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Old 06-20-2012, 10:42 PM
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Does the 5.7L MDS Hemi have a knock sensor?

I just tried my WK with a couple of new engine mods: Air Aid Jr. kit and DiabloSport inTune canned 91 Octane tune. I'm using 92 Octane gas, (Ron + Ros)/2, that is the highest octane fuel I can get.

Overall the result was very good, I did not expect this much improvement from this basic bolt-ons, these are really cost efficient mods.

However, now I notice a much different engine sound at part throttle acceleration and at around 2500 rpm. It sounds like a Growl , or could be a constant engine knock . It does not sound like that at higher revs or under full throttle. It is not that loud, I can hear it with the windows up only, with windows down, the wind noise does not let me hear it.

Is this something normal or should I worry about it? Does the engine have a knock sensor and how does it work and prevent ping?

Any help will be appreciated, thanks.
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Old 06-20-2012, 11:30 PM
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Re: Does the 5.7L MDS Hemi have a knock sensor?

2 knock sensor on bottom of block near the exhaust manifolds
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  #3  
Old 06-20-2012, 11:57 PM
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Re: Does the 5.7L MDS Hemi have a knock sensor?

Using the datalogger function, you can log knock retard.
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Old 06-21-2012, 08:51 AM
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Re: Does the 5.7L MDS Hemi have a knock sensor?

The noise is probably from your CAI, when operating in 4 cyl mode. The stock intake is very well designed, optimizes low and mid range torque, where the motor operates 95% of the time, and muffles the sounds when MDS kicks in. I took of my CAI and went back to stock and it sounds, and runs MUCH better. CAI is a waste of $ and worsens throttle response.
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Old 06-21-2012, 12:37 PM
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Re: Does the 5.7L MDS Hemi have a knock sensor?

Quote:
Originally Posted by dmsfun View Post
CAI is a waste of $ and worsens throttle response.
I disagree with this statement. I snagged an OEM intake off of an SRT8 WK and my throttle response definitely improved. And so did my mpg.
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Old 06-22-2012, 12:44 AM
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Wink Re: Does the 5.7L MDS Hemi have a knock sensor?

I also recently installed an airaid CAI, straight-thru muffler and run on 91.
The 2500rpm "growl" is also now noticeable with my 5.7 Hemi. The exhaust note sounds really great. I have also noticed an improvement in throttle response and general performance. I simply do not agree that the stock filter box and intake resonator is "better" - at least not in my case ?
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Old 06-24-2012, 08:56 AM
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Re: Does the 5.7L MDS Hemi have a knock sensor? Resolved.

Thanks for the info Scott and Ryan .

I tried the Data logger on a couple of runs and it shows cero Knock retard all the time, so I guess the GROWL at 2500 is normal.

DMSFUN, I do not have the standard CAI, it is the Jr kit, this keeps the stock housing, and its fresh air funnel, replaces the filter and the resonator in favor of a better flowing plastic pipe. The datalog shows clearly how intake air temperature drops as speed builds up. It works just fine.
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Old 06-27-2012, 08:58 AM
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Re: Does the 5.7L MDS Hemi have a knock sensor?

I tested both intakes back to back with a cleaned, stock TB and then with the MM 85 mm TB. Most important when doing any comparisons, both intakes had a NEW, CLEAN filter. You cannot compare a stock intake with a used filter to a CAI with a new, clean filter !! A dirty filter chokes the Hemi quite a lot, as I noticed a big improvement after installing a new panel filter in the stock housing. The stock intake resonator works great; you don't get that intake growl in MDS mode and all that other noise from a CAI. I didnt test the SRT or Airraid intakes, only the AFE Stage II, which is an enclosed filter CAI. It had worse tip in throttle response at all speeds, particularly at lower RPM's. Only in the case of flooring it and running the 1/4 mile at WOT did I see any advantage to the CAI, not very useful for street driving. I unhooked the battery for an hour or so to reset the ECU each time, then drove with each intake for a few days. The stock intake wins for street driving, hands down. The biggest improvement in throttle response though, is from the 85 mm TB compared to the stock TB.
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Old 06-27-2012, 09:33 AM
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Re: Does the 5.7L MDS Hemi have a knock sensor?

I personally like the extra growl/noise from a CAI. I use a K&N drop-in filter and clean it every oil change so I've had ample opportunity to test the mpg. After adding the SRT8 OEM CAI, I noticed an immediate avg mpg increase of 1. Considering that I do mainly city driving, going from 11.5 to 12.5 mpg is a pretty big deal.

Notably, I also, removed the stock debris/water collector from the OEM box and added a CAI flex tube that routes to the front of the grill for additional air intake/less restriction.

Another benefit of the CAI was that the IAT dropped significantly, likely due to less heat bleeding into the stock rubber material of the SRT8 CAI. Via my Scangauge II, my IAT now stays within 5-10 degrees of ambient, unless I'm stopped at a light for an extended period of time.
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Old 06-27-2012, 10:39 AM
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Re: Does the 5.7L MDS Hemi have a knock sensor?

Brent, all of your findings pretty much mirror those I have experienced. The K and N's work better when they're a little dirty though. I normally clean/re-oil at 30K intervals. I use a modified LX SRT-8 airbox on mine, with the additional air inlet and a K and N. I also have the Challenger IAT Sensor, which samples from the center of the tube. On the highway, mine always runs at ambient. On my Hemi LX, I have also have an SRT airbox, but have made a double walled, insulated tapered (5 in. to 3.25 in.) tube for it, and it will only get down (5-7*) to about where yours does. I have tried everything to get it to ambient. I have concluded that the big difference is IAT Sensor location and length. The WK's is near the airbox and the LX's is just in front of the throttle body. Apparently heat soak through the tube and surrounding engine components, and sensor length are the reasons for the increase. I'd put a Challenger sensor on the LX, but the connector plugs are different, and I haven't had time to mess with it. Besides I have a manually adjustable IAT (another one of my tinker jobs) on the LX, so I can set the temp. (on the fly) to anything I want.
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Old 06-27-2012, 10:56 AM
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Re: Does the 5.7L MDS Hemi have a knock sensor?

Quote:
Originally Posted by jeepgcoman View Post
Brent, all of your findings pretty much mirror those I have experienced.
Funny enough, I'm pretty sure it was your build that I followed when I made the decision to run the OEM SRT8 box with additional inlet. I'll have to look into this IAT centered in the tube though for another project.
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