Low trap speed for current setup? Bad tune?

[millhouse]

My shifting was spot on, shifting at 6500 1st-2nd and 6800 2nd-3rd and 3rd-4th. I'm not new to drag racing. My only problem was launch because of 3:73s and stock tires. Had to baby it off the line. However, I was getting a little wheel spin in 1-2 shift. To me, even with bad weather conditions, still doesn't add up to a loss of 5-6 mph.

Why in the world are you short shifting at 6500RPM in first and second? Rev that baby out to 7000RPM in each gear. By short shifting, you are not using all of your available horsepower. You absolutely could be losing 3mph+ by short shifting it.

I'd also say to let someone else give your car a rip down the 1/4 mile. My friend thought he was a great driver. I jumped in his car and picked up 3mph and knocked off almost 0.4 seconds in the 1/4 mile.

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[kcc0521]

Why in the world are you short shifting at 6500RPM in first and second? Rev that baby out to 7000RPM in each gear. By short shifting, you are not using all of your available horsepower. You absolutely could be losing 3mph+ by short shifting it.

I'd also say to let someone else give your car a rip down the 1/4 mile. My friend thought he was a great driver. I jumped in his car and picked up 3mph and knocked off almost 0.4 seconds in the 1/4 mile.

I have to suspect that you don'thave much experience racing your car because after multiple passes down the strip I am 100% positive the short shift will improve your time. I went 11.40 at 118 with tires headers and a tune. short shifting. How fast have you been?

 

[GTBOB]

I picked up .2 and almost 2 mph "short shifting" my GT350 intake at 7200rpm instead my usual 7600 rpm shift points.

 

[millhouse]

I have to suspect that you don'thave much experience racing your car because after multiple passes down the strip I am 100% positive the short shift will improve your time. I went 11.40 at 118 with tires headers and a tune. short shifting. How fast have you been?

None on this car, but hundreds on others (I have tested this out many...many times on the street). One only needs to look at the stock dyno to understand where to shift. You don't shift at peak power on any car...unless the gearing is terribly mismatched. This isn't unique to the S550 mustang. Shifting needs to be done to utilize the most area under the HP curve. On the S550, this is right before the rev limiter.

By shifting at 6500 RPM you are leaving out 500RPM of HP that is near peak.

If you don't believe me, take a look at the stock coyote dyno.
Shifting at 6500RPM with the 3.73 gears will drop the RPMs down to ~ 4300RPM. Look at the area under the curve between those two data points.

Shifting at 7000RPM will drop the RPMs down to 4650 RPM. Again, look at the area under the curve between those two data sets.

It's plain to see which one will give you the best acceleration. By shifting at 6500 RPM you are giving up 500 rpm of near peak horsepower for 350RPM of sub-par lower RPM.

Again, this isn't unique to the S550...it's really the easiest way to see where you should be shifting for maximum acceleration.

 

[millhouse]

I picked up .2 and almost 2 mph "short shifting" my GT350 intake at 7200rpm instead my usual 7600 rpm shift points.

Was shifting at 7600RPM making you shift to 5th in the 1/4 mile?

 

[GTBOB]

No, I'm crossing the line at 6300 rpm in 4th. 3.55 manual with a 28" bias ply. Well out of my power curve for this intake manifold. I could probably stay in 4th with a 4.09 rear gear with this tire setup. Hmmm...

 

[millhouse]

No, I'm crossing the line at 6300 rpm in 4th. 3.55 manual with a 28" bias ply. Well out of my power curve for this intake manifold. I could probably stay in 4th with a 4.09 rear gear with this tire setup. Hmmm...

6300 with those gears and tires is a 111mph trap speed. You sure that's correct with your mods?

 

[RubyRed PP]

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Thanks I will give them a call

 

[RubyRed PP]

Never ever ever shift into 5th, Lund ups the rev limit to 7500 stock manifold you got plenty of rpm to wind it out. If you ever didn't have enough rpm then get a taller tire. As for the low mph I don't know if your running street tires , based on ET looks like it but do yourself a favor and get some sticky tires man , you'll trap much higher and that ET will come down by the second. I'm running hoosier slicks next time I go. always go bias ply btw

Yes running stock tires but I'm comparing to others with same mods and street tires who are trapping at 115-117.

 

[RubyRed PP]

Why in the world are you short shifting at 6500RPM in first and second? Rev that baby out to 7000RPM in each gear. By short shifting, you are not using all of your available horsepower. You absolutely could be losing 3mph+ by short shifting it.

I'd also say to let someone else give your car a rip down the 1/4 mile. My friend thought he was a great driver. I jumped in his car and picked up 3mph and knocked off almost 0.4 seconds in the 1/4 mile.

I'm doing that from 1st-2nd to reduce the wheelspin on that shift. I have tried both ways and have same results. Also tries shifting at 7000 on every gear and actually get better trap speed shifting at 6700-6800

 

[Grimace427]

Why in the world are you short shifting at 6500RPM in first and second? Rev that baby out to 7000RPM in each gear. By short shifting, you are not using all of your available horsepower.

The street tires couldn't handle any more power in 1st gear anyway so short shifting the 1-2 shift is perfectly acceptable, even optimal.

Yes running stock tires but I'm comparing to others with same mods and street tires who are trapping at 115-117.

Same day same strip?

 

[RoadCone]

RubyRedPP,

How is track prep for Kil-kare? How do cars with sticky tires do?

Edgewater is BAD.... so I may travel in the next few weeks.

 

[RubyRed PP]

RubyRedPP,

How is track prep for Kil-kare? How do cars with sticky tires do?

Edgewater is BAD.... so I may travel in the next few weeks.

I feel like track conditions are always good. I used to run my 01 Bullitt there and was able to hook up just fine with my nt555r drag radials (best et was 12.55 with around 1.7-1.8 sixty foot. Sad that I can't come close to that with my 15 GT, although my Bullitt had 100 shot.

 

[RubyRed PP]

Same day same strip?[/QUOTE]

You do have a point but I'm also comparing same DA of others. The only variable would be a different track. I doubt a different track could account for 5-6 mph difference. I don't know maybe I'm crazy , just trying to figure Out if that's the case.

 

[RoadCone]

Same day same strip?

You do have a point but I'm also comparing same DA of others. The only variable would be a different track. I doubt a different track could account for 5-6 mph difference. I don't know maybe I'm crazy , just trying to figure Out if that's the case.[/QUOTE]

I believe a different track could. Track prep is huge. That is why I asked. I don't expect my mph difference to be huge at different track, I believe DA will be the bigger factor in that, buy as far as ET, the track is where it is at.

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