Dual ball bearing turbo

[Ian C]

Righto folks, I went home from work yesterday, and fitted my T67DBB, gave it a shakedown, then went out and gave it some abuse I'd already gotten a load of performance figures from the T67p a few days ago, and I got the same ones from the T67DBB, and these here graphs are the result. Also attached is the spreadsheet with all my comparisons in, and some notes (which you must read before asking questions as it should cover some of the more obvious ones )

 

The conclusion is, the DBB rocks for making the car more driveable. The data shows some impressive gains below 4000rpm which is where a lot of regular driving takes place. I've only done 40 miles in it but it feels better and now I know that isn't the placebo effect.

 

Not much different above 4000rpm but that's what I expected. I've got the same tests from 4000rpm instead of 2000rpm but they are less conclusive as a) the difference is smaller and b) it's far far harder to match the two tests up without skewing the results. So in order to not confuse the issue, I haven't posted any of that up. Suffice to say that above 4000rpm there is still a difference, but nowhere near as marked as below 4000rpm - we are talking 0.05 to 0.1bar boost ahead, maximum.

 

I also did a gearchange test and that indicated that in fact the DBB behaves exactly like the P-trim, and doesn't lose less boost during the (0.2s long) gearshift. In a 3rd to 4th gear shift, when I got back on the throttle both turbos spun up pretty much exactly the same.

 

I hope these results are useful in helping you select what turbo you want. They also show if a single turbo is "for you" or not. You only have to look at 3rd gear ratcheting up 15+mph a second to decide that though

 

-Ian

 

EDIT - I uploaded the wrong spreadsheet, the correct one is now attached.

T67DBB to T67p comparisons from 2000rpm.zip

[Guest Terry S]

Excellent info bud!

[uk-rich]

good work there fella, but when i got my turbo from powerhouseracing.com, he strongly recommended that a dbb is not worth it on any turbo below a t74 which is there stage 4 i think, i went for a stage 2+ which is based on a modified t67

he said the bearings will wear much quicker on a dbb unit

 

just going on what jarret told me, thats all

[Lucifer]

Yes this is true, but the figures spek for them selfs. At the end of the day its a trade off between replacing your turbo once a year or putting up with a little more lag.

[Ian C]

Hmmmm, how can a bearing with LESS friction wear out faster?

 

Garrett must have some nasty warranty claims if their cartridges all wear out within a year

 

-Ian

[Guest Terry S]

really, all those DBB on OEM cars LOL.

 

Mine seems fine BTW

[uk-rich]

because they have plain bearings that run on a film of oil, the dbb has ball bearings, which are lubed with oil, but they touch the races in which they run, which causes wear

[Ian C]

Well even I can't get longevity data after only 40 miles

 

And anyway, he was wrong about the performance difference so...

 

-Ian

[Guest Terry S]

There is more than 1 company doing DBB turbos guys

 

Porsche must be gutted and Garrett near bankrupt

[mkirby]

What sort of power at the wheels would you expect the turbo to put out??

 

I looked at the BB Vs Thrust bearing argument when i went for my turbos but with my 300zx theres simply no choices other than the HKS range (2530s) or the greddy range which i went for as its sooooo proven but it is slower to spool up than my previous BB turbos i had on my skyline but i find larger spooling turbos much easier to drive around town

 

Keep up the good work

 

Mike

[CJ]

Superb write up Ian

[Thorin]

Excellent data Mr C. Thanks.

 

 

Hmmm, still think it's a 61 for me though

[Guest Terry S]

The difference in that speed map is pretty impressive mate:thumbs:

[Tricky-Ricky]

I found that changing to a BB turbo on my S14 gave me quicker spool up at lower RPM and better pick up, and i know of quite a few people that have run BB turbos at higher boost for a lot longer than your average plain bearing turbo, so i'm really not sure where the short lifespan came from, i have never heard that said before.

[uk-rich]

only re telling what i was told

[Ian C]

Don't worry about it mate, it's nothing personal. Jarrett probably didn't have any DBB turbos on the shelf at the time

 

T61's don't spin up that much faster, figure 0.1bar ahead for the same rpm/time according to a brief glance at some datalogs I have. Of course, a T61DBB would probably be a different matter altogether

 

-Ian

[Lucifer]

I'll have a 61 DBB cut right back on the rollers soon, so ill post up the findings.

[Ian C]

The difference in that speed map is pretty impressive mate:thumbs:

 

Aye. Take 3rd gear for example. Floor it at 2000rpm in 3rd and by the time the P-trim is at 59mph, the DBB is at 68mph, and that's exactly the same car, just on boost faster. That's the difference that suprised me the most, I wasn't expecting such a large difference. That's all about drivability, which is exactly what I wanted out of it.

 

-Ian

[Lucifer]

Agreed. Can you not now fine tune the map to take MORE advantage of this?

[JamieP]

good results there ian, terry you have email

[paul mac]

I'll have a 61 DBB cut right back on the rollers soon, so ill post up the findings.

excellent write up Ian, i would be really interested with your findings Lucifer, doesn't Terry S run a T61 DBB, anything that helps low down grunt is defo to be considered

[8secSupra]

Hmmmm, how can a bearing with LESS friction wear out faster?

 

Garrett must have some nasty warranty claims if their cartridges all wear out within a year

 

-Ian

 

You guys are comparing apples to oranges as we Yanks like to say. The DBB turbos that are available to the aftermarket are NOT the same technology or level of reliability as OEM dual ball bearing turbochargers. Garrett has several divisions, one for OEM applications which we cannot buy, and Garrett Garage which makes aftermarket applications. In the US, you only have two major aftermarket manufacturers of DBB turbos, Garrett Garage and Innovative Turbo Systems. We use ITS turbo's in our kits, but have tested both names. We all agree over here that the DBB turbos tend to wear out faster and experience heat-related fatigue sooner than standard bearing turbos. This being said, DBB turbos were designed for high boost applications in the beginning (1.8 BAR+) so the thrust bearing would not fail from such severe shaft RPMs. They trickled down into the aftermarket slowly and people (like PHR) began to use them on different non-race applications. We've proven countless times on our chassis dyno that the difference in spool-up on any of our smaller turbos (GT60, 62, and 67) is almost not even noticeable. Maybe 2-300 RPM sooner when doing a back-to-back comparison on the dyno. Your dyno's over in the UK are much different than ours, and the method of reading is quite different. Our chassis dyno's have a minimum of 3000# of rolling mass at each tire, which gives more accurrate readings under load. If your doing the testing by rolling into full-throttle at 2500 RPM you will notice a difference in the DBB spool-up. However, in the real world of street driving, who actually gets a start at 2500 RPM? When you lay into the turbo at 4000 RPM, you wont even notice the difference between the two. Those with DBB turbos from us, have you noticed the whine of the turbo compressor wheel long after you shut the engine off? Thats the shaft still spinning along at 100,000 RPM with no oil for 2 minutes you are hearing. We've noticed a significant increase in heat-related fatigue of the bearings with DBB turbos.

 

Now, I sell both variations in the PHR kits, DBB and standard bearing. I could easily tell the customer that DBB is better and sell them a $700 USD more expensive kit. However, I tell it as straight forward as I know. I advise each customer these facts and let them make up their own mind on which route is best for them.

 

Jarrett at PHR

[JohnA]

Another thing worth checking is the exact size and shape of the compressor/turbine wheels as well as in/exh A/R ratios.

 

A slightly lower A/R ratio can make a BB turbo look like it's "spooling" earlier, where in reality the difference has nothing to do with bearing friction.

I remember this being the case a couple of years ago in an engineering forum I frequent.

[uk-rich]

see !!!!!!!!!!!!!!!!!!!!!

[Ian C]

It takes 27 seconds for mine to stop spinning off idle, not two minutes. If you don't do a sympathetic shutdown on any turbo you are asking for trouble. There is oil on the bearings, it just gets hot as it isn't circulating, but the water cooling jacket is there to ferry this heat away to stop coking issues (the water still circulates via convection even though the engine has stopped).

 

My results were from road testing, i.e. real life, exactly how I'll be using the turbo, not a dyno so I dunno why you are talking about the differences in dynos. The road speed graph shows straight away that there is a big difference in the low down drivability of the car, almost 10mph faster. I know no-one in a race or on the drag strip boots it at 2000rpm, and I've said ALL ALONG (did you read the start of this thread btw?) that there is minimal differences above 4000rpm and a T67 is on song almost instantly at those levels. It's the part throttle low to midrange where it makes big strides, and that's where most people drive that car most of the time. I couldn't accurately reproduce part throttle positions while driving on the street, it's almost impossible to hold the throttle within 10% of a given opening for any period of time, so it had to be 100% throttle for the purposes of the testing.

 

I'm not overly interested in the lifespan of the cartridge ion this thread, this is a thread about the advantages in spool-up over a 360deg bearing turbo in exactly the same setup. I don't want a slanging match over who is right and who is wrong on that front because I imagine you've got no hard data anyway, otherwise you'd have produced it, and we've had no failures yet

 

I was hoping that people would find this data, which I've busted my ass to get, genuinely useful. Alas so far it's just degenerated into a trader from the states wading in telling me pretty much it's bullshit, with no data to back up those claims. So where, seeing as you have access to the spreadsheet I've produced, have I gone wrong and mistakenly concluded it is a big improvement, hmmmm? Where's your testing results showing DBBs aren't worth the effort?

 

Pardon the animosity Jarrett, but I'm sure you can understand how annoying this is to me. I was going to link to the results on Supraforums but now I think it'll be more trouble than it's worth if people are just going to say "blah, who sells blah turbos, says it's bull therefore it is". What further evidence can I show ffs? It's better than just saying "there is no difference" or "it spools up faster" surely...?

 

-Ian