what power levels are you looking at?

I am on the fence on selling my upgraded VTG turbos and going GT2 myself.

 

This is an odd post with a lot of questionable things, but a few of the major issues:

This is the point of increasing the size of the compressor, so the maximum boost can be increased without increasing the shaft speed beyond the safe limits. So your argument makes no sense.

At this point history has spoken. Many people have many years of track use on upgraded VTG's and it's fine.


I don't see how you think upgrading the compressor will cause reliability issue when a large body of anecdotal evidence suggests often reliability is quite good, and you also think small shop bearings and oil seals will be reliable when anecdotal evidence suggest it will not be. Look at the excellent reputations of many vendors that sell upgraded vtgs. This is why most shops don't do it.

 

Is removing and reinstalling turbos an easy process? I'd like to do this myself however, I'm not sure what needs to be done, any gotchas, and any other little things I should be aware of.

Perhaps there is a write up on here or better yet, a video...


I know, the search button is my friend...

 

basically 3 studs on the header 4 studs on the exhaust. soak everything on pb blaster at least 24 hrs ahead of time and watch removing any oil lines from the turbos. if they have never been off they may twist and ruin the line thus needing to order new lines and possible days of down time waiting on parts. new exhaust and header gaskets needed. they look like a large and small metal o ring

 

I had oil lines that would not come off initially. I heated them up with a propane torch and they came off fine.

 

I still have these if you are interested?

https://www.6speedonline.com/forums/...7-1-turbo.html

 

Guess I missed a few post,

Your almost correct TimeTomorrow! Great name by the way. I'm always looking for it! Since you stated "Major issues," to my response it's necessary that I respond.

I'm not going to pretend I know more (I may not) but, I would like to know more on your insite.

By your post, you note on compressor size. If I sit back, and consider compressor wheel speed in regards to shaft speed, wouldn't a more aggressive compressor wheel reach maximum shaft speed sooner with more velocity? I would only assume that the actual compressor speed would lead to more rotations at one point. For how long, I have no idea but, do you truly think that our turbos suddenly stop at exactly 100K?

On to your second point, I believe that the few that have "road tracked" their cars with this upgrade, do this successfully with a downtune.

Your last statement makes no sense to me. Maybe its "anecdotal" to itself?

I have had many conversations with vtg remanufactures regarding this same question. I respect them when they are upfront with me and tell me not to bother with it in regards to my application.



The OP had made this post relating to a "Blew a turbo" and, I have done that.

https://www.6speedonline.com/forums/...hats-next.html

Have you?

Anyhow, i'm here to learn so,

 

Thanks for all who have responded. I have picked up the set of EVOMS 65mm that were referenced earlier in this thread. Hopefully they will be as advertised.

For those following, I have attached an engineer's assessment of both turbos. It seems to read very similarly to the blown turbo thread linked to by elite1.

I was running GT2ICs, COBB custom tune, EP1, 98RON. With the custom tune I was experiencing a shudder in 5th gear (tip) going up hills at WOT. I thought perhaps it was the turbo intake pipes (stock) collapsing and reopening at those higher flow rates, causing vibration through the system, and maybe unbalancing the turbo shaft. It's all speculation.

A gentle word of warning to newbies like myself to tuning. Tuning is not without it's risks. Taking the stock hardware and pushing it beyond the limits that the stock software imposes is likely to end in tears if you don't tear it apart once in a while and preempt any problems (like looking for abnormal wear). In my case, 2 of my cylinders were leaking, and required the head to be removed. The valves were found to be slightly bent and needed machining. The damage is thought to have been caused by the valves closing agains trapped metal fragments.

The $$$ damage from this incident is likely to be around AUD$35,000. (dropped engine, valve machining, replacement turbos, replacement wing, replacement bumper, replacement exhaust, paint, labour). Yes, prices are crazy in Aus.

 

Glad this discussion has people thinking and always happy to discuss

With the compressor, the larger compressor wheel has a bit more weight and considerably more drag, so it requires more energy to spin as the increased volume of air drags the larger blades. This means that for a given amount of exhaust energy, the larger compressor will actually spin slower than the smaller would have. This will cause a subtle loss in spool up performance, but this is usually offset pretty well by the typical other aftermarket mods like exhaust, inter-cooler, and headers. This also means that at a given shaft speed, the bigger blades move more air. Exhaust gas pushes on the turbine to make the shaft spin faster, and intake air has to be pushed out of the way for the compressor to move which pushes back and slows the shaft speed. The more air the compressor has to move, the more it pushes back.

This is all pretty intuitive when once you think about everything you probably already know. If you want a 500hp turbo on one car and a 900hp turbo on another car, you don't buy the same size turbo but one with upgraded bearings and rotating assembly materials to support substantially higher rotational speeds, you simply buy a bigger turbo with similar bearings and materials.

"consider compressor wheel speed in regards to shaft speed, wouldn't a more aggressive compressor wheel reach maximum shaft speed sooner with more velocity?"

I'm having a hard time following you here. What do you mean by "more aggressive" here? The only way I can come up with that makes this a true statement is that if you change the geometry of the exhaust turbine you could increase shaft speed. For the compressor a smaller compressor with "less aggressive" geometry would lead to more shaft speed as the compressor is the brakes in the equation and the exhaust turbine is the motor.

I see the post you linked, but I'm unclear about the confusion. It looks like the diagnosis was clearly failed aftermarket turbo bypass valves. A bypass valve failure is extremely likely to cause a catastrophic turbo failure..... another edit: you also had leaking intercoolers, another likely source of turbo failure. [yeah didn't notice this until I'd already written all that... ] actually it might be terminology confusion. The "compressor" is the cold side that compresses fresh air and pushes it into it to the engine. The turbine is the side that takes the hot exhaust gas. I think this may be the root of the confusion. That post says a " the compressor wheel broke in two, one shot against the Cat convertor and the other just wedged itself into the turbo housing. "

a whole compressor wheel could never shoot against the cat, but a turbine wheel could.



increasing the size of the turbine is not always done and is tricky because unlike the supply of fresh air, there is only so much exhaust gas, so it's a much tougher balancing act with the sizing.

 

Great post Time! Very informative.!

Thanks.