GT35R vs KKK K27HF

jbrown · 04-12-2015, 07:59 AM

So I go to one of my favorite state parks to take a ride the other day and I notice like gray smoke will under boost. I notice it only does it in the park. So I am thinking I have to much oil in my car. I was on the high side. So I take some out, go for a ride around local roads and no smoke good to go. I go back to state park and same thing. I figure SH-T I must have a bad turbo (GT35R). Take out the old K27HF and put it on, same thing. So now I am stumped. The car does not burn oil, runs like a champ , rebuilt about 5000 miles ago.
I am in the park today and notice a car go by me and I see some gray smoke. I pull my car to the side and check out the road. What an IDIOT I am. The road still has sand and dust from the winter all over and my tail pipe aims down a little and I was just blowing the crap off the road as I was driving agressive. That's why it did not do it on my local roads , a lot cleaner. LOL...
Since I had the K27HF on I had a chance to compare both turbo's with my EFI conversion. Well, no comparison. With EFI the GT35R blows the K27HF away. Spools up so much faster, much smoother pull. In my book night and day.
Now before EFI, when I was CIS, I loved the k27HF. My opinion with CIS the K27HF with SC cams is the best set up for street car. I went 964 cams and for street driving I like the SC better. Then I went to the GT35 on CIS and even thou it was better than the K27HF, I did not think it was worth the money for a CIS car. Then I EFI the car. The car is wild fire with 964 cams and GT35. I have not driven other EFI cars to compare. I should not say that, my friend had a EFI 930 with Halteck but the car ran like SH-T, so I dont want to use that as a comparison. If I were to stay CIS. SC cams and K27HF. Great set up....
John

Tippy · 04-12-2015, 08:25 AM

Great feedback, John. And good to hear no issues either.

RarlyL8 · RarlyL8's Garage

It is good that you were able to compare not only the turbos but CIS vs EFI vs cams with the same turbos.
We find the same to be true, the setups are completely different and require different turbos for more optimum performance. The GT35 is a bigger turbo than the K27HF which can be taken advantage of with EFI. The most WHP I have seen personally using a K27HF was 505WHP, but no other turbo was used to compare with that setup.
We now use K27/K29 hybrids on high HP CIS engines and find them to be at least equal to the K27HF if not a tad bigger on the top end. The most important thing is to size the turbo to the engine and expected power curve, no matter what brand you prefer.

LOWFAT · 04-13-2015, 06:25 AM

Thanks for the info since I'm in the market for a turbo right now anyway. I was highly considering the gt35 and the was pretty much set on that but now it looks like the old k27 is back in the running. My car is cis with sc cams etc. I currently have a standard k27 that's undersized for my set up. It runs out of breath at 5500 rpm and I'm ready for more punch!!!!!

Tippy · 08:13 AM

Why the hell would you consider the K27?

You like laggier, less power turbos? No offense to current K27 users.

It's not just the fact the GT35 flows more air (worry of CIS owners), the REDUCED BACKPRESSURE of the GT35R is freeing up parasitic horsepower (more power WITHOUT needing ADDITIONAL fuel).

RarlyL8 · RarlyL8's Garage

The K27 series was used by Porsche for the 930 and 965 and are for all practical purposes plug and play. This is important for many. The performance differences are minor on stockish CIS engines. The K27 series turbos are also bullet proof, often exceeding 100,000 miles of service.

Tippy · 04-13-2015, 09:55 AM

Quote:

The K27 series was used by Porsche for the 930 and 965 and are for all practical purposes plug and play. This is important for many. The performance differences are minor on stockish CIS engines. The K27 series turbos are also bullet proof, often exceeding 100,000 miles of service.

I know Brian, just joshin'.

But, you can get the GT35 journal-bearing a lot cheaper and I'd imagine the longevity would be right up there with the K27.

RarlyL8 · RarlyL8's Garage

Porsche used KKK made in Germany, not Garrett made in Mexico.

jbrown · 12:01 PM

Quote:

Originally Posted by LOWFAT

Thanks for the info since I'm in the market for a turbo right now anyway. I was highly considering the gt35 and the was pretty much set on that but now it looks like the old k27 is back in the running. My car is cis with sc cams etc. I currently have a standard k27 that's undersized for my set up. It runs out of breath at 5500 rpm and I'm ready for more punch!!!!!

If you are interested I am selling my K27HF. Great turbo to match up with what you have. Can save you some money....
For more punch up top you have to change your cams to 964. I was like you and went to 964 cams. I dont think the turbo alone will help you up top.
Again the difference was only if you want to rev the care past 6000 rpms. With the sc cams the power cam on a little earlier. With the GT turbo and EFI it spools so fast so you get the best of both worlds.

jbrown · 11:58 AM

KKK are great turbos. Definitly a great match for CIS. I agree with rarlyl8, bullet proof. If I had to pick between the GT35 or K27HF , HFS and I was staying CIS. I would go with the KKK turbo. It worked so go for years for me. EFI I am really happy with the GT, I hope I get the longevity out of it. I do let it cool down before I turn the car off . The only time I did that with the KKK is after a hard run. casual driving I would turn it right off and never had a problem in 8 yrs..

LOWFAT · 04-13-2015, 12:09 PM

Shoot me a pm with info. Thanks

Jimmy18E · 04-13-2015, 12:20 PM

If you like the 964 cam for the bit more top end you get, try the 993SS cams. I'm making power to 7000 RPM with a K27/29. It about as much cam you can go with a CIS car.
Jimmy

fredmeister · fredmeister's Garage

Quote:

Originally Posted by LOWFAT

Thanks for the info since I'm in the market for a turbo right now anyway. I was highly considering the gt35 and the was pretty much set on that but now it looks like the old k27 is back in the running. My car is cis with sc cams etc. I currently have a standard k27 that's undersized for my set up. It runs out of breath at 5500 rpm and I'm ready for more punch!!!!!

I was interested in asking you what the symptoms were that you saw when the turbo was running out of steam. Did you notice a distinct drop in power, did your AF ratios change suddenly, or did the boost drop off suddenly? Looking for specific tell tale signs that I could monitor while driving to indicate that it might be happening to me. You know, using a boost gage and AF ratio gage for example.

I have a k27S turbo in my 930 with some major upgrades and according to compressor maps that I have found regarding the k27 turbo's limits I might be at its limits as well.

thanks for any input,

Tippy · 04-13-2015, 01:38 PM

I have a turbo that can blow the jugs right off my 3.4 (Borg Warner S366 good to 830hp), and the sign is simply hp drop off past a given RPM.

In my case with Carrera 3.2 cams (same specs as SC), hp drop beyond 6K in higher gears.

Tippy · 04-13-2015, 01:39 PM

Quote:

If you like the 964 cam for the bit more top end you get, try the 993SS cams. I'm making power to 7000 RPM with a K27/29. It about as much cam you can go with a CIS car.

Jimmy

Did you relieve the pistons to clear the valves? Change valve springs for higher spring rate over stock?

RarlyL8 · RarlyL8's Garage

993SS do not require piston relief. I'm using these on the Evil Engine build and did add bigger springs as the redline will be stretched to 7200rpm.
We did see the K27-7200 hang on a bit longer, from 5500rpm to 6300rpm, before dropping off when my headers were added to our test engine.

Jimmy18E · 04-13-2015, 04:42 PM

Tippy... It is a full on build, xtreme did the heads , Ti retainers , springs, etc and the Pistons are JE that needed a Little work for the valves to clear.

Jimmy18E · 04-13-2015, 04:48 PM

I just saw Brian's post. I know my Pistons needed work, I' will check with the shop tomorrow. We did end up going with 7:65.1 compression ( measured), that might be the reason

Tippy · 04-13-2015, 07:27 PM

Ah ok. Thanks Brian and Jimmy.

fredmeister · fredmeister's Garage

Quote:

Originally Posted by Tippy

I have a turbo that can blow the jugs right off my 3.4 (Borg Warner S366 good to 830hp), and the sign is simply hp drop off past a given RPM.

In my case with Carrera 3.2 cams (same specs as SC), hp drop beyond 6K in higher gears.

That's ok but I was looking for indicators that don't require a dyno.

I have not dyno-ed my car yet, I do all my tuning on the road and at track days. So I was looking for signs that I could monitor thru seat of the pants and my boost gage and AF meter. I don't notice a drop in power above 6000rpm, the beast pulls hard there.

thanks,
Fred