The "J" Swap

Had the pleasure of going out to Chuckwalla Raceway today to follow Coz and Nick. Nick in his Radical and Coz in his recently built J powered NSX. Fun day. The J looks amazing in the engine bay. Leaves plenty of room to work on things while the engine is still there. He is running a single turbo with WTA inter-cooler and I really couldn't tell the difference between his exhaust note and mine other than his revs don't go quite as high. AEM Series 2 just like mine too. Good torque and horsepower though. Car was competitive and if he blows it up, not the end of the world. If you are racing, this must be a serious consideration.

Has anyone done the j37?


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Stillsittinlodo27 said:

Has anyone done the j37?


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It's more challenging as even if you get the tranny/axles figured out you would have to deal with canbus/bcm. It'a doable but more work. If I know what I know now I would go with j37 for sure. It was learning experience with my jswap and it was not that bad after all. It's just a lot of time and money..

Stillsittinlodo27 said:

Has anyone done the j37?


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The J37 is really a truck/suv motor in my opinion. It has the longest stroke of the J series motors (96 mm) and also uses FRM (Fiber Reinforced Metal) cylinder liners, which many feel is not favorable for boost and limits your aftermarket piston selection. The J37 is the limit of the J series and even Honda didn't continue to use it.

I really like the rev characteristics of the J32a2, however the J35 seems to be getting the most aftermarket support and the most interchange options with factory parts.

The J32 probably has the highest redline potential and highest horsepower potential. (89 mm bore x 86 mm stroke)
The J35 probably has the highest torque potential. (89 mm bore x 93 mm stroke)

Valhalla said:

Had the pleasure of going out to Chuckwalla Raceway today to follow Coz and Nick. Nick in his Radical and Coz in his recently built J powered NSX. Fun day. The J looks amazing in the engine bay. Leaves plenty of room to work on things while the engine is still there. He is running a single turbo with WTA inter-cooler and I really couldn't tell the difference between his exhaust note and mine other than his revs don't go quite as high. AEM Series 2 just like mine too. Good torque and horsepower though. Car was competitive and if he blows it up, not the end of the world. If you are racing, this must be a serious consideration.

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I and everyone else would love to see video of this! I know Jim doesn’t post much here anymore but when posted here, it stays and is easily google’able.

Jinks said:

I and everyone else would love to see video of this! I know Jim doesn’t post much here anymore but when posted here, it stays and is easily google’able.

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https://youtu.be/qGWOWYeWv38

Not from this past weekend but this is Jim's NSX with a J32a2 and single turbo setup.

Thanks. That sounds nice.

Here is some more footage from Jim with his single turbo J32a2 swap. Enjoy.

https://www.youtube.com/watch?v=89bFHte8PSo&feature=youtu.be

What clutch is Jim running?

Hi Jinks, Jim is running the Exedy dual ceramic clutch.

Velocitized said:

Some people have asked about swapping in the CL/TL Type-S 6 speed manual along with a J-swap so I thought I would post a comparison of the transmission gearing.

View attachment 140534

While the CL/TL Type-S 6 speed might be more highway friendly, 1st gear might be too low.

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I figured out everything with the J trans. I have final drives and close-ratio setups. I am able to gear the thing pretty much however anyone would like while using nothing but OEM gears.
Below is a picture of my close-ratio setup. I used parts from 7 different trans to do it.

Wow that is really cool, do you have a chart of all available ratios?
[MENTION=20050]Velocitized[/MENTION] you need to make a mount kit for using these transmissions too!

Bense said:

I figured out everything with the J trans. I have final drives and close-ratio setups. I am able to gear the thing pretty much however anyone would like while using nothing but OEM gears.
Below is a picture of my close-ratio setup. I used parts from 7 different trans to do it.

Click to expand...

That is really cool.

What do you think the torque limitation would be for this modified transmission? It's known that certain NSX gears are weaker depending if it's a 5 or 6-speed.

Bense said:

I figured out everything with the J trans. I have final drives and close-ratio setups. I am able to gear the thing pretty much however anyone would like while using nothing but OEM gears.
Below is a picture of my close-ratio setup. I used parts from 7 different trans to do it.
View attachment 156469

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Bense, this is very cool. Nice work and thank you.

Like Mac Attack, I am also interested in the power handling comparison between the NSX and J transmissions.

It's going to be equivalent to the 2010-2014 AWD TL and the new K20C turbo.

The center distance is bigger than the nsx type R 5speed, so theoretically stronger.

Is the NSX 6 speed stronger than the NSX 5 speed? You guys would know more about this than me.

Bense, great job!! where does your ratios stockup on below table

I've got two options for 1st & 2nd. One is more traditional, the other has a slightly longer 2nd gear, which is what I prefer.
-------------------------------
1st = 3.625
2nd = 2.115
3rd = 1.529
4th = 1.190
5th = 0.976
6th = 0.848
-------------------------------
1st = 3.933
2nd = 2.037
3rd = 1.529
4th = 1.190
5th = 0.976
6th = 0.848
-------------------------------
Final drive options:
3.286, 3.55, 3.842, 3.9, 4.11

This project took a LOT of energy.

Wow that is awesome!

[MENTION=33689]Bense[/MENTION], is it possible to bolt up the J-trans to the C engine? Might be a better option for those of us looking for a 6-speed, given the scarcity of the OEM trans.

Honcho said:

@Bense, is it possible to bolt up the J-trans to the C engine? Might be a better option for those of us looking for a 6-speed, given the scarcity of the OEM trans.

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I have no clue. I don't have access to an NSX or a C engine.

There's two other options for a longer 6th gear for those that prefer it.
0.735
0.686

Also, my setup is stronger than the normal J-series FWD trans.

Mainshaft comparison, from left to right:
F22 (same size as B-series), K-series, J-series FWD, Big shaft J-series

Honcho said:

[MENTION=33689]Bense[/MENTION], is it possible to bolt up the J-trans to the C engine? Might be a better option for those of us looking for a 6-speed, given the scarcity of the OEM trans.

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From my deduction, it does. But there are a few things to work out:

Clutch + flywheel
Transmission mounts
Shifter cables
Driveshafts

The later 3 has been solved by [MENTION=6927]nsxmugen[/MENTION].

Edit: [MENTION=33689]Bense[/MENTION], your close ratio gears are good, however, the 1-2 shift will be an issue for the NSX as it would drop the engine to a much lower RPM: 8000 RPM in first = 4800 RPM in 2nd

The JDM NSX gears and 6-speed NSX retains RPMs at around 5100 RPM.

I am aware of this. The powerband on the C-series engine is no different than most of the other low-displacement, high revving Honda engines. My spreadsheet has tables calculated for all B/C/D/F/H/J/K-series transmissions, with the exact teeth count for all OEM and aftermarket gears for all gears that have been released globally.

If you want to compare the RPM drop between 1st and 2nd gears, all you need to do is look at the quotient of (2nd/1st). To see where the RPMs fall, multiply that quotient by your shift point (redline). The problem with 1st and 2nd gear on Honda transmissions is that they are integrated into the mainshaft. Unless you create a custom countershaft 1st gear that has a lower tooth count, that is designed to mesh with the gear profile that's machined into the factory mainshaft you must change out the entire mainshaft. ATS made a B-series gear like this, and I got Gear-X to make a D-series gear like this. MFactory now offers a K-series gear like this as well.

The greater the value is of that quotient, the smaller your RPM drop will be.

USDM 91-94 = (1.727/3.071) = 0.562
JDM-R 91-94 = (1.952/3.071) = 0.636
USDM 97-05 = (1.956/3.066) = 0.638
BenseBuilt = (2.115/3.625) = 0.583


I have proposed that a custom mainshaft be made with a (54/19) 1st gear, and a (43/21) 2nd gear
1st = 2.8421
2nd = 2.0476

However, this reaches the point where I do not have the financial means to get those gears manufactured. Please keep in mind that we are talking about a 3-4mph difference between the configuration that I have concocted and the scarce 6speed.

I recalculated my tables for you guys.
Tire size: 255/40/17
Redline: 8000 rpm
Cruise RPM: 80 mph



This is a screenshot from my own spreadsheet that I have setup so that all I have to do is punch in the gear ratios, and everything that I want to know is automatically calculated. Some of these values will be obvious and apparent to you guys. Others will not. I will explain one the less obvious, calculated values are.

Example: NSX USDM 91-94
The 0.5624 to the right of the 1.727 2nd gear is (2nd gear/1st gear). This tells me what the reduction is when shifting from 1st to 2nd gear. Multiply this 0.5624 by the previously defined 8000 rpm and you get the RPM that you will be in after you take 1st gear up to 8000rpm, and then shift. The rest of these values calculated between each gear is calculated (e.g. 0.7122 = (3rd/2nd), or (1.230 / 1.727))

The teal 3365 is the cruising RPM in top gear at the previously defined cruising speed. In this case, 80 mph.

The yellow 2.23995 is the quotient of (2nd/5th) = (1.727 / 0.771). This is a very simple formula that I use to quickly calculate and assess how close the spread is from 2nd to 5th gear. The lower this value is, the closer or 'tighter' your gear spread is across these gears.

In my close-ratio Frankenstein concoctions, I generally try to get this number as low as possible. To do this using OEM gears, I look for the 'tallest' 2nd gear that is available, and I pair it with the shortest 5th gear that I can use. NSX doesn't have as many gearing options, however something like D-series does.

BenseBuilt D-series gearing
1st = 3.083 (custom gear-x gear that I had made)
2nd = 1.762 (1992-1995 Civic cx/dx/lx/vx -- non ex/si)
3rd = 1.259 (1988-1991 Civic dx/lx)
4th = 1.033 (1988-1991 CRX HF 3rd as 4th gear -- can also use 88-91 ZC 4th gear, its same ratio)
5th = 0.878 (1988-1991 JDM ZC)
Fnl = 4.058 (92-00 DX/LX)

This was a 'junk' trans that I pieced together 10 years ago while I was a student using left over parts from transmission builds that I did for other people. I had already made profit from the other parts. While at first glance it may seem like some junk, Frankenstein trans, in several ways it was one of the most optimal setups that I ever ran. Take a look at the (2nd/5th)=2.00493. It had very tight gearing across the 2nd -> 5th spread.

Now, granted I recognize that the crowd here that might be interested in a setup like this is the antithesis of a poor mechanical engineering student that was experimenting with gearing on the Honda D-series platform. However this is the experience that I'm able to bring to the present table, that some may find useful.