I'm planning on a future drivetrain upgrade very soon; I'm basically planning to convert from auto to manual and wish to ask any experts on HT, which tranny dominates in fast acceleration and street performance/track overall?

I understand the American Si tranny dominates in the higher gears and the DX dominates in the first gears but then lags (has take off power, but looses bottom-end power). I wouldn't mind building a hybrid tranny at all, as I've definetly heard and read that switching out some of the first gears of the DX into the Si makes for a well rounded transmission... but I have another question... how does this compare to the Japanese Si (ZC) transmission? I understand it uses a half shaft, right? I would think the ZC transmission is strong, but a lot agree the Si surpasses, true or false? Anyone out there do any research on these?

So the main question is, when compared to the ZC drivetrain, how does it compare with the hybrid Si (DX/Si gear combination) drivetrain?

** Please post any links to threads related to this topic **

 

The DX and SI 1-5 gears are all exactly the same ratio. The difference between the DX and SI that makes the SI that much better is the inclusion of a 4.25 final drive instead of the DX 3.88 final drive.

 

the ZC transmission is not any stronger than any of the others - internally, they are mostly the same - the only difference is in the differential carrier and side gears that accept the larger axles - the ZC 2-5 gears are shorter than the DX/Si gears and the ratios are a little closer together, but the ZC has the same final drive as the DX, 3.88 - in gears 1 thru 3, the Si is shorter than the ZC but in gears 4 and 5, the ZC is shorter than the Si, even with the 3.88 final - the best, as far as pure acceleration, is the ZC 1-5 gears with the Si final drive or with a 4.44 final drive (hard to find) - how all of that relates to performance on the drag strip is a whole different matter - there, it depends on how fast you are running and tire size - for instance, on our drag car we have run all different combinations - at the altitude we run at (5800ft.) the quickest 60ft. times came with ZC 1-5 and 4.44 final drive, however, the quickest 1/4 mile times were with a straight Si transmission - this is due to the fact that with the ZC/4.44, we were having to shift to 4th gear, where with the Si we could run through in 3rd gear - at lower altitude tracks, where we were going faster, the ZC/4.44 was quicker because we were having to shift to 4th even with the Si

 

Sweet. Thanks for the fast reply guys.

I'm really not looking for track performance, but overall, street performance. I want fast acceleration and strong pickup. I'm looking for the factory sport feel.

Humm, so the DX is the same 1-5, but the final drive is the difference, eh? Sometime before, I had heard the 1-2 gears were stronger, humm..

So, stock Si setup would be what I'm looking for as far as a quick pickup? Which car had the 4.44 FD?


Modified by jdm4drSi at 5:28 PM 5/22/2008

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by jdm4drSi &raquo;</TD></TR><TR><TD CLASS="quote"> Which car had the 4.44 FD?</TD></TR></TABLE>90-93 JDM Integra ZXi, RXi, TXi and probably others

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by jlicrx &raquo;</TD></TR><TR><TD CLASS="quote">90-93 JDM Integra ZXi, RXi, TXi and probably others</TD></TR></TABLE>

S-W-E-E-T.

So what setting would you recommend for "factory sport feel" (smooth acceleration, shifting and driveability)?

 

I posted this in a topic that was originally asking about gear ratios, so if it's not 100% relavent sorry. Begin paste:

For comparison's sake here's the actual ratios:

JDM DOHC ZC L3:

1st - 3.250

2nd - 1.944

3rd - 1.346

4th - 1.033

5th - 0.878

Final drive - 3.888

I bolded 5th because that's shorter than a USDM Type R 5th gear ratio!!! Now when you do the math against the 3.88FD it's not too crazy though - you get 3.40.

Now for USDM Si or JDM SOHC ZC L3 ratios:

1st - 3.250

2nd - 1.894

3rd - 1.259

4th - 0.937

5th - 0.771

Final drive - 4.250

I bolded the final drive because it's the best one we got here in a regular 5-speed L3 tranny here. When you multiply the 4.25Fd against the .771 lower 5th gear you get 3.27 - still lower than the DOHC ZC overall 5th gear ratio. This means the USDM 88-91 Si tranny has a slightly lower cruising highway rpm in 5th gear.

So basically acceleration would be in direct correlation with how close each gear is to each other, because the less of a number difference between the gears, the less rpm drops, and the higher each overall gear number ratio is (gear ratio x final drive ratio) the quicker you get to rip through that gear.

Sorry if I'm confusing anyone

I'm going to try and do the math of my custom Zc/Si hybrid tranny where i used ZC 1-4 closer gearing coupled with the Si 5th and 4.25 FD to sow you what I mean. I will simply take each gear ratio and multiply it against the 4.25 FD to get my overall gear ratios per gear.

1st - 13.81 (same as 88-91 Si tranny either way)

2nd - 8.26

3rd - 5.72

4th - 4.39

5th - same 3.27 since I kept the Si 5th gear, but if I had kept the ZC 5th it'd be a ridiculous 3.73!!! That's a huge difference!

Anyways see how close each number is? Like I said the closer the numbers stay together, the quicker you rip through each gear, and thus, the quicker you accelerate.

For comparison's sake I'll do the same math with a regular 88-91 Si tranny that most of us try to get when we do a SOHC build here in the US:

1st - 13.81

2nd - 8.04

3rd - 5.35

4th - 3.98

5th - 3.27

And finally the DOHC Zc with it's shorter gearing, but shitty 3.88 DX-spec FD:

1st - 12.61 (YIKES! Would take longer to go through!)

2nd - 7.54

3rd - 5.22

4th - 4.00

5th - 3.40

So compare the numbers and see the difference? You'll note that the custom Zc/Si tranny has higher numbers, and closer to each other numbers too. This means quicker ripping through gears.

You'll also note that even our regular 88-91 Si tranny has a clear advantage over the JDM DOHC ZC tranny too, because of the taller 3.88 FD they have. The taller FD negates the closer gears.

Does that make sense?

...and another copy paste including an original quote from a guy, so you'll get the reference I make with my reply:

Actually the ZC tranny, if it came from a DOHC ZC has completely different gearing and final drive than the 88-91 Si tranny.

The DOHC ZC tranny has the closest 1-5 gearing than any other SOHC tranny. The "problem" with them is that they also have the DX spec taller 3.88 final drive in them.

The 88-91 Si tranny has longer, more spaced out gearing, but a much better 4.25 final drive in them, so OVERALL after multiplying gears against the final drives the Si tranny is actually SHORTER/BETTER geared than the ZC tranny.

What I have done, and it works out amazingly well, is I took ZC 1-4 gears and stacked them into an Si tranny case with the better Si final drive - but I left the stock Si 5th gear!!! What this gave me was a ultra close, awesome accelerating 1-4 gear ratio, but a stock 88-91 Si 5th gear for highway cruising rpm.

Let me ask you this:

Currently do you have the DOHC ZC tranny complete with the midshaft, or have I gone off on a tangent for nothing? The reason I ask is that the DOHC ZC L3 tranny is 100% different inside than the SOHC L3 ZC tranny.

 

I personally took a little different route.. in my trans i have the SI 1-4 with a CRX hf 5th gear and a Gear-X 4.9 final drive. I am really happy with it, because i get great acceleration in 1-4, and then 5th gear is good on the highway, despite the high final drive.

 

thanks for the reply B18C5 and everyone else whose contributed so far.

I am going to take into account your analysis and weighing it against my own judgement to see which is best.

I really dont want the ZC tranny because of the different spline pattern, and since I'm building brand new EX knuckles (BEYOND DISCONTINUED AND HELLA RARE), I am not going to opt out from them just because of the spline pattern. I want to stick with the EX hub (WHICH IS ALSO WICKEDLY RARE) because I want to preserve my good axles.

So, I might just seize the ZC 1-4 gears and slap them on the Si tranny and keep the 5th + FD on the Si.

 

Arrg. It seems to be so hard to find info on the difference in the differentials between the Std, Si and ZC. Are they all different?

 

In a related note, and also a shameless plug I'll be posting up the built SOHC Si/ZC tranny I built in a day or so. I rebuilt it with all 5 shaft bearings, diff bearings, main shaft seal, and shifter shaft seal a few years ago.

I sold the car the tranny and built 11:1CR D16A6 was attached to, but the new owner opted to swap in a built B series so I'm helping him sell off the goods. He's supposed to stop by today to tell me what prices he wants fro everything.

If anyone cares just check my recent topics (started by me) for the next few days and it should be up along with a complete MPFI conversion with Rywire harness, ECU, etc. etc.



Sorry, shameless plug. Not meant to be a thread jack, but it is related since I've got such a tranny being discussed for sael soon.

 

I'd pick it up if it didn't have the ZC-spec spline pattern, you know?