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Scion FR-S / Toyota 86 GT86 General Forum The place to start for the Scion FR-S / Toyota 86 | GT86


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Old 07-15-2020, 03:00 AM   #85
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Hmm, but $2.3K at japanparts, +shipping/import costs .. imho by such price good clutch type LSD looks better choice.
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Old 07-15-2020, 07:46 AM   #86
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I would say the best reply was given here:

https://www.ft86club.com/forums/show...7&postcount=36
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Old 07-15-2020, 03:05 PM   #87
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That is not completely correct: Torsen doesn't have a lock rate, as it's stucture goes from 0 to 99.9% (if both wheels completely loose traction it will work as an open diff).
GRMN LSD is declared to be a little more "open" on the first phase, to help entering the curve. So I think it has different gears on Torsen leverage, basically related to wider rear wheels of the GRMN.
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Old 07-15-2020, 08:26 PM   #88
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Originally Posted by nikitopo View Post
This was a build to order factory part. Meaning that Toyota Japan took a standard 17+ differential (4.3 FD ratio) and opened it to change the Torsen with the improved one.

Other parts like the GRMN intake manifold are discontinued, so it is much harder to find them.
I know the parts are harder to get. I’m just wondering the real benefit vs cost ratio for the GR unit, which is still Torsen, when better performing clutch types can be had for less.

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Hmm, but $2.3K at japanparts, +shipping/import costs .. imho by such price good clutch type LSD looks better choice.
That’s my thinking. I could get a 17+ OEM 4.3 FD or even a TRD 4.56 FD paired to a OS Giken diff for the same or less. I get the appeal for somebody who may want an OEM solution that’s just a bit better than standard (like OEM+ type of thing), but I have to wonder how noticeable the differences actually are in the real world.

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That is not completely correct: Torsen doesn't have a lock rate, as it's stucture goes from 0 to 99.9% (if both wheels completely loose traction it will work as an open diff).
GRMN LSD is declared to be a little more "open" on the first phase, to help entering the curve. So I think it has different gears on Torsen leverage, basically related to wider rear wheels of the GRMN.
This was my understanding of the GRMN unit too. Between the brakes, fender vents, intake manifold, seats, and so on... I’d try to source any of those before the diff, personally lol
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Old 07-16-2020, 01:51 AM   #89
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Quote:
Originally Posted by gpvecchi View Post
That is not completely correct: Torsen doesn't have a lock rate, as it's stucture goes from 0 to 99.9% (if both wheels completely loose traction it will work as an open diff).
GRMN LSD is declared to be a little more "open" on the first phase, to help entering the curve. So I think it has different gears on Torsen leverage, basically related to wider rear wheels of the GRMN.
It looks that you don't understand the details of how a Torsen differential work. Torsen has a torque bias ratio (TBR) and in the normal case it is a 4:1 rate. This is also called its lock rate, but the better terminology is TBR. So, the diff in the GRMN 86 has a higher TBR. It is close to a 6:1 rate.

You can find more information here: https://torsen.com/ask-torsen-torque...nal-questions/

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This was my understanding of the GRMN unit too. Between the brakes, fender vents, intake manifold, seats, and so on... I’d try to source any of those before the diff, personally lol
I am not trying to build a GRMN 86 replica. I wanted to solve a specific problem I had, caused by bad road pavement conditions. I found that the best option would be to use the specific diff and it works perfectly. Someone might say that an OS Giken diff or other clutch plate would be better, but everyone can have its opinion here. What I can say for sure is that GRMN spent a lot of R&D to build the specific diff and yes it makes a difference. Another thing to know is that Torsen (JTEKT Corporation) is actually owned by Toyota, so they know what they are doing.
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Old 07-16-2020, 09:09 AM   #90
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This is what I said, you were talking of lock rate not torque bias ratio, that's a completely different thing...
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Old 07-16-2020, 12:54 PM   #91
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It looks that you still don't understand, but you are not the first nor the last. GRMN 86 differential has nothing to do with the wider wheels or about being more "open" like you said.
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Old 07-16-2020, 02:59 PM   #92
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Originally Posted by nikitopo View Post
I am not trying to build a GRMN 86 replica. I wanted to solve a specific problem I had, caused by bad road pavement conditions. I found that the best option would be to use the specific diff and it works perfectly. Someone might say that an OS Giken diff or other clutch plate would be better, but everyone can have its opinion here. What I can say for sure is that GRMN spent a lot of R&D to build the specific diff and yes it makes a difference. Another thing to know is that Torsen (JTEKT Corporation) is actually owned by Toyota, so they know what they are doing.
I’m not saying you’re building a replica; I was just saying that I would personally be more interested in some of the other items compared to the diff, because of reasons stated earlier.

But as you mentioned, the GRMN unit works best for you and the specific problem you had. That’s fine. If it works, it works.
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Old 08-04-2020, 06:59 AM   #93
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Originally Posted by ck20090418 View Post
My grmn build, bonnet next
Jesus, how much was the manifold?

Sent from my CPH1979 using Tapatalk
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Old 08-04-2020, 07:07 AM   #94
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Nice!
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Old 08-04-2020, 09:41 AM   #95
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Jesus, how much was the manifold?

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Just a little bit extra compare to the red aluminium manifold

But Some work need to be done to make it run correctly

Otherwise aftermarket ecu can bypass some sensor to activate the throttle plate inside to switch the long runner or short runner
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Old 08-04-2020, 12:34 PM   #96
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Short length runners are for high rpm power and long length runners for mid rpm torque. This is a high quality factory spec'd intake manifold for getting a wider torque curve from this engine .
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Old 08-04-2020, 11:27 PM   #97
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Awww where did the post go for the cool manifold??
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Old 08-04-2020, 11:35 PM   #98
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Originally Posted by nikitopo View Post
Short length runners are for high rpm power and long length runners for mid rpm torque. This is a high quality factory spec'd intake manifold for getting a wider torque curve from this engine .
it use a vacuum hose connect to the airbox and a vacuum pump to open up the throttle plate for stock setup.

still figure it out a how to run it properly if i use motec ecu
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