Poor ET at the drag strip

[SteelSteeds]

I'm kind of at a loss, so I'm looking for some opinions:

 

Every season I make around half a dozen trips to the drag strip with my '98 Cobra. Two years ago in October, I got my best time ever: 13.70 @ 101mph. In my quest to go faster, I upgraded the rear gears to 3.73 from the stock 3.27s. The next spring, I couldn't even get that time, I was doing 13.8 - 14.0. So, I changed plugs, wires, cleaned the K&N, and no change, same ETs.

 

Tonight was my first night out for this year, and my best was a 14.0. I was pretty bummed. These times are on Nitto 555R drag radials, which are only used for racing.

 

I know I'm not the most skilled driver, but I did better with the stock gears! I know one factor was the temperature, that October night was around 50 degrees, where tonight was 10-12 degrees warmer, but still...

My car has 71k on it, meticulously maintained, 92 octane, and not a lick of mechanical trouble the entire time I've owned it. Am I just slowly losing hp due to wear and tear on the motor? I'm sure there's a small drop, but I wouldn't think it would be that much.

 

Plus, damned if I didn't grind 2nd TWICE tonight! But, from what I've read there isn't much I can do about that but swap the tranny out...

 

Mostly just venting, I was really hoping to do better. There were some scary fast diesel trucks at the strip tonight. Low 12s in a Dodge extended cab 4x4. What's up with that?

[Orf]

There were some scary fast diesel trucks at the strip tonight. Low 12s in a Dodge extended cab 4x4. What's up with that?

 

 

Sorry I can't help with your dilemma, but the diesel thing perked up my ears. I'll have to try to find the site again, but I recall seeing one about an F-250 with a Power Stroke enigine running high 11s. They had Banks products, propane injection with methane cooling, and even nitrous spray on top of the propane. The engine output was something like 650+ Hp, and 1100+ lb ft torque.

 

These were all things I considered for my Excursion, until I asked myself: Why?

[Five Oh B]

I'm kind of at a loss, so I'm looking for some opinions:

 

Every season I make around half a dozen trips to the drag strip with my '98 Cobra. Two years ago in October, I got my best time ever: 13.70 @ 101mph. In my quest to go faster, I upgraded the rear gears to 3.73 from the stock 3.27s. The next spring, I couldn't even get that time, I was doing 13.8 - 14.0. So, I changed plugs, wires, cleaned the K&N, and no change, same ETs.

 

Tonight was my first night out for this year, and my best was a 14.0. I was pretty bummed. These times are on Nitto 555R drag radials, which are only used for racing.

 

 

You can see in my signature that swapping from 3.55's to 4.30's didn't help my ET's, either, and I consider myself a better-than-average drag racer (same track for 24 years).

 

I'll leave weather out of the equation for now, as you mentioned it was warmer, but not terribly so. You may want to check your air/fuel ratio, though. It's something you don't really feel or hear (unless it's too lean and your car is pinging like crazy), but it can really slow the car down if it's way off. Maybe you have aftermarket exhaust or a cold air kit that is leaning out your air/fuel ratio? If so, get a handheld programmer to richen it up or have a speed shop dyno tune it for you. Or, perhaps you oiled your K&N air filter too much and dirtied the MAF sensor or screen? If so, that would lean out the car, too. Reclean the K&N, re-oil very lightly, clean off the MAF sensor & screen, and try it again.

 

Also, assuming you're getting good traction with the D/R's, you may want to launch at a higher rpm - maybe in the 3,500 to 4,500 area - or as high as possible without spinning. DOHC's love to rev! If you are not revving it up to launch, then you are likely bogging your high-strung DOHC off the line and giving up valuable ET while you rev back up to the powerband.

 

Your car should easily post sixty foot times of around 1.80 to 1.90 all day long if your D/R's are hooking up and you're launching with enough revs. For every extra tenth to the sixty foot mark, you can expect your 1/4 mile ET to suffer by two tenths. For example, if you run a 1.8 60' time and on to a 13.50 ET, then you could expect a 2.0 60' time to slow you down to a 13.90 ET. Most of the 1/4 mile ET is determined in the first 60' and your shifting ability (get a good aftermarket short-throw shifter if you don't already).

 

On a side note, there's a little formula I use to make sure I'm driving my best. If you take your 1/4 mile ET and multiply it by your trap speed in mph, you should get a number between 1350 and 1500 roughly. The closer you get to 1350, the better you're launching and maximizing your traction and drivetrain. The higher the number, the worse your traction or driving. I tend to average about 13.10 @ 105mph, which when multiplied is 1375 - not far off the ideal. If your car runs through the traps at 101mph (like you mentioned above), you should be able to drive your way to a 13.40 if you launch & shift perfectly (1350/101 = 13.37). Do this math with your timeslips. If you have a bunch of them over 1400 when you multiply the ET & mph, then you've got to launch harder, control the spinning or bogging (whichever you have), and shift quicker. Again, really focus on getting sixty foot times to 1.8 for your car.

 

If your mph is starting to fall (not 101mph anymore, but getting lower), then you may very well have an engine that is getting tired. MPH tells you how much HP your car is putting down, while ET tells you how well you're launching and hooking up. If the MPH is still 101mph, then it's your driving/racing technique. If the MPH is lower, then it's your engine.

[Evil95GT]

To add to the wisdom of Five Oh B, I'd definitely concern myself more with MPH than I would elapsed time.

 

For example, when my car was running 12.9s at 107, I *knew* there was a hell of alot more in it. I attributed the offset between ET and MPH to my 60 ft times, which were between 1.89 and 1.95 (extremely poor if you ask me, considering the fact that the car has 4.10s and had BFG drag radials at the time).

 

Now, on to the gears. I started off with (blush) stock 2.73s. I made the jump to 3.55s, and found that it simply wasn't enough for a combo that loved to rev high and made most of it's power in the top end. I kept them for 600 miles and made the switch to 4.10s. Right now, I feel I could get away with a 4.30, but I think the husband would wring my neck.

 

Make sure you're considering all the variables..........tire pressure, launch RPM, shift RPM, weather, etc. All of those things will affect your ET.

[SteelSteeds]

Wow, a ton of excellent info, thanks all!

 

To address the points:

Orf, I was told by the driver of the Dodge that he was putting down 1200 ft/lb of torque at the wheels :o

 

Five Oh, I'm running long tube headers, high flow cats, and Flowmasters, but I had all that on when I was running better. MAF/filter look great, no pinging. I'm launching around 3000, but I tend to spin. I know my clutch technique is where I need the most work. I have a hell of a time forcing myself to slip the clutch, I'm always trying to get out of it and feather the throttle. I *know* that's not the way to get the best times, and I'm slowly re-training myself. I had a similar problem when I first got this car - I was used to low end torque, and shifting before 5000, which didn't work so good with the DOHC!

 

So, my 60 foot times sucked on Friday. I was doing 2.1 - 2.2 all night. The last two seasons I was getting those 1.8-1.9s. Since this was my first time out this season, and I was feeling the adrenaline, maybe that's the whole problem. My first few runs my mph was bad, but my last run was over 100mph again. Using your formula, my best result is 1400. I'm running a B&M Ripper shifter, which I like very much, but I still get that damned 1-2 grind, and sometimes it's BAD. I know, that has nothing to do with the shifter, and everything to do with the T-45.

 

Michelle, you're right about the variables. I've played with tire pressure, but never get consistent results (again, more due to my lack of driving skill than anything else). I know weather/temp is a big factor, and always try to run on the cooler nights. The hot nights in mid-summer are always disappointing. Launch rpm I'm working on, but shift RPM I'm curious about. I want to get a dyno tune this summer, there's a place in Vancouver WA I've talked to a few times that swears they can help me a lot, and I know they've tuned a lot of 03-04 Cobras to some fantastic times. With a good tune and a dyno graph, I'd know exactly where the best place to shift is. I'm going more by ear/seat of the pants than anything else.

 

Bottom line: I guess I figured if I kept practicing (just going to the track), my times would improve. But it looks like I'm gonna have to do my homework to actually acheive the desired results. What a concept!

:D

 

Again, thanks all for some outstanding advice and insight. I feel much better now, and am more convinced that it's just me, and not my car.

[Five Oh B]

Lance, feeding just the right amount of clutch is going to really help you strike the right balance between bog and tirespin. Keep practicing and those 60 foot times will get closer to 1.8's and your ET's closer to 13.50's @ 101 mph. Invest in some slicks, air them down, heat them up, and you can side step the clutch and forget about feathering the clutch if you prefer. Of course, you might start breaking stuff (i.e. especially axles).

 

Shiftpoints are important. You want to shift at the rpm that drops you into the next gear at about 500 rpm's lower than peak torque. Your DOHC (with the exhaust mods) likely makes peak torque around 4,000 to 4,500 rpm's, so you'll want to rev each gear high enough (maybe around 6,000 to 6,500 rpm's depending on gear ratios) so that each shift drops you down to around 3,500 to 4,000 rpm's. This should maximize power by keeping you in the powerband for your motor.

 

It's all about practice. I mentioned I've been drag racing at the same track for 24 years, so I've got most of it figured out, but I still have to "re-learn" a bit at the beginning of every season.

 

Good luck!

[JETSOLVER]

Good stuff everybody. A few things that helped me get into the 12s, Fresh plugs. This car seems really sensitive to plug fouling esp the middle cyls. And those darn seals at the cam cover can leak for no reason and foul plugs. If the wires are original, change them. Most folks think the FRPP 9mm wires are the best. As for the tranny meander over to SVTPerformance.com in the SN95 COBRA thread, do a search and you will get A LOT of advice re the tranny and additives. Real problem on the SVT(I had mine rebuilt several times.) As for launch you'll have to feel out your tires but the car is fairly heavy so keep working higher about 250 rpm at a time until you blow them off. I found that the big thing in getting my numbers down was going to 6800(indicated) at the top of each gear. It really is hard to get used to it, but the B head needs revs to work its best. And its almost impossible to hurt the motor in stock/near stock trim. As I say SVTperformance is an excelllant source for these cars and if RPM motorsport in VANCOUVER, B.C. is still around they are all about mod motors. Searching for the link now....

[SteelSteeds]

I've got a fresh set of NGK copper plugs (forget the number off the top of my head), and FRPP 9mm wires (blue, of course). The original platinum plugs that I took out actually looked just fine; no fouling, minimal wear, but they had almost 70k on them and I'd read that the copper plugs give you just a hair better performance, at the expense of needing to change them much more frequently.

 

Vancouver BC is a bit of drive for me, I'm in Portland Oregon. The town just across the river from Portland (OR/WA border) is also called Vancouver, which causes some confusion. I lived their briefly when I first moved to the area, and friends/relatives back in Montana were always getting confused, thinking I'd moved to Canada... Not that that would be a bad thing!

 

I'm running the Red Line synthetic AT fluid in my T-45, which I decided on after reading mountains of opinions. It hasn't been appreciably different in feel since I changed it.

 

I haven't been running that high before I shift, it feels like I'm not pulling as hard once I get over 6000, so I've been shifting between 6k and 6200. That's completely seat of the pants though. It pulls like crazy from ~4400-5800.

 

Right now I'm thinking I should add a CAI, and get a dyno tune, and just keep practicing. If I was planning to keep this car, I would seriously be looking at the T-56 upgrade, but since I plan to trade/sell in order to finance a GT 500 (next spring), I just want to have fun for a while without blowing anything up!

 

Thanks for the advice!

[JETSOLVER]

Sounds like you have got most of it handled. You have pulled the intake cover to get an idea about your IMRC's right?

[kaylan1521]

I too got tired of inconsistent 60' foot times on D/R's so I went the Slick/Skinnies route.

 

Since then I've done about 75 runs and my best 60' is a 1.54 and I average 1.61.

 

I also just ran in a bracket event in Texas and all 8 of my runs were within .06

 

So, what I am saying is forget the D/R's and go the slick route.