What's the best choice - a K27/8 turbo or one of lindsey racings' "super turbo" like for an example the Super 75/T4 (I'm on a 3.0l). Please help me decide!

 

I think before anyone can give you answer a couple of questions need to be answered. What is the car going to be used for, what is your budget, and what HP range are you looking for?

 

I had a K27/8 on my car then switched to the Super 61.

The K27/8 ran out of umph at 17 psi. I could set the boost pressure higher but it would start dropping off at around 5000 on the dyno down to about 17 at red line.

The Super 61 had no problem pulling 21 all the way to red line.

The K27/8 did spool about 500 rpm quicker, but the K27 was not just an off the shelf turbo, it had been lightened more than the Lindsey's turbo builder would recommend due to balancing problems and it had a bullet on the inlet.

One of the things you need to consider is what boost level you are planning to run. A smaller turbo is always going to spool quicker but fall off at the end at high boost levels, and a larger turbo will have to top end boost but will spool a little later.

One of the major considerations in how much boost you are going to run is how you are going to use the car. It won't do you any good to have more power if you aren't going to use it. And example might be driving at an autocross. At an autocross you are mostly in lower gears. In those lower gears having more boost/power, even at the top end can be a hinderance and will actually slow you down because control is more difficult. Another thing to consider is tire size and compound. The more power you can get to the ground, the more power you will want.

 

Getting the best of both worlds (fast spoolup and lots of flow) is doable. When getting a turbo for your 3L you must decide on the power level you want as well the spoolup characteristics you desire. Getting a turbo to support lots of hp (500+rwhp) and to spoolup quickly (1bar 3200-3400rpm) is a balancing act..

A K27/8 is not a good choice for the 3L..

ALWAYS go for the largest area under the power curve. Peak numbers are useless when your power band is limited to higher RPMs..

 

I think we all need to know the "specific" application for your car, and how you intend to use it. Doing an autocross event is very different from street driving, let alone a track car. Regardless, I will have to agree with John (Vitesse Racing) 100%. I too have a 3.0L 8V, and just changed out a Lindsey Super 75 w/T4 hotside to a Vitesse Racing custom Stage 5 turbo. PM if you want.

 

There are some very good garrett compressors made today. Much better than any k27. The problem lies in the configuration. If the unit is not configured correctly it will be a dog. Only good for peak numbers. Or a turbo that spools quickly but falls off fast. For a street driven car. It's nice to have a broad powerband. As close to naturally asperated as possible. The best that you can do is match torque and hp as close as possible.This will give you the best solution. On the LR dyno chart page I see that the torque peaks very late past 4700 rpms. This indicates a large turbine and maybe a larger housing.
Peak numbers look good but a broad powerband feels better on the road. The downside is that a 500 hp car will be faster than a 400 hp car even with a shorter power band.This will become evident in the taller gears. There is no perfect answer.
Match the hp and torque and you will have a very friendly car. There is two ways of doing this. Large compressor smaller turbine or smaller compressor larger turbine. It looks to me that a 380 to 400whp 2.5 can be had with a good power band at moderate boost levels.

 

Thank you for all your input!

The car is being built mostly for track use (I just can't get enough of the nordschleife ). So basically I'm interested in a turbo for track use. Sure - I'm using it a lot for everyday driving during the summers, also some autocross, but the track is where this baby should belong

If money wasn't an issue my first and foremost choice would be to go with vitesse stage 5 kit (is it possible to buy only the turbo from that kit btw?).

By reading your answers it seems like I can sum up my choices this way:

Choice 1: Vitesse turbo (I think it's a bit too pricey for my wallet this winter sadly)
Choice 2: Lindsey racing "super" turbos. (I just have to try to figure out which one of them is best choice for me! Any ideas?)
Choice 3: K27/8

Is that a fair sum up? Where would you put a K27/10 in that list?

 

The k27/8 should be #1,736,645.
Only a fool would put that on your 3 liter.
Just being honest.
You will throw away 100% percent of the 20% larger engine benefit over a well tuned 2.5.

 

If you are aiming for KKK turbochargers (known for their reliability) then aim for a K29 for a 3-liter

 

I would recommend K27/11. It makes for a good match for a 3.0. Even the factory felt that. Its only oil cooled though and make sure its 7200 series. You can get them from the 964 turbo guys who are swapping them for something else.
Raj

 

yes. Vitesse will sell the turbo without the kit.

 

Hey that sounds interesting! Is there anyone in here with a k27/11 installed? It's a super tight fit I guess? Any other issues with this solution other than the tight fit and that it's oil lubricated?

 

A buddy of mine, Chris Caroll, runs a shop called TurboKraft (602-481-0264). He is the former head wrench of Powerhaus and he's got experience with K27 and K29 turbos used on 3.0L 4cyl apps. Give him a call - I'm sure he'll point you in the right direction if you're set on staying with a KKK turbo.

Vic

 

Another question How would a K27/11 compare to a GT3071R?

(gah! there are too many choices!!)

 

They are not comparable at all. Also, the "11" referes to the size of the turbine/exhaust housing while "GT3071R" only refers to a combination of compressor and turbine wheels.

The GTBB series turbos are the best there is. They are extremely efficient compared to other turbos plus they're dual ballbearing. A properly matched GT-turbo will blow any KKK-turbo away!