SVX tuning

[mrmule]

This may be the wrong place to inquire, but it should at least start my journey off in finding out.

So I think the peak torque curve of the SVX is between 4500 and 6000. I was wondering if there are any widely transferable principles which I could apply to this engine to move the torque curve to the left; i.e. at lower RPMs, by doing something like changing the cams for example (I don't know a great deal about tuning engines) just so the engine doesn't have to be screaming to get to max torque. The 3.27 R&P has moved everything down quite a few RPM, so I'd like to move the engine down a hint to match.

If anyone has ever sent their Subaru conversion to a Subaru tuning specialist post transplant and were happy with the results I'd like to hear from you.

[syncroandy]

Wouldn't it be easier just to use the right R&P for the engine ?

[mrmule]

I knew someone was going to say that. There is no 'right' R&P after you've done a Subaru conversion - well there is now

I dont want the engine screaming away on the motorway if it doesnt need to. It doesnt need much torque to push it along once its already going.

I just want to change the characteristics of the engine for acceleration purposes..

[syncroandy]

Sorry for the smartass reply I'm currently on 225/65R16 with 4.86 diff on my camper with EJ25, and I find it just about right. Some might consider it a bit under-geared, but I prefer the slight bias toward climbing ability and acceleration and using the van heavily loaded. I don't cruise above 65 and there's still plenty of headroom for overtaking.

To your original question, you might want to seek out a Subaru tuning forum, or perhaps try VWKD ?

[mrmule]

Sorry for the smartass reply I'm currently on 225/65R16 with 4.86 diff on my camper with EJ25, and I find it just about right. Some might consider it a bit under-geared, but I prefer the slight bias toward climbing ability and acceleration and using the van heavily loaded. I don't cruise above 65 and there's still plenty of headroom for overtaking.

To your original question, you might want to seek out a Subaru tuning forum, or perhaps try VWKD ?

Already on VWKD.

My tin top is going to be a lot lighter than yours. I'm kinda building it to be a motorway mile muncher. Plus I am running 255/40 17 which are 9% smaller than yours. So although not the same, the disparity is smaller than it first appears. I suspect the performance arent that far removed from each other.

I just want the torque to come in sooner, thus matching the R&P.

So is it possible to change the traits of the torque curve the way I am proposing?

[faggie]

just get your gearbox rebuilt by people who can build t3 boxes to cope at motorway speeds ie bears motorsport

[silverbullet]

Might be an idea to mention that it's an auto running a custom ring and pinion set eh?

Here's a p/t graph of a lightly modded EG33, I searched for "subaru svx eg33 power graph":

http://efilogics.com/dyno/graph.php?gb= ... =000000255" onclick="window.open(this.href);return false;

Hmmm...look at this little puppy:

http://t0.gstatic.com/images?q=tbn:ANd9 ... p-laZ4jb6Q" onclick="window.open(this.href);return false;

[mrmule]

Might be an idea to mention that it's an auto running a custom ring and pinion set eh?

Why? I just wanna bring the torque curve to the left. Nothing to do with the trans.

Here's a p/t graph of a lightly modded EG33, I searched for "subaru svx eg33 power graph":

http://efilogics.com/dyno/graph.php?gb= ... =000000255" onclick="window.open(this.href);return false;

I can't make out the numbers on any of the 3 axis. My just be the ipone!

Hmmm...look at this little puppy:

http://t0.gstatic.com/images?q=tbn:ANd9 ... p-laZ4jb6Q" onclick="window.open(this.href);return false;

Chintzy!

[silverbullet]

OK, finding it hard to find a standard power/torque graph so in the meantime, Specs from SubaruSVX.com:

Displacement: 3.3 liter / 3318 cc / 202.5 cubic inches
Bore and Stroke: 96.9 mm x 75 mm / 3.815 inches x 2.95 inches
Compression Ratio: 10.0:1
Horsepower: 230 @ 5,400 rpm
Torque: 228 @ 4,400 rpm
Maximum Engine Speed: 7,000 rpm

(Automatic) Gear Ratios:
Gear Ratio Overall Ratio (rpm) mph
1st 2.79:1 9.90:1 (6400) 43
2nd 1.55:1 5.50:1 (6200) 76
3rd 1.00:1 3.55:1 (6200) 118
4th 0.64:1 2.27:1 (4890) 143
Final Drive Ratio: 3.55:1
Rpm @ 60 mph in 4th: 2050

Reads to me like it was meant to be revvy, not a torque monster. It wasn't particulary high-geared even in the SVX, so your taller 3.27 diff might have over-geared it for the bulk of the bus.

Scoobs do like to sing, just like a wbx

Short of a stroker crank, about the only thing that might improve the low-end torque would be exhaust headers with optimized runners i.e. quite a bit longer. But not easy to cram it all in without getting creative...

[mrmule]

Cheers Ian.

Seeing at the curb weightof the tin top is approx the same as the SVX (1600kgs) I'd say we're comparing evenly.

I know the scooby engines like to rev, but at 60mph I'm around 3300rpm, which will be producing a lot more torque than the SVX box would have dictated at the same speed

Rpm @ 60 mph in 4th: 2050

So arguably I'm a lot better off anyway

I've dropped the rpms by about 800 with my ring and pinion at 60-70mph (was 4100rpm with slightly undersized tyres), which is no where near enough to have put me in 'boging down' territory. If I had the stock 4.09 final drive ratio, I'd be producing close to max torque at average motorway speeds (4100rpm), essentially meaning I'd have no grunt in reserve for overtaking, or gradients, or just going faster etc.

So you see, with the SVX, I actually could drop the ratio even more; perhaps something like a 3.0 or even 2.8 and still get away with it!! All I gotta do is shift down a gear if I need the power in any case.

Sooooo, its not absolutely necessary, but I just wondered if there were any simple mods to bring the torque in a little earlier. I'm looking at Haywoood and Scott to make a custom exhaust, so will have a chat with them about the headers, thanks Ian.

[silverbullet]

The SVX coupe is a tad more aerodynamic than the bus though Frontal area at 60 is definitely a factor here!

Of course you've got the VW 3-speed auto, so no "overdrive" 4th gear. Did Porsche make auto 911's? They would have nice tall diffs...60mph at 3300 is basically the same as my 2.6 or an AAP equipped bus on standard tyre sizes.
You tyres are quite a long way undersize at 9%, I had 255/40/17 on the back of the Bullet and it was quite a nice change to go up to 45 section. Made all the difference.

Haywood and Scott, very nice work. Thickwall tube as well, so quieter than most! My friend is the Austrian agent for them Long headers with silencers over the top of the gearbox could be the way forward.

Like this? http://www.haywardandscott.com/porsche/ ... ystem.html" onclick="window.open(this.href);return false;

[faggie]

i am running a Aircooled dk box with a modified engine and my revs at 60mph are 2900rpm and there is no way i need to drop down a gear on the motorway or normal roads to overtake in fact i hardly use the gerabox lower ratios when moving as i can actually set of in 4th if i slip the clutch a little

[mrmule]

i am running a Aircooled dk box with a modified engine and my revs at 60mph are 2900rpm and there is no way i need to drop down a gear on the motorway or normal roads to overtake in fact i hardly use the gerabox lower ratios when moving as i can actually set of in 4th if i slip the clutch a little

I suspect I'll be fine with the standard SVX Fag, as you rightly confirmed with your WBX. Although being an auto does change the goal posts a little...

[faggie]

hi i am not running a wbx they dont make enough power