Hey everyone, I have a question for you guys that I hope I can get help with. I have a 1993 Honda Civic Del Sol Si with the D16z6 motor. It was originally an auto but had the conversion kit put in to make it manual. I looked at the stamp on the tranny and it said P20 A000. My question is that I race a 1/3 mi asphalt track and tried to run it in second and I was hitting about 66mph at about 7000rpm in 2nd gear. My uncle has the Civic Hatchback with a D15B Vtec and says his runs at 6500rpm at about 69mph in 2nd gear. Why would this be? IT says the gear ratio with the A000 is 1.761 in 2nd gear but for some reason mine runs higher rpms then his? I NEED my RPM's to drop to continue running it in 2nd.

 

It very well could be a faulty tachometer. Many of us 5th gen owners have aged tachometers that aren't 100% accurate. I have got an issue myself to deal with in relation to tachometers. If ratios are ratios, then the speed will always be the same with the same RPM and the same gear sets, as long as it's a manual. It's also a possibility that the last owner put in custom gears to optimize the transmission to his/her liking.

But in all honesty, the tachometer is most likely the culprit.

 

Ok. So my uncles hatchback with a d15b and my del sol with a d16z6 should have the same rpms and gear ratio even though my engines bigger?

 

Engine size has nothing to do with gear ratios. The trans is what matters
I wonder how many people just got cancer from that post

 

Ok. So RPMs would be the same also

 

LEt me break this down for you real quick. Speed is directly affected by a few things in a manual transmission (and to an extent, an automatic): final drive ratio, drive gear ratio(s), and engine speed, and also the size of your tires.

Let's say that you have a final drive of 4.30, and you are in 3rd gear. Here is your imaginary gearset:
1st: 3.11
2nd: 1.85
3rd: 1.40
4th: 1.05
5th: 0.82

You are in third gear doing 2000 revs. Your output shaft to the wheels will be spinning at 4.30 x 1.40 x 2000, which is 12,040 revs, but you aren't finished yet, because you have to know the size of your wheels before you can convert that to speed.

The point is, no matter how big your engine is, be it a 455 SD in a Trans Am or a 1.4 Turbo in the new dodge dart, nor how much throttle you are applying, at 2000 rpm your output shaft will ALWAYS be spinning the same speed. Find out what gear ratios you have and what he has. You could have different transmissions. Also, look into getting a replacement tachometer. I've been looking at this one.
http://www.logicmotorsports.com/Omni.../omni-tach.htm
It was reccommended to me here on H-T. I'm eventually gonna get it. With OEM ones ranging in the 200+ dollar range, you can't beat that price. Plus, the lifetime warranty won't leave you doubting.

 

You're only getting to 66 through a third of a mile? Gearing and tire choice aside, something sounds...unhealthy about that, in regards to your motor.

 

ya id say i have a 94 del sol d16z6 1/3 mile its well over 100 and thats not going anywhere near 7k rpms but i would think 2 completely diff cars and motors are not going to perform the same

 

Whoops. I meant to say 1/3 mi asphalt CIRCLE track. Not drag haha. But I looked and both of ours say P20 A0000 on the transmission.

 

So now, not only does tire size come into play, but so does tire compound. Awesome. Put your car on a rolling road to test it. Most shops do special "dyno days", go to one, pay the pocket change to get on the dyno, and see what your speeds are in each gear at 3000 RPM. You're now getting close to too many pieces in the puzzle.