie that twin T4s are a damn decent alternative to the T6 setup, but if you have the cubic inches, no reason not to go single for the pure manners of it, and the power curve is more manageable to me. The single most important part of the single vs twin debate to me is shift lag on a twin turbo setup is quite significant compared to a single turbo setup if you are running a street car manual transmission.

(its sad because if I ever build my drag car... It will have 2 60s on it.... Only because 2 60's is a good $1500 cheaper then the bullseye I want)

[The Dark Side of Will]

Did a single T6 setup with my buddies built bigshot 358 SBC.. Spool was way better for traction on normal tires (boost comes up way slower than with twins due to inertia of the big heavy wheels), and was a faster car from a 60 roll due to the fact that it just made more power, with less flow according to the compressor maps.

I wont lie that twin T4s are a damn decent alternative to the T6 setup, but if you have the cubic inches, no reason not to go single for the pure manners of it, and the power curve is more manageable to me. The single most important part of the single vs twin debate to me is shift lag on a twin turbo setup is quite significant compared to a single turbo setup if you are running a street car manual transmission.

Ahh... so "street manners" to you means staying out of boost... That's ok with a built SBC because it has torque off boost. I saw a Supra single dyno sheet a while back in which had 150 ftlbs at 4000 RPM and 550 ftlbs at 5000 RPM. I don't call that a manageable powerband.

Think about what you're saying here... In one paragraph you say that the twins have worse street manners because they build boost faster, but in the next paragraph, you say they're worse at the strip with a stick because of transient response. Figure it out, mang.

[Atilla the Fun]

Lag is mostly in the distance of the turbo from the exhaust valves, and the size of the hot side of the turbo. In my case, I'm challenging the Enzo, and to run 215 mph, I'll need power to 6600 rpm in 6th gear. My 1-2 upshift costs me 46% of 6600 rpm, so I don't need full boost until nearly 3600 rpm. 3600-6600 is reasonable. It'll seem less responsive down around 2000 rpm, and yes, the unboosted torque of the LS6 is adequate there anyway, but If I didn't need that top end, I'd choose smaller hot sides to have full boost by 2500 rpm. It all depends on what you want. Just map it out, evaluate it, refine it, re-evaluate and re-refine as needed until it's rrealistic and workable, all while saving up your money, then start buying and building.

[crzyone]

You can only compare twins to a single that puts out the same air flow. The twins will always have better response.

The difference isn't as large today as it used to be with new twin scroll BB turbos but twins still have better response in general.

On a V engine the twins will be MUCH more responsive, the turbos can be right on the ends of the exhaust manifolds or headers. With a single there will always be long exhaust routing to get each bank to one turbo.