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dc772 May 30th, 2017 11:14 PM

Nitrous and drag racing help needed-just beginning
 
Hey guys, Ive got a few questions on how to run my car and get the most out of it. I did a lot of work to it this winter and began racing this spring. Right now the basic set up of the car is 255hp/297tq and then a 100 shot on top of that. Im running an auto with a 3800 stall and a jmodded valve body, 3.73s, and a big and little set up with MT et street radials 275/60/15 (I know the tire is a little too tall for the 3.73s). Ive got upr sub frame connectors, upr rear control arms, upr k, and orange konis and eibachs. My window switch is currently set to spray 3k-6krpm.

-So far the car has run a best of 13.2 at 104, and with the 100 shot a 12.3 at 117.

-My best 60ft ever was 1.89 and most of the 60's have been 1.91-1.95.

-Im launching the car on the footbrake between 2250 and 2500 depending on what the track holds that day.

So here's where I need help Id like to get the car in the 12s Na and in the 11s with the 100 shot before I go to the 125 shot. I think my 60fts can still be improved and I am at a loss on where to start with knocking them down a bit. The last time out the MT's consistently trapped higher every pass as I aired them down from 22-18lbs over 4 passes. I have a feeling that the car is bogging out of the gate and resulting in the "just okay" 60ft times and its taking more time for the car to reach 3k for the spray to come on when Im running on the bottle. If anyone has some insight on how to knock down these 60fts a bit Id really appreciate it.

Additionally, a friend/fellow mustang racer I know told me just to set the window switch to 2k so it sprays on my launch, and that it wont hurt anything since it just a small shot. Realistically with the way the car launches it wouldnt be sprayed below 2500 ever so I think that when Im on the bottle this might be a good set up to get out of the hole quicker. Im just wondering if you guys have experience with it and want to make sure its "okay" to do.

-Any help is appreciated. Im just starting out and learning as I go and trying to soak it all in. I did search these things but didnt come away with any solid info. Thanks, Dan

RDY4WAR May 30th, 2017 11:27 PM

I wouldn't set the window switch lower. Keep it at 3k. Since you're not able to footbrake it at your stall speed, I wouldn't try to footbrake it. Just snap it WOT off idle and the let the converter flash.

A 4.10 rear gear would help a bit with those sluggish 60ft times but your issue here is just power. You're probably making about 340whp on the 100 shot. Assuming a full weight 03 GT with a full tank of gas and driver, your racing weight is probably at best around 3500 lbs. I think a 12.3 is about as good as it's going to get. Like I mentioned, a little better gear will help you some off the line. Past that, you either need to drop weight off the car or add HP.

What converter are you using and does it have anti-ballooning plates to hold up to the nitrous?

dc772 May 31st, 2017 12:55 AM

The car is around 3300 lbs at race weight with me in it (Im 280lbs). Im using a multi disk circle d converter. Im unaware of the exact build specs as I bought it from someone that had it specd then changed their route, they were running a blower. On the 100 shot the car made 340/438, I have the 125 shot tuned as well but wanted to see what I can make of the 100 shot first. I was wondering if I was missing something with my launch, or just plain missing something that would be able to help out my 60fts. Im sure a good cam would be the best next step, but I am really leaning toward coyote swapping the car in a year or two, and I dont see the point in throwing more money at the 2v. Not bashing the 2v, just economically doesnt make sense right now. Unless I decided to forge the motor, do a direct port, and do heads and cams too.

69fastback May 31st, 2017 09:05 AM

Nitrous converter, and blower converter are set up totally different. Have you inquired with Circle D to see what a re stall would cost? That alone is key to a auto car getting out on the 60'. I ALWAYS spray it on the hit. My car shaves almost a full .4 off the 60' when leaving on the bottle.

I think a large part of your answer is in the converter.

blownstang May 31st, 2017 09:14 AM

Try a 26" tire. I have a Circle D 3600 with a 3.55 gear. I run 16-17 psi. 60' is essentially the same between a 275/40/17 Toyo drag radial and 275/50/15 Hoosier drag radial. 1.63-1.65. I foot brake to 2600 and then hammer it. Is the rear end suspension adjustable? If so might want to double check how it's set. If not, good! One less thing to have a headache about. Where is the trans shifting? Set it as close to 6500rpm as you can and up your spray rpm cutoff.

GBPackerFan May 31st, 2017 09:52 AM

Have you thought about a trans brake? Launch RPM is where the issue is. I would not lower the window switch RPM. Your problem is launching at too low an RPM. You probably are bogging at the line. You should and can be in the 1.6x range for 60fts.

It's all about the 60ft man. Especially with an Auto that does all your shifting.
@JayC can help here. He had a very good setup with his nitrous and can offer some good advice.

RDY4WAR May 31st, 2017 10:03 AM

Quote:

Originally Posted by dc772 (Post 11848425)
The car is around 3300 lbs at race weight with me in it (Im 280lbs). Im using a multi disk circle d converter. Im unaware of the exact build specs as I bought it from someone that had it specd then changed their route, they were running a blower. On the 100 shot the car made 340/438, I have the 125 shot tuned as well but wanted to see what I can make of the 100 shot first. I was wondering if I was missing something with my launch, or just plain missing something that would be able to help out my 60fts. Im sure a good cam would be the best next step, but I am really leaning toward coyote swapping the car in a year or two, and I dont see the point in throwing more money at the 2v. Not bashing the 2v, just economically doesnt make sense right now. Unless I decided to forge the motor, do a direct port, and do heads and cams too.

I wouldn't worry about any nitrous specific cam with the small shot you're spraying. Your problem is that blower converter. You need one spec'd for your nitrous motor. Have you data logged any runs to see where it's actually stalling? A 3800 stall spec'd for a blower car won't stall at 3800 behind your small nitrous shot. You're realistically probably only stalling at 3000-3400 unless your engine happens to coincidentally mimic the torque curve of a blown engine.

69fastback May 31st, 2017 10:03 AM

Is the car dead hooking?

I can tell you my Neal Chance converter was setup for someone else's car too, and I was cutting 1.40 60's. After I sent it back to get setup for my car, it's down to a 1.29.

dc772 May 31st, 2017 09:02 PM

Thanks for the input guys, as far as the converter I am 99% sure it is not spec'd for a blower car. From what I was told it was an off the shelf 3800 that the guy bought, he did not spec it, simply just put an off the shelf converter in his blower car. I do have the build numbers of the converter so Ill call and try to get the exact specs from circle d. I havent data logged the car and now that you say that I will do that on my next trip to the track. But I feel like the car is stalling at 3800, from messing around with it on the street and having my friend/mechanic drive it we both feel it is dead on around 3800. Even at the track you can feel the lock up. I would try a 26 in tire but I just bought these 275/60s so Im gonnna just have to stick with them. The car is absolutely dead hooking. it hasnt spun yt with the MT's. The lower rear control arm is solid, the uppers are adjustable and set the correct pinion angle (no whining either). The car is bogging at the line, which is certainly the largest part of the problem. So maybe launching off idle and letting it flash then take off will keep it from bogging like it does when I foot brake the car. The rev limited for drive is set at 6050. Thats just where my tuner put it, so Im guessing I need to set that up to 6500 and set the window switch for a 6450 cut off? I appreciate all your input and help guys, Im 20 and just getting into it and I dont have anyone helping me out directly so the advice is always appreciated.

RDY4WAR May 31st, 2017 09:21 PM

Do you have a dyno sheet with your power curve?

69fastback May 31st, 2017 10:27 PM

A converter is more than a stall. RPM recovery on shifts and several other factors play a part. A properly tuned converter goes a long ways.

And spray that shit on the hit.

And in case you're unsure, dead hooking is bad and wheel speed is tha shit.

dc772 May 31st, 2017 10:46 PM

I do have a dyno sheet, Ill take a min and post it up. I know dead hooking is bad, I knew the car was going to dead hook so I started my tire pressure out at 25psi and still didnt spin. Would you guys recommend trying 30psi or just running the basic 18 psi and dead hooking. Im going to set my window switch to 2500. Next time Ill try a footbrake launch at 2500 and then a idle launch and see if it flashes quick enough for it to spray right off the launch.

-Last thing, in my tuner (sct x4) it is listed as "max drive rpm" so I make the connection that this is where I set the shift point. Its currently set at 6050, as blownstang said should I set that to 6500? Just want to make sure that is the absolute correct adjustment to make.

dc772 May 31st, 2017 10:55 PM

1 Attachment(s)
First try at uploading my dyno sheet. Sorry its kinda hard to look at, we didnt take the time to separate and print out the runs, but this is all I have. Also my tuner only took the car to 5500 so Im still unsure whether I should make that adjustment in the tune for the max drive rpm

RDY4WAR June 1st, 2017 12:44 AM

Quote:

Originally Posted by dc772 (Post 11848929)
I do have a dyno sheet, Ill take a min and post it up. I know dead hooking is bad, I knew the car was going to dead hook so I started my tire pressure out at 25psi and still didnt spin. Would you guys recommend trying 30psi or just running the basic 18 psi and dead hooking. Im going to set my window switch to 2500. Next time Ill try a footbrake launch at 2500 and then a idle launch and see if it flashes quick enough for it to spray right off the launch.

-Last thing, in my tuner (sct x4) it is listed as "max drive rpm" so I make the connection that this is where I set the shift point. Its currently set at 6050, as blownstang said should I set that to 6500? Just want to make sure that is the absolute correct adjustment to make.

Start at 25psi, continue to raise the tire pressure until it spins. Set it 2psi below that point.

This video shows very well the importance of wheel speed off the line.


Quote:

Originally Posted by dc772 (Post 11848937)
First try at uploading my dyno sheet. Sorry its kinda hard to look at, we didnt take the time to separate and print out the runs, but this is all I have. Also my tuner only took the car to 5500 so Im still unsure whether I should make that adjustment in the tune for the max drive rpm

Thanks for the dyno. It's a shame that the dyno doesn't go any higher. Your shift point at 6k may be on point. I'll plot your curve here shortly and see about what you should be running. You're running a 4r70w, correct?

dc772 June 1st, 2017 01:07 AM

I am running a 4r70w, I appreciate you doing that for me. As far as where the shift point is set, the tuner told me he had a "built trans" tune that he wanted to try so we loaded it up and road tested it and it seemed pretty good so I havent messed with it. Video was great too, now I thoroughly understand what Im aiming for here and can see what you guys are talking about. Thanks a lot-Dan

RDY4WAR June 1st, 2017 01:15 AM

Quote:

Originally Posted by dc772 (Post 11849073)
I am running a 4r70w, I appreciate you doing that for me. As far as where the shift point is set, the tuner told me he had a "built trans" tune that he wanted to try so we loaded it up and road tested it and it seemed pretty good so I havent messed with it. Video was great too, now I thoroughly understand what Im aiming for here and can see what you guys are talking about. Thanks a lot-Dan

Question: Are you locked out in 3rd gear?

If you're not locked out in 3rd gear, this is what my math is coming up to.

60ft: 1.49 @ 45.12 mph
1/8: 6.85 @ 99.30 mph
1/4: 10.92 @ 120.11 mph

This is assuming a 3800 stall converter that is spec'd to your engine with a peak 2.2x torque multiplication and non-locking throughout the run with 12% slip and spraying off the launch. Weight is 3300 lbs, drag coefficient is guessed at around .038 with 20 sqft of frontal area, (probably wrong but close enough) rear gear of 3.73, rolling resistance of constant 38.4 lbs, trans gears at 2.84 / 1.63 / 1.00 / .70, and a flat track with no wind.

For the 125 shot, I get...

60ft: 1.46 @ 46.04 mph
1/8: 6.71 @ 101.37 mph
1/4: 10.69 @ 122.26 mph

Ideal shift points...

1st to 2nd shift: 6200 rpm
2nd to 3rd shift: 5800 rpm

Froush June 1st, 2017 07:11 AM

10s with 340 hp at 3300 lbs. Ummm......no. he would be lucky to break 11s. This is why people think their cars are making more power or can run faster than they can.....guys with "calculators" that are grossly off

RDY4WAR June 1st, 2017 07:54 AM

Quote:

Originally Posted by Froush (Post 11849177)
10s with 340 hp at 3300 lbs. Ummm......no. he would be lucky to break 11s. This is why people think their cars are making more power or can run faster than they can.....guys with "calculators" that are grossly off

I'm not using a calculator. I'm using physics. It's very possible and people do it all the time. My scenario is assuming an ideal setup with a properly matched converter, good wheel speed, etc... I'm using basic newton's laws of motion using the force created by the car at every 100 rpm step in each gear with converter data figured in to get a more accurate torque output. Again, this is assuming a properly spec'd converter for his combo. The OP does not have a properly spec'd converter. He has a shelf converter that's most likely nothing more than a stock style unit that's been modified to stall higher. What he needs is to contact Circle D for a properly matched 9.5" converter and get Silverfox or Lentrch to build him a valve body to work well with that converter.

The reality with his car is that it's not actually making 340 hp. That's just what the dyno spit out because it doesn't know any better. You can't dyno an auto car and expect an accurate reading because of the way the dyno reads torque. The only way you'll get an accurate reading with an auto is if it's completely locked out during the run. That's why I asked if his car is locked out in 3rd gear. If so, that changes everything and I've got to go back and redo my math again.

He'll, just look at NMRA Factory Stock and Coyote Stock. These guys are deep in the 10s with less power to the ground than the OP and pretty much stock long blocks.

Froush June 1st, 2017 08:10 AM

Go hit a drag strip dude. 340 hp at 3300 lbs (probably higher race weight) says low 12s high 11s to real life and many reputable calculators

http://i1096.photobucket.com/albums/...psfuwxhxen.jpg

---------- Post added at 08:10 AM ---------- Previous post was at 08:05 AM ----------

And coyote stock make more power to the ground than op.....and they have them in very light fox bodies. You aren't running your imaginary numbers with 340 hp

RDY4WAR June 1st, 2017 08:29 AM

Quote:

Originally Posted by Froush (Post 11849193)
Go hit a drag strip dude. 340 hp at 3300 lbs (probably higher race weight) says low 12s high 11s to real life and many reputable calculators

http://i1096.photobucket.com/albums/...psfuwxhxen.jpg

---------- Post added at 08:10 AM ---------- Previous post was at 08:05 AM ----------

And coyote stock make more power to the ground than op.....and they have them in very light fox bodies. You aren't running your imaginary numbers with 340 hp

That stupid online calculator is extremely vague and very wrong. It's also assuming you're giving it crank HP of 340 which isn't correct. It says the car will go 107 mph when the OP has already stated to have gone 117 mph. My math says he'll go 120 mph with a properly matched converter. There's also the margin of error with my drag coefficient which I'm assuming is a tad off. That'll only make a difference on the back half of the track though. The OP's issue is getting off the line.

I've been around drag strips since as early as I can remember.

Also, the Coyote Stock racers aren't that much lighter. They're 3000 lbs for 2014 and older sealed engines and 3200 lbs for 2015 and later. The aerodynamics is pretty comparable. They're making 370-390 whp at 3200 lbs and are knocking on that 9 second door.

Drag racing is so much more than just power.


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