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RB25 Transmission Limit


Zman0690

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Nash is correct on the tranny swap. I'll ad that all the internal gears, gear ratios, spring inserts, and synchros are interchangeable from the RB25 RWD trans to the Z32 trans

 

Its basically taking the input shaft, and bell housing from the RB tranny, and mating those with the 300ZX transmission. This allows you to use the stock mounts, electronics, driveshaft, and even the electrical connections from the Z32. In fact, the entire alternator/oil sending unit harness is a plug-n-play operation going from the VG30 to the RB26

 

I am personaly going through all of this right now, and I'll be takign alot of pictures as I do it. My plans for tearing the trans down is to combine all the good synchros/spring inserts from both trannies.

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Sorry to burst your bubble, but I'll school you any day on drag racing....

 

Reaction times have absolutly nothing to do with your ET or Trap speed. My out of the box times on average are 1.5-1.6, and to my knowledge, there arent any Z's that average quicker. I have seen some 1.4's before, however its a very rare case. In any event, shaving off one tenth of a second on your 60 foot time, only shaves off one tenth of a second off of your 1/8th mile time. It would consequently shave two tenths of a second off your 1/4 mile time

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Well, I'm in no way a drag expert but, what I was trying to say, correct me if I'm wrong, was: If a car starts to accelerate later than an other (due to power band, not one accelerating after the other) but, once it does reach it's peak torque, starts accelerating faster then the other, he could reach the end of the track quicker but with a lower speed...

 

It's hard for me to explain as I'm no expert in that area but, I've witnessed some races in which the "looser" actually had a higher top speed than the winner but, took more time to reach the line.

I know reaction has nothing to do with speed but it does have something to do with your total elapsed time right????

 

P.S.: Would you happen to know a certain Mark Martz??? He's the guy I bought my Z from and he's also from Peoria. What a coincidence.

 

 

Drag racing has nothing to do with speed, its all about the fastest time (ET) The races you have seen were probably actual timed races where you're reaction time is factored in with your ET.

 

Say for example your reaction time is .4 of a second and you run a 12.00 1/4 mile. Your opponent has a reaction time of .2 of a second and he runs a 12.00. Your total time is 12.40 and his total time is 12.20, thus he wins.

 

The reason you see higher speeds, but yet the person could have lost is due to a few reasons, but is mainly traciton. Its hard to explain the phyics of this, and alot of people dont comprehend, but the less traction you have, the faster you will go, due to the more time you ahve to build up speed. I'll try to setup an example

 

Say you run a 12.0@120mph and then you run an 11.5@120mph. The second run, you got way better traction. It took you 12 seconds to accelerate to 120, wheras the 2nd run it only took you 11.5 seconds to accellerate to 120. If you had that extra 1/2 second, think of the extra speed you would have gained....

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Unless the timing equipment is wrong at our local dragstrip (mobile, AL) , i am looking at the timeslip right as i type.

Reaction +.3138 needs improvement

60 ft - 1.6813

330 ft - 4.8321

1/8th - 7.1392

mph - 86.03

 

 

Have any idea what your car weighs?

 

Here's a timeslip of mine with a similar 1/8th mile time

 

11.2@124.JPG

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Well I'll first start off by saying that there are many more variables than can be accounted for in a short post like this but you have hit on a few important ones and that is the power to weight ratio, which is most directly related to ET. MPH, as stated, is mostly dependant on traction and secondly by gearing. Of course I'm no engineer, so I'm sure someone will come along and set me straight on this. With that said you can have some moderate variances in MPH, however ET's of cars with similar power to weight ratios should be almost identical given equal traction and gearing.

 

I'll sit here and wait patiently for someone to correct me as I'm sure there is someone here who knows more about this than me.

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.....

The guy that took his car to the limits his name J Taylor found him self with a smoking piston after he raced a Viper but hes tranny was absolutelly fine as far as i know. And thats with an RB25 with stock internals.

...

 

Just to clear up any confusion,(since I have some reading what you wrote), J Taylor has a TH350 behind his RB25. Sure, stock internals on the ENGINE, but he is not running the RB25 transmission. If you watch the video of the run vs. the Viper,(where he killed a piston), there is no drop in sound on shifts, i.e. an automatic transmission. Smooth acceleration w/no boost drop.

-Bob

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My apologies guys, JT is right about our track being 60' short which I did not take into account. I thought the computer did the correction on the timeslip. I have emailed the local track about all this and what our projected true 1/8th mile would be. The track did answer a few of the logic questions I had, but they also invited me to the tower this Saturday to watch the computers to see how everything works and to ask questions. I look forward to the education since drag racing is still new to me. Definitley different mindset than road racing.

 

Dave

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