Schantin

iTrader: (6)

Hi. I'm stationed in Germany and have had my Camaro here for about 2 weeks. Current setup includes H/C, 243 heads w/ Patriot Duals + hardened pushrods, 9" rear end, UMI suspension parts, etc.

I currently have 4.11's in the center section, which is GREAT for acceleration, but for the German Autobahn those gears certainly wind the engine up higher than I'm used to. At 95mph I'm sitting at 3,050RPMs and at 155 it is in the 4400RPM range.

I'm curious if running at 4000+RPM's for extended periods of time will torch the engine in the near future or if I just need to get used to hearing the LSI in the upper RPM band

I have thought of swapping the 4.11's to some 3.23's or even 3.08's.....

$0.02 from the autocross crowd appreciated. Thanks.

Big Bu Bu

iTrader: (4)

I'm not an expert on the subject, but from most of the things I've read, things like aggressive cam lobe profiles, lift, and in some cases the spring configuration are the factors that determine stress on the valve train. So I guess the short answer is if your valve train is robust enough, then the high rpms are not a problem. I would imagine that running at speed over there alot different then the US. 4.11 does sound high for a top end car. My CTS V has 3:73 gears and in 5th at 163mph it's at the redline at 6300rpms. 4400rpms sounds low for 155mph to me.

98_1LE

iTrader: (17)

Sixth gear won't live long at high speeds. It will overheat.

High rpm's will wear the motor, but as long as you keep it cool it will last a good while.

Averaging 140mph over 59 miles, my T/A got under 7 mpg.

Schantin

iTrader: (6)

Thanks for the reply. Concerning RPM's.... the 4400 was approximate. I was looking at the road more than the Tach at that speed Appreciate the engine info.


That's why I like this forum..... never even thought of keeping the tranny cool at that speed. Which begs the Q.... does anyone make a tranny cooler for a T56?

Concerning fuel economy. Totally feel you. I burned through an 1/8 tank on one high-speed run. It's not an everyday thing for me to blast that fast (even with no speed limits). I've been averaging around 95-105 in my travels.

98_1LE

iTrader: (17)

Yes, they do make coolers, however you still don't want to use sixth gear for extended high speed driving. Change gears in the rear diff.

The problem is with a .5:1 overdrive, the shaft is spinning at twice driveshaft rpm. At high driveshaft rpm and load, the bearings are simply undersized. You might be able to swap in a higher numerically fifth/sixth gear set, but I think there are restrictions on that also.

Above 170 aero starts becoming a problem, with getting air from under the hood becoming a challenge. What kind of safety equipment do you have?

A couple interesting things:
With stock 3.42 gears, the ac compressor works up to about 130mph. I think it shuts off at a specific rpm.
The cruise control worked at 138 mph with 3.42 gears, but not at 165 mph with 3.23's. Not sure why. It works at lower speeds.
I have driven 130 with the ac and cruise control on.

blackrat

What kind of provisions do the autobahn burners use to be able to maintain those speeds? Mercedes are autos so they are out of the picture but manual BMWs must have some features to help keep driveline temps manageable.

I remember reading an issue of GMHTP with some guy who built up an LS1 T/A for the Silver State run. One of the things it focused on was how he put a lot of time into keeping the diff cool. I guess that was a big problem for sustained high speeds. Here's the link:

http://www.gmhightechperformance.com...ure/index.html

Interestingly it mentions he kept the T56 stock, but also has the stock 3.42s so he can keep it in 5th. I've heard of the problem of pushing 6th gear as well.

Schantin

iTrader: (6)

98 1LE and Blackrat.....

Good info and interesting points. Thanks for your responses Yep, I'm in "seldom charted" territory here. I did not know about the bearings for 6th gear being a weak link. With the current 4.11's I'd max at about 135MPH (approx) in 5th gear. That would get me skunked by even my 91 Eurospec 5-series sedan

Blackrat.... the German cars are limited to 155mph. That's why my sights are set on the 165-170 sustained speed. It's just enough faster to prove a point not to mess with the American sports car. My Euro BMW does not have oil coolers for the diff or trans.... and it's a 24-valve (high output) M50 version. It does have some retardedly large brakes + independent rear-end though......

For the rear on the Camaro.... I do have a Moser 9". It holds a butt-ton of fluid, which does help in cooling. I haven't thought about adding a cooler to the rear. I had thought of tapping the bottom of the tranny on the T56 and adding a Mocal pump to an external cooler (like what an STS-Turbo system would use for oil-return to the engine). That's pure custom though, so haven't gotten too far on that.

As for speed, YES, AIR IS A VERY SERIOUS FRIGGIN PROBLEM AT 170. The car began to feel very light at that speed (or a better way to put it is I got very scared), so I let off the gas and allowed her to coast back into the 140MPH range. The Autobahn is extremely smooth, and like Slickrock for a 4x4, makes stock shocks/springs perform like a hero. The difference between 165-170 in my car was dramatic. Full control to "oh crap!!" I have no front crash bar or foam in the nose (due to the previous FMIC installed when the car was turbo'd). That might be actually helping my cause by disrupting airflow. I was told by others on this forum that Koni adjustables would help cure that problem.

Safety equipment is what you'd expect for a drag car. Driveshaft safety loop, race seats + harnesses. (No cage yet). I've been careful in testing her limits too..... believe it or not.

Thanks for the input, and if anyone has ever installed a cooler on their T56, please chime in. I know there are some peeps here who have been to Germany and cruise in the upper 100's range. As for gears.... I'm slated for a Mid-East military tour that will be paying for a lower-geared center section + some 6-piston Baer Brakes.