View Full Version : bb t28 vs. "big 28"

11-07-2002, 01:33 AM
i posted this in another thread and recieved on replies, so i decided to give the topic it's own thread... curious to see the view/reply ratio...

does anybody want to discuss the pros and cons of a:

brand-new s15 t28 turbo
big 28 (rebuilt)

as far as ease of installation, definitive hp expectations(@ what boost), spool-up(@ what rpm, not just "quick" or "laggy"), cost, and longevity?

i have heard many different claims to both and i just want to sort out the BS so i can make an informed decision...

11-07-2002, 09:21 AM
For reference, here's vrtelektrique's thread on the S15 turbo install on a redtop:
http://forums.freshalloy.com/ubbthreads/showflat.php?Cat=&Board=UBB9&Number=168010&page=&v iew=&sb=&o=&fpart=1&vc=1

As far as the install, the big 28 would be a little easier since it is the same T-25 you originally had - just altered. Going off of his thread, there is some modifications that need to be done but it's nothing too bad.

I'd also like to hear some more discussion on this from people with hands on experience. My options just opened up a bit more as I'll be parts hunting in Japan this winter. If I come across a S15 turbo at a good price I want to have an idea ahead of time if it's something I want to buy or if I should go for something else... http://forums.freshalloy.com/ubbthreads/images/icons/smirk.gif

11-07-2002, 10:09 AM
Can we throw the Sunny GTI-R turbo in here also?

11-07-2002, 10:50 AM
i'm also curious.
where's greaser when you need him?

11-07-2002, 11:04 AM
I think its more a question of more power or more reliability. I dont think you will find a brand new S15 T28 though, that would be pushing it. Ball bearing is just nice due to their reliability. The S15 is good for around 320 to 330rwhp i believe, no sure on Big T28.

11-07-2002, 12:36 PM
Why couldn't you find a brand new S15 turbo? From what some of the guys living in Japan say, you can get a used (low mile) and new turbo for under $600.00.

11-07-2002, 02:49 PM
i've always been under the impression that bb=less reliability. also the s15 turbo brand new can be had for less than $900 at phase2motortrend.com can the s15 turbo really make 330 whp with stock motor and no cams?
anyone else know anything?

11-07-2002, 03:07 PM
I don't know how much more horsepower the s15 turbo is capable of compared to the s14 turbo but recently there was a post where someone made 307 hp on an s14 turbo. 307HP 299Ft-Lb (http://forums.freshalloy.com/ubbthreads/showflat.php?Cat=&Board=UBB9&Number=368765&Forum=U BB9&Words=307&Match=Entire%20Phrase&Searchpage=0&L imit=25&Old=3weeks&Main=368765&Search=true#Post368 765)

It seems maxed out at 1.3 bar. Very good numbers though.

11-07-2002, 03:51 PM
</font><blockquote><font class="small[/img]In reply to:</font><hr />
i've always been under the impression that bb=less reliability.


I don't think that's true. IIRC, the Garrett dual-ball-bearing system was developed for Nissan in the 80's to improve reliability for their racing program.


11-07-2002, 06:45 PM
</font><blockquote><font class="small[/img]In reply to:</font><hr />
I don't think that's true. IIRC, the Garrett dual-ball-bearing system was developed for Nissan in the 80's to improve reliability for their racing program.


thanks for shedding some light on the situation asad. do you know what hp numbers either of these turbos are capable of, or are you just trolling and trying to contradict me wherever you can?

11-07-2002, 07:09 PM
</font><blockquote><font class="small[/img]In reply to:</font><hr />
do you know what hp numbers either of these turbos are capable of


Nope, although the number I keep hearing for the FP Big28 is around 350whp.

</font><blockquote><font class="small[/img]In reply to:</font><hr />
or are you just trolling and trying to contradict me wherever you can?


No, I'm just trying to stop the spread of misinformation.

Perhaps if you weren't wrong so often, I wouldn't have to contradict you so much.


11-07-2002, 07:11 PM
thanks for all the replies (finally)...
so far, it seems we have established that the big 28 is easier to install, costs less or as much as the s15 t28, and has a shorter lifespan...

still waiting for people who have had personal experience with spool-up and definitive hp with these two turbos...
im not too versed on the technical aspect of turbos (a/r, wheel/housing sizes and such), so i was hoping we can get more into that...
also, as i understand, it may be reasonable to rebuild your own thrust bearing turbo... on that note, how much more difficult/costly would it be to rebuild the t25 into a big 28? can i find things such as housings and wheels on other usdm oem turbos? would the cost (if parts where brand new) and results be much different from that of a shop?
thanks for all the informative posts... http://forums.freshalloy.com/ubbthreads/images/icons/wink.gif

11-07-2002, 07:23 PM
what about ceramic bb turbos, asad, how are they as far as reliability?

11-07-2002, 08:04 PM
Turbonetics claims that their ceramic single BB (only on the compressor side) can handle something like 50x the thrust loading of a standard floating journal bearing. If that's true, I'd imagine that would also improve reliability, as the bearing wouldn't be operating as close to its limit.


11-07-2002, 08:36 PM
I have the forcedpeformance BigT28. I have been running 15psi and it feels as strong as my t28/t3 did at 20. But its not a very fair comparison becuase now i have an equal length tubular manifold and JWT S4 cams. I will get on the dyno sometime soon, right now i am in the middle of installing toda valve springs and JWT cam gears. When i get it assembled and put a few miles on it i will go to the dyno, sorry for the wait. I can tell you this: Even with my big cams i still am making boost below 3000 and am full boost by ~3350. Without the cams i would imagine you would see full boost ~3150. Spool up is almost instanious where as the hybrid i was using before didnt see full boost till ~3900. The BigT28 requires absolutely no modifications whatsoever, it is a complete bolt on affair. However, if you want to run some high boost you need the fuel to support it.

11-07-2002, 11:31 PM
i am slowly being sold on the big 28 or big t28... not sure the difference... probably going to wait till the stock t25 gives me trouble though...

11-07-2002, 11:38 PM
Aubrey, are the turbos listed on forcedperformance.com suitable/available for the sr? do you have to pay more? what are your experiences with them?

11-07-2002, 11:45 PM
'91 Hatchback

Ummm...yeah they're for the SR

Z from Japan
11-08-2002, 01:32 AM
</font><blockquote><font class="small[/img]In reply to:</font><hr />
I don't think that's true. IIRC, the Garrett dual-ball-bearing system was developed for Nissan in the 80's to improve reliability for their racing program.


Maybe this can help shed some light on the subject. The BB Garrett in the mid 90's is completely different from the newest ones comming out. I have had my hands on both and they feel and sound completely different. The older type has more shaft play even when new and you can hear what sounds like a single ball bearing slapping around inside. The newer ones (also HKS GT series) are very tight and sounds a little like the bearings are sliding against each other making a low steady hiss.
I did get a hold of a pair of nearly new Nismo BB GT25 turbos for the R34 GTR and they have the same BB design as the HKS GT series. I don't know about the S15 turbos as I haven't obtained one yet. They are still pretty expensive. I suspect that Garrett has now done away with the older BB design.

11-08-2002, 01:43 AM
ForcedPerformance is one of the most respected turbo builders in the dsm community. Take a look at this page http://www.dsmtimes.org/ Five of the top 10 times in the country are achieved using a forced performance product.

11-08-2002, 02:24 AM
I was thinking about the Big28 today.....
if the stock T-25 is "inefficient" above 1 bar
then I would assume the Bigt28 would be also, why not?

IF this is true then the Bigt28 is making for example:
320hp @ 1 bar?!? If not true then when (estimated psi/bar) does the big28 become inefficient/max out?

What does FP do that enables you to boost a rebuilt/tweaked non-ballbearing t25 to 20psi (if that is where it maxes out)?

It seems the big28 is very potent turbo- but since it began life as a t-25 you could max it out/place more wear and tear on it pretty quick.

11-08-2002, 10:24 AM
What forced performance does is take your T25 bearing housing and put in a bigger turbine and compressor wheel (and machine the housings to fit the larger wheels). If course, I'm sure they won't give away the specs on exactly what wheels they use.

Thus, depending on what wheels one uses, they can use a compressor wheel that is efficient at higher pressure ratios than the stock T25 compressor, AND has a free-er flowing turbine side (with a stronger turbine rather than the ceramic turbine wheel used in stock S13 T25's).


11-08-2002, 01:34 PM
What's the most power anyone has heard being made on a T25? Just curious...


11-08-2002, 02:34 PM
no dyno #'s....best i pulled to date was a 12.8@109 (1.9 60ft), with the safc untuned, stock turbo, motor, ecu, and Open diff...obviously a built motor would produce more out of the t25.....our ser with bluebird motor went 12.3 on a fully stock motor, stock exhaust, stock t25....

11-09-2002, 01:41 AM
The engineer at Forced Peformance (Robert) told me the turbo will be efficient up to 22psi, and will hold that much till redline. I havent put it up that high yet.

11-10-2002, 12:25 AM
abailey-what boost were you at to make the 343 whp?

11-11-2002, 03:04 AM
still some unanswered questions/ extra info i was hoping people here knew...

11-11-2002, 03:48 AM
Questions such as:................?
There are only a small handful of SR/BigT28 owners on here (count on one hand?).
You might be better off corresponding directly with FP or dare I say it- browse some DSM forums. You can learn alot from the DSM camp!

11-11-2002, 05:39 AM
That was with the T25/T3 combo at ~21psi. I havent dynoed with the BigT28 yet.

11-11-2002, 01:27 PM
aubrey, can you list the differences in the t25/t3 vs. the big28 vs. the big t28?
it semms like there are so many variants of the same type of turbo.
opinions on all three?
FP carries the big 28 if im not mistaken, so i think i will be getting that in the future, but i would like to know about the others...

11-11-2002, 04:55 PM
Aubrey, have you decided how you are going to set your cam gears at? I have the s4's, cam gears, grex springs, tomei RAS, but it's not installed yet. JWT said to advance the exhaust side 1 setting, and retaqrd the intake 1 setting (2.5 degrees). They said this would reduce overlap and increase performance

11-11-2002, 08:10 PM
I am going to use the settings that JWT recommended for the cam gears, they tested and tuned them so i trust thier opinion. I got the head back from the machine shop with the new valve springs installed (Toda) and will have the car back together and running tonight.

carluch240: The big28/bigt28 are the same thing, I think people are just sometimes adding the "T" and sometimes not. It uses the factory turbine and factory compressor, but they are bored out and larger wheels are installed. The hybrid turbo i had was too laggy, boost on this turbo is almost instanious. The boost with the hybrid pulled harder and harder till redline, building more power as the revs rise. The BigT28 hits like a ton of bricks at a very low rpm and pulls all the way to redline. I think the BigT28 will have a much better curve on the dyno. We will know very soon. I would recommend going the bigT28 route from Forced Performance if you want ~350rwhp. If you want over 400 go T3/T4.

11-11-2002, 08:17 PM
cool, thanks for all your help... i think i will get the big t28 when my t25 blows...
btw, do you know what kind of turbo william (on FA) had? was it big t28 or t25/t3?
he sold it to a friend of mine and i was curious what he has...

11-11-2002, 08:59 PM
i'm think i am going to go with garrett's gt25 turbo in the very near future. i haven't decided which a/r to go with .64 a/r or .86 a/r yet though...may be .86 with some nice mid range cams..... ArrrGGGghhhhh (tiger claw action) http://forums.freshalloy.com/ubbthreads/images/icons/grin.gif

depending on the a/r the power ranges any where from 325-400 rwhp and very fast spool up due to the BB.

11-12-2002, 04:25 AM
I just picked up the 2540 a couple of weeks ago. What are anyones thoughts on that turbo? Right now i'm running power fc, 555 cc injectors, gtr fuel pump, and z32 mafs. I'm gonna be installing it in a couple of weeks. Any ideas?

11-12-2002, 03:24 PM
which turbo has the potential to make more high end power: big28 or t25/t3?

11-12-2002, 07:39 PM
what chou talkin' 'bout, madness?

11-12-2002, 09:24 PM
I've got the Forced Performance BigT28 also. It's a great turbo. Makes good power, full boost at 3200rpms. I'm only running 10psi, all stock internals with metal head gasket. I haven't had a chance to dyno since my rocker arm went out on me.

I use to run a T3/T25 with a super 60 trim compressor wheel and stock T25 turbine. Boost was quicker on this turbo, but the high wasn't that good compared to the BigT28. I'm pretty sure that Forced Performance is using a 60 trim compressor on the BigT28. My old turbo (T3/T25) had a tiny chip on the compressor housing from the compressor wheel. When I got it back as the BigT28, it was the same, no grinding out like the turbine side. Which lead me to believe it's the same. Just in case anyone was interested. Turbine side, NO idea!!! http://forums.freshalloy.com/ubbthreads/images/icons/confused.gif

11-13-2002, 12:35 AM
what'chou talkin about nismos13silvia?
are you saying you think they're basically the same turbo?

11-13-2002, 01:26 AM
No, no, no. Sorry if I got you confused. I was just saying that the compressor could possibly be a 60 trim. Since the compressor housing wasn't ported out, "maybe" they used the same trim as my old T3/T25 (60 trim).

The turbine side has been totally redone. You can tell how much they ported out, not from the pictures. I don't know or have any idea on the size or specs.

DEFINITELY not the same turbo!!! http://forums.freshalloy.com/ubbthreads/images/icons/grin.gif

Here's a few pictures. http://www.eframes.com/default.asp?guestalbum=31268.6100 Some of you guys probably seen them already. Could not compare the turbos together since I sent the old one out to get rebuilt.

11-13-2002, 04:02 AM
William, wasnt he the one with the CTC kit 420rwhp? That was a larger turbo--T3/T4 maybe?

11-13-2002, 01:01 PM
he had a t3/t25 hybrid before that and made ~300whp

11-13-2002, 05:06 PM
u can't go wrong with an FP Big28... or any T28 offering, for that matter. Even if u outgrow it, you'll probably have no trouble selling it.
"heavy" DSMs run low 12s, so an s13 should do better
SR T25 have better housings than the DSM T25 cores
Only issue is the ~$900 (with shipping 2 way) price tag takes the sparkle off abit - not much turbo for ya dollar. A NEW 16g will match its performance for $4-500 (depends)... BUT plug n play is THE selling feature for 2nd gen DSMs I guess... SR too
other options that use new? cartriges;

prices look good... they may be able to do somethin' 4 u
DSM guys luv 'em

11-13-2002, 06:40 PM
Yes, and you forgot to link forcedperformance's page:

11-13-2002, 07:15 PM
i thought it was 750, and you send them your turbo...
900 would be for "just" the turbo. correct?

11-14-2002, 07:19 PM
$900 is without a core. I sent them my old turbo. Total for me+shipping was $810. Cheaper than a S15 turbo, I think they're $950+shipping.

You really can't go wrong with this turbo. I can't wait to get my car running good again with 550cc injectors and turn up the boost, 18psi!!! But it's cold now and will be snowing soon, here in the land of cheeze. http://forums.freshalloy.com/ubbthreads/images/icons/grin.gif So, have to wait till next spring.

11-14-2002, 07:34 PM
phase2 sells s15 turbos for 895+shipping.

11-14-2002, 09:54 PM
On the big28's are most of you running HKS actuator upgrades?

11-14-2002, 10:57 PM
I want a big28 soooooooo bad now http://forums.freshalloy.com/ubbthreads/images/icons/grin.gif

11-15-2002, 01:28 AM
True, the S15 turbo is a little more expensive but 1 wont produce as much power and 2 is not a bolt on affair, you have to change some pipes, lines, etc. Ball bearing is a plus though. The forcedperformance bigt28 upgrade is 795 for sr turbos and 750 for DSM's. Shipping usually runs about $15 via UPS.

11-15-2002, 02:30 AM
how necessary do you think upgarding the actuator is?
what will i gain by doing so?
i've heard they're a b!tch to install and set properly...

11-15-2002, 04:54 AM
i wonder if theyre would ever be some variaton of the bigT28 on ball bearings.

11-15-2002, 05:06 AM
The HKS actuator is extremely easy to install and doesnt require any adjusting once its installed if you plan on using a boost controller. The wastegate arm is threaded and the further you twist it in, the higher your base boost is. So if you have a boost controller just screw it on there tight enough to pull the wastegate shut and adjust your boost level above that with a boost controller. I really dont know if its necessary: My boost has been falling off from 19 down to 14psi. I was told by both forced performance and JWT that it was bc of my cams--I needed to get cam gears. I bought cam gears and the HKS actuator at the same time. I installed the HKS actuator first and the boost still does the same thing, so I dont think its the wastegate. Forced Performance and JWT said i need to dial out some of the overlap in order to hold high boost, i was putting my chain tensioner in tonight and the oily little [censored] slipped through my fingers and broke into three pieces. I guess i will find out if the cam gears fix it whenever i can get another chain tensioner http://forums.freshalloy.com/ubbthreads/images/icons/frown.gif

11-15-2002, 11:15 AM
Aubrey -- you might want to try setting the base pressure of the HKS actuator higher. Remember, the exhaust manifold pressure is going to be much higher (probably about 2x!) what the intake manifold pressure is, meaning you have around 40 psi trying to force that wastegate open from the inside -- meaning that if the exhaust pressure forces the wastegate open, there's nothing the boost controller can do to stop it. So...give that a try, I'm interested to see if it has any effect http://forums.freshalloy.com/ubbthreads/images/icons/smile.gif


11-15-2002, 11:50 AM
does the hks actuator hold 14psi to redline? ATM my stock actuator goes to 14psi for awhile (when i set it at 14 that is) then leaks down to 11 or 12 at about 6200-&gt;redline

i ordered the actuator, but wondering if its worth it if i need cams too:(


11-15-2002, 01:17 PM
my bc is still set at .6 bar and it spikes to .7 or .8 depending on the weather when i get to 5500 or so rpm. i assume this boost spike is due to the wastegate actuator because it still spikes that high with the bc off or disconnected.

11-16-2002, 04:50 AM

a few pics of my turbo here. can anyone tell me anything i may not know about it by looking at it? (i'm an idiot i know)

maybe the links will be better size.
http://nopistons.net/modules.php?set_albumName=album66&amp;id=aar&amp;op=modloa d&amp;name=gallery&amp;file=index&amp;include=view_photo.php
http://nopistons.net/modules.php?set_albumName=album66&amp;id=aad&amp;op=modloa d&amp;name=gallery&amp;file=index&amp;include=view_photo.php
http://nopistons.net/modules.php?set_albumName=album66&amp;id=aab&amp;op=modloa d&amp;name=gallery&amp;file=index&amp;include=view_photo.php

11-16-2002, 07:00 AM
I think the reason your boost is falling off is because of the stock actuator--With the HKS unit you will get much more steady boost levels and less spikes. When i had my stock turbo i remember the boost would spike up to 16 then drop back down to 14 then by 6200 it was down to around 12-13. I dont know anyone that has installed the HKS actuator on thier stock turbo for a good comparison. Maybe someone here will speak up.

P.S. I finished installing my cam gears tonight! It was raining and i have my drag radials on the back so i had to be somewhat careful. I got in third and about 60mph stomped it. It spun for most of the time and i had to come in and out of the gas. For the times when it did hold it seemed to be holding the 18psi i want to run pretty well. I really want it to clear up out here so i can really see if they were worth it. --I have the S4 cams and my boost was falling off. Both FP and JWT said i need the cam gears to dial out some of the overlap.

11-17-2002, 06:39 AM
Asad, i was going to try your suggestion but ran into a problem tonight---see my other thread for details:

http://forums.freshalloy.com/ubbthreads/showflat.php?Cat=&amp;Board=UBB9&amp;Number=388479&amp;page=0&amp; view=collapsed&amp;sb=5&amp;o=&amp;fpart=1