maxed out gt 28's
#21
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Im not sure the exact specs on the GTM GT28s but APS uses a small GT25 compressor housing and relatively undersized .64a/r turbine housing. So you can likely make more. Im not sure why people aren't getting more out of them though, i made 510 on stock block @ 11.5psi with these turbos, and Z1s dynojet consistently makes similar (in some cases lower) numbers that Forged's DD
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!
Last edited by rcdash; 05-16-2011 at 04:53 PM.
#22
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I don't believe it. 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.
But im just saying even the Almighty Sharif has acknowledged that they read similar, so you know its gotta be true
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
#24
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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.
Last edited by djamps; 05-12-2011 at 08:26 AM.
#25
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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?
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?
Last edited by rcdash; 05-12-2011 at 10:08 AM.
#26
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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.
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.
#28
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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.
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.
#30
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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?
#33
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JWT 530BB = GT2554R
JWT 700BB = GT2860R
JWT 850BB = GT30xx
Source for the first two: http://www.ztechz.net/id1.html
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