Is 11.5:1 CR Typical for DI Engines?

[SubLGT]

I was looking at the specs for Honda's direct injected "Earth Dreams" 3.5L SOHC V6 engine, and the compression ratio is shown as 11.5:1. Just curious how this compares to other direct injected engines.

Also, I could not find out what strategy Honda has taken with this engine to avoid the buildup of carbon on the intake valves. Anyone know?

This V6 puts out 280HP @ 6000rpm and 262lb-ft @ 4700rpm (in the 2016 Pilot). It may be higher in Acura applications, I have not checked. The 2.5L DOHC turbo 4 in my 2005 Subaru puts out 250HP @ 5600rpm and 250lb-ft @3600rpm, and I am somewhat surprised this new Honda V6 does not do better than 280/262. Is 300/300 not doable in a 3.5L n.a. V6 engine?

 

[horse123]

Compression ratio can vary a lot. I wouldn't use it as a comparative spec unless you're planning on building a track car or something.

 

[Quattro Pete]

Originally Posted By: SubLGT
Just curious how this compares to other direct injected engines.

The supercharged 3.0 in our Q5 has a compression ratio of 10.3:1.

 

[racer12306]

Chrysler puts out over 300 with their 3.6L in the Ram, iirc.

Honda could make this engine put out 350hp is they wanted it to, but is it necessary is the real question. This engine is probably shared between the Accord, Ridgeline, Pilot, Odyssey, and their Acura counterparts. Do these cars need over 300HP?

 

[supton]

Originally Posted By: racer12306
Do these cars need over 300HP?


Do they need 300hp? To be competitive, yes. To get the job done, outside of sales, no. My opinion, of course. But it can be nice to ones foot into it and have results now.

 

[Hokiefyd]

Originally Posted By: SubLGT
This V6 puts out 280HP @ 6000rpm and 262lb-ft @ 4700rpm (in the 2016 Pilot). It may be higher in Acura applications, I have not checked. The 2.5L DOHC turbo 4 in my 2005 Subaru puts out 250HP @ 5600rpm and 250lb-ft @3600rpm, and I am somewhat surprised this new Honda V6 does not do better than 280/262. Is 300/300 not doable in a 3.5L n.a. V6 engine?


In the MDX, it is slightly higher...290 hp @ 6,200 and 267 lb*ft @ 4,700. There may be some changes in exhaust or intake tuning, or some separation for marketing reasons. It's competitive with others in its general class:

Chevy Traverse 3.6L V-6: 281/288 hp and 266/270 lb*ft (no speeds given)
Dodge Durango 3.6L V-6: 290 hp @ 6,400 and 260 lb*ft @ 4,800
Ford Explorer 3.5L V-6: 290 hp @ 6,500 and 255 lb*ft @ 4,000
Nissan Pathfinder 3.5L V-6: 260 hp @ 6,400 and 240 lb*ft @ 4,400
Toyota Highlander 3.5L V-6: 270 hp @ 6,200 and 248 lb*ft @ 4,700

Going only by spec sheet, the GM's numbers look good, but we don't know what engine speeds where those peaks occur. Dodge's Pentastar puts out good numbers, but at higher engine speeds. Ford's engine may be a good compromise -- higher peak hp and speed, but a torque peak at a lower engine speed. The Nissan and Toyota engines are both below average based on peak numbers.

But you can't go only on spec sheets. The "character" of all of the engines may be very different -- peak numbers are good, in my opinion, only for bench racing.

300 hp is certainly doable in a V-6 engine. 300 lb*ft of torque is probably asking a lot out of 3.5 naturally-aspirated liters. Then you also get into the question of transmission durability -- at least with transverse FWD applications -- and torque steering issues. 300 hp seems to be near the limit explored in production vehicles. I owned two Northstar Cadillacs (that were basically 300/300), and full throttle could be a little wooly. Anyone with a supercharged 3800 can probably attest to the fact that making power and torque is easy -- but getting the front tires to harness it effectively is more difficult.

 

[Quattro Pete]

Originally Posted By: racer12306
Do these cars need over 300HP?

Probably not, but a heavy SUV or minivan with full load on board (or towing) could probably use it more than a mid size sedan.

As supton mentioned, it's more about keeping up with the competition in marketing collateral these days.

 

[Swift101]

I don't think DI has anything to do with it. My Sonata 2.0T (DI) has a compression ratio of 9.5:1

 

[rjundi]

Originally Posted By: SubLGT
The 2.5L DOHC turbo 4 in my 2005 Subaru puts out 250HP @ 5600rpm and 250lb-ft @3600rpm, and I am somewhat surprised this new Honda V6 does not do better than 280/262. Is 300/300 not doable in a 3.5L n.a. V6 engine?


One aspect you forget is Pilot is running regular fuel and get 19city/26MPG with AWD.I believe the MDX does 290HP but they added premium requirement to that.

300HP I have in my 07 MDX is great for heavy load(5 people + skis) with ample passing power but not necessary. I'd give up 30-40HP in mine for better MPG which averages 18.5MPG and gets 20-22MPG highway. It is rated 15city/20highway with premium!

Not to burst bubble but the LGT only does 243HP and 240ish lb-ft due to HP adjustment sometime after 2005. Wife has the same car(05 LGT 5mt wagon) and loves it.

 

[rjundi]

Originally Posted By: Hokiefyd
Originally Posted By: SubLGT
This V6 puts out 280HP @ 6000rpm and 262lb-ft @ 4700rpm (in the 2016 Pilot). It may be higher in Acura applications, I have not checked. The 2.5L DOHC turbo 4 in my 2005 Subaru puts out 250HP @ 5600rpm and 250lb-ft @3600rpm, and I am somewhat surprised this new Honda V6 does not do better than 280/262. Is 300/300 not doable in a 3.5L n.a. V6 engine?


In the MDX, it is slightly higher...290 hp @ 6,200 and 267 lb*ft @ 4,700. There may be some changes in exhaust or intake tuning, or some separation for marketing reasons. It's competitive with others in its general class:

Chevy Traverse 3.6L V-6: 281/288 hp and 266/270 lb*ft (no speeds given)
Dodge Durango 3.6L V-6: 290 hp @ 6,400 and 260 lb*ft @ 4,800
Ford Explorer 3.5L V-6: 290 hp @ 6,500 and 255 lb*ft @ 4,000
Nissan Pathfinder 3.5L V-6: 260 hp @ 6,400 and 240 lb*ft @ 4,400
Toyota Highlander 3.5L V-6: 270 hp @ 6,200 and 248 lb*ft @ 4,700



Add MPG in AWD form to see what is better or worst package. Honda wants MPG not sure what the rest are doing better or worst then them.

 

[Hokiefyd]

delete

 

[A_Harman]

Yes, higher compression ratios are part of the reason DI is being adopted for gasoline engines. Since the fuel is not drawn into the cylinder with the air, it has less time to absorb heat from the cylinder walls, thereby making it less prone to detonation. Higher compression ratio gives better engine efficiency. GM's Gen V V8's have 11.0 to 11.5 compression ratio naturally aspirated, and the LT4 (supercharged) has 10.0:1. GM's 3.6L V6 has 11.5 CR naturally aspirated, and 10.2 turbocharged. The Ecotec 4's have 11.2 NA and 9.5 turbocharged.

 

[ExMachina]

Originally Posted By: SubLGT
I was looking at the specs for Honda's direct injected "Earth Dreams" 3.5L SOHC V6 engine, and the compression ratio is shown as 11.5:1. Just curious how this compares to other direct injected engines.

11.5 is very typical, unless we are talking about Mazda, who has performed miracles at 14:1 now, and is working on 18:1 for later. See http://www.dailytech.com/Mazda+Expects+3...rticle34052.htm

Originally Posted By: SubLGT
Also, I could not find out what strategy Honda has taken with this engine to avoid the buildup of carbon on the intake valves. Anyone know?

They "just" need to make sure the postive crankcase vent system mixes well with the air, or, better, has an improved catch-can than what was done a few years ago. Also, valve stem surface finishing (shiny) helps keep junk from sticking.

Originally Posted By: SubLGT
This V6 puts out 280HP @ 6000rpm and 262lb-ft @ 4700rpm (in the 2016 Pilot). It may be higher in Acura applications, I have not checked. The 2.5L DOHC turbo 4 in my 2005 Subaru puts out 250HP @ 5600rpm and 250lb-ft @3600rpm, and I am somewhat surprised this new Honda V6 does not do better than 280/262. Is 300/300 not doable in a 3.5L n.a. V6 engine?


Since the GM LFX 3.6L V6 (same 11.5 CR) produces 323 hp (no turbo either), then a 3.5L Honda should be getting 300 hp, no excuses except if tuning for fuel economy (more torque) then 290 hp should be reachable.

 

[gathermewool]

Originally Posted By: Swift101
I don't think DI has anything to do with it. My Sonata 2.0T (DI) has a compression ratio of 9.5:1


Yes, it does

 

[ExMachina]

Originally Posted By: gathermewool
Originally Posted By: Swift101
I don't think DI has anything to do with it. My Sonata 2.0T (DI) has a compression ratio of 9.5:1


Yes, it does


Its the turbo that forces the CR down. No turbo, you can run a much higher CR, with DI helping a lot since DI cools the charge. "The superior charge cooling in DI compared to PFI for the same fuel resulted in pushing knock onset limits to higher in-cylinder maximum pressures."--- from http://papers.sae.org/2012-01-1275/

 

[badtlc]

that is the lowest I have seen. 12+:1 has been what I have seen.

 

[Hokiefyd]

Originally Posted By: ExMachina
Since the GM LFX 3.6L V6 (same 11.5 CR) produces 323 hp (no turbo either), then a 3.5L Honda should be getting 300 hp, no excuses except if tuning for fuel economy (more torque) then 290 hp should be reachable.


Yes; in a car (Acura RLX), the 3.5L V-6 produces 310 hp. GM's 3.6L V-6 in the Traverse (similar to Pilot) produces 281 or 288 hp, so yeah...lots of tuning one way or the other for hp and torque going on here.

 

[gathermewool]

Originally Posted By: ExMachina
Originally Posted By: gathermewool
Originally Posted By: Swift101
I don't think DI has anything to do with it. My Sonata 2.0T (DI) has a compression ratio of 9.5:1


Yes, it does


Its the turbo that forces the CR down. No turbo, you can run a much higher CR, with DI helping a lot since DI cools the charge. "The superior charge cooling in DI compared to PFI for the same fuel resulted in pushing knock onset limits to higher in-cylinder maximum pressures."--- from http://papers.sae.org/2012-01-1275/


Exactly, but I'm not sure if your post was to correct me or as an addition...

Without DI, his 2.0T would not be able to run at 9.5:1 with regular fuel...at his power and emissions levels

 

[440Magnum]

Originally Posted By: racer12306
Chrysler puts out over 300 with their 3.6L in the Ram, iirc.



I think the highest rating for the Pentastar 3.6 in 2015 is in both the Challenger and Ram at 305 HP @6350 RPM 268 ft-lb @4800 RPM. JGC, 200, minivans, Wrangler etc. get ratings between 285 and 300 hp.

But more importantly, it is NOT a direct-injected engine, at least not yet.

DI certainly allows either higher static compression or more boost in theory, but its amazing how much can still be achieved with simpler MPEFI.

 

[SubLGT]

I read somewhere that compared to port injection, DI also enhances low end torque.
Not sure if that is directly due to fuel delivery, or to the higher CR that DI allows, or to both.