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So what are the drawbacks of an underdrive pulley? I mean if it were that easy to increase performance just by using a different size pulley, the manufacturers would be doing it! There have to be some downsides - just curious what they are (less current via alternator, less power going to power steering pump, etc)....

Thanks.

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Pulley question

Jtrosky,

Cost can be one? But I think they just stick a cost effective pulley that works in a multiple application.

So far i travel about 900 km with the pulley and no issues. AC is working well and other electriques also. The only thing i notice his my lights are slightly dimmer. To be safe, before winter i will install a battery with more CC. Maybe the battery from the 9C1 or a Eliminator from CT.

The rain just stop about 30 minuntes ago and the sun is trying to come out! I wll go to the track around 18h00. My fingers are cross.
 

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I was thinking also about filling up the intake front reservoir, but not sure i want to risk debris or chunks that may enter the engine with time. I'm thinking of swapping my stock intake to a Camaro intake! But do do so, i will have to relocate the battery and customize so fitting and/or intall a catch can etc. That that would be done in winter. But those down pipes from that shop in Philly will be my next mod.
 

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Discussion Starter #24
go look up Jason at JACFAB.com he's on the Camaro forums, and has gotten some great gains by taking out the air diffuser and filling in the oil dip on the Camaro intakes. He is supposed to be putting some playdough in an impala intake he has to test and let me know what kind of gains the flow bench shows. he already sent me the diffuser removal info which showed about ~4% increase in flow through the intake over stock.


Also he told me the bolt pattern for the impala intake and Camaro intake is different which is why his "extendolator " wont fit our cars... but he has a prototype "extendolator" for the impala that he should be sending me someday to test and review over here on our forums.


I believe the Y pipe you are looking at keeps the stock downpipes with cats. if you check out my thread


http://www.impalaforums.com/8th-gen-engine-performance/600649-porting-12-13-3-6-lfx-down-pipes.html


you can see the restrictions I removed around the inlet part and the o2 bungs. I think it would be worth doing if you are or are not doing the Y pipe replacement. AND... if you ever do get the Y pipe done please go the track afterwards and let us know what you run. I'm very curious as to what kind of gains are had from it. If they are good enough I would get a custom set up as well.


All the 1/4 mile tracks around me have closed over the years so its difficult to get to one anymore.
 

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Great news about JacFab, I did contact him about a year ago, and he did mention the same issues with the impala intake difference, please advise me when you do receive it, one thing i found out is the engine is affected by heat soak, if i cool down the car for one hours, i will have a great ET and mph, but, you lose anywhere from 0.45-0.85 sec. after each consecutive passes.

Speaking of passes, with the heat and humidity advisory, my best pass was 14.333 @97.88 mph, but my worse pass was 14.557, i did a total of 8 passes in about 4 hours. I'm thinking of going full synthetic on my next oil change AC Delco dexos oil is a synthetic blend, so i'm thinking going with the Pennzoil Pure Plus 5w30 oil. Maybe that should help?

I look into cleaning around the bung, but if I go decide to upgrade the cat down-pipe, i will get the heads exhaust flange/plate and build a new exhaust down pipes.
( CBM MOTORSPORTS CHEVROLET 3.6 LITER ALLOYTEC LFX EXHAUST FLANGES )
 

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Something else to consider - I've been reading that an underdrive pulley can cause more engine knock. Have you been monitoring KR values at all since the underdrive pulley was installed? I've been monitoring KR valeus on my stock 2012 Impala and even with 93 octane gas, there is significant KR. I'm just wondering if the KR levels change at all with the underdrive pulley.

It's amazing the amount of information you can obtain from scanning your vehicle. In my opinion, if you are after all-out performance, an HPTuner device is an absolute must. Between the scanner app and the ability to correct issues you see in the scanner logs, you should really be able to take advantage of the mods you are doing. You may be surprised at what you see if you start scanning your vehicle after all of the performance-related mods you've done.
 

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I had 0 kr before my water pump underdrive pulley and 0 after, but I have alot of mods and a good tune to help with my 0 kr.
im also a 3.8l not the 3.6l
 

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Yeah, I've never monitored any of my 3.8's, but it's my understanding that these newer high-compression, DI engines come from the factory with lots of knock. I couldn't believe how often I see KR in my 2012 - regardless of whether I'm using the Overkill tune or the stock tune. I'm just thinking that there may be a lot of KR going on with the 3.6's - and if you can reduce at least some of it, you may help the overall performance (if you're looking to squeeze every bit of performance out of it like they are talking about in this thread). I've found that just removing a degree or two of timing can stop up to 6 degrees of KR - in other words, when the computer does detect knock, it usually "over compensates" for it, thereby reducing performance.

Also, you could at least confirm that the mods aren't causing any additional knock which could cause long-term engine issues. While the computer will reduce timing to stop the knock, it still has to detect knock before it can compensate for it....

Not sure how the Trifecta tune comes into play here either though - I know that they mention that they treat knock differently - only way to be sure would be to datalog and see whats going on though.

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3.8's stock from factory knock badly also, but exhaust mods(headers or plog&3'' downpipe) and a good tune kills the kr quickly
 

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Interesting - I didn't realize that the 3/8's also had significant knock from the factory. Whenever I review other peoples logs for NA pushrod engines (not Impala-specific), I see very little KR in their logs, so I just assumed that the amount of KR I'm seeing was only an issue with the newer direct-injected engines (I have read that the DI engines tend to have more KR than older non-DI pushrod engines in general).

One of these days, I'll have to connect my HPTuner up to my LaCrosse and log some info just out of curiosity - I'm been meaning to read the computer anyway, just to see what the programming looks like.

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5-7 kr from factory on most n/a 3.8's from what i see on the grand prix sites
 

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Hello, Will.

My name is Marc and I also have a 2012 impala 3.6 LFX. I am contacting you because I am interested in upgrading my underdrive pulley like you did however, I am troubled on the install process. In your opinion what is the best way to install the product? do i drop the subframe and work my way up to the pulley or detach the hoses from above the pulley and work my way down?

Thanks.
 

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Mark, the install without the proper puller can be tricky. but, the pulley is accessible by simple lifting and removing the passenger tire. Please let this forum know witch Gate belt you will be installing (P/N).

Good luck and enjoy the faster pick-up and power across the RPM's
 

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I might be beating up an old topic but I wonder if this pulley would work on the 3.5/3.9 impala I believe the over all diameter of the under drive pulley is 6.580-6.563 give or take and the lfx is 6.340 same as the 3.6 g6 ..just wanted some in put before I make the purchase ..Thanks in advance guys
 

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They have different p/n I ran the oem part the power bond and Dorman they all have a Lil difference in over all diameter but the bolt in the and sleeve look to be the same and I figured if it was used in the old 3.6l model it might be interchangeable.. thanks for the speedy input! I think I might need to bite the bullet and hope it sticks lol
 

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Hey guys, I know this is an old thread but I have a concern:

I have a 2014 Impala Limited and I would LOVE to install the UDP.. and it does fit my car. BUT I am unable to find it anywhere. If someone knows where to find it, I would be incredibly grateful.

Thank you!
 

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As far as I know I am the 1st person to put one of these on an Impala. I wasn't 100% sure it would fit. I looked on rock auto to determine if the Impala and Camaro pulleys PN# were the same, they were not, HOWEVER there was a premium OEM replacement pulley pn# PB1509N, and it was listed for both cars.


I figured that if one would fit both cars, then the SLP underdrive pulley (made by powerbond) would fit as well.


From pictures I have seen the only difference between the Impala pulley and the Camaro is the Impala has 3 spokes and the Camaro 6.


They are supposed to be good for 6whp and 4wtq.


Chevy actually sold them on the SLP 327 Camaros from the factory, so they will not void the warranty.


Stock pulley is actually lighter, about 5lbs, vs. the SLP at 6 lbs. Which I thought was strange, but after researching things, the powerbond UD pulleys for Corvettes and other GM v8's are all heavier as well, the gains come from underdriving the accessories, and since the weight is closer to the center of the HUB the parasitic loss from rotation inertia, is the same or better than stock.


I just put it on last night, but the car does seem a little more responsive, and I have had no charging issues, I do not however have any subs or amps.




pulley is PN# 100232A, they normally go for about $250 but I got it on sale around cyber Monday from Marylandspeed.com for around $200.


It took me a couple of tries, but the belt you want is pn# K060926.
Hey I Know this post is like 5 years old but do you know if the pulley u posted is still available anywhere?





pics of stock vs. SLP
 
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