Got a question for those running a stock GS-R tranny w. stock rev-limit. What revs are you getting when you shift from 1st to 2nd and 2nd to 3rd. From 8000 to xxxx rpms on upshifts? I'm trying to build a short gear tranny, and looking for info on GS-R shift points. Thanks!

-steve

 

most people who want shorter gears get a B16/ITR tranny..shorter? JDM ITR...but ill try to get those nubers for you...


[Modified by 10K2HVN, 5:10 PM 2/25/2003]

 

 

i have the specs on the ITR JDM and USDM and Civic SI trannies... i need GSR info... what i specifically need is how many revs it drops during shifts at redline... the reason is when road racing, the 2nd gear in a ITR and Civic SI tranny is too tall and i run out of revs in 2nd... the ITR/Civic SI 2nd is a 2.105 where a GS-R is a 1.900 gear but they both use the same 1st gear 3.23. but i'm wondering how bad is the drop off in from 1st to 2nd. i also have a special 3rd gear i'm going to use and it would be better/closer to the 1.900 gear than the 2.105

anyone got some info for me?

 

oh... and fyi... JDM tranny isn't a shorter gear box... just a taller final drive... a 4.7 vs. a 4.4... the US market tranny is actually more of a close gear box than the JDM one... just shorter final drive... i've done my homework... i just need someone w. a GSR to go out and take a drag launch for me in their car and bring back the RPM numbers.

 

from the way that im taking this..it sounds kinda like an oxymoron..'too tall' and 'runs out of revs'...OH!! unless you mean 'drops out of revs'???..or 'gears are too short'? but yeah...if life permits..then itll be my pleasure to find out for you..unless i blow my motor..then that will just suck!!!

 

I'm not too exactly sure how much it drops in 1-2. But if it helps, you can hear your secondaries right after you shift. So i'm assuming around 5600-5700 when shifted at 8000. Although the gsr tranny has longer gears, it lands higher than the Si/ITR tranny in every single gear except for 2nd gear.

 

pretty much the v-tec b-series trannys are evenly spaced out... the big difference is the 2nd gear in the trannys... 2nd is a bigger drop in the GS-R than the Type-R or Civic Si... the GS-R 2nd is short enough to continue to get higher mph before hitting the rev limit... i just need to know how many revs drop from 1st to 2nd to see if the closing the gear ratios in 2nd-5th is worth the loss on starts...


[Modified by sleedawg, 4:38 PM 2/26/2003]

 

I'm also curious and no one has ever given me a thorough explanation except: "Type-R has shorter gears. Shorter gears = better for acceleration".

Isn't there more to it then just shorter gears? Doesn't power band have an effect also? In that case, wouldn't a JDM final drive put into a GSR tranny really stomp on an usdm itr tranny?

 

after 8000RPM in first then into second it ended up at 5.3kRPM
then a second round at 8k with a slight chearp second started at 5.5kRPM
then the last try with slightly slower acceleration left me at 5.3kRPM to start with in second...so this means with a 8k redline your second gear with a GSR will be around 5k to 5.5k RPM

 

StinkyTofu... here's a few explanation for some of the questions you've asked...

"shorter gears=better for acceleration"
Transmissions were made for street driving, driveability, and fuel mileage not for maximum performance. A factory b-series tranny will not stay in v-tec from the 1-2nd and 2nd-3rd gear shifts as the revs drop to ~5500 rpms. In the rest of the gears, (3-5) the gears drop revs on upshifts to ~6000 rpms. As we all know 6000+ is about where vtec kicks in, (unless you've modified your ECU and vtec crossover point) and thus in these engines, that's where the powerband is.

The larger the powerband, the more you can space out the gears. That's why people w. turbos like wide spaced gear boxes like the factory LS gears, because there's no need to shift with only 2,000 rpms between shifts (6000-8000rpm) because they have the power to shift from a lower point in the rev range and let the turbo spool up and pull them through the gears. Unfortunately, us N/A vtec people don't have the luxury of a wide powerband like turbo cars, so we need to keep our revs between a narrow band of revs we like to call vtec.


"wouldn't a JDM final drive put into a GSR tranny really stomp on an usdm itr tranny"
Quick answer... NO... a GSR tranny w. 4.7 fd will not stomp a ITR tranny for the simple fact the ITR tranny has a Quaife LSD. The LSD will make a substantial difference. Even if we took the non-LSD equivalent (Civic SI) and ran it against a 4.7fd, I don't believe it would get "stomped." It would lose, but not substantially.

The easiest way to think about what a 4.7fd (JDM) vs a 4.4 (USDM) will do, is imagine the 4.7fd as your first gear, and 4.4fd as your second gear. When you start pulling out of first it revs real quick and easy. Second gear takes more power to pull out of a stop, but once it gets going it's just as good and gives you a higher top speed. (note... the difference in a 4.7 and 4.4 is not as dramatic as a 1st and 2nd gear spacing at a start) That's the basic rationale of fds.

Sorry for the novel.

p.s. 10K2HVN- thanks for taking the run for me... it wasn't the answer I was expecting. But that's why, I needed someone to go check my calculations. Thanks man!


[Modified by sleedawg, 4:43 PM 2/26/2003]

 

Sleedawg: Sweet thanks for the explanation. Not trying to be technical or anything, but i thought the ITR tranny came equipped with a Helical Limited Slip and not a Quaife? When i was comparing the ITR to the GSR tranny, i was disregarding the LSD and only concerned with the gearing. Can the same rule with turbo motors be applied to n/a vtec motors that have a smooth power band? As in, no vtec spike. With cams such as toda B/C's, you can make pretty decent midrange power. Thus widening the power band?

 

Helical Limited Slip and not a Quaife
The factory Helical Limited Slip is the same design as the Quaife. Some rumors point to the factor LSD being a Quaife. (though I've never looked at one side by side) The other type of LSD is the clutch type which is the KAAZ or Mugen ones. These are too rough to drive on street everyday. Take it from me, I drive w. a Kaaz in a daily driver. OY!!!

Can the same rule with turbo motors be applied to n/a vtec motors that have a smooth power band?
Once again, it's basically comes down to how far down the powerband can the engine support. In other words, do you have the torque which Turbos/Superchargers/Large Displacements NA to support a further spaced gear box?

From my experience w. cams (Skunk, Toda, Jun, etc), you need to be in VTEC. The faster you get into VTEC or through the range of VTEC, the faster your car will accelerate. Yes, Toda B/C advertise improved midrange power, but trust me... all these cams love VTEC. And the more agressive the cam the greater the VTEC spike. Does it mean that you need a short gear box? No. The reason I'm creating a very close gear ratio hyrbid box is to keep the revs up no matter what the situation is during road racing/track conditions.

The issue I have is that on the track my ITR/Civic SI tranny redlines midcorner in second gear. If I go through the corner in third gear, the engine is flat (not in VTEC) because the gear is too short. So I'm thinking add the GSR gear to have a little more gearing before redlining midcorner, or bring down 3rd gear so I'm in VTEC earlier, or both. But I needed the GSR data first before ripping everything apart.

 

Gear Ratios VS MPH for B-series Tranny's
http://www.hondaswap.com/articles/viewer.php?id=54

i don't know if the link works but the article is on http://www.hondaswap.com
not sure if you've seen it......

bash me if it doesn't relate to your topic