turbos and corrected air flow

tsuter · 06:24 AM

Looking at some compressor maps for a possible turbo change.
Anyone want to opine on VEs by RPM for the 3.0 SC with CIS and stock heat exchangers and also with SSIs?
Theoretical Air flow lbs/min:
2500 = 19
3000 = 23
3500 = 26
4000 = 30
4500 = 34
5000 = 37
5500 = 41
6000 = 45

corrected air flow stock = ??
corrected air flow SSI = ??

Thanks

turbo6bar · 12-12-2003, 06:07 AM

Max torque rpm = max VE

I would guess max VE is 90% at best.

I recall a spreadsheet on the Megasquirt forum that takes the HP curve and converts it into VE. Barring an actual dyno run of your engine, that spreadsheet would be your best bet.

Lemme know if you need help.

Jürgen

tsuter · 12-12-2003, 04:20 PM

OK I'll change the question a bit:
You want the fastest possible spool up from 2500-3500 at 5-10 PSI and don't care about HP only TQ. You don't however want to dive into the choke line at 5500 either at 10 PSI max:

So the options:
1. T3/T4E 50 trim .63 AR
2. T3/T4E 50 trim .48 AR
3. T3/T4E 48 trim .50 AR
4. T3/T4B Super S .63AR
Other?
Why?

tbitz · 12-12-2003, 06:04 PM

I've looked into this and I think I came up with the T04E-54 trim as the best fit for the 3.0l 911 engine on mild boost. I'll have to find my notes. This was based on high efficiency at 10psi, and lowest surge line. I think the A/R for the turbine was 0.6. I haven't tried this setup, so take it for what it is worth. These were just educated estimates.

Not sure but, I think I wouldn't go with the hybrid series. The T3 turbine side may choke the engine at high power?

tsuter · 12-13-2003, 08:08 AM

Agree, TO4E in 50, 54, 57 even possibly 60 are possible. I'm just interested in better low end TQ and spool up with a hybrid T3/T4 than a conventional T4. All the new Garrett GTs are mapped for boost well above 10PSI so they seem even worse for lag.
Can't seem to even locate maps for hybrids.

turbo6bar · 12-13-2003, 09:45 AM

Try Tracy Grimm at www.tgfab.com or Ray Hall at http://www.turbofast.com.au/welcome.html

Selecting turbochargers is like a lost art, and the guys who do know turbos sometimes have tight lips.

tsuter · 12-13-2003, 11:02 AM

?? No hybrid maps at those sites. I've used Ray Hall before but their site is a bit dated in terms of turbo technology.

turbo6bar · 12-13-2003, 11:07 AM

Actually, what I meant is contact a vendor for a recommendation. I think you'd be very lucky to find anyone on Pelican who's a turbo specialist. From what I've read, Garrett is very protective of those flow maps.

tbitz · 12-13-2003, 11:26 AM

Tsuter,

Hybrid only means T4 compressor with T3 turbine. I don't believe they are a new generation of compressors. All the compressor maps for T04B/T04E apply to the hybrid T4/T3.

If your talking about maps for the tubine, I haven't seen any. The turbines have much wider dynamic range than compressors do, so there is less variation in turbines, since only a couple of turbines are good for a wide variety of engines.

Note: spool up time can be reduced by reducing the A/R of the turbine housing.

Here is a good spot for compressor maps:
http://not2fast.wryday.com/turbo/maps/

turbo6bar · 12-13-2003, 11:34 AM

tsuter, I hope I didn't come off as a sourpuss. When I was looking at turbochargers, there wasn't a lot of data available to the DIYer.

tsuter · 12-14-2003, 05:55 AM

I was just hoping to find some VE data on airflow for 3.0L SC with stock heat exchangers vs SSIs. The key in selecting a turbo is knowing your airflow and while "theoretical" flow is interesting you really need adjusted flow to use those compressor maps.
I suppose if anyone has managed to put SSIs on a 930 that would also answer the question about any measurable difference (stock to SSI) with a turbo.
Thanks

turbo6bar · 02-05-2004, 01:09 PM

Did you ever choose a turbocharger, tsuter?

I was looking at the T04E 50 trim, and a .58 P-trim was recommended for the turbine side.

Did you consider the K27?
Jürgen

tsuter · 02-05-2004, 01:45 PM

I ended up keeping the Rayjay turbo (for now) and modifying a 4.5" Fabspeed 930 stainless steel muffler.
With the straight out right side and no 180 degree turn back to the left side I dropped my spool RPM from 3900/4000 to about 3200RPM.

A huge difference.

I don't think even SSIs will do much more as it seems the spool limitation was turbo back pressure from the old exhaust doing its 180 turnaround back to the left.

So far I've saved money over a new turbo. We'll see as it gets warmer soon and I can get some more road time.

It just made sense to go after back pressure first and solve that regardless of turbo.

cowtown · 02-05-2004, 01:52 PM

tsuter, I've been looking at doing exactly the same thing with my 930 engine's muffler. Either a straight-through Borla or Dynomax. Do you have any more shots of how yours is mounted and clamped on? I see some welded brackets on the left but can't make out what they are bolted to.
Thanks

tsuter · 02-05-2004, 02:03 PM

I made a custom support bracket. It fastens in the stock 911SC bracket position with two bolts. Visible in the picture below the red lettering. It has an arm that extends to the right with two slots for the straps around the muffler.
The stock left side is the wastegate outlet only now.

turbo6bar · 02-05-2004, 02:15 PM

tsuter, are you saying you don't build any boost until 3200 rpm?

Here's a pdf from Pat Willaims Racing of a stock 3.3CIS engine:
stock 3.3L dyno table

Boost builds before 2500 rpm. I like it.... A lot.

I imagine your SC cams and higher compression should help build boost quickly.

cowtown, you need the 934 zork tube from Fabspeed. Check out the video on their web site. I bet it's loud. The turbo sounds are wicked, though.

Jurgen

tsuter · 02-05-2004, 02:41 PM

Rayjay is close to a T04B so late boost. I was seeing boost from 4000-6000. Now with the new muffler 3200 and up.
But it's still a T04B.
I'll get some real data when it's warmer out. Right now i'm just watching the 3.0# switch open.
Maybe my clock will fail and I can put a boost gauge up in the cockpit.
All I have now is a small mechanical peak and hold in the back ... sometimes.

beepbeep · 02-05-2004, 03:16 PM

There is another trick when it comes to spooling turbos quickly: keep your headers short and isolated!

PV=nRT -> volume of hot gas will be higher the hotter gas is. With other words, the closer to head(s) turbo is the hotter the exhaust gas is and the greater volume flows trough the turbine resulting in boost treshold moved downwards in RPM range.

911's have always had problems with turbo headers beacuse of heat-exchanger peculiarities. 930's are prime example of this horrible constructional compromise: exhaust path between furthest cylinder and turbo is something like 2 meters!

If you take a peek at 935 "headers" you'll notice that there are no matched length primaries, just a bunch of pipes bung-welded together into a thick sewer going into the turbo as soon as possible.

With other words, short headers with good flow will give you more benefits on turbocharged car than long tuned ones.

Unfortunately, this often means getting rid of the heat and fabricating your own headers. Exhaust bandage helps a lot too.

Speaking about turbos, my expirience is that Garrets new GT series is head and shoulders above most (all?) older series as KKK anicient K27, TD04E etc.

I believe GT35 with appropriate housing would give very quick spoolup and good boost.

WydRyd · 02-05-2004, 03:22 PM

Only problem is that they won't last very long on an oil cooled only car. Those turbochargers are designed specifically for water cooled applications.

That's what I've been told by Garrett anyway

tsuter · 02-05-2004, 03:33 PM

The GT series would require water cooling. I've actually considered doing this in the 911 using a VW after run coolant pump and running the coolant thru my AC condensor which is not used.

One step at a time though boys!