Extra Horsepower

kaspar139 · April 26, 2001

Truck:

2001 Silverado (1500) Ext Cab Z-71, with 4.8L V8

Background:

I first upgraded my truck with a catback Flowmaster exhaust system. Next, I added a 3" Performance Accessories body lift, and 33x12.5x16.5 BFGood Mud Terr. on 16.5x9.75 AE 589's. Now, the truck IMO looks sweet!

Question... before the upgrade to the tires, rims, and body lift, the truck had GREAT pickup. I expected the truck to lose a little power with the increase in tire size, but it seems to be more than a little. What can I do to increase the horsepower with MINIMAL effects to my warranty?!?!?! This is URGENT! I feel like the truck is draggin ass.

Thanks in advance.

Jack Boelte · April 26, 2001

You need to change your rear end gear ratio to compensate for the larger diameter tires. You made a pretty large change in your overall drivetrain ratio with 33" tires! Go to a reputable 4 Wheel Drive accessory shop that regularly does rear end changes, they can help you select the corrcet gear ratio. This will also correct your erroneus speedometer.

kaspar139 · April 26, 2001

No kidding? I realized, like I said, that I would decrease in performance, but I was shocked at how much. I had 265/75 R16's on before the swap (which are equiv. to 31" tires I think). The gear ratio was 4.10 before, so according to http://www.tyres1.com/tech_calcs.html, my new gear ratio from a 31.6 to 32.8 swap is 3.95.

How much will a gear swap cost? What about a K&N air filter? How much would that help (probably not much).

And, that is awesome that it will correct the speedo!

Thanks!

Jack Boelte · April 26, 2001

I didn't realize you had 4.10's! I wouldn't think you would notice that much difference either, especially with the difference you show in ratio change. It's not that much.

K&N is a big help. Maybe look for some emissions legal long tube headers from Hooker. I think you have to wait until you reach 50,000 miles or damage before you can change to a free flow cat. Mr. Screwdriver could help you there!:DGears are around ? for teh ring and pinion set, see 4 wheel and off road magazine for a billion different advertisers. Not sure how much it would cost to install. I don't think it is too difficult, it just has to be exactly right. If you feel up to it, you may consider doing it yourself. With my '84, I would do it, not with an '01 though!

Maybe a performance computer chip? Don't get cheap here!

Shaners · April 26, 2001

I put the K&N FIPK Gen II kit in my truck. I like it alot and claimed HP increase is up to 15 horsepower. They are about ?.

You could also buy a hypertech and reprogram your computer. This will help alot too. You'll be able to reprogram for shift points in the tranny, change your tire size calibration for the speedo, and change the ail fuel ratio in the injectors for added performance. The down side is that you should probably run premium fuel if you start changing air/fuel mixtures. But recalibrating the speedo and changing shift points is worth it. Your truck makes it's torque up in the higher rpm range, and the exhaust that you added, will probably push you further in to the higher rpm range in order to find power gains. (About ?)

Unfortunatly these new Vortec motors require a certain amount of back pressure to generate torque in low rpm's. By freeing your exhaust up you have moved your torque curve further up the power band, and lost some low RPM grunt. (Although I bet it sounds GREAT!!!)

Good Luck

Frank S · April 26, 2001

Shaners beat me to it!

The Hypertech PP3 is what you need for sure,although I don't advise altering the factory shift points because your truck will not shift until around 6000 rpm's at wide open throttle.I am quite sure you would also like what it will do for the firmness of your transmission shifts.

The K&N gen II FIPK is also a great mod and it should come with a CARB exemption sticker because they are 50 state smog legal.

Welcome aboard and let us know what you decide to do.

Roofer · April 26, 2001

I have almost the same setup, but with 285/75/16 tires. I added a K&N Gen II, dual exhaust, HPPIII, and a 180 powerstat. I only have 3.73's and I can burn up the 285 BFG's from a stop pretty darn good. A few mods seemed to help me quite a bit. It burns the tires better now with the 285's than it did completely stock with the Firestones. Like Yzr2K said, let us know what you do and how it turns out.

Later

Frank S · April 27, 2001

#Moderation Mode

Let's go ahead and move this into the Aftermarket forum.

Moved here

kaspar139 · May 1, 2001

I think I am definitely going to get the K&N gen II FIPK kit, as I can do that one myself. I don't know what all would be involved in placing the performance chip in there, and adjusting settings. My automotive expertise is not that great, however I am willing to learn (just not much room for error on my NEW truck!)

Also, I looked on the web, www.chevrolet.com, and could swear that I saw my gear ratio was originally 4.10, but I will re-verify that. I think I will head over to 4 Wheel parts and see what they will charge to install a new gear setup.

Also, thanks again for ya'lls input.

TheScaryGuy · May 3, 2001

Well, I spent 80 bucks on plugs and wires and the suckers running and firing like a champ now. The bosch platinum +4's aren't cheap but man, I was amazed really at how much better it ran. (This along with new bosch lifetime warranty wires)

I know it doesn't say 20hp increase! or 250bucks, but it seemed to be a cheap increase for me(not that 80 is cheap heh heh)

kaspar139 · May 3, 2001

How will that affect your gas mileage, ScaryGuy??? I am willing to try anything, I was just under the impression that a spark plug change could cause your mpg to go WAY down (but I could be confusing that with something else, WHICH is entirely possible).

And, 80 bucks sounds like a GREAT fix :-D

Shaners · May 3, 2001

Kasper,

I don't really want to jump in on "scary", but there is a difference of 12 years between your truck and his. On an older vehicle, getting new technology (plus replacing old parts) should definatly benefit!!!

I had an '89 G20 van and replaced plugs (AC Delco) wires (8 mm) and added a k&n drop in air filter and it felt like a new motor. I had about 65K miles on it at the time.

Your truck already has Platinum tip plugs, but nothing like the Bosch plugs that Scary put in his truck. You also have Sequencial Fuel Injection, as compared to the older "throttle body" system. And you have a much more advanced computer.

I would recommend the FIPK Gen II (which you said you would be installing) and the Hypertech III reprogramer. The Hypertech is much simpler than replacing a "chip", and you can control how far you want to tweek your motor, trans, adjustments for shift firmness, and for tire size.

Shane

kaspar139 · May 3, 2001

Thanks Shane, you make a very good point. I wasn't even thinking along those lines. As you can see, I have a lot to learn about my truck!

TheScaryGuy · May 4, 2001

Doh......Shaners hates scary...... :-( And he likes to put scary in his place about not knowin nuttin..... ;-)

lol J/K shaners!

Shaners · May 5, 2001

no way Scary... just a little quicker to post than you. I'm glad your truck is running good, and I'm really bummed that the Buick is trashed... I remember those cars foundly!!! They had a backseat in them kinda like a sofa bed!!! Highschool memories.... they'll never go away!!! LOL