hispanic panic

Looking to build a D series for some endurance races and i was looking to start with the DOHC ZC as the platform for a handful of reasons, one of which was a closer ratio gearbox. Was going to put the Si final in it and call it a day when i looked up other gearing for transmissions like the k series CTR and realized the D series gearing is probably WAY too wide. Assuming a race only build with a fully ported head/manifold and sky high cams, i'd figured 8k to be a reasonable RPM limit that can still make power. With that goal in mind, it looks like the M factory close gear sets are the only reasonable option. And if I go M factory gear sets for the D, the SI gear spacing makes a lot more sense vs the ZC's gear spacing. The only problem i'm mulling over is that the jdm DOHC ZC transmission has an intermediate shaft to help cut down on torque steer. Depending on engine prep, i'd fully expect a built ZC to make anywhere between 160 to 200 wheel depending on how crazy i get with it, i'm just not sure if the intermediate shaft really makes enough of a difference for the added complexity of finding a ZC, gutting an SI tranny, and refitting the ZC tranny just for the theoretical benefit of an intermediate shaft.

Anyone road race a powerful d series and have any input on weather or not the intermediate shaft is worth it?

Kaan

iTrader: (3)

Its my understanding that the "factory" geared D series cars seem to do a lot of 2/3/4 shifting... where the aftermarket cars are doing a lot of 3/4/5 while on track. both seem to be fairly effective... BUT D series stuff is getting harder to come by, specifically shift forks and things.

for the money you are going to spend on the D series stuff (assuming you don't have a huge pile of d series stuff laying around)... IMHO it will be cheaper and more effective to do a non vtec B series build.

dirty19

iTrader: (1)

Id drop an email to James Ornelas at Ghostwerks.
He used to run Gearspeed and Synchrotech shops back in the day.
An Expert at all transmissions honda/acura.
Welcome to Ghostwerks Inc. -

He'll give you the most cost effective information you'll need to make that choice.

hispanic panic

I had considered a b series, But the d series is 100 lb lighter. I know it won't be cost-effective to make power on the d series, but it's hard to say no to 100 lb weight reduction! Especially for endurance racing. Also some series penalize you for engine transplants :/ otherwise I'd go full blown k24 from the CRV. Those blocks are cheap as ***** and weigh the same as a b series

Aquafina

iTrader: (3)

If you're going to run an MFactory gear set you don't need to order a DOHC ZC trans unless you want the shorter 2nd gear. You can use a DOHC ZC diff and intermediate shaft in any D trans, which is why I had MFactory make the DOHC ZC helical LSD. The main benefit of the ZC trans (performance aside) is the shift forks are usually well within the wear limits.

I've run just about every trans setup possible for the D series and the MFactory close gear set and OEM 4.058 FD has been my favorite on track.

That said, you can also run MTM gears. They are custom made so you can tailor the ratios however you want them (there are 184 ratios to choose from).

Dilbones

I think we all need more info from you such as:

1.) What series/class
2.) What are rule sets
3.) What car

Couple of things based on what I read:

The people I know that race endurance with Hondas do well with non-VTEC B Series such as the B18B1 and B20. Specifically in the slowest class in AER. The reason for this, partially, is the cars are light (because Honda) and the engines are more reliable than the VTEC motors.

With that being said, a "race only build...[with] sky high cams" doesn't sound all that reliable as the motor is now higher strung.

Gearing is track-dependent. Optimal corner exit/straightaway speed at the Glen vs. Lime Rock is likely different, for example.

Why are you worried about torque steer? Honda Challenge H2 cars run B18C5 motors all day long at ~180 HP and have no issues with torque steer. You're not launching the car from a dig, you're road racing. I'm not sure I understand the concern here...so assuming what you say about the intermediate shaft is true about "controlling torque steer" I would say it's not worth the additional hassle.

I know several people who have raced and still do race with a single cam D Series. SCCA guys will do mild builds like a bottom-end refresh with a bump in compression, maybe some cams, and a mild port job. They typically run lighter cars like the CRX or the EG Civic. With that setup, you essentially get an EX or Si trans and change the final and put a diff in it.

I used to drive a D15B7 which was by no means fast, but was extremely reliable. If I have any advice for you with regard to building a trans for a D Series, it would be to look at the tracks you're racing and see what the most applicable final drive is. Choose that and then put a clutch plate in and send it.

Kaan

iTrader: (3)

at 188hp/138tq I cant say I have it (standing starts and all the corner exits)... but open vs. gear vs. plate diff... the car will feel completely different. when I ran a gear and when my plates started going, it will feel weird (tq steer ish) when exiting.

hispanic panic

Oh wow, the options!!

As far as shift forks, you mean the ZC forks are just newer and have less wear? Or are they beefier? Do you think having an intermediate shaft is necessary or worth it with a diff installed? I assume the 4.25 FD from the SI is too high for the M factory close gear set? I wondered about topping out 5th on some race tracks, i'd wonder if you'd run into any issues with that on a large track like COTA pushing nearly 200 hp in a 1800 lb car.

I haven't even gotten to figuring out the diff yet, I was leaning towards a clutch pack 1 way, or a 1.5 way with the decell side set to minimum engagement. I'm very much against the idea of running a 1.5 way in any differential due to the increase in understeer, but understand honda's need help in preventing inside wheel lockup during braking. I haven't fully fleshed out that side of things yet. Care to share your experiences/thoughts, and why you chose helical?

Aquafina

iTrader: (3)

The ZC transmissions generally have less use on them so the parts are less worn. The forks are the same as all other L3 forks. I'm not sure if there is a performance advantage on track with the intermediate shaft. I had MFactory make it so the DOHC ZC guys wouldn't have to change axles, and for the high powered drag guys to have beefier axles. Top speed depends on your rev limit and tire size. The fastest track I ran at was VIR Full and I didn't top out (was gear limited to 122mph). That was in a 99whp 2,340lb car. If it had decent power and less weight it would have been on the limiter on the back straight.

I use a helical in my car because I put a ton of miles on it and never feel like working on it after working on others all day so I didn't want the maintenance that comes with the clutch type. My customers seem to be split on 1.0 vs 1.5. It comes down to the chassis setup and how you drive the car, IMO.