Katech_Zach

Good answer

Katech_Zach

Cool. I'm pumped. You're going to have a pro racecar when you're done.

Katech_Zach

Removing catalysts would be the biggest gain and still not near 530-540 or even the 550 he originally mentioned.

Katech_Zach

The LS7 is not under-rated. They make pretty much 505 SAE. GM does have a history of under-rating engines, but the new SAE standard and more responsible reporting policies are supposed to change that and the industry.

jvp

Boy, that's one super-efficient drive train then. *cough* *sputter* bullsh1t *cough*. With stock rear-wheel dynos of 440-460HP for these Z06s, it means the drive train is losing a mere 10-11% power?

As Bill Cosby once said, "Riiiiiiiiiiiiiiiiiiiiiiiight. What's an Ark?!"

While I don't question your knowledge of some of thing things that go on within GM, I find this claim to be complete nonsense. There's no way the drive train on these cars is SO efficient that it's losing 10-11% power. Not happening.

jas

WeaponsGradeTorque

You have got to be kidding? How can you even have the nerve to question Katech's answer on this? Katech works hand-in-hand in engine development with GM. They are responsible for helping out with the C6-R. They have some of the best engine dynos that are under severe environmental control to detect even a slight change in HP. Just ask Jim Hall about Katech's dyno's and how accurate they are. Why would GM say the the LS7 is SAE certified and not used the standard.

As far as RWHP numbers around here, they are mosly garbage. Katech even proved this recently with an LS7 cam test when they found one very reputable tuner to overrate the BHP gain by more than 35!

jvp

What does "a very reputable tuner's" overrating have anything to do with RWHP? I was there, the day my BONE STOCK Z06 was put in a Dynojet, with a mere 1000 miles on the odo. 454HP at the rear wheels. BONE STOCK (just for clarification: that means no engine tuning, no exhaust mods, no intake mods, NOTHING).

And I'll question anyone whose claims don't make sense. Simple fact: if a car is putting 454HP to the REAR WHEELS, and the engine is claimed to be putting out 505HP at the crank, that means the drive train is responsible for a 10.09% loss. And I believe that to be complete BS. Nobody's drive trains are that efficient.

I know very well who Katech is and what they've accomplished (they've been working with GM's racing long before the C6-R). But math is math. And numbers don't lie. You want to convince me, then whip out the numbers and show me.

jas

Verrückt

From Katech, that answer is as good as gold.

jvp

Some of you guys are amazing. The engineer in me says "Trust. But verify." I'd expect similar attitudes, but I guess not.

(Hint: Katech isn't God).

jas

Katech_Zach

So you are saying you trust and aftermarket speedshop's Dynojet inertia dyno that calculates horsepower based on the torque number at the rear wheels more than you trust a Schenck-Pegasus and Fraude water brake dyno with superflow electronics in a climate controlled room and industry standard SAE correction factors measured by a ISO 9001-certified tier 1 GM supplier? Numbers do lie, and here's a few more for you. We measured 420rwhp C6 Z06 on a Mustang dyno. That's 85hp drivetrain loss or 16.9%. Does that make more sense to you?

dgdoc

Did it ever occur to anyone that using a strict percentage of the engine's crank HP as the method of calculating drive-train loss is a pretty bad way to do this?

As an example, for this to be true, it would mean that the drive train loss on a C6Z would have to be about 25% more than a C6 for everything to be identical. Does anyone believe this is the case?

A different way to think of this is that drive train loss is probably pretty close to being a constant for the type of vehicle, transmission, differential, and axle/CV assembly. Yes, there is an increase in gear drag as RPM's go up and torque rises, but I don't think it is a constant. So, I believe that as HP goes up, the percentage to attribute to drive train loss will probably go down.

I've read that NASCAR folks have drive-train losses in the 5% area. Part of this is because these folks pay extreme attention to all the things that cause drag. However another part of this equation is certainly the fact that their motors are in the 700-800 HP range. If we simple used the 15% rule, that would mean that NASCAR vehicles would be losing 120 HP due to drive train losses. (Things would get pretty hot if that were the case).

Anyway, just something else to consider when engaging in crank vs. RWHP debates...

Katech_Zach

That's true. Drivetrain loss really ins't a fixed number or a percent, rather somewhere in between. Say you have a C6 Z06 loosing 85hp or 16.9% stock. Well say that we put twin turbos on it and it made 1000hp. It probably won't loose 169hp throught the drivetrain, but it probably will be more than 85hp.

jvp

Simple question: How many crate LS7s have you tested? What's your sample size?

jas

Katech_Zach

By my count in our log I see 77, but there could be much more than that.

JDRacing

Only 77? And you call that a significant sampling on which to base conclusions about an engine design's performance?

Seriously, you got my attention with that post (and it's not like I wasn't paying attention before). Would you be willing to provide some insight on the hi/low range of peak torque and HP numbers (if you're not otherwise under some confidentiality obligation)? Thanks in advance.

Mhart27

Thank you for putting into words what I have been wondering for a little while now. I never understood why it took more power to turn the same components when the power of the engine was increased. Assuming the drivetrain components have not been changed, how can you use a set percentage to calculate drivetrain losses for two different engine power outputs?

Katech: I am very interested to know why it would be, as you said "somewhere in between?" Not too technical an answer as I am not an engineer. Thanks.

AU N EGL

So some ppl are thinking that DECADES of experience with GM Engines, is still worth questioning?

Now what were those few WINNING engine building accomplishments?
http://www.katechengines.com/katech_...s_heritage.php

Katech_Zach

Sorry, I can't go into any more detail on GM development work.

JDRacing

Understood, and thank you for the response. I suspected as much, but just thought I'd ask.

Katech_Zach

Dgdog said it well when he said

Parasitics increase exponentially with speed. As you increase horsepower levels the percentage of which is lost through the drivetrain becomes less altough it is also not a fixed number. Here is an example: Compare that stock Z06 I stated earlier at 85hp/16.9% drivetrain loss. On our street attack Z06 at 608hp we measured 100hp/16.5% drivetrain loss. Horsepower loss goes up with power increase, percentage lost goes down.