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Craig 930 RS's Avatar
 
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So you have 1 bar, headers, and a cam of some sort -

Data point:
7.5:1 with 964 cams, .9 bar, Zork, + K27 HF Zero Clearance (specially built turbo) for me = 438 RWHP/413 RWTQ. Using

If you use 1 bar on CIS with a K27 HF/HFS you had better damn well have accurate + more fuel via some means.......
I'd recommend the adjustable WUR + RPM switch and possibly the IA fuel head, if required.
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"930 is the wild slut you sleep with who tries to kill you every time you "get it on" - Quote by Gabe
Movie: 930 on the dyno
Old 08-10-2007, 10:54 AM
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Quote:
Originally Posted by hobieboy View Post
How would the GT35R compares with the 40R for EFI cars?

BTW - I have PM'ed you on another topic...
As I said before, EFI or not EFI, it doesn't matter. It's a matter of mass flow and pressure delta. You can calculate this.

A 3.3L spinning @ 6000 revs and boosting 1.2 bar @ 92% VE and intake temp of 35 deg. C would suck roughly 50lbs/min worth of air and produce around 450hp worth of power assuming certain efficiency (which I assumed from expirience). CIS flapper is nothing else but a "second throttle"...if CIS car produces 450hp it will gulp certain amount of air. If CIS makes it slightly less effective when producing that amount of power, it will need >even more< air+fuel.

Roughly, you take this figure (50lbs/min, 2.2 pressure ratio) and plot it into compressor map. If you are way out of efficiency island, your turbo isn't suitable.

That being said, GT35R 68mm, 56 trim is pretty spot-on for this case, landing in 72% efficiency island,to the right of the middle 79% best-case spot . GT40R is nice too, but suitable only if you are chasing really high power...which brings you back to certain other things (like, will engine handle it).

Here's K27 map (you need to convert kg/s to lbs/min):



Here's GT35R map (red line drawn by me for 1.7 bar application):



Calculate suitable mass flow and pressure ratio, choose A/R that suits your engine, lay out the maps and pick the turbo that suits you best according to your needs the best.

PM me your adress and I'll send you Excel spreadsheet to calculate mass flow if you cannot do it yourself.

Cheers.
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Last edited by beepbeep; 08-10-2007 at 11:50 AM..
Old 08-10-2007, 11:44 AM
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The Gt35r is not "too much" for a CIS car. All you have to do is run less boost to make a bit less power and stay within CIS constraints.

Hobieboy, the Gt40r (gt4088r) has almost the same sized compressor wheel as a 35r, and a larger turbine. It will make more power on the same boost, however it ultimately really doesn't seem to outflow the 35r by too much more. The Gt40r is rated at 700fwhp by Garrett. Though they are conservative, I've seen Gt35r's push 650whp and Gt40r's barely push 700whp. Honestly, if you want to go bigger than a Gt35r, you might consider the Gt4094r which is a new hybrid of a Gt42r compressor and 42r turbine. It's rated at 850fwhp so at least it can make a "bit" more power than a 35r.
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Old 08-10-2007, 11:46 AM
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I plan on using a GT4094R on my 934 replica. Built 3.4 with Individual Throttle Bodies. Should be REAL fun since it will be pushing only ~2400lbs. around.

Cleve
Old 08-10-2007, 02:06 PM
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Angry

ok..... so much for what I've been told.

I guess the PPI should have brought this out, but I didn't think I mentioned that the turbo was a K28 'cheater'

I climbed under the car and this is what I actually have:





so.... the question is, how much can I gain from going to a different turbo?

I have B&B headers, a K&N intake, web regrinds and a tial F40 / 1bar spring wastegate..........
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Old 08-10-2007, 04:41 PM
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Quote:
Originally Posted by beepbeep View Post
Garrett GT35R, hands down. CIS or no CIS, it's just a air-pump. A very efficient one. What matters is mass flow/pressure differential and not what squirts the fuel. Yes, it needs another flange and less oil pressure and a coolant loop but once it's solved it's years ahead of KKK K27-any-letter-you-like......snip
Solving these problems are really the key for most people on this list. If I didn't do the fabrication myself, I could not have afforded to have someone do it for me. Therefore, a GT35r, although superior, would not have been feasible.

That being said, the time I took to fab everything to make the GT35r work was well worth the time/effort.
Old 08-10-2007, 05:34 PM
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Maxx, you've got a pretty decent setup right now. Going to a K27F or like turbo will help out your top end. weather or not it is $1500 worth of improvement is up to you.
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Old 08-10-2007, 07:46 PM
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Quote:
Originally Posted by RarlyL8 View Post
Maxx, you've got a pretty decent setup right now. Going to a K27F or like turbo will help out your top end. weather or not it is $1500 worth of improvement is up to you.
Probably not unless I plan on a lot of other mods as well. Maybe I'll just worry about it later if I have to ever replace this K27 7200.
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Old 08-11-2007, 01:48 AM
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Quote:
Originally Posted by beepbeep View Post
As I said before, EFI or not EFI, it doesn't matter. It's a matter of mass flow and pressure delta. You can calculate this.

A 3.3L spinning @ 6000 revs and boosting 1.2 bar @ 92% VE and intake temp of 35 deg. C would suck roughly 50lbs/min worth of air and produce around 450hp worth of power assuming certain efficiency (which I assumed from expirience). CIS flapper is nothing else but a "second throttle"...if CIS car produces 450hp it will gulp certain amount of air. If CIS makes it slightly less effective when producing that amount of power, it will need >even more< air+fuel.

Roughly, you take this figure (50lbs/min, 2.2 pressure ratio) and plot it into compressor map. If you are way out of efficiency island, your turbo isn't suitable.

That being said, GT35R 68mm, 56 trim is pretty spot-on for this case, landing in 72% efficiency island,to the right of the middle 79% best-case spot . GT40R is nice too, but suitable only if you are chasing really high power...which brings you back to certain other things (like, will engine handle it).

Here's K27 map (you need to convert kg/s to lbs/min):



Here's GT35R map (red line drawn by me for 1.7 bar application):



Calculate suitable mass flow and pressure ratio, choose A/R that suits your engine, lay out the maps and pick the turbo that suits you best according to your needs the best.

PM me your adress and I'll send you Excel spreadsheet to calculate mass flow if you cannot do it yourself.

Cheers.
I found this on the web Is it fairly accurate?
1 KG/sec = 132 lbs/min approx equals 1771.812 CFM

Also, is that K27 map for the 7200?

Thanks Goran.
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Old 08-11-2007, 03:27 AM
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Quote:
Originally Posted by NathanUK View Post
I found this on the web Is it fairly accurate?
1 KG/sec = 132 lbs/min approx equals 1771.812 CFM

Also, is that K27 map for the 7200?

Thanks Goran.
Dunno about the map. It says K27/2, 911 Turbo on the paper. I guess it's standard KKK fitted on 3.6T or such. KKK maps are generally hard to find. Then there is plethora of "tweaked" turbochargers that are nothing but lumps with clipped blades, moving surge limits somewhat upwards but making them even more inefficient.

About conversion...just convert kg to lbs and multiply it with 60 and you'll have the figure
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Old 08-11-2007, 01:58 PM
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That is a 7200 map
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94 3.6Turbo 6-speed AWD
Old 08-11-2007, 02:00 PM
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P.S. Let's not forget that picking the right turbo trough compressor maps doesn't mean that we are looking for turbo where top-power plot ends up in center of max-efficiency island! Such engine would be good on a airplane, but cars rev their engines trough a certain range and you want your turbocharger to perform in optimal fashion troughout the range required by application.

With other words, working point will "wander" trough efficiency plot depending on boost, throttle and revs. A typical turbo would let you go trough max efficiency island where you need the power the most...around 3000 to 4000 revs. It will then wander to the left of the map, but it shouldn't go into overrev or surge limit.

To put it simply: if you pick smaller turbo it will pump more efficiently trough middle-range but start huffing more and more hot air at high revs. As we are not using CVT-gearboxes or are drag-racing with slushboxes, such character isn't always bad.

Highway perspective: my daily driver has a small Mitsu TE05-13b turbocharger. It boosts around 1 bar in middle revs, then tapers down towards 0.6 bar at 6000 revs as it runs out of steam. In this (extreme) case, my power curve is almost flat between 4000 and 6000 RPM. Torque is gradually declining. Engine produces around 220hp. If I drive my car against a N/A engine of similar output, I always run away as this torque allows me to dissipate more power in typical 4000-6000 RPM shift-range than N/A engine would. My "pull" would gradually decline as I climb trough the revs, but each upshift gives me almost same torque in next gear.

So,
For top end power: big turbo=low backpressure=efficient at high revs=less responsive=good for drag-racing
For good compromisse: slightly smaller turbo=efficient at middle revs=responsive=good in most cases
For torque monster=small turbo=high backpressure=monster torque low down=almost instant boost=needs to be boost controlled with boost taper at higher revs in order not to overspeed the turbo.

Hope this clears the choice parameters somewhat.
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Last edited by beepbeep; 08-11-2007 at 03:20 PM..
Old 08-11-2007, 03:16 PM
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Very well said Goran...
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Old 08-11-2007, 03:39 PM
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I'd think the best method might be to choose a robust and proven overall top-to-bottom setup which mimicks what your goals are - then copy it.
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- Craig 3.4L, SC heads, 964 cams, B&B headers, K27 HF ZC turbo, Ruf IC. WUR & RPM switch, IA fuel head, Zork, G50/50 5 speed. 438 RWHP / 413 RWTQ -
"930 is the wild slut you sleep with who tries to kill you every time you "get it on" - Quote by Gabe
Movie: 930 on the dyno
Old 08-11-2007, 03:52 PM
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Quote:
Originally Posted by Craig 930 RS View Post
I'd think the best method might be to choose a robust and proven overall top-to-bottom setup which mimicks what your goals are - then copy it.
This being somewhat obscure hobby and filled with traditionalists to boot, there are not many "proven" setups that fit all diverging goals.

Usually, it defaults to bolting K27 of some sort. That being said, It pays to read on the subject and sometimes even try something different
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Old 08-11-2007, 04:06 PM
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What's a 'diverging goal'?

Anyway, if you have CIS there is definitely a set of tools, parts and methods to make high, reliable HP.
I speak not of turbochargers in general and not even a K27 specifically, but rather empirically the entire engine build - CIS as my posit.

What's a posit?
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- Craig 3.4L, SC heads, 964 cams, B&B headers, K27 HF ZC turbo, Ruf IC. WUR & RPM switch, IA fuel head, Zork, G50/50 5 speed. 438 RWHP / 413 RWTQ -
"930 is the wild slut you sleep with who tries to kill you every time you "get it on" - Quote by Gabe
Movie: 930 on the dyno
Old 08-11-2007, 07:07 PM
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