Question For The Guru's--Dumping Boost
 

After running today at Carlsbad with a new chip, I ran into a couple oddities I never had before. Out of my six runs today, I had trouble in three of them. The first was towards the end of a run as I shifted into 3rd, the engine shut off and threw a SES light. I just through it into neutral and it started back up, no problems back to the staging lanes. Then two runs later, between the 1-2 shift, the boost dumped and I had to get out of the gas completely and then the boost came back. No SES light. It did this one more time at the 1-2 shift and just got out of the gas and the boost came back. Only difference between the runs and the final two was I dropped pressure in the ET's to 16psi. It sounds like an over-rev between 1-2 shifts. I didn;t get a chance to bump up the pressure to test again. My mods are in the signature. Any suggestions would be appreciated.

By the way, I finally broke into the 12's today!:D

You hit the rev limiter and the PCM dumped the boost for when it fell on it's face on the 1-2. Easy fix, just unplug the silinoid.

But the SES light and killing the motor going into OD has me stumped.

Why are you going into OD? Are you turning mid 11's?

Sorry, I meant into third.:rolleyes: I have a bypass kit installed, so how can it dump the boost???

You didn't do something right then when you installed the bypass kit... Unplug the solenoid and see if you can simulate the same thing, and see if it falls on it's face. If it still falls on it's face, something else is wrong...

But, still going into third... I would like to see what Sal has to say.

A couple of months ago, right after changing a chip, my eng shut down in 2nd and then on another run-in 3rd. Each time, it would restart OK. Turned out to be a 'connection' problem with the chip--not a 'cleaning' problem(I knew this because I installed another chip that night an no problem with it.) Mine did not throw a SES light though???

Dan

It sounds to me that the shift point is too close to the rev limmit. The tarnsmission can overshoot the shift point depending where in the calculation loop it happens to be when your motor gets to the shift point. If you are going 0-60 mph in 3 sec you are going 0-40 in 2. That gives 1000 rpm to 5500 rpm in 2 or about 2300 rpm per sec. If the computer misses the shift by just .1 sec the motor overrevs 230 rpm. These are all round numbers but you can get the idea.

Andy

Reclean the contacts and reinstall the chip. Make sure you pull down evenly on both sides of the duct tape before sticking it so the chip isn't twisted to one side or the other. If you don't have duct tape holding it in place then get some.

i had the same problem friday nite w/ boost dumping. where should i unplug the solenide (sp?) at? will that fix the problem, or do i need a bypass kit?

FastAsL,

this pic is from ChIcKeNeArS:


https://www.f150online.com/galleries...1173-13983.jpg:cool: :cool:


That's all you need to do..I had the same problem last week....JR

can anything be damaged by doing this mod?

Chris,
as far as I know there in no problem...lots of guys do it, some for close to a year......you can do a search now, try that for more info......JR

ps: you have mail......:D

thanx for the help JR

ps. you got mail.

Thanks for the replies. One more question...If I am hitting the rev-limiter, how can the computer dump the boost with the bypass kit installed??? Thanks again.

i dont know this for sure but i will guess
when you hit the rev limiter your rpm drops a few hundred right? when your rpm drops its similar to letting of the gas right? and when you let off the gas, what happens??? you loose your boost.
that may be it but i dont know for sure

Hey Doug, congrats to be hitting the 12's!!! What was your total time (I must have missed it).

Anyways, like Lightning Boy mentioned above, it's possible you installed the bypass kit wrong. If not, try simulating it as much as possible again(safely), but this time pull the bypass kit off and just leave the solenoid(sp?) un-plugged. Also, do check for connection issues with the chip. It's possible that your truck is creating so much force from a launch that you jolted the chip loose!;) Good luck, hope you can make it this Sunday. Should be loads of fun!