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Hi all. As a quick introduction I'm a UK Supra owner and the technical section moderator of mkivsupra.net. I've been running a Boostlogic T67 setup for a couple of years and have found it very agreeable :) When the DBB version of the T67 came out I got in the queue very early on, and after the backlog had cleared my turbo rocked up in blighty recently.

The thing about DBB turbos is that, as far as I could see, there wasn't any actual data out there about how much "better" the turbo is compared to non-DBB. There was a lot of "it'll spin up faster" and so forth, but how much faster? Is there a real world difference? As I was going to change from a T67 to a T67 DBB I thought I'd actually get some performance data rather than just relying on the "seat of my pants" dyno so that others can look at the data and make their decision...

I used the E-Manage Ultimate's onboard datalogger to get the data. The sample rate is 20ms. The testing was done on the road. The gradient varied a little but nothing major (it's flat where I live) so I don't think that affected anything, especially as I tried to do all the runs on the flat. The T67p runs were done 3 days before the T67DBB ones, ambient temps were within 4degC, and absolutely nothing else was changed on the car - not even me attempting to set up my boost controller properly ;) So as far as an ordinary Joe Public guy can do, the results are pretty reliable and accurate.

I'd also like to point out that I don't sell stuff, so I'm about as unbiased as I can be :D I also had the opportunity of going back to my T67p if the DBB was a crock so I was in no way obligated to pretend it was better for any reason :)

Anyway - enough rabbiting on, what about the conclusions?

My conclusion is, the DBB rocks for making the car more driveable :) The data shows some impressive gains below 4000rpm, which is exactly where a lot of my regular driving takes place. Having done nearly 1000 miles on it since doing these tests, I wouldn't go back to non-DBB. No loss of top end power, and on boost much earlier. You can see on the graphs that the DBB outruns the P-trim by about 0.2bar in most circumstances. The real-world result of this can be seen on the road speed graphs where some frankly outstanding results showed up, getting nearly 10mph over the p-trim on an in-gear rolling start!

It's 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 due to doing this on the road. So in order to not confuse the issue, I haven't posted any of the 4000rpm+ results 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.

The car spec is:
1996 6spd manual
T67p / T67DBB turbo
BL tubular manifold
BL 3" DP and exhaust
720cc injectors
HKS 256in264ex cams
E-Manage Ultimate

I have a 272 intake cam on order to test out the theory that reverse staggering is extremely beneficial to a single turbo setup on the 2JZ. I'll try and do the same testing to see if it works :)

Anyway - graphs:






And the data for your perusal:

t67p_t67dbb_comparisons.xls

I hope this info is useful in helping you decide what turbo and bearing type you want. It also gives an indication of how drivable a single turbo Supra is :)

-Ian
 

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Moderator, l337 M0d3r4t0r
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wow that is absolutely amazing thanks for sharing.. You should post this in the dyno section or even the general section... i think thats a better home...

What exhaust housings where you using on the two turbos?
 

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It's on a .68 housing...

It is indeed excellent info - proper real world results.

Compare these results to a T04Z and you'll cry if you own the HKS Turbo!!
 

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What a great post. Thanx for your time. I am almost done installing my WOTM/PTE 67DBB. I CAN'T WAIT!

BTW, what FMIC do you have?
-jt
 

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So it looks like the spool up RPM is the same..I.E. they both hit 1.0bar at the same RPM, but the DBB turbo gets the car to that RPM quicker. Thanks for the results. Turbo would be great coming out of a low-speed corner. Looks like about a 400ms difference in acceleration.
 

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jt granberry said:
What a great post. Thanx for your time. I am almost done installing my WOTM/PTE 67DBB. I CAN'T WAIT!

BTW, what FMIC do you have?
-jt
In Ian's absence...it's a Blitz 2Row...it's been on the car about 4 years now!
 

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cant wiat to see your results on the reverse staggering. I have really wondered about that and if I wouldnt have went dbb from the start this thread would ahve really helped me and I am sure it has others keep up the good work and make sure to post the results of the reverse staggering

Thanks,
Anthony

PS dyno section posting would get more views and therfore help more people
 

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It's all ball bearings...
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Ian C: Thanks for putting in the work to collect data on the 67 vs 67DBB comparison. This appears to more or less confirm the conventional wisdom about DBBs that phorcefed00 mentioned (spool-up vs time to hit the corresponding rpm). It would be great to see these graphs with data from other turbos overlayed on it (per Alex Holdroyd's comments about the TO4Z). Great to see real world data on this turbo, it only makes me more anxious for my 67 DBB to be up and running. Thanks again.
 

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great data it beats the spool time every time. im changing my fuel system over then i'll prolly go dbb.
 

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Wow, it looks like the DBB really rocks the house! Good work!

Joe
 

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nice info, thanks for sharing. I wonder what the price difference is between the DBB and non-DBB turbos?
 

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REVTECHRACING.COM
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Hau said:
nice info, thanks for sharing. I wonder what the price difference is between the DBB and non-DBB turbos?
$250.
 

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Great writeup!! Looks like this will be my next upgrade when i get fuel to support the power.
 

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Alex Holdroyd said:
In Ian's absence...it's a Blitz 2Row...it's been on the car about 4 years now!

Damn! I am using the Greddy 4 row myself. I want to see the difference.
 

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That is really helpful information. Thanks for taking the time to quantify the numbers for us! :bigthumb:
 

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Ian-

That's totally awesome. Alex D was just telling me about the T67 DBB. He put one on and loves it as well.

I took the liberty of plotting boost pressure vs. RPM in 2nd and 5th gears. You can see a little difference there.
http://www.its2.uidaho.edu/cordon/dan/automotive/Cars/Supra_Images/2nd_Gear.jpg
http://www.its2.uidaho.edu/cordon/dan/automotive/Cars/Supra_Images/5th_Gear.jpg

In the Corkey Bell book on turbochargers, they decfine "Lag" as two components. One is the time it takes from when you open the throttle to when the turbo spools up. The other they call "boost threshold" and it is more like how much RPM the engine needs to hit for the turbo to kick in. The data you collected shows a small improvement in boost threshold. In order to look at the other concept here's an idea for a test:
Run the car at say 4000 rpm cruising down the road. Log RPM, boost, and throttle position. Then step on the throttle fully and see how long it takes for the turbo to reach full boost. Usually this is where the BB turbos really shine over the journal bearing turbos.

However, since it's a bit PITA to swap turbos again for this comparison...we'll just have to wait until I have a journal and DBB T67 to play with :eek:)

Thanks for sharing with us-
 
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