[Stealth7]

My ZL1 is new, stock and may or may not stay completely stock. Great car!

Just food for thought and "ease of emissions-friendly mods", especially in CA:

1. ZL1 has 650hp/650trq crank power OEM.

2. ZR1 has 755hp/715trq crank power OEM (so, 105hp and 65trq).

3. Among other changes, the ZR1 adds a larger Supercharger, Larger Intercooling Capacity and More Sophisticated and Additional Fueling for the gains in #2. May also be Intake and CAM changes, not sure.

It is a bit interesting that GM made all of those changes to get those gains, but ZL1 owners and tuners are simply swapping pulleys and tuning for such gains. Makes me wonder about drivability, longevity, safety margins (too lean, etc.), warranty and other matters. If minor mods could have safely increased the power of the ZL1, it seems that GM would have done so.

Thoughts?

[BlaqWhole]

There is a lot more to it than that. Manufacturers take a lot into consideration when they put these engines together. It isn't as simple as they could have pullied it a bit more and got more HP. Nowhere near as simple as that. That would be kinda like saying you could throw a blower on a SS and have a ZL1 when we all know that the ZL1 is on a completely different level than the SS. Same way, the ZR1 is on a completely different level.

[Can'tHave2MuchHP]

Originally Posted by BlaqWhole

There is a lot more to it than that. Manufacturers take a lot into consideration when they put these engines together. It isn't as simple as they could have pullied it a bit more and got more HP. Nowhere near as simple as that. That would be kinda like saying you could throw a blower on a SS and have a ZL1 when we all know that the ZL1 is on a completely different level than the SS. Same way, the ZR1 is on a completely different level.

Agreed.

The amount of R&D and homework GM has to do when releasing an engine is absolutely crazy. I don't think anybody is held to a higher standard of performance engine reliability than GM, though they may not be the most reliable, they're the easiest ones complained about or at least one of the easiest. What I mean by that is, if a Ferrari has a problem at 20,000 miles, nobody bats an eye. But if an LT4 or LS9 or LS3 etc. doesn't make it to 50,000 miles or 100,000 miles (And there are MANY LS and LT engines over those marks) people start bitching. Same goes for Lamborghini, BMW M, Mercedes AMG, etc. none of them are held to the standards that the Big 3 and specifically GM are for performance engine reliability and sustainability. You could drive a LT4 or LT5 for 150,000+ miles just like any other modern daily driver. Try doing that with a McLaren or a Ferrari.

And yes, guaranteed if you take an LT4 that's pulleyed/tuned to make 755 HP and run it against a stock LT5, the LT4 it would fail in MANY tests that the LT5 would breeze through. Whether the problems start at 150,000 miles or 4000 RPM for 24 hours etc. etc. it obviously wasn't good enough for GM.

Besides that, you really think GM could get away by putting the same engine in both their halo ZR1 and mid range Z06?

[DangerZL1]

Most of the performance mods for the 1.7 blower require E85, meth injection, or race fuel. GM can't require any of these on a 50 state legal production car. The only solution for more power while maintaining reliability is adding the LT5, which unfortunately isn't going to happen.

[Badgerbimmer]

The engine also has port fuel injection and direct injection.

[Stealth7]

You hit on some of what I was saying.

My point is that given all that GM did for the ZR1 to get 105/65+, tweaking the ZL1 on 91 pump gas (not E85 or meth) in CA or other emissions control states is risky for the motor, warranty, smog, etc. I.e., no free lunch.

[bigmike32172]

But with all of the bolt-on claims made by numerous vendors you should easily be able to surpass the ZR1's 755hp with today's ZL1

[Markoz28]

I’m guessing the LT5 has a better fuel system than the LT4. Plus the super charger on the lt5 is bigger. Sure you can pulley the lt4 but you will need to upgrade the fuel for more than what a pulley can give. You can also add a bigger super charger to the lt4 but even that will be limited for fuel. The lt5 is just a step ahead. I’m guessing a pulley and tune will be crazy on the lt5. Then add E85 to the mix and it should be nuts

[Blackdevil77]

Is the cam different in the LT5?

[Oil Man]

Originally Posted by Markoz28

I’m guessing the LT5 has a better fuel system than the LT4. Plus the super charger on the lt5 is bigger. Sure you can pulley the lt4 but you will need to upgrade the fuel for more than what a pulley can give. You can also add a bigger super charger to the lt4 but even that will be limited for fuel. The lt5 is just a step ahead. I’m guessing a pulley and tune will be crazy on the lt5. Then add E85 to the mix and it should be nuts

I'm really hoping this translates to a lot of compatible, high quality fuel system components in the GM parts bin to address the limitations of the LT4 once you start adding power.

[devnull]

Originally Posted by Badgerbimmer

The engine also has port fuel injection and direct injection.

That’s what I’m talkin bout!

[toohighpsi]

The LT4 package was designed to meet the European pedestrian impact requirements in the Z06 which necessitated the smaller rotor diameter TVS1740 to maintain acceptable hood clearance. GM does not go to the dyno to see how much power they can get out of an application, that is determined by the vehicle design team and powertrain simply meets the requirement. There are no kudos for extra power, if the engine makes more than expected they will pulley/calibrate it down to the spec.

The 1740 on the LT4 is already tuning the maximum speed allowed by Eaton/GM. While it is possible to spin it a bit harder and make some additional power in the aftermarket, it's already at the end of it's compressor efficiency. This is what necessitated going to the larger SC. In the case of the LT5 the TVS 2300 would have been enough to easily hit the target that they delivered, but they clearly wanted to have a car (ZR1) that makes a statement and will continue to. The TVS 2650 is a serious piece and you can bet in no time there are going to be some crazy fast tuned ZR1s out there!

[Can'tHave2MuchHP]

Originally Posted by toohighpsi

The LT4 package was designed to meet the European pedestrian impact requirements in the Z06 which necessitated the smaller rotor diameter TVS1740 to maintain acceptable hood clearance. GM does not go to the dyno to see how much power they can get out of an application, that is determined by the vehicle design team and powertrain simply meets the requirement. There are no kudos for extra power, if the engine makes more than expected they will pulley/calibrate it down to the spec.

The 1740 on the LT4 is already tuning the maximum speed allowed by Eaton/GM. While it is possible to spin it a bit harder and make some additional power in the aftermarket, it's already at the end of it's compressor efficiency. This is what necessitated going to the larger SC. In the case of the LT5 the TVS 2300 would have been enough to easily hit the target that they delivered, but they clearly wanted to have a car (ZR1) that makes a statement and will continue to. The TVS 2650 is a serious piece and you can bet in no time there are going to be some crazy fast tuned ZR1s out there!

I do not think we will see any tuned ZR1s ever. Have you been keeping up with the ECU info on the Corvette Forum? So a small back story, EFI Live has been working on the L5P Duramax engine ECU for 2+ years and they just officially gave up. Saying it's impossible and even if they were to crack it, they'd have to charge a fortune for tuning. Now the ZR1's ECU is EVEN more complex and it needs TWO things cracked due to the double fuel setup. Plus, each ECU is VIN specific so EVERY car would require a super computer breaking the code for years. So every "tuned" ZR1 we see is going to have to be taken to a Tuner to sit for 2, 3, 4 or even more years just to be cracked.

That's if somebody doesn't leak out some sort of a short cut from the inside of GM which is entirely possible. But judging how the L5P flopped (And people said the same thing then and still do) I doubt it will happen.

I'll say this, the 1740 blower was a big mistake. How that slipped through the testing, we'll never know.

[bobby35ny]

Notice, different heavier crank on the LT5. If the LT4 could have made 675, 700+ RELIABLY they would have done it. And who knows if the rest of the powertrain could handle it.

Before I get flamed, YES I know guys are making 700+ with mods etc. but jury is out if it can last 100k miles.