SouthernSon

"General Motors faced tough challenge when searching for the proper transmission to pair with its all-new 625 horsepower supercharged LT4 engine in the 2015 Corvette Z06. The General wanted to match the lightning-fast shifts offered by Porsche’s PDK transmission, but no dual gearbox existed that met both of GM’s requirements — compact size and the ability to handle the LT4’s 635 lb.-ft. of torque.

The answer? Build one that could. The 8L90 eight-speed automatic transmission found in the new Z06 was developed entirely within GM. It’s a traditional automatic gearbox in its design, but GM says it shifts not only faster than any dual-clutch, but smoother as well."

I addition to the above excerpt, the transmission in the '19 ZR1 also had a few extras added including different algorithms.

BrunoTheMellow

The zr1 has the 2 extra radiators but it's still running hot air into all 3. All are behind charge air heat exchangers. With that being said. Even without the heat exchnager in the way. You still need the best main radiator you can find, the biggest aux horizontal radiator you can fit + a third radiator or oil cooler to keep the Z06 properly cool.

Timing is pulled above 194 coolant temp. Properly cool for full power is keeping coolant <194. Not 220,230. Just because the car doesn't hit limp mode doesn't mean it's not overheating.

d16dcoe45

Sir, I only used the term "LEAD GLOBULES" because another poster used PRECISELY that term--that is why I originally put quotations around it! I know what I have seen with my own eyes and my own experience in automotive engines. I don't understand why there is overwhelming fear and paranoia that leaded fuel will somehow "ruin" your precious engines. Doesn't happen. The cats and 02s, sure--they will be remdered useless eventually. The rest of the engine will not be hurt in any way, shape or form. I am hearing conjecture and internet claims but no ACTUAL first hand experience.

I am not the one that made the claim that LL100 is damaging, therefore the burden of proof does not lie with me, it lies with the person or persons that made such claims. I just think it's hilarious that much of the racing world uses HIGHLY leaded fuel and these deposits never seem to shorten the life of the engine in amy measurable way! Yet here we are on the ZR1 forum and the mystical LT5 is somehow "different" and lead will DESTROY IT! Again, no ACTUAL first hand experience. Just alot of conjecture, because people love to appear/sound smarter and more learned than they actually are.

d16dcoe45

Don't tell what I know or do not know. You don't know anything about me. And we are talking AUTOMOTIVE ENGINES. Instead of linking generic issues with airplane engines how about some personal FIRST HAND knowledge with auto engines? Go ahead. I'll
wait. No? I didn't think so. You are funny to me, trying to sound smarter than you actually are. You are predictable. Oh well.

SouthernSon

Bless your heart. I am sure things will get better.

range96

Realize race engines are rebuild frequently. Spark plugs used to be replaced after 12,000 miles in the old days with leaded gas. Exhaust valves were completely covered with lead residues in the leaded gas days. I think Hib misdirected the credit for the "lead globules" term.

Hib Halverson

NASCAR, MECS, Xfinity, Gander Mtn. truck series: unleaded E15 gasoline
IndyCar: Methanol
F1: unleaded fuel similar to "Euro 95" pump gasoline
FIA World Endurance (ie: 24hrs of Le Mans and etc) unleaded, 105-oct E20
FIA World Touring Cars: 93-oct E5
IMSA: 100-oct unleaded
Australian Supercar Series: unleaded E85

Those are the fuels used by some of what "d16dcoe45" terms "the racing world".

The only racing series I could find which could be called "major" which uses leaded fuel is NHRA drag racing allows a limited amount of NHRA-approved leaded racing gasolines supplied by either SUNOCO or VP to be used in Pro Stock, Pro Stock Motorcycle and Comp Eliminator.

It is likely that use of "HIGHLY leaded fuel" in motorsports is far less widespread than "d16dcoe45" may believe.

NASTYC7

Don't get these guys started on mixing 3 or 4 gallons of E85 with 91...… They will lose their mind and say the engine will be destroyed.... What they read and know are two different things..

NASTYC7

It's just not NHRA but all of drag racing from Pro to test and tune nights in which anyone uses VP's C-11 - C-16, not to mention off roaders, Sand drags, Boats and a ton of other high HP cars. I have a 850 hp Gen 1 car that runs on 102 octane for street use, 110 for the track. Leaded fuels are used much more than you think.

d16dcoe45

Boy you don't quit, do you? You don't even know who you are talking to. I mean, I am a NOBODY, but this is far from my first rodeo so please cut the pretentious language and attitude.

It is far less widespread than I would be believe? Are you being serious now? I almost think you are pulling my leg.

Do you have any idea why every sanctioning body uses unleaded fuel or ethanol based fuel nowadays, sunshine? (BTW I was waiting for you to bring up F1, Nascar and the others because you are very easy to figure out/predicatable) It is because of the EPA and politics, Lead is an ABSOLUTE NO NO in Europe--it is not found in solder, fishing lures, figurines, nothing! So naturally F1 and the FIA specs a quality unleaded. Same with Nascar! Nascar had a 12:1 compression limit, and didn't (or still don't) NEED super high octane fuel but WITHOUT A DOUBT EVERY TEAM WOULD RUN A LEADED RACING FUEL IF GIVEN A CHOICE!

I only took issue with you and Southern Son because you made blanket statements that leaded fuel is more/less the devil for your exotic and precious pushrod, Roots blown (yes SUPER HIGH-TECH&#128580LT5 miracle motors. And anyone who had different experience you inferred that they were 100% incorrect and your knowledge was superior to all. You weren't trying to teach, you were trying to "win". Seriously, get off your high-horse. Some people post to learn AND/OR teach, some others post to get the ego massage of appearing more learned than they actually are. You and Southern Son are the former.

Every weekend, 90% of Sportsman AND Professional drag racers fill their tanks with racing fuels containing ENORMOUS AMOUNTS OF TETRAETHYL LEAD! And their engines are as clean at teardown than the guys running pump gas! The fact is, lead is a VERy SMALL part (albeit an important one) of the overall makeup of fuel, and lead alone is not going to define that fuel or how clean it burns in the combustion chamber.

Oh, btw what is the name of your shop? The one you invited me to in your other post?

d16dcoe45

Haha! My guess is to these guys, drag racing and 1/2 mile racing is a joke. Not "real racing". Whatever that means. Funny thing about drag racers, they seem to know ALOT more about mechanics and technical stuff than HPDE guys. Not knocking anyone--I am sure there are plenty of road race/HPDE guys that know a TON more than I do, but it is just what I have noticed over time.

SouthernSon

I have had to replace more plugs in aircraft engines than I care to remember. Massive electrodes are less expensive than the fine wires but I hate having to run up the rpm and pull mixture several times at runup before takeoff to clean off residue.

Hib Halverson

I'm well aware that leaded fuel use abounds in a wide variety of non professional and, in some cases, non-competitive motorsports. My point is that in many parts of the racing (as in wheel-to-wheel competition at the professional level) unleaded gasoline is the fuel. A significant portion of "the racing world" does not used leaded gas. Perhaps some of this argument comes down to how we define "racing world".

Not to say that lots of horsepower can't be made with unleaded fuels. Until recently, NASCAR Cup engines were making 800-hp on non-restrictor plate tracks using unleaded 105-oct E15 gasoline. The top engine guy at TRD was quoted just last week as saying that the engines TRD currently builds for MECS racing's current engine package, would make 900-hp, if they ran without the airflow restrictions NASCAR puts on them.

That said, I get it that some of the larger displacement engines seen in high-performance/racing marine applications and in drag racing need higher octane because of how large their chamber volumes and so forth are making them more detonation sensitive. I also get it that to get much above 105-oct, leaded fuel is required.

But the fact remains...leaded gasoline in applications where 1) normal street driving is part of the equation as well as 2) teardown and rebuilds with far less frequency that you'd see with all-out racing engines can result in lead deposits on spark plugs, valve heads, chamber walls and piston tops.

You say you have an 850-hp Gen 1 car you run on the street on 102-oct leaded fuel....what do your spark plugs look like after 10,000 street miles?

JG853

Quick question - If a driver left the ZR1 in auto (D mode) and did not use the paddle shifters, do you think that these other PDK cars will be faster on a road course or drag strip?

NASTYC7

Well, I can't say I drive it as a daily, so 10,000 street miles wouldn't even be a option for me in an untouched scenario. I run a magneto so my spark is very hot and I can say I never seen any lead deposits even scoping I see nothing in the cylinders. I have 14:1 compression, the leaded fuel is to help stop early detonation. I am in the process of changing over to E85.

But I am sure you are old enough to remember when that's all we had was leaded fuel. Even back then I never saw lead build up on any teardowns, plug changes or anything. It was basically just blow by build up due to tolerances back then. Leaded fuel is not a "Engine" problem it's an "environmental" problem and I know VP is working to make more fuels without lead, not because of deposits. I believe they have C-20 now unleaded that handles 30 PSi of boost or up to 12:1 compression.

Hib Halverson

Now, back to our regularly-scheduled A8 thread...

Occasionally, I assist an oil blender in testing new products in a performance street duty cycle.

In the last half of 2018, we briefly tested an aftermarket Dexron 6, mPAO-based, full-synthetic ATF in an 8L45 eight-speed automatic. The 8L45 and the 8L90 much the same inside with the main difference between the two being the L45 has rotating parts which are smaller in diameter that those in the L90, allowing the transmission case to be smaller and the overall weight of the transmission to be lower, however, the two versions use the same type of torque converter clutches and have the same clutch materials inside the transmission. 8L45s are common in V6-powered light trucks and V6-powered, rear drive passenger cars such as the Camaro and the Cadillac ATS and CTS.

Just before we began this test, I had one of my sources in the service world advise against it because he had heard anecdotal information about dealers who had mistakenly filled eight-speeds with Dexron 6 rather Dexron HP and, subsequently, had those transmissions fail. Feeling the information was too anecdotal, I discounted that intel and proceeded with the test.

I had this transmission flushed and refilled with this aftermarket Dexron 6 fluid. In a 2655 mile test, I could perceive no difference in fluid temperatures or transmission performance. At the 2655 mile mark and several months after the change to the test fluid, the manufacturer of the aftermarket Dexron 6 contacted me and said to end the test because some lab work they had been doing at the same time with the OE fluids indicated that, while the two fluids, Dexron 6 and Dexron HP, were quite similar in base stock and viscosity, their additive packages were vastly different. The feeling was that because of this vast difference in additive packages, use of a Dex 6 spec. fluid in a transmission designed for Dex HP could eventually damage the transmission.

Further research, which included the several GM service bulletins in re: fluid for 8L45s and 8L90, indicates that the factory fill and ACDelco replacement fluids had had their formulations changed two or three times since the transmission was introduced for the 2015 model year. Additionally, at the time we decided to end our test, GM was telling its dealers not to use the ACDelco fluid at all and use only Mobil 1 "Synthetic LV ATF HP" (low-viscosity automatic transmission fluid high-performance) in both 8L45s and 8L90s. We ended the test of the Dex 6 fluid then flushed and refilled the trans with M1 Synthetic LV ATF HP.

The lesson in all this is: don't run any fluid in an eight-speed but either Mobil 1 Synthetic LV ATF HP or other ATF which meets the current Dexron HP specification. I will add that there are very few fluids other than the Mobil 1 which meets that spec.

SouthernSon

I like changing my own fluids so I appreciate the info on the transmission fluid, Hib.

Here is another little ditty I found on the other topic of interest:

https://www.shell.com/business-custo...-30071600.html

Hib Halverson

With the 8L90, you can only "change" the fluid that's in the pan. Even then, with a Corvette and the trans having no dip stick or fill tube, it's a f@#king bitch of a job to do. Fluid level has to be checked with the trans fluid at 95-115° and the engine running which is impossible to accomplish without burning your arms, so you need some Kevlar gloves and wrist protectors. If you have to add fluid, you need a pump of some sort with a hose long enough to snake around the exhaust and then go up and then bend 180° down into the fill opening which is sealed with a rubber plug which you first must pop out.

I have not actually done that. but I've had the car up in the air looking at how I'd do it.

That coupled with my experiences checking/adding fluid to both an ATS-V with the 8L90 and a Chevy Colorado with an 8L45, has me knowing the above description is pretty close to reality.

To flush and replace all the fluid, you need special equipment dealers and some trans shops have.

SouthernSon

Okay, you talked me out of that one.

UnhandledException

As someone who has tried various transmissions back to back extensively, I can tell you the automatic in this car (as by now widely known) is pretty slow in manual mode (I honestly dont understand why anyone would not want to use manual shift mode at least sometimes). Even BMW’s ZF8 transmission that are found in “non-M” cars like 550 or 340 are substantially faster than the transmission in corvette in manual mode. The DCT in the M cars is in a different league and I’m sorry to say this PDK (let alone PDK-S in GT3/RS) is worlds apart.