horsepower for less $

[greenday9d1]

I'm trying to modify my cherokee on a fairly low income, so i'm trying to figure out what i should do that would increase horsepower but not cost to much (which means simple enough that i could install it myself). I've already installed a throttle body spacer and a new exhaust manifold, and i'd like to know what other things i could do for not too much money that would increase my power. thanks!

[REDXJ4FUN]

Bigber TB weth its a DIY or one you can now gwt off ebay they work very well. Plus some type if aur intake helps alot.

[woody]

A couple universal speed-tricks:

#1 is losing weight... anything that isn't making your ride quicker is probably slowing it down... If you plan to buy new wheels, light alloys are better than steel. Ounces add up to pounds, and losing pounds offsets other mods or adds performance.

#2 minimize parasitic losses. You could do away with the A/C (if equipped) and change to synthetic oil in the engine, manual trans, and axle(s) if your rig is fairly oil tight.

My XJ has most of the interior stripped out... (left the dash, console, front seats, and door trim) mainly since it sees some mud use & I don't tote more than 1 passenger.

[MonsterXJ]

Dude u gotta get Nos! havnt you seen fast and the furious? And get some big-ass vinal stickers, that adds mad ponies!

[hjeepxj]

Originally posted by MonsterXJ
Dude u gotta get Nos! havnt you seen fast and the furious? And get some big-ass vinal stickers, that adds mad ponies!

stfu n00b


you can make your own intake, dynomax or rustys catback for 92+ is 130, and boring your own tb aint hard

[Dr. Dyno]

As a great fan of homebrew mods, I say do as many as you can. As far as cheap HP mods go, here's a list:

1. Homebrew FIPK (like mine on my website) +5hp
2. Self-bored 60mm TB +3hp
3. Self-bored 62mm TB spacer +2hp
4. Dynomax Super Turbo 2.25" cat-back from Summit Racing $120 +6hp
5. Carsound high-flow cat (when your old one expires) +2hp
6. Custom 2.25" exhaust downpipe +5hp

That's a cheap and very easy 20+hp. The stock downpipe has lots of crimps in it, so chop it out about 6" below the flange at one end and 6" from the cat at the other end. Then weld in a new uncrimped section of pipe in between. A good muffler shop can do ths for you.
Like Woody said, you can also remove some unnecessary weight for further performance gains. Each 100lb removed is like gaining 6hp and it's free. Here's what you can remove:

1. Gas tank skid 32lb
2. Engine skid 18lb
3. TC skid 10lb
4. Roof rack bars 13lb
5. Spare wheel 50lb
6. Dual electric fan conversion 5lb
7. Floor mats 5lb
8. Jack, jack handle, and lug nut wrench 10lb
9. Rear seat bottom 20lb
10. Front driveshaft 20lb
11. Fibreglass hood saves 15lb
12. 1/4 tank of fuel saves 85lb

You could also remove the A/C compressor and condenser, charcoal canister, screen wash bottle, and a few other odds and sods. Removing weight from the front is more advantageous than removing it from the back.

[JeepSpeed]

Sorry to jack the thread, but anyone know where to get, or who makes, fiberglass hoods for the XJ? As a starving college student, Im probably not in the market just yet (that's alot of beer money), but would like to know for future reference. Also is there any disadvantages to kicking the charcoal canister? Will I screw up emmisions or dirty my engine bay if i take it out? And last question, I promise, is there any danger in removing the gas tank skid? My RWD wonder will never see real offroading. Muchos gracious.

[Dr. Dyno]

I removed my gas tank skid, front skid, roof rack bars, plastic engine undertray, and clutch fan. My Borla header/downpipe is 7lb lighter than the stock manifold/downpipe and my Flowmaster muffler is 7lb lighter than the stock muffler, so my XJ is about 85lb lighter than stock.
No harm in removing the gas tank skid except that the gas tank will be more vulnerable to damage if your Jeep gets rearended.

[hjeepxj]

Originally posted by JeepSpeed
Sorry to jack the thread, but anyone know where to get, or who makes, fiberglass hoods for the XJ? As a starving college student, Im probably not in the market just yet (that's alot of beer money), but would like to know for future reference. Also is there any disadvantages to kicking the charcoal canister? Will I screw up emmisions or dirty my engine bay if i take it out? And last question, I promise, is there any danger in removing the gas tank skid? My RWD wonder will never see real offroading. Muchos gracious.

usbody.com has a slick looking hood, expensive though

not sure of who makes a stock replacement one...(in fiberglass)

[greenday9d1]

My AC doesnt work right now anyway, but dies the drivebelt tighten eough to cover that?

[greenday9d1]

also if i get a bored out throttle body, will i need a larger bore throttle body spacer?

[REDXJ4FUN]

I belive you would since most are just meant for the standard bolt on.

[hjeepxj]

Originally posted by greenday9d1
also if i get a bored out throttle body, will i need a larger bore throttle body spacer?

yeah, if you want gains ;)

[woody]

Originally posted by greenday9d1
My AC doesnt work right now anyway, but dies the drivebelt tighten eough to cover that?

No, but just snag an Idler pulley & bracket from a non-AC equipped Jeep with the same motor.

[aspera]

I've done some of these. My catback is just a short little straight pipe from Autozone...need to work on that.:) At least it fits the cheap, light and free flowing criteria.

I also stripped out the interior. I even removed the passenger's side of the dash. Headliner, conlsole, carpet door panels, etc...all gone. All I left was 2 seats and some trim around my head. I wish race seats were easier to bolt into an XJ.

I'd like to ditch the charcoal canister. I'd like some instructions before I begin.

I'd also like to either (a) remove the front driveshaft, or (b) convert it to RWD. Please point me to the proper thread.:lol:

I want to keep the A/C, but it ain't-a-workin' so it might have to go. Got a pic, part#, price of the A/C idler?

I don't mind spending a little money on the Jeep cause I got it for free, but I want to see how much I can build it up on a 'ghetto' budget. I like seeing my co-workers get freaked out when they see the empty interior.:D

[Lawn Cher']

Aspera-

I'm moving to the St. Louis area within a few months, and I have a 2wd MJ that I plan on converting to 4wd once I get settled into my new place. If you want, I can pass the 2wd transmission and front axle your way. Is your XJ a 5-spd or auto?

[aspera]

It's an auto.

Excuse my ignorance, but what is the difference between the 4WD and 2WD transmissions? Isn't the transfer case a seperate assembly?

[Johann]

There is a different tail piece on the 2wd tranny to make up for the lack of tcase. The slip yoke has to go somewhere:D

2wd slipyokes are longer as well

[Lawn Cher']

The MJ has a Pugeot 5-speed (replaced shortly before I bought the truck, and I haven't driven it at all except to move it around on the driveway... shifts very nicely.) I don't suppose you want that then, do you.

[aspera]

Normally I prefer manuals, but I'd rather stick with the auto that it came with. Now if I had a T56 6-speed just sitting in the garage I might consider a conversion.:D

[Slip Kid]

Here's some pics of my homemade intake. I used a rice-burner filter from autozone. The tube is 3" pvc, and I had to use a section of smaller pipe to connect to the filter. (3" exhaust pipe will work, and is commonly used for the entire tube) you can see my coffe jar, it's to catch engine blowby, if your engine doesn't blow oil, you can just use a hose strait from the valve cover to the airtube.

I used an unrolled piece of stovepipe and some rivits to make the heat shield.

http://www.geocities.com/foxfire13.geo/images/intake.html

[aspera]

Now THAT'S home made.:eek:

[aspera]

Well, I yanked the charcoal canister. It was pretty easy. I just moved the wiper fluid tank out of the way and removed the 3 bolts that hold the bracket for the canister. I just unplugged all of the hoses and wiggled it out. A few more minutes to plug the lines and I was done.

...so I worked on the sound deadening tar patches in the doors for while. I quit when my fingers hurt too bad.:D I got most of it done anyway.

...next I discovered some rusty-ass door seals attached to the bottom of each door. WTF are those things supposed to do? They sure didn't stand a chance against a determined idiot with a screwdriver (me).:D They were pretty heavy, too.

I was done for the day and had to go to work. I had some time before work...so I removed the parking brake handle. It didn't work anyway. Lazy parts piss me off:laugh:. I couldn't believe how easy it was to take off...just two bolts.

[JeepSpeed]

To aspera or the good doctor Dino,

Is there any downside to removing the charcoal canister? Will it screw with my emmisions or crud up my engine bay? Just wondering, would like to take it out and get rid of some of the clutter in there, I'm sure it can't weigh more than a pound or two. Thx.

[Dr. Dyno]

Originally posted by JeepSpeed
To aspera or the good doctor Dino,

Is there any downside to removing the charcoal canister? Will it screw with my emmisions or crud up my engine bay? Just wondering, would like to take it out and get rid of some of the clutter in there, I'm sure it can't weigh more than a pound or two. Thx.

Is that all? I thought it would weigh more than that. I was going to remove mine to save some weight as well as reduce clutter in the engine bay.
The only downside that I can think of is that the engine bay will have a strong smell of gasoline vapours. Not sure how you'd get around that issue.

[aspera]

Mine doesn't smell. I plugged up some of the vents with rubber caps that I found at the autoparts store.

Currently, I'm yanking the A/C junk. So far I removed the condenser, accumulator, and all underhood tubing. I still need to get rid of the compressor and evaporator core. Anybody done this?

My engine bay is gonna look SO sano.:D

[JeepSpeed]

I love the smell of gas vapor in the morning! Haha, won't plugging up the holes leading to the canister cause a back up and send the "charcoal" or whatever it is back into the engine? Is this bad, or do I just not understand it's function? If thats the case, can i just turn the tubes down, and leave them open so i just spray the "charcoal" onto the street below? Oh, and Dino, thank God you're alright, I heard about the bombing. Thanks. :)

[Dr. Dyno]

Thanks Jeepspeed. :) I was still in Cyprus when the bombing took place and I heard about it on the BBC news. It was horrible. I'm glad I wasn't there at the time but I'm back in town now. I returned on Monday morning.
I've decided I'm going to leave my charcoal canister in place for now. The A/C lines make it a major hassle to remove, and in any event removing it might set off the check engine light.

[5-90]

The principal reason the charcoal cannister exists is to collect fuel vapours from the tank and store them until they can be released into the intake stream for burning. Removing the cannister and plugging the lines should not affect engine performance, but WILL cause you to fail emissions in CA - and probably most other places that have emissions controls with a visual inspection (removal/alteration of OEM equipment.) Greenday, don't do it unless you are planning on putting it back every two years or turning into off-hiway only use.

BTW - Where in the BA are you? We seem to be collecting here (Jes is in SF, Pancake is a few miles from me here in San Jose, anyone else?) Perhaps us BA types should get together some night...

5-90

[catyrpelius]

like the other guy said, get some nos stickers, perhaps a racein strip, u coudl also get one of those big ass coffe can style mufflers or u could just cut a hole in the bottom of a coffe can and duct tape it onto the end of your muffle. All these things make it mad fast, i believe that the nos stickers alone give you 548749569658 horsepower

[Phil]

like the other guy said, get some nos stickers, perhaps a racein strip, u coudl also get one of those big ass coffe can style mufflers or u could just cut a hole in the bottom of a coffe can and duct tape it onto the end of your muffle. All these things make it mad fast, i believe that the nos stickers alone give you 548749569658 horsepower
So do you not like horsepower, or do you have more money than brains, so you can buy every single go-fast part you want? Some people do have limits on what they can spend on their Jeep, and they want the most bang for their buck.

[Sarge]

like the other guy said, get some nos stickers, perhaps a racein strip, u coudl also get one of those big ass coffe can style mufflers or u could just cut a hole in the bottom of a coffe can and duct tape it onto the end of your muffle. All these things make it mad fast, i believe that the nos stickers alone give you 548749569658 horsepower

If you and the others posting like this don't like this sort of thing....go to one of the other forums.

Sarge

[JnJ]

like the other guy said, get some nos stickers, perhaps a racein strip, u coudl also get one of those big ass coffe can style mufflers or u could just cut a hole in the bottom of a coffe can and duct tape it onto the end of your muffle. All these things make it mad fast, i believe that the nos stickers alone give you 548749569658 horsepower
Take a hike. No use for PITA punks here.

[Goatman]

Sorry to jack the thread, but anyone know where to get, or who makes, fiberglass hoods for the XJ? As a starving college student, Im probably not in the market just yet (that's alot of beer money), but would like to know for future reference.

Jeepspeed, I find a little humor in your posting name and your question. Jeepspeed is the name of an XJ only offroad racing class and organization. Using that name sort of implies that you have something to do with them. They also happen to offer fiberglass fenders and hood for XJ's. I couldn't help but get a kick out of you asking that question. :laugh2: :laugh2:

:D :D

[JeepSpeed]

Haha, yeah, I feel like a fake jerk when ever someone brings it up or i think about it, but I have no connection to Jeepspeed whatsoever. I greatly admire what they do and wish I had money so that I could too. But I actually had the name Jeepspeed on another forum (supraforums, don't ask.) over two years ago, before I even knew about the actual organization. Surprised when I found out about it. If I'm breaking a trademark or doing anything sueable, my name is Juan Ricardo and you have no idea who I am. Later. :)

[Goatman]

Haha, yeah, I feel like a fake jerk when ever someone brings it up or i think about it, but I have no connection to Jeepspeed whatsoever. I greatly admire what they do and wish I had money so that I could too. But I actually had the name Jeepspeed on another forum (supraforums, don't ask.) over two years ago, before I even knew about the actual organization. Surprised when I found out about it. If I'm breaking a trademark or doing anything sueable, my name is Juan Ricardo and you have no idea who I am. Later. :)

No big deal, Juan. :)

I just got a kick out of it. :D

[TOZOVR]

No harm in removing the gas tank skid except that the gas tank will be more vulnerable to damage if your Jeep gets rearended.

Or wheeled :wave:

[TOZOVR]

So do you not like horsepower, or do you have more money than brains, so you can buy every single go-fast part you want? Some people do have limits on what they can spend on their Jeep, and they want the most bang for their buck.
Bang for the buck...

....and yet very few folks actually do any real world testing and put blind faith in K&N Filters/intakes and just assume they're getting tons of HP.

Find a local dragstrip and go there. Weigh your truck. Go once a week and immerse yourself in the world. See what goes fast...try some stuff on your rig. See what makes it faster in REAL LIFE. See what does not. See what makes cars and trucks faster in general and apply it to your jeep. You will meet some amazing folks and make some great friends.

$15 a week is cheap money on real world data and info...not racing some schlep in a civic who isn't racing you in down town Yourtown, USA. Much better than dropping $40 on some filter that just makes your Jeep louder IMHO.

Good luck,
RJ

[01-XJ]

[QUOTE=JeepSpeed] where to get, or who makes, fiberglass hoods for the XJ?


Rusty's

[XJZ]

Somebody also makes lexan(sp?) rear side windows.....

And lose the hatch. :D

[JeepSpeed]

[QUOTE=JeepSpeed] where to get, or who makes, fiberglass hoods for the XJ?


Rusty's

Awesome thanks, very cheap too. Actually a little too cheap. There is no picture, no description, no weight. I would have to research that alittle bit further before I would invest in that.

[Mike@Accurate]

RE; new downpipe: The divits in the pipe clear the driveshaft yoke at full up travel. OK to put a new pipe in IF you don't wheel. Bottom it out and you will be looking for the old pipe.
RE; TB boring: 62.5mm made exactly 3.25hp on the dyno. Boring out the hump WON'T make three hp and going to 62mm WON'T make 2 more hp.
RE; air pipes: ours made 8.25hp on the dyno and knocked .2sec off of 1/4mi times. (no blind faith here)
RE; spacers: you probably will need to bore it to match an oversize TB. I don't think they work at all though.
RE; cannister: OBDII trucks will throw a code every time they try to purge, just like when you leave your gas cap open.
RE; belts: my '97 no-air motor takes a different length belt than my A/C equipped XJ. There are idlers, but I think you may need to buy a belt from the donor truck to make them fit .

I think the best mods are an air pipe and exhaust. Most real power. If you feel like taking your Jeep all the way apart, and not doing a stroker, a cam swap is the next biggest power adder. (NOS not withstanding)
MIKE

[Dr. Dyno]

I think the best mods are an air pipe and exhaust. Most real power. If you feel like taking your Jeep all the way apart, and not doing a stroker, a cam swap is the next biggest power adder. (NOS not withstanding)
MIKE

Don't forget about porting the head. I saw a good performance gain above 3000rpm after I home ported the head on my old 4.0 without losing torque lower down. I know a CNC ported head will produce better gains but a carefully done home port job can still produce good results. The exhaust side is particularly restrictive and opening up the exhaust port throat/bowl/short side radius probably produces much of the HP gain from porting the head.

http://www.jeep4.0performance.4mg.com/head.html

Since the head has to be removed for a cam swap, a ported head will complement the performance cam very nicely.
A combined 11hp from a free-flow intake and bored TB sounds about right. A bored spacer will slightly lower the HP/TQ rpm peaks by effectively adding runner length, and produce a small gain in gas mileage.
IMO, the most restrictive part of the exhaust is the cat forwards, so replacing only the muffler or the cat-back won't do much. Replacing the cat and crushed downpipe will do a lot more, and will help you get more out of a performance cat-back.

[Gridikal]

In the exhaust situation, I just had my flowmaster super 40 put on today, I gained back the lost power from my dynomax "super turbo" and then a little bit more- not to mention it sounds 300% better.

[Mike@Accurate]

Dino,
"Don't forget about porting the head" ... Good call. I forgot. We got 16hp on a 4.0 & 20hp on a 4.6L. Especially if you are doing a cam and have it sitting there anyhow. Straightforward to run as well, no computer issues. MIKE

[ColoradoDave]

tons of weight can be stored up in the carpet too. There is tons of foam insulation under the carpet that stores up water adds lots of weight and causes rust. At the very least, pull the foam and insulation crap from under the carpet. you'll be amazed how heavy all that stuff is when you pull it out.

[cruiser54]

Man, what an old thread!!!!!!!!

[stroked88]

rawr!!! zombie thread!!!

[NorCalChris]

Very old thread. but I'm going to add to it.

Keep in mind the jeep was dynoed to prove all this. I'm not going to lie to sound cool on a thread from years ago. lol


I have had lots of different exhaust systems. I had some where the pipe ended after the muffler, i had open exhaust, and now i run a full exhaust all the way out the back like the factory had it. I went from a open exhaust w/ cat to a flowmaster muffler (i hate them, but that's a different story for a different day) with full piping all the way out the back. I gained BACK 4hp and 6 ft/lbs of torque that i had lost from going open exhaust.
I installed a K&n dop in filter and lost 1hp and leaned out my AFR. my renix engine doesn't meter the air going in, just manifold pressure. Luckily I have an adjustable Fuel Pressure Regulator. Made some adjustments and brought my AFR back to where I wanted it. Gained back the 1hp lost plus 5 more.
I indexed my spark plugs, and gained almost ten more hp.

Heres some advice. From the throttle body towards the filter your ducting should all be the same size. so if you run 62mm tb you want all the piping towards your filter the same size. Same with exhaust. if you run a 2.25 down pipe, you can go to a 2.5in in/out cat, you now need a 2.5 in/out muffler. and 2.5 in piping out the back. you dont want a 3in in/out muffler necked down to 2.5in piping out the back of the jeep.

[NorCalChris]

My jeep is a 90 4.0/aw4/242 with under 5k on engine. but 268k on tranny. I'm normally run 35x12.5 mtrs on steel rims. I have STOCK gears. Don't laugh or make fun of me I know, i know, i know. The last dyno run conditions were 93.99*f, 21% humidity. I installed two stock sized tires. I laid down 133hp, 175 torque. Sucky right? Well, consider a 25-30% loss through an automatic tranny plus tcase. Now this isn't no drag car, but its pretty good because stock ratings are 177hp and 220 ft/lb? so 177hp*.3=53.1. 177hp-53.1=123.9hp. 220ft/lb*.3=66 220ft/lb-66=154 ft/lbs
123.9hp/154 ft/lb of torque is whats expected to be laid down on a stock renix engine. I make 9hp more and 21 ft/lb over stock. not bad at all in my opinion.
It helps out when the turty fives are on. lol. Before all this it only laid down 106hp with 35s. :bawl:

[urban yan]

I laid down 133hp, 175 torque.
No one should ever say "laid down" and 133hp in the same sentence.

[NorCalChris]

haha. Say what you will.

[badron]

A late model intake sould be good for a more HP then most of the mods combined. Then a cam/lifters. Then a hoged out TB. Then a new poop pipe.

[cruiser54]

A late model intake sould be good for a more HP then most of the mods combined. Then a cam/lifters. Then a hoged out TB. Then a new poop pipe.

I thought I read somewhere that the late intake was good for 3 horsepower or less.........

[CherBear]

I thought I read somewhere that the late intake was good for 3 horsepower or less.........

Are you talking doing a late model intake manifold swap onto an older model?

[NorCalChris]

Are you talking doing a late model intake manifold swap onto an older model?
I believe that's what he is talking bout. I have heard it is not worth more then a few ponies, and haven't heard of any torque gains (although I'm sure there is some)

[Dr. Dyno]

I gained 2rwhp/4rwtq with the '01 XJ manifold swap and no other changes on my 4.6 stroker ('92 XJ). The biggest torque gain was 6rwtq at 3400rpm where it now peaks. I also gained ~1mpg in gas mileage so for me the manifold swap was worth doing since the manifold itself only cost me $53.

[yossarian19]

Well, somebody has to say it...
The biggest performance gains you can get on most vehicles will be... a good tune up.
Before you spend money on after market parts or porting the head, be sure you:
Replace cap, rotor, wires & plugs
Make sure your catalytic converter is in good shape
Replace O2 sensors as necessary
Clean the TB
Replace fuel filter, if applicable, and make sure the pump is healthy
have a fresh air filter
Run some injector cleaner (I've used Sea Foam, though I hear BGK44 is good stuff as well)
ETC
On my rig, replacing the worn-out cat did a lot more than anything else I messed with

[tone]

Well, somebody has to say it...
The biggest performance gains you can get on most vehicles will be... a good tune up.
Before you spend money on after market parts or porting the head, be sure you:
Replace cap, rotor, wires & plugs
Make sure your catalytic converter is in good shape
Replace O2 sensors as necessary
Clean the TB
Replace fuel filter, if applicable, and make sure the pump is healthy
have a fresh air filter
Run some injector cleaner (I've used Sea Foam, though I hear BGK44 is good stuff as well)
ETC
On my rig, replacing the worn-out cat did a lot more than anything else I messed with

Isn't it BG 44K? BG = brand and the 44K = fluid type or whatever? I haven't seen BG44K in years or a BG guy for that matter, where can I get some at? Haven't seen it since I worked for Goodyear years ago and only thought you could get it from the BG guy in the truck...

[yossarian19]

Isn't it BG 44K? BG = brand and the 44K = fluid type or whatever? I haven't seen BG44K in years or a BG guy for that matter, where can I get some at? Haven't seen it since I worked for Goodyear years ago and only thought you could get it from the BG guy in the truck...

Sounds like you know more than me already. Google search for it, though, and you'll find it available online.

[hubs97xj]

BG lists dealers on their website, and some guys on ebay sell cans of it as well.

[cruiser54]

44K is amazing stuff. Works way better than seafoam. Dealerships and repair shops carry it. Not cheap but worth every penny. ask Joe Peters.

[1990heepxj]

waking this thread up again.... anyway this article http://www.jpmagazine.com/techarticles/engine/154_0911_jeep_4_liter_engine_myth_busting_true_lie s/index.html explains that a newer intake manifold actually will reduce hp due to loss of air velocity

[gradon]

There are plenty of us that have swapped it in and have noticed an increase in performance. The smooth turning, equal-length runners and bigger volume are clearly superior in design.

[Dr. Dyno]

waking this thread up again.... anyway this article http://www.jpmagazine.com/techarticles/engine/154_0911_jeep_4_liter_engine_myth_busting_true_lie s/index.html explains that a newer intake manifold actually will reduce hp due to loss of air velocity

I gained 2rwhp/4rwtq on the dyno with the '01 XJ intake swap on my 4.6 stroker, with a ~5rwtq gain from 1500-3300rpm. Gas mileage also improved ~1mpg.
The '99+ intake has a much larger plenum but smaller cross-section runners than the earlier manifold. While HP gains may be small, the increase in TQ lower down the rpm range is noticeable.

[1990heepxj]

well my thinking of why it helped you is probly because you have a stroker and can actually use that larger displacement of air in the manifold. im not saying the difference is bad at all, every couple hp/tq counts so if it would help me id do it too. its kinda same concept as a tb spacer and everything else stock, it does nothing because the factory setup can already pull in as much air as it needs to use therefor it gives it the ability to pull in more even though it wont use it. from what they found on a stock 4.0 i'd stay away from the swap, in ur case i would also swap it in for sure

[NorCalChris]

What everyone gains is going to be different. The conditions are always different. I have dynoed cars at 630 in the morning and then dynoed them at noon and seen a 15hp loss. Air temp is always a factor. This mod has been done and dynoed "enough" times to see improvements on the majority of people's rigs.
It always depends on how much its worth to you. Is 3hp/5ftlbs worth 50 bucks? MAYBE. What if the only one you can find is 100 bucks? Is it worth it now?

[Dr. Dyno]

I have dynoed cars at 630 in the morning and then dynoed them at noon and seen a 15hp loss. Air temp is always a factor.

The dyno is supposed to correct for barometric pressure, air temperature, and humidity (usually to SAE standard on most chassis dynos). I think you're looking at raw uncorrected numbers.

[o-gauge-steamer]

The numbers out of a Dyno are open to discussion. Yes, they will give you a corrected to Sea Level/Standard Atmosphere/Humidity HP/Torque values which is really nice for comparing apples to apples. However, here at 7,000' altitude what I want to know is what do I really have to work with. Sea level numbers are sort of silly really...

The Golan Stroker I put in my 97 back in 2000 was rated at 300hp on the Golan Dyno. Sea Level. Here? Not so much. Unless you are running forced induction (and even then) altitude robs power.

[NorCalChris]

The dyno is supposed to correct for barometric pressure, air temperature, and humidity (usually to SAE standard on most chassis dynos). I think you're looking at raw uncorrected numbers.
Ok, I probably am looking at the uncorrected numbers, but that doesnt explain the difference in power when nothing changed on the vehicle. Ive seen it happen more then once too, but hey one time it was because some jackass left a bottle of co2 opend in the dyno room after disconecting a halo sprayer. that really threw us for a spin until we walked out there and realized the cars just sucking in the co2.

[CherBear]

Ok, I probably am looking at the uncorrected numbers, but that doesnt explain the difference in power when nothing changed on the vehicle. Ive seen it happen more then once too, but hey one time it was because some jackass left a bottle of co2 opend in the dyno room after disconecting a halo sprayer. that really threw us for a spin until we walked out there and realized the cars just sucking in the co2.

Nothing has to change on the vehicle to provide different dyno numbers. Temperature, humidity and barometric pressure all have an effect on horsepower and torque.

As you said, you dynoed in the morning (low temp) then again at noon (high temp) and saw a power loss...

[Dr. Dyno]

However, here at 7,000' altitude what I want to know is what do I really have to work with. Sea level numbers are sort of silly really...

Yeah, if you're living at high altitude they're not much use to you. The important thing to remember is that the dyno should be seen as a tuning tool rather than looking at the absolute numbers for bragging rights.
Just use the same dyno before and after each mod (preferably under similar weather conditions to minimize any difference in correction factor) so you can make an apples-to-apples comparison. That's what I did with the '01 XJ intake swap.

[o-gauge-steamer]

Dino,
You are correct that the BEST use of a dyno is for tuning. Way back before the dawn of time (circa 1973) I built up a 2 litre Triumph 6 cylinder into a 2.45L. Three Weber DCOEs using the British Leyland S-5 LeMans cam. Used the dyno at the BAP-GON. to get the Webers correct. Anyone that has ever attempted to tune Webers will under stand. Between idle jets, emulsion tubes, main jets, air bleeds.... Well you get the idea. At the Time, provided you were willing to accept "used" parts, BAP-GEON would trade out the as shipped parts for the ones needed to set up the carbs provided it was done on the dyno. Made for a relatively quick setup. End result? 256hp. Not bad for under 2.5L.

Of course, this was done in Sacramento. Elevation 20'...

[NorCalChris]

What everyone gains is going to be different. The conditions are always different. I have dynoed cars at 630 in the morning and then dynoed them at noon and seen a 15hp loss.


The dyno is supposed to correct for barometric pressure, air temperature, and humidity (usually to SAE standard on most chassis dynos). I think you're looking at raw uncorrected numbers.

Ok, I probably am looking at the uncorrected numbers, but that doesnt explain the difference in power when nothing changed on the vehicle.

Nothing has to change on the vehicle to provide different dyno numbers. Temperature, humidity and barometric pressure all have an effect on horsepower and torque.

As you said, you dynoed in the morning (low temp) then again at noon (high temp) and saw a power loss...
CHERBEAR, look at what dino said.

[Dr. Dyno]

At the end of the day, I was very happy that I swapped in the newer intake. It also helped that I got it for only $53. The HP/TQ gains were small but just enough for me to notice a subtle improvement by the SOTP. More importantly, I was impressed with the ~5% improvement in gas mileage so it didn't take long to recoup the cost of the intake with the fuel cost savings.