Will Garrett GT35r work in air cooled 930 motor

[TurboKraft]

The bummer about the Garrett offerings is that they don't have many non-wastegated turbine housings in D5 or cast stainless.

True, stainless direct from Garrett would be nice, like the sexy Tial v-band turbine housings. Or better, the Inconel housings of the ultra-cool TR30R (Audi R8 Le Mans turbos). Garrett uses high-nickel content "Ni-Resist" alloy for their GT-series ball bearing turbos. Not a metalurgist, but it seems incredibly tough and withstands the EGTs of these air-cooled engines (and EGTs of rotary engines, also notoriously hard on exhaust parts).

So when somebody makes a "hybrid" turbo by screwing a compressor to a turbine, to me it is like a house painter retouching the Sistine Chapel ceiling.

Another factor is the rotational inertia of the rotor (Compressor + Turbine + Shaft + thrust bearing). The higher this is, the harder it is for the turbo to spool up. I think you will find that newer turbo's have much lower (30% lower) than turbo's from the '80's. That is what 25 years of computational fluid dynamics buys you.

Couldn't have said it better.
Long story short, the engineers at Garrett (and BorgWarner, etc.) have the tools to refine their products very well before putting them into production. They don't match one compressor wheel to a different turbine wheel by chance or accident. They look at the airflow characteristics and inertia of the components and put together the best combinations. Rarely will you find a manufacturer's turbo with a compressor wheel that radically out-flows the turbine wheel, as you often find in the aftermarket. (And these are usually targeted for small displacement, high boost, high HP engines that also run massive wastegates to make up for the lack of turbine flow.)
That's not a 930 engine's m.o.

One result of this mis-matching is higher exhaust backpressure at the turbine inlet (header) flange. 930s are bad enough, and the long, undersized tube feeding the wastegate on most aftermarket headers doesn't help matters, either.
Anyone else have exhaust backpressure data they would like to share?
We just dyno tuned an ex-Ruf 3.4L that had been in storage for many, many years. Another shop converted it to EFI and "600hp" -- not with a K29-7006#13, buddy! At 17.2psi boost in the manifold, the exhaust backpressure was just a hair under 30psi. About a 1.75:1 pressure ratio (backpressure:boost) despite the larger #13 turbine housing. Car is choking on the backpressure, spooling up slowly, keeping the Group B cams from doing their work.
One of the most responsive EFI 1994 Turbo 3.6s we have built had 2 different large ball bearing turbos. The first had a 1.4:1 backpressure ratio and drove great. The next turbo we used had a lower 1.2:1 ratio from a significantly larger turbine wheel -- and it spooled up even sooner than the smaller turbo!

The reason no one looks at a turbine map is that it's really trivial for the end user to do so. The end [user?]sizes the unit using a/r ratio, trim and max speed of the turbine at a desired compressor output (which conveniently appears on the compressor map). Looking at the map that you posted, what could we understand that those three things don't already tell us or how that map overlays a compressor map?
Only guys like you use turbine maps to impress people at parties and on forums.

Have to disagree. We use the turbine maps a great deal in making an initial turbocharger selection on a new engine combination. If you know the cfm flow of the engine, you better have the exhaust flow to match otherwise you get choked with backpressure into the turbo. Sure, we might make a change after initial dynos, like a different A/R turbine housing to tailor the power band for how the client will use the car. But this turbine flow data is very useful in selecting the closest match the first time around.

Now... Garrett GT35R guys with CIS- How much boost can you run before the CIS runs out of steam?

So far, on a <8.0:1 3.4L, we're done at 0.75bar because AFR is approx. 12.5:1. On this west coast pump junk they call 91-octane, we'd rather be conservative and keep it just richer than 12:1.


What's the most power anyone has made from a K27?

The most I've ever seen was 455hp from a 930, and that was on MODE's (Holcombe's) engine dyno. 3.5L 930 with all usual bolt-ons and cams, and a K27-7006. It made the same power at 1.1bar as at 0.9bar -- 455hp -- only at lower rpms as boost was raised. End of the turbo, turn the boost back down, no point raising boost when the turbo is out of air.

[RarlyL8]

What's the most power anyone has made from a K27?

The K27HF-2 can suport 600HP @ 1.4bar past typical redline. A client had a K27HFS on an EFI car that went 500HP.
The stock 7006 is an old turbo and comares in no way. You can get 400HP out of a 7200. Much depends on how the engine is built or set up, then when the turbo runs out of air.

[Speedy Squirrel]

I can't believe how many Excellece Magazine bikini models have PM"d me since I posted that turbine map. Who would have guessed!

Quote de Speedy Squirrel

What people on this board don't seem to realize is that there is also a turbine map. The turbine map depicts the turbine efficiency vs a mass flow parameter and the expansion ratio. It get a little more complicated because there is a range of efficiencies for a given shaft speed. The compressor is carefully matched to the turbine so that the turbine produces the best possible efficiency for a given mass flow and expansion ratio.

The reason no one looks at a turbine map is that it's really trivial for the end user to do so. The end sizes the unit using a/r ratio, trim and max speed of the turbine at a desired compressor output (which conveniently appears on the compressor map). Looking at the map that you posted, what could we understand that those three things don't already tell us or how that map overlays a compressor map?

Only guys like you use turbine maps to impress people at parties and on forums.

[turbobrat930]

Originally Posted by Speedy Squirrel

I can't believe how many Excellece Magazine bikini models have PM"d me since I posted that turbine map. Who would have guessed!

Well Played, my friend, well played!!!

[hobieboy]

Originally Posted by TurboKraft

One result of this mis-matching is higher exhaust backpressure at the turbine inlet (header) flange. 930s are bad enough, and the long, undersized tube feeding the wastegate on most aftermarket headers doesn't help matters, either.
Anyone else have exhaust backpressure data they would like to share?
We just dyno tuned an ex-Ruf 3.4L that had been in storage for many, many years. Another shop converted it to EFI and "600hp" -- not with a K29-7006#13, buddy! At 17.2psi boost in the manifold, the exhaust backpressure was just a hair under 30psi. About a 1.75:1 pressure ratio (backpressure:boost) despite the larger #13 turbine housing. Car is choking on the backpressure, spooling up slowly, keeping the Group B cams from doing their work.

Perhaps a little off topic but I'm curious...

Would a larger diameter header (say from the standard 1 5/8" to 1 3/4") help to reduce the backpressure? Or is it something else?

thanks!

[beepbeep]

Originally Posted by hobieboy

Perhaps a little off topic but I'm curious...

Would a larger diameter header (say from the standard 1 5/8" to 1 3/4") help to reduce the backpressure? Or is it something else?

thanks!

Majority of backpressure comes from the fact that exhaust gases must pass trough lot's of little blades which are "braked" by big fan which pumps the air into engine. Header and exhaust contribute only slightly...

Too big headers would probably only increase the lag as you would loose pulse energy in exhaust gases and only feed turbo with pressure delta.

[TurboKraft]

Hi Goran,
That's very true, the turbine blades are the major cause of backpressure.
But I have also seen modified engines wake up and become more responsive, more powerful when removing headers with little 1.5" OD primary pipes and going with larger 1.625" or 1.75" primaries and larger secondary pipes.
On a mostly stock engine, or something <400hp, I don't think the big 1.75" headers make sense, no.

[WinRice]

Originally Posted by TurboKraft

We use the turbine maps a great deal in making an initial turbocharger selection on a new engine combination. If you know the cfm flow of the engine, you better have the exhaust flow to match otherwise you get choked with backpressure into the turbo. Sure, we might make a change after initial dynos, like a different A/R turbine housing to tailor the power band for how the client will use the car. But this turbine flow data is very useful in selecting the closest match the first time around.

Chris,

Out of curiousity, do you have a rough rule of thumb of what frame size Garrett to use on which 930 engine combination? For example:

GT35r 450RWHP-550RWHP
GT40r 550RWHP-650RWHP
GT42r ? -?

[NathanUK]

I have always wondered about back pressure with the K27HFS due to the larger compressor side vs the hot side.
I have always wondered if the fact that because the K27HFS turbo will make more volume of air from the cold side (compared to a standard K27) at say 6000RPM (or a given amount of flow through the turbine) this would therefore mean that because the wastegate would need to be open further that this would reduce backpressure just before the hot side more than it would for a standard K27?

Did I get this wrong apart from the WG having to be open further/longer/more often?

[911st]

I wish we would start checking the back pressure with different turbos. This is such a basic concept.

This post talks about ballanceing the hot and cold side and suggests that there is significant opertunity on the hot side. And that it is not alwas a small turbine that makes for the quickest boost. Nor is it the bigest that makes the most HP.

Originally Posted by TurboKraft

...Long story short, the engineers at Garrett (and BorgWarner, etc.) have the tools to refine their products very well before putting them into production. They don't match one compressor wheel to a different turbine wheel by chance or accident. They look at the airflow characteristics and inertia of the components and put together the best combinations. Rarely will you find a manufacturer's turbo with a compressor wheel that radically out-flows the turbine wheel, as you often find in the aftermarket. (And these are usually targeted for small displacement, high boost, high HP engines that also run massive wastegates to make up for the lack of turbine flow.)
That's not a 930 engine's m.o.

One result of this mis-matching is higher exhaust backpressure at the turbine inlet (header) flange. 930s are bad enough, and the long, undersized tube feeding the wastegate on most aftermarket headers doesn't help matters, either.
Anyone else have exhaust backpressure data they would like to share?
We just dyno tuned an ex-Ruf 3.4L that had been in storage for many, many years. Another shop converted it to EFI and "600hp" -- not with a K29-7006#13, buddy! At 17.2psi boost in the manifold, the exhaust backpressure was just a hair under 30psi. About a 1.75:1 pressure ratio (backpressure:boost) despite the larger #13 turbine housing. Car is choking on the backpressure, spooling up slowly, keeping the Group B cams from doing their work.
One of the most responsive EFI 1994 Turbo 3.6s we have built had 2 different large ball bearing turbos. The first had a 1.4:1 backpressure ratio and drove great. The next turbo we used had a lower 1.2:1 ratio from a significantly larger turbine wheel -- and it spooled up even sooner than the smaller turbo! ...

[TurboKraft]

We'll be datalogging EBP (Exhaust Back Pressure) on each of the EFI 911 Turbos we're working on (3.5L, 3.4L, 3.3L, 3.5L, 3.8L) and can post some data over the coming weeks as the projects hit the dyno.
The turbochargers range between GT35R and GT42R in size.
Sorry, no K27-7200 based turbos in process.

[David]

I’m waking up this old thread since I’m about to embark on a change from a K27HF2 to a GT35 Gen II that I picked up from a fellow turbo enthusiast who had it laying around new in the box and I’m looking for information. Chris at TurboKraft is helping me with a turbo housing and oil restrictor since the good deal turbo didn’t come with that. Good info here on water cooling ports since I didn’t know what to do with them and now I know to leave them open.

I’m not looking for more power, just less lag and hopefully better drive ability. Plus I haven’t done much to my car since I finished the engine rebuild and EFI project over 10 years ago and l’m jonesing for some garage time with the 930!

[s5uewf]

Just as a data point, I have had my TK GT35r in place for several seasons now with no issues and while enjoying much better power delivery than any turbos used in the past. No operational issues at all so far.

[gumba]

2019 turbo choices? So what are some turbo choices for today.
CIS up to 450 h.p.
EFI over 450 h.p.

[TurboKraft]

K27-7200 based:
Upgrade yours to double billet internals -- billet compressor wheel, and very lightweight high-flow turbine wheel.
+ Good for all-out CIS or mild EFI builds.
+ Exact bolt-in fitment because K27-based
- Limited by that turbine housing -- backpressure on 450+hp EFI engines
- Replacement housing parts are practically non-existent. Need a new turbine housing? Good luck, indefinite backorder, if not simply NLA.

Garrett:
The GT35R is still the best all-around turbocharger, more responsive than a K27 and flowing more cfm than CIS will reasonably support, capable of 620whp on EFI engines.
Their new Gen2 GTX3582R has a lighter billet compressor wheel and increased efficiency at our low pressure ratio so finally, the billet wheel is a worthwhile upgrade over the cast wheel.

Also, still highly configurable, ex: different A/R turbine housings, v-band outlet available, T3 or T04 or v-band turbine inlet, etc.

BorgWarner:
So far, the EFR's haven't performed well enough to justify their expense and additional custom fabrication.
Some guys still swear by the S300 series (think Tippy is running that).

[Tippy]

Originally Posted by TurboKraft

BorgWarner:
So far, the EFR's haven't performed well enough to justify their expense and additional custom fabrication.
Some guys still swear by the S300 series (think Tippy is running that).

Yes, the EFR's are pricey! Not worth it.

But, I have the Joe Schmo S-series, the S366 (66mm comp) to be exact. That turbo spools stupidly quick for having a gargantuan turbine (73mm exducer). Some here used the S360's (60mm) but weren't raving about them, so there's that.

The boost recovery is insane on mine. I put a YouTube video showing my idiot light indicating 1 bar on the boost gauge. You can see the light illuminate nearly instantly between shifts.

I think the S362 would be sweet as it's right there in size with a GT35R in compressor size. How quick does the S362 spool compared to the GT35R? Dunno. But, if the GT35R is too far out of reach, the S362 may work as a cheaper alternative.

[gumba]

What about the 7006.

[kevinbodman930]

How do you like the Gtx3584rs?

Originally Posted by TurboKraft

K27-7200 based:
Upgrade yours to double billet internals -- billet compressor wheel, and very lightweight high-flow turbine wheel.
+ Good for all-out CIS or mild EFI builds.
+ Exact bolt-in fitment because K27-based
- Limited by that turbine housing -- backpressure on 450+hp EFI engines
- Replacement housing parts are practically non-existent. Need a new turbine housing? Good luck, indefinite backorder, if not simply NLA.

Garrett:
The GT35R is still the best all-around turbocharger, more responsive than a K27 and flowing more cfm than CIS will reasonably support, capable of 620whp on EFI engines.
Their new Gen2 GTX3582R has a lighter billet compressor wheel and increased efficiency at our low pressure ratio so finally, the billet wheel is a worthwhile upgrade over the cast wheel.

Also, still highly configurable, ex: different A/R turbine housings, v-band outlet available, T3 or T04 or v-band turbine inlet, etc.

BorgWarner:
So far, the EFR's haven't performed well enough to justify their expense and additional custom fabrication.
Some guys still swear by the S300 series (think Tippy is running that).

Sent from my SM-N950U using Tapatalk

[K24madness]

Originally Posted by kevinbodman930

How do you like the Gtx3584rs?

Sent from my SM-N950U using Tapatalk

I think that’s a tough question to answer unless you give more details under which scenario you want that turbo to operate.

HP/Boost targets?
Built vs stock engine?
CIS vs EFI?
Etc

[Dominik 930]

and I'm looking for a old kokeln turbocharger.

You do not have to send it to germany - just to Huntsville Al.
many thanks