dllhg

Well I finally had car dynod. Have about 30 hard track days on this setup. Still running strong 👍. Mid and top end majorly improved over downpipe and tune setup. Went with more
conservative tune since I do heavy track work. Was told it would be around 650 whp with the 100 octane. 700 give or take with more aggressive tune. I don’t know how anyone is getting 100 whp gains on stock turbos 🤷‍♂️ car is night and day faster than downpipe with 100 octane tune. Here is graph. 677 whp. About 100 over stock.

gesundheit

Do you have the before and after? Otherwise, it’s very difficult to truly see the improvements.
also what boost level are you at to achieve this and is the tune for 100 octane?

Higgs Boson

They make 510 - 530 at the wheels depending on who's fluffing the dyno so your car made about 150 more than stock at the wheels on 100 octane. IAT's are probably a good bit lower than a maxed out stock turbo tune as well which means more consistent power for longer rather than just putting up a dyno number that doesn't hang out at the track.

gesundheit

Every dyno is different. I’ve seen my car make 80hp difference just based on the dyno I was using. The 900s should make power until cutoff.

G. P

Just one correction to your statement of "100 over stock"

GTR's Stock HP is rated at 575 Crank HP. Your Dyno shows 677 whp. So wiith 12% drivetrain loss on the GTR, this 677 whp is actually 769 Crank HP, or 192 over stock. Nice gain. Enjoy it.

Higgs Boson

I think he's referring to Renntech saying the cars are underrated (even though they aren't).

Wasserott

Renntech appears pretty transparent, can you back up what you state?

Wasserott

Dave - nice job and thanks for posting…that is a great result.

Higgs Boson

Every turbo car dynos with better than expected results compared to what the manufacturer rates them at, why is this? BMW, Honda, MB, doesn't matter, they are all "underrated."

Aside from trying to back calculate engine power from wheel power on different dynos in different conditions (the factory rates the engine with repeatable results in a controlled and scientific environment very unlike the typical tuning shop chassis dyno), the tests are performed differently as well.

The factory rates the engine without acceleration meaning they hold the RPM at given points and take a measurement and then move to the next steady point and form a graph based on this.
The chassis dyno (or other engine dyno methods) use a sweeping accelerating measurement that always causes higher readings.
Its apples to oranges. Only problem is, it's measuring apples on the tree against oranges in the grocery store.

The GTR makes 577 engine HP, that is a certified repeatable number no matter what the chassis dyno says it makes at the wheels. I am not saying Renntech is doing anything wrong but I am saying we need to understand why. It's for a good cause, it is to compare their advertised power gains to a real baseline in their shop. They want to use a 12% drivetrain loss, but 577 * .88 is 507rwhp. Due to differences in testing they dyno a stock GTR at 535rwhp, but no would would believe the car has 7% drivetrain loss so instead they just call it "underrated" because of course it doesn't have 7% loss, the testing method is just different (a lot different).

So really they are doing us a solid and not claiming those gains for themselves, instead trying to be transparent by showing us a real gain from an actual baseline. That's a good thing.

Wasserott

Your response sounds logical and reasoned. Thanks for that contribution. I think that Dave’s results are a good reflection of the mods and performance he has seen and shared. Not a perfect prediction but close to what you might expect.

Wasserott

I would like to know if you can run these turbos with the stock cats in place without too much heat issues.

user33

Interestingly, in this video by GAD Tuning he states that AMGs don't make more power than they're rated at, the implication being "if the dyno works properly":

Higgs Boson

Exactly, back in the old days we just called the dyno generous or ambitious, etc. We didn't call the car underrated.

At least Renntech isn't trying to take credit for an extra 20rwhp.

G. P

For lack of baseline, I default my numbers to the GTR's spec HP. I agree that whenever you do a dyno, you have to run a stock tune and then the tuned map, so you can see the gain. Otherwise, numbers can be all over.

dllhg

Two stock C7 Z06 were there. Both put down 563-565 whp. So it’s def not a high reading dyno. I had car in dyno mode and pulls were in 4th gear.

dllhg

Super happy with the car. Dyno was just a cars and coffee event with some friends. Was fun. What I can say is the car is night and day better through the curve vs catless downpipes and 100 octane tune. Very reliable as well. Over 30 hard track days mostly Laguna. 👍

BlownV8

You probably understand this but for those not familiar with dynos. The results should not be if you are using the same manufacturer of dyno with a weather station like Dynojet. The results should be the same/very close regardless of where the dyno is located. Yes, you will see differences with different measurement technology: inertia, water brake, electric, or hydraulic.

gesundheit

With my Pure 900 setup and a custom tune I achieved +250hp at the wheels and +260tq at the wheels compared to my stock GTR. This represents a 50% increase in rwhp and a 55% increase in rwtq. Tuned for race gas.
This was the highest, yet still at a safe limit, of the stock fuel pumps. I thought about upgrading the pumps, but traction is already an issue :-).

dllhg

I don’t know about 250 gain. I have heard 800 possible with fuel upgrades. My understanding is 700-725 was max safe power stock fuel system. Stock is around 550-560 whp. Mine is 677 with 100 octane on safe tune for heavy track use.

gesundheit

I have many, many dyno runs on my car using 3 diff types of dynos and the gains were consistent on each of them. My tune is not conservative, like you mentioned yours was tuned for, and mine is not intended for the track. Originally, I had a more conservative tune, but then tried more aggressive tunes to get closer to the stock fuel system limits with more boost and timing. I was able to get another 70+hp to the wheels between my conservative tune and the aggressive tune. Also, 100 octane is the lowest level octane of ‘race fuel’ gas. There are higher octane levels that can allow more timing and boost without knock. I’ve also had the opportunity to try 3 different types of dynos with stock figures ranging from 473 to 502 at the wheels. These are real ‘at the wheel’ numbers, not manipulated/corrected ones (for example dynojet offers SAE STD EEC DNI JIS UNC…you should be using a standard SAE), watch out for smoothing, and, for consistency, all 3 diff dynos were done with the proper 1:1 gear ratio (5th gear). It’s one of the reasons I’m not a fan of dynojet, which most folks flock too for ‘bragging rights’ numbers and the ability to manipulate.
To say a car makes x hp at the wheels and will max at y hp based on fuel system, tranny, etc may be misleading as there can be huge differences between dynos, tuning maps, fuel type, etc. For reference, it’s not unusual to see a 5-15% difference based on the dyno type you are using, which is why getting a baseline is so important if you’re truly trying to see the increase on the same car.