Happy holidays to everyone:

I currently have a 6 lb pulley JDM chip and filter. For some reason I feel that my truck ran stronger when I had the 4 lber chip and filter. I would like to hear opinions about anyone else's experiences when changing from a 4 lb to 6lb pulley setup.

 

I have always had the theory that it would be safer to run a more aggresive chip with a 4lber than a less agressive chip with a 6lb. but thats just my uneducated opinion

 

UB
I've done testing with this comparison.
I have a 4lb Lower and a quick change stock or 2lb Upper.
My 1st Racing Season I switched often at the track to compare the difference between running w/4lbs vs 6lbs. I found I can loose as much as 2/10th's AND EVEN MORE w/6lbs if hot lapping.
This yr I only compared it 2 diff times at 2 diff tracks, with simular results. At Cecil I ran 12.2 when I switched to 6lbs, this was after (2) 12.0's using 4lbs.

To date, every Best ET I have (except one) was with the 4lbs, AND NOT THE 6LBS. My last run at Eng Town was with 6lbs +75 N2O HP, But thats NOT what made the difference.
The 12.0's were done full weight, with seats, tools, spare, the works. The eng town 11.81 (6lbs), we DID take the seats out, spare off, and anything else we could take out, jack, tools, etc..
There is no doubt in my mind I can run 11's with only 4lbs by adding that 10HP of Nitrous (75HP) and a little weight reduction.
My guess is with 4lbs it would have been the same or better,
BUT NOT WORSE.

Once we start overspinning the Eaton, the extra Boost can actually work against us be loosing HP due to much hotter
air inlet temps. (remember, I have NO COOLING MODS)
And back then I was hot lapping all my runs in the summer heat.

 

Anybody want to trade a 6lb for a 4lb. I have a 6lb but i can only use 91 octane (Cali gas) so the 6lb's is too much for my truck. Any takers?

 

At the track I have passed at least 5 guys running 6# lowers to my 4# lower. It's the same every time. At launch they pull me by about 1 truck length. Then I catch and pass them before the end.

Now having said that. I have noticed that in the really cold 30 degree weather they will out run me in ETs and trap speeds. But on a 60-80 degree day they are toast.

The ones that steadily pull on me are the 5# lower guys. I;ve ran 2 different guys. I beat them both. But it was cause I got a solid launch. They both slowly gained on me every time.

Oh and Loosebolt? He's the odd duck in my experiences... He has a 6#lower and that turkey walks very steadily down the whole track! I reckon it's his tune/combination of parts?

Rich

 

Thanks for the replies everyone, I think I'm going to switch back to the 4#. Anyone else care to share their comparisons?

 

I agree with Rich.
the 6# makes more power, but a lot more heat.
Once that heat builds up, you start losing power and the cooler running 4# has the advantage.

You need to pull the heat from the I/C.

I personally think (no data to back this up) if you make a homemade supercooler, run your I/C lines to the container, have it run through coiled copper tubes, then back to the I/c. Have the container full of ice to draw that extra heat and then some out of the a/f mixture, the heat will not effect the 6#.

 

what if I install an aftermarket heat exchanger? Would that even things out a bit and reduce some of the extra heat of the 6 #er?

 

i would say yes but only if you had the heat exchanger, fans, and intake spacer.

 

I run the 6# in Cali with the 91 octane gas. It had 7 dyno pulls as it was getting dialed in and I only lost a little on like 2 of the seven as Danny tweaked things. The best was the final pull. At the track, I had several runs with **** to compare to. He had the 4# but also had some other goodies to give him like 10 more hp than me. I beat most of his times even though I was on F1's and he was slicked. Head to head, I spun terribly, peddling it, my truck shifted to second and held it for some reason. I didn't gain or lose anything the hole way down the 1/8th, even though I pulled second from 2000 rpm. The heat probably would hurt me more in the 1/4, but for street play, it's hard to beat the torque of the 6#. IMHO. Jubes, if you have the 6 and are in SoCal, have Danny dynotune it. No problems here for almost 20k miles.

BD