What is the best shift point for racing????

[K-S-W]

I have always been a dedicated honda and acura enthusiast. When you hit redline on the hondas you have vtec. Maxda is a diff. roll with redline, no power. The low end on MSP's murders honda hands down. So my question is, if i'm racing at the track what is the best shift point to shift at to stay in the maximum power range. I'm guessing 5500 rpm's.

 

[t3ase]

If you search for dynos in the Mazdaspeed section, I believe the power starts dropping at around 6000 or 6200. There's no point redlining the car but if you get it in that sweetspot, you're right back in to boost. Lemme suggest getting a GTech if you're that concerned.

 

[InsidiousMSP]

6500rpm. Regardless if power drops before then, you want to stay in the powerband.

 

[t3ase]

6500rpm. Regardless if power drops before then, you want to stay in the powerband.

you have a dyno that shows that?

 

[ThrillRide]

me experience at the track...if i shift before 7k my et's are lower. take it to 7 imo and you will only need 1-3. best times taking it to 7

 

[t3ase]

me experience at the track...if i shift before 7k my et's are lower. take it to 7 imo and you will only need 1-3. best times taking it to 7

ack. I'll pass. :/

 

[jersey_emt]

me experience at the track...if i shift before 7k my et's are lower. take it to 7 imo and you will only need 1-3. best times taking it to 7

I need to shift to 4th gear or else I'd hit the rev limiter in 3rd in the 1/4.

 

[InsidiousMSP]

you have a dyno that shows that?

How will a dyno show that?

 

[t3ase]

at least give us a visual aid as to figure out the power band. that'd be a bit better than everyone sayins "6, 6.5, 7k, etc"

 

[InsidiousMSP]

at least give us a visual aid as to figure out the power band. that'd be a bit better than everyone sayins "6, 6.5, 7k, etc"

You don't run through gears on a dyno. I don't even know off the top of my head what rpm you land at when shifting to 3rd at 6500rpm for example, but I know it's a hell of a lot better than shifting at 6000. Best way to see is try it yourself. I'd definitely recommend it.

- 14.3 @ 98mph, Intake & 11psi.

 

[t3ase]

Nah, I'm done tearing my car up.

By the way, I realize that dynos aren't multiple gear pulls. If you find the gear the car was pulled in then if you learn your car and know the rpms you will land at when shifting, as you mentioned, then you can use basic logic to find the proper RPMs.

Correct?

 

[AutoBox]

dyno would only show u th epowerband of that gear its dyno on....gear ratios etc all factor in on a good shift point.....in general i like to shift at 7k in 1st and 2nd and 3rd i shift at 6500....ur boost trails off around 5700 or so.....at least my stock msp does....another factor is upgrades.....dependin on ur upgrades ur power band will shift....u cant fully attain a shift point for each gear until u datalog a complete run and see where ur power trails off in each gear......but unless ur drag racin is really important i would jus shift around 6500 or so...few hundred rpm aint gonna make much of a difference

 

[mcstark]

Basic logic with shift points is this (according to Car & Driver back in the day): you want to shift when the power (hp & tq) available in the next gear is higher than your current gear.

So it would make sense if your car is peaky, which most 4 bangers are, that you should shift closer to redline.

Check this out (I know it's a P5 dyno, but you 'll get the idea):
/members/mcstark/MISC/dyno.jpg

The red lines indicate (approx) the max torque and hp. The green lines indicate just past redline in a P5. If you shift at the red lines your rpm's will drop, hence the power available in the next gear will fall off. But if you rev to the green lines then you should hit near those max figures in the next gear.

This is the theory they (C&D) use to figure their shift points for when they test cars. In my experience (in my only other stick), is that once you get the rpms up you should be in the powerband all the way to fifth -- unless you've got f*'d up gear ratios.

 

[ThrillRide]

i am not moded so i don't hit the rev limit. i shift at 6800 to 7000 on 1-3. i shifted to 4th only once and my times were .333 higher than the others.

 

[Maniac0301]

Lower gears multiply the power that your engine puts out. That is why if you were to run a dyno in 2nd or 3rd gear the numbers are high. This multiplication factor from the gearing more than makes up for the drop in power after we hit peak. Waiting til redline to shift will be the fastest especially if it keeps us from having to throw in an extra shift.

 

[Notorious]

Heres the thing, if you shift at lower rpms then you just gonna hit less power when shift into the next gear. Yeah you gonna lose some power running it to redline, but the next gear that you shift into will be closer to peak power. I recommend shifting at red line. I bring the tach up to 7, which because of inaccuracies is closer to 6600 rpm.

 

[SPDRCR]

Continuing on with what mcstark wrote...
I recall from a Car and Driver or Road & Track article years ago that you can mathmatically calculate the optimum shift point for any car. As mcstark said, the theory goes, shift at the point when the power, and more specifically, the torque, available in the next gear is higher than the torque in the current gear. Everything revolves around torque and not horsepower due to rate of acceleration (or something like that). So much for horsepower is king.

Heres the simplest formula of many I found. This one came from a Miata board:
Lower Gear Ratio / Higher Gear Ratio x Torque Peak RPM = Shift Point

So for stock, with a torque peak of 160 @ 3500 RPM given the gear ratios the shift points look like this:

1st 3.307 / 1.842 x 3500 = 6284
2nd 1.842 / 1.310 x 3500 = 4921
3rd 1.310 / 0.970 x 3500 = 4727
4th 0.970 / 0.755 x 3500 = 4497

Now, before anyone goes and gets their panties in a bunch, I know that seems unreasonable, but that's the math. And I haven't tried it yet to prove one way or another, but I'm open to hearing anyone else's results.

It's also interesting to note that, the point is to shift where the torque in the next gear is simply higher and that does not neccesarily mean the peak, so this formula still may not be the mathmatical exact shift point since in any gear the torque may be higher in the next gear but still below the torque peak. Ultimately this chart is the theoretical the very latest shift point to maximize acceleration because, by definition, as you approach redline there is no gear where the torque is higher than the torque peak in the next gear.

Another factor to consider is that due to boost, the torque curve may not be exactly the same in every gear in a real world situation (ie. diff boost levels in diff gears). But that would probably only affect 1st gear noticeably.

Finally, for anyone with mods, you'll obviously shift at different points since your torque curve is most likely higher.

 

[2K3 MSP]

me experience at the track...if i shift before 7k my et's are lower. take it to 7 imo and you will only need 1-3. best times taking it to 7

1st-3rd? I only get to about 82mph in 3rd gear...The MSP is able to hit 100mph+ in the 1/4 mile. That's definately gotta be in 4th.

 

[rocketspeed]

I don't believe an MSP can hit 100 in the 1/4. Not a stock one, anyway.

This is from my GTech:
/members/rocketspeed/gtechhpcurve.jpg

As you can see, on my car, the HP peak is at about 5,900 RPM's.

If you're shifting at 5,500, you're not even reaching peak HP.

I can tinker with my GTech more tonight and pull down more data to back this up, but its my belief that for 1-2 and 2-3 shifts anyway, redline is your best shift point.

 

[ThrillRide]

1st-3rd? I only get to about 82mph in 3rd gear...The MSP is able to hit 100mph+ in the 1/4 mile. That's definately gotta be in 4th.

NO. I am un moded and my speeds in the 1/4 have been around 88mph. Go search for a thread called 1/4 miles times. You will note that the moded cars are the only ones hitting 100mph.

I don't believe an MSP can hit 100 in the 1/4. Not a stock one, anyway.

True!