ItalianStallion

Give me one more year and I will be your friend's biggest customer lol

MRonan

Very interested, Wouldn't mind to listen to what your friend has to say. Please PM me his number. Thanks

MR

BlownV8

1.35 bar = 19.845 PSI

According to the tech that ran dbassons55 boost pressure neither did you. J/K

Maybe you should take a bit of advice from yourself.

By asking a question, I was reveiling that I did not know the PSI on the 65 engine. It painfully obvious that the engine is not very efficient at flowing air when you have to run 21.5 PSI, according to you, to make a little over 600 HP from a 6.0L engine. Heck, your Supra was making way more power on similar boost levels from an engine with half the displacement. Granted the Supra does spin faster and HP is dependent on RPM. Not to mention, the 65 has an automatic tranny but the difference isn't that great in the grand scheme of things - maybe 35 rwhp at that level.


This is an excellent tool for determing hp that an engine will make on boost. It's for supercharged engines that sap hp more than turbocharged engines but I think it may help explain:
http://superchargersonline.com/hp_ca...r.asp?submit=1

Take 200 RWHP starting HP and add 20 PSI and a 3 core intercooler. Our air to water intercoolers are very effective so I'm giving Mercedes a reasonable doubt that theirs is as effective as a 3 core intercooler.

You know what that gives you? 510.57 RWHP. That's right at what these engines make. If you back into the RWHP the 65 engine makes, it's right at 200 RWHP without boost. That pretty much sucks for a 6.0L engine.


I'm not knocking the TT V12 because I own one and love it but it is hard to believe they intentionally made the engine so it doesn't breathe very well. Sure they can make 800 hp on 2 bar but it shouldn't take 2 bar for the engine to make that kind of power if it flowed very well. Many engines of similar size are over 1000 hp on 2 bar of pressure.

Besides, HP does not eat trannys. It's torque that wil twist a tranny apart. HP = tq * RPM/5252. You can have close to 900 HP with around the same torque that the Renntech 65 produces at 2000 RPM or around 800 lb-ft but the key is to have that torque available at a 5800 rpm and even much less torque if your engine spun faster. However, a stock 65 hp peaks around 4500rpm and stays flat until 5,500 and then starts to fall. When you push the turbos with a Renntech mod the 65 peaks around 4,200 rpm and starts to decrease all the way to redline.
800 * 5800/5252 = 883 hp

The fact that these engines don't rev very high hurts our peak hp but the lack of flow kills our highend torque as you can see from every dyno from a 600 or 65 engine. That lack of highend torque kills highend hp since they are directly related, see above formula. The tt 65 engine peaks very early and falls off like a rock off a steep hill. That torque curve either shows the engines inability to flow at higher rpms or the turbo's lack of efficiency. Either way, it's not good. Look at an efficient engine and the torque curve is very flat or it increases with RPMs.

If the problem is turbo inefficiency, why hasn't someone upgraded to a more efficient turbos. Is it that tight that it will not allow a slightly larger or more efficient turbo that didn't start loosing it's efficiecy after 3000 RPM?

You would think that Mercedes would pull out the stops on a car that approaches $200,000. It is obvious that they didn't pull out the stops on this engine or, dig, on our stupid unreliable ABC suspensions.

JLP

Funny Rob Allen has directly quoted 21.8 peak lbs of boost along with literature from AMG as well!

Here are a few quotes from different sources as to what PSI the 65 is running pal!

"TECHNICAL HIGHLIGHT: Mercedes let loose its performance department, AMG, on the 5.5-liter twin-turbo V-12, and the result is an utterly fantastic powerplant. With a bump in bore from 82.0 to 82.6mm and a stroke increase from 87.0 to 93.0mm, AMG increased displacement to 6.0 liters. It also significantly raised boost pressure from 14.5 psi to 21.8. Although the SOHC twin-spark-plug, three-valve-per-cylinder arrangement remains, horsepower jumps from an already ludicrous 493 to an astounding 604. The torque numbers are even crazier—738 pound-feet, up from 590"The net effect is acceleration that's out for blood.

" Despite channeling 22 psi of turbo boost, the SL65 doesn't snap you back into your seat like an American V8 — it rolls over you like roaring thunder. In the real"



I would tend to trust the ACTUAL people who built the car over some joe-blo tech using Star-di!

By the way the motor in your Cl600 is not the same as a 65. Different piston's, different rods, etc...

Blown V-8 you seem to be a know-it-all so rather than continue wasting my time going back and forth with you..........think what you want, because thats all that matters!

whoover

The tranny is certified for 1000 N-m, not 1000 ft-lb. Not coincidently, that's 738 ft-lb, the peak torque of the stock engine. The boost is reduced by the ECU in the midband revs to limit the torque to the transmission's limit. It's easy enough to restore boost to increase midband torque and peak HP (that's what all the tuners do), but it will frag your transmission if you use the max torque all the time.

BlownV8

Dude, didn't you see the J/K behind my last remark on the PSI. You are the one who is ATTEMPTING to be a know it all. How many times have I got to say that I did not know the boost pressure. READ WHAT I AM TYPING!

I'm not sure why you are even mentioning the differences in engine components in the CL65 vs the CL600????


So you are saying that the stock motor is hitting 21.8 or whatevertheheck PSI at 4500 rpm and cutting boost throughout the rest of the RPM range to save the tranny? In essence, what you are saying is the tuners increase the boost too but the dynos of the engine are showing an even greater decrease in torque as the rpm's increase? You are implying that Renntech ups the boost early in the RPM range and decreases it, in greater proportion as rpms increase, similarly to the stock ECU does and this is why the torque is taking a nose dive after 4200 RPMs?

I'm just trying to understand the low peak hp with high boost levels. However, whoover, what you are saying would make sense as to the reason the car is making such low hp numbers with 21+ PSI and 6.0L of displacement. My Renntech does produce max HP fairly early early in the RPM range and just hangs there until redline so what you are saying does make more sense.

Does anyone have a boost map on their dyno runs? That would be the proof in the pudding!

whoover

Yes, the stock ECU reduces boost at the natural torque peak to limit it to 738 ft-lbs. Boost comes on again at higher RPMs, resulting in a square torque curve from 2000-4000 RPM. The cam profile would have to be changed to move the torque peak any higher, but the "nosedive" to 500 ft-lb at redline is a fine compromise considering the engine also delivers 500 ft-lb just off idle! Restoring a normal torque peak (as the tuners do) is great, but it's at the expense of the engineering margin of safety for the transmission.

The stock engine, with the torque limiter, is a never-ending joy. I'm sure a Renntech-modified engine is even more fun, but I enjoy flooring the car with no worries aside from the Highway Patrol.

BlownV8

Thanks for your input!

DoctorV8

I think that is a reasonable explanation. For those who haven't seen it, here is the dyno graph of my stock '05 CL65. A whopping 559 rwhp.

https://mbworld.org/forums/cl55-amg-cl65-amg-cl63-amg-c215-c216/174524-bone-stock-cl65-dyno-results.html

BlownV8

Your car is a freak. You dynoed around 60 RWHP more than many with the 65 engine.

DoctorV8

Yeah, I would love to be able to read boost on my car...to see if it holds 22 psi higher in the rev band than most.

BlownV8

Don't ever let the dealership flash your car. You may lose that boost!