Basics on Increasing Horsepower

Disclaimer: Links on this page pointing to Amazon, eBay and other sites may include affiliate code. If you click them and make a purchase, we may earn a small commission.

srs5150

TYF Newbie
Joined
Oct 24, 2016
Posts
24
Reaction score
76
Here's my first attempt at an article for TYF....

In a very general sense, our engines are nothing more than large air pumps. They suck in air (intake), mix it with fuel and spark to generate power in the combustion chamber, burn it, and spit the bad stuff out the (exhaust) tailpipe.

The better our engines breathe (the more air they can suck in) and the more air they can efficiently push out, the more power our engines will make.

Cars (including our trucks) – I use “cars” for short - are mass produced to be nice and efficient. Many government agencies see to it that our cars are produced to be quiet, fuel efficient, and good for the environment. All good stuff for the masses, I would agree.

The stock air box (intake) on mass produced cars is not made for horsepower, it is made with restrictive airways and a basic filter to keep it efficient and quiet. This chokes your engine from a lot of that good horsepower producing air that it needs to roar. Most engines off the assembly line aren’t allowed to roar, that would be un PC, and we can’t have that!

On the opposite end, the exhaust is the same way. Mass produced exhaust manifolds are used because they can be made cheaply, and easy to install (relatively speaking compared to headers). Next, your exhaust needs to push that air through at least one catalytic converter, mufflers and restrictive piping. The “cats” purpose is to get rid of most of the noxious fumes that your exhaust would normally spew into the air. Mufflers quiet the exhaust down and every angle or “turn” in the piping represents a point at which your exhaust is not breathing as well as it could.

Enough talk, let’s build some horsepower!

#1. Intake: So, when building horsepower, I think it is safe to say that most people start with the Intake (tube, not intake manifold). It’s a bolt on that can be done in under an hour and has noticeable results right away. It might not throw you back into your seat any more than it did before, but it will add a noticeable growl when you hit the GO pedal. And we all know from our Honda Civic friends that louder means faster. Oh, no, he did *NOT* just go there, did he? I’m allowed to, I had a hot-rodded Civic in a past life (without the fart tube, mind you). I also have ADD, back to the topic….

Cold Air Intakes (CAI) and ram air intakes simplify the stock air box by replacing it with a simple large diameter tube with a high flow filter on the end of it. Something to keep in mind is that (in addition to just “air”), your engine loves cold, dense air - so be careful which aftermarket intake you select for best results.

#2. Muffler: The easiest mod on the exhaust side is to replace your restrictive (un sexy sounding) stock muffler. Mufflers are relatively inexpensive and a shop can put one on for you in an hour or so. Depending on your selection, you will notice a dramatic sound in tone of your exhaust. This tone may be pleasing or obnoxious. I recommend spending some time on YouTube listening to different mufflers and listening to other trucks. Remember that the same muffler on a big block V8 will not sound the same as it does on a 4 cylinder Honda, so take the source into consideration, as well.

A twist on #2 is a “Cat Back” exhaust system. Here, instead of just doing the muffler, we are also swapping out the restrictive piping from the catalytic converter(s) to the exhaust tip. If you look at stock piping where it bends, it’s usually pinching at the turns. These pinches restrict air flow. If you have heard of the term, “mandrel bends”, this means that when the pipe turns, it does so gradually, without pinching, or changing the diameter of the tube. This maximizes air flow.

#3. Tune: If you’ve done the basic intake and exhaust mods, your engine should be breathing better. Air / fuel mixture is very important to generating horsepower so letting your car’s computer know you’ve changed the game a bit will help go a long way to taking advantage of the horsepower you have already freed up.

That’s the easy stuff, and It should free up horsepower. How much? I’m not going to say because it is so subjective and there are too many variables. Read up on each component to see what kind of gain you can get. Don’t take the manufacturer at their word, check where guys have dyno’d results. The gain from each mod individually might seem slight, but adding them all up together as a system will make for noticeable gains.

This has gotten a bit long winded. I have many more ideas on really taking it up a notch. If you guys feel this is valuable info, let me know and I can do a part two.
 
Last edited:

Tonyrodz

Resident Resident
Joined
Feb 16, 2012
Posts
30,979
Reaction score
45,108
Location
Central Jersey
Very interesting. I'm sure it clarifies for the novice, and maybe some old heads on here. Keep the knowledge coming Steve. :)
 

dantheman

Full Access Member
Joined
Nov 3, 2014
Posts
138
Reaction score
141
Location
Houston
just a note, the stock airbox in these trucks with a high flow filter produces more power than any of the conical filters in the engine bay. hot air = less dense = less power. cooler air (even if only 10 degrees cooler) will produce more power. for these trucks the best setup is the stock airbox with a high flow filter, and a replacement tube that goes from the MAF to the throttle body.
 

08HoeCD

Full Access Member
Joined
May 6, 2016
Posts
2,052
Reaction score
1,931
dantheman is correct.

While the basic information provided by the OP is valid for many vehicles, you won't get much bang for the buck with these recommendations on a late-model Tahoe because the oem airbox and even the muffler are not as restrictive as on many other vehicles. The tune is where you'll see the most results.
 

dantheman

Full Access Member
Joined
Nov 3, 2014
Posts
138
Reaction score
141
Location
Houston
some of the reading ive done has suggested that the earlier trucks 00-05 tune has the power enrichment not ever coming in and that MOST of the gains you get are from enabling it. if i recall they have it set to something like you have to be at WOT for 200 seconds before it goes to PE mode. i might be wrong on this as its all 3rd hand knowledge. i havent hooked my hp tuners up to the tahoe yet to tinker with it and see. but picking up 30-40hp off of just adjusting 1 tune value would be pretty rockin lol.
 

Danny3737

Full Access Member
Joined
Jan 3, 2016
Posts
1,382
Reaction score
2,041
Adding a cold air intake and/or a performance air filter while still using the stock throttle body is going to give you little to no extra HP. The computer without a tune is going to ultimately determine the air flow mixture. That's why when the air filter gets dirty ( to a point ) the drivability and performance stays the same.
 

adventurenali92

Full Access Member
Joined
Feb 16, 2015
Posts
7,230
Reaction score
8,323
Location
Big Bear Lake, ca
So my apologies if this has been asked before. Bear with me. I'm still new to underhood mods and changing things performance wise. As of right now, I have a spectre CAI, that I got from another member and love it, on my 2006 Denali XL with the LQ4 6.0. Everything else is stock setup. Now, I think a cat is starting to go bad(I think there's 2 right?!) so here's my question, when I have the cats(?) replaced, I want to do a custom exhaust while everything is opened up down there. What's a simple exhaust mod route to go, that will give my truck a nice beefy sound, but not too crazy, maybe a little more kick when I go, but not necessarily have to have this, And what would I need to replace my cats and not break the bank? I also don't really understand the differences in exhaust setups, so any insights you guys have to share on that would also be appreciated!
 

W8TVI

Full Access Member
Joined
Nov 6, 2016
Posts
696
Reaction score
692
Location
Traverse City, MI
So my apologies if this has been asked before. Bear with me. I'm still new to underhood mods and changing things performance wise. As of right now, I have a spectre CAI, that I got from another member and love it, on my 2006 Denali XL with the LQ4 6.0. Everything else is stock setup. Now, I think a cat is starting to go bad(I think there's 2 right?!) so here's my question, when I have the cats(?) replaced, I want to do a custom exhaust while everything is opened up down there. What's a simple exhaust mod route to go, that will give my truck a nice beefy sound, but not too crazy, maybe a little more kick when I go, but not necessarily have to have this, And what would I need to replace my cats and not break the bank? I also don't really understand the differences in exhaust setups, so any insights you guys have to share on that would also be appreciated!

I'm not sure if the newer GMT800 trucks still are laid out like mine is, but on my Yukon XL, it has two cats (one on each side, that Y into a single pipe once it gets down to the underside of the truck. My mechanic said he can convert it to true dual exhaust by cutting out the Y and running two pipes and mufflers to the back of the truck for about $650 installed.
My dad's truck is plumbed the same way and he had it done. I love the sound, and want to get it done on my truck, but there are other things I should need to fix first before putting $650 into something that doesn't need fixing.

Here is a video of what his sounds like:
 

Forum statistics

Threads
129,127
Posts
1,810,864
Members
92,214
Latest member
George ramos
Top