Still love them, and no plans this winter, but maybe in the spring if the guy from the other thread posts some favourable numbers...

Speaking of numbers, can't wait to see some from you once your build is complete.

 

Thanks Tom!
Rather high Pex/Pin ratio, clearly shows the retrictive nature of VTGs' hotside. GIAC has done good job in programming to keep engines alive, there's not much room for errors...must be a lot of heat there...

 

Well actually, a 2:1 ratio of boost to back-pressure is ideal, so at 30psi boost these turbos are working in perfect efficiency. At full boost and at max RPM we normally see EGT's around 900º, which is perfect for a VTG. Remember, they're built for us by Tial, who are more or less the industry leaders in turbocharger technology.

 

Here you go. There are two attachments. The first one has 3 graphs on it. A stock 997TT, our 65mm VTG's, and our full 68mmVTG kit. All three of these are cars with stock engines, never running more then 23psi.

The second graph shows our full 68mm VTG kit on a car with a built 3.8L engine at higher boost levels (28psi). No other hardware was changed except the modified engine and increased boost.

 

That EGT figure is quite nice and TiAL know their stuff

But Tom, I have to disagree on one thing, namely that ratio. There's a kind-of-a rule of thumb that when backpressure divided with charge pressure stays between 1.0 and 1.5 there's no problem. Over 1.5 starts to build up heat and over 2.0 the engine goes kaboom.
Under 1.0 is the place where the real power lays....like in past turbochaged F1 engines. Over here is a Fiat 1/9 that has 600 hp (out of 2.0l engine) and pulls to over 300 km/h on a mile. It drives to and from the airfield, no need for trailer. Pex/Pin is less than 1.0...

I also happened to visit a local speedshop a while back and got again some info about backpressure. I forgot to ask about IAT vs backpressure details, but it's effect to power become quite clear.

Shop's owner has a Comp D/TA class drag racer, Europe's fastest:
0-402 m 7,52 s @ 290,26 km/h
0-100 km/h about 1,1 s
0-235km/h 4,79 s

He also has his own Dynomite engine dyno and was testing a new turbocharger for next season. It was top-of the-line BB Garrett but somehow a slight disappointment, because it gave out less power than his in-house developed hybrid turbo. So what numbers are we talking about? Garrett was pushing close to 1100 hp, last season's hybrid about 100 hp more. Reason for this difference was backpressure. At 3.2 bar boost (Yes! The engine is 2.2l 4-cyl M3 one...) the backpressure was 2.8 bar. With his own hybrid backpressure stays at 2.2bar...
Lesson of the story: Turbine side becomes restrictive if it isn't matched to compressor. No matter how big is the compressor there will not be big hp if the turbine doesn't flow enough.

 

Well you're definitely also correct to a certain extent, but I think the comparison you're making doesn't really apply here. Even completely stock, the 997TT has a a very high pressure ratio. If we lowered the ratio on our setups, we would definitely sacrifice a lot of low end torque. We're also running on the factory Porsche engine management and VTG. The smaller 4 cylinder engines you mention are most certainly built for a specific purpose...drag racing. They probably have large turbines, stand-alone engine management, and anti-lag or some other enhancement to low end power. The turbochargers most certainly also require frequent rebuilding.

When we initially tuned our turbos, Tial even mentioned that we had some more room to go higher on ours...even as high as 65psi back-pressure...but we found it wasn't necessary.

The cars we build have to be ready to run flawlessly day after day in the hands of our customers, with excellent driving qualities and still deliver the power. Tons of street driving, 100's of track hours, and perfect reliability. I think we've found the best of both worlds to be honest.

 

Thanks, seems amazing, but why havent you done some 60-130 runs, it takes seconds and can be done safely? Or since you are in the US, do a easy start and just go for a high trap speed in the 1/4 mile?

 

Well, where we are located in Florida is a very populated area. The roads are all congested and busy and there's a lot of traffic.

Sure there are some quiet roads where it could be tested, but we've chosen not to take any chances with our cars, customers' cars, or our lives lol. Some customers have done tests, maybe posted on here but I haven't seen them besides KerCar, Arone997tt and a couple others. However, now that it's such a problem for people not to know...i will do my best to try to get a test next time I have a car here available.

We're comfortable knowing the power our kits produces. From those power numbers, the performance will come.

 

I think it would be much appreciated!

 

You can use mine-maybe at your open house? james

 

That would be great!!!

What are your current mods and do you run pump gas?

 

2008 tip. Champion's 700hp Werks package, Tubi street, 20" Champion RF67 wheels, ++++. and I use Sunoco 93 pump gas. js

 

Hmmmm, it would be great to compare to tips with 700hp package from different tuners, i can provide any 0-100, 60-130, 100-200 , 200-300 300-400;-) 1/4mile full mile, etc for comparison, i run pump fuel and meth so its almost like running on racefuel. I can also list my modds which i think are less than yours ;-)

 

[QUOTE=Tom@Champion;3748631

The cars we build have to be ready to run flawlessly day after day in the hands of our customers, with excellent driving qualities and still deliver the power. Tons of street driving, 100's of track hours, and perfect reliability. I think we've found the best of both worlds to be honest. [/QUOTE]

My specific interest is track-- circuit track and not drag strip-is that the track hours you refer to?
Have any of those cars been running 68mm?To maximise HP potential-- what supporting mods are required?
What affect has higher boost had on the rest of the engine?
What is the reason(advantage?) to stay with VTGs? I am trying to understand why not simply change turbos to other known quantities.

tia

 

Yes...when I say track, I mean race circuit, not 1/4 mile track. We have never built a car for the 1/4 mile. It's just not our interest.

There's two stages with our 68mm VTG's. Stock engine and built engine. Both stages require the same supporting mods, which would be a good race exhaust, headers, intercoolers, larger TB and plenum, y-pipe, turbo inlet pipes, software, and injectors. On a stock engine, we limit the power via software to around 650-675 AWHP. At this level, we're never running more then 23psi, which we've deemed to be completely safe on the stock engine. We have several cars at this power level with over 30k miles on them. On built engines, we use the same exact hardware with different programming and have gone as high as 850 WHP on a few GT2's, and about 775-800 AWHP on a couple 997TT's.

There a few advantages to staying VTG. The first and most important in my opinion is that you can still completely rely on ECU-controlled boost. Other turbos require the use of an external boost controller. VTG's also provide GREAT low end torque, they're easily reversible to stock, and have amazing daily driving qualities.