I did not originally think much of this mod but I figured it would be pretty easy so I would go for it. I went strictly off the voltage from my multimeter to determine how much to grind off. Stock voltage was 4.2 on my car. It took quite a bit of material removal to get to 4.6, which is where I stopped. I then had someone floor the gas pedal from in the car to make sure the cam was hitting the stop I just ground down. It wasn't even close! It was not even reaching where the original stop was located!

Pushing the gas pedal down I could her the cable bottom out with my foot only about 80% to the floor. I traced this sound to the traction control mechanism. I don't know why the hell there is another mechanical stop in the traction contol , but there it was. Grinding the stop inside the traction control was a PITA , but after I was done, I could finally hit WOT.

I feel this may have been a fairly significant mod, as it was more than just a tad of opening I picked up. I felt a SOTP difference at WOT, but I'm anxious to get to the track. I had some concerns about trap speeds with my car earlier, and I hope to see a difference.

The point of this post is that in my opinion, do not ignore this mod, especially if you have traction control. The throttle cable was tight and pulling from the start of stepping on the gas, so don't think adjusting it was called for.

If anyone has any relavent experience or feedback on this mod, I would be interested to hear it. I know plenty of people have done it, and I've searched and found many references , but I've not found many results, track,dyno or SOTP. I orginally figured that the last little bit of throttle blade travel might not make much difference, but in my case I think there might be something

 

hey where did you get your references for this mod. I have never even heard of this mod. post some more info ps

 

I did the bump stop mod and felt a nice difference in the ***-meter... car chirps the tires harder when shifting into third.

The bump stop mod allows your TB blade to open closer to 90degrees then where it is right now. Check install university for instructions.

 

cool thanks for the info man

 

never heard of having to grind more then just your TB's bumpstop, sounds to me like you throttle cable needed to be tightened.

 

how do you know if you need to do it? ive been hooked up to autotap and efilive, and i think it said i was at 100% throttle....so do i still need to do it?

 

no, thats your open at 100% of the factory settings, meaning if your throttle only open to 78degrees the factory setting, than your throttle is open 100% of that 78degrees

 

ok, thats what i was thinking.

 

Hook up a voltmeter to your TPS and see how much it's really opening.

 

There was no apparent slack in the cable. Also, the cable hit the stop inside the traction control long before the pedal hit the floor.


I found some references on this site with the same situation, one guy did something similar to me except he took the traction control apart to move the stop, where I just drilled and dremeled it out. The other one described the same scenario, and he claimed he DID have success adjusting the throttle cable. However, I observed the throttle to be opening as soon as I stepped on the pedal, so if it was "tightened" I would think it would no longer return to the closed postion when my foot was off the gas.

Still, I do not have much experience with this engine, so I could be missing something with the cable adjusting scenario. Almost all I know I learned here or on other LS1 web sites. Either way, this solution worked for me, so I'll post it in case it helps someone.

 

your logic seems sound, the only thing i would question is if you were not the first owner, possably the TB was not the one that came with the car(98-99 had differant TB cable lobe sizes then later models....) (i think it was 98 and 99)

 

I've heard of the mod but did not think it was worth it. Why would GM only have the throttle body blade open to 78 degrees? Why not 90? to begin with.

 

oh its VERY worth it... gm made alot of mistakes... why would they put a rear in that cant hold even stock hp?
why did they put a restriction in the master to slave hydrolic line that makes it hard to shift from 3rd to 4th?
why did they kill 35+ years of history???

sometimes the general does dumb ****... if they did everything perfect then we would not need a ls1tech website...

 

I believe you should go by geometry, not electricals.
Blade to dead center by stop. Then adjust your TPS
if it's out of range (should not be). Then check that
the pedal pulls it full open, short of the floorboard.
Cars with ASR/TCS may need slack taken out of the
(non-adjustable) pedal cable segment by adding a
spacer. Mine did, an inch worth.

 

Good answer LOL

 

I bought the car a few months ago from a chevy dealer with about 7,000 miles. It was supposedly a "demo" they bought from another dealer and never sold to private owner. It appeared to be completely stock.

So it is possible that it is a different throttle body, though it seems unlikely to me. However, having the wrong size cable lobe on the throttle body would fit in to the problem I encountered.

How can tell if the throttle body and/or cable lobe is different? ...and if it is, does it matter now?

 

it does not make a big differance, if any at all, the only trouble you would have encountered because of it, you have fixed anyway
so for you it is a non issue

 

oh yeh it should be said.... check the parts for sale section. anytime someone is going to sell there car they almost always return it to stock with other peoples parts... its pretty comman practice...

 

How do you hook a voltage meter up to the TPS? and did you just use a dremal tool or something?

 

I loosely followed the instructions on ls1camaro.net, in the articles section. This is where I found the place to test the voltage. I did not disconnect the throttle cable, and I only needed a short piece of wire to stick out of the connector. With the meter gounded, to test you just need one hand testing the voltage, and the other opening the throttle. A dremel is what I used for the grinding. Keep testing the voltage as you grind so you don't go too far. If you end up not needing to adjust the throttle cable, and there is no conflict with the traction control, the whole process should be pretty staightforward.