Car Guys, Assemble!

[eagl]

I am dropping a 3.73 in my Cobra backed with the tall 6 speed Tremec.  The Cobra top speed is not limited by horsepower, just the design itself.  It likes to lift the rear end at over 180MPH.

I take it a 911 whale tail is frowned upon...

One of the most spectacular crash videos I've ever seen was of a guy who insisted on building a '95ish Camaro (pointy nose version) out for 200+ mph.  If I recall the story correctly, he had the power but the rear end "stock" would lift at around 160-170, and with his aero mods including air dam and huge spoiler he'd still lose traction at around 190.  Out of desperation he put a few hundred pounds of sand in the trunkwell and gave it one last shot.  Right around 200 the car leapt about 20 ft in the air and flipped.  Spectacular video, can't find it on youtube since it was a pretty old vid and has been bumped by all the crazy one-mile Camaro wrecks in the last few years.  That's one good thing the updated 1998 Camaro and firebird styling did, was give the car another 20-30 mph before it started to lift.  Good thing 'cause the car with a stock LS1 would redline 5th gear in the 160s where the 1997 and earlier F-body would get really unstable.

[Rich46yo]

This was my first "legal" car. By legal I mean I bought a car at 15yo, a 1963 Buick Wild cat, but it wasnt really legal cause I didnt have a DL. So this was my first car, my High School car.


Dont have an original picture but same car. '66 'stang with a .289 8cyl and a custom vinyl Pony interior. I found it on a lot in '74 with 32,000 miles on it. It was, as we used to say, "Tits". After I ran it into a tree drag racing, splitting it in half, I bought a '66 Chev Caprice with a .396 big block, a big Holley, pipes, duals, from a local garage gearhead. It was painted in that gorgeous Chev candy apple red. It was, as we used to say, a "sleeper". Best of all I could fit the whole gang in it.

So many fast cars thru those years its hard to remember them all. Most of them big blocks. ALL of them from the '60s and '70s until I bought my first new car. An '85 Mustang GT. I love cars and trucks. Always have, always will.

[-ammo-]

Thanks Frenchy and Skuzzy.

Yep, I am sacrificing ludicrous high speed A-bahn fun for quicker acceleration.  My car has 3:73 gears now and the speed limiting factor with my car are the tires I installed.  They are the best street tire I have tried -  Mickey Thompson Street Comps.  I have 285/35-19s on the rear but they are Y rated and only good to 169 MPH. I can hit that easily with the 3:73s -  I have had the car faster than that with the last set of tires.  But these tires stick better than anything I have tried providing its above 60 degrees and the sun is shining (happens all the time in Germany, right?).  They handle great in the twisties too.  The truth is, I am not as keen as I was when I first souped up the car and was hitting 300 KPH.  I will still be able to squirt up to 170 but surely won't be able to maintain that speed for any length of time.  I normally drive the car on the A-Bahn anywhere from 100-120 MPH (traffic allowing) but I will certainly need to slow it down a bit on road trips.  I'll have to let the Audi, MB, and BMW family wagons pass me but that is OK.  I'll save the fuel and wear for the hot ones.  It will be a bit emasculating to let the German brand family trucksters -  to include VWs - pass me routinely

[-ammo-]

I think going from a 3.31:1 to 4.11:1 is not a good idea for Autobahn bashing.  A good compromise would be a 3.5x:1, if you could also attach a 6 speed to it.  That should effectively get you off the line better, through the mid range faster and still not compromise the top end.

I am dropping a 3.73 in my Cobra backed with the tall 6 speed Tremec.  The Cobra top speed is not limited by horsepower, just the design itself.  It likes to lift the rear end at over 180MPH.

Are you going with the Tremec Magnum XL? I have read nothing but good about that tranny.  Uhmm, it is a bit expensive too!  I understand it's based on a TR6060.. the same tranny in the Shelbys.

[Skuzzy]

I take it a 911 whale tail is frowned upon...

I want to preserve the integrity of the aesthetic of the car.  To that end, I will be doing some aerodynamic testing along Interstate 20 in West Texas.  It has a speed limit of 85MPH, which should be plenty to gather some data to see what I can do with the underside and flow over the top of the windshield.

Are you going with the Tremec Magnum XL? I have read nothing but good about that tranny.  Uhmm, it is a bit expensive too!  I understand it's based on a TR6060.. the same tranny in the Shelbys.

Yes, I am installing the Magnum.  Big transmission, but it has all the ills of the previous series corrected.

[-ammo-]

This was my first "legal" car. By legal I mean I bought a car at 15yo, a 1963 Buick Wild cat, but it wasnt really legal cause I didnt have a DL. So this was my first car, my High School car.
(Image removed from quote.)

Dont have an original picture but same car. '66 'stang with a .289 8cyl and a custom vinyl Pony interior. I found it on a lot in '74 with 32,000 miles on it. It was, as we used to say, "Tits". After I ran it into a tree drag racing, splitting it in half, I bought a '66 Chev Caprice with a .396 big block, a big Holley, pipes, duals, from a local garage gearhead. It was painted in that gorgeous Chev candy apple red. It was, as we used to say, a "sleeper". Best of all I could fit the whole gang in it.

So many fast cars thru those years its hard to remember them all. Most of them big blocks. ALL of them from the '60s and '70s until I bought my first new car. An '85 Mustang GT. I love cars and trucks. Always have, always will.

Nice ride Rich.  I don't have to tell you what that '66 Stang is worth now.

I really want a '67 fastback to restore.  I like a '68 too.  The '69s were nice but they started to get a bit bloated

[Skuzzy]

I had a 68 Mustang GT.  Loved that car.  I installed the sway bars from the GT350, which really improved the handling and stability.  Had a chance to buy a 66 GT for my first car, but Dad nixed it.

[eagl]

I finally sprung for a tune and CAI for my G8, put in a LS7 MAF with quicker temp response while I was tinkering with the intake.  Much nicer throttle response and better drivability from the tune.  I'm looking hard at headers/xpipe which would bump me from about 300 to 360ish rwhp for a total expenditure of under $3000, but there is a non-zero chance I might have to relocate to California and I don't want to have to keep the stock exhaust around forever on the off chance I might have to actually get the thing smogged someday.

Too much potential to just let it go, though...  The G8 has a known lifter weakness, and the current rage seems to be to drop a brand new crate chevy SS LS3 under the hood if the lifters fail and take out the motor outside of the powertrain warranty, instead of rebuilding it back to stock.  Some dealers will offer to drop that in for $10k total and give it a 2 year 35,000 mile warranty, compared to $5k-ish to rebuild a motor that trashes itself when the lifters fail on the freeway.  Not bad considering that when brand new, the G8 could be had for under $30k out the door...

[Skuzzy]

OEM roller lifters are a weak link for all makes.  That is usually the first thing that fails.

[-ammo-]

I finally sprung for a tune and CAI for my G8, put in a LS7 MAF with quicker temp response while I was tinkering with the intake.  Much nicer throttle response and better drivability from the tune.  I'm looking hard at headers/xpipe which would bump me from about 300 to 360ish rwhp for a total expenditure of under $3000, but there is a non-zero chance I might have to relocate to California and I don't want to have to keep the stock exhaust around forever on the off chance I might have to actually get the thing smogged someday.

Too much potential to just let it go, though...  The G8 has a known lifter weakness, and the current rage seems to be to drop a brand new crate chevy SS LS3 under the hood if the lifters fail and take out the motor outside of the powertrain warranty, instead of rebuilding it back to stock.  Some dealers will offer to drop that in for $10k total and give it a 2 year 35,000 mile warranty, compared to $5k-ish to rebuild a motor that trashes itself when the lifters fail on the freeway.  Not bad considering that when brand new, the G8 could be had for under $30k out the door...

I mentioned this in another thread.  I know of two G8 owners that installed a centrifugal SC on their G8s and their cars made insane power. This isn't a cheap modification but the bang for buck factor is definitely there.  Boost is where it's at if you want to make big power.  

[eagl]

I want to preserve the integrity of the aesthetic of the car.  To that end, I will be doing some aerodynamic testing along Interstate 20 in West Texas.  It has a speed limit of 85MPH, which should be plenty to gather some data to see what I can do with the underside and flow over the top of the windshield.

You might get some benefit from shaping the airflow coming up from under the rear.  Direct that up by keeping the airflow attached as it climbs the underside of the rear (hidden vortex generators under the rear bumper?) and you might be able to kill some of the lift that way.  Hard to measure, but you're going to have it wired up anyhow so a front and rear suspension ride height measurement gadget shouldn't be too hard to put together.  Even a little camera and an indexed card attached to the springs would work, if you could find a smooth enough road to not have to filter out too much noise to get an average ride height.  "easier" to do it in software but then you'd have to come up with a sensor and then filter the logged data.  But as long as the car is going to be wired up with your new vehicle controller anyhow, why not put in ride height sensors for testing your aero mods?

[eagl]

OEM roller lifters are a weak link for all makes.  That is usually the first thing that fails.

The 5 options are usually:
1.  DOD delete plus cam before it fails, which runs non-mechanics $1000 or more
2.  If the lifter tick is consistent enough, you can sometimes get the dealer to replace the lifters under warranty before they fail.
3.  Wait till it fails under warranty, and try to convince the dealer to replace it under warranty.
4.  Wait till it fails outside warranty, and rebuild the whole dang motor.
5.  Wait till it fails outside warranty, and spring for the chevy SS LS3 which is darn near a drop-in replacement, then spend a few extra pennies to bump it to 500+ rwhp.

I'm leaning towards option 5 since I think I'm out of warranty and occasionally I hear what sounds like those ball bearing pendulum toys you see on executive desks in the movies.  Like tapping 1 inch steel ball bearings against each other, tap tap tap pause tap pause pause tap tap tap pause tap pause pause...

[eagl]

I mentioned this in another thread.  I know of two G8 owners that installed a centrifugal SC on their G8s and their cars made insane power. This isn't a cheap modification but the bang for buck factor is definitely there.  Boost is where it's at if you want to make big power.  

Since I'm starting with the L76 there would be a lot of rebuild work done prior to that.  DOD and cam swap before even thinking of boost, for starters.  If I ever decide to go that big I'll probably sell the stock motor and start over with an LS3.

Or just sell the kids and buy a new corvette...

[Skuzzy]

You might get some benefit from shaping the airflow coming up from under the rear.  Direct that up by keeping the airflow attached as it climbs the underside of the rear (hidden vortex generators under the rear bumper?) and you might be able to kill some of the lift that way.  Hard to measure, but you're going to have it wired up anyhow so a front and rear suspension ride height measurement gadget shouldn't be too hard to put together.  Even a little camera and an indexed card attached to the springs would work, if you could find a smooth enough road to not have to filter out too much noise to get an average ride height.  "easier" to do it in software but then you'd have to come up with a sensor and then filter the logged data.  But as long as the car is going to be wired up with your new vehicle controller anyhow, why not put in ride height sensors for testing your aero mods?

I have six manometers to measure the pressure in various locations and will also tape the car for video to map the airflow over and around the body.  I'll make calculated drag coefficients from the runs in both directions.  Best I can do without a real wind tunnel.  Should be good enough.

One thought I had, was to open up a channel between the seats, from under the car, which exhausts on the rear deck.  I need to find a high pressure area under the car to open to the low pressure on the deck.

Yes, a rear diffuser might also be in order, if I can make it stealthy enough.

[eagl]

I have six manometers to measure the pressure in various locations and will also tape the car for video to map the airflow over and around the body.  I'll make calculated drag coefficients from the runs in both directions.  Best I can do without a real wind tunnel.  Should be good enough.

One thought I had, was to open up a channel between the seats, from under the car, which exhausts on the rear deck.  I need to find a high pressure area under the car to open to the low pressure on the deck.

Yes, a rear diffuser might also be in order, if I can make it stealthy enough.

I'm not 100% sure what most diffusers are intended to do, but if you want underbody airflow to direct upwards you need it to stick to the surface longer  That's one reason why those little trick vertical strips (can't remember what they're called) at the trailing edge of a spoiler wing work so darn well, because they ensure the airflow doesn't curve back down, sort of the opposite of what vortex generators would do.   A strip of tiny vortex generators (either angled edge-mounted plates extending out of the surface airflow boundary layer or low profile wedges that energize just the boundary layer) might do the trick better than a traditional diffuser.  You could measure the exit airflow direction with some bits of yarn taped to the back of the car, if you don't go all the way and measure actual downforce with either a pressure sensor or something to gauge ride height (spring compression as speed increases).