Boost at launch question

[SeattleSy#1255]

What factors play a role in the amount of boost at launch...I can't get anything above 5-6 lbs, and that is with throttle floored...It's impossible for me to drive thru my brakes. I'd like about 9-10 off the line as i think traction becomes an issue over that...What factors or things i can check/fix to increase my boost at the line?

TIA

 

[Will_in_China]

Re: Boost at launch question

What factors play a role in the amount of boost at launch...I can't get anything above 5-6 lbs, and that is with throttle floored...It's impossible for me to drive thru my brakes. I'd like about 9-10 off the line as i think traction becomes an issue over that...What factors or things i can check/fix to increase my boost at the line?

TIA

Is it pulling timing on you?
Stock T/C?
Restricted intake and exhaust/cat?

-Will

 

[ttdolson]

....

 

[SeattleSy#1255]

stock exhaust with deleted mufflers...

stock intake

stock T/C

Mods..are the normal....

walbro fp
ultimate
AFPR
others...

Fuel pressure adjustment doesn't seem to make a difference in what i can build at the line...I took out the stock crossover intake to see if that would make a difference, but still can't get past 5-6...


Why do i see some people saying they can launch there trucks with 15psi (not that i want to) but, why are soom 5psi and some 15psi...and there all stock?

 

[Will_in_China]

How's the CAT?

Try unhooking the crossover tube for the intake and do a short spool and put it back in...

I would guess it's timing though.
How much advance are you seeing on scantool?

-W

stock exhaust with deleted mufflers...

stock intake

stock T/C

Mods..are the normal....

walbro fp
ultimate
AFPR
others...

Fuel pressure adjustment doesn't seem to make a difference in what i can build at the line...I took out the stock crossover intake to see if that would make a difference, but still can't get past 5-6...


Why do i see some people saying they can launch there trucks with 15psi (not that i want to) but, why are soom 5psi and some 15psi...and there all stock?

 

[InvisiBill]

How exactly are you prepping for the launch? Are you just holding the brake down and flooring the gas?

Another thing... I've never heard it mentioned here, and it may not even apply since you have an Ultimate, but there's a page in the manual that describes some of the extra features and characteristics of the turbo system, and it says that boost is cut when the gas is floored while the brake is pushed down.

 

[SeattleSy#1255]

will n denver,

you want me too look at the spark advance on my scan tool, is that what you are saying...other than that, i'm unfamiliar with timing??? That cat seems to be fine!

Invisible,

I have read that too, though I don't think this is the case here...

I'll do the Tod A. manuever, and slowly throttle it to build boost to see what i can get too...by the time i'm at 5-6psi, its floored...like i said, its impossible for me to creep through my brakes.

 

[JustBeachin]

I thought the same thing.....ah, I can't leave with too much boost. I was right. I gave it too much boost, and I couldn't leave.

 

[FLSY2730]

if any body can luanch at 15lbs without massive wheelspin, i would like to see that.

 

[SeattleSy#1255]

.......LOL......


i'm not looking for 15lbs....just more like 8-10----

i want to be able to break my neck with wiplash...i know there is more in this thing with more boost...but 5-6 is not much compard to others i have seen and felt!

 

[InvisiBill]

Do you have any leaks anywhere? Loose hose or something? Try the bicycle pump trick... Any boost problems at other times?

Mine has a K&N in the stock airbox and a hotwired Jabsco, and I've never had it stop building boost before a launch. It just keeps going until it's creeping on me...

 

[SeattleSy#1255]

no no no, no leaks or anything...all vacuum lines etc. are redone...Its been like this since I bought...funny thing is that it seems about 50% of the syty's can only reach 5-6psi at launch (stock) and others can build boost until brakes can't hold...

In terms of timing i reviewed a few datamaster files and my SPARK ADVANCE seems to be around 13-16 right before i launch with boost built between 5.1-6.1psi...<------------------is this a factor or related to boost at launch?

 

[Mephisto]

i just now started having the same problem... i just installed that replacement bolt that goes in the manifold so you can hook up the boost gauge air hose, and now i cant get more than 5lbs on a launch, and no more than 10lbs when driving. why would swapping that out cause this?

 

[SeattleSy#1255]

COLD WIND,

that is something completely different...you now can only get base boost which is 10lbs...

I get normal boost, just can't launch with more than 5-6...

for you, i'm guessing you created a leak somehow with vacuum. All i can say is redo your vacuum line...you may not have messed with them, but just opening the hood could mean problems for those POS!

 

[Christian Dionne]

if any body can luanch at 15lbs without massive wheelspin, i would like to see that.

Jack, I used to launch between 12 and 15 psi and cut my best 60' times.

Stock turbo, TC, engine, drivetrain etc...

Nitto 450 All weather tires with 1.74 60' reguraly.

I know that isn't quite as good as yours

I'm sure that much boost in your combo would be rediculous.[/quote]

 

[Will_in_China]

Screw "Seems Fine"
Rip that fuckin' thing out... It is a stocker right?
You don't need it anyway.
While you are at it, get a dump tube...

If it ain't the stocker, this message will self-destruct under high boost in 5 seconds...

will n denver,

you want me too look at the spark advance on my scan tool, is that what you are saying...other than that, i'm unfamiliar with timing??? That cat seems to be fine!

Invisible,

I have read that too, though I don't think this is the case here...

I'll do the Tod A. manuever, and slowly throttle it to build boost to see what i can get too...by the time i'm at 5-6psi, its floored...like i said, its impossible for me to creep through my brakes.

 

[Tooky]

For the record I have a stock Sy with new Viper HX tires and I can only build about 5 PSI on the launch before it creeps or the rears start scraping. I launch at about 3-4 PSI at the dragstrip and I cut 1.7 60's. Here are my 3 best 60's from my last trip to the dragstrip (April 30th).

1.777
1.798
1.776

I did notice if I spun the tires a fair bit, my 60's actually improved. Next time I go to the track I am going to try launching with even more boost and see what happens. I guess I can say I haven't reached the point yet, where the tires are spinning so much that the 60's get worse, so there must be room to improve.