I was watching TRUCKS a while back and Gale Banks was on. They were talking about newer diesels and how they get such incredible power out of them. When they were talking about the turbo, he said that turbo lag is a things of the past. Thanks to variable geometry turbos there is virtually no lag. I've never heard anybody else mention these and I'm wondering if anybody here knows more.

 

I dont have anything to add but I am sure some of these armchair turbo experts will ring in soon.

 

I'm no expert but I know it is a very valid point.

Turbo lag is something commonly referred to by people that are virtually uneducated in the way turbos work, and probably swear by Superchargers.

Tecnically speaking, due to the fact that superchargers create parasitic loss and can not be 100% efficient turbos by default have the potential for higher/better output.

Why do you think people are doing turbo setups on $200,000 Ford GTs?

If properly designed and tuned turbos will outperform a superchargers and not have turbo lag.

 

I believe the new porsche 911 turbo is the first gasoline engine to use these turbos. Check out the Porsche boards, those who have driven it say it is a monster (but most 911 turbos are) They seem to work well on the Diesels and hope to see the technology move further into the gas engine segments. I have never driven a car/truck with a variable vane/geometry turbo, so I am not sure how they feel compared to a conventional BB Turbo.

 

Lumadar, thanks for your opinion on Turbo vs Super chargers but that has nothing to do with my question. I understand how both work and the advantages and disadvantages of both. Turbo lag is a fact though. It does exist. I've felt it. I'm asking how a VG turbo is different and how it reduces the lag.

 

Gotcha. Well I do not specifically know anything about VG turbos but it seems very simple..they likely produced a turbo that has a way to gradually adjust boost (adjust opening and closing size) at different RPMs to minimize turbo lag. Nothing crazy there... and notice how it says "virtually no turbo lag" it's the same as any normal turbo that is properly mathced to the engine size.

Of course turbo lag "is real" but it doesn't have to be a factor in any application if the turbo is sized properly. There is basically a trade-off between a massive (large) turbo and some initial turbo lag with insane peak numbers, or a smaller turbo and "virtually no turbo lag." Now many with argue a properly average sized turbo will offer both, but of course you won't get the absolute peak numbers or the absolute minimum turbo lag with a middle sized turbo.

anyway, I know I still didn't answer your specific question, but I hope it makes more sense now.

and if the end question you are looking to have answered is "Is it possible to have a turbo without noticable lag?"

The answer is an emphatic YES.

 

Thanks, I guess that is what I was asking. I'm still curious as to exactly how a VG turbo differs from a regular one. I know it produces more boost sooner. I guess I'm over thinking it. If anybody knows of a site that explains how and why it works that would be great. I'm not putting one on my truck anytime soon, if ever. I'm just curious and wondering why I don't hear of more people using them. It sounds like you can have the best of both worlds with one. Little or no lag and huge peak numbers.

 

Chrysler used VNT turbos back in 1990 on the 2.2/2.5L Turbo cars. The problem with using VGT/VNT turbos in gasoline applications is the higher exhaust temps then diesels. The Chrysler tubo cars had the problem of siezing the vanes from them not being exercised enough.

I used to work for a very well known corvette tuner who uses twin turbos. Trust me, a properly setup turbo system using the new ball bearing center sections and proper A/R ratios will make full boost by 2000 RPM and carry out through the entire RPM range.

TG

 

^ Good call, I had forgotten about the chryslers, although I know technology has progressed greatly since that time.

 

Apparently the new VQ turbos in the gas powered Porsche use a pressure plate (just like the cummins) and they don't use the veins so the problems they previously had are no longer there.

Say hello to badass power across the power band for all vehicles!

 

To explain the varible turbos in a nut shell:

Think of a Jet engine. When sitting at the end of the tarmac you here the engine spin up but not really producing any thrust, then they bring the vains in and woosh you are off.

Basically the part that causes the lag is the fact you are compressing air and that is resistance. You have to produce enough force to overcome said resistance. So you use a varible vain so that you spool the turbo up with no resitance and then bring the vain in as needed for boost.

They work really well and alot of the supra guys have been using them. They are still considered a new technology (even though they are not) because not many have ventured into the realm of needing them. My next build will be with a varible vain setup. Gonna put it in my wifes 04 mustang. I can set it to producee virtually no boost for daily driving, then set it for mucho boost at the strip

 

What's VQ? How are the vanes/pressure plate controlled? Electronically? Centrifugal clutch? Or would you have to make manual changes under the hood?

 

The new Acura RDX uses a variable geometry turbo. If you head into the Flash demo here http://www.acura.com/TLP/TLP_s001.html and then select "Turbo Engine" under the Performance header, you can see an animated presentation on how they made their vg turbo.

 

That's actually a very good example! Good link!

 

Borg Warner and Garrett both have different approaches. One of them uses Variable Vane Technology which actually changes the vane configuration. The other uses Variable nozzle technology which changes the size of the hole the exhaust travels through. Making the hole smaller will speed up the flow during low speed spooling the turbo earlier. Both websites have complete write-ups on the technology, however currently only one of them is being used on gasoilne applications, the other is still only used on diesel applications because of the exhaust temperatures according to the articles.

I have to agree with That Guy. I currently own 4 Supercharged vehicles but have also done lots of work with turbos. A proper turbo setup is very nice, but IMHO manifolds and heat management are the biggest issues.