Turbo Reliability...It IS there

Herr-Kuhn · 05:56 AM

Over the years, there has been a lot said about how unreliable turbochargers are and how they really don't work well on the 928. Today I will use factual information to make it clear that these statements are simply not true.

I've been daily driving my twin turbo S4 most of the summer this year and the car has logged 13,000 miles since the installation. This is on a car with over 180,000 miles on the original engine and running in excess of 550 flywheel HP. The car can still get the same low 20s MPG as it did when stock. It has a cold AC and cruise control that work just as the did before the conversion.

I've driven my car on 4 long trips, twice to NC and twice to PA...each time without incident.

I've not had to worry, pull or inspect the turbos at all...they are working just as they did when installed 17 months ago.

Let's take a look at some of the typical anti-turbo statements:

There is too much lag: This one is my favorite and usually spoken by a belt driven guy. Lag is defined as the time it takes from when you drop your foot to when you have manifold pressure starting. In the case of my car, full manifold pressure is reached at 3,200 RPM when under loads. Also, consider that the power made is a function of mass airflow and parasitic loss out of the system. The bottom line is turbos make the same HP as belt driven systems but do it on less boost. Nobody can argue with 500 ft-lbs on the tarmac by 3,200 RPM.

Turbos make too much heat: The turbo does not make heat, the heat comes from combustion which happens in the combustion chamber. The turbo simply harnesses this heat to drive the compressor. About 1/3 of the energy from combustion goes out the tailpipe, 1/3 into the cooling system and 1/3 out the crankshaft. Consider that turbos extract heat from the 1/3 that is wasted and that there is also less fuel burned overall compared to a belt driven system. It can therefore be proven that the heat out the tailpie is actually less than a car running the same power on a belt driven system and as well, less heat into the cooling system. This is contrary to popular belief. People like to show photos of glowing red turbo manifolds...the fact is one can glow a manifold on a normally aspirated car cherry red too. Exhaust components on a turbo car usually last longer than others because they see less heat.

Turbos are unreliable The boost system in my car has yet to leave me stranded, anywhere. I don't have issues with overheating or broken crankshaft pulleys, bolts or belts...ever. To the contrary, turbos are the most reliable boosting systems going, this meaning the longest lasting and lowest amount of maintenance of any type of system...also the most efficient. Too many diesle rigs and OEMs using turbos to argue it otherwise.

Turbos are not streetable Turbos ARE streetable, in fact if you leave your foot out of my car it drives just like stock, there is no indication otherwise until you hammer down on the car. You can be running in the vacuum downshift and boot it and you're rewarded with a lot of power. Hang on and steer...it's not for the faint of heart.

Turbos are too costly: A good turbo system will cost some money, but when you consider the road manners of the car coupled with the performance increase they are well worth the cost.

Turbos will blow the engine: The fact is that any engine can be blown if the tune is improper, turbo included in that. The key is proper fuel and ignition management of the engine. Take a NA engine and crank 40 degrees of advance in and you'll break something too.

If you are not believing these statements, go and ask for a ride next time and you will see the performance is mind-blowing (no pun intended). Consider a lot of the statements made over the last 5 years regarding the use of turbos on the Porsche 928 are hearsay from people who have zero experience with the setup.

N2O-SHARK · 08-10-2008, 06:42 AM

I don't believe a damn word!

When do I get my ride in your car.

Well said for the naysayers!
All power adders have more myth than fact on the internet. Some guy turns up the boost on his stock turbo with out retuning the rest of the engine or redoing fuel maps, blows his car up and suddenly "Turbo's" are bad. Same for SCs and N2O.

When the finance minister releases the funds for capital investment in the infrastructure of my German economic fuel BOOST, I'll be Turbo as well.

rhjames · rhjames's Garage

like I told you a few months back, John-----

near 700,000 miles and then only a thrust bearing/front cartridge seal failure.

700,000 miles of brutal punishment---run hard, put up wet. 1400 + degrees of heat on the hot side every day.

--Russ

Herr-Kuhn · 08-10-2008, 04:45 PM

Also consider the technology has come a long way in the last 10 years...ball bearing units and better turbines and compressors just about erase the old "turbo lag". I still scratch my head when I see an old skool K-26 or K-27 on a 951...there are so many better turbos now. 3K is old skool, works alright but the new GT series is so much nicer and more responsive.

MarkRobinson · 08-11-2008, 05:16 AM

Bump: my turbo 928's have been perfectly reliable. My SC 928's always ran warmer, made less HP & Tq at the same boost, had the rattle-ish sound to them "hey man, is your AC compressor failing? Listen to that clutch!". Also, it's nice to never have to worry about a belt controlling your outting when you're SC'd.

I'd never go back to SC's, would never chance a stroker. There really is no better way to REALLY enjoy a 928 than fighting wheelspin at 80mph with 285's on the rear.

Herr-Kuhn · 08-11-2008, 08:22 AM

Yes, I have to say I am glad I never opened this engien up to do any upgrades. It's proof of how robust these animals are...I mean I have 183,000 miles on this car and it's making gobs of power. I know I could run up to 16-18 psig if I lowered the compression and installed larger injectors, but I'd be afraid of blowing the transaxle out of the car at that point...it's tempting for sure.

Herr-Kuhn · 08-11-2008, 08:27 AM

Forgot to mention, as we were dialing in my car and the boost, we overboosted because I had the boost turned up too high from the cockpit...it hit 16 psig and did so by like 3,400 RPM...at about 3,600-3,800 RPM the throttle was pulled, but not before the car smacked 640 ft-lbs to the tarmac, and it was just starting to level off. The potential here is enormous...I'm sure this system can lay down 650-700 WHP if the engine was built, in fact I think it would be easy to do.