GT28 vs K24 pros and cons
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I agree with Mr. Walnut. I disagree that the GT28s are better than K24/18gs. I've been in several ball bearing Gt28s. They are a very good turbo, no question. However, they can surge (physics not the tune) and can be difficult to modulate especially if you're tracking the car.
Also, going GT28s is a much more expensive proposition with water cooling that isn't required on K24/18gs. Porsche does not use any ball bearing turbos in their production cars. I believe it's safe to say they know more than anyone on this or any other board concerning this subject.
Also, just b/c an OEM manufacturer doesnt use something doesn't mean its not good...thats just a silly comment...
I understand for many people here seeing 60-130 times and 1/4 mile data is necessary for them to come to a conclusion on which is better. I'm sure this data will come and until then we need to base our *opinions* on what data is available.
Also, in response to your marketing comments....lets not dismiss the fact that these tuners/vendors have been bringing more and more new technology, products and options to people like us. If they were not testing and "marketing" then we would not have as many options (or be aware of them).
.
Last edited by audikp; Jun 5, 2009 at 06:17 AM.
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I have a feeling it would be my 1st loss!
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I think the new GT28's look very promising, but I'm waiting to see 60-130 and 1/4 mile times from multiple cars with them before I form an opinion either way. What I will say is that K24/18Gs can produce some very fast times without a lot of boost, while still giving wonderful driveability.
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I would hold out and see how "007-911"s Tip holds out...
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^^ That's a good point and another question I have. I also have a tiptronic and would like to know what it can handle and what could be done proactively to address any potential problems.
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i'll just add a couple points in....perhaps more later 
about the OE use....lets not forget that GT28's are OE turbos on the R33 and R34 skyline GTR as well as a some SR20DET variants
i have never seen/heard of a GT28 go into surge on a 996, 993 or 997
the whole BB vs non BB thing: BB turbos are much stronger, have fewer moving parts and can take far more abuse than JB turbos...it's just an evolution in turbocharger technology things get better over time that is why you see these turbos spooling much quicker and holding the top end power
also, there is a JB GT28 option which is much cheaper!
about the OE use....lets not forget that GT28's are OE turbos on the R33 and R34 skyline GTR as well as a some SR20DET variants
i have never seen/heard of a GT28 go into surge on a 996, 993 or 997
the whole BB vs non BB thing: BB turbos are much stronger, have fewer moving parts and can take far more abuse than JB turbos...it's just an evolution in turbocharger technology things get better over time
that is why you see these turbos spooling much quicker and holding the top end poweralso, there is a JB GT28 option which is much cheaper!
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From what I have seen here, at 500whp, they start to take a beating. I guess there are people who can help, but it's not cheap. Contact member "Blackhorseturbo" here on the forum. Much experience in the Tip arena.
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i'll just add a couple points in....perhaps more later
about the OE use....lets not forget that GT28's are OE turbos on the R33 and R34 skyline GTR as well as a some SR20DET variants
i have never seen/heard of a GT28 go into surge on a 996, 993 or 997
the whole BB vs non BB thing: BB turbos are much stronger, have fewer moving parts and can take far more abuse than JB turbos...it's just an evolution in turbocharger technology things get better over time that is why you see these turbos spooling much quicker and holding the top end power
also, there is a JB GT28 option which is much cheaper!
about the OE use....lets not forget that GT28's are OE turbos on the R33 and R34 skyline GTR as well as a some SR20DET variants
i have never seen/heard of a GT28 go into surge on a 996, 993 or 997
the whole BB vs non BB thing: BB turbos are much stronger, have fewer moving parts and can take far more abuse than JB turbos...it's just an evolution in turbocharger technology things get better over time
that is why you see these turbos spooling much quicker and holding the top end poweralso, there is a JB GT28 option which is much cheaper!
Just to clear up some confusion...or add to it, how many variants of the GT28 turbo do you sell? BB, JB, alpha series bolt-on, K16 hotside etc..etc...
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the BB A28 and the JB A28
we previously offered the gt28 in a K16 hotside but that is now outdated with the new stainless housing we developed
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I know the turbine housing is different, but is the "alpha" GT28 comparable to the old style GT28 on the compressor side?
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If I got on it in first, it would wheel hop like crazy. If I romped on it in 2nd, more wheelhop. The track was pretty damn sticky that day.
I did get two other ones, but they're pretty null as there was an error in driver skill in both of them.
On the last run, I managed a 13.6.I also went 1-2-5 as far as gears go. I went to shift into 3rd, car bogged a bit. I thought "OMG I just got this effing thing back, it can't be broken!!" Then I looked down and saw I was in 5th. I figure since the run was already screwed, I'll just continue in 5th. Trapped 110-112 IIRC.
I did get two other ones, but they're pretty null as there was an error in driver skill in both of them.
On the last run, I managed a 13.6.I also went 1-2-5 as far as gears go. I went to shift into 3rd, car bogged a bit. I thought "OMG I just got this effing thing back, it can't be broken!!" Then I looked down and saw I was in 5th. I figure since the run was already screwed, I'll just continue in 5th. Trapped 110-112 IIRC.
Cossey,
Thanks for the info - that's interesting data, but I think we need a few more runs with drivers pushing the car through all the gears to know the true potential. Did you make any other passes and if so, what were the trap speeds like?
Out of curiosity, why didn't you get on it in 2nd? I can sort of understand 1st due to transmission wear and wheel spin concerns, but 2nd is normally not a problem with AWD.
If it gives you any confidence, I have launched my car from moderately hard to very hard in 1st every time (about 40 passes), but I can understand your reluctance to do it. If you stay away from drag radials, these cars spin like crazy in 1st, relieving a lot of the power from the transmission. In fact, I have to go a little easy in 1st to even think of hooking up. A high RPM launch, unless you really feather and burn the clutch, will result in massive wheelspin and a slower ET.
Thanks for the info - that's interesting data, but I think we need a few more runs with drivers pushing the car through all the gears to know the true potential. Did you make any other passes and if so, what were the trap speeds like?
Out of curiosity, why didn't you get on it in 2nd? I can sort of understand 1st due to transmission wear and wheel spin concerns, but 2nd is normally not a problem with AWD.
If it gives you any confidence, I have launched my car from moderately hard to very hard in 1st every time (about 40 passes), but I can understand your reluctance to do it. If you stay away from drag radials, these cars spin like crazy in 1st, relieving a lot of the power from the transmission. In fact, I have to go a little easy in 1st to even think of hooking up. A high RPM launch, unless you really feather and burn the clutch, will result in massive wheelspin and a slower ET.
If I got on it in first, it would wheel hop like crazy. If I romped on it in 2nd, more wheelhop. The track was pretty damn sticky that day.
I did get two other ones, but they're pretty null as there was an error in driver skill in both of them.
On the last run, I managed a 13.6.I also went 1-2-5 as far as gears go. I went to shift into 3rd, car bogged a bit. I thought "OMG I just got this effing thing back, it can't be broken!!" Then I looked down and saw I was in 5th. I figure since the run was already screwed, I'll just continue in 5th. Trapped 110-112 IIRC.
I did get two other ones, but they're pretty null as there was an error in driver skill in both of them.
On the last run, I managed a 13.6.I also went 1-2-5 as far as gears go. I went to shift into 3rd, car bogged a bit. I thought "OMG I just got this effing thing back, it can't be broken!!" Then I looked down and saw I was in 5th. I figure since the run was already screwed, I'll just continue in 5th. Trapped 110-112 IIRC.