EDIT: I just re-ran my car on a local DJ (carolina auto masters in durham nc) and the #s were only slightly higher (within 20 whp) than #s 2 mos back from Sharif's dyno. Go figure - maybe Sharif's dyno is reading higher these days? Anyway, I stand corrected.

Who can personally vouch for this dyno reading lower than Forged's DD? There are multiple documented reports going the other way... Maybe on a cold day, a DJ might be able to get within 10% of Forged's lower reading since his dyno does not correct for atmospheric conditions and Dynojets overcorrect (so on a cold day would subtract more). Based on the numbers that come out of Z1's dyno, it looks right on target for a high reading DJ.

Anyway, if this thread tells you anything, it's that dyno readings are all over the map for similar sized turbos!

 

Im not gonna start a nutswinging match with you, if you want to feel good about that 500rwhp DD then keep thinking its such a "heart breaker"

But im just saying even the Almighty Sharif has acknowledged that they read similar, so you know its gotta be true
Just an example (one of many, just happened to be in the same thread) this guy made 289rwhp @Z1 wait isn't 289 less than 299?
ok back on topic, I plan to find the max of modified APS turbos within the next month or so, and i may even make a trip up for FP to get some DD #s

 

LOL

 

There's technically no such thing as a 'high reading DJ' at least anything more than a few hp. Inertia based dynos such as DJ are FAR more consistent than any load based like DD. It's not like the drum on a DJ loses weight which would have to happen to get a 'high reading DJ'. It's a fixed mass and a fixed equation... there's no room for error especially a non-corrected run which eliminates possible sensor reading errors.

 

By the same token, there is no low reading "heart breaker" DJ either as originally implied by rh_334. My only contention is the correction factors and if you don't correct for environmental conditions (which I believe DD shootout mode does NOT) then you're going to have bigger variances depending on run conditions. I have also found that DJ is much more consistent vs Forged's DD for my own car across weather conditions.

In regards to the difference of Forged's dyno vs a DJ, I base my conclusions off my own data, not anyone else's. In at least 4 different tunes/dyno days on Forged's DD vs a similar # of DJ "events" I have made on my own (hundreds of pulls). Consistently higher on a DJ, STD correction with a greater variance during the summer when the DD dyno shows a much bigger hit than the DJ corrected #s. And I know how those pulls are being recorded and under what conditions. I can take any car and go to any dyno and make it read 20 whp higher or lower by changing the heat soak status of the car. The #s are meaningless unless you control conditions. And it is absolutely pointless to compare a DJ to any DD dyno number rh_334 - you seem to be trying to validate Z1's dyno readings as legitimate by comparing them to Forged's dyno readings. A DJ is a DJ and is consistent. If a shop wants to cheat, they can claim one boost level and specify another, ice down a motor, spray N20 in front of the air intake etc. A comparison isn't valid and no validation is needed - we take everyone at their word.

In regards to what the OP is asking for GT28s, I think they behave like smaller turbos vs say the Greddy 18Gs, show similar high midrange torque, but do not have as much peak power potential and have similar spool characteristics. The nod I think clearly goes to the 18Gs. To get the same peak power potential you have to move to GT30s and they definitely spool later than 18Gs. I have yet to see a Garrett package that fits the 3.5L VQ better than the Greddy turbos. Perhaps a GTX28 will come out and address that?

 

a pair of normally sized housing Gt28s (not APS) like GTM uses are very capable of into the 700s.
the GTM 30 and 35s you'd need would have to use the special T25 housing, so u just can't buy off the shelf turbos.

I wouldnt think there'd be much reason to switch.

Are you planning on running E85 or race gas all the time? Max turbo numbers arent very important unless you have the octane and fuel system to drive that as a daily boost level.

 

oops double post....

 

havent decided on what the build is yet, waiting on insurance to decide what theyre going to pay to replace, filled up with what i thought was 93 at the gas station and turned out to be contaminated with disel... doing the tear down today and the adjuster is going to come take a look. as far as we know know after scope and compression test scaring in the cylinders and loss of compression across the board. So debating on bottom end build and just upping the boost (would have a 93 map and a c16) or BC stroker and sleeve it and leave the turbos for now, would just spool fast as ****

 

The rebuilt 2871r flavor of the original APS kit is good for about~550whp before they lose steam and spool a hair slower than the originals.

 

the compairson between turbo's/kits isn't all apples to apples either since greddy comes with external gates which should be good for more power; wheras the garret units APS uses are internally gated. i bought abushong's original APS kit which came with the BB original turbos, but the manifolds have the external WG port on them so the shop my car is at is fabricating a EW setup that will recirc back into the 3" downpipes. unfortunately i don't have money or time for a CJM fuel system so I'm stuck with the modified stock one that comes with the kit. i do however have DW 830cc injectors and the DW300lph pump, so with that we will see if these external gates do anything or not.

 

He has a GTM kit, not APS. different housings, so the APS limitations arent so relevant.

 

Plus, the GTM kit has external wastegates IIRC from pics I have seen in multiple threads.


Surprised nobody has brought up comparisons yet with the JWT 700bb turbos. Aren't those modified GT28's as well?

 

From what I understand:

JWT 530BB = GT2554R
JWT 700BB = GT2860R
JWT 850BB = GT30xx

Source for the first two: http://www.ztechz.net/id1.html

 

na theyre recirculated and internal

 

Hmmm... I thought I saw pics of GTM TT kits with external wastegates and open dumps. Maybe those were kits with the GT30 or GT35 turbos though.

 

theyre sold separately for another 1200 XD

 

You have the option to choose between the external wastegates with GTM 3'' down pipes or internal wastegates with all of their kits.

 

For another $ 1200 lol

 

ya but the internal gates are not limiters nor is the recirc'd dumps. its housing size, which the GTM uses real GT28s, unlike the JWT or APS.

Thats why you have to use those motor mount spacers.

 

Not my APS kit anymore, we will see how much of a difference it makes since the graph i posted earlier has a similar build and still running the stock housings.