GT35R v K27

[vas930]

Does anyone have any documented evidence that the GT spools faster than the K27?
I always read that some people feel it does.
Then I see Brian say he has not seen this to be the case.
I listen to what all you guys say. I have great respect for Brians knowledge.
Surely after all this time someone has done a documented test.

This question is sending me mad.
Anyone got some data.
__________________

[spence88mph]

Hey Vas, ask someone with extensive experience with both, the guy you got the headers off . My money is on the Garrett.

[911TT33]

+1 on the GT.

I've had a couple K27's before I eventually went with a GT. Everything else remaining equal (apart from smaller oil feed line and exhaust inlet flange), the GT just felt more responsive and less laggier. Also, I ran it with the water jacket open for years and had no reliability issues.

Never did back to back dyno testing tho... Although, highly reputable Porsche tuners are stating:

"Experience Shows with repeated dyno tests have proven their boost response is far superior to any KKK or hybrid "HiFlow" turbocharger."

[RarlyL8]

The difficulty is finding data where the only change made was the turbo and the turbos are of equivalent output. Many things influence boost threshold and the RPM range from threshold to full boost. Apples to apples would be something like a GT30 vs a K27S or a GT35 vs a K27HFS. KKK/BW also now has a new line of turbos out that will compete with the GTX Garretts.
All this being said I've not seen any equivalent high flow turbo spool significantly faster than 1bar by 2600rpm, which is what we see with the K27HFS. I say significant because bang for the buck is part of the decision process. The K27 is as close to a plug-in for the 930 as you get, conversion costs for the Garretts being a factor. Also KKK/BW made the K27 very robust where the "new tech" ball bearings are not. Because I do not manufacture turbos I have the luxury of choosing the best the market has to offer. When someone comes up with a turbo designed for the 930 that out-performs and out-lasts the K27 at a similar price point I will be all ears.

[vas930]

Thanks for the reply, Gents.
Looks like no back to back tests on spool up.
I will take the advice.
Thanks.

[Tippy]

If you are street, get the Garrett BB. You would want the quicker boost for a more responsive car. Garrett claims going to ball-bearing over journal - all else equal - will give you a minimum 15% decrease in spool time.

There isn't any guess work between BB vs journal.

They are comparing themselves - not competitors - by using apples-to-apples testing.

If you track with extended periods of boost, get the triple "K". These are the workhorses that more than likely will far outlive the Garrett's ball-bearing cartridge.

[vas930]

Thanks Tippy.
I do track the car and drive it hard on boost for long stints.
My old K27 is twenty years old and its time for a new one.
I think I will go for a KKK again for the reliability factor.
My question was related to documented evidence.
Is it 200rpm or 800rpm better, that type of thing.
As no one seems to have done the test back to back, we are left with opinion.
Thats fine, we have plenty of good experienced opinion on this forum.
I listen to it all.

[vas930]

Is it safe to run the k27HFS with non mod CIS?
Anyone ran this set up on a dyno for a safety check.

[JakobM]

you need to look at what drives a turbo...
Basically you can go the easy and commersial route = single scroll + ballbearing
Or you can go the difficult build but effient and reliable way = twin scroll + 360 degree journal bearings

If you really want faster spoolup time then I wouldnt spent one secound on ballbearing as the argument.
True twin scroll setup will eat anything you can through at it in single scroll setup whatever ballbearings or money spent. And Twin scroll means divided inlet with divided wastegate pipe collector. WG do also needs to be 100% divided all the way - many are not. Use your time and money there. It is pure physics. Each puls has halve size A/R to enter with full energy rather than loosing energy across multible cylinders (single scroll). Plus your detonation risc is higly decreased with Twin Scroll (less backpressure from neighbor cylinders on cam overlab) and thus you can run much more aggressive cams. 3.0L engines normally gives between 1000-1500rpm earlier spoolup compaired TS vs. SS. Something singlescroll $$ ballbearing turbos never will be albe to compete on. Top effect is also different. Look at single turbo race or diesel industry applications which need earliest possible spoolup and highest possible reliable applications. They use TS setup.

Rather than compairing bearings you should IMO compare which turbo support TS applications and choose size from there. You can go much more bigger, safer and efficient with TwinScroll setup.

[Tippy]

Can't you get twin scroll for the BB Garrett?

[JakobM]

As far as I know Garrett "OEM" start TS only as late as from GT37 and up...to reasons unknown
However some shops due provide TS turbine housings for smaller variants as GT35 and GT30
Maybe Garrett has changed this with the GTX versions...havnt checked lately
The lack of TS and A/R variable herefrom is IMO a huge disadvantage for the Garrett programme compaired to the comparable turbos that has its "genes" from the diesel industry

[vas930]

Thanks, Jakob.
Thats great info and makes sense.
However I dont want to become a test mule to find the right TS set up for my needs.
I just dont have that kind of money to try a range of turbos and test for the best.
I know Brian has been doing some work on a TS setup for up to 400hp apps like mine.
When something has been tested and for sale as a kit, then it may be of some interest.
For now, I want the best spool up I can get with boost to 6000rpm.
Thats why I ask about the K27HFS.
I know the K27s spools early, but it drops of at around 5500rpm.
I track the car, and with a four speed need the widest power band I can get.
Just not sure if the stock CIS will give enough fuel.
I do run the Andial fuel enrichment kit, not sure how much dif this makes.
Think I should put it on the dyno and see what the fuel is doing now.
At least then I know what I have to play with.

[RarlyL8]

The HFS will hit 1bar at 2600rpm, so no ball bearings will be much quicker given the same size turbo.
The 7200 starts to run out of steam above 5500rpm, the HFS and K27 hybrids will blow 1bar right past redline.
The turbo does not determine fueling requirement, but rather the output of the engine. Typically the stock fuel head will support up to 375WHP. The K27HFS should not be used on a stock engine as it is not being utilized. Minimum requirements are headers, muffler, large intercooler, and 1bar boost. This will bump you near the 375WHP number but should not require a fuel head recalibration. It will require an adjustable WUR to insure safe AFR's.
My 930 headers are all split plenum as benefit is had even by conventional turbos with this type of tuned system. Twin scroll turbos are like 2 separate turbos, one for each bank, so you can see how that would be quick to spool.

[Tippy]

If you know the best A/R for single scroll, it's a simple percentage increase already determined. I want to say you go 30% bigger on the A/R for the TS.