SuperC

Hello C5 friends,

I have had many turbo cars but this is my first experience with corvettes and ls1s and auto trannys. Everrything I have owned in the past was AWD FWD and mostly Inline 4 cylinder.

I am excited to finally get into my dream car, an early c5 with targa top.


I live pretty close to UPP and so I am going to install their Twin Turbo kit with the 6182R turbos and I have several questions about what other mods I should do that will give me the best bang for the buck so that I dont waste time and money on negligable upgrades to the LS1

Currently
I have a stock 1997 Automatic Base corvette with 0 modifications

Tuning
After I install the UPP twin turbo kit, I plan to have them dynotune the car using HPtuner software. I want to make sure I have everything in place to get the most out of that tune.

Here are some questions I have.

Gears
I hear people mention I have low gearing in this "old" C5. But under boost, what is the right gear set to use? I am not going to be dragging often. I just want a really fun and fast car all around but Im sure I will show up the 1/4 to see how the car fairs but its not my goal to run this or that. It is much more important to me to enjoy cruising on the highway between 30 and 80mph so I dont gears that are going to be running at 6000 RPM at 80mph

Injectors
What Size injectors should I use if I am shooting for 650 or so HP
Thinking 60lb or 80lb with an E-85 tune aggressive and a mild second tune on 91octane.

Intake flow
Will swapping the LS1 Intake manifold, TB and MAF make a difference?

Heads
Are they worth swapping to 243s? What kind of gains can be had? Or should I leave them stock?

CAM
Best cam that will no be too lumpy and drive like stock? I would like the car to be fun but idle well.

Exhaust
Obviously the intake and exhaust systems will be part of the kit but what about cats and catback? I was reading that most cat backs just sound better but dont offer power gains. Is that different under boost? Would the Z06 TI system be less restrictive? Any favorite high flow cats?

Suspension
I beleive my shocks are worn out and I was planning to go with Bilsteins HD or sports but I want a mostly stock ride without wheel hop. I drive 5 miles of dirt roads so I want the most comfortable ride possible. Should I go Z06?

I know because I have a 97, there were many improvements to the LS1/LS6. Any suggestions about the best part swaps for a boosted application? I kind of asked this question already but I would love to hear thoughts...

blackmachdown

I'd stick with the 5871 turbos on a stock displacement ls1, if anything I'd upgrade to the ballbearing ported housing. I have 6182r on a built 6.1 liter and I miss how fast the smaller turbos spooled.

If your keeping the auto I'd get a stall and shift kit (not familiar with corvette autos) to ensure your shifts are fast and bleed off minimal boost.

I'd upgrade the rear end to a 3.42 max anymore and you will be spinning in all gears.

Go for the 80 lb injectors if running with e85. They also have a boost referenced fuel system I would recommend getting as well.

Ls1 intake will be good enough, the intake doesn't matter as much under boost.

Heads: I think you can hit 600 hp with your stock heads and e85 if you are deadset on the 650 then I'd get 243 heads or even 317 heads (lower compression add more boost)

Cam: LS6 cam or a custom turbo cam

Exhaust: have them give you a 3 inch straight pipe all the way to the back it will give you the most power. It is loud but not crazy loud. My long tubes with a catted x pipe and bb bullet c5 was louder than my three inch straight piped with dynomax race bullets twin turbo z06. As far as cats go with kooks green cats or thunderbolt racing 3 inch cats

On edit: you have a 97 I'd look into changing out your pcm for a newer one from a 99+ they are better to tune with

Look through my post history here I started with a bonestock z06 and upp turbo kit and now I'm rocking their upgraded turbos, built motor and making significant hp now!

Turpid porpoise

Personally I would not spend the money on the exhaust, cam or heads and I would put it towards motor/diff mounts, trans brace, and maybe a built diff.

600 is not a lot on a twin turbo ls1 so i dont think you will need heads, cam or exhaust just let the boost make the power for you. That way you maintain a smooth ride and get the power you want with some added durability.

0CK@UPPCOS

I'm going to go ahead and throw in my .02 here.

First thing you need to do if you want anything over 450-500 is swap out those connecting rod bolts. Pre 01's are weak and will not last.

80 or 96lb injectors minimum if you're going E85, and one of our fuel systems like BMD said.

3" exhaust all the way back, for what you're looking for this isn't really optional. Our down-pipes are already 3" so trying to condense that back to a 2.5" creates ALOT of back pressure. Most cars it's to the tune of ~80whp on only 7psi w/g pressure.

A cam would help (but not the end of the world), heads would also help a little but are not really necessary (we can just increase the boost to make up the difference). If you're going to go with a cam, don't waste time with an LS6, just get a custom one and call it a day. Spinmonster cams are the ones we usually run.

Running a stock 5.3L with Spinmonster cam on E85 through a 4L80, I've pulled 780whp before I started running out of fuel and twisting my frame on the dyno. But the engine was also after 01, so I had the better rod bolts.


CK

Turbo-Geist

And the myth continues to be spread...

See the dyno below from when I had the stock 1999 LS1 engine with ~84,000 miles on it.

There were some good things mentioned, but weak rod bolts on pre-01 vettes is a myth. A "tuner" once told me that they would fail at 550rwhp. I'm glad I didn't listen.

792/748

Turbo-Geist

As far as other mods go, I wouldn't do anything to the car besides bolting on the turbo kit with the 5871 turbos, proper size injectors, and a good tune. Adjust boost to where the car makes ~ 550rwhp and then drive it and see how you enjoy it. If you want more power increase manifold pressure and add more fuel.

As some mentioned, you will quickly find the 97 computer is limited from a tuning standpoint. The next weak point will be the factory auto transmission. If you are looking for a max of 650hp, I would only focus on the fuel system and transmission. Everything else can remain stock. I also swapped to better valve springs and pushrods on my stock motor and went with a new clutch and some driveline upgrades before going turbo. I also added an LS6 intake. The intake is optional for the power you are looking to make.

Here was the 1st dyno with the stock bottom end, stock cam, stock heads, etc:

0CK@UPPCOS

GMPP recommends replacing the rod bolts on any pre 01 Gen 3 for performance applications. After 01 they replaced the rod bolts across the whole line. Obviously that says something. It's cool that you were lucky enough to make that power without anything happening. Kudos to you. But no one can tell the metallurgic strength of the rod bolts that he has in there, and obviously there was a problem that was addressed. And there's really only one way to figure out if the rod bolts aren't strong enough to hold up to the task....

#2, you can't "ignore" the exhaust issue. It simply won't work. You can try to add as much boost as you want, but when you have a turbulent restriction that is causing back pressure, you have a problem. It's been tried many times, and we have many dyno records to back it up. And like I previously mentioned, with only w/g pressure it's worth ~80whp, which in terms of back pressure is HUGE!.

CK

SBCGENII

Dont spend any money on Gen 3 rods. They will bend way before the bolts break on a boosted motor.

SuperC

Thank you all for the Great Information. Really Good food for thought

I was focusing my mind on the top end of the motor thinking that was going to be the weak point of the system. I thought the LS1 bottom ends were pretty strong and I was hoping not to have to pull that apart yet.

Ok So let me try to sum this up then.

Most important factors are

1) Exhaust - Need 3 inch piping all the way back. Will high flow cats be an issue for flow? If so should I go with a test pipe setup so I can
2) Fuel System upgrades. Someone mentioned there are issues with 97 computers not allowing as much control. Will this be problematic when using E85? I was hoping to setup 2 maps, 1 for pump gas that is conservative and one with E85 that is for "race"
3) Transmission/diff and engine mounts. Someone mentioned those being issues. What are the failure points of the Auto Tranny? What gears do you recommend with boost?

blackmachdown

1. Yes they will hold you back I'm not sure the exact numbers but I'm sure CK has the numbers. I run test pipes and swap cats when it's emissions time. But I live in an emissions testing county. You might not even have to deal with emissions testing since you live close to the springs.

2. The stock pcms regardless do not allow two tunes to be uploaded at the same time. You would have to load whichever tune you wanted via a programmer or hptuners

3. Your mounts will be fine if they are in good condition.

Rkreigh

Injectors
What Size injectors should I use if I am shooting for 650 or so HP
Thinking 60lb or 80lb with an E-85 tune aggressive and a mild second tune on 91octane.

>>> e85 will need bigger injectors as well as fuel pump. e85 fuel quality can vary quite a bit. Keep in mind your fuel system needs to be around 40% bigger to provide a safety margin with e85

Intake flow
Will swapping the LS1 Intake manifold, TB and MAF make a difference?

>>> ls1 or ls6 manifolds work pretty good, I wouldn't mess with the TB

Heads
Are they worth swapping to 243s? What kind of gains can be had? Or should I leave them stock?

>>> target the compression for around 9 - 9.5, 10 or more if you are running e85. I'd sure consider flex fuel sensor ECM like a haltech if you want to run e85

CAM
Best cam that will no be too lumpy and drive like stock? I would like the car to be fun but idle well.

>> no way to tell you the "best cam" without knowing a bit more about your goals and how you intend to drive the car. A good old ls6 works OK with boost as does the ls9 and they are cheap. A cam optimized for your combo will provide more power, but the turbos do a good enough job there, I favor the driveability and throttle response over a few poinies. It's all in the combo and the tune.

SuperC

Thanks for the information. I actually live near fort collins but out in the middle of nowhere so I dont have emissions right now. But I would like to know if I moved, I could pop some cats in there.

SuperC

So maybe no E85. Would 91 octane with a meth kit be better?

Also for the cam. I prefer driveability over HP and I dont particularly want to swap heads yet so maybe LS6 would be best then.

Thanks for the info and reply

Turpid porpoise

91 + Meth is the next best thing to running E85 full time. You don't need the extra fuel volume with 91+meth and you can probably hit 650 whp without swapping cams.

Edit: 93 + Meth is really the next best but if you can only get 91 then it is what it is.

Turbo-Geist

I'm seeing this as your main purpose for the thread. The stock LS1 engine does not need any additional parts to make 650HP with 5871 turbos.

You need to address the fuel system and transmission and have the car correctly tuned.

Any other parts along the lines of intake swaps, head swaps, changing rod bolts, camshafts, etc., would be a waste of money for 650 HP.

You will also need to plan for a different set of rear tires. The stock run flats aren't going to cut it with the torque that a turbo produces.

0CK@UPPCOS

Go E85 and stop screwing around!

Think about it, you're already going bigger fuel injectors, so what's the difference in cost between 60lb/hr and 90lb/hr? Minimal. You're already at the point where you're going to need a fuel system (and ours will support E85). So why go through all the expense and trouble of adding on a Meth system if E85 is readily available? You could even add in the flex fuel sensor and still be less than the cost of the Meth setup......

CK

etekberg

Really? Can you explain?

0CK@UPPCOS

I was thinking "you're kidding right?", but then I caught the 1997 part.....

So you can't really add the flex fuel sensor, so you'll have to run E85 all the time, or swap actual tunes in the ECU when you change fuels.

Turpid porpoise

Do you have any info on how to get a non 97 C5 to run flex fuel? I thought Vengeance was the only group able to make it work and they aren't sharing info.

0CK@UPPCOS

I don't readily know that we've done it on any C5's. We've done it on plenty of early LS1 ECU's but they were mostly from trucks I believe and going into swaps, so there was no need to communicate with the BCMs.

CK