What is the best rpm to shift at for a 97 spec type r motor what rpm do most of you guys shift at when racing at the track?

 

eleventy billion RPM

it really depends on your powerband...even if you stop making power at say...8k rpm its better to shift a little bit beyond that just to carry the revs higher into the next gear. but on a stock ITR engine redline is at 8400 right?

 

If you have dyno'd your car... post that and a guess can be made from it. Or math can be done to figure out ideal shiftpoints... ahhhh math1!!!!!

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by splitime &raquo;</TD></TR><TR><TD CLASS="quote">If you have dyno'd your car... post that and a guess can be made from it. Or math can be done to figure out ideal shiftpoints... ahhhh math1!!!!!</TD></TR></TABLE>

For 90% of the cars on this board, including the stock one, the math is easy. Shift just before the rev limiter for fastest acceleration.

If you have a monster drop in torque/power, it becomes a little tougher, you have to calculate the intersection in the power curve at various speeds in the current gear and next gear, and shift when they cross (like if you make 170 WHP at 9000 RPM in 3rd, and if you shift to 4th you'll make 170WHP at 6800 RPM, that's a good point to shift.)

You can do the same thing with torque curve and gear multiplication, but that's harder to do in my head.

-Chris


-Chris

 

Dave wants to do Integrals

Chris - who says shift at the rev limiter for any ITR engine with stock cams regardless of i/h/e/tuning/etc/etc/etc/blah/blah/blah++ (turbo/sc is another story that i dunno about )

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Chris F &raquo;</TD></TR><TR><TD CLASS="quote">For 90% of the cars on this board, including the stock one, the math is easy. Shift just before the rev limiter for fastest acceleration.</TD></TR></TABLE>

I believe that is correct. However, as a practical matter, when you have the accelerator floored and you're in the upper end of the revband, the revs rise VERY fast, and it's very difficult to pick a precise rev point to shift and hit it every time. Even if you're good at it, it's tough to get closer than within 200-300 RPM of the point you're trying to hit - at least, with any consistency, especially when you're trying to keep the car pointed down the track and have a few other things on your mind, too.

On my ITR, I'm not sure where the rev limiter kicks in; I think it's somewhere around an indicated 9000 RPM on the tach (although that could be off). However, I really don't want to hit the rev limiter, because that upsets the balance of the car (just like suddenly lifting off the throttle). So what I do is, I try to start my shift when the revs hit the indicated 8400 RPM redline, knowing that I might be off by a couple hundred revs either way. That seems to work out fine for me. YMMV.

 

Fantastic sig, Ken.

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by nsxtasy &raquo;</TD></TR><TR><TD CLASS="quote">However, as a practical matter, ... I try to start my shift when the revs hit the indicated 8400 RPM </TD></TR></TABLE>

Me too. Actually lately I just shift at 8000. But yeah when I was more stock-ish I aimed for the INDICATED redline, 8400 or so.

 

bit OT do u guys shift at redline driving around streets? cuz i read somewhere on this forum ppl shift earlier when driving around on streets

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by drifter_X &raquo;</TD></TR><TR><TD CLASS="quote">bit OT do u guys shift at redline driving around streets? cuz i read somewhere on this forum ppl shift earlier when driving around on streets</TD></TR></TABLE>

As long as it's within posted limits I do as much as possible.

It makes me

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Chris F &raquo;</TD></TR><TR><TD CLASS="quote">Fantastic sig, Ken.</TD></TR></TABLE>

Suckup

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Chris F &raquo;</TD></TR><TR><TD CLASS="quote">Me too. Actually lately I just shift at 8000. But yeah when I was more stock-ish I aimed for the INDICATED redline, 8400 or so. </TD></TR></TABLE>

Indicated redline is what I shoot for about 98% of the time.

Then there's that pesky 2% where I'm trying to stay ahead of, or catch a 911 or M3 or Z06, etc, etc... And for the most part riding it out to the top doesn't provide much of anything worth the push.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by drifter_X &raquo;</TD></TR><TR><TD CLASS="quote">bit OT do u guys shift at redline driving around streets? cuz i read somewhere on this forum ppl shift earlier when driving around on streets</TD></TR></TABLE>

Ooooh, those chatroom abbreviations are SO hard to read - they make my head hurt.

But, to answer your question... Basically:

- To maximize acceleration, keep the car in as low a gear as possible without exceeding redline. Which means keeping the revs as high as possible, and shifting as high in the revs as possible.

- To maximize fuel economy, keep the car in as high a gear as possible without lugging the engine. Which means keeping the revs as low as possible, and shifting as low in the revs as possible.

How do you drive, on the street? I don't know about you, but if I'm just out driving on the highway to get somewhere, I just want to maintain a certain speed, and I'm not even accelerating much or at all. I just get up to my 75 or 80 or whatever mph, and hold it there. So I don't need to be in third gear, I'd rather get 25-27 miles per gallon cruising in fifth gear than waste $2.35/gallon gasoline and have the engine way up in the revs in fourth or third with no benefit other than making it way too LOUD. If I'm trying to get past traffic and there's a brief gap that I'd like to squirt through, I'll downshift to fourth (or sometimes third), but most of the time, there's no point in being in a lower gear. On city streets, it's even worse; again, in traffic, there is very little room for acceleration, so there's no way to take advantage of a lower gear.

On the track, of course, it's a different story.

Your choice...



Modified by nsxtasy at 10:02 PM 6/17/2005