1/4 mile time not so hot, ways to improve?

[Kazuya1274]

Finally got my car to the track tonight. Although I did pretty good, I was really hoping for at least a 13.5, instead I got a 13.7 (wanting to eventually dip into the high 12's). My 60' times were horrible, over 2 seconds. Not sure you can do much more with 15x6 wheels with V rated tires. The car seems to lose power after the 5000 rpm mark, so I think I am starting to lean out at high rpm. The plugs show it, too. I started with 12 degrees timing, then went to 14, then 16 (NA distributor). My mph dropped each time. First run was 104, then 102, then 101. What kind of timing are most of you running on your cars? My best run was with the 12 deg of timing, but that was the first run. As the temperature got cooler, I should have been running faster, but everytime I messed with the timing I got slower. My last run was a 13.8 and I got the 60' time down, but only hit 101 mph.

 

I'm not the most experienced drag racer (never had anything worth drag racing!). I know I can do better though. The car's specs are:

81 280ZX, 83 turbo block, TO4B/T3, 13 psi, Tial wastegate, 2.5" exhaust, Turbo injectors, intercooler, Bell FPR, stock fuel injection.

 

Questions are:

Would 370 cc injectors help me on the top end? Because the car pulls hard, then kind of levels out at high RPM.

 

Anyone have some pictures of a cold air intake setup? My air filter is currently where the A/C compressor used to be, so I know it is not getting enough cool air.

 

Would new suspension help any? I'm running on some very worn out springs & struts.

 

I know some of you guys with the stock T3 are getting in the 12's, so why can't I? Or am I not running enough boost??

[evildky]

I'm not a big drag racer either so my input is limited,

the tires: slicks or dot slicks will help get those 60 footers down

front tires: smaller, lighter, narrower would help a bit

diff: you got an open stocker? a LSD really helps but not if the tires can't hold it

Gears: stock 354 :1 ? taller ratio will get you off the line quicker

AFPR: get that pressure up and keep it from leaning out on the long end

I/C: spray the Intercooler down with a mist of Ice water between passes

add lightness: if it doesn't make the car stop go or turn, take it out

[Guest bastaad525]

Personally I dont think the 370cc's are the magic key that will unlock faster times, at least, not on their own. While it is very possible that you are running lean on top with the stock injectors and FPR, you are probably running FASTER because of it. When I dynoed with my most recent setup, on the first pulls I was running much leaner, at almost 14:1 a/f, and as I used the BEGI FMU to richen up the fuel curve to get to that mid 12:1 area, power dropped off significantly, from 20 to 40 hp/ftlbs lost across the entire rev range. So in all probability, getting a richer mixture will most likely slow you down, but, better to go slower than not go at all due to broken/blown/melted parts. As far as feeling like it's tapering off after 5000rpm, that is pretty normal for the L28ET... I'm not sure how the T3/04 affects this, but I know with the stock T3, power usually peaks in the 5000rpm range... well at the stock boost levels it peaks at like 5500rpm, but I've noticed that, at least on my own setup, that as boost levels and power levels go up, the HP peaks lower and lower in the RPM range... my hp peaks at 4600rpm!... but does stay almost flat up to about 5100rpm. I have seen this on other similiar setups as well. Blame it on the stock head or cam. Also, blame it on your exhaust. With that turbo you REALLY should be running 3"mandrel all the way back... a smaller exhaust will choke the turbo and limit your top end power.

 

As far as needing the 370's... well, I know that the FMU will allow you to run a lot of fuel thru the stockers, up to a point. With the stock turbo pumping out 12psi I was able to get it to run SUPER rich at about 65psi of fuel pressure. With a T3/04 though you're moving a lot more, and denser air (more efficient turbo), so you'd most likely need quite a bit more fuel, requiring even higher fuel pressure. A lot of people disagree on this but the general ballpark figure for what is considered the maximum 'safe' fuel pressure is around 80psi, though some say that you can get up to around 100psi 'safely'. If you do a search for topics using my user/screen name you'll find a LOT of recent topics regarding the FMU and it's abilities and limits, as well as one particularly useful post with lots of math equations that can help you easily determine ballpark #'s for how much fuel you need for x amount of power or how much fuel pressure you need etc.

 

That all being said, I do think that an injector upgrade goes hand in hand with the upgraded turbo. Actually, a few guys have recently mentioned that even the 370cc's on their own can run a little lean on top when running high boost or a hybrid turbo, so you will most likely still want to run your FMU with the 370's to get a little extra fuel on top. And, though running richer will slow you down, the ABILITY to run richer of course opens up that other most fun counterpart, higher boost! With 370's AND the FMU, you have the capability to run a LOT of fuel on top and support a LOT of power.

 

Most importantly, you need to budget for some dyno time with a wideband. Or get your own wideband O2 sensor. Once you get this modified it's just not worth taking risks with your investment... if you don't already have one at least get a fuel pressure gauge, you can do a 'Home Depot Special' for around $10. That way you can at least get a decent idea of what the FMU is doing and better tune it using some of those math equations I mentioned earlier. I used these for a baseline and when I dynoed my baseline was just about spot on.

 

 

The worn suspension might be helping your times... soft rear suspension allows a lot of weight transfer to the rear providing better traction on the rear wheels... I might be wrong about if it actually provides faster or slower times, I really have no idea, but I know it will help with better traction when launching.

 

Getting your air filter out in front of the radiator support to get cool fresh air will probably help a bit.

 

60' times make a LOT of difference in your ET's... your trap speed is good as is and I'd think 104mph, a good 60' could get you lower 13's.

 

And anyways, who is running 12's with the stock turbo in a 280zxt chassis? I know there are guys doing it in 240's... not doubting it just curious who pulled it off. I do think that YOU can get your car into the 12's with that turbo, more boost and a good a/f ratio, maybe even with bad 60' times

[Garrett76Zt]

geez your fingers must have huge callouses on them!

[spork]

The fastest my 280zxt went on a stock turbo was 13.3 @106.(18-19psi on street tires)) My T3/TO4E hybrid got me to 12.3 @ 112.8 (25psi on slicks) and with any luck I'll have the new T-61 in this weekend and I'm looking for low 11's. As far as the fuel issue...buy, borrow, steal, rent a wideband. Anything else is just a guess.

[Brad-ManQ45]

What RPM's were you leaving the line at?

 

I'm not a fan of the stock ECU and am planning to go MSII or UMS in the future with biggeer injectors in order ot hit 6K rpm reliably.

[Guest bastaad525]

geez your fingers must have huge callouses on them!

 

 

 

So I give detailed answers.... leeme be! Hey I WISH I got answers like that when I ask these kinds of questions!!!

[Guest De Schmaydee]

.....i think you are doing one hell of an incredible job doing 13s @ 13psi....i dont know of anyone else doing that in a zx @13psi..... ..s

[Guest Zcarsmakemyheadhurt]

Well I am a drag racer so I am inclined to answer as well as I can. First off what is the story with the fuel pump? I don't see that you have one in your list of specs. If it isn't get one pronto. Your FPR isn't doing a thing without it and get a fuel pressure guage mounted where you can see it "on boost". What are you running for gas? You usually get more MPH by bumping the timing but only when you have a fuel that can keep up with the engine speed. I would go at least 100octain in a boost only motor also are you checking your timing after 3000rpm? Between 24-30 is where the sweet spot is. If you car is intercooled you should be able to pull of 16-18psi on race gas and as for the 320's I usually don't like larger injectors on stock EFI but some people pull it off. I would probably look into a additional injector controller or better still a standalone EFI system, I know I sound like a broken record about those things but think about it. Your turbo upgrade isn't working anywhere near its peak flow numbers and for sure you can use more injection controll along with timing. See if you can find some G-60 Mcquery tire for those wheels as long as you have a clutch. Go for it.

[cygnusx1]

Here is a way to improve your 1/4 mile times.

 

http://www.ratsun.com/videos/9.35.mpg <---This belongs to a HybridZ member.

[akeizm]

The fastest my 280zxt went on a stock turbo was 13.3 @106.(18-19psi on street tires)) My T3/TO4E hybrid got me to 12.3 @ 112.8 (25psi on slicks) and with any luck I'll have the new T-61 in this weekend and I'm looking for low 11's. As far as the fuel issue...buy, borrow, steal, rent a wideband. Anything else is just a guess.

 

Out of interest, are you running modded internals to be running @ 25psi?

[Kazuya1274]

Thanks for the responses guys. Looking back on it now, I don't feel too bad about the time. There was a Camaro SS running at the same time I was that I would have spanked had he lined up with me (his best was a 13.9, but he was mostly in the 14.2-4 range!), so I do think my first track experience was pretty good. However, I know I have barely tapped the potential of the car, so I'm using this time now to make some improvements to the existing setup. I will upgrade to 390cc eclipse injectors for now. We (I didn't adjust the thing, my friend did!) have had good luck moving the AFM gear to lean the mixture down at idle. I am also going to get a 60 mm throttle body, mildly port the head and intake, and go with at least a 3" exhaust (the downpipe will be 3"). I've heard time and again how much difference a 3" exhaust makes on a turbo car, but I was reluctant to go past 2.5" because of the limited space on the back of the T3/TO4 turbine housing. However, this time I am going to squeeze that 3" pipe on there somehow.

 

To zcarsmakemyheadhurt, yes I do have a Walboro 255 lph fuel pump. I do tape the fuel pressure gauge to the windshield as well, but I need to do that more often that I have been. As for fuel, I run 93 octane in the car. The reason it is only 93 is because I want to keep the car as streetable as possible. Guess you can call me a "run what you brung" kinda guy. You are also right about the timing numbers that 24-30 is the sweet spot, which is where my best run was at. I do agree with those that say an aftermarket ECU is the way to go. Although I question whether that alone is going to give me any significant horsepower gains, I do know it will give way better tuning parameters, and get rid of intake restrictions like the AFM and all the junk on the intake manifold.