Noisy GM 3.6?

[tomg]

Drove a rental 2013 Impala with the 3.6 engine with only 13K miles. Motor seemed pretty

noisy during passing and merging acceleration. My 2008 Impala with the 3.5 engine only about

half the noise under the same circumstances.

My question is, will the new 2014 Impala have the same engine, because I was considering

on buying this car. Maybe I was wrong on the amount of noise of the 3.6!! Any throughts?

[Drew Dowdell]

The amount of noise the 3.6 makes seems to depend on the car it is installed in. In the Cadillac XTS and Buick Lacrosse, it is fairly hushed. The 2013 Impala you drove has been dumbed down a bit and might have sound insulation removed as it is fleet only. The 2014 is an entirely different car, but yes it will have the 3.6 optional and the 2.5 liter 4-cylinder standard.

[vonVeezelsnider]

In city-speed acceleration I noticed a whistling noise in the two I have rented...

[ponchoman49]

I have driven 3 2012's 3.6 Impalas and did not think any one of them was noisy even in full throttle. However when first started the direct injection could easily be heard outside the car until the engine warmed up. The three I drove were LT and LTZ models. maybe you had a fleet spec base LS version with less insulation.

[dwightlooi]

Actually, I find all the Direct Injected 3.6s to be noisy. It's noisy in the Camaro, it's noisy in the Buick Lacrosse, it's noisy in the CTS and, yes, it's noisy in the ATS 3.6. I have not driven that engine on the Impala (new or old). It seems that the DI engines are significantly noisier than the 3.6 DOHC w/ port injection (Saturn Aura). It is sort of a "gggrrrr" noisy in the low-mid frequency spectrum. The 2nd gen DI (LFX) version as opposed to be 1st generation (LLT), do not seem to be significantly better. They seem to have succeeded in moving the noise frequency to a slightly higher frequency but it's still noisy. Which was kinda disappointing because they took an active effort in dealing with DI noise during its development -- or so they claim. In this regard the non-DI 3.6 DOHC was a more refined engine. In fact, the 3.5 and 3.9 Pushrods were more refined engines.

In the ATS, the engine is actually pleasant sounding when pushed because of the exhaust note and because induction noise drowns out the DI clatter at higher rpms. At 1500~2500 rpm under load though, the engine is annoying. This is particularly bad because that is your "cruising" RPM at legal freeway speeds. GM is not unique in this regard. Go drive a DI turbo 2.0 GTi or A4 and you have the same "ckckckck" sounds at idle and a "gggrrrrr" at lower mid rpm ranges. I used to not believe that this could be an issue but having driven all these cars over time, I now understand will Lexus uses both Port and Direct Injection in their engines. Port Injection for quiet idle and low-mid throttle, low-mid rpm acceleration. DI cuts in at higher revs and wide throttle positions for the additional performance.

[chevelle454]

My LFX is very quiet. It is a 2012 Impala LTZ. I also drove a 2012 CTS and it was quiet also.

[Drew Dowdell]

So a V6 Lexus will end up with 10 - 12 injectors?! How very Benz like of them.

[dwightlooi]

So a V6 Lexus will end up with 10 - 12 injectors?! How very Benz like of them.

12 of them. 6 Port and 6 Direct Injectors. One high pressure piston pump for the direct injectors and another for the port injectors. There is no clear cut over between the two. Basically, the port injectors remain in use even after the direct injectors are activated such that they are both in use at some points on the fuel map.

[hyperv6]

The simple answer is when you inject fuel into a cylinder it takes high pressure. To do this you needs high powered injector and high pressure pump on the engine.

Keep in mind you are dealing with injector pressures of over 2000 pounds vs. 17-23 pounds of a normal injector.

GM went early with little insulation on many of the DI engines and now they have started to work on noise insulation. MY 2.0 DI was retro fitted with a rubber foam cup that cut down the noise on the pump and while the injectors ares heard out side on the inside they are not noticed. I do have a cold air door that make a loud air rush sound till the engine has run for about 3 min.

On my 3.6 DI there is no noise inside till you rev it up to about 4500 RPM and higher. It is just an engine rev sound.

On the injector pump and injectors they have wrapped them in more insulation than earlier models. Injector and pump noise has never been an issue on the Terrain and Nox web forum.

Might note they buried the pump on top of the intake of the new LT engine. They did their best to cover the noise. I think with each engine we will see improvements on DI noise.

The only DI worry has been carbon build up on the intakes. Since no fuel flows over them Carbon has been an issue for some. GM says they have it covered but still some have carboned up at 8,000 miles.

This is one area to watch as in the past the intakes were cleaned with incoming fuel and today no fuel passes over them. I suspect GM has some over lap but at low RPM driving they never catch any fuel with cleaners. The harder you drive and more RPM the better may help?

The oil is just what little that passes the guide to lube it and normally was cleaned off but today it carbons up with the heat. The Exhaust will just burn off as normal.

Audi and VW have had major carbon issue.

[dwightlooi]

I urge you to drive a 3.6 HFV6 w/o DI and one with DI. You CAN definitely tell the difference in engine note. The DI has a distinctly less refined sound. I am not talking about the tick tick tick you hear from the outside, rather it's the grainy "gggrrrrrrr" that the DI engine make at 1500~3000 rpm which is absent in the port injected engines.

The pump on DI engine is actually not the biggest noise source. It's the injectors themselves slamming shut under over a thousand pounds of pressure. Honestly, I think GM should revive "throttle body injection". Yes, it's somewhat imprecise and doesn't offer perfect fuel distribution from cylinder to cylinder and no it's not every knock resistant for that reason. But, high knock resistance is not always important -- it's only important under moderate to high loads and at lower rpms. If you retain Direct Injection for performance and under load emissions, but add a single throttle body injector, you can dramatically cut down on idle and low speed noise, provide for valve cleaning and do so at a lower cost and complexity compared to direct + port injectors.

[Drew Dowdell]

Bring back TBI?

[David]

TBI had it's day. That shipped sailed and we need to continue to find better ways and improve on current versions.

[Robert Hall]

Needs more/better sound deadening materials in/around the engine compartment, I would think. I drove a rental '12 Impala last year w/ the 3.6, didn't really notice much difference from previous Impalas I'd rented other than it seemed quicker...but I had the AC on and stereo up..

Edited March 20, 2013 by Cubical-aka-Moltar

[dwightlooi]

Well, all things being constant, DI is the biggest downgrade in vehicle refinement in the last few decades. Not that it doesn't have tremendous advantageous going for it. Refinement however is not one of them.

[David]

Well, all things being constant, DI is the biggest downgrade in vehicle refinement in the last few decades. Not that it doesn't have tremendous advantageous going for it. Refinement however is not one of them.

Dwight, I am surprised as this is one of your shortest comments and I enjoy reading your technical insight.

So other than refinement, what other specific issues would you have with this? I have changed my 94 Suburban from TBI to a FuelInjection which allowed me to convert to CNG so it runs on both and runs very well.

[dwightlooi]

Well, all things being constant, DI is the biggest downgrade in vehicle refinement in the last few decades. Not that it doesn't have tremendous advantageous going for it. Refinement however is not one of them.

Dwight, I am surprised as this is one of your shortest comments and I enjoy reading your technical insight.

So other than refinement, what other specific issues would you have with this? I have changed my 94 Suburban from TBI to a FuelInjection which allowed me to convert to CNG so it runs on both and runs very well.

Well, it's really very simple. If you replace Port Injection with Direct Injection in an otherwise identical engine. Refinement is notably reduced due to a significant increase in injector noise.

DI Advantageous

• 10% Higher Compression Ratio
• Potential to implement stratified charge lean burn
• About 3~6% higher power & torque -- all else being equal
• 2~4% better fuel economy

DI Disadvantageous

• Significant Noise Increase from high pressure injector closures
• Slight cost increase from 300~1200 psi fuel system hardware
• Carbon build up on the intake valves and intake tracts are not cleaned up fuel additives
• Placement on injectors sometimes compromise optimization of intake runner design

For maximum performance, efficiency and refinement, a dual injection (port + direct) is best. This however is expensive and, some will argue, unnecessarily complex.

[Drew Dowdell]

So the Lacrosse and XTS just have lots of extra padding.. because they are super quiet inside.

[dwightlooi]

So the Lacrosse and XTS just have lots of extra padding.. because they are super quiet inside.

Basically, yes.

But, super quiet is relative. I didn't find the XTS 3.6 to be "super quiet". I find the engine to be a little coarse and the interior noise under acceleration (especially between 1500 and 4000 rpm) to be less refined than in a IS, ES, GS, E-class or 5-series.

Edited March 25, 2013 by dwightlooi

[hyperv6]

The fact is the when released GM did little or nothing on the first DI engines to cover the noise of the pump or injectors. Most of the noise is from the hi pressure pump on the engine and today most are encased in a foam box that muffles the noise. The injectors often buried under a plastic intake that removes most of the noise.

GM in 08-09 had TSB's to address the noise issues and some option parts like the covers for the HP pump to remove much of the noise.

Keep in mind engines like the 3.6,3.0 and Ecotec were all not designed originally as DI engines do they lacked much of the new things that GM is doing with the new LT engines.

I own a 3.6 port injected 08 engine and a 3.0 DI 2012 engine and I can tell you inside there is no perceived issue with noise what so ever on either. Both engines have a growl to them most due to the intake at high RPM. The fact is there is some noise to the HV engine that some like in the Camaro and some hate in a XTS. The noise is subjective and as a whole few in the public have noticed or complained on the inside of the car.

Now early on many complained about the ticking noise not understanding the injection system and when informed of the DI system they were ok. Most thought of it as a bad lifter. So the reality most are fine with this system and really have no issues with is from behind the wheel and few have issue outside any longer with the improved isolation of the sound.

It is true the system is more expensive and if you play with it and are not careful can give you a painful and dangerous shock. The voltage is much higher in this system and can give you a thumping. The lines are one time use and need replaced if opened up but then how often do you really need to open a fuel system anymore?

As far as fuel placement I have seen no issue with it as most new pistons have a spot to help with fuel flow and the fuel is from what GM claims placed where they want it. This is more true on the new LT engines as they did more work on the air and fuel flow on this engine than any other GM has ever done. I expect the other engines will see enhanced improvements with each upgrade. The new Eco has already seen it now.

The bottom line the DI system is here to stay as the improvements well out weigh any issues. For better MPG and better emissions it is a must. Also the smaller engines work well with it as they can increase the compression of the engine with out having to go to high test fuels.

Also DI loves and helps control many issues with fuel in a Turbo engine. It improves it in performance, emissions and durability as it can provide fuel as needed and has many other benefits as outlined by MFG.

The only real unknown at this point is the carbon issue on the intakes and heads. All cars seep a little oil to keep the valve guide alive. In the past the fuels cleaners help keep this in check. Today no cleaners flow but GM claims to have addressed this. In may contacts with many people who own DI GM cars I have only see a few issues with carbon build up and one GM TSB on the subject. GM seems to have better control than VW/Audi did but I still see one with this issue once in a while in a GM engine.

I suspect that people who drive and never see much RPM may have the issue more than an engine driven hard. I was told that GM leaves the intake open just a hair and injects some fuel to get a little fuel in on top of the intake valve. But I have not seen this in print and I am not sure if this is what they are doing. I know it can be done but how effective? Until I see how GM is really addressing it I will keep looking for info on this.

Note too I have had the cover off both my HV engines and the new 2012 has much more insulation on it to dampen engine noise in general than the 08 Bu. GM looks like they are making an effort to quiet valve train noise as the V covers have sound deadening material on them.

As for my DI on my Eco the only hash noise that really sounds bad is when I first start it and there is a door that opens in the intake and it sounds like a vacuum cleaner and makes a horrid noise like something is wrong. It shuts in less than 30 seconds but after that the pump makes a little noises and the injects just a little. In side the intake is heard more than anything and most Turbo owners complain that the turbo is too quiet and the blow off valve is also too quiet since you hear little inside. The HHR is not blessed with much insulation and DI is not an issue in it. Note I did retro fit the cover on the pump and it helps.

Until there is something better they will just refine the DI system. I am waiting for the aftermarket to address it more with the new LT engine. Right now there are many companies working on and coming out with kits to eliminate the cylinder deactivation. Lingenfelter and the cam companies are the key players here.

[David]

So the Lacrosse and XTS just have lots of extra padding.. because they are super quiet inside.

Basically, yes.

But, super quiet is relative. I didn't find the XTS 3.6 to be "super quiet". I find the engine to be a little coarse and the interior noise under acceleration (especially between 1500 and 4000 rpm) to be less refined than in a IS, ES, GS, E-class or 5-series.

The 2004 SRX I got my parents seems quitter than the new 2nd Generation SRX from an engine stand point.

[Guest Chris]

My wife's 08 Enclave makes the annoying "ticking" from the DI system (self diagnosed). This is a very loud and embarrassing noise. Here we are driving a $45K vehicle that sounds like it's not taken care of. I have read on multiple forums (camaro, cadillac, buick, etc.) that they have similar issues and share my opinion. It makes me want to dump the car and never buy from GM again.

[Drew Dowdell]

Have you taken it to get it looked at yet? I admit that I can hear the ticking, but it's fairly soft

[Guest Dan]

I have a bit of a knock on my 2012 impala 3.6 with 20, 000 miles you can hear it in drive as you take off from a stop under normal aceleration.....any ideas

[Drew Dowdell]

Does it change if you put higher octane fuel in it?