Revealing dragstrip weirdness

[Darth Vader]

I just took my car (08 GT) to the track again, after a round of recent changes. I previously went with an AEM CAI + an epoxy MM. Best I got was 14.2 at 99.2. That was a first effort for the car/me driving it so, I didn't think it was that s***-hot but, allright.

This time, I added a Corksport DP heading into the second cat, a Forge on the red spring, a PG TIP + and ETD to hold the engine up. The car's ETs have plummeted from this and my greater experience with the car. I'm down an average of .77 seconds from the previous setup. I banged off 4 straight high 13s on stock oem tires. Best 13.84. (Hitting the helmet line with what the track officials thought was a regular Japanese-plastic hatchback was icing, I must say.)

The weird thing is, I can barely beat my last mph best of 99.2. The best I did was 99.72. On AVERAGE, I'm up 1.6 mph but, the car doesn't seem to be delivering the mph I expected from a DP mod (plus the other stuff) on a turbo car. Weather was good, between 45 and 75% relative humidity and 101 on the baro so, it wasn't air.

I have no way of monitoring the engine at this time but, by all measures in the real world, the car is running much better but, it's just not making the #s, mph wise. The engine's compression is good and even and the plugs are new.

Is that second cat that bad a cork? I have trouble believing that.

Any other ideas I might have overlooked? I am not new to drag racing or modifying cars, having done the first for over a decade and the second for over 25 years.

 

[zx2man]

Ill throw my 2 cents in..I dont dragrace so im no expert at all..but couple factors that come to mind is..even though you have added couple mods..1st 2nd gear are still limited on power..thats gonna hurt you speedwise..the oem tires are imo not a really good tire getting quick trap times..and also the shifter is alittle long...so some stickier wider tires and better shifting? get that power to the ground and you should break 100's easily..most car magazines have ran the stock ms3 at 13.8-14.0 and around 100-102 trap..so it can be done..specialy with your mods..maybe it takes more practice launching these fwd ms3's..I honestly think that the limits in first 2 gears along with fwd platform will alwas hurt the times in this car.

 

[Darth Vader]

I already have a SS plate on the car, as well.

I think I'm getting power down, the drop in ET indicates that. I don't find the car hard to launch particularly at all, especially for a front driver.

The low mph tells me I'm not delivering as much power on the big end as I expected.

 

[evilmonkey]

what are you launching @?shifting @?what about a high rpm 2nd gear launch?...<----never tried it but it might also kill your 60 foot times

 

[Darth Vader]

2500-3000, slipping the clutch. Making 2.1 60' on oem street rubber so, I think I'm ok at the front end. I'm flat shifting a little under 6k. It doesn't seem to matter if I run out 4th at the stripe or pop a quick one into 5th but, I only did the pop to 5th once so, maybe not definitive data yet.

A high rpm 2nd would kill the 60 foots and likely the clutch, imho.

 

[evilmonkey]

A high rpm 2nd would kill the 60 foots and likely the clutch, imho.

i was thinking the same, i think launching a bit higher and letting them spin a bit would yeild slightly better short times and probably raise your mph..when i stripped my stang without slicks i'd pop at about 4000 spin first and second to acheive 1.6 shorts,a 12.00 quarter@ 123mph......for s**** and giggles i lowered the launch rpm to about 3-3300 just spin 1st and feather into 2nd to get a 1.8 short,12.3 and about 117mph....slicks was an entirely different animal altogether

 

[MSMS3]

Darth,

I agree that something is holding the engine back in the second half of the quarter. Your 2.1's at 60 ft are about as good as you are going to get on stock rubber. I can't do that, at least not consistently. Hell, I get 2.2's most of the time and even some low 2.3's and am still trapping at 106 with almost the identical set up you have. I launch at about 2,300 rpm and feather the throttle, shifting at 5,500, knowing that I'm closer to 6,000 by the time I get the shift completed.

You should be hitting around 13.5 quarters, certainly 13.6's. I got one 13.4 but that was when everything went perfect and in 60 degree springtime weather.

Neither you nor I have a Dash Hawk or an AP, so it's a little hard to understand and diagnose why we are performing differently without better monitoring. I think your speculation elsewhere that you may have a fuel pressure issue could be right. Either that or something in the mapping in your ECU is pulling boost, timing or fuel back. I'm assuming that your boost gauge is telling you that boost is holding fine once you get up into third gear.

Are you able to flat shift 2-3? When I granny shift there, my times jump up almost 2 tenths, even with flatshifting 3-4 and 4-5. But I still end up trapping 104-105 with a slow 2-3 shift. Something's not right if you can't get at least to 102.

I'm wondering if your motor mount and the dampner might be so solid now that you are getting artificial knock being picked up by your knock sensor and that is pulling back timing. If vibration is being transmitted to the sensor, it could have a negative effect. Just a guess.

 

[Darth Vader]

Yeah I can flat shift 2-3 easily, especially with my short shift plate. I think, the mount issue is the only possible non-driver mod issue here.

I think, to be honest, that running out the back door in 4th is killing my MPH. The ECU is pulling back boost by that time pretty handily, since I'm over 6000. I think I have to shift earlier, to avoid tapping the limiter on the flat-shift or revving out the gears too high.

I'm up by a max of about 4 mph by the 8th and hitting 80 mph there so, I'm giving something away in the back half. Since I don't hear knock, the above 2 explanations are all I can think of.

I'm going to see if I can get one more day in before season end and run without the ETD installed. Then try to do the 5th gear finish with shifts closer to 5k than 6.

 

[MSMS3]

Yeah I can flat shift 2-3 easily, especially with my short shift plate. I think, the mount issue is the only possible non-driver mod issue here.

I think, to be honest, that running out the back door in 4th is killing my MPH. The ECU is pulling back boost by that time pretty handily, since I'm over 6000. I think I have to shift earlier, to avoid tapping the limiter on the flat-shift or revving out the gears too high.

I'm up by a max of about 4 mph by the 8th and hitting 80 mph there so, I'm giving something away in the back half. Since I don't hear knock, the above 2 explanations are all I can think of.

I'm going to see if I can get one more day in before season end and run without the ETD installed. Then try to do the 5th gear finish with shifts closer to 5k than 6.

Makes sense, especially given how much torque these engines make down low. When in doubt, shift early with this engine and pull back up the power band, it seems.

It would be really a crying shame to find out that the ETS was triggering your knock sensor. Stranger things have happened, though.

For what it's worth, when I run the G-Tech, it's showing that I actually hit the hp peak at 5,300-5,400 rpm, and the power just falls flat on its face at 6k. I think the DP makes its extra power in the midrange on the stock tune, building the power quicker and earlier. That's just my thought.

Good luck. Report back. I may try to get some fall track time here after the temps drop a bit. It was still 90 degrees here today at 5 p.m.

 

[Darth Vader]

I will also test the ETD by doing time/distance runs with a stopwatch, ETD on and ETD off.

The only other possibility is the fact I had 91 octane fuel in the car on race day.

 

[08cosmic3]

Shift @ 5500 and use 5th gear. There is NO power after 5500 on a stock ECU. Get an AP and power will not start dropping to 6000 rpm. I ran 13.97 @ 102.5 on a hot afternoon with just a cobb intake and test pipe on stock tires with 28,000 miles on them (bald). I ran 13.83 @ 103.6 with current mods in August on a hot afternnon with the bald tires. I was running a Stg1+sf93v105 map. I'm going back to the track in late october when the track opens for fun racing at noon on saturdays. I have new Hankook v12 tires which grip much better, harder to brake loose in 2nd. I'm running the Stg1+SF93v103 map now and it holds more boost than the 105 map. The temps are dropping so I'm hoping for 13.5

Alot of guys, including me, have come from high reving cars and tend to forget that this car is not. It make power from boost not RPM's

 

[socks]

what were track conditions the two times you went?

you may have a significantly more powerful car, but if you ran on a cool night the first time, and in the heat this time, your traps would suffer...

 

[Darth Vader]

no offense mac but, if you actually read my email, you'd see I refer to baro and humidity in the third paragraph. The air was better this time out, over last time.

This isn't my first rodeo, I've been drag racing bikes and cars for over 10 years and modding them for over 25.

My recent purchase of a Dashhawk and close inspection of the engine, via plug change and compression test, reveal no abnormalities. Thus, I can only conclude one nut is loose, the one behind the wheel. I'm going out tomorrow to test a new driving strategy with this car. I'll let you all know how it works out.

 

[Darth Vader]

Datalog of track time via DH shows the WOT table to be insanely rich... like 10:1 rich. No s*** it's a bit flat. I'm gonna throw a test pipe in there to lean it out further. This is with an AEM CAI and a CS DP for flow mods.

I did break 100, on the worst 60' time I've ever done (2.5) and a hopping second gear journey. It still whipped up 101.4 despite those driver-induced idiocies. I only got two runs in, it was pretty cold and traction was pretty bad. Run 1 was datalog only so, shift whenever. The other run was the 101.4 one and that was done with the shift light set at 5400 and powershifting. This shot the flare to 6000 and dropped the change to about 4k, which is pretty good.

More seat time and...a test pipe...are in order.

 

[onelsono]

y not just just throw a full TBE on it a good intake a fuelpump upgrade, a good tune, and throw sum slicks on it and run 12's? ull def be over 100 then

 

[Darth Vader]

Well...I already have an intake and a CS DP. I don't think I need an FP upgrade, since the car is pig rich at WOT and pressure shows over 1600. I like the stock cat back's tone and volume. I think the test pipe will snarl it up just about right.

This IS my DD so, I don't really want to mess with it too much. I want to run as well as I can on the stock tune. I can do any task with this car I want, it isn't about experience, or ability, or tools, or space. I've been building and racing cars for 25 years. At my age, I just pick and choose the stuff I want to do.

 

[MSMS3]

TBE ain't gonna do squat on this car on the stock turbo, compared to him just adding a test pipe to the aftermarket DP he already has. Stock CBE flows extremely well at this power level. The restrictions are all upstream.

OP has as good intake (about as good as it gets) and a fuel pump that's obviously still making him super rich even at full throttle and high engine load.

Yes, a little lean out with the test/race pipe at WOT under full load in the higher gears might be just what the doctor ordered.

These cars are just so damned hard to launch for many of us (at least me). What works one week under one set of track conditions is disaster the next week. Oh, yes, you can put DOT drag radials on to make a point, but you can't run around on the street with them (at least not very long).

Thanks to OP Darth for sharing. He's sold me on getting a DH and I'm shopping for one now.