What do the intake valve deposits on DI engines actually do, they cannot cause a lean condition because fuel is sprayed in to the cylinder, so asides from wanting a mechanically clean engine what is the actual affect on the engine of having these deposits?
DI engines: ethanol fuel better?
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Worst case scenario is that you have enough build up on the valve that you can loose compression because the valve doesn't seal well.
Most new GDI designs have it where the intake valves are STILL sprayed by the fuel injectors, therefore, minimizing build up.
Mazda Skyactiv engines do this and so does Hyundai. I'm pretty sure VW/Audio and every one else does this these days.
Most new GDI designs have it where the intake valves are STILL sprayed by the fuel injectors, therefore, minimizing build up.
Mazda Skyactiv engines do this and so does Hyundai. I'm pretty sure VW/Audio and every one else does this these days.
I do not see this on the new VW products ( maybe Audi) for their 2.0 litre turbo GTO and GLI, but thanks for the update accent2012!
Originally Posted By: accent2012
Worst case scenario is that you have enough build up on the valve that you can loose compression because the valve doesn't seal well.
Most new GDI designs have it where the intake valves are STILL sprayed by the fuel injectors, therefore, minimizing build up.
Mazda Skyactiv engines do this and so does Hyundai. I'm pretty sure VW/Audio and every one else does this these days.
Mazda does not spray fuel on the intake valves.
Worst case scenario is that you have enough build up on the valve that you can loose compression because the valve doesn't seal well.
Most new GDI designs have it where the intake valves are STILL sprayed by the fuel injectors, therefore, minimizing build up.
Mazda Skyactiv engines do this and so does Hyundai. I'm pretty sure VW/Audio and every one else does this these days.
Mazda does not spray fuel on the intake valves.
Originally Posted By: accent2012
...
Most new GDI designs have it where the intake valves are STILL sprayed by the fuel injectors, therefore, minimizing build up.
...
Most? I thought most do not, and none that you get in a vehicle for under $30,000.
Toyota has dual (direct and port) injection in some of their Lexus GDI engines. Audi plans to add it for model year 2015 if I what I read somewhere else is true.
Mazda uses high valve temperatures to minimize deposits, without port injection.
...
Most new GDI designs have it where the intake valves are STILL sprayed by the fuel injectors, therefore, minimizing build up.
...
Most? I thought most do not, and none that you get in a vehicle for under $30,000.
Toyota has dual (direct and port) injection in some of their Lexus GDI engines. Audi plans to add it for model year 2015 if I what I read somewhere else is true.
Mazda uses high valve temperatures to minimize deposits, without port injection.
Originally Posted By: vintagegz
What do the intake valve deposits on DI engines actually do, they cannot cause a lean condition because fuel is sprayed in to the cylinder, so asides from wanting a mechanically clean engine what is the actual affect on the engine of having these deposits?
Large deposits on the backside of the intake valves would obstruct air flow into the cylinders, decrease volumetric efficiency, and make the engine run rich.
What do the intake valve deposits on DI engines actually do, they cannot cause a lean condition because fuel is sprayed in to the cylinder, so asides from wanting a mechanically clean engine what is the actual affect on the engine of having these deposits?
Large deposits on the backside of the intake valves would obstruct air flow into the cylinders, decrease volumetric efficiency, and make the engine run rich.
I think my Accent GDI is a victim of over-enthusiastic engineering. The car has 11:1 compression and a maximum RPM of 6250 during WOT acceleration. Therefore the cylinder pressures must be rather high especially when you consider the rather high power density of this engine; 138hp and 1.6L displacement.
Of course GDI is supposed to make up for a lot and be tolerant of high cylinder pressures, but it "ain't" working on this one. I figure the dirty gas and my reliance on Top Tier fuel have worked against me. The combustion chambers and piston crowns must have a nice crust of carbon and crud that has a mild glow plug effect along with taking up room in the combustion space effectively increasing the already high compression ratio. I don't know if I can blame Top Tier for being ineffective because the car was apparently pinging since the day it was new, only just enough where it wasn't audible because from day one it never got the fuel economy it is now that I have switched from 87 octane to 93. In any event, I am quite happy and impressed that the car has gone from a max of 37mpg to 42.5mpg now that I'm running premium.
I wonder if buildup on the back of the intake valves could be influencing the ping I was experiencing? The ping began to be audible when the car had about 15k on it. It now has 77k.
Of course GDI is supposed to make up for a lot and be tolerant of high cylinder pressures, but it "ain't" working on this one. I figure the dirty gas and my reliance on Top Tier fuel have worked against me. The combustion chambers and piston crowns must have a nice crust of carbon and crud that has a mild glow plug effect along with taking up room in the combustion space effectively increasing the already high compression ratio. I don't know if I can blame Top Tier for being ineffective because the car was apparently pinging since the day it was new, only just enough where it wasn't audible because from day one it never got the fuel economy it is now that I have switched from 87 octane to 93. In any event, I am quite happy and impressed that the car has gone from a max of 37mpg to 42.5mpg now that I'm running premium.
I wonder if buildup on the back of the intake valves could be influencing the ping I was experiencing? The ping began to be audible when the car had about 15k on it. It now has 77k.
This has been discussed before on BiTOG. Here are some videos of Hyundai GDI engines showing how they operate.
Hyundai Theta https://www.youtube.com/watch?v=Pxvp9F-PS34
hyundai gamma https://www.youtube.com/watch?v=6NDddEZnpOQ
Mazda skyactive g engines are the same way. Air intake valves are low enough to be in the trajectory of the gasoline spray.
It's not just Mazda, but Hyundai and everyone else uses high temperatures. This stuff isn't exclusive to one company.
Look at the injector spray on the intake when intake is open....
Hyundai Theta https://www.youtube.com/watch?v=Pxvp9F-PS34
hyundai gamma https://www.youtube.com/watch?v=6NDddEZnpOQ
Mazda skyactive g engines are the same way. Air intake valves are low enough to be in the trajectory of the gasoline spray.
It's not just Mazda, but Hyundai and everyone else uses high temperatures. This stuff isn't exclusive to one company.
Look at the injector spray on the intake when intake is open....
Originally Posted By: accent2012
This has been discussed before on BiTOG. Here are some videos of Hyundai GDI engines showing how they operate.
Hyundai Theta https://www.youtube.com/watch?v=Pxvp9F-PS34
hyundai gamma https://www.youtube.com/watch?v=6NDddEZnpOQ
Mazda skyactive g engines are the same way. Air intake valves are low enough to be in the trajectory of the gasoline spray.
It's not just Mazda, but Hyundai and everyone else uses high temperatures. This stuff isn't exclusive to one company.
Look at the injector spray on the intake when intake is open....
How about the GM Ecotec engines? Do the valves get "washed," or does GM use the high-temp method?
This has been discussed before on BiTOG. Here are some videos of Hyundai GDI engines showing how they operate.
Hyundai Theta https://www.youtube.com/watch?v=Pxvp9F-PS34
hyundai gamma https://www.youtube.com/watch?v=6NDddEZnpOQ
Mazda skyactive g engines are the same way. Air intake valves are low enough to be in the trajectory of the gasoline spray.
It's not just Mazda, but Hyundai and everyone else uses high temperatures. This stuff isn't exclusive to one company.
Look at the injector spray on the intake when intake is open....
How about the GM Ecotec engines? Do the valves get "washed," or does GM use the high-temp method?
There seem to be two opposing schools of thought here... one says that gasoline wash is needed. Then there is another school which says that injector timing should be designed in a way to completely avoid direct fuel contact...
Quote:
Haider, GM’s V6 assistant chief engineer, explained how GM has designed its DI engines to combat carbon buildup: “We maintain great engine function and performance in our all our DI engines through an optimization strategy with our valve events,” he said. “Our intake-cam timing, injector targeting and timing of the injection events are optimized to avoid direct fuel contact on the intake valves. This strategy keeps smoke and soot formation to an absolute minimum, which in turn prevents excessive deposit formation.”
http://www.edmunds.com/autoobserver-archive/2011/06/direct-injection-fouls-some-early-adopters.html
Quote:
Haider, GM’s V6 assistant chief engineer, explained how GM has designed its DI engines to combat carbon buildup: “We maintain great engine function and performance in our all our DI engines through an optimization strategy with our valve events,” he said. “Our intake-cam timing, injector targeting and timing of the injection events are optimized to avoid direct fuel contact on the intake valves. This strategy keeps smoke and soot formation to an absolute minimum, which in turn prevents excessive deposit formation.”
http://www.edmunds.com/autoobserver-archive/2011/06/direct-injection-fouls-some-early-adopters.html
WOW! Really valuable info there. I didn't realize the spray angle was such that it could spray onto the back of the valve that way. Thanks for the link.
What fuel are you running in your 2012 Accent? What is the max fuel economy you've seen? I have the 2012 Accent as well. On the premium fuel I've seen 42.5 MPG, the best ever, and that is actual calculated. The MPG computer lies to the tune of 2 extra MPG, so I actually saw 44.5 MPG on the computer. Before, with 87 octane, the best it would do was 37 MPG.
What fuel are you running in your 2012 Accent? What is the max fuel economy you've seen? I have the 2012 Accent as well. On the premium fuel I've seen 42.5 MPG, the best ever, and that is actual calculated. The MPG computer lies to the tune of 2 extra MPG, so I actually saw 44.5 MPG on the computer. Before, with 87 octane, the best it would do was 37 MPG.
Thanks for that link! The more info readily available the better!
As for my accent, I average 34mpg, but that's mixed city/highway driving and my car has 54k miles.
The best hand-calculated average I've gotten with this car was 38mpg. The onboard MPG is always off a bit and it varies from what I've read - I don't rely on it anymore. I know I got the most if I average 280 miles with one/two bars left on the fuel gauge.
I hope you bought your car brand new before the Hyundai MPG rewards kicked in. I received $130+ this past year and nearly $200 the year before. Not a bad Xmas present
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I've used 89 octane once and didn't notice any improvement. I might try 93 octane, but I don't know, it's expensive! It might not be worth it in the long run to gain 2-4mpg.
As for my accent, I average 34mpg, but that's mixed city/highway driving and my car has 54k miles.
The best hand-calculated average I've gotten with this car was 38mpg. The onboard MPG is always off a bit and it varies from what I've read - I don't rely on it anymore. I know I got the most if I average 280 miles with one/two bars left on the fuel gauge.
I hope you bought your car brand new before the Hyundai MPG rewards kicked in. I received $130+ this past year and nearly $200 the year before. Not a bad Xmas present
I've used 89 octane once and didn't notice any improvement. I might try 93 octane, but I don't know, it's expensive! It might not be worth it in the long run to gain 2-4mpg.
I got one of the first '12 Accents in the country. Bought it June 2011. I'm part of the MPG reimbursement, but I haven't cashed it in yet. I'm up around $500 right now.
Do yourself a favor and do the math. If you can only improve your mileage 1-2 MPG, then you'll save money running premium. I'm saving a lot. I've improved 5+ MPG. If you hear pinging quite a lot, then your likely to benefit too. But maybe your car is more tolerant to 87 octane. Its supposed to be according to the owner's manual, but mine is not!
Do yourself a favor and do the math. If you can only improve your mileage 1-2 MPG, then you'll save money running premium. I'm saving a lot. I've improved 5+ MPG. If you hear pinging quite a lot, then your likely to benefit too. But maybe your car is more tolerant to 87 octane. Its supposed to be according to the owner's manual, but mine is not!
Originally Posted By: Lurgi
WOW! Really valuable info there. I didn't realize the spray angle was such that it could spray onto the back of the valve that way. Thanks for the link.
What fuel are you running in your 2012 Accent? What is the max fuel economy you've seen? I have the 2012 Accent as well. On the premium fuel I've seen 42.5 MPG, the best ever, and that is actual calculated. The MPG computer lies to the tune of 2 extra MPG, so I actually saw 44.5 MPG on the computer. Before, with 87 octane, the best it would do was 37 MPG.
My skyactiv mazda3 behaves similar, but not as extreme as yours. I saw around 39 MPGs on 87 octane and regularly hit 42-44 MPGs on 91+ octane.
WOW! Really valuable info there. I didn't realize the spray angle was such that it could spray onto the back of the valve that way. Thanks for the link.
What fuel are you running in your 2012 Accent? What is the max fuel economy you've seen? I have the 2012 Accent as well. On the premium fuel I've seen 42.5 MPG, the best ever, and that is actual calculated. The MPG computer lies to the tune of 2 extra MPG, so I actually saw 44.5 MPG on the computer. Before, with 87 octane, the best it would do was 37 MPG.
My skyactiv mazda3 behaves similar, but not as extreme as yours. I saw around 39 MPGs on 87 octane and regularly hit 42-44 MPGs on 91+ octane.
Any high compression DI engine should benefit from higher octane - regardless of the system. I am trying to get my parents to run 91 in their Focuscape just to show them the better mileage.
Originally Posted By: Lurgi
I give my GDI Accent regular Italian tune-ups. They don't seem to "blow out" or "clean out" anything. The [censored] thing continued to ping no matter what. I religiously ran only top tier gas since it was new. I used 87 octane only as well, since the owner's manual states that is OK. Finally, since the pinging was slowly worsening, I decided to try premium fuel only. The ping has almost completely stopped. And the fuel economy has picked up over 5 MPG! on the highway. Using premium is actually quite a bit cheaper with this sort of improvement in economy. And the engine isn't beating itself to death. I would say when it was pinging bad on 87 octane, the knock sensor influenced the computer to take out timing, and I noticed downshifting, apparently to stop the pinging.
Is your car knocking or is it pinging? Are you running premium fuel currently?
The only worry I have is that eventually my car will have carbon build up so bad that it won't even operate on premium any more.
It may not be that. My 2001 Taurus pinged horribly, for years. Dropped a lot of money on it - always thought it was carboned up.
It was just a bad EGR sensor. Finally set a code at 70K miles (had problems from 30K), replaced the DFPE sensor and it never pinged again!
Originally Posted By: Lurgi
I give my GDI Accent regular Italian tune-ups. They don't seem to "blow out" or "clean out" anything. The [censored] thing continued to ping no matter what. I religiously ran only top tier gas since it was new. I used 87 octane only as well, since the owner's manual states that is OK. Finally, since the pinging was slowly worsening, I decided to try premium fuel only. The ping has almost completely stopped. And the fuel economy has picked up over 5 MPG! on the highway. Using premium is actually quite a bit cheaper with this sort of improvement in economy. And the engine isn't beating itself to death. I would say when it was pinging bad on 87 octane, the knock sensor influenced the computer to take out timing, and I noticed downshifting, apparently to stop the pinging.
Is your car knocking or is it pinging? Are you running premium fuel currently?
The only worry I have is that eventually my car will have carbon build up so bad that it won't even operate on premium any more.
It may not be that. My 2001 Taurus pinged horribly, for years. Dropped a lot of money on it - always thought it was carboned up.
It was just a bad EGR sensor. Finally set a code at 70K miles (had problems from 30K), replaced the DFPE sensor and it never pinged again!
Originally Posted By: Miller88
Any high compression DI engine should benefit from higher octane - regardless of the system. I am trying to get my parents to run 91 in their Focuscape just to show them the better mileage. . . .
I doubt mine is that high a compression engine. The manual says 87. However, the Turbo models have "recommended 91+ octane," and the sporty GS cars require premium.
Though those cars have the 2.0L turbo, it might be worth a try. Though I tried premium once in the 3800-powered Park Avenue. My gas mileage went down.
Any high compression DI engine should benefit from higher octane - regardless of the system. I am trying to get my parents to run 91 in their Focuscape just to show them the better mileage. . . .
I doubt mine is that high a compression engine. The manual says 87. However, the Turbo models have "recommended 91+ octane," and the sporty GS cars require premium.
Though those cars have the 2.0L turbo, it might be worth a try. Though I tried premium once in the 3800-powered Park Avenue. My gas mileage went down.
The Mazda is 13:1 and it recommends 87 too. I think the Mazdas are the only ones with the extreme compression.
Originally Posted By: Benzadmiral
I doubt mine is that high a compression engine. The manual says 87. However, the Turbo models have "recommended 91+ octane," and the sporty GS cars require premium.
Your engine has an 11.2:1 compression ratio. In my book, that's pretty high. I remember back in the late 60s when all the Big Blocks came with 10:1 ratios and required premium gas and then in 71-72 the ratio was dropped to 8:1 so they could run on regular and the upcoming "low lead" which eventually became "unleaded" in 1975 with the first cats on cars.
Thanks to FI and ECM, modern engines can run on 87 with that high a compression ratio. But it might be worth running a few tanks of 93 octane just to see if there is any difference in MPG.
I doubt mine is that high a compression engine. The manual says 87. However, the Turbo models have "recommended 91+ octane," and the sporty GS cars require premium.
Your engine has an 11.2:1 compression ratio. In my book, that's pretty high. I remember back in the late 60s when all the Big Blocks came with 10:1 ratios and required premium gas and then in 71-72 the ratio was dropped to 8:1 so they could run on regular and the upcoming "low lead" which eventually became "unleaded" in 1975 with the first cats on cars.
Thanks to FI and ECM, modern engines can run on 87 with that high a compression ratio. But it might be worth running a few tanks of 93 octane just to see if there is any difference in MPG.
Hm! I hadn't thought to look that up. Well, premium tends to be about .30-.40 more per gallon than regular around here, around 11% higher. I'd have to get at least 26 mpg in regular driving to break even -- more, if the 25 I got this past period wasn't a fluke.
Might be fun to try on the highway, though.
Might be fun to try on the highway, though.
Originally Posted By: Miller88
The Mazda is 13:1 and it recommends 87 too. I think the Mazdas are the only ones with the extreme compression.
That is extreme and definitely explains the "high temp heat to prevent build up" theory. I guess I will give 93 octane a shot... heck even fill up at a shell station, they are supposed to have the best high octane gasoline. BP gas is what I mainly use since that is now considered top tier but I guess I'll spoil myself
.
The Mazda is 13:1 and it recommends 87 too. I think the Mazdas are the only ones with the extreme compression.
That is extreme and definitely explains the "high temp heat to prevent build up" theory. I guess I will give 93 octane a shot... heck even fill up at a shell station, they are supposed to have the best high octane gasoline. BP gas is what I mainly use since that is now considered top tier but I guess I'll spoil myself
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