924Board.org

TJC · Posted: Wed Mar 02, 2011 9:37 am Post subject: 931 Engine Torque Curve?

First of all I did try the search, but obviously I'm not very good at it!

What I'm trying to find out is simply a plotted torque curve of a basically stock 924 Turbo engine. I know what the peak is, but to see the curve, or at least to know what the torque values are at various RPMs would be very beneficial to me.

I would appreciate any help, even to be pointed in the right direction, in obtaining this information...Thanks!
_________________
'95 BMW 318i/5 ..."Pearl"
'87 Porsche 944 NA... "Liebchen"
'02 Porsche Boxster..."Sunbeam"
'04 BMW X3..."Xander"
Still on the Prowl!

www.ttrs1.com

ideola · Joined: 01 Oct 2004 Posts: 15550 Location: Spring Lake MI

Haven't found an official graph yet, but you might find the following image from this thread interesting, and maybe even useful:

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erstwhile owner of just about every 924 variant ever made

ideola · Joined: 01 Oct 2004 Posts: 15550 Location: Spring Lake MI

Here's another one from this thread:

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erstwhile owner of just about every 924 variant ever made

ideola · Joined: 01 Oct 2004 Posts: 15550 Location: Spring Lake MI

Note to self: archive those dyno plots before they disappear with the rest of the images from those threads.
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erstwhile owner of just about every 924 variant ever made

TJC · Posted: Wed Mar 02, 2011 10:19 am Post subject:

Thanks for that, the second thread with the numerical printout is very helpful. I'm liking the way the chart shows a pretty flat range of torque, all things considered for the type of engine this is.

Ideally for my scenario I'd like to see the turbo spool up a bit quicker and the torque start building earlier even though I would sacrifice horsepower at the top end, but that is one thing that I'm willing to do for this project that I have in mind.

Any more info, thoughts or suggestions?

Thank you!
_________________
'95 BMW 318i/5 ..."Pearl"
'87 Porsche 944 NA... "Liebchen"
'02 Porsche Boxster..."Sunbeam"
'04 BMW X3..."Xander"
Still on the Prowl!

www.ttrs1.com

ideola · Joined: 01 Oct 2004 Posts: 15550 Location: Spring Lake MI

Series 2 hot side, ceramic coat the entire exhaust tract in the engine bay, stock boost, and higher CR (using custom pistons or a thinner Cometic gasket). I can help you sort out the CR if interested.
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erstwhile owner of just about every 924 variant ever made

TJC · Posted: Wed Mar 02, 2011 10:53 am Post subject:

gegge · Joined: 27 Jul 2007 Posts: 1124 Location: Sweden

Stock 924 turbo engine

Be careful raising CR with a #4 turbinehousing if you got a restrictive exhaust with an old cat and mufflers. Especially if you got long rods. Unless you got access to high octance fuel it will ping. Read the selfdestruct article: http://www.924board.org/viewtopic.php?t=34464
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Carl Fredrik Torkildsen

924 turbo -81 Carrera GT RESTOMOD
924 turbo -80 Dolomite De Luxe
924 -85 DP kit, BBS RS, M030 and tuned engine
924s -86 Black on black turbo with Fuchs

ideola · Joined: 01 Oct 2004 Posts: 15550 Location: Spring Lake MI

To clarify on the CR, I was suggesting Euro spec CR (8.5:1) thru the use of custom pistons, or near that figure by reducing head gasket thickness. I'll have to check the numbers, but I believe the last time I calculated it, you can achieve 8.3:1 CR by using stock S2 US pistons (8.0:1) with a .027" Cometic gasket...
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erstwhile owner of just about every 924 variant ever made

TJC · Posted: Thu Mar 03, 2011 5:44 am Post subject:

I'm starting to look at gear ratios vs the torque curves to get an idea where this engine likes to live. Right now with just a cursory lookover it seems to me that for optimum torque, it likes to be in the 2500 to 4500 RPM range...does this seem about right? I'm guessing that it doesn't have much grunt below 2000 RPM given the fairly low 1st gear ratios vis a vis the final drive ratios.

Well, back to plotting and more study...Thanks.
_________________
'95 BMW 318i/5 ..."Pearl"
'87 Porsche 944 NA... "Liebchen"
'02 Porsche Boxster..."Sunbeam"
'04 BMW X3..."Xander"
Still on the Prowl!

www.ttrs1.com

ideola · Joined: 01 Oct 2004 Posts: 15550 Location: Spring Lake MI

This is where the G31 really shines. It shares many components with the 915, and can be setup to just about any arrangement you want, depending on what you're trying to do.

The G31 going into the club sport has a Euro spec R&P with Euro 5th gear to provide a more track friendly setup and slightly closer ratios.

My trans guy is currently setting up the NA version of the snailshell for one of the guys in NZ where we're "scrunching" 2nd, 3rd, and 4th together to provide shorter ratios, and using the original 4th in the place of the 5th gear so he ends up with a usable 5th gear. This is all based on how he wants to run the car.

My point is, I'm now beginning to really appreciate why the G31 was so preferred in the race cars, because it seems to have more available configurations for different track scenarios. One could imagine having different G31's on the shelf suitable to various track configurations...relatively speaking, it's not that hard to swap a trans in and out!
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erstwhile owner of just about every 924 variant ever made

TJC · Posted: Thu Mar 03, 2011 6:39 am Post subject:

Well, I'm afraid I won't be able to use it...you see I'm looking to mate the engine to a VW 091 gearbox...yes the gearbox that is in my, dare I say, Vanagon

.

Hope you weren't drinking or eating something when you read that, sorry if you were...cleaning up keyboards and monitors is a real PITA.

I'm considering a number of paths for an engine conversion and using the 924 Turbo is one of them if I can source the right bits to convert the 091 Bellhousing. Since the 924 engine shares the same bellhousing mount bolt pattern as some Audis and the VW LT35 van, I'm trying to find a source for the South African bellhousing and engine mount bar that was used to install the 5 cylinder Audi engine in the Vanagon there. I believe that the 924 and that engine are from the same family so having those bits would basically be a plug and play as far as mounting the engine is concerned. I also believe that the crankshaft flanges have the same bolt pattern and dimensions so the flywheel/clutch setup should be fairly straightfoward.

Anyway, now you know what I'm up to...probably won't help me anymore

...but that's why I'm trying to glean all of the info I can before jumping in with both feet.

By the way, we only use the Westy sparingly...maybe 1 to 2K miles a year, which is why I'm even considering this swap...along with a 911 engine.
_________________
'95 BMW 318i/5 ..."Pearl"
'87 Porsche 944 NA... "Liebchen"
'02 Porsche Boxster..."Sunbeam"
'04 BMW X3..."Xander"
Still on the Prowl!

www.ttrs1.com

ideola · Joined: 01 Oct 2004 Posts: 15550 Location: Spring Lake MI

Are you kidding?! A 931-powered Vanagon?! That would be sweet!

It's like turning the tables, no?! Love it.
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erstwhile owner of just about every 924 variant ever made

TJC · Posted: Thu Mar 03, 2011 7:31 am Post subject:

WHEW! And here I was worried that this thread would die after I declared my intentions!!!

I just can't see myself going out of the "Family" so to speak with installing a Ford or a Subaru engine in our "Happy Camper" as many other Vanagon owners are doing. I also can't bring myself to rebuild (again) the underpowered engine that's in it now...even though I can get more power out of it. Parts availability, costs, poor heads (major exhaust valve and seat issues) etc, etc, just don't justify the time and expense.

I'm not looking to go racing with this piece, but it would be nice to climb some hills comfortably, and merge into highway traffic without much of a hassle. The 931 torque curve looks decent enough and with the gear ratios available in the 091 trans I think I can take advantage of the engine's power without straining it too much. That's why I'm questioning where this engine's power starts to build and where it is most comfortable running in a cruise and torque building mode. It's been many, many years since I've driven a 931 and frankly I don't remember these particulars...yes, I'm getting old!

I realize that I will be moving a lot more weight and need to overcome some aerodynamics compared to our 924s, but using this engine in stock form has got to be better than a stock 67 HP, 101 ft/lbs Torque lump that's in there now...even a NA would probably best it

.

So, does my earlier comment regarding where the power band lies seem to be fairly correct? Again, I'm concerned with everyday driving...

Thanks!
_________________
'95 BMW 318i/5 ..."Pearl"
'87 Porsche 944 NA... "Liebchen"
'02 Porsche Boxster..."Sunbeam"
'04 BMW X3..."Xander"
Still on the Prowl!

www.ttrs1.com

ideola · Joined: 01 Oct 2004 Posts: 15550 Location: Spring Lake MI

Yes, definitely, on a Series 2 setup, boost comes pretty strong on around 2500 RPM, and you'll be good 'til at least 5500 RPM. Keep in mind, redline on these motors is 6500, so the power band only came down about 500 RPM between S1 and S2 configurations.
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erstwhile owner of just about every 924 variant ever made