Hey everyone I'm new to the forum but wanted to give some insight to some mods I just made to my weak I5.

When I test drove my H3 at the dealership it was after driving Wrangler Rubicon’s, Mitsubishi endeavors, an ugly Chrysler suv, Nissan murano etc. So when I got behind the wheel of the H3 and drove it; Yes a little gutless but not horrible after driving the above mentioned. Anyway I bought it obviously knowing I would be making some upgrades to the engine.

Well at home I drove my V8 grand cherokee and almost threw up.

I went straight to the web and went shopping. Several hundred $ to autoanything and a few days later I was in the garage. Oh by the way my dad drove my h3 and 2 days later bought one.

Disclaimer: No we don't have money to blow. It just so happens we both needed a new 4x4 both our grand cherokees took a dump at the same time and winter is coming. Utah winters can get pretty bad.

So we were both in his garage. Ordered K&N 63 Cold air intakes, air raid throttle body spacer and jet mass air sensor.
After 2 hours working side by side helping each other etc we were finished. I took another 15 mins going over our work before starting up because it seemed too damned easy. I have put cai's from k&n on jeeps as well as throttle body spacers and for some reason I just felt they took longer.

Well we started them up and the ECU went nuts revving and super low idle. My dad kept saying the comps were just "learning" the new air/fuel mix. His 08 "learned" quicker than mine and he went for a test drive. I watched mine rev-low idle, rev-low idle, then die. Did that 3 times. Started again and it revved really high then went to normal idle. I took it for a test drive just as my dad was getting back. I could say my butt dyno could tell there was something there that wasn't there before but not a V8 either.

Then the event happened. Check engine light and the traction control said it failed.
I got back to my dads house and his engine light was on as well. We went back through the instructions checked everything and noticed on the Jet sensor it said in bold MAKE SURE THE CHECK ENGINE LIGHT IS NOT ON! nothing else. nothing saying if it is..... this is what you should do/not do, check etc. Thanks JET. Tried calling them nothing. Website nothing. We checked how the stock sensors are in the stock intakes and sure enough we put the new ones in backwards in the k&n.
You can't just flip it around either the whole mounting bracket in the k&n has to be flipped, then the sensor.
The odds we both did the exact same thing not working side by side on that particular part?
Same genetics maybe?
Making sure the neg battery cable was disconnected to reset the computer we fixed the problem and restarted them.
Not a single issue no high rev low idle die sequence. Maybe because the air sensor isn't backwards?
No engine light or Traction control failure.
And the butt dyno noticed an improvement as well.
Still his 08 has more felt power than my 07.
I have driven my to work a few times now and around town. It is definitely more drivable. Call me crazy but the mpgs went up 2-3.

We are now looking for step 2 exhaust, maybe headers.
Step 3 ECU tune

I have read on the forum people really vouch for the efans from pcmtuneforless.com can anyone second that? real gains etc.

Anything else I can do for gains aside from a supercharger or turbo?
I like the h3 a lot after getting used to it and the fact that I'm over 20 mpgs is a huge bonus but really need more ponies before I throw on some aggressive tires.
Thanks guys

 

so you had it a few days and were able to do an accurate mpg comparison huh!.

i drive my 2nd stock 3.7 and i cant use all the power. i push lightly and it takes off. if i really push its just too quik for normal driving and mpg will suffer.

your comparison is a good one. i got a hemi loaner from carmax where i got my used 07 when it needed a minor svc. the hemi jumped out from under me like some of your more powerful vehs. but,,,after driving my h3 again and getting a feel for it i could never sensibly hit the gas hard to duplicate the off idle jack rabbit start of the hemi,and who needs it??
most people get into their vehicle and drive at a normal pace,occassionally booting it to get away from a idiot on a ramp who doesnt know how to merge. i rarely need to stab the gas.
hey,i had a 460 stang,,,i know how it can feel, but i never needed that,it was just for fun.

if all the mods really boost the output way up,you will find yourself feathering the gas!, like the hemi!!

the i5 has more power than you can use sensibly, like ALL modern cars

 

I really don't find anything wrong with the 3.7 except for towing anything up a hill.

 

TB Spacers = paper weights. Have you thought about fuel saver magnets? or.... the Brooklyn Bridge?


IMHO the PCMforless tune is the way to go for the I5s, you pick your own custom tune. With Jet, you get what they sell, and what exactly is that?


Welcome to the forums.

 

Hello from MI.

First post and you are telling us that products that have not really worked (except for the K&N) or improved performance AND MPG for anyone else have given you more power AND MPG????

Hmmmmm...... think I'm gunna call you Krazy.

Buy the way you will have to remove the Jet Chip if you get a proper PCM tune. All the Jet chip does is "fool" the PCM with false readings.

 

Tom
I'm sorry if I have struck a nerve.
As far as MPG comparison: I have had the hummer for a few weeks now I drive more than 50 miles round trip to work everyday and have made a few trips to SLC which is near 40 miles 1 way. In the last few weeks I have put a few hundred miles maybe 500-600. I'm not sure how many miles you need to make an mpg check? I fill up then drive 150 or so miles. Fill up again check how many gallons/miles. done. I don't need to drain the tank to get it. Yes its not a long drawn out study over months but I was consistantly getting 18 mpg before the intake etc and now after its getting 20.5-21 with the upgrades. I have been very careful to drive the exact same. (baby it)

I don't try to hot rod the h3 either. I was simply noting as many many others have, it's a heavy vehicle with a 5 cylinder which makes it a little sluggish. I have especially noticed it being underpowered trying to get on the freeway, quickly matching 65-70 mph is not possible with some of the on-ramps here and the I5 as it sits.
I really disagree that it has more power than I can use sensibly.

 

I never claimed that the improved performance was from any one or the other product. It all may be the k&n. I have had nothing but good from the 63 series in the past so thats what I based these modifications off of. I wouldn't know exactly what did what as I did them all at once. All I can say is there is a noticed improvement on the engine performance and yes mpg. I will keep a close eye on it for the next month and give an update. Like I said above, where I drive and how I drive it was a solid 18 mpg before and now its over 20. Hopefully I can keep it up there. To get this awesome vehicle AND get 20 mpgs?! I would be happier than a puppy with two...
Also it's not the jet "chip" its the jet mass air flow sensor.

 

Wow, some of you guys were a little harsh. Can't disagree with anything, but still...

Welcome! What part of UT? There are a few of us in the Layton area.


I have to disagree. Sure, it will get you where you want to go and 4low has enough gearing and torque for the steepest offroad climb. However, more low end grunt would allow better acceleration without forcing the tranny to downshift and run high rpms. Big hills and a 75mph speed limit = tranny hunting or driving well under the speed limit. When I step up to 35s I'm sure it will be worse.

Based on what I've read here and other Hummer forums, I have confidence that an Airdoc, pcm4less, and possibly exhaust would help with some or all of these shortcomings. Completely stock, power is adequate but certainly not more power than one can sensibly use. At least if you are like me and don't want to rev the whizz out of the engine - I want more power without being in a lower gear. Maybe it's more of a shift point issue than a power issue? Either way, the only reason I haven't bought a PCM4Less tune already is because I plan to upgrade tire size in the spring and want to do tires, airdoc, and tune at the same time.

 

I live in clearfield just south of the freeport center. I drove passed a white H3T this morning sitting in someones driveway this morning. If you are in that part of clearfield may have been yours?

Glad to see someone else can appreciate that the actual freeway speeds here are 75-80+ mph

Thanks for the heads up on the Airdoc. I saw that stock resinator box and couldn't imagine why that would be a good idea. Will they work with the K&N intake already installed? It looks like some cutting might be in order.
Yes I hate having the engine revv, work so hard and tranny search when I could give it a hand to add some hp. I plan on having this thing for a long time so anyway that I can take a load off the engine I'm game.

I'm waiting for the tune as well until after the exhuast and maybe headers.

 

Yup, that was me. Crissam Meadows, just across Antelope from Freeport. It's the only white H3T I've ever seen in person. I'd challenge anyone in a stock I5 H3/H3t to drive from SLC to Park City or even just down to Thanksgiving point and not long for more low to mid rpm power.Hate to say it, but the answers you seek can be found by searching. All my info on power/mpg gains and improved shifting are second hand through forums like this. I have read a lot so I'm fairly confident, but instead of passing on what I remember others saying it's probably best to just read their posts.

Do the PCM4Less tune last. They have a number of questions so the tune can best match your mods. This includes tire size - they can adjust it so the speedo is compensated for non-stock tire size (main reason I'm waiting).