So get a proper muffler? My 6.0 made 475whp and well over 400wtq for a wide range before being turbo and sounded damn near stock. I would not mess with a turbo for under 500hp, totally not worth the hassle. A single T3 will be more of a restriction then a power adder at that point.

 

@Slow Sedan
Hindsight is always 20/20 and a 6.0L would have been a better choice but I already have an LC9 (5.3L). Ditto for a T3 turbo that needs a rebuild. I'm used to hassling a solution, I'm a big fan of repurposing what I already have

Does everyone agree that my humble performance requirements are unattainable with any T3 on an LC9?

 

Is it possible to get 400 horsepower out of a 5.3 with a T3? Sure. Will it have a nice powerband? Probably not.

You have an LC9. You're about 80 horsepower away from 400 at the flywheel.
That's a set of 1 7/8" long tubes and almost any 22x/22x cam. Done.

 

If you want to re-purpose, why not buy another GT35? it's a $160 purchase. Not gonna break the bank and then it would work well.

 

@Forcefed86
What will my expected torque curve and final HP number look like with that single snail on an LC9? Assume a 3" trail to dual 2.5" exhaust. I mentioned it before but I'll restate it, I want to maintain 400ft/lbs for at least 3000rpm. Given the high VE of the LC9, I assumed this was fairly easy to get with a small turbo but I'm now seeing some of the potential problems.

@JoeNova
I've been looking a little further into your first reply in this thread and am beginning to understand your point but given that I'm planning on no more than 9psi, even a back pressure of 1.6 bar seemed acceptible to me. I didn't realize just how much hot gas needed to move over 5500rpm. The 4000rpm is a pretty fair estimate of where the efficiency would start to drop. Much props but stop dissuading me from a turbo, it's annoying

 

I honestly don’t think it’s worth the time/effort.

If you go through the trouble of adding a turbo... run a charger that’s suited to the task. You can pick up a GT45 turbo for $180 shipped that would work extremely well. Or grab another gt35 like the one U have. If either of those purchases “blow the budget” then you shouldn’t be looking at turbo charging anyway. That’s peanuts relative to what the rest of the stuff costs... and all the effort involved. Things like big exhaust systems aren’t needed. For the cost of a full 3” to 2.5 dual system you could buy the correct turbo. Then run the factory exhaust and still be on top.

 

@Forcefe86
I suppose I should explain my thoughts better. Please feel free to correct any wrong notions. When you go above 450ft/lbs of torque, your driveline and clutch choices become exponentially more expensive. The same cost escalation happens with fuel pumps, injectors, pushrods and valve springs when you're over 500hp at the wheels. Speaking of wheels, that kind of power usually means bigger tires and other miscellany that makes your suggestion much more expensive than my humble plans. An engine that gives me and nice flat 400ft/lb. torque curve that goes from 2000-5500rpm that tops out at ~450hp at the wheel would be adequate for my needs and if I can run this setup on pump gas, that would be ideal for my application. The car will run a stick axle with a watts link in the rear and a macpherson up front. Is it anything to write home about? Not really but at ~8lbs/hp I'll be amused with it
I'm committed to an LC9 and a cam that'll get me the numbers I want on that block is not likely to do it as elegantly as a snail, IMHO. I looked into the solution suggested so I believe this is an informed comment. A pair of GT35's creates fitting issues so it needs to be one unit but it will have a decent intercooler to help bring up the power. The GT45 looks like it could be the solution but in what trim?.

 

I don't think you are going to have a flat 400 lb-ft torque curve starting at 2k and staying there to 5.5k with a turbo. It is unrealistic. There will be too much heat and back pressure. A better bet might be a small positive displacement supercharger. Might not even need a cam....but since you already have the turbo....hmmmm.

 

I'm not so sure it is. One of the main reasons to insist on a turbo over a cam was the relative ease of obtaining a flat torque curve. As long as the turbo can start quickly and have sufficient gas throughput, judicious use of routing and pressure regulation should get it done. Even a big A/R T3 would spin up plenty quick enough on my LC9 but as JoeNova correctly pointed out, the efficiency would be awful on the top end even with the piddly 9psi upper limit. The T4 family is more likely to yield my answer if I can get one of them awake by 2000rpm. Is there a resource that correlates octane requirement to boost/compression? It would be handy to plug in the boost to a given compression for the octane requirement.

 

The base cheap gt45 only comes in 1 trim with the 69mm comp. Wheel. Just type gt45 in on amazon. its only 170 shipped now.

 

@Forcefed86
Thanks, I saw them. Any input on my other questions?

 

Sure turbos are better, no argument there. My point was the cost/effort VS performance for a 400hp goal isn’t there with turbo charging. And the unit you have is a poor fit.

I was under the impression you wanted to use what you had because you were on a budget. Which is why I suggested the Gt45. IMO with a properly sized turbo at 4-5psi you could hit 400 without an intercooler. Save some time/$ and pick up some spool time. The GT45 is the cheapest option for a single that will work by far. But it’s not ideal for what you are doing. It has largeish exh. housing and turbine wheel. You can get a .68 T4 61/65 or 67/65 for from VSracing for $250-320. Those would work better, but cost quite a bit more.


Point is the turbo is the cheap part. The fabrication, fuel system, driveline, and engine management are the expensive parts. And whether you run 5lbs or 20lbs the cost is approx. the same.

 

Quite true. But it still has to be sized properly for the engine and rpm it is being used on. Your idea could work with a lot of work-arounds to bring in the boost early and keep it limited. And you will still end up with an inefficient turbo that is going to have massive back pressure issues and heat production. I am not sure if the compressor will be so inefficient to heat up the charge air to a dangerous level....but I am reasonably sure the turbine will back up enough to have the exhaust nearly glowing hot in a race vehicle.....and you said road race.....how long are these races? Heat management might be a nightmare.....

 

Like I said before for road race and under 500hp, zero chance I would go turbo! I would throw some TFS 220 on that thing for $1500 along with a nice cam and springs for $600 and call it good, beat the ever living snot out of it for years to come. The 7500 RPM range will be a LOT more useful then whatever he cares about making at 2000RPM.

 

I'm fairly certain that we are at the point of, just do it and let us know how it goes. If you have the turbo and the skill, you can toss on a T3 and swap to a T4 relatively easy after your "learned the hard way" moment.

 

Some answers: I wouldn't race more than 100 miles, I'm an amateur. The car also needs to do street duties. Is the TFS 200 mentioned a Trick Flow type head? I wasn't aware 7500rpm was attainable in an LS without some cylinder/balance work. I'm not looking forward to learning any hard lessons. I can probably flog my LC9 for a 7L with an additional $1500. That looks like the cheapest way to get what I want. If the last word has been said on getting what I want with a turbo LC9 economically, I'll drop out here. Thanks for helping me sort out my plans.

 

Your reasoning is what confuses us. You want instant spool. That's fine and all, but do you know how fast 400+ horsepower goes from 1600-2600 RPM? Pretty damn quick. You don't need it to spool that low. This isn't a 4 cylinder. You're going to make great torque at any RPM without boost. An LC9 is capable over making 4 digit power/torque on a stock long block. The difference between 450 and 700 horsepower on a turbo LC9 is almost $0. My billet 80mm turbo spool so fast and hard on my 5.3 that it'll put me sideways at 60 mph by the time I get my foot down. I'm having major issues comprehending how you think you need boost on a turbo V8 at 1500 RPM for street duties, unless this is a 5000+ lb truck.

 

lol probably right...

Yes the trickflow work well and 7500 is easily obtainable with the LC9 internals despite what head you use. I just mentioned the TFS to ensure you meet your power goal and I would get a better intake as well, let it all breath and it will reward you a lot more then choking it up with a single T3.

 

 

@nocooler
Your suggestion prompted me to look at something completely different. GM puts a hot little 2.5L four banger in the Cadillac ATS. Does anyone happen to know if it has the same footprint and mount as the LS? I figure it would be at least 100lbs. lighter, make 200hp before boost and could be a proper fit for a T3. The 5L Windsor, anemic and outdated as it is, doesn't change the backpressure issues noted by everyone here.

@JoeNova
I've never thrashed 8lb/hp around a track in a car but I have lots of experience handling thrust on my FZR1000 bike. I shouldn't be too much out of sorts with 400ft/lbs at 1600rpm which by my estimates is only ~120hp at that point, not the 400+ described in your post above. Perhaps I didn't understand what you meant there. Until I actually looked at what happens in a turbo setup, I didn't get what you were trying to tell me from the beginning. Sorry about that. I know I'm a bit pedantic but I like knowing as much as I can about what I intend to do before doing it. Forgive me if my questions annoyed any of the other participants here. Truth said, I'm grateful for all the input.

I have only recent experience with a turbo and that is on a Ford SVO. My previous investigations on getting that 2.3L Lima over 400whp were fruitless and so I looked into an LS. A complete LC9 in good shape came my way and I bit on it. If I were to put 700hp into a Fox body, I would immediately have to upgrade the 8.8 rear to a Torsen then fit a T56 with a heavy duty clutch. That would have been too big a headache. I just want a nice flat 400ft/lb. torque curve that lasts for most of the rev range and tops off at ~5600rpm. No phrenetic rev climber, just a nice, polite Q-ship with some ***** when required. I thought I could get that with a little turbo on the LC9. I'm glad I asked here before taking that step. You guys know my aims and the things I won't change on the platform (exhaust, 8.8 diff, etc.). So far, all the answers provided point me to NA. If the Trickflow heads and intake from a hood scoop can get me >3000rpm of rev band with 400ft/lbs. of torque and 420hp to the wheels on my LC9, I'll consider this matter resolved. If not, let the suggestions pour forth