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 Post subject: T-slot restrictors
 Post Posted: Sun Aug 28, 2011 12:59 pm 
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Hey All,

As you know I have been playing with that accelerator pump bleed. Well since adding the bleed, I have a hole when I am rolling into the throttle to launch rpm. The hole is non-existent when I go to the floor to hit the rev limiter for a t-brake launch, it just there when I roll slowly into the throttle while footbraking. I looked at previous logs, before the bleed, and there is a smaller hole there, but not enough to feel it. I have t-slot restrictions in there so I am starting to thing the proper adjustment would be enlarging the t-slot restrictions. It has .052 restriction. On my car the mains kick in around 2300 and the log shows it starts going lean about 1900-2000.

So what do you all think, t-slot restrictions or should I continue messing with the bleed and pump cam.

Thanks

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 Post subject: Re: T-slot restrictors
 Post Posted: Sun Aug 28, 2011 1:43 pm 
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IMO, i would just increase the acc pump restrictor a bit till it goes away... .052 is fairly basic size....Or what you may want to try is just turn the speed screws, say 1/4 to 1/2 turn more. That will show more slot and may get ride of your issue..

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 Post subject: Re: T-slot restrictors
 Post Posted: Sun Aug 28, 2011 1:48 pm 
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Remember, TSJs also control how the car acts on pit lane and the return road!! Hork with that and you'll likely wind up with something you don't want in those areas.

Maybe a more aggressive pump cam on the primary side would help, ie, working quicker early in the shot? Smaller pump bleed may help too but also may make it rich at the hit again?

That pump bleed is a double edged sword IMHO. Like I said before, they would probably be good for more MPG on a street/performance engine. Looks like it's going to take a bunch more testing to get it perfect though.

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 Post subject: Re: T-slot restrictors
 Post Posted: Sun Aug 28, 2011 1:51 pm 
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Well, I this hesitation happens when i am rolling into the throttle slowly, so I do feel it coming up the return road, that is why I am leaning toward a t-slot adjustment.

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 Post subject: Re: T-slot restrictors
 Post Posted: Sun Aug 28, 2011 2:11 pm 
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fourtenposi wrote:
I do feel it coming up the return road, that is why I am leaning toward a t-slot adjustment.


Are your AFRs confirming this and does it surge all the time or just hesitate slightly when the throttle is opened?

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 Post subject: Re: T-slot restrictors
 Post Posted: Sun Aug 28, 2011 2:15 pm 
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Yes the afrs confirm this, Its pretty much every time it gets into the rpm range. I think the accelerator pump was covering it up before, and now that I am leaning it out, it exposed the hole. It about wants to cut out.

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 Post subject: Re: T-slot restrictors
 Post Posted: Sun Aug 28, 2011 2:23 pm 
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Here is the log

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Here is a link to a larger pick

http://farm7.static.flickr.com/6085/6089641317_1c092f6e0d_o.jpg

The slower I roll through this rpm range, the worst it is.

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 Post subject: Re: T-slot restrictors
 Post Posted: Sun Aug 28, 2011 3:15 pm 
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Yup, I see what you mean. I'd try adding .005 to the TSJ to see how it reacts to that. If it likes it then you can add a another .003 until you get it where you want it. If you don't get any change then the IJ may need to be larger as well. :-k

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 Post subject: Re: T-slot restrictors
 Post Posted: Sun Aug 28, 2011 3:32 pm 
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Well decided to go out in play, Started out when up to a .063 tsj. It got better, but it was still there. So I decided to pull out the jet all together and see if it was still there. It now goes through that rpm range alot cleaner. If I roll through those rpms really slow, afr shows it goes to mid to high 14s. But if I roll into the throttle like I do when staging, is goes to the 13s. So seems like removing the t-slot restrictions did the trick. We see how she does at the track in two weeks.

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 Post subject: Re: T-slot restrictors
 Post Posted: Sun Aug 28, 2011 7:25 pm 
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On a side note, a cool thing about those weber blocks is that you can pull the e-tubes and disable the mains, This allows you to see exactly how the t-slot is delivering fuel. With the original t-slot restrictions and no e-tubes, it would would start to die at about 1900 rpms, with the restrictions removed,it carries it up to about 2400. You know, I am not a fan of who I got them from, but I really like these blocks.

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 Post subject: Re: T-slot restrictors
 Post Posted: Mon Aug 29, 2011 4:33 am 
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.005 smaller on the idle air bleed and readjust idle AFR. Thats how you richen the T Slot.
Put your .052 back in.


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 Post subject: Re: T-slot restrictors
 Post Posted: Mon Aug 29, 2011 6:02 am 
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I really didn't need to richen the t-slot, I need to extend the range in which it is in operation. Isn't that the purpose of the t-slot restriction?

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 Post subject: Re: T-slot restrictors
 Post Posted: Mon Aug 29, 2011 9:46 am 
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Bill, lowering the idle air bleed will extend the range of the transition circuit. Idle and transition circuits work on a balance of the idle jet, idle air bleed, transition slot size and position, and t-slot jet if any. The t-slot jet is not all about controlling the fuel or duration, it's about balancing how much air it bleeds back into the system as well. Try the .063 in the t-slots first and drop the idle air bleed .005 as Scott suggested.


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 Post subject: Re: T-slot restrictors
 Post Posted: Mon Aug 29, 2011 10:11 am 
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I will give it a try how it is and see what happens, then put the restrictors back in there and drop the bleed. See which one produces a better result.


Assuming that the fuel curve is where I need it to be without the t-slot restrictors, Is there an advantage to making the correction with the IAB vs the t-slot? I have driven the car yet so I don't know if I have created other issues, but removing the restrictors allows the car to come up clean to the launch rpms.

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 Post subject: Re: T-slot restrictors
 Post Posted: Mon Aug 29, 2011 3:15 pm 
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Do you happen to run a TPS so you can see where you're at in relationship to your slots? You might have an issue with the length of the slot as well.

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