Let's have a discussion about the history and evolution of the 28 series turbos.

From my understanding there have been 3 versions so far + the GT28 alpha turbo over the years for a total of 4.

 

Thanks ari for creating the thread. Seems the manufacturers won't give their specs (for obvious reasons).

I am interested what I can achieve with the old K16/2860RS turbos plus

- Injectors
- IC's
- Turbo inlet pipes
- Exhaust
- Custom tune

...on pump gas. What kind of approx. hp or approx. 60-130 time?

To date, I have heard I would be better off with K24/18gs or with the newer Alpha 28s, but there is a good deal of those older K16/2860RS turbos available to me.

I am looking for good road course driveability with approx. 650 hp crank, or in better sense approx. 6.5 sec 60-130mph time on pump gas.

I know both the K24/18g and A28's can deliver that performance on pump gas as seen from the members' rides here. But what about the K16/2860RS turbos? Not possible?

 

The best performance from the 16/28 hybrids was Arts car which I believe had a 6.14s 60-130 time on race fuel. You should probably pm Art4iza for details but I think the car was pretty maxed out on supporting mods. I think it dynoed less than 650 whp but it seems like it was on a heart breaker type dyno.

Another fast hybrid 28 car was Don's car (DMK). He had a 6.15s 60-130 and dynoed about 645 whp on race gas. Here is his 60-130 PBox and his dyno on pump and race. His engine blew a short time later...

The third fastest hybrid 28 car I know of, was Mike Wests' (Chinitowest). He ran a 6.26s 60-130 on race fuel.

These hybrid 28s are great for road course and street cars, imo. They have the same boost threshold as stock but generate much more power than a K-16 or a stock K24. Their weakness is that the power drops off pretty quick at higher speeds and rpms so they are not ideal for highway pulls or standing mile runs. You can easily get over 600 whp with them on pump fuel which can get you into the mid 6s 60-130.

The newer tial version is a significant improvement because it adds much better top end pull to the same low boost threshold.

 

I would start with defining your objective and budget. 60-130 times are measured by starting at a lower speed, say maybe 35MPH and getting a running start letting the turbos build boost. You start the run at full boost with the throttle plate wide open. Most chipped cars with a 7,000 RPM limiter do it with 1 shift from 3rd to 4th (although I have heard of 2 shift attempts). While certainly a test of torque and overall power, it's not a definitive test for driveability and throttle response. Your road course and street requirement makes me want to think you're on the right track with the Tials.

I'm running the latest Tial non-alphas. They are ball bearing turbos and are water cooled. Honestly it's too confusing as there have been several iterations of the GT28 turbos since the early days of GIAC tuned EVO GT700 cars. At some point I believe they were based on K16 housings. Not sure if they still are. IMO K24/18g while being the absolute best bang for the budget (especially when coming from K24s already) still maintain quite a bit of turbo lag. The GT28s are a better "street" turbo IMO. Meaning they are very drivable from a turbo lag perspective, especially in the lower gears.

Consider giving Tial a call directly. They make 2860s, 2871s and the GT28 alpha turbos as well as GT30s and GT35s. I'm sure they are a good source for straight up advice.

I think the 2871s may be a good compromise between cost and flow if you're not going with 24/18gs and can't quite justify the cost of Alpha 28s? The bigger compressor wheel may give you bit more top end flow. Haven't seen many of them around here.

Either way this has been a bit of an obscure topic. I think it will be great to learn a bit more on the topic

In terms of intercoolers, you will be hard pressed to find a better bang for the buck than the factory 997.2 IC.

 

Ari, it has been difficult to get alot of info on these turbos especially the alphas. I am far from an authority on these turbos but, I doubt many of the hybrid K16/28s are being produced now. I believe the Garrett GT-28 was put into a K16 housing so it would bolt onto a 996TT without any additional work and would give alot of extra power. Now Tial housings also bolt up to the cars and have a billet wheel to boot...

Now if Jake would drop by...

 

They also make gt30/k24's turbos like the gt28/k16's but was used on a older gt800 kit. I have a set forsale if intrested, from my brothers car with 3k miles.

 

I feel those tial 28's hybrids are hard to beat for street and road cars. They work well with the stock porting, cams, and intake runners on the 996 turbo to make a very crisp and smooth car. I seen a gt2871 car running T25 flange with a 64 A/R make 700 rwhp at 1.3 bar on vp109. Lots of fun to drive!

 

Would a close line be drawn between the tial Alpha 28 and the K24/18 setups in performance? Coming from a K24 car, seems like the cost effective method is sticking with the modified K24 units. What are the differences in performance vs. cost? I guess the supporting mods would be the similar if not the same? also could you bring the K24 upto date with billet wheels and such?

 

They are similarly performing turbos, with the Alpha28 getting the nod on spool and a little top end. If you already have K24's though, it's approx $1500 to upgrade to 18g's and wastegates. maybe not worth the extra $4k for Alphas, depending on supporting mods, which you will need to maximize both turbos.

 

From some dyno plots posted some time ago by Tony, it seems that A28's have a slightly fatter torque curve all across the rpm band. However, I agree with Mike, if you have K24's, upgrading them to 18g's is really a no brainer...
They may be old etc.. but as long as they're good to run a sub 6sec 60-130....they're more than enough for 99% of us.

 

K24s can now be fitted with billet 18g and 20g wheels

 

Yes, but they didn't perform as expected. It seems only 16/billet 16g worked well.

I think the consensus is that GT28 Alpha > 24/18g

and the 2860s are?? Better street power but not quite the top end?

I think this discussion really boils down to do you want to freeway race or drive on the street?

 

yep, we don't do the K16 or K24 conversions anymore because we have our own stainless steel housing that bolts right up.

 

Jake,
Could you comment on how the alphas compare to the hybrids and stock turbos in terms of performance both in flow and hp production?

 

yeah would love to hear about it also...having an X50 car with K24 turbos, would be much more inclined to save the $$$ and put it towards supporting mods and go the hybrid route with the 18g or 20g with billet if possible if I were to mod for big power down the road...