Hi......I just read a post from bucrx7. He stated that his engine went bye bye. When reading his post he says that he downshifted to 4th gear to pass up a car. The ? is: Is it bad to downshift on a rotary engine? This is not the first time I've heard of this happening. It happened to a friend of mine about a year ago and to other people on the net aswell. I own all three generations and rarely downshift, I actually put it in nuetral then to gear, but never downshifted from say.....50mph (4th)then to 3rd...I just don't have a good feeling about the way It will sound or what it may do to apex seals. If anyone has any info on this..PLZ let us know

 

I know this debate has raged for years. I downshift all the time. Anyone who road races the car, downshifts probably 30-40 times per lap. The key is matching revs when you downshift to perserve your sychros.

As far as blowing engines. I don't think the downshift is what got them. It was more along the lines of too much boost, not enough fuel. They just happened to have downshifted.

 

The only way that downshifting from 5th to 4th would cause problems is if you are doing triple digits. Downshifting will not hurt the car at all if you do it right, just make sure the gear you do go to will be under 6k rpms (racing).

 

Come on buddy, this is a high-end sports car. Downshifting should be as common as upshifting. Hope you are just being sarcastic.

Ant

 

How would you even drive the car if you never downshifted?

 

I'm not sure how downshifting would cause detination. The throttle body is basically closed when engine breaking and there would very little fuel going into the engine, perhaps even none. How could you detonate? Anyone know?
As far as rev matching, for me, that's become habit, or second nature. What? You granny shifing instea of double shifting like you're 'sposed to?
Sorry, I just had to say that.

 

If anyone is curious, my PFC shows 0.0% inj duty cycle while engine braking. I'm sure some fuel is getting in there, just less than .1%.

 

Most people don't realize the partial truth to this.

Downshifting from fifth to fourth does put some strain on the system, especially when you use it to accelerate. Dyno pulls are done at fourth gear, and thats where some poorly tuned engines go bye bye.

In fourth gear you are pushing the most boost for an extended period.

This is not to say that the FD doesn't handle this well, it does. That is what it's built for. But not a poorly tuned FD, especially one that lacks enough fuel at that kind of boost and engine stress.

As far as downshifting from fifth to fourth to use it just as a brake, is a waste. Put the stress on your brakes, not your engine / clutch, and tranny which are harder to replace than your brakes. Again, this should not cause any issues, unless it is poorly tuned and probably just letting the gear slam into the higher revs without rev matching.

Tuning is the key.

 

Trick to downshifting is RPM matching. You have to find out what your gear's mph ranges are. I think the RX 7's 3rd gear spans to 100 mph but I'm not sure of this (so don't try it!) So if you are 80-90 I'd pop it into 3rd not 4th...if you pop it into 4th and he pops it into 3rd, I don't care that you drive a Supra or 7, you're gonna get rocked right off the bat. Also before you downshift, take a look at your rpm...before you downshift, ALWAYS hit the gas kind of hard and let your engine rev up then snap it into the gear...never let your engine go limp then throw it into the lower gear where your car buckles and slows down...you want "VRRRRRRRRRRRMMMMMMMMM ::pop:: ERRRRRRRRR VRMMMMMMMMMMMMMMM"

 

Do NOT go into 3rd at 90mph! 70 is the max I'll put it into 3rd! Don't use the tranny as a brake, brakes are cheaper, easier to come by, and alot easier to install. If you don't know how to downshift, buy an auto.

 

C'mon man...how can an RX-7 not handle higher than 70 on 3rd gear? My friend's BMW m3 '95 handles 96 mph...can anyone confirm anything?

 

Top speeds in gear for the FD are roughly:

1st: 40
2nd: 70
3rd: 105
4th: 140
5th: when you run out of power, or about 200 MPH (it's tall)

Note that this doesn't mean downshifting to 3rd at 104 MPH is a good idea. I might go for a quick squirt in 3rd at 90 if the competition is tough, but I'd usually just start in 4th for a run that starts at 90 MPH. I would definitely go into third at anything below 80 MPH.

-Max

 

You can downshift to 3rd at 90 but you will be redlining so whats the point? If you downshift to 3rd going that fast it should be to race. 70 puts you at a good rpm and a little room to wind it out in 3rd.

1st gear ends at what 38? So are you going to downshift into first at 38?

 

I know my 4th doesn't go to 140. Highest I've had it to was 130 and I had to go to 5th, that's with stock size wheels and tires. I would look at the speedo in 1st, 2nd, or 3rd but I don't get the chance, paying attention to other stuff and they go by too quick.

 

I am a strong man and It's hard as hell for me to downshift into 1st at 10 mph...but 3rd with 90 is for racing purposes only don't get me wrong...it's useless to downshift into 3rd with normal driving. But you gotta be quick man...even if it's just 300 rpm until redline, you gotta make that shift...that is some good speed your wasting if you don't...downshift into 3rd, run it's course, then quick shift into 4th. Hardest part about shifting is getting it into 3rd from 2nd...damn fd lol

 

I'm with Gsrsol on this one, if you are reasonably close to stock, there would never be a reason to downshift into 3rd above about 80. The heart of the powerband on a close to stock car is 5000-7000 rpm. After 7k it starts dropping off. What's the point of downshifting to 7k rpm? BTW, since the normal technique for matching revs is to rev it over the correct point and shift as it's dropping, what do you do to downshift to 7k? Blipping the throttle to 8k without hitting the red limiter just to downshift? I don't think so. If I'm much above 70 mph, I just leave it in 4th.

 

Hi everybody,

I had a question about this whole downshifting thing too. I plan on buying an FD in the future, so I wanted to know this.

If I was cruising along in my FD in 5th and say down shifted into 3rd and the RPM's were to go to 1000 RPM's before redline and just mash the gas, would that cause any strain on the engine?

I drive a 01 VTEC Prelude and when I need to pass someone I usually down-shift to a point where I am right at around 6500-7000 RPM's. Lude has a redline of 7400 and fuel cut is 8000 (I upshift at 7900).

I'm just used to downshifting aggresively, and I was wondering If I do he same thing in the FD, will it cause any unwanted strain on the rotors, housings etc? will the fuel system be able to react fast enough to prevent detonation?

 

i think 1st gear was designed with gear protection in mind. it resist downshifts above 10 mph. that is why it's hard as hell to downshift to first when crusing even at 10 mph, but once you drop below, say 5 mph or so, it slides right into gear. try it if you don't believe me.

 

Most cars no matter wut they are dont like to be put into 1st above 8 or 9 mph... Go home and go run around in 2nd then push ur clutch in and just push the handle up with force till it slides in..

 

I've heard that it is possible to downshift into first when going 10-20 MPH all you have to do is double clutch.

a member on club si (Civic Si) says that he downshifts to 1st when he is racing from a 15-20 MPH roll.

EDIT: I haven't tried it myself so I dont know if it actually works.

 

ive been driving for awile not just rx7's but corvettes,hondas,vw's,ive drove just about everything hard and if there wasnt a rpm guage in the car i wouldnt even notice becuase i basically go by feel and sound also speed has alot to do with downshift decision making it might sound like a load of crap but i can feel when a car is stressing second nature i think. for those of you who dont feel me or the car buy a shift light =)

 

I was just wanting to see how many people heard about this. It seems to be a myth.....could have been my freinds shitty driving skills. Don't get me wrong..I do downshift in all my cars...but try not to do it alot. No wonder my brakes don't last as long...Thanx for all the info guys......

 

downshift all the time to slow down. Alsways done it on all the cars. RX-7 both 1st & 2nd Gen. will lock up the wheels for second, going about 50-60 drop it 2nd, its an excellet rear end slide when you take them crazy *** corners.

 

It happened to me in my t2 I downshifted from 3rd to 2nd and the turbo ate an apex seal...the same thing happened to this guy's daughter that we know, but with the 3rd gen...she went form 5th to 4th to pass another car...I think that Jorge knows what I'm talking about

 

I downshift all the time but only hard when racing, and I typically go from 3-2 b/c the tires chirp and I seem to gain the best mid-roll launch.

I talked to one of the guys from Rotary Performance (RX-7.com, they're in my area and built my motor) about whether or not rev matching is important to prolong the synchros and he said NO, that the RX-7 has an auto-sync or something that makes it A-OK to downshift frequently without matching revs. I believe he said most cars have this.