dyno'ing an SVX

[mbtoloczko]

I'd like to dyno my SVX. There's a performance shop not too far from my home that has a 2wd dyno. I've read in some previous threads that an SVX can be dyno'ed on a 2wd dyno simply by removing a fuse that converts the beast to 2wd. I have no doubt that removing the fuse does this, but is there any chance of damaging the drive train by dyno'ing the thing is this mode?

Thanks!

[Phast SVX]

You cant do that. Even though it seems quite enticing. When you put the fuse in while driving hte car around, your still dragging the rear wheels and diff at the same speed. Being on a Dyno you will not be dragging the diff at the same speed, and will cuase major strain to the tranny. Sorry Find a shop with a dynopack, they are quite plentifull with the new WRX being stateside.
phil

[mbtoloczko]

Originally posted by Phast SVX
You cant do that. Even though it seems quite enticing. When you put the fuse in while driving hte car around, your still dragging the rear wheels and diff at the same speed. Being on a Dyno you will not be dragging the diff at the same speed, and will cuase major strain to the tranny. Sorry Find a shop with a dynopack, they are quite plentifull with the new WRX being stateside.
phil

I'm a bit curious now. What's with all the old threads stating that the tranny in the US SVXes was used specifically so that the SVX could be dyno'ed with a 2wd dyno?

[Phast SVX]

That was the idea, but later our cars are now exempt from certain emmisions tests that require the use of a dyno.....maybe beav or huck can back me up on that but im fairly posotive, no mechanic though
phil

[Beav]

Here in Louisville the emissions testing is a joke, more driven by private enterprise than actual concern for the environment. The program just got the axe and will become null and void next year. Any AWD cars here are only tested for emissions at idle. I think it's more because they didn't want to lay out the extra bucks for four wheel dynos, plus they don't exactly hire rocket scientists to man the test lanes.

That being said, who can say what the true reason for the inclusion of the FWD fuse was? More than likely it was because of California testing requirements. It also helps out when doing alignments and when diagnosing AWD problems.

I doubt that it cause much, if any, damage to the tranny as most dyno sessions are fairly quick. When the fuse is in place some of the oil return from the cooler is diverted and the rear clutches get shorted their full allotment of oil. But, as I said, this is only for a moment or two on the dyno, not the same as driving to grandma's with the fuse in place. If anything did turn belly-up it would more then likely be a result of coincidence.

Here's the real question though: Why bother in the first place? Unless you've done some mods that have real potential for hp increases or need to be measured to make final adjustments, etc., you're just tossing money at something of little value.

I can't see that there would be any problem with dyno'ing the car with the FWD fuse in place. Correct me if I'm wrong, but the basic purpose of that fuse is so the car can be dyno'd on a normal 'mometor......

I'd like to do it to see if after 10 years the car still makes anywhere near what its original claim of 230 hp was..

-adam

Hmm.. I always thought the FWD fuse was for "doing the donut".

[Seraph]

Originally posted by Phast SVX
That was the idea, but later our cars are now exempt from certain emmisions tests that require the use of a dyno.....maybe beav or huck can back me up on that but im fairly posotive, no mechanic though
phil

I just did the emission test. They did not dyno my car. They can't. They only have 2WD dynos at the place I tested. You should have seen the look on the car owners behind me when the guy came up and said it was all done without having to go on the dyno.

[mbtoloczko]

Originally posted by Beav
Here's the real question though: Why bother in the first place? Unless you've done some mods that have real potential for hp increases or need to be measured to make final adjustments, etc., you're just tossing money at something of little value.

I'm planning to do some exhaust mods, and I'd like to see what difference the mods make in the HP/torque. The cost is only $50 for three runs. The $100 it would cost to see the HP gain/loss would be worth it just so I can add a little hard data to all the talk on these forums about HP gains/loses associated with exhaust mods.

So you're sure there would be no damage done by setting the car to fwd mode for a dyno run? $100 is worth it, but $3000 is not. :-)

[oab_au]

Originally posted by mbtoloczko


I'm planning to do some exhaust mods, and I'd like to see what difference the mods make in the HP/torque. The cost is only $50 for three runs. The $100 it would cost to see the HP gain/loss would be worth it just so I can add a little hard data to all the talk on these forums about HP gains/loses associated with exhaust mods.

So you're sure there would be no damage done by setting the car to fwd mode for a dyno run? $100 is worth it, but $3000 is not. :-)

As Phil says there is a difference to running around with the fuse in and running on the dyno. When on the road both sets of transfer clutch plates are running at the same speed, due to the road connection.

On the dyno the drive plates run at the front wheel speed, The driven plates connected to the back wheels are stopped, so there is friction taking place. Just keep the dyno runs short and allow enough time between runs for cooling.

Harvey.

[Beav]

I just tripped over this at the "End Wrench" site:

"Subaru of America, Inc.’s Emissions Defect & Performance Warranties cover only defects in vehicle materials and workmanship, and not resultant vehicle damage
caused by an improper state emission inspection. Subaru Full-Time 4WD and AWD equipped vehicles should never be tested on a single two-wheel dynamometer."

[Trevor]

Do your own testing for free on a same piece of road with a stop watch. Make several runs and make sure all things are equaul. That will not necessarilly be the case when someone else does a dyno check for you for money believe me. I know how they work and how they are worked.

High road speed is not required and a road with a gradiant is a big advantage. Make runs held in a lower gear throughout up to a decided rev. limit and do several. You are not looking for drama and wheel spin. Quite the reverse. If you get consistant readings you can be confident with the results.
You will appreciate that difference in temperature will effect many of the factors involved and the mechanicals should be at normal optimum at each start.

It is appreciiated that you will not be able to impress with a bunch of figures and possibly a printed read out but you will be sure in both your own mind and as of fact that you have comparitive figures which have useful accuracy.

I am becoming aware that many young guys here regard me as a silly old bugger, but I can assure you that I do not put forward advice unless I have been there, done it and proven it, after having been sure of what I was doing in the first place and I do have qualifications. One thing you can be sure of is that advice from Beav or Harvey is without doubt rock solid.

[fait_svx]

I know for a fact that this car does not make 230 horses. There is no such thing as a car that puts out the "stated amout of horses". I bet this car only puts out 150 horses to any given wheel at any given rpm range.

[Landshark]

Originally posted by fait_svx
I know for a fact that this car does not make 230 horses. There is no such thing as a car that puts out the "stated amout of horses". I bet this car only puts out 150 horses to any given wheel at any given rpm range.

230 is the Net hp at the crank. i believe, for automatic transmissions, about 82% of that actually gets to the wheels. so for the SVX you're looking at about 188 hp. does 82% sound right - i'm going from memory?

[Phast SVX]

i remember a dyno chart from the old SVX performance site...errr...grr!! what was it! anyways their best with the slushbox was 179 to the ground...around the same tq.....but now more importantly what was the name of that damn site!!!
phil