[MarkGranite]

For about a year now, my 1/4 mi trap speeds have consistently been around 111to 112 mph. Before now, they used to be around 113 to 114 mph. The car is a 2019 1320. My thoughts are,

1) the car has 21k on the clock and something is getting tired. But the ET's are as good as ever. I have attached. my
runs last night with the DA around 1300.

2) Please look at Bakersboys post : Day 1 at the drag strip in this forum, and his excellent result. Every one of times and speed are better than mine, except the ET's. How could that be? Maybe physics doesn't apply (Hah).

3) Anyone have any ideas? I would like my trap speeds to return to their former glory.

 

[SickToo]

20 mph back half. Lil weak

What was it 2 years ago?

 

[Dodgenovice]

Weight, new or different tires, fuel, oil, gear and transmission fluids, worn belts or parts, plugs, etc.

 

[Rob446]

lower tire pressure, worn DR's, wheel alignment front, rear, both. When I set my rear camber to zero and aligned both ends the car picked up well over 1 MPH.

 

[ironpony]

MPH is HP what have you changed ? fuel, oil weight, diff fluid, trans fluid. Bad air, air fuel ratio, bad sensor.

 

[John Matthews]

If your ET is unchanged and consistent who cares. Mph does not win races, Et does. If the car is keeping the same ET are you staging differently? We would need to see the old time slips not just the 2023’s. You can’t really compare to your friend’s car for information .

 

[EvoRaat]

I had a 1320, you ought to be able to run 11.7 consistantly...change oil often, check tires and tire pressure, don't sleep at the light, passenger seats removed, foot brake...that was before any mods...

 

[MarkGranite]

20 mph back half. Lil weak

What was it 2 years ago?

I have records of all of my runs to date. For example, on 2/11/22 I got 114.32, 114.62, and 114.56 mph with ET's of 12.01. 12,02, and 12.00. Similar numbers on 12.03/21 and 04/02/21.

Weight, new or different tires, fuel, oil, gear and transmission fluids, worn belts or parts, plugs, etc.

I did put on Nitto 555 R11 305X35x20 tires on 20x11 wheels. The diff oil has been changed.

lower tire pressure, worn DR's, wheel alignment front, rear, both. When I set my rear camber to zero and aligned both ends the car picked up well over 1 MPH.

I did have my car aligned when I put the new 305's on back.

If your ET is unchanged and consistent who cares. Mph does not win races, Et does. If the car is keeping the same ET are you staging differently? We would need to see the old time slips not just the 2023’s. You can’t really compare to your friend’s car for information .

Yes, ET is more important IMO and the ET's are a bit less with the 305s. My consistency on the ETs is unbelievably better over the two outings, 02/09/23 and 03/09/23. Like a group of 3 or 4 runs being within .05 sec.

I found the original Nexus 275s a bit more difficult to get it right while the Nitto 305s seem to be just roast em and go.

While the Nexen appear to give slightly faster mph times, they recently were from 111.7 to 112.9 mph which is still
not the former 113 to 114+ mph values.

I had a 1320, you ought to be able to run 11.7 consistantly...change oil often, check tires and tire pressure, don't sleep at the light, passenger seats removed, foot brake...that was before any mods...

Ha! My drag racing thing is to race the car as delivered with the tire pressures adjusted accordingly. With me in the car,
I've gotten weights of 4440 and 4460 at the track, so 11.8s are probably the best I'm gonna get on regular days.

 

[Rob446]

Nexen's N-FERA SUR4G 275x40x20 are 28.7 dia. while NITTO NT555RII 305x35x20 are 28.4.

 

[ironpony]

what is the roll out/ circumference on the tires ? smaller would lower MPH ^^^^^^^^^^^^^^

 

[SickToo]

No, less rollout only decreases mph if ya run outta gear

Yes, ET is more important IMO and the ET's are a bit…
I have records of all of my runs to date. For example, on 2/11/22 I got 114.32, 114.62, and 114.56 mph with ET's of 12.01. 12,02, and 12.00. Similar numbers on 12.03/21 and 04/02/21.



I did put on Nitto 555 R11 305X35x20 tires on 20x11 wheels. The diff oil has been changed.



I did have my car aligned when I put the new 305's on back.



Yes, ET is more important IMO and the ET's are a bit less with the 305s. My consistency on the ETs is unbelievably better over the two outings, 02/09/23 and 03/09/23. Like a group of 3 or 4 runs being within .05 sec.

I found the original Nexus 275s a bit more difficult to get it right while the Nitto 305s seem to be just roast em and go.

While the Nexen appear to give slightly faster mph times, they recently were from 111.7 to 112.9 mph which is still
not the former 113 to 114+ mph values.



Ha! My drag racing thing is to race the car as delivered with the tire pressures adjusted accordingly. With me in the car,
I've gotten weights of 4440 and 4460 at the track, so 11.8s are probably the best I'm gonna get on regular days.

No brother. Not when you are contemplating whether it has lost power or not. Mph is the number you need to look at to determine power. Back half mph. (1/4m mph minus 1/8m mph).

If vehicle weight has not changed that number tells whether you are up or down on power

 

[ironpony]

No, less rollout only decreases mph if ya run outta gear

well if he gives us a little info we could do the math.
RPM at line, trans gear ratio, reared ratio. just might be running out of motor

 

[SickToo]

it’s a 2019 1320

If he could hook a 20” tall tire (and get it over the rear brake : ) it would not run outta gear

 

[TxKevinD]

This may be a silly question,but are you experiencing more headwind now? Are you running on same track? Has the track made changes (removed windbreaks/trees, etc

 

[MarkGranite]

well if he gives us a little info we could do the math.
RPM at line, trans gear ratio, reared ratio. just might be running out of motor

it’s a 2019 1320

If he could hook a 20” tall tire (and get it over the rear brake : ) it would not run outta gear

This may be a silly question,but are you experiencing more headwind now? Are you running on same track? Has the track made changes (removed windbreaks/trees, etc

If your ET is unchanged and consistent who cares. Mph does not win races, Et does. If the car is keeping the same ET are you staging differently? We would need to see the old time slips not just the 2023’s. You can’t really compare to your friend’s car for information .

Thanks to all for your replies. I have compiled all the data and attached a pdf sheet. The DAs listed are my estimates using online data at airdensityonline.com

I'm thinking a COT, catalytic over temp, could be my problem.

 

[ironpony]

Bradenton fixed or adjusted their MPH clock at the top end or are not consistently setting them in place

 

[SickToo]

I'm thinking a COT, catalytic over temp, could be my problem.

Then if I were you I would spend $400 on a 3+ and a bypass and do some logging. If you are wrong you can sell it for close to 400 bucks and if yer right you get to buy credits and unlock the pcm : )

 

[Rob446]

How does run data and associated DA indicate cat overtemp? Did the change from Nexen to Nitto take place in Feb or March of 2022?

 

[SickToo]

His back half mph went from 22 - 23, 23.5 even on a few runs…

To 22

To 21

Now its down to 20

I would be leaking that thing down warm

 

[MarkGranite]

Bradenton fixed or adjusted their MPH clock at the top end or are not consistently setting them in place

Maybe. I do not know anything about how a drag strip calibrates their devices or how often.

Then if I were you I would spend $400 on a 3+ and a bypass and do some logging. If you are wrong you can sell it for close to 400 bucks and if yer right you get to buy credits and unlock the pcm : )

I have an extended warrantee I want to keep. But, yeah I probably have to learn and do some data logging.

How does run data and associated DA indicate cat overtemp? Did the change from Nexen to Nitto take place in Feb or March of 2022?

I put the Nittos on at the beginning of Jan. 2023.

His back half mph went from 22 - 23, 23.5 even on a few runs…

To 22

To 21

Now its down to 20

I would be leaking that thing down warm

Good, you see what I see. The first step to solving a problem is to recognize there is one.

Well, I plan on going to the strip this Thursday a get a couple of runs in.