I recently purchased an 07 a6 (nonz51) and have been researching as to what modifications I will choose to do to improve the handling.

As far as "sustained high g forces" go, what is the max that one could recommend with the a6? I'm asking because this will determine what spec of tires I will run on the car as well as the setup of the suspension.

Thanks

 

your setup determines how many g's you can pull. crappy tires and bad (base c6 suspension) you wont make any g's you just slide outta control. i think nitto was claiming almost 1.5g on a stock evo x with the nt05

 

Thats correct but Im interested in how many Gs the transmission can handle so I can choose a suspension and tire setup (I already have several in mind).

ie I wouldnt pick hoosier A6's and and a racing setup because I know the drivetrain cant survive the extended fluid starvation, but I might pick a max performance road tire or less aggressive dot r tire and midrange set of sways/springs/shocks.

Im aiming at 1.1- 1.2 Gs, but I just want to be sure the a6 will be able to handle this.

Thanks

 

i dont think there are any corners long enough to hold high g loads long enough to starve a trans for fluid. let alone the fact the trans fluid fills the bottom of the case along with pan. id be worried about engine oil starvation first.

 

The reason why gm engineers never put dry sumps in a6 cars was because the a6 cant hold up to high lateral g forces for extend periods of time. The a6 is a limiting factor and I just want to know how much so I can plan the car out accordingly.

I don't think they mentioned how much the a6 could reliably hold up to, but this is the information I am looking for.

Thanks!

 

That's exactly right and also exactly all we've been told. I haven't seen any specifics. All I can offer is that 1) Spring Mountain Corvette Driving School has 2 A6 GS's and don't have problems but obviously they don't have a huge track with sustained side loads, so 2) if you're just doing regular type road racing with relatively short side loads you will likely be okay, especially with the limited capability of a street car.

Also, did you ask the guys in the Roadracing Forum for any insight? Best of luck and have fun.

 

Is the bolded portion an assumption on your part or is it a statement of fact??? If it's a fact, please provide the name of the GM engineer(s) who made this statement AND a link to the same.

I'm going to guess it's an assumption on your part because there is no limit to the amount of lateral g-forces the 6L80 can withstand. Transmission fluid temperature is the limiting factor when tracking an A6 car and they won't run very many laps on a hot day at the track before the fluid temps max out, that is the reason GM didn't do the dry-sump on A6 cars. They're not meant to be on the track for long periods of time in the heat because they don't have the cooling capacity from the factory. Adding a well designed/installed aftermarket transmission oil cooler will solve that problem but if all you're doing is autocrossing, you don't even need that. I'm assuming you're doing autocrosses since you mentioned Hoosier A6 tires and not the R6.

Get a set of DRM custom valved Bilstein shocks and a set of Z06 springs/stabilizer bars to go with a set of Z06 size Hoosiers A6 tires along with an alignment for track use and you'll have more cornering power than you'll know what to do with. (If you have to use your stock size tires, use the Z51 springs/bars.) DRM just did a group buy on Bilstein shocks...you might be able to pick up a set somebody on the list backed out of. You might get away with less than $1000 for shocks/springs/bars if you can pick up a set of used Z06 springs/bars for a good price.

 

Yes, it was stated by Tadge Juechter at Sebring. Here's Joe G's synopsis and the 42 minute video if you want to verify.

http://forums.corvetteforum.com/1577130727-post1.html

 

I watched the video and the problem isn't the max amount of lateral g's being generated, it's the transmission oil temperature. Watch the video again and pay particular attention when it gets to 30:30 where he states:

"Like I said, the condition of the oil, based on our testing, the weak link is always the transmission. You'll get a message on the DIC that says 'trans temp hot' before you run into any issues with engine oil."

That is the reason the dry sump wasn't installed on automatics...as he said, "When the limiting factor is the transmission, there's no sense adding all the content to save the engine. I mean the dry sump is to save the engine and improve the lube system of the engine...that's not the weak link, so you don't put it in."

He did say "the automatic wasn't designed for the same lateral load capabilities as the manual", but nowhere did he say it wasn't designed for the same max lateral load. "Capabilities" can mean many things...in this case, it means the A6 transmission doesn't have the capability to stay on the track at 10/10ths (max lateral g's) without overheating.

I did see where el es tu said in his third post "the a6 cant hold up to high lateral g forces for extended periods of time" (bold my emphasis), but it really has nothing to do with the g-forces which is what his first post is stating. The 6L80 isn't going to fly apart if he somehow manages to pull 2 g's in a corner...that isn't what Tadge was talking about. Joe G's synopsis is correct but misleading...hopefully people watched the video and understood it was about the transmission fluid overheating and not a max lateral g limitation.

The fact that Spring Mountain uses the two GS A6 cars in Las Vegas where summer temps are brutal says something. Their track may not be huge but it is far from small at 2.2/2.4 miles and 10/12 turns plus they put the same Michelin PS2 ZP tires on the GS as the Z06 and ZR1 use. My guess is they install a transmission oil cooler too...I'll give them a call tomorrow and ask. I need to see about setting up a driving school my daughter got with her 2011 GS anyway.

 

We may be discussing semantics. I don't think anyone has said or believes the A6 will come apart due to sustained high G-loads. What is understood is that the trans oil will climb inside the oil pan same as the engine oil and subsequently uncover the trans oil pickup. That obviously results in slipping and heat. Maybe they need to design a dry sump system for the A6.

All the best to your daughter. She should have a great time at Spring Mountain.

 

Will you be running with NCCC or SCCA? What class? The rulebook will determine your setup.

 

I did a several low cost upgrades and I wish I had saved my money and just bought the Pfadt kit and moved on. All the parts are made to work together and in the end, it would have cost me less money than my trial and error method.

 

Is the bolded part "understood" or something you just made up. Link us up to any discussion proving your assertion. Tadge never mentioned anything about the transmission oil filter becoming uncovered besides the fact that it will never happen (unless you're really low on transmission fluid)...have you ever had the pan off of a 6L80? It's nothing like the inside of an engine where there's plenty of room for the oil to go up...the valve body makes a pretty good "dam" to keep transmission fluid in the pan. This is not a matter of semantics, there are too many A6s being successfully tracked with only the addition of a good aftermarket cooler. When heat is generated from the clutches slipping, the transmission fluid and friction disc get burned long before you get the "trans fluid temp high" message on the DIC. Plenty of people have gotten the high temp message with no burnt friction disc or fluid meaning the heat isn't coming from clutches slipping as you said.

The funny thing about this is the dry sump LS3 will starve the scavenge pump pickup in a left turn over 1g as the oil climbs the oil pan away from the single pickup mounted to the left of center in the oil pan. The double reservoirs hold a sufficient amount of oil to "cover" the momentary loss of oil from the scavenge pump that's replenishing the tanks. Unfortunately, the '06-'08 Z06s only have one reservoir and plenty of LS7s have bit the dust pulling over 1g with R-compound tires and that was very well documented by a Corvette Forum member...after 4 seconds over 1g, oil pressure drops to zero. The Viper has a swinging pickup which is the proper way to do it if you're going to use a single stage scavenge system...real racing dry-sumps have at least a three stage pump (one pressure pump and two scavenge pumps) with many having more than three stages.

With proper cooling, the 6L80 will have no problem surviving extended track sessions. I still plan on calling Spring Mountain tomorrow to see what they did to their two A6 GS's. I don't think my daughter knows they have A6 cars yet.

 

Thanks for the replies.

Im either doing stock sizes or going with 265 front and 305 rear (if I end up needing new wheels to clear bigger brakes)

Now the hard part is tire choice: pilot super sport, pilot sport cup, or toyo r888...

 

I spoke to Spring Mountain today and they said the two A6 GSs have a stock drivetrain...no transmission oil coolers. They run 20-30 minute sessions and have no problems with overheating. I doubt the sessions are being run at 10/10ths for the whole session since the purpose of the school is to teach but this is proof the A6 can handle the lateral g's even if it isn't for extended periods. Like I said, add a good cooler and don't worry about running for extended periods.

 

I drive the car hard for appropriately 30 min to an hour at a time with some small cool down breaks in between, so this is very good news.

Thanks for looking that up.