2010 Grand Sport Dyno Day - Surprise!

STL Mark

STL Mark

Member #001
Honorary Member
Location
Pacific, MO
First Name
Mark
Last Name
Earls
So, I've been posting this tale on the Corvette Forum, and I thought I should probably share it here as well.

So, today was Dyno Day. I bought my 2010 Grand Sport M6 Vert. 6 months ago from a dealer, used with 66K miles (now 67K miles). It runs great, excellent paint and interior, and appears BONE stock even down to the RunFlats. As soon as I pull it in, the tech say somebody's done some work to this car - It's been lowered. We compared it to a ZR1 in the shop and it looks about an inch and half lower. WOW! Well, okay fine.

They do the 3 pulls, no adjustments...and it made 427 RWHP. So, I guess it has a tune right? Thrilled no matter what.

It was an excellent shop, and I'll be going back now with confidence (and a baseline) to make my mods (headers, exhaust, CAI, tune).

What an awesome day. (end post)

SO - this is almost 100 HP over stock. Almost certainly the car has a computer tune. But, you can't pull that much gain with zero bolt-ons. On dyno day the shop did not run A/F diagnosis, or access the ECU. They can when I bring it back in. So, we'll see what kind of tune may be in there. One poster on CF suggested a mild cam. I don't know. The idle sounds stock. Maybe ported heads or intake or both? It's a mystery.

Furthermore, on a related issue - I bought an extended powertrain warranty (35,000 miles) with the car. I believe that the warranty is probably now in essence - void. I called the dealer salesperson (my son-in-law). He said they'll cover it. But, I have my doubts. I doubt they replace a hot-rodded LS3 with a new hot-rodded LS3 if it has a failure. If they cover it at all (which I doubt) it will be a stock LS3 - or stock parts.

So, I'm thrilled, and at the same time at bit concerned. It's a big mystery. I'm having the dealer contact the original owner, but not holding my breath.

How about deductive reasoning... QUESTION - does anybody here have an idea how to get an extra 100HP with zero bolt-ons on an LS3?

M
 
A few thoughts from around the interwebs:
Super Chevy
Another Super Chevy
Old Corvette Forum post

You said you hadn't done much poking around, so, I would think intake/heads have been modified or upgraded. Everything from porting to new springs on the valves and many other things you can't see from just looking under the hood. The discussion with the previous owner should help. As for your warranty, don't sweat that. Unless you tell them, I bet they won't notice or mention it either. Plus, you have a good car, don't think the worst that it will be in the shop during your ownership.

By the way, what does M6 Vert mean?
 
Purple Venom said:
By the way, what does M6 Vert mean?
Click to expand...

Manual 6-Speed, Convertible.

As for your ideas, I'm thinking the path of least resistance - mild cam, ported heads, computer tune. Supposedly, a factory cam has one bolt, an aftermarket has 3 bolts. But that sounds odd to me.
 
Mark I think you are correct. Cam with low duration but large lift combined with well done stock heads and a good tune could get there. Not sure about the LS3, but my stock LS1 cam was the same bolt wise as the Comp cam I installed.
 
Excellent info about the cam bolts. I really have no idea.
Thanks for the info.

The cam/head/tune seems to be the thing.
I just don't know.

We'll explore the tune on the next visit.
As for the cam - it sounds like stock idle, so it's a bit stealthy.

LS3 makes 420 at the crank. This car makes 427 at the wheels.

It's a unicorn !
 
Excellent info about the cam bolts. I really have no idea.
Thanks for the info.

The cam/head/tune seems to be the thing.
I just don't know.

We'll explore the tune on the next visit.
As for the cam - it sounds like stock idle, so it's a bit stealthy.

LS3 makes 420 at the crank. This car makes 427 at the wheels.

It's a unicorn !
 
Have you unbolted the coil covers and taken a close look at the engine? Might be a Big Block Ford in disguise :cool:

Or it could be a difference in the way the HP is read by the dyno's. There are varying methods - what Franjo found and what Detroit is reporting may be based on two different test criteria :confused:
 
You must log in or register to reply here.
Back
Top