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Crank Pulley List (Price, Weight, Part #'s)


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Just to verify, looks like underdrive part number is P10681B, while light weight regular size is PAJ773BL right?

 

Also I wish we could use tables in the posts, it's a pain to add new entries currently so might switch it to be a screenshot of my spreadsheet or store the data inline.

 

Yes, P10681B. Verified, I bought one. However the B is for Blue. The Red one is P10681R. There is also a Silver version.

 

They also use 58-2703-2LG on their website. They differentiate part numbers, but they are really all the same.:

http://www.obxracingsports.com/products.php?pk=1541

 

I'm NOT sure now the other one is OEM size, it MAY be underdrive too. On the OBX website and Amazon is says it is underdrive. It may be $7 more for the fancier cutout. Someone would have to buy one to know for sure.

Nothing like a race track to find the weak points in man and machine.

"Good Judgement comes from Experience. Experience comes from Bad Judgement"

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  • 8 months later...
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Bumpski!

 

5EAT so no flywheel issues, does underdrive cause charging issues for us?

 

I don't know. It's going to spin the alternator, PS pump, and AC pump slower. If you are sitting in bumper to bumper traffic for 30 minutes that may not work too well.

 

IMHO, I would only use an underdrive pulley on a race car.

Nothing like a race track to find the weak points in man and machine.

"Good Judgement comes from Experience. Experience comes from Bad Judgement"

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  • 1 month later...
Looks like I have that one in the list, with actual weight at 1.30lbs

 

Whoops.

I did find one not on the list: Go Fast Bits. They make both an Underdrive Crank pulley with Alternator and P/S pulleys kit, and a straight oem size lightweight Crank Pulley.

 

http://www.gfb.com.au/products/lightweight-pulley-kits/subaru

 

And their Tech on them: http://www.gfb.com.au/tech/tech-articles/12-lightweight-under-drive-pulley-kit-performance-testing

Edited by Sgt.Gator

Nothing like a race track to find the weak points in man and machine.

"Good Judgement comes from Experience. Experience comes from Bad Judgement"

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I really need to figure out a better way to display the pulleys, weights and sizes, wish there was a table function. Right now I have to manually space them, that's why I haven't added some of the recent mentions.

05 LGT 16G 14psi 290whp/30mpg

12 OBP Stock 130whp/27mpg@87 Oct

00 G20t GT28r 10psi 250whp/36mpg

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I really need to figure out a better way to display the pulleys, weights and sizes, wish there was a table function. Right now I have to manually space them, that's why I haven't added some of the recent mentions.

 

I tried using the Table HTML from another forum I post on but it didn't work.

 

We need to add the ATI Superdamper to the list too.

 

http://www.atiracing.com/products/dampers/charts/dam-subaru.htm

Nothing like a race track to find the weak points in man and machine.

"Good Judgement comes from Experience. Experience comes from Bad Judgement"

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I really need to figure out a better way to display the pulleys, weights and sizes, wish there was a table function. Right now I have to manually space them, that's why I haven't added some of the recent mentions.

 

That's, unfortunately, not available in vBulletin.

 

Alternatively, do you use MS-Excel? Use that to create your table, then save it as a CSV file. Upload that using Manage Attachments. If you have the ability to PDF a regular Excel file, even easier, just upload the PDF.

- Pro amore Dei et patriam et populum -
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That's, unfortunately, not available in vBulletin.

 

Alternatively, do you use MS-Excel? Use that to create your table, then save it as a CSV file. Upload that using Manage Attachments. If you have the ability to PDF a regular Excel file, even easier, just upload the PDF.

 

Might do as a PNG attachment, but then easy updates go out the window. I got a plan, will do it with probably fancy screenshots.

05 LGT 16G 14psi 290whp/30mpg

12 OBP Stock 130whp/27mpg@87 Oct

00 G20t GT28r 10psi 250whp/36mpg

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  • 11 months later...
Why is underdriven bad?

 

Underdrive is potentially only needed if you race/track the car ALL the time and at very high RPMs. Using a underdrive crank pulley reduces the rpms on the ALternator, Power Steering, and A/C (if you haven't removed the A/C in your track car) which extends their life and reliability.

 

It's also useful and the reason I used one if you are running a dry sump pump off a serp belt from the crank. An oem size crank will overdrive the dry sump pump. That's my opinion, others disagree.

 

The problem is that it underdrives your alternator and A/C for street driving RPMs. On a street car it's not a good idea, the OEM folks very carefully spec the size of the drives to work at street rpm levels and long periods of idling rpm.

 

It's funny, I now use the Fluidampr pulley on my race car, the heaviest one on the list! I like it so far, the car drives great. And despite all the folks who say an undamped pulley like all the aftermarket lightweight pulleys do no damage because the Subaru flat 4 is inherently balanced and has such a short crank a damped pulley is not needed; I like having better than the oem damping.

Nothing like a race track to find the weak points in man and machine.

"Good Judgement comes from Experience. Experience comes from Bad Judgement"

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It's funny, I now use the Fluidampr pulley on my race car, the heaviest one on the list! I like it so far, the car drives great. And despite all the folks who say an undamped pulley like all the aftermarket lightweight pulleys do no damage because the Subaru flat 4 is inherently balanced and has such a short crank a damped pulley is not needed; I like having better than the oem damping.

 

I may eventually get one myself, but since I don't race the car I'm less concerned about it.

 

The only car that I've ever seen an underdrive lightweight crank pulley cause funkiness on is my G20 with an SR20VE with cams. The motor could rev to 8k rpm, but with the light weight pulley it felt and sounded odd at 7k rpm. After I installed the stock pulley I could rev it to 8k no problem. Some background, most Nissan SR20's have 8 counterweight cranks, the SR20VE motor has a 4 counterweight crank. Thus it's believed they are are more sensitive to under-damped crank pulleys. I didn't believe it until I saw it myself.

 

Back to the EJ's, I only got the GS pulley because I didn't want the crank pulley to fall apart on me again (my motor already saw one crank pulley failure with the previous owner). If I felt the same oddness or noise that my SR20VE had, I would install stock pulley (or ATI or fluidmpr) and not bother. But since it's been happy from what I can feel/hear I don't mind it.

05 LGT 16G 14psi 290whp/30mpg

12 OBP Stock 130whp/27mpg@87 Oct

00 G20t GT28r 10psi 250whp/36mpg

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I bought both GS and fluidampr when I saw the original pulley starting to fail. I liked both products for craftsmanship but went with the fluidampr for a few reasons.

 

1. The lighter GS didn't feel much different than stock in my auto tragic. After comparing it to a friend's 5mt, I realize that it benefits manuals more.

 

2. I want my original motor to last and the additional dampening from the fluidampr seemed worth the extra cost for added longevity (only time will tell)

 

3. I can tell the fluidampr works, It completely changed the exhaust note. Immediately after starting it up, it idles much smoother and with less lobbing. It somewhat loses the iconic subaru burble at idle...that's the only downside I've found.

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It's actually hard to find an underdrive crank pulley. The OBX was the only one I could find (to make my dry sump pump work better).

 

The biggest advantage I saw to lightweight pulleys is that they make it easier to rev match your downshifts. The heel-toe blip responds faster and if you mis match the revs the engine has less momentum energy for the clutch and drivetrain to overcome when they hook up. In other words if your revs are off a bit when you let the clutch out the engine spins easier to match the driveline speed.

 

Other than that I don't believe a lightweight crank pulley adds any more power to your car.

 

I've had the lightweight ones in both standard and underdrive. Going forward I would not use a lightweight one at all, and an underdrive one unless it needs to drive a serp belt on a dry sump. Otherwise I'll stick with OEM or upgrade to a Fluidampr.

Nothing like a race track to find the weak points in man and machine.

"Good Judgement comes from Experience. Experience comes from Bad Judgement"

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I made no power on crank pulley, I only did for peace of mind.

 

Here is a run that was about an hour apart (time to replace it the pulley while everything is hot). This is on a fairly stock overall car, maybe with my current power levels it would make a bigger difference? I would attribute the slight torque loss to other factors (if I can find these logs I'll verify things like IAT's and Total Timing).

http://i160.photobucket.com/albums/t188/covertrussian/Cars/05%20LGT/Engine/Pulleys/Crank/CrankPulleyStockvsGrimmSpeed.jpg~original

Edited by covertrussian

05 LGT 16G 14psi 290whp/30mpg

12 OBP Stock 130whp/27mpg@87 Oct

00 G20t GT28r 10psi 250whp/36mpg

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I made no power on crank pulley, in fact I lost torque. I only did for peace of mind.

 

Here is a run that was about an hour apart (time to replace it the pulley while everything is hot). This is on a fairly stock overall car, maybe with my current power levels it would make a bigger difference?

 

I'm sure you know this, but a lightweight crank pulley will neither add, nor lose power/torque. The main advantage is of course a slight decrease in time to rev up and down (helpful with rev matching, etc), and to replace or preemptively replace an aging stock pulley which has a potential to separate (sometimes catastrophically).

 

On that VD, even with best intentions, there are enough differences (especially on stock tune, the time to switch to open loop fueling makes me cringe) that you can't really attribute the 5 ft-lb "loss" to the crank pulley. It would be just as valid to say that the crank pulley somehow decreased spool, got rid of the wonky fueling at 4500 rpms, and smoothed out the powerband. But, we can be nearly 100% certain that isn't the case either.

 

Like I said, I know you know this, but I just wanted to clarify for future readers.

 

Chase

Engineering

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You are correct, I went ahead and reworded my post. I did that graph back when I wasn't as good at keeping the variables down. Even though I did my best to replace the crank as fast as possible, ambient temperature dropped 2*F. Coupled with me not checking to make sure IAT's and Total Timing is the same between two runs, and of course stock inaccurate Wideband. If I can dig up those logs I'll do a deeper dive into them.

 

I will have to say that faster rev should increase power, especially with how VD does calculations (how fast RPM increases over time), this is why clutch slips will give you 800hp.

05 LGT 16G 14psi 290whp/30mpg

12 OBP Stock 130whp/27mpg@87 Oct

00 G20t GT28r 10psi 250whp/36mpg

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It is still extremely impressive that it is as close to being an identical pull as it is for Virtual Dyno.

 

And I should clarify that I meant faster free rev (albeit small, but noticeable), as the difference between time to rev when on power is greatly overshadowed by the engine actually making power. The contribution at that point is just too small to notice.

 

Chase

Engineering

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