Let's talk diesels!!!!

[blackshine007]

Ok, call me an idiot or exploit my ignorance, but if you have a diesel and you're upgrading the turbos, why would anyone in their right minds drop the compression to 10:1? I would really like to understand that concept. Thanks in advance.

[allmotoronly]

I have no clue. Diesels run on compression. they do not have spark plugs, and they rely on high compression to cause detonation. will a diesel even idle with 10.0:1 C/R?

[japan4racing]

i thought low comression for a diesel was like 14-15:1.......will the diesel even combust with compression that low? i wonder if they up the fuel pressure more to atomize it better.....diesels also run super high fuel pressure..i guess if you ran more it would make for a better chance of igniting but it does seem kinda stupid to run 10:1....im not a diesel expert though.

[blackshine007]

Well according to the guy rattling off specs about someone else's diesel truck (he's a member in here) He said that it was a twin turbo set up on 10:1 compression. I asked the same exact question. It crunk up with no problem being that it was warm already. I would assume it wouldn't do shit at that low. So let's just call the guy "Genious" for a moment. The guy in the diesel truck was doing some crazy ass drifting in the parking lot. I thought the thing was gonna flip from hitting the curb and/or take out the light poll a couple of times. I asked "Genious" what was done to it. He was like "The guy said it has a twin turbo set up on 10:1 compression....."
me: WOW!!! That's low!!!
Genious: What do you mean low?
me: Umm, why would you wanna lower the compression that low on a diesel?
Genious: (giving me a look like I'm a dumbass) To get more air into it!!! (giving me the duh look and walks away)

So I guess I'm missing something on why would an outrageously powerful diesel have lower compression in it. I would assume by the characteristics of the engine, it should've never been touched

[blackshine007]

Anyone else care to touch this one? I need some real opinions

[Z28]

Well according to the guy rattling off specs about someone else's diesel truck (he's a member in here) He said that it was a twin turbo set up on 10:1 compression. I asked the same exact question. It crunk up with no problem being that it was warm already. I would assume it wouldn't do shit at that low. So let's just call the guy "Genious" for a moment. The guy in the diesel truck was doing some crazy ass drifting in the parking lot. I thought the thing was gonna flip from hitting the curb and/or take out the light poll a couple of times. I asked "Genious" what was done to it. He was like "The guy said it has a twin turbo set up on 10:1 compression....."
me: WOW!!! That's low!!!
Genious: What do you mean low?
me: Umm, why would you wanna lower the compression that low on a diesel?
Genious: (giving me a look like I'm a dumbass) To get more air into it!!! (giving me the duh look and walks away)

So I guess I'm missing something on why would an outrageously powerful diesel have lower compression in it. I would assume by the characteristics of the engine, it should've never been touched


If I understand you right, I think it's because the newer technology, such as common rail and AECS factored with the ability to increase the incoming air temperature to about 700-900 degrees without the use of a higher compression ratio, diesels are able to drop their C.R. Dropping the C.R. for them would help in effiency, and would also allow them to burn a lighter fluid, such as methenol or propane.

Basically, from my weak understanding, they drop the C.R. so that they can modify other aspects of the system due to the technology replacing glow plugs and getting rid of the need for a higher C.R. to cure the cold-start woes some diesels have had. But like I said, mostly due to the newer technology allowing them to drop C.R. via heating the air temperature another way and using a higher pressure fuel system.

But I don't know diesels for shit, so take what I said with a grain of salt, but hopefully I'm not too far off. Kinda rare to find diesel mechanics these days, but I hope someone corrects me where I'm wrong.

[blackshine007]

The sole point of a diesel is to run on oil. That's why the compression is normally high. It takes alot of compression to ignite diesel. Notice if you see someone accidentally fill their tanks with diesel, what happens? Doesn't run to save it's life, right? The glow plugs initially is just a hot spot in the CC that ignites the fire. After that, it runs off it's own detonation. Fuel the fire and it increases it's idle. With the direct injection, it justs make it easier to control fuel to get better mileage and aids in the benefit of better tailpipe emissions. I would so love to hear someone's opinion on that. Reps for all those that has chimed in on this

[Blitanicle99]

Chiming in... My best friend has probably the fastest Diesel in the Marietta/Kennesaw Area. If someone thinks they have a faster one PM me and well see haha

But in a nut shell (Ill try and keep this simple and short)
All diesels do not have crazy fuel pressure. The new motors such as the 24v Common Rail found in the new Dodges and 6.0 Fords and new Duramaxx. The older dodge motors the regular 24 and 12v do not have that kind of fuel pressure. Where as, the common rail the sheer amount of pressure in the lines can cut your skin when your change out the injectors.
But... running that low compression on a twin turbo setup will allow a shit ton of air in and not use alot of fuel. The guys running twins arent running normal setups. Most run sequential (sp?) Using their stock probably a t44 to spool up something like a t70+. That big turbo needs a SHIT LOAD of air obviously so the amount of air pressure you have to increase is off the charts.
The guy may not have been running something that low, but he probably dropped it lower. 10.1 is on the verge of stalling for a diesel. Diesels run of compression, no compression motor shuts off.
Simple enough?

[blackshine007]

In a nutshell, yes. Thanks. Have some reps

[NevrNufTorq]

just my :2cents: i called a few buddies that are diesel mechanics and they said there's no way this puppy would run at 10 to 1. and you can cram all the boost in a diesel that you want it wont make it much faster. the only wy to make one faster is to cram more fuel in. but there is a theoretical limit to this before you have to raise the boost!!! and the reason why propane and methanol work so well in diesel's is b/c they replace the air and allow the diesel to burn hotter and thats why you have to watch your egt's except for the meth which will lower your egt's but does allow the charge to run cooler. :goodjob:

oh, tell your boy to bring his truck out to tunerfest. i'llrun him in the dodge for $hits and giggles after i unload the 2 cars i haul there off the trailer!! not saying i'll win or lose but it'll hold its own :D :eek:

[blackshine007]

just my :2cents: i called a few buddies that are diesel mechanics and they said there's no way this puppy would run at 10 to 1. and you can cram all the boost in a diesel that you want it wont make it much faster. the only wy to make one faster is to cram more fuel in. but there is a theoretical limit to this before you have to raise the boost!!! and the reason why propane and methanol work so well in diesel's is b/c they replace the air and allow the diesel to burn hotter and thats why you have to watch your egt's except for the meth which will lower your egt's but does allow the charge to run cooler. :goodjob:

oh, tell your boy to bring his truck out to tunerfest. i'llrun him in the dodge for $hits and giggles after i unload the 2 cars i haul there off the trailer!! not saying i'll win or lose but it'll hold its own :D :eek:
I like that answer. Thanks. Have some rep kind sir

[1SOL2NV]

kick him in the nuts and run ..... lol ......

[racer181818]

ummm yeah it wouldnt even run.... how dumb